The fertilisation of flowers. Translated and edited by D'Arcy W. Thompson, with a preface by Charles Darwin

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THE FERTILISATION OF FLOWERS

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THE

FERTILISATION OF FLOWERS

BY

PROF. HERMANN MULLER

TRANSLATED AND EDITED BY

D’ARCY W. THOMPSON, BA.

SCHOLAR OF TRINITY COLLEGE, CAMBRIDGE

WITH A PREFACE BY

CHARLES DARWIN

WITH ILLUSTRATIONS

FL ondon
MACMILLAN AND CO.
1883

TRANSLATOR’S PREFACE.

In this edition I have incorporated a large mass of Dr. Hermann Miiller’s recent
observations, of which he sent me full notes; and I have also added further details
where it seemed necessary, taken from his own and other writings. Many new figures
from Dr. Hermann Miiller’s other works have also been inserted here.

The systematic part of the book, which is arranged on Endlicher’s system in the
German edition, has been re-arranged according to Bentham and Hooker's Genera
Plantarum.

I may mention one case out of many in which I have had difficulty in choosing
between equivalent words. I have throughout used fertilisation in preference to the
ungainly word pollination, to imply application of pollen to the stigma without
definite reference to the result of the act: that is to say, I have in ordinary cases
translated Bestdéubung and Befruchtung by the same word. But I have taken pains to
guard against ambiguity in all cases where this rendering might lead to it.

_ Mr. T. H. Corry, of Caius College, Assistant-Curator of the University Herbarium,
has read through the whole systematic part, giving me constant assistance.

I have been at pains to compile a list of all works relating to the subject of this
book ; and so far as lay in my power I have added an Index of genera to the list.

Charles Darwin’s preface, full of suggestion, full of kindly appreciative feeling, is
of peculiar interest as one of the very last of his writings.

D’ARCY W, THOMPSON.
Trinity CoLttear, April, 1883.

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PREFATORY NOTICE.

THE publication of a translation of Hermann Miiller’s Die
Befruchtung der Blumen, &c., will without doubt be a great
service to every English botanist or entomologist who is interested
in general biological problems. The book contains an enormous
mass of original observations on the fertilisation of flowers, and
on the part which insects play in the work, given with much
clearness and illustrated by many excellent woodcuts. It includes
references to everything which has been written on the subject;
and in this respect the English edition will greatly exceed in
value even the original German edition of 1873, as Miiller has
completed the references up to the present time. No one else could
have done the latter work so well, as he has kept a full account
of all additions to our knowledge on this subject. Any young
observer who, after reading the whole or part of the present work,
will look, for instance, at the flower of a Salvia, or of some
Papilionaceous or Fumariaceous plant, or at one of our common
Orchids, will be delighted at the perfection of the adaptations
by which insects are forced, unconsciously on their part, to carry
pollen from the stamens of one plant to the stigma of another.
Design in nature has for a long time deeply interested many men,
and though the subject must now be looked at from a somewhat
different point of view to what was formerly the case, it is not
thus rendered the less interesting.

viii PREFATORY NOTICE.

Hermann Miiller has by no means confined his attention to the
manner in which pollen is carried by insects or other animals
from plant to plant, for wind-fertilised flowers have been carefully
described by him; and several curious transitions from the one
state to the other are noticed. He has also attended more closely
than any one else to the many contrivances for self-fertilisation,
which sometimes co-exist with adaptations for cross-fertilisation.
For instance, he has discovered the singular fact that with certain
species two kinds of plants are regularly produced, one bearing
inconspicuous flowers fitted for self-fertilisation, and the other kind
with much more conspicuous flowers fitted for cross-fertilisation.
The flowers on the first-mentioned plants serve the same end as
the curious little closed cleistogamic flowers which are borne by a
considerable number of plants, as described and enumerated in the
present work.

There is another interesting feature in the Befruchtung, by

which it differs from all other works on the same subject; for it
includes not only an account of the adaptation of flowers to insects,
but of different insects to differently constructed flowers for the
sake of obtaining their nectar and pollen.

Any one who will carefully study the present work and then
observe for himself, will be sure to make some interesting dis-
coveries; and as the references to all that has been observed are
so complete, he will be saved the disappointment of finding that
which he thought was new was an already well-known fact. I
may perhaps be permitted here to mention a few points which
seem to me worthy of further investigation. There are many
inconspicuous flowers which during the day are rarely or never visited
by insects, and the natural inference seems to be that they must
be invariably self-fertilised ; for instance, this is the case with some
species of Trifolium and Fumaria which bear very small flowers,
with some species of Galium, Linum catharticum, &. Many other
such flowers are enumerated by Miiller. Now it is highly desirable
_that it should be ascertained whether or not these flowers are

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PREFATORY NOTICE. ix

visited at night by any of the innumerable individuals of the many
species of minute moths. <A lepidopterist while collecting at
night, if endowed with only a small portion of the indomitable
patience displayed by Miiller, could ascertain this fact. The
question possesses a considerable degree of theoretical interest ;
for if these inconspicuous flowers are never visited by insects, why,
it may be asked, do they expand, and why is not the pollen
protected by the petals remaining closed, as in the case of
cleistogamic flowers? It would perhaps be possible to smear
such small flowers with some viscid matter, and an examination
of the petals would probably reveal nocturnal visits by moths by
the presence of their scales; but it would be necessary to prove
that the matter employed was not in itself attractive to insects.
H. Miiller gives long lists of the several kinds of insects which he
has seen visiting various flowers in Germany; and it would be
interesting to learn whether the same insects and the same pro-
portional number of insects belonging to the different orders, visit
the same plants in England as in Germany.

There are many other subjects which it is desirable that some
one should investigate, for instance, by what steps heterostylism
(of which an account will be found in the present work) originated :
and with trimorphic heterostyled plants we meet with a more
extraordinary and complicated arrangement of the reproductive
system than can be found in any other organic beings. In order
to investigate this subject and several others, experiments in
fertilisation would have to be ‘tried; but these are not difficult
and would soon be found interesting. For instance, there are
some plants, the pistils and stamens of which vary much in length,
and we may suspect that we here have the first step towards
heterostylism ; but to make this out, it would be necessary to test
in many ways the power of the pollen and of the stigma in the
several varieties. There exist also some few plants the flowers of
which include two sets of stamens, differing in the shape of the
anthers and in the colour of the pollen; and at present no one

x PREFATORY NOTICE.

knows whether this difference has any functional signification, and
this is a point which ought to be determined. Again, there are
other plants, for instance, the common Rhododendron, in which the
shorter stamens are more or less rudimentary, and it has been
asserted that seedlings raised from pollen taken from the short and
from the full-sized stamens differ in appearance; and it would be
of importance to know whether they differ in their fertility or
power of yielding seeds. It would also be interesting to learn
whether in the plants, already alluded to, which produce two
forms, one adapted for self-fertilisation and the other for cross-
fertilisation, the reproductive organs have become in any degree
differentiated, so that their action would not be perfect if the two
forms were reciprocally crossed. Would a flower adapted for
self-fertilisation yield a full complement of seed if fertilised by
pollen from one adapted for cross-fertilisation ; and vice-versd with
the other form ?

But it would be superfluous to make any further suggestions,
These will occur in abundance to any young and ardent observer
who will study Miiller’s work and then observe for himself,
giving full play to his imagination, but rigidly checking it by
testing each notion experimentally. If he will act in this manner,
he will, if I may judge by my own experience, receive so much
pleasure from his work, that he will ever afterwards feel grateful
to the author and translator of the Befruchtung der Blumen.

CHARLES DARWIN.

Down, February 6, 1882.

CONTENTS.

HISTORICAL INTRODUCTION .........

PART II.

THE INSECTS WHICH VISIT FLOWERS... .

PART III.

THE MECHANISMS OF FLOWERS .......

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68

ERRATA,

Page 34, line 9, from top, delete the words ‘‘ of. Umbellifers.”
» 48, Fig. 8, for ‘‘ Licus,” read ‘‘ Sicus.”
» 55, line 7 from top, for ie feathery hairs,” read ‘stiff bristles.”
>> 149, ,, 26, ,, 5, for **wreus,” read “wrens.”
5 ALG; horse Gy ae TOP “¢ Bsculus Pavia (rubicunda),” read ‘* Aisculus
(Pavia) rubicunda.”
», 171, in both tables, transpose the words, ‘In Low Germany,” and ‘* On the
Alps.”
», 427, line a6, from top, for < Scopolia,” " read ‘‘Scopolina.”
», 487, 5, 2, 5, 55 for ‘ Digitalitis,” read ‘‘ Digitalis.”

Labelle is, perhaps, a better name for the lobesat the extremity of the proboscis
in Diptera, called end-flaps (German Endklappen) or paraglosse in Part II.

THE FERTILISATION OF FLOWERS.

PART I.
HISTORICAL INTRODUCTION.

{tr was not until the close of last century that the true purport
and significance of flowers began to be perceived. Christian
Conrad Sprengel seems to have been the first to view the subject
in the light of adaptation, and to show how all’ the colours, scents,
and singular forms of flowers. have some useful purpose. His
book struck out a new path in botanical science, and its title, Zhe
Secret of Nature in the Form and Fertilisation of Flowers Discovered,
shows that the author was well aware of the importance of his
discoveries. Setting out with the conception of a “wise author of
nature who has not created one hair without a definite purpose,’
Sprengel contrived, by reflecting on apparently insignificant facts,
to throw light on most important phenomena in the life of
flowers. The gradual progress of his discovery, as he describes it
in the introduction to his book, is worth recapitulating.

The inconspicuous hairs which cover the lower part of the petals
of the wood cranesbill (Geranium silvaticum, L.), and. beneath which
drops of honey lie hid, led Sprengel in the year 1787 to the dis-
covery that most flowers which contain nectar are so arranged that,
while insects can easily reach it, the rain is prevented from doing
so; and he came to the conclusion ‘“‘ that the nectar of these flowers
is secreted for the sake of insects, and is protected from rain in
order that the insects may get it pure and unspoiled.” Starting
from this conception, he next summer studied the forget-me-not.

1 Das enideckie Geheimniss der Natur im Baue und in der Befruchtung der Blumen
(Berlin : 1793).
fs / B
al

2 THE FERTILISATION OF FLOWERS. [PART I.

(Myosotis palustris, L.), and speculated on the meaning of the yellow
ring round the mouth of the corolla, which forms a pleasing con-
trast to the azure-blue of the limb; and he conceived the idea
that this might serve to guide insects on their way to the honey.
On examination of other flowers he found that coloured dots and
lines and other figures occur especially at the entrance to the
nectaries, or point towards it, and he was accordingly confirmed in
this idea of path-finders or honey-guides. The next step was easy,
and Sprengel could scarcely remain long without perceiving that, as
the special colour of one part of the corolla serves to guide the
insect after it has settled upon the flower, the bright colour of the —
whole flower serves to attract the notice of insects while still at a
distance. So far, Sprengel had looked upon flowers as contrived
simply for the use of insects, but the study of some species of
iris, in the summer of 1789, led him to the further discovery that
many flowers are absolutely incapable of being fertilised without
the aid of insects; and so he concluded that the secretion of honey
in flowers, its protection against rain, and the bright colours of the
corolla are contrivances of use to the flower itself by bringing
about its fertilisation by insects. Thus were laid the foundations
of a theory of honey-containing flowers, which Sprengel enunciates
in the following propositions : (1) These flowers are fertilised by
some one species of insect, or by several species ; (2) the insects,
in approaching the honey, brush pollen from the anthers with
various hairy parts of their bodies and convey it to the stigma. The
application of this theory to the various plants that came within
Sprengel’s reach led to the production of the above-mentioned
book, which is marked throughout by a wealth of patient observa-
tion and acute reasoning. In it the following five features are |
described in several hundred species of flowers, partly native and
partly cultivated, as proof of the correctness of the theory :—

(1) A honey-gland or nectary, i.e. a part which elaborates and
secretes honey; (2) a honey-receptacle, which receives and stores
the honey secreted by the gland; (3) a contrivance to shelter
the honey from rain (Saftdecke); (4) contrivances to enable the
insect to find the honey easily (Sa/tmal); bright colour and ex-
tension of the corolla, odour, and above all coloured spots near
the entrance to the honey-receptacles (path-finders); (5) the
‘impossibility of mechanical fertilisation, 7.e. spontaneous self-fer-
tilisation, or of fertilisation by the wind, and in many cases the
direct observation of fertilisation by insects in nature. Sprengel
discussed these five points in numerous honey-secreting flowers,

ed!” |

PART I. | HISTORICAL INTRODUCTION. 3

and succeeded in explaining most of their characters as contrivances
for insect-fertilisation. His theory, although the first effort in this
wide field, would have afforded a satisfactory key to the chief
puzzles of the floral world had it not contained a very serious flaw,
which Sprengel was not conscious of, and was therefore not in a
position to remove. Since the conveyance of pollen to the stigma
is obviously of no benefit to the insect, the same question should
have arisen even from Sprengel’s teleological standpoint, which
nowadays comes up prominently when we consider his hypothesis
from the standpoint of natural selection: “What advantage can it
be to the plant that its pollen should be conveyed by insects to
the stigma?”’ For just as according to our modern views only
modifications which are of advantage to their possessor can be pre-
served by natural selection, so from the teleological standpoint
only beneficial arrangements could be ascribed to the all-wise
Creator. If the conveyance of pollen to the stigma by insects is
of no greater advantage than the direct contact of the reproductive
organs in the flower, then the preference of the former uncertain
method to the latter seems unnecessary and capricious, and any
theory based thereon falls to the ground.

It is remarkable in how many cases Sprengel recognised that
the pollen is carried of necessity to the stigmas of other flowers by
the insect-visitors, without suspecting that therein lies the value of
insect-visits to the plant. In very many plants Sprengel had
observed that the two sets of sexual organs in the same flower are
not developed simultaneously; to this phenomenon he gave the
name dichogamy. In his introduction (p. 43) he says expressly:
“Since very many flowers are of one sex only, and probably as
many more are dichogamous, nature seems to intend that no flower
shall be fertilised by means of its own pollen,” and as a proof of
this he adduces an experiment performed by him on Hemerocallis
Julva, which showed him that this plant is not fertile to its own
pollen. So near was Sprengel to the distinct recognition of the
fact that self-fertilisation leads to worse results than cross-fertilisa-
tion, and that all the arrangements which favour insect-visits are

_of value to the plant itself, simply because the insect-visitors effect

cross-fertilisation !

But this omission was for several generations fatal to Sprengel’s
work, which was otherwise well fitted to give a powerful impulse
to further research. For, both at the time and subsequently,
botanists felt above all the weakness of his theory, and they set

aside along with his defective ideas the rich store of his patient
B 2

+t THE FERTILISATION OF FLOWERS. [PART I.

and acute observations and his pai poe and accurate
interpretations.

Instead of the correlation of living organisms, which Sprengel
had made the subject of observation and reflection with such
admirable results, classification and afterwards anatomy and
embryology occupied investigators so exclusively that no one ever
thought of continuing Sprengel’s beautiful. researches or of
testing their accuracy. His work remained forgotten until our
ideas of organic nature were fundamentally changed by the progress
of knowledge, and until the advantages of cross-fertilisation, which
Sprengel only faintly realised, were recognised anew and more
clearly through independent experiments.

The idea of independent creation of species, prevalent in
Sprengel’s time and so confidently stated in his book, was overthrown
by progress in the three departments of classification, embryology,
and paleontology ; all three led consistently to the conception that
the existing species of plants and animals must have originated
from simpler forms; and Darwin’s Origin of Species proved the
point by deiopaention clearly and thoroughly how actual forces
were operating before our eyes to modify living forms.

But, even before this great revolution in our conception of
nature, one point which was needed to make Sprengel’s theory
efficient had been clearly perceived. A few years after Sprengel’s
book appeared, Andrew Knight (392), after some experiments on
cross-fertilisation and self-fertilisation in the pea, laid down the
law that in no plant does self-fertilisation occur for an unlimited
number of generations. But his law received no further atten-
tion, and nobody conceived the idea of applying it in connection

with Sprengel’s theory. A like fate overtook Herbert (334), who

summed up the result of his numerous experiments in this sentence :
“T am inclined to think that I have derived advantage from impreg-
nating the flower from which I wished to obtain seed with pollen
from another individual of the same variety, or at least from
another flower, rather than with its own” (p. 371). OC. F. Gartner
(259) was led still more distinctly to the same result by experiments
on Passiflora, Lobelia, and Fuchsia. Even when Darwin, in 1857
and 1858, published some new experiments on Papilionaceee (151),
which showed that the aid of insects or artificial imitation of their
action was necessary for complete fertility, and that crossing of
separate plants was actually to a great extent effected by insects, his
re-enunciation of Knight’s law remained ineffectual. The charm
that had kept Sprengel’s theories inoperative was only broken when,

PART 1. ] HISTORICAL INTRODUCTION. - B.

in the next year, Darwin produced his Origin of Species, and in it
emphasised Knight’s law as a general law of nature, placing it on
broader and surer foundations and uniting it intimately with his
theory of natural selection. This theory showed for the first time
the full value of Sprengel’s work, and caused his book, which had
been forgotten for seventy years, to play a prominent part in the
investigation of the prime causes which determine the forms of
flowers.

As a foundation for the hypothetic natural law that “no organic
being fertilises itself for a perpetuity of generations, but that a
cross with another individual is occasionally—perhaps at very long
intervals—indispensable,’” 1 Darwin showed that in all higher and
the great majority of lower animals the sexes are separate, and
that most hermaphrodite forms pair regularly ; that, in the experi-
ence of breeders of animals and cultivators of plants, breeding
in-and-in diminishes the strength and the productiveness of the
offspring, while crossing with another breed, or with another stock
of the same breed, increases both ; that, according to the above-
mentioned experiments of several botanists, the application of
pollen to the pistil of the same flower is less efficient than pollen
from another individual; that in very many plants the situation of
the reproductive organs, exposed to the weather and often liable to
injury, may be most simply explained if we admit the necessity of
occasional crossing; that, according to his own experiments on
Papilionacee, the exclusion of insect-visits in many cases diminishes
or arrests productiveness; that, as Sprengel had shown in many
cases and Darwin had confirmed, self-fertilisation is prevented in
many flowers by the relative positions of the reproductive organs
or by their ripening at different times; finally, that in no living
organism do the structure or situation of the reproductive organs
prevent occasional crossing with another individual of the same
species. These statements, taken separately, were neither decisive
nor free from objection, but collectively they lent a high degree of
probability to Darwin's hypothesis; and so, from its close connec-
tion with the question of the origin of species and the fundamental
importance that it therefore had for all botanical research, botanists
could not help at once taking part for or against it, according to
whether they were impelled by the general weight of evidence or
deterred by the gaps in the chain.

The opposers justly maintained that though in the animal
kingdom the possibility of occasional pairing might be admitted in

1 Origin of Species, chap. iv. ‘On the Interciossing of Individuals.”’

6 THE FERTILISATION OF FLOWERS. [PART I.

the case of the relatively few hermaphrodites which generally
fertilise themselves, yet for the majority the common notion that
the flowers are fertilised with their own pollen, either spontaneously
or by the aid of insects or the wind, was as yet not disproved (cf.
Treviranus, 742). They said justly that the observations quoted to
prove the disadvantages of breeding in-and-in or of fertilising a
flower with its own pollen were quite insufficient, and they called
for more extended experiments. Finally, they pointed to the not
rare occurrence of flowers which inevitably fertilise themselves,
which even remain closed, and yet which are fully productive, as a
difficulty in the way of Darwin’s hypothesis not yet removed. From
the nature of the case, complete proof seems impossible, either for or
against this law; for neither, if it is true, can the necessity of
occasional crossing be shown for all bi-sexual plants and animals;
nor, if it is false, can any hermaphrodite which as a rule fertilises
itself be kept under observation for an unlimited number of
generations. But, since the facts which come within the scope of
this law and by which its validity may be subjected to detailed
proof are inexhaustibly numerous, continued research will either
bring the probability of the law to the verge of certainty or make
its improbability continually more conspicuous. And so the
Knight-Darwin law was admirably fitted to lead to numerous
investigations of phenomena hitherto left unobserved, and so to be
highly valuable in furthering our knowledge, even if in the end its
truth could not be universally and absolutely affirmed.

Darwin opened these new lines of investigation with his own
incomparable researches. A few years after the publication of his
Origin of Species, he showed by his wonderful book on orchids
that he had by no means affirmed the general truth of Knight’s
law without having engaged in special researches himself. For he
showed in this work that in almost all British orchids, and in all
the foreign species within his reach, the flowers were adapted down
to the most minute details for insect-visits, in such a way that
insect-visitors could not fail to carry the pollen to the stigmas
of other flowers. Only a few species in which self-fertilisation
regularly took place formed an exception, as yet unexplained,
to this general law; but since even in these cases the possibility
of occasional crossing was not excluded, they formed no valid
argument against the Knight-Darwin law.

This work, freed from the fundamental flaw of Sprengel’s
theory and permeated by Darwin’s acute reasoning and observation,
was a model for the study of the forms of flowers, and it gave —

PART I. | HISTORICAL INTRODUCTION, 7

a powerful impetus to further research based upon Sprengel’s
work. Even Treviranus’s well-founded objection that in most
orchids, even our native species, the operation of inséct-visitors was
only concluded indirectly from the structure of the flowers and
had not been directly observed, could not hinder this result of
Darwin’s book; on the contrary, it could only direct more general
attention to the insects that actually performed the work of
fertilisation, A paper published seven years later by Darwin (159),
enumerating the insects observed to visit a large number of native
orchids, shows to how great an extent attention had been attracted
to this point.

Another line of investigation which Darwin initiated in the
same masterly way, was the direct observation of differences
between the action of pollen from the same and from another
flower. It has been already mentioned that Sprengel instituted
experiments on self-fertilisation in the case of Hemerocallis
Julva, and that he recognised that the flowers of this plant were
not fertile to their own pollen, and other instances of the same
kind, or at least of diminished fertility upon self-fertilisation,
had been accumulated by other botanists as has been already
explained. Darwin collected these scattered facts and brought
them under Knight’s law which for the first time revealed their
full significance, and at the same time he initiated a new method of
research which placed the produce resulting from self-fertilisation
alongside of the produce of cross-fertilisation in the struggle for
existence, and so permitted the result of persistent self-fertilisation
to be ascertained under natural conditions. In numerous plants
which were found to be fertile with their own pollen, he fertilised
some flowers with their own pollen and other flowers on the same
plant with pollen from a neighbouring plant growing under the
same conditions, excluding insects with great precautions; he
allowed the resulting seeds to germinate on damp sand in the same
vessel, and then planted them in pairs on opposite sides of the
same pot; then, while all conceivable precautions were taken to
keep both sides under the same conditions, he watched the growth
of the plants to maturity. The same experiment was repeated
with the seeds produced by these, and was continued from
generation to generation.

In several cases (Jpomea purpurea, Mimulus luteus), the plants
resulting from cross-fertilisation showed even in the first generation
a marked superiority over the others; they were larger in the
proportion of four to three or even three to two, they flowered

8 THE FERTILISATION OF FLOWERS. [PART I.

earlier, and they produced more capsules. In other cases such
superiority was less marked or was imperceptible, but in no mp
case was the advantage shown upon the other side.

So these researches also gave results on the whole favourable to
Knight’s law; but probability bordering on certainty could only be
attained when researches of this kind were undertaken on the
largest scale and carried on through many generations. As far as
lay within one man’s power Darwin had fulfilled this condition,
for he had prosecuted the above-mentioned research for eleven
years. The number of individual plants produced by crossing and
also of those produced by self-fertilisation which he watched from
germination to maturity reached more than a thousand ; they be-
longed to fifty-seven species, fifty-two genera, thirty large families,
and included natives of the most various countries. The result of
this whole research may be summed up in the single sentence:
“Whenever plants which are the offspring of self-fertilisation are
opposed in the struggle for existence to the offspring of cross-
fertilisation, the latter have the advantage ;”’ whence it is clear
that all peculiarities which aid cross-fertilisation will be retained
and perfected by natural selection. But if the direct rivalry does
not occur, self-fertilisation may suffice for the propagation of the
organism for an unlimited number of generations, producing healthy
and fertile offspring.

A third line of research prosecuted by Darwin with the same
success, namely the experimental study of dimorphic and trimorphie
plants, took away the last shadow of foundation from the old
belief that species differ radically from varieties, and threw some
light upon the obscure question of hybridisation. Sprengel had
remarked, in discussing Hottonia palustris (p. 103): “Some
plants bear only flowers whose anthers are included within the tube
but whose style is exserted, and others bear only flowers whose
style is shorter and whose stamens are longer than the tube of the
corolla. I believe that this is not accidental but that it is a
disposition of nature, though I am not able to suggest its purpose.”
Subsequently this peculiar phenomenon of long-styled and short-
styled plants was recognised in several other species, and in
Lythrum salicaria three forms were found, long-styled, mid-styled,
and short-styled, without any further use being made of the facts.
Darwin subjected the peculiar sexual relations of these plants,
which he called dimorphic and trimorphic, to a closer considera-
tion ; he also performed numerous experiments, crossing the plants
in various ways, and cultivating the produce of the various unions.

a Dae: Te

PART 1. | HISTORICAL INTRODUCTION. 9

The final result of these researches, which were marked by all
his usual care and patience, may be summed up in the following
statements :—

In dimorphic heterostyled plants (species of Primula, Pul-
monaria, Linum, etc.) two forms exist, in fairly equal numbers
and growing for the most part near together; while in other
respects completely or almost completely alike, they differ from
one another in this particular, that in the flowers of the one
form the anthers stand distinctly above the stigma, while in the
other form the positions are reversed; further, that in each form
the anthers stand at the same level as the stigma in the other ;
and finally, that in the long-styled form the stigma is rough and

1-10, Primula elatior. 1—5, long-styled flower; 6—10, short-styled flower ; 2, 7, pollen-grains,
dry ; 3, 8, ditto, moist; 4. 9, stigma; 5, 10, stigmatic papille.

11—18, Pulmonaria officinalis. 11, long-styled flower in section ; 12, pollen-grains of ditto, dry ;
18, ditto, moist ; 14, short-styled flower; 15, pollen-grains of ditto, dry; 16, ditto, moist; 17, 18,
stigma and stigmatic papille common to both forms.

furnished with long papille and the polien-grains are small, while
in the short-styled form the stigmatic papille are short and
close-set and the stigma seems smooth and the pollen-grains are
larger. In trimorphic heterostyled plants (Lythrum salicaria) there
exist three forms, one with long-styled, one with mid-styled, and
one with short-styled flowers ; and in each form there are two
whorls of stamens whose anthers stand respectively at the same
height as the stigmas in the other two forms; the tallest stamens
produce the largest pollen-grains, and the shortest produce the
smallest,

10 THE FERTILISATION OF FLOWERS. [PART I.

Insects which visit the different kinds of flowers by turns in the
same way, must, since the same parts of their bodies always touch
organs at the same height in the flower, effect cross-fertilisation
both in dimorphic and trimorphic plants in such a way that
the stigma in one form of flower always receives pollen from
anthers which stand at the same height in another form. Such
crossing, which is the mode commonly occurring in nature and in
which the size of the pollen-grain is always proportional to the
length of the style that its tube has to traverse, was called by
Darwin legitimate. In dimorphic heterostyled plants there are
thus two ways in which legitimate fertilisation is possible, both
occurring regularly in nature, viz., the fertilisation of long-styled
flowers with the pollen of short-styled, and vice versdé ; similarly
there are in such cases two kinds of illegitimate fertilisation, viz.,
long-styled flowers with the pollen of long-styled, and short-styled
with the pollen of short-styled. In trimorphic heterostyled
plants, on the other hand, six modes of legitimate cross-fertilisa-
tion are possible and occur regularly in nature; and there are
twelve modes of illegitimate crossing, since each of the three
kinds of stigmas is illegitimately fertilised if it receives pollen
from either whorl of stamens in a flower of its own form or from
one whorl of stamens in each of the other two. Now Darwin
found, when he tried all the four modes of crossing in the
dimorphic plants and all the eighteen modes in the trimorphic
plants, and sowed the seeds from the resulting capsules and
again crossed the offspring in various ways, that only the “ legiti-
mate” crossings resulted in full fertility, and produced normal
and fully fertile offspring; while, on the other hand, illegitimate
crossings led to all degrees of diminished fertility or even
complete barrenness, and produced offspring which had all the
characters of bastards produced by the union of distinct species.

The result of these investigations was particularly favourable to
Knight's law, since it proved that in heterostyled plants not only
the occasional crossing of separate flowers, but the regular crossing
of separate individuals was absolutely essential for the maintenance
of the species. At the same time it broke down the sharp
boundary-line between Species and Variety which had formerly
been supposed to be found in the more or less complete sterility of
hybrids produced by crossing distinct species; and it showed, more-
over, by the complete resemblance between the offspring of
illegitimate unions in dimorphic and trimorphiec plants and the
bastard offspring of distinct species, that in the latter sterility both

PART I.] HISTORICAL INTRODUCTION. 11

at first and in the bastard offspring is not due to differences in the
general structure, but exclusively to a difference in the action
of the reproductive elements.

Attracted by Darwin’s brilliant researches on heterostyled plants
(1861-1868), many other investigators have since worked at the
same subject. Darwin has collected their results, controlling them
by his own observations and experiments and incorporating them
with the results of his later investigations. His book contains all
that we certainly know as yet concerning heterostyly, and treats also
as comprehensively of polygamous, dicecious, and _ cleistogamic
plants. It restricts the name polygamous to plants which: possess
male, female, and hermaphrodite flowers, and introduces the fol-
lowing new terms: gynodiecious, for plants which have hermaphro-
dite and also purely female individuals; androdiecious, for plants
which consist of hermaphrodite and purely male individuals ; gyno-
monecious, for plants which have hermaphrodite and purely female
flowers upon the same individual ; andromonecious, for plants in
which one individual bears hermaphrodite and male flowers.

The most complete collection of all the known facts which
contribute to prove Knight’s law is given by Darwin in his work
on the Variation of Animals and Plants under Domestication, in
which he suggests many new and fruitful lines of research ; but
the three methods of investigation which Darwin originally used
have been the chief aids in investigating the determining con-
ditions of the forms of flowers. Numerous observers, among whom
Friedrich Hildebrand, Federico Delpino, my brother Fritz Miiller,and
Severin Axell deserve special mention, have pushed forward along
these new paths that Darwin opened ; they have not only brought to
light a mass of new facts, all tending to elucidate floral mechanisms
on the basis of the Knight-Darwin law, but they have also disclosed
many new general principles. These we may briefly review.

Hildebrand, in several laborious works, demonstrated that many
floral contrivances which Sprengel had investigated, but had
explained on the theory of self-fertilisation, were really adapted
for regular cross-fertilisation; and he explained on the same
principle, and in most cases figured, many forms that Sprengel had
not examined. He extended the list of dimorphie and trimorphie
plants, and applied Darwin’s experiments to Primula sinensis,
Pulmonaria officinalis, and several species of Ozalis; he also
performed artificial self-fertilisation on these forms, and found that
it led in general to even greater sterility than the illegitimate
crossings. By his experiments on Corydalis cava, he showed that

12 THE FERTILISATION OF FLOWERS. [PART I.

self-fertilisation, which occurs spontaneously in all flowers of this
plant, is completely inoperative, that even crossing of different
flowers on the same individual gives a very poor yield, and that
only the crossing of separate plants results in full produc-
tiveness. A powerful objection to the Knight-Darwin law
was removed by this discovery. Finally, in his. Geschlechter-
Vertheilung bei den Pflanzen (1867), he has striven to show that
throughout Phanerogams cross-fertilisation of separate individuals
either takes place in all cases, or does so for the most part, or is at
least possible; and he has given the following classification of
phanerogamic flowers according to the comipletendss with which
they exclude self-fertilisation :—

A. Male and female organs in different flowers (diclinism).
Cross-fertilisation ensured, and effected by insects or by the
wind. Ex. Cannabis,

B. Male and female organs in one and the same flower (monoclinism).
1, The organs of the two sexes not developed simultaneously (dichogamy),.
(a) The male before the female! Ex. Geranium pratense.
(b) The female before the male? Ex, Luzula pilosa.
Self-fertilisation usually prevented, and cross-fertilisation
effected by insects,
2. The organs of both sexes developed simultaneously (homogamy).
(a) Flowers expanding ( flores chasmogami, Axell).
I, Anthers distant from the stigma.
a. Styles of different lengths on different plants of the same
species (Heterostyly,, Hild. ; dimorphism and trimorphism,
Darwin).

Self-fertilisation not altogether prevented, but either quite
inoperative (Pulmonaria officinalis) or yielding little
result (Primula sinensis).

8. Styles of the same length in all the flowers (Homostyly).
* Reproductive organs changing their relative positions during
the flowering period.

Self-fertilisation avoided, cross fertilisation effected by
insects. Ex. Anoda hastata.

** Reproductive organs remain unchanged in position during
the flowering period.
+ The aid of insects necessary for fertilisation.

Self-fertilisation to a great extent impossible, and cross-

fertilisation necessary. Ex. Orchidacee. Self-fertilisation

1 Sprengel calls this species of dichogamy, male-female, or dichogamia androgyna ;
Hildebrand, protandrous ; Delpino, proterandrous.

R Sprengel calls this species of dichogamy, female-male, or dichogamia gynandra ;
Hildebrand, protogynous; Delpino, proterogynous. Delpino distinguishes two
varieties, viz., proterogynia brachybiostigmatica, where the stigmas are short-lived
and. wither before the anthers ripen; and proterogynia macrobiostigmatica, where
the stigmas remain capable of fecundation until the anthers are mature, and where
consequently self-fertilisation remains possible.

PART 1, | HISTORICAL INTRODUCTION. 13

to a certain extent possible, but not necessary ; cross-
fertilisation more probable. Ex. Asclepiadee.
tt The aid of insects not essential.
Self-fertilisation possible, but cross-fertilisation also effected
by insects,
II. Anthers lying close to the stigma ; self-fertilisation inevitable.
* No seed produced without cross-fertilisation, which is effected
by insects. Ex. Corydalis cava.
** Seed is produced on self-fertilisation, but cross- fertilisation by
insects is not excluded,
(d) The flowers never expand (flores cleistogami, Kuhn).

Only self-fertilisation occurs, and all cross- fertilisation is
excluded ; but the plants have other flowers which open
and are liable to cross-fertilisation. Ex. Owalis acetosella,

Although the statements contained here with reference to the
possibility of cross- or self-fertilisation have turned out not to be
universally correct, and although the divisions merge into one
another by many intermediate forms, as Hildebrand himself
allowed, yet Hildebrand’s scheme is very well adapted to serve
as an artificial classification for the consideration of individual
cases.

Delpino described the structure of very many. flowers belonging
to the most distant orders, showing them all to be adapted for
cross-fertilisation. His descriptions are so clear and minute that
he dispenses to a large extent with illustrations. In many cases
he has directly observed the fertilising agents, and he states at
least the families or genera to which they belong. He has shown
that water as well as wind, and snails and honey-sucking birds as
well as insects, play a part in the conveyance of pollen. He has
shown in the most diverse instances how the form of the flower is
determined by the special fertilising agent, and in several families
(Maregraviacee, Marantacece, Artemisiacee, &c.) he has made happy
use of the gradual stages in adaptation to special fertilising agents
in order to trace the mutual genetic relations of the members of
the family. He has also shown strong evidence that in many cases
the distributional area of a species is determined in the first
instance by the presence of that animal which the flower has
become adapted to be cross-fertilised by. And finally, choosing the
various means of transport for the pollen as his basis of classifica-
tion, and taking advantage ingeniously of the almost complete want
of direct observations on the cross-fertilisation of Cryptogams, he
evolved the following scheme of the whole vegetable kingdom, in
all of whose members he also is of opinion that cross-fertilisation
is either certain, or probable, or at least possible.

14 THE FERTILISATION OF FLOWERS. [PART I.

I. Plants with Motile Reproductive Elements
(Zoogame).

Fucacee, Characez, Protonemez (Mosses and Liverworts), and
Proembryonatz (Ferns, Horse-tails, Rhizocarps, and Club-mosses),
whose antherozooids, corresponding to the spermatozooids of
animals, are endowed with spontaneous movement. Nearly allied
to these are the Diatoms and Conjugate, in which the whole
individual is motile.

II. Plants which require External Aid to bring their
Reproductive Elements together (Diamesogame).

A. Plants fertilised by the agency of water (hg ydroplenten
B. Plants fertilised by the wind (anemophile).
C. Plants fertilised by the aid of small animals (evidiophite),

A. Plants Fertilised by the Agency of Water.

Delpino subdivides this class into two :—

1, Plants adapted for fertilisation under water. These require
for cross-fertilisation that the stigma or the poilen-grains, or both,
should be thin and filiform, and that the pollen should be abundant
and of like specific gravity to the water (Posidonia, Cymodocea,
Zostera, Ceratophyllum, Floridec).

2. Plants adapted for fertilisation at the surface of the water.
In these the pollen is specifically lighter than water, or is borne
upon a floating raft ; the peduncles of the female flowers elongate,

sometimes aided by their spiral form, to bring the flowers to the

surface of the water (Ruppia, Vallisneria).

B. Plants Fertilised by the Wind.

The only positive character common to these is their smooth
and easily scattered pollen; the negative characters common to
them are absence of bright-coloured floral envelopes, of perfume,
and of honey.

1. The Gymnosperms are all wind-fertilised, and are charac-
terised by the absence of a stigma.

2. The anemophilous Angiosperms have for the most part
enormously developed stigmas, which project in the form of long
tails, brushes, lamine, or discs; their male flowers are very seldom
immovable, but are generally easily shaken by the wind, either the
axis of the male inflorescence, or the peduncles of the male flowers,

PART I. | HISTORICAL INTRODUCTION. 15

or the filaments themselves, being long and pendulous; in some
cases the stamens are explosive, and project all the pollen into the
air. The following five varieties may be distinguished among
anemophilous Angiosperms :—

(a) Forms with catkins, in which the axis of the male
inflorescence is movable. Ex. Corylus, Betula.

(b) Forms with pendulous flowers. Ex. Negundo fraxinifolium,
Rumen.

(c) Forms with long stamens. This is the most common variety,
including almost all Graminew, Cyperacee, Juncacew, Cannabis,
Humulus, Empetrum, Mereurialis, Ricinus, Plantago, Littorella,
Callitriche, Myriophyllum, Hippuris, the anemophilous species of
Thalictrum, &e.

(d) Explosive forms. Ex. Urtica, Parietaria, Morus.

(¢) Forms with immovable flowers. Ex. many Palms, Potamo-
geton, Triglochin, Sparganium, Typha.

C. Plants Fertilised by Animals.

These usually possess bright colours or perfumes, and supply
food to their fertilisers. The following classification has been
supplied to me by Delpino, by letter :—

I. ORNITHOPHILZ.—These plants are adapted for fertilisation
by birds, which come in search either of honey or of small insects
(Trochilide, Nectarinia, etc.). They present several different types.
What is known concerning them is founded chiefly on the reports
of travellers who were ignorant: of the principles that should guide
their investigation. Many of them possess large brilliantly-coloured
flowers, very frequently scarlet, pouched in form, upright in position,
and secreting great abundance of honey.

II. ENtoMopHILA.—Plants whose flowers are adapted for
fertilisation by insects. To this group belong all our native flowers
which possess perfume or bright colours.

III. MALacopHiLt#.—Plants whose flowers are adapted for
fertilisation by snails. (These have as yet been observed by
Delpino only.) The flowers are crowded so closely together, that
the snails in creeping over them must come in contact both with
pollen and stigmas. The plants are protected from the ravages of
their voracious guests, either by secreting an acrid fluid which kills
the snails (Alvcasia odora), or by metamorphosis of the perianth
into a thick fleshy tissue, with whose destruction the snails are
content (Rhodea japonica).

16 THE FERTILISATION OF FLOWERS. [PART I.

In further subdividing entomophilous plants, Delpino omits all
those plants which can be fertilised equally well by insects of various
orders, and limits himself to forms which he considers to be adapted
for particular insects. As such he distinguishes :—

1. Melittophile ; plants adapted for fertilisation by (the larger)
bees. These have diurnal flowers, with colours and scents attractive
to man also, partly with concealed honey (Salvia pratensis), partly
devoid of honey, and in that case with the pollen inclosed within
the flower and only becoming apparent on special treatment
(Genista tinctoria).

2. Micromelittophile ; plants adapted for fertilisation by the
smaller bees (and very many other small insects). These flowers
possess quite incomprehensible attractions for their visitors, far
more than in any other plants (Herminiwm Monorchis).

3. Myiophile ; plants adapted for fertilisation by various
Diptera. Their flowers present for the most part dull (yellowish,
wine-red, speckled) colours, their odour is for the most part disagree-
able both to man and to bees, and they display either an exposed
surface of honey or else pollen only for their visitors (Huonymus).

4. Micromyiophile ; plants adapted for fertilisation by minute
Diptera. The flower or the inflorescence forms a chamber with
a narrow entrance, often a temporary prison for the fertilising
agents ; honey is produced as a thin adhesive layer, or may be absent,
in which case the pollen is abundant (Aristolochia Clematitis, Arum).

5. Sapromyiophile ; plants adapted for fertilisation by carrion-
flies and dung-flies. The flowers have a putrid smell, but the
other characters of the group resemble those of the Myiophil
(Stapelia, Rafflesia).

6. Cantharophile ; plants adapted for fertilisation by beetles.
These are large diurnal flowers of striking colours, affording con-
venient shelter, and containing an exceedingly large supply of
pollen besides occasionally some easily accessible honey (Magnolia).

7. Psychophile ; plants adapted for fertilisation by diurnal
Lepidoptera, These have brightly-coloured diurnal flowers, whose
honey is concealed at the base of a very narrow tube (Dianthus).

8. Sphingophile ; plants adapted for fertilisation by Hawk-moths
(Sphingidw) and Noctue. These have light-coloured nocturnal
flowers, with a strong sweet scent, whose honey is concealed at
the base of a very long tube or spur (Lonicera Caprifoliwm,
Platanthera)+

' Since the above was written, Delpino has completed his work, Ulteriori osser-
vazioni sulla dicogamia nel regno vegetale, and in it the contrivances by which

rr eer =

—

ae Sea

re een

v A eT the Ty ME *7

part 1] HISTORICAL INTRODUCTION. 17

My brother, Fritz Miiller,has made many interesting observations
on South Brazilian plants, in all the three lines of research which
Darwin instituted. His results have been contributed partly to
the Jenaische Zeitschrift and Botanische Zeitung, partly to Darwin’s
Variation of Animals, ete., and are partly published for the first
time in this book. He has found in the case of various orchids
that they are not only sterile to their own pollen, but even that
the pollen and stigma of the same flower act as fatal poisons to

-one another. In various flowers (Chamissoa, Epidendrum) he has

discovered special contrivances in the act of being evolved, and
especially in Posoqueria and Faramea he has given clear proof
that certain peculiarities, advantageous under the given conditions,
have by no means attained their full perfection. The proof of this
fact deserves special attention as a strong objection to the teleolo-
gical theory. His comprehensive observations on Brazilian orchids
will; it may be hoped, soon be published in a special work.

Severin Axell published in 1869 a book on the floral mechanisms
of Phanerogams. It contains a clear historical review of the growth
of our knowledge of the sexual relations of plants, and describes
some new investigations of floral mechanisms and some experiments
on the fertility of plants after self-fertilisation, It is remarkable
for divesting of a certain onesidedness the conception that had

flowers are adapted for cross-fertilisation by animals are fully treated and very clearly
arranged. He distinguishes :—

1, Adaptations which affect the senses of sight and smell in the fertilising
agents.
(a) Colour,
(b) Scent.

2. Adaptations which affect the sense of taste: the attractions of pollen, honey,
aud other food-materials. :

3. Arrangements which direct the actions of the fertilising agents, and make
them more effective.

(a) Increase of conspicuousness by heliotropy, the position and grouping
of the flowers, enlargement of particular organs, ete.

()) The development of certain parts convenient for alighting on or
standing on.

(c) Arrangements for preserving the nectar for the use of the fertilising
agelts,

(d) ce teuiante for promoting the transfer of pollen from the anthers
to the body of the fertilising agent, and thence to the stigmas.

(ec) Arrangements for ensuring the transport of pollen from one flower to
another, or from one individual plant to another,

(f) Arrangements for regulating the number of visits of the fertilisin
agents. ;

(g) Arrangements for adapting the flowers to particular fertilising agents

ey
o

Finally, Delpino gives a classification of flowers according to their different types,
of which he distinguishes forty-seven, and he appends some remarks on the fertilising
agents of plants and their habits.

C

18 THE FERTILISATION OF FLOWERS. [PART I,

become here and there prevalent of the significance of cross-
fertilisation; and also for attempting to arrange all the floral
mechanisms of Phanerogams in a series, according to their natural
development from less perfect to more perfect forms.

The first impulse to the new investigation of flowers had been
given by Darwin’s notion of a general law that no organised being
fertilises itself for an unlimited number of generations, or, as
Darwin put it, that nature abhors perpetual self-fertilisation. And
it was natural that those investigators who worked upon the lines
laid down by Darwin should look upon the contrivances that were
favourable to cross-fertilisation and unfavourable to self-fertilisation
as so many proofs of the truth of Darwin’s conjectural law. But
they neglected to consider those flowers which frequently or
regularly fertilise themselves; or, if such flowers forced them-
selves upon their notice, they were looked upon as isolated excep-
tions, and self-fertilisation was considered, in spite of them, as
throughout injurious to plants. For instance, Hildebrand in 1867
says: ‘In most plants self-fertilisation is avoided by special
contrivances or even rendered impossible, or if it does take
place it is at least injurious;” and in 1869 he tries to prove
“the law of the avoidance of self-fertilisation,’ and to treat as
isolated exceptions Calccolaria pinnata and Morina elegans, in
which he had found self-fertilisation to take place regularly when
insect-visits fail. Similarly, in Delpino’s writings until 1869
the idea recurs in many places, quite definitely, that “nature in
general abhors self-fertilisation,”! while Darwin had only spoken of
perpetual self-fertilisation. Now Axell justly showed that this
conception entertained by Hildebrand and Delpino was unfounded,
for he brought forward in opposition to it the facts that in many
flowers self-fertilisation inevitably takes place in default of insect-
visits, and that he himself had proved by experiment in many
cases that such self-fertilisation results in the production of good
seed; further, that many aquatic plants, which under ordinary
circumstances expand their flowers at the surface of the water and
are cross-fertilised by the wind or by insects, remain closed and
submerged when the water is unusually high, and in such cireum-
stances fertilise themselves and produce seeds which propagate the
species; and finally, that many terrestrial plants, with irregular
flowers which render self-fertilisation impossible, produce, instead
of these or along with these, other flowers of simple structure

1 For instance, in No. 177, p. 55, “L’antipatia che ha Ja natura per le nozze
consanguinee ” (1869).

———

i ane

Ls

PART I.| HISTORICAL INTRODUCTION. 19

which remain closed (flores cleistogami, Kuhn) and produce seed

regularly by self-fertilisation. He supposed that the existence of

cleistogamic flowers was due partly (eg. Lamiwm amplexicaule) to

low temperature, which hindered the development of the ordinary
_ flowers, and partly to failure of the insects which under normal
- circumstances effected cross-fertilisation.

By this explanation, Axell rectified the conception that was so
distinctly uttered by Hildebrand and Delpino in their earlier
writings, viz., that cross-fertilisation is advantageous and self-
fertilisation disadvantageous for plants, by showing that though
cross-fertilisation is better than self-fertilisation, yet self-fertilisation
is infinitely better than absence of fertilisation and consequent

ee ite aml

Fia 2.—Cleistogamic and ordinary flowers of Lamium amplexicaule.

1—4, large ordinary flower, not quite twive natural size. 1, entire flower; 2, oblique view of
mouth, showing anthers and stigma ; 3, upper part of corolla just before the flower opens ; 4, nectary
(n) and ovary (02).

: 5—10, small cleistogamic flower (5-8, x 5;°9, 10, x 24). 5, entire cleistogamic flower from the
outer side ; 6, corolla, opened by force, seen from the side; 7, the same, opened less widely, seen
_ from below; 8, corolla of a cletstoraniic flower, unopened, from below; 9, essential organs of a
cleistogamic flower undergoing self-fertilisation, two stamens having been removed ; 10, ovary and

- nectary seen from the front and right.

sterility; and he also removed by his elucidation of cleistogamic
' flowers one great objection to the Knight-Darwin law,—the
argument which was used against it by H. von Mohl.

Axell founds his attempt to classify all floral mechanisms of
Phanerogams in the natural order of their development upon two
laws which he lays down as axioms: (1) Nature strives to increase
as much as possible the number of individuals in each species ;
and (2) she strives to attain the greatest possible results by the
simplest possible means. If, instead of abiding by the teleological
standpoint which personifies nature, Axell had risen to the
objective conception of nature which Darwin founded, he might

c 2

20 | THE FERTILISATION OF FLOWERS. [PART I,

have stated these two laws somewhat as follows: (1) every species
of animal and plant has, in otherwise similar circumstances, the
greater prospect of survival in the struggle for existence, the more
numerous the offspring that it leaves; (2) every individual may,
under otherwise similar conditions, be preserved the more easily
in the struggle for existence, the simpler its requirements are.
He would not then have required to state these laws as axioms,
for they are seen to be immediate consequences of the theory of
natural selection. Starting from these two laws, Axell saw in
every economy of material, space, or time, an improvement in the
mechanism of the flower. Accordingly he considers the arrange-
ment in anemophilous flowers the most primitive and most
imperfect form amongst Phanerogams, since it necessitates an
immense waste of pollen, which is avoided in cross-fertilisation
by insects. In both the anemophilous and the entomophilous
sections, Axell recognises a further advance in the transition from
dicecious to moncecious and monoclinic forms, since in this arrange-
ment there is not only increased economy of material (floral
envelopes, pollen), but increasing certainty of sexual reproduction.
In the group of monoclinic entomophilous flowers, Axell considers
that a further advance is shown in passing from dichogamic to
herkogamic flowers (those in which self-fertilisation is hindered
by the relative positions of the parts), and from these to the
heterostylic (dimorphic and trimorphic), and finally from these
to the homostylic plants with irregular flowers and again to those
with regular flowers.

According to Axell, the forms which stand nearest to the diclinie
entomophilous flowers are the dichogamic,! as in both of these
types two insect-visits are necessary for each act of fertilisation,
and many insect-visits which are paid successively to flowers in
the same stage of development remain useless to the plant.
Among homogamic entomophilous flowers, the herkogamic, in —
Axell’s opinion, share with the dichogamic forms the disadvantage
of not being able to fertilise themselves in case of need; but they
stand one stage higher, since each act of fertilisation requires only
a single insect-visit. This is also the case in heterostylic forms,
which according to Axell stand yet a stage higher, since in them
self-fertilisation, though very difficult, is not impossible. Finally,

1 Axell allows the quite unfounded supposition that the corolla begins to wither
and the secretion of honey ceases as soon as pollen is applied to the stigma to lead
him into the equally erroneous conclusion that proterandrous dichogamy only is

possible in entomophilous flowers; and this conclusion leads him. to doubt the
accuracy of many observations which are opposed to his view,

f

- PART I. | - HISTORICAL INTRODUCTION. 21

among homostylic forms, in which the possibility of self-fertilisa-
tion is unchecked, those with regular flowers stand, according to
Axell, on a higher grade that those with irregular flowers, since
they permit the visits of more various insects. Axell thus arrives

_ at the following order of development :—

,

e
3

‘
:
‘
:
,
7

A. Flowers which are fertilised by the aid of an extraneous
medium of transport (jlores chasmogamt).
I. Anemophilous forms: (a). dicecious, (b) moneecious, (c)
dichogamic (proterogynous), (7) homogamic.
If. Entomephilous forms :
a. Self-fertilisation hindered by
1, Diclinism ) Two insect-visits necessary for each
2. Dichogamy § act of fertilisation.
3.: Herkogamy? 4.5.05: + « Only one insect-visit
b. Self-fertilisation not hiner necessary for each
1. Heterostyly. 2. Homostyly act of fertilisation.

B. Flowers which fertilise themselves without the aid of an
extraneous medium of transport ( flores cleistogamt).

If we review the lines of research above described, in order to
get a clear idea of which path leads us most surely to the condi-
tions determining the forms of flowers, it becomes plain that two
different aims must be kept in view; these are closely connected,

"and sometimes within certain limits mutually depend upon one
_ another, but they cannot be confounded without danger; viz.
(1) the elucidation of floral mechanisms, and (2) the proof of the

Knight-Darwin law.
Sprengel kept in view as the sole aim of his researches the

_ explanation of the characters of flowers on certain presumptions
_ which were to be justified by the constant possibility of such expla-
nations; and his results were singularly fortunate so far as was

possible with his teleological conceptions, and without knowledge
or foreshadowing of the advantage of cross-fertilisation. Darwin
_ remedied both flaws in Sprengel’s theory, since he not only gave

complete expression by his theory of natural selection to the new

conceptions that had gradually grown up, but he also made the

definite statement, and took steps to prove it, that the effect of

_ cross-fertilisation is advantageous. But he did not content himself

with the statement that cross-fertilisation leads to a more vigorous
offspring than self-fertilisation, which would have sufficed pro-

yisionally to explain the contrivances in flowers, but he laid down

22 THE FERTILISATION OF FLOWERS. [PART I.

the much more comprehensive and general law “that no organic
being fertilises itself for a perpetuity of generations, but that
a cross with another individual is occasionally—perhaps at very
long intervals—indispensable.” And, in his exhaustive researches
on the floral contrivances of orchids, he had always kept in view
as his chief aim the establishment of this law.! |

Hildebrand and Delpino followed the same aim just as dis-
tinctly, though they expressed it in other words.? All three sought
to explain all the contrivances of flowers, presupposing the accuracy
of that general law. . If all floral mechanisms without exception
had turned out to subserve the necessity of occasional cross-fertili-
sation, the establishment of that law, and with it the foundation of
our comprehension of flowers, would have attained thereby to the
highest measure of certainty; but in point of fact, as on the one
hand more and more flowers were adduced in which cross-fertili-
sation is, under natural conditions, inevitable, on the other hand,
in at least equal proportion, more and more instances were revealed
of plants which regularly fertilise themselves and are fully pro-
ductive thereupon. Inasmuch as one cannot admit that the mere
possibility of occasional cross-fertilisation is a sufficient proof of its
necessity, it must be acknowledged that the establishment of the
Knight-Darwin law is not advanced in the least by all the
researches on the mechanism of flowers. The whole explanatory
theory of flowers, so long as it is based entirely upon this law, has
this uncertainty at its foundation.

In order to avoid this uncertainty and to secure a firm basis for
investigating the conditions determining the forms of flowers, it is
above all necessary to leave aside the Knight-Darwin law, which
can neither be proved by investigating the forms of flowers nor is
necessary for their elucidation; and to confine ourselves to the
proposition, which is sufficient for this investigation and which
can be verified by experiment, that cross-fertilisation results in
offspring which vanquish the offspring of self-fertilisation in the
struggle for existence.

1 “In my volume ‘ On the Origin of Species,’ 1 have given only general reasons for
my belief that it is an almost universal law of nature that organic beings require
an occasional cross with another individual; or, which is the same thing, that
no hermaphrodite fertilises itself for a perpetuity of generations, Having been
blamed for propounding this doctrine without giving ample facts, for which I had not

in that work sufficient space, I wish to show that I have not spoken without having

gone into details.”’—Darwin, On the Various Contrivances, ete., p. 1.

* Hildebrand calls it the law of the avoidance and the disadvantage of continual
self-fervilisation (*‘ das Gesetz der vermiedenen und unvortheilhaften stetigen Selbst-
befruchtung’”’); Delpino calls it the great law of dichogamy, or of intercrossing (“la
gran legge della dicogamia o delle nozze incrociate "),

ee ee

PART I.] HISTORICAL INTRODUCTION. 23

It is obvious that this proposition. is much narrower than the
Knight-Darwin law. For it is easily conceivable, and it is com-
patible with all known facts, that, in all plants without exception,
the offspring of self-fertilisation, as soon as they come into com-
petition with other individuals of their species which are the
offspring of cross-fertilisation, finally succumb, and that therefore
the above-mentioned proposition is thoroughly correct; but that
nevertheless many species which are regularly self-fertilised, and in
which the struggle for existence between the offspring of self-
fertilisation and of cross-fertilisation never takes place, reproduce
by self-fertilisation for an unlimited number of generations, and
that therefore the Knight-Darwin law is false.

Whether the offspring of self-fertilisation finally succumb in
the struggle for existence to the offspring of cross-fertilisation in
the same species may probably be decided in the course of a few
generations for certain plants by the above-described experiments
contrived by Darwin. Whether, on the other hand, plants in which
such competition is avoided, owing to exclusive and continuous
self-fertilisation, finally become extinct for want of crossing, can
probably in many cases not be decided. At least Darwin declares
expressly (Variation, etc., chap. xvii.) that, in order to recognise
the difference between plants produced by self-fertilisation and
those produced by cross-fertilisation, it is often absolutely necessary
to place both together in competition. And, moreover, important
facts stand opposed to the Knight-Darwin law, which have mostly
been collected by Darwin in his Variation of Animals and Plants
with scrupulous care. I may refer to the examples of plants
(mentioned in chap. xviii. of that work) which spread over
unlimited areas by asexual reproduction; to the Brazilian culti-
vated plants, described by Fritz Miiller and discussed in the third
section of this book, which after they have been multiplied for
many generations exclusively by asexual means, have lost even the
power of sexual reproduction ; to the well-known facts that numerous
mosses reproduce over great part of their area of distribution by
exclusively asexual means, and that many are only known in the
sterile form: all facts which are not easily brought into accordance
with the supposition that occasional crossing is essential for lasting
conservation.

There is good foundation, therefore, for the demand that the
explanation of floral mechanisms shall rest only on the sufficient
and demonstrable assumption that cross-fertilisation Beige more
vigorous offspring than self-fertilisation.

24 THE FERTILISATION OF FLOWERS. [PART I.

But while we must, on the one hand, strive ‘to limit our
assumptions as much as possible, in order to keep a basis.fully
demonstrable by experiment for our conclusions, we must, on the
other hand, that these conclusions may rest firm,-demand the
securest possible establishment of all accessible facts which can
influence the mutual relations between flowers and the agents
which fertilise them.

Of the various fertilising agents, wind and water are so simple
and regular in their action that it is easy to review the circum-
stances of the case, and to recognise how the comparatively simple
contrivances in anemophilous and hydrophilous plants are deter-
mined by the nature of the medium of transport. But the insects }
which act as carriers of pollen are so various in size, form, length
of proboscis, food-material, mode of movement, colour-sense, &c.,
their abundance depends on so many conditions, and their visits to
particular flowers are so influenced by weather, the competition of
other insects, the attractions of other neighbouring flowers, &c.,
that the mere investigation of floral contrivances, and the mere
general establishment of the fact that certain flowers are actually
visited and fertilised by insects, can never lead to a perception of
the primitive conditions which determine any specific peculiarity
in a flower. Only when it is accurately ascertained for many
and various flowers of the same neighbourhood by what insects and
how abundantly by each each species is visited, what in each case
each visitor comes in search of, how each acts in its visits, how the
dimensions of their bodies correspond to the dimensions of the
flowers (for instance, the length of their proboscis to the length of
the tube and spur), what parts of their bodies come in contact with
the pollen and the stigma, and so forth ; when further, for each of
these flowers, not only the form, arrangement, and order of deve-
lopment of the separate parts, but also the area of conspicuous
surfaces, the diameter of the entrance, the depth of the tube in
which the honey lies, in short every point which can affect the
insect-visitor, has been accurately ascertained—then only may we
hope, by comparing the characters of flowers and their insect-
visitors, to attain to accurate knowledge instead of the mere
surmises concerning the conditions that primitively determine any
floral character. Ae

It is plain that in such facts all previous investigations have
left wide gaps. Even Delpino, who paid more attention than any

* Snails and birds may be left out of the question, as they do not play an important
part in fertilising any native plants,

ee ee

o-—a

on Ay pe ge) +

PART I. | HISTORICAL INTRODUCTION. 25

previous observer to the insect-visitors, based his generalisations
upon far too few observations of insect-visits ; both his classifi-
cation of entomophilous flowers? and his general conclusions
concerning the fertilisers of whole families (Composite, Boraginee,
&c.) require essential modification. In no single case do the
observations hitherto made on anthophilous insects suffice either
to explain the differences between nearly allied species of flowers
or to settle the primitive conditions determining any specific
floral character. .

In order to attain to substantial knowledge concerning such
determining conditions, we must modify in two respects the modes
of investigation hitherto adopted, based upon the Knight-Darwin
law :-— | ;

(1) Instead of considering those flowers in which cross-
fertilisation in case of insect-visitors is distinctly insured or in
which self-fertilisation is distinctly opposed, we must look upon all
entomophilous flowers without exception as requiring elucidation
to the same degree; and in each species we must consider the
possible or inevitable occurrence of self-fertilisation in absence of
msects with as much care as the certainty or possibility of cross-
fertilisation in case of insect-visits.

(2) Instead of confining ourselves to the investigation of floral
mechanisms or of at most ascertaining in a general way by what
groups of insects a particular plant is visited and cross-fertilised,

“we must consider the insect-visitors with as much care as the

flowers visited by them, We must compile for each species of
flower a list as complete as possible of its visitors, in order to come
by wide comparison to a safe conclusion regarding what: effect
peculiarities in colour, odour, the secretion and concealment of the
honey, etc., have upon insect-visits, and so upon the fertilisation of
the plant. We must also take note of the way in which the

insects are fitted to obtain their floral diet, and we must try to

trace the gradual evolution of such adaptations through all stages,
since many characters of flowers and of their visitors (e.g. length
of tube and length of proboscis) have been developed in reciprocal
adaptation, and can therefore only be understood when considered
together. |

This is the path which I have sought to enter on in the present
book. How far I have succeeded in my task is for others to
decide. To permit of fair judgment, I must myself explain certain

omissions in my work.

1 Supra, p. 15.

26 THE FERTILISATION OF FLOWERS. [PART I.

I have been unable to pay equal attention to all groups of
anthophilous insects. I could neither determine by myself the
minute flies and gnats, ichneumon-flies and their allies, aphides
and species of Meligethes and Thrips, nor could I get them reliably
determined by others; these, accordingly, along with most ants
and some saw-flies, are referred to only in general terms. Noc-
turnal lepidoptera and microlepidoptera are left almost untouched
for another reason, viz. the difficulty of observing them upon
flowers in the dim light. On the other hand, I have paid close
attention to the beetles, the larger flies, bees, ‘wasps, and butterflies,
and I have determined their species with the aid of the entomo-
logists referred to in my preface. But just on account of this
simultaneous observation of so many insect groups, in the case of
the most frequented flowers it is probably only the commonest
species that have fallen into my hands; so that it will be easy
for any collector of a special group to show the most extensive
omissions in my richest lists. I indeed hope that this may be done
on the largest scale.

In hastening to publish provisionally an account of my researches,
it was further impossible for me to follow out thoroughly in the
case of all the: groups of anthophilous insects the modifications
which fit them for a floral diet, and to prove that such modifica-
tions have been evolved gradually. In thecase of bees, the most
important visitors of flowers, I have attempted to give such
proof in a special work. In the present book I must limit myself
to giving a general account of the adaptations of insects to the
flowers visited by them, so far only as seems essential for a right
understanding of the actions of insects upon flowers.

NOTES ON THE HISTORICAL INTRODUCTION,

1. Severin Axell gives in his work (17), published in 1869, a short review of
the development of our knowledge of the sexual relations of plants. He
says :—

“ Although we meet even in ancient Greek and Roman authors with dim
foreshadowings of the sexuality of some diclinic plants, it is only towards the

end of the seventeenth century that we find the existence of two sexes in the _

higher plants clearly and generally acknowledged. In 1682, Nehemias Grew
published his book The Anatomy of Plants, in which he maintained the
necessity for the pollen to act upon the pistil to form the fruit. Rud. Jac.
Canierarius? and Sebastian Vaillant? strongly supported the new views, partly

1 Epistola de sexu plantarum (Tiibingen : 1694).
* Discowrs swr la struetwre des flewrs, ete. (Paris: 1717).

a

i ts el a a at

ree Ie ae ee ee

TROP

Sa ec

PART I. | . HISTORICAL INTRODUCTION. 27

by experiment, partly by specifying the sexual organs in various forms of
flowers ; while on the other hand Tournefort! and Pontedera® tried to prove
that these views were untenable, chiefly from philosophical considerations.
The contest may be considered to have been settled in its main point by the
masterly collection of proofs of the sexuality of plants given by Linneus
in 1735.3

After it had been shown that pollination is an essential condition for the
production of seed, it still remained to show how the pollen-grains are con-
veyed to the stigma ; and attempts were made to elucidate this also, but with
less success. It was of course seen that in diclinic plants some external agency
must convey the pollen-grains from the male to the female flowers, and the
whole effect was ascribed to the wind ; in hermaphrodite flowers, on the other
hand, it was supposed that the stigma is dusted with pollen from the same
flower without the cooperation of any external agency. This had to take place
either by the anthers and stigma coming in contact, or by the pollen falling
down upon the stigma: the former would have to take place either before the
flower opened, or by movements of the reproductive organs‘ ; to explain the
latter, it was laid down as a general rule that those flowers whose stamens
overtop the style have an erect position, and that those in which the style
overtops the stamens are pendulous.> Meanwhile, since it was observed that
many flowers contain honey and are visited by insects, the idea arose that these
must be of some use in fertilisation. It was, however, supposed that in their
visits they simply shake pollen from the anthers,® and not that they carry
pollen from one flower to another. The importance and in many cases the
necessity of the action of insects was not at all recognised,’ either in general
or in any single case, if we except the observation of the fertilisation of Ficus
earica by Chalcis Psenes (Ficus in Amen. Acad. i.).

This last. observation stood for a long time isolated, until in 1761 Joseph
Gottlieb Koelreuter demonstrated the necessity of insects’ aid in several
other cases, such as Cucurbitacee, Iridee, Sambucus, and Viscum.’ This
illustrious man remarked also, that in Malvaceae, Epilobium, and Pole-
monium (Vorliuf. Nachr. p. 34), self-fertilisation is prevented by maturation
of the reproductive organs at different times, and that in these plants the
pistil of an older flower is fertilised by the aid of insects with pollen from a
younger flower.’ In the case of most plants, however, he held to the old

1 Institutiones rei herbaric (Paris: 1700).

2 Anthologia, seu de floris naturd (Patav. : 1720).

3 Fundamenta botanica (Amsterdam : 1735).

4 It was Vaillant who first observed this phenomenon. For the meaning which
was assigned to it, see Linneus, De nuptiis et seaw plantarum, 1729, first printed in
1829; and ‘* Sponsalia Plantarum,” p. 46, in Amenitates Academice, i.

5 Linneus, loc. cit. and “‘ De economid Nature,” in Amen. Acad. i.

6 « Sponsalia Plantarum” and ‘‘ De nectariis forum,” Amen. Acad. iv.

7 See, for instance, the explanation of the act of fertilisation in Viola tricolor in
** Sponsalia Plantarum,” p. 37. :

8 Vorléufige Nachricht von cinigen das Geschlecht der Phlanzn betreffenden Versuchen
und Beobachtungen (Leipzig: 1761), and Fortsetzung der vorliufigen Nachricht
(Leipzig : 1763).

After showing how well the organisation of these plants is fitted for crossing
Koelreuter remarks: ‘‘ An id aliquid im recessu habeat, quod hujuscemodi flores
numquam proprio suo pulvere, sed semper eo aliarum sue speciei impregnentur
merito queritur. Certe natura nil facit frustra.”

28 THE FERTILISATION OF FLOWERS, [PART 1,

explanation of fertilisation, which, erroneous as it was, was not contro-
verted until the appearance of Sprengel’s book and, afterwards still more
thoroughly by F. J. Schelver* and August Henschel.2 The researches of
these botanists showed clearly that in most plants pollination of the pistil
is impossible or at least improbable without the cooperation of some external
agent. The last two authors, since they did not ascribe the proper importance
to insect-visits, were led into the error of denying the sexuality of plants.
On the other hand, Sprengel has not only rendered the negative service of
showing, as the others did, how the prevalent conception of the mode of
fertilisation is directly contrary to the actual relations, but also the positive
service of removing the last objection to the sexual theory by his theory of the
adaptation of flowers to fertilisation by insects.*

2. Even Sprengel notes several instances of incomplete adaptation ; e.g. on
page 259, “Although the flowers (Lychnis dioica) being nocturnal are not
adapted for humble-bees, yet these make use of their nectar.”

3. Perhaps F. G. Kurr has reviewed most thoroughly Sprengel’s observa-
tions in his book Untersuchungen iiber die Bedeutung der Nektarien in den
Blumen, which is replete with his own observations and ideas. But even
this acute observer 4 lets us clearly trace how his ignorance of the advantage
of cross-fertilisation prevented him from agreeing with Sprengel’s explanations,
and how, along with Sprengel’s theories, he rejected his correct observations
(e.g. in the case of Campanula) in order to cling to old errors.

Severin Axell, in his above-mentioned work, cites the following later
botanists who rejected Sprengel’s discoveries ; “'Treviranus,> in upholding the
sexuality of plants against Henschel, denies altogether that the organs of the
two sexes mature at different times, and declares that the pollen and the stigma
always ripen simultaneously ; Schultz-Schultzenstein ® attacks Sprengel, and
charges him with false statements; De Candolle’ asserts: ‘M. Conrad
Sprengel a cherché 4 développer ses idées, plus fondées, je le crains, sur des
théories métaphysiques que sur la simple observation des faits;’ Mikan
criticises him for his description of the apparatus for fertilisation in the violet ;
even Robert Caspary says, ‘ quod censeo, non injuste dici potest, inter omnes
illas Sprengelii observationes, quas certissimas profert, quo modo insecta flores

fecundent, ne unam quidam esse, ex qua certe concludi possit, nullo alio modo’

flores fecundari quam auxiliis insectorum.’ Robert Brown alone, in his
well-known paper (114) on the fertilisation of Asclepiadacee and Orchidaceae,
confirmed the accuracy of Sprengel’s statement that the aid of insects is
necessary for the fertilisation of these plants, although he, like Sprengel,
failed to notice that here cross-fertilisation occurs and not self-fertilisation.”
Just as, according to these extracts, most botanists reviewed onesidedly
the weakness of Sprengel’s theory, and threw overboard the good along with
the defective ; so, with equal onesidedness, Delpino and Severin Axell have

1 Kritik der Lehre von den Greschlechtern der Phlanzen (Heidelberg : 1812),

2 Von der Sexualitét (Breslau : 1820).

3 Of. Severin Axell, “ Om det fargade hyllets betydelse for vdaten,” Bot, Notiser
Tredje haftet, 1868.

4 Loe. cit. pp. 188, 139.

5 Die Lehre vom Geschlechte der Pflanzen (Bremen: 1822),

6 Die Fortpflanzung und Ernihrung der Pflanzen (1828).

7 Organogruphie végétale, i. p. 538 (Paris: 1827).

ee ee ee |

PART 1. | HISTORICAL INTRODUCTION. 29

raised up Sprengel’s work too high, and have passed over in silence the flaw
which explains why it remained inoperative for so many generations. Delpino!
says in regard to the neglect of Sprengel,—and Severin Axell agrees with
him: “It is sad to witness this war of error against truth, especially when
the contest was begun by one who lived subsequently, and who, instead of
profiting by the truths discovered by his predecessor, only set to work foolishly
_ to deny them.” While fully acknowledging the justice of this opinion, I
think that, to be fair to both sides, we must add: Sprengel’s discovery is an
instructive example of how even work that is rich in acute observation and
happy interpretations may remain inoperative if the idea at its foundation is
defective.
4, Darwin says in his paper on the fertilisation of Papilionaceous flowers
by bees (p. 461) : “Andrew Knight many years ago propounded the doctrine
that no plant self-fertilises itself for a perpetuity of generations. After pretty
close investigation of the subject, I am strongly inclined to believe that this is
a law of nature throughout the vegetable and animal kingdoms.” As Darwin
also mentions, Knight had found by experiment in the case of the Pea
that more numerous seeds and more vigorous offspring are obtained by the
application of pollen from another flower than by self-fertilisation.

1 Sull opera ‘* La distribuzione dei sesst, etc.” del Prof. F. Hildebrand, p. 10.

PART IL.
THE INSECTS wHIcH Visit FLOWERS.

Our native flowers are visited by examples of all the main
divisions of insects; but these divisions differ greatly in regard
to the number of their anthophilous species, the extent to which
these restrict themselves to flowers for their food, their relative
importance in fertilisation, and their special adaptations for the
work. And though, as a general rule, the degree to which a group
of insects is adapted structurally for a floral diet is proportional to
their importance as fertilisers, this does not hold good always. In
the following sketch, our insect-groups are arranged according to
their progressive adaptations for obtaining food in flowers.

Orthoptera and Neuroptera.

These groups contain, at least among our native species, no
form which is habitually anthophilous, or which shows any trace
of adaptation for a floral diet. }

Earwigs (Yorficula auricularia, L.) often creep in the
daytime into flowers (Campanula, Papaver, Tropeolum, roses,
pinks, peonies, etc.), whose softer parts they feed upon at night.
Grasshoppers leap or fly on to various parts of plants, and so
occasionally on to the flowers, to feed.

I have seen a small dragon-fly (Agrion) settle repeatedly on
flowers of Spirza, apparently only to sun itself.

I have so often seen species of Hemerobius, Sialis lutaria, L.,
and Panorpa communis, L., wpon flowers of Umbelliferse, and

* Delpino once found a small green grasshopper on flowers of Ophrys aranifera
(172). Darwin states, on the authority of Mr. Swale, that in New Zealand several
species of grasshoppers have been observed to fertilise papilionaceous plants (152,

p. 451), This seems to me almost incredible. In South Brazil my brother Fritz Miller
1as fuund a Pscudomops, probably P, laticornis (Perty), common on flowers.

parr i.] THE INSECTS WHICH VISIT FLOWERS. 31

watched them bending their heads down on to the honey-secreting
disc, that I could not doubt that they were feeding there. In
the summer of 1855, I took Ascalaphus macaronius on flowers of
Umbellifers in meadows at Laibach.

The case of Panorpa communis* is quite clear, for it even visits
flowers with more deeply-seated honey (Rosacerx, Composite, ¢.9.
ELupatorium cannabinun), plunging its long beak-shaped head

_ into the tubes. One might be inclined to look upon this elongated
head as specially adapted for the quest of honey, were it not that
_ the little wingless, closely-allied Boreus hiemalis, which never visits

+ (I SP SOME

flowers, but lives among moss,” shows the same peculiarity.
It is also exceptional for Neuroptera to visit flowers. They

are more abundant than the above-named Orthoptera, and

occasionally cross-fertilisation may be effected by them; but

certainly no native flower has been modified by the agency of
_ either group.

Hemiptera.
In their importance as fertilisers, Hemiptera stand higher

than the preceding divisions, for in one group, the bugs

(Hemiptera heteroptera, Latr.), several forms are habitually
anthophilous ; whether they possess fang peer adaptations for
a floral diet is still uncertain.

The species of Anthocoris (so called from their fondness for
flowers) are fitted by their small size to creep into and suck honey

_ from very various flowers. I have taken several undetermined

species of Capsidw and Anthocoride on flowers of Umbelliferz,
Composite, and Salix, seeking honey and dusted with pollen,

» I found Tetyra nigrolineata abundantly on flowers of Daucus

Carota in Thuringia, and I have seen Pyrocoris aptera, in spring,
thrusting its proboscis (about four mm. long) into florets of the

_ dandelion; the underside of its legs and body was dusted with
_ pollen, and it seemed to be a regular and efficient fertiliser. I
_ have seen no structural adaptations for floral visits in any of

_ these insects, unless the small size of Anthocoris be of this nature ;
_ the long proboscis is found in many allied forms which never

visit flowers. No flower has been shown to be specially adapted
for the visits of field-bugs, and I know no species for whose
fertilisatiorw these insects are especially important. The structure
of their proboscis need not be considered.

1 Panorpa communis is habitually carnivorous.

* I have found Borews hiemalis repeatedly among moss on the Lichtenauer
mountain, near Willebadessen, but only in the middle of winter.

32 THE FERTILISATION OF FLOWERS. [parr r.

Coleoptera.

In contrast to the foregoing groups, Coleoptera affurd un-
equivocal adaptations to a floral diet. They are of far greater
importance as fertilisers, for many species in widely different
families feed at times on flowers, and a still greater number
confine themselves to such food exclusively. None of our
native plants are fertilised exclusively or even mainly by
Coleoptera; but the large genus Meligethes alone, the species of
which are small and can creep into most flowers, is of more
importance as a fertilising agent than all the preceding groups
taken together. On the other hand, beetles do great harm to
many flowers by nibbling their reproductive organs.

In flowers where te honey lies fully exposed (Ui mbelliferce;
Cornus, Parnassia), many species of beetles may be seen licking
it; and in flowers with exserted stamens and with the honey
concealed though accessible to short-lipped insects (Rosiflore,
Composite), beetles may be seen licking up honey, devouring
pollen or even the whole anther, or nibbling at the petals and
stamens. In flowers which have conspicuous anthers but which
secrete no honey, or where the honey lies too deeply hidden,
(Ranunculacee, Plantago), the beetles feed upon the pollen, the
anthers, and other soft parts of the flower. Besides these, flowers
which afford shelter from wind and rain (Campanula, Digitalis)
are visited by beetles, which then feed upon the pollen and the soft
tissues. In warmer countries, according to Delpino (178, L., p. 234),
several flowers of this kind, eg. Magnolia, have become adapted
for fertilisation by beetles (Cetonia) exclusively. Lastly, we
sometimes find beetles upon flowers which seem to offer none
of the advantages above described, but only allure by means of
their bright colours; thus, for instance, Cryptocephalus sericeus
and OC. Mori are often attracted by the bright yellow flowers of —
Genista tinctoria.

A review of the mode of life of insects sihdan visit flowers,
and of the families to which they belong, shows continuous
gradations from those which never visit flowers to those which
seek them as a secondary matter, and finally to those which
entirely depend upon them. This shows clearly that insects
which originally did not avail themselves of flowers gradually
became more and more habituated to a floral diet, and only

part it.} THE INSECTS WHICH VISIT FLOWERS. 33

became correspondingly modified in structure when they had
learned to depend upon such a diet exclusively: so that the view
(defended by Delpino), according to which certain flowers have
been predestined for certain insects, and vice versd, is untenable.}
In the larval state I have observed only one anthophilous
_ beetle (Helodes arcta) to affect a floral diet ; other beetles, which
as larve feed on the parts of flowers, e.g. the Apple Gouger
(Anthonomus pomorum), abandon flowers on attaining to the
perfect state. The larve of beetles which are anthophilous
when mature, are partly carnivorous (TZelephorus, Trichodes,
Coccinella), partly feeders on putrid animal matter (Dermestide),
partly feeders on living or decaying vegetable matter (Buprestida,
Cerambycide, Llateride, Chrysomelide, Curculionide, Cistela,
_ Lagria, Mordellide, Lamellicornia).
Of the carnivorous larve, most species of Coccinella and
Telephorus yemain carnivorous in the perfect state, but some
(Coccinella septempunctata, C. L4punctata, C. mutabilis, Telephorus
fuscus, T. melanurus, etc.) though they do not disdain flesh
altogether resort more or less to flowers, and TZ vichod:s in the
perfect state restricts itself absolutely to a floral diet.
| In the next group, larve which feed upon putrefying animal
matter, Dermestes retains the same habit in its perfect state,
Snover visiting flowers, and Anthrenus and Attagenus sometimes
do the same; but of these latter genera, the same species which
under favourable circumstances, ¢.g. in neglected zoological collec-
_ tions, feed for many generations on animal matter, without ever
leaving the cases whose contents they are destroying, in other
circumstances may be found by hundreds upon flowers, busily
feeding upon pollen and honey.
The most perfect gradations are exhibited, however, by those
families whose larve feed upon vegetable matter, as the following
selection shows: I have taken no species of Bostrichide on
flowers ; of the Curculionide, only a tiny part of the family resort
(and then exceptionally) to flowers, whether of the same plants
. in which they pass their earlier stages (Gymnetron campanule,
_Larinus Jacee and senilis), or of other plants on which they
find freely accessible honey (e.g. Otiorhynchus picipes on Cornus,
species of Apion on Adoxa and Chrysosplenium) ; the Chrysomelide,

a

PRO er eae «7

1 Cf. the discussion of Delpino’s teleological conceptions in the fourth section.
_ * J have found larve and pupe of Larinus senilis, F., at Miihlberg in Thuringia,
at the base of the capitula of Carlina acaulis, and the perfect insect on the leaves
_ and now and then on the flowers of the same plant.
D

—-

34 THE FERTILISATION OF FLOWERS. [PART II.

besides showing the two stages exemplified in the Curculionidae,
possess species which in the perfect state are either mainly or
exclusively confined to flowers, either feeding on honey (eg.
Clythra scopolina), or on the soft parts of the flower (e.g,

Cryptocephalus sericeus). But even in the Chrysomelide, the

anthophilous species make only a small part of the whole family.
The same holds good for the Lamellicornia, the Linnzan genera

Melolontha and Cetonia, whose anthophilous species in part feed —

upon leaves of Umbellifers, occasionally resorting to flowers, where
they feed on all the soft parts indiscriminately (Phyllopertha
horticola), and in part subsist on a floral diet, either chiefly
(Hoplia philanthus, Cetonia) or exclusively (Zrichius fasciatus).
Of the Cerambycide and Llateride, at least half of our native
species resort to flowers, some only incidentally (Rhagium,
Clytus arietis, Diacanthus cneus), but the greater number
exclusively. Finally, among the Mordellide, Cdemeride,

Malachiide, etc., whole species in the perfect state depend ,

entirely on a floral diet.

The importance of Coleoptera in fertilisation is not great
enough to make it worth while to compare closely all the
anthophilous species, genera, and families with their nearest
allies among non-anthophilous forms, in order to trace out
adaptive modifications. To disprove the teleological hypothesis
of predestination,—that certain insects are fore-ordained for
certain flowers and specially organised thereto,—it is enough,

since a gradual transition towards a floral diet has been shown —

to exist in very various families, to show by one example how the
structural adaptations appear also in the most gradual manner.
We take, as an instance, the Cerambycide.
One of the chief groups into. which, according to Westwood,”
this family is divided, viz. the Lepturidw, comprehending our
native genera Rhamnusium, Rhagiwm, Toxotus, Pachyta, Strangalia,
Leptura, and Grammoptera, is exclusively restricted in the perfect
state, for the great majority of its species,’to a floral diet;
Rhamnusium alone, to my knowledge, is never found on flowers,
but on willows and poplars; the species of Rhagiwm occur
chiefly on fallen wood, but occasionally on flowers; the specie,

1 Helodes phellandrii, for example, lives as a larva in the hollow stems, and some-
times as a beetle on the flowers of Phellandrium aquaticum ; Cassida murrea lives
in the larval state on the leaves of Pulicaria dysenterica, and sometimes as a beetle
on the flowers of the same plant. Crioceris 12punetata lives in the larval state on
Asparagus, and in the perfect state sometimes feeds on the honey of Umbellifers,

* Introduction to the Modern Classification of Insects (1839-40).

PART u.] THE INSECTS WHICH VISIT FLOWERS. 35

of Toxotus occur chiefly on flowers, rarely on shrubs; the four

remaining genera confine themselves to flowers. In proportion

to the extent to which these forms confine themselves to a floral
diet, are the structural characters displayed in them which mark
off the Lepturide from other Cerambycide, and which fit them for
_ feeding on honey, whether superficially or more deeply placed, viz.
the elongation of the head forwards, a neck-like constriction
behind the eyes, and consequently the power to direct the
_mouth forwards, the prothorax elongated and narrowed anteriorly,
. and, as I have found by a comparison of the mouth-organs, the
development of hairs upon the lobes of the maxilla.

a wi

MANS

Fic. 3,—Adaptations in Beetles for feeding on honey.

1.—Leiopus nebulosus, L. never visiting flowers. Head bent downwards, no neck behind the
eyes, prothorax broad, lobes of the maxilla (1b) furnished with bristly hairs.

2.—Clytus arietis, L., occasionally visiting the flowers of Umbelliferee and Rosacew. Head less
‘bent downwards, less broad behind the eyes ; prothorax longer and narrower ; outer lobe of maxilla
(galea, 2b) set with longer hairs,

3.—Leptura livida, F., exclusively anthophilous,—Umbellifere, Rosiflore, Composite, Convol-
vulus, and others. Head elongated and directed forwards, with a distinct neck behind the eyes ;
thorax still narrower ; both lobes of the maxilla (galea and lacinia) with long hairs (3d).
4.—Strangalia attenuata, L., exclusively anthophilous, and able to lick honey from the corolla of
Scabiosa arvensis (4 to 5mm. in length). Characters those of the preceding species, but the pro-
thorax is still longer and still more narrowed anteriorly ; both lobes ofthe maxilla have long
hairs (4b).

All these modifications form so complete and gradual a series,
from those Cerambycide which never visit flowers, and those which
‘can only lick superficially placed honey, up to Strangalia attenuata,
which can reach the honey in Scabiosa arvensis at the base of
tubular florets 4 to 6 mm. long, that the little steps by which natural
selection has operated may be clearly traced.

The order of Coleoptera is thus of special interest, as affording
‘us the first tendency of insects towards floral diet, and the first
corresponding modifications. We see how, in the most diverse
families, accustomed to widely varying nourishment, single species
have become habituated, first partially, then exclusively, to a floral

diet, and that then, by natural selection, structural changes have
D 2

36 _ THE FERTILISATION OF FLOWERS. [PART II.

developed to insure greater success in the search after food ;* and
we can distinguish how a dependence on flowers has sprung up at
different epochs of time, for in some beetles there has been time
for the attainment of adaptations, and then for their divergence
to form genera and families; while others, which have acquired
the habit later, remain isolated anthophilous species among near
allies which never resort to flowers.

Diptera and Thysanoptera.

The Diptera stand on a higher grade than the Coleoptera in the
matter of adaptation to a floral diet, and are of far more importance
for fertilisation. While only a small fraction out of all the
species of Coleoptera resort to flowers, probably the majority of the
Diptera do so. While, further, the mouth-organs of our native
beetles show only commencing adaptations, which extend at
most over small families, and may be easily traced by intermediate
stages to their origin, in flies and gnats the mouth is so deeply
modified that it is exceedingly difficult to trace back its parts to
the primitive form of the original biting insect-mouth. For our
present purpose it will suffice to discuss the structure of the
mouth-organs and the manner of using them in those Diptera which
are specially important as fertilisers of our native flowers, without
entering into questions of phylogeny.

The family of the Drone-flies, etc. (Syrphide), are alone of far
more importance as fertilisers than all our other Diptera put
together. Most of their numerous and often very common specie
depend mainly or exclusively on a floral diet, and in this family aa
found the most perfect adaptations to a diet alternately of polle:
and honey. Accordingly, to illustrate the mouth-organs of flies, 1

1 T have fully discussed the development of a dependence on flowers in beetles in
a special work. This treats of the first transition to a floral diet; the progress
towards entire dependence on honey and pollen; the attainment through practice
of a certain ease of action upon flowers, and its hereditary transmission; and

the similar behaviour of different beetles which have acquired equal degrees of structural

adaptation (H. Miiller, ‘“‘Die Entwickelung der Blwmenthdtigkeit der Insekten,”
Kosmos, Bd. ix. pp. 258-272). ,

9

* The above refers only to our indigenous forms. Tropical and subtropical beetles
show far more striking adaptations to a floral diet. For instance, in a Wemo
which my brother Fritz Miiller observed sucking flowers of Convolvulus at Itajahy
and sent to me, the maxilla are transformed into two sharp grooved bristles 12 mm. |
long, which when opposed form a tube like the proboscis of a butterfly, but of course
not capable of being rolled up (cf. H. Miiller, “ Hin Kafer mit Schmetterlingsriissel,”’
Koemos, Ba. vi. pp. 802-304 ; Hagen, Proc. of the Boston Soe. of Nat. Hist. vol. xx.
pp. 429, 430, 1880; H. Miiller, Kosmos, Bd: x. p. 56).

% I have explained my view of the descent of Diptera from Phryganide in a
paper entitled ‘‘ Anwendung der Darwin’schen Lehre auf Blumen und blumen-
besuchende Insekten,” Verh. der Naturh. Ver. fiir pr. Rheinl. u. Westf. 1869.

part u.] THE INSECTS WHICH VISIT FLOWERS. 37

take the most specialised and most abundant of the Syrphide,
Eristalis and Rhingia. |
In £ristalis the outstretched proboscis is seen to be composed of
three segments (Fig. 4, 4, 5, 6, and Fig. 5, 1): (1) the mem-
branous basal piece (9), which bears anteriorly two unpaired (A, 7)
and two paired (& &) elongated chitinous pieces, and external to the
latter two palps (J 7); (2) the membranous and very contractile
middle segment (7), only clearly separated on the lower surface ;
and (8) the extremity of the proboscis, supported beneath by a
stiff chitinous plate (c), and bearing at its apex two contiguous

ee st

Fic. 4.—Mouth-parts of Eristalis (7: 1).

: 1.—Head of E. arbustorum with retracted proboscis, from the side.

pe 2.—Ditto, from below.

* $,—Ditto, with extended proboscis, from above.

g y 4.—Extended proboscis of E. tenaw, from the side.

_~*- 5,—Ditto, from below.

_, 6.—Ditto, from above.

, a, eye; bb, antenney; ec, end-flaps of proboscis; ¢/c’, their inferior segment ; d, ve on the

_~ upper side of the point of the proboscis ; e, harder chitinous piece on the under side of the point of

the proboscis; jf, contractile middle part of the proboscis; g, contractile base of proboscis; h,
upper lip (labrum), grooved underneath to receive the unpaired piece (i), which probably represents
the two fused mandibles; k, maxilla; 1, maxillary palp ; mm, edges of the cavity on the under side
of the head into which the whole proboscis is withdrawn ; n, occipital foramen.

flaps or lips each of two parts (cc and ¢'c’), and on its upper
surface a longitudinal groove. Of the chitinous pieces at the
end of the first segment of the proboscis, only the superior un-
paired one (h), which is prolonged under the membrane to the head,
can be looked upon as an upper lip (/abrum); the lower one (7) seems
to be formed by coalescence of the two mandibles. The upper lip
(h) forms, with its concave side, a groove directed downwards into
which the piece 7 can be completely withdrawn ; between the bases
_ of these pieces 2 and 7, when drawn wide apart, the small opening
_ of the mouth can be seen. The free ends of the two chitinous

ery ee eo

38 THE FERTILISATION OF FLOWERS. [PART IT.

pieces kk arise on each side somewhat below the coalesced man-
dibles (77), and bear palps on their outer sides; these are there-
fore, without doubt, to be looked upon as the maxille with their
palps, while the basal parts of the maxilla have coalesced with
the base of the lower lip (g) (/abiwm), and are dimly visible below
the skin (4,/', Fig. 4). The contractile piece (f) and the piece
supported by the chitinous plate (¢), form together the free
superiorly-grooved anterior part of the lower lip; f and e
probably represent the submentum and mentum. The flaps
(cc) are probably not the palps but the modified paraglossz
borne on the ligula, though Burmeister prefers to consider them
as labial palps.

Let us now consider how these structures are disposed,
(1) when feeding on pollen ; (2) when sucking honey; (3) when
at rest.

(1). In feeding on pollen, the fly stretches out its extensible
proboscis, moving it, according to need, straight forwards, out-
wards, or upwards, grasps with the two flaps at its extremity a
little mass of pollen, rubs this down to single grains by a rapid
motion of the flaps, and passes it backwards by the same motion
into the groove on the lower lip; in this groove lies the upper lip,
which is grooved below, and, within that, the chitinous pieces which
are presumably formed by coalescence of the mandibles, and are now
prepared to seize the pollen. As soon as the pollen is sent back-
wards by the terminal flaps, these chitinous pieces separate slightly
the parts which immediately surround the mouth-orifice, seize the
pollen now lying in the groove of the lower lip, and thrust it
backwards into the mouth. After a few seconds the first portion
is swallowed, and the same series of actions begins anew. When the
pollen-grains are united into long strings by elastic threads, as in
(@nothera, an action of the forelegs, alternating with the movements
just described, is necessary in order to free the pollen-grains from
the threads. After the fly has torn away a little mass of pollen
from the anther, it brings up its forefeet to its mouth while stand-
ing on its mid and hindlegs; then taking the cord of elastic
threads between its forefeet, and rubbing them together as if
washing its hands, it tears the threads asunder, and frees proboscis
and legs from them. Sometimes, to clean the terminal flaps from
adhering pollen, it takes its proboscis in its forefeet, and rubs it

1 In Fristalis tenaw, which attains a length of 15 mm., the outstretched proboscis

is 7 to 8 mm. long; in Z. arbustorwm, which is 10 mm. long, the proboscis is 4 to 5
mm. long,

ei)

part u.| THE INSECTS WHICH VISIT FLOWERS. 39

gently between them. A remarkable peculiarity of the flaps,
shown in Fig. 5, makes them admirably adapted for seizing the
pollen, for grinding it down, and for passing it backwards; the
apposed surfaces of the two flaps being closely set with parallel

: ridges of chitin, by which the pollen-grains are easily held fast, and
_ shoved into the entrance of the groove (d).

2
-
7
-
a
=
=
—
—

Fic. 5.—Proboscis of Eristalis tenax, more highly magnified.

1.—The greater part of the proboscis of Eristalis tenaz, L., with the flaps applied together, and
the mouth parts slightly separated ; seen from above. When the pieces h and i are depressed in the
groove d, the mouth parts are in the position for feeding on pollen.
‘ eon end of the same proboscis with the flaps separated to show the chitinous ridges on their
nner sides.

Lettering as in the preceding figure,

This peculiarity is undoubtedly developed in connection with a
pollen diet, for it is obviously advantageous thereto; and it is only
found in those families of Diptera which visit flowers to obtain
both pollen and honey (Syrphide, Muscide, Stratiomyide), and is
absent in those which avail themselves of honey only (Bombyliide,

40 THE FERTILISATION OF FLOWERS. [PART II.

Empide, and Conopide), and in the gnats, which are also purely
suctorial.}

(2). In sucking honey the Syrphide place the grooved upper lip
(h, 1, Fig. 5), and the chitinous piece (7) together, to form a tube
which is inclined downwards and inclosed within the groove on
the lower lip. The terminal flaps may now be useful in two ways;
they may either be laid close together (as in 1, Fig. 5) while the
membranous middle joint (7) of the lower lip is so far drawn in that
the suctorial apparatus inclosed within the groove of the lower lip
protrudes in front of the flaps and dips into the fluid to be sucked ;
or they spread out the flaps wide apart so that their rough inner
surfaces rest upon the support, and the point of the suctorial
apparatus protrudes at the end of the groove on the lower lip.
Flies with swollen cushion-shaped flaps (Syrphus balteatus, Fig. 7)
act usually in the latter way, those with long narrow flaps (Rhingia,
Fig. 6) adopt exclusively the former. Both pollen-grains and fluid
which have been carried into the tube formed by the chitinous
pieces h and 1, are aided in their passage to the mouth by means of
the sucking stomach in connection with it. The maxille and their
palps seem to play no part either in sucking or in feeding on
pollen, and hence must be looked upon as useless appendages in
the Syrphide.

(3). To guard the proboscis when at rest, the fly draws the
membranous basal piece g backwards and downwards, the upper lip,
mandible, and maxillz, with their palps fold upwards, the contrac-
tile middle piece (/’) is closely drawn up, forming a few membranous
folds at the lowest part of the proboscis, the horny plate (e) and the
flaps (c) fold upwards and forwards, and the whole proboscis now lies
so deeply hidden in the deep cavity underneath the snout-like
prolongation of the head (m, 1, 2, Fig. 4), that at most the terminal
flaps protrude slightly (1, Fig. 4). On examining the head now
from below (2, Fig. 4) one sees in the cavity only the flaps ¢ ¢’,
and beneath them the upper part of the chitinous plate (e), whose
lower part lies hidden in the folds of the contractile part of the
proboscis.

A further advance on these adaptations, fitting them still more
completely for their threefold requirements, is conceivable, if to
a still more elongated proboscis there is added a greater develop-
ment of the snout-like prolongation of the head which covers it

1 | have never observed the Tabanide to feed on pollen, though their end-flaps are
roughened with chitinous ridges; but I have often found Tabanus micans and 7,
lwridus on flowers, and I think it not unlikely that they sometimes feed on pollen,

part u.] THE INSECTS WHICH VISIT FLOWERS. 41

when at rest. Such a state of things is found in Lthingia, where
the proboscis (11 to 12 mm. long), exceeds in length the whole body
(10 mm.), and is not surpassed by that of any indigenous fly.!

In anthophilous insects, the power to detect hidden honey ad-
vances parallel to the structural adaptations for securing it. When
Sprengel described flies as stupid insects, incapable of finding
out honey which lay concealed, that statement applied to the great
majority of short-tongued forms, but not at all to forms with
long proboscides, such as the Syrphide, Bombyliide, Conopide, and
Empide.

Rhingia takes a foremost place in intellectual acuteness, as
in the length of its proboscis, and there is, I think, no flower
which affords honey attainable by it, that it does not discover
and make use of. For instance, the deeply-hidden nectaries
of the Iris are more frequently visited by Rhingia rostrata

Fia. 6.—Proboscis of Rhingia rostrata, L.

1.—Side view of head with retracted proboscis.

2.—Ditto, at the moment when the proboscis begins to unfold.

8.—Ditto, with fully extended proboscis.

4.—Head, with retracted proboscis seen from below, twice as much magnified as in the three
first figures.

Lettering as in Fig, 2.

than even by humble-bees, though Sprengel (p. 74) considers
that no insects save bees can find them, and adds that this
goes without saying in the case of flies, which are so obviously
too stupid.

But even in the Syrphida, only a few species have acquired so
highly specialised a proboscis as Hristalis: the great majority have
a proboscis formed on a similar plan, shown in Fig. 7. The labium
is much shorter, its extensible middle jomt is wanting, the
terminal flaps are swollen and cushion-shaped, and there is a
corresponding diminution in intellectual power. Of the families
of Diptera besides Syrphide, the Muscide, Stratiomyide, Bombylude,
Conopide, and Empide are of some importance in the fertilisation

1 Bombylius discolor, Mik., alone equals it in the length ofits proboscis ; Bombylius
major, L., approaches it (10 mm.)

49 THE FERTILISATION OF FLOWERS. [parr us.

of flowers. Of these forms the first two families both suck honey
and feed on pollen; the last three suck honey only.

The pollen-eating Muscide and Stra-
tiomyide have the same soft, cushion-
shaped, swollen end-flaps, and the same
chitinous ridges thereon, as the Syrphide ;
and in spite of some structural differences,
they use their mouth-organs in the same
way, and retract them when at rest into
a cavity below the head. The merely suc-
torial species of Bombylius, Empis, and
Conops have end-flaps not provided with
soft cushions with horny ridges, but
formed simply of strong chitinous plates,
which serve to transmit the suctorial
apparatus; and the proboscis cannot be
withdrawn into a cavity. So we may con-

‘i,

f—

any. Dosbuatis of a clude that the power of withdrawing the
balteatus, De G. ia 7 7 :
eee ey proboscis into a cavity below the head is
Lettering as in Fig. 2. of advantage only as a protection for the

pollen-feeding apparatus, and has been
developed indirectly in relation to anthophilous habits, like the
snout-like or beak-like prolongation of the head in Syrphide.

Of the purely suctorial flies, the species of Hmpis carry their
thin, straight proboscis directed downwards, and use it preferably
in that position; accordingly they resort chiefly to erect flowers,
into which they can plunge their proboscis vertically. If the
flower is tubular, and so long as to require it, they thrust the |
whole head down into the tube, an action which the small size
of the head facilitates. The chitinous piece formed by coalescence
of the mandibles is produced into a sharp, lancet-shaped plate
(I used Hmpis tesselatum for investigation), which, guided by the
elliptical end-flaps, is used for boring into juicy structures, such as
the inner wall of the spur in Orchis. Any considerable increase
in length in a downward-directed proboscis is clearly impossible
without the development of a joint.

In the habits of the Hmpide we see clearly the transition from
blood-sucking to honey-sucking. Sometimes in a single species
the females, which require more nourishment, are blood-suckers,
while the males suck honey only.! In Paltostoma torrentium
(Blepharoceride) two different kinds of females exist together, one

' H. Miiller, Natwre, vol, xxiv. p. 214 ; Kosmos, vol. ix. pp. 415-417.

part it.] THE INSECTS WHICH VISIT FLOWERS. 43

blood-sucking, the other honey-sucking; while the males are all
alike and all feed on honey.

In the Conopide, the proboscis, which is still carried downwards,
is bent, when of considerable length, at the base, and sometimes
again near the middle; and then, in the latter case, the anterior
part shuts up into the posterior like the blade into the handle
of a pocket-knife, so that the proboscis may still be carried in
a vertical position.

The species of Bombylius, on the other bacid: carry their proboscis
(which is likewise too long to be carried downwards and unbent)
directed straight forwards, and permanently ready for action. They

Fia. 8. —Conopide and Bombyliide (Bee-flies).

1.—A Conopid, Licus ferrugineus (x 1°7).

2.—Head of ditto, with extended proboscis.
3.—Proboscis folded like the blade in a pocket-knife.
4.—A Bombylid, Bombylius major (x 1°7).

5.—Its proboscis, more highly magnified.

thus save time, sucking as they hover in the air over each flower with-
out settling, and flying rapidly from one to another. In the length
of their proboscis they approach Rhingia, Bombylius major having
a proboscis 10 mm. long, and B. discolor one of 11 to 12 mm.; they
also nearly rival Rhingia in their powers of detecting concealed
honey. The species of Bombylius, like those of Hmpis, are fitted
also for boring into succulent tissues. For the labium and the
labrum inclosed by it form two grooves uniting into a tube in
which the maxillz, as two very fine bristles, and the mandibles,
united into one broad, strong, pointed bristle, move backwards and

1 Fritz Miiller, Kosmos, vol. viii. pp. 37-42.

44 THE FERTILISATION OF FLOWERS. [PART II.

forwards. The labrum itself is drawn out into a stiff, fine point,
Both the labrum and the united mandibles, held between the long,
narrow end-flaps (paraglosse), may easily be stuck into soft tissues.
I have often seen species of Bombylius thrust their tongues into
honeyless flowers (e.g. B. canescens, Mik., into Hypericum perforatum),
and I imagine that here the boring apparatus was being brought
into action.

While, so far as I know, the species of Homtuliys and the
Conopide restrict themselves to the juices of flowers, very many
other anthophilous flies are in the habit at times of sucking all
kinds of other, often uncleanly, fluids. Thus, species of Lristalis
may be seen feeding eagerly in gutters, Scatophaga and Lucilia
on dung, Sarcophaga on putrid flesh; even Volucella bombylans,
which is so abundant on flowers, I noticed in May, 1869, feeding
on a floating carcase, and returning repeatedly to it when driven
off. Several flowers seem to have acquired an offensive smell in
relation to these habits of flies.

Of the second main division of Diptera, the gnats, the larger
forms, Tipula, Bibio, etc., are of very second-rate importance in the
fertilisation of flowers ; they occasionally lick fully exposed honey,
and so act now and then as carriers of pollen. No flower has
become specially adapted for them. Tiny species of midges, on
the other hand, eg. Psychoda phalenoides, which hide in dark
corners in the daytime and fly actively in the evening, are the
regular fertilisers of the remarkable flowers of Aristolochia
Clematitis and Arum maculatwm, which afford dark hiding-places
for their visitors, and hold them in a temporary prison; others
play an important part in the fertilisation of Adoxa and
Chrysosplenium. |

The group of Thysanoptera (Zhrips) are by their small size
(hardly 1 mm. long at most, and many times less in breadth) fitted
far better than even the Anthocoride among the Hemiptera or
Meligethes among the beetles, for entering all sorts of flowers.
Probably few flowers, if any, are altogether exempt from their
visits, and though they have seldom been detected in the con-
veyance of pollen, yet from their great abundance their value as
fertilisers must not be overlooked. It must be almost impossible
to exclude these tiny insects, when we try to isolate a plant
experimentally by means of nets. The Thysanoptera seek both
pollen and honey. They seize a single pollen-grain in their

1 Darwin, whose experiments were always marked by admirable precautions, always
kept in view ‘the possibility of Thysanoptera entering through his nets.

PART .] THE INSECTS WHICH VISIT FLOWERS. 45

mandibles, and convey it to the mouth; they obtain honey by
applying the mandibles and maxille together so as to form a short,
conical sucking-apparatus. Besides a floral diet, they avail them-
selves, according to Westwood, of other plant-juices;! they injure,

Fig. 9.—Thrips (Black-fly).

1.— Thrips, seen from above (x 30).
2.—Its head, more highly on front view.
é —Mandible. —Maxilla 5.—Labium.
6.—Leg. c, coxa; f, femur; té tibia ; t, g on the end of which is a sucking dise instead

of hooks.

for example, cucumbers and melons, and leave the leaves on which
they have settled dotted over with small dead spots. Thus they
agree with Diptera in availing themselves both of pollen and honey,
and in not restricting themselves to a floral diet.

We may here mention the young larve of Meloé, called by Kirby ? Pedi-
culus Melitte, and by Dufour Triungulinus, which resemble the Thysanoptera
in the activity of their movements, and in their minute size which permits entry
into all flowers. Although they visit flowers only to attach themselves as para-
sites to bees, they feed for the time on pollen and honey, and getting thus
dusted with pollen they play a part similar to, but even more subordinate
than, that of the Thysanoptera,

Hymenoptera.

The order of Hymenoptera takes a still higher rank than the
Diptera in regard to its adaptations for a. floral diet and its
importance in fertilisation ; for the great majority of its members,
in the perfect state, are entirely dependent upon flowers. Review-
ing the main divisions of this order, the Wood-borers (Sirea, L.) are
the only forms which I have never found upon flowers; of the ants
several species, of the Saw-flies (Zenthredo), Ichneumons (Jehnewmon,

' Introduction to the Modern Classification of Insects, ii. p. 4.
2 Monographia Apum Anglice, pl. xiv. fig. 10.

46 THE FERTILISATION OF FLOWERS. [PART II.

Bracon), Chalcididse (Pteromalus), and Ruby-tails (Chrysis), many
species, of the Wasps (Diploptera) and Sand-wasps (Fossores),
almost all which I have had the opportunity of observing, and
- of the bees all species without exception, rely almost exclusively
on a floral diet.

All these groups, excepting the last two, are only capable of
sucking honey from flat exposed surfaces, and even among the
Sand-wasps there are few species whose proboscis can reach some
millimetres into a tubular flower; so that a large proportion of
flowers are exempt from the visits of all Hymenoptera except bees.
But bees, which not only feed when in the perfect state exclusively
on the produce of flowers, but nourish their young thereon also,
are in such intimate and lifelong relations with flowers, that they
show more adaptations for a floral diet, and are more important for
the fertilisation of our flowers, and have therefore led to more
adaptive modifications in these flowers, than all the foregoing orders
put together. A closer study of bees is therefore essential for
a right. understanding of the fertilisation of many of our flowers.

The Family of Bees.

The various structural modifications in bees will be most easily
understood, if we arrange them in the natural order of genetic
descent. For the grounds of my views, I must refer the reader
to a special essay of mine on the subject of bees.? If my conclusions
are correct, bees are descended from certain Sand-wasps, which,
like the species at present existing, pursued spiders, insects

and their larvae, disabled them with their sting, carried them

to their nests, and laid an egg beside each, thus supplying the
resulting larva with living food,—while the perfect insects fed
entirely on honey and pollen; these were the founders of the new
race, who gave up the old manner of feeding the young to feed
them with a portion of their own food, disgorged from their
stomachs. The race thus started differed at first from the others
in nothing but this habit; but in the course of time, filling
an unoccupied place in the economy of nature, they increased

1 For a discussion of the genealogical relations of the families of Hymenoptera and
their gradual acquirement of proficiency in anthophilous habits, consult my recent
works, “ Wie hat der Honighiene ihre geistige Befihigung erlang ?” (Hichstddter Bienen-
zeitung, 1875, 1876 ; and note in Nature, vol. xv. p. 178) and ‘* Die Entwickelung der
Blumenthiitigkeit der Insekten,” ti. and iii.

2 Anwendung der Darwin'schen. Lehre auf Bienen,” Verh. der naturh. Ver. fiir
pr. Rhein, u. Westfal, 1872, pp. 1-96.

Pines! RS ae

parr u.] THE INSECTS WHICH VISIT FLOWERS. 47

enormously, and at last formed the widely ramified family of bees ;
the still extending branches of this family, our recent bees, show
us in many ways gradations in their adaptations to a floral diet,
which help us to recognise to some extent the lines of their
evolution. |
The species of Prosopis stand just on the same level with the
primitive ancestral types of bees. In their almost hairless bodies,
the narrow first tarsal joint, scantily provided with hairs (Fig. 10, ¢’),
and their very slightly elongated mouth-parts, they completely
resemble the Sand-wasps, and only claim to be admitted to the
family of bees by their manner of feeding the young. They fill

Fic. 10.—Right hindleg of Prosopis variegata, 9. Seen from. behind.

ce, coxa ; tr, trochanter; /, femur ; ti, tibia; t, tarsus: @, first joint of tarsus.
(The tibia and tarsus are drawn too hairy).

their brood-chambers (which are lined with a hard cement’ by
means of the broad tongue) with a mixture of disgorged honey
and pollen, which serves as food for the larve on hatching. These
little active insects, which themselves have a peculiar odour, prefer
strongly scented flowers, Reseda, Ruta, Lepidium sativum, Matricaria,
Achillea, ete., where they alternately suck honey and eat pollen.
In spite of their smooth bodies, sticky pellen adheres frequently
to them, especially to the parts of the mouth and to the slightly
hairy legs; these have feebly developed brushes on their tarsi
(Fig. 10, ¢’), by which the bee can clean the whole upper surface
of its body after burrowing, but no other part of the body. has
any development of hairs suited for collecting pollen.

48 - THE FERTILISATION OF FLOWERS. [PART II.

Though the species of Prosopis are thus no better fitted for a
floral diet than many Sand-wasps, they are of far greater import-
ance as fertilisers on account of their more frequent visits to flowers,
in procuring food for the young. We must consider minutely the
form and action of their mouth-organs, to understand the higher

HIT
Jct
" ies

pt,

ty
i

Hilti]

(3 hi
hs
Hy
iif

wii é
at ‘wisn

ty,
aT
‘
Hiyittiel
Ni}

Fig. 11.—Mouth-parts of Prosopis.

1.—Head with completely folded mouth-parts. Seen from below. ; ;

2.—Front part of head, after the mandibles have diverged and the labrum turned upwards. ~

2b.—Mouth-parts in the same position; more highly magnified.

3.—Mouth-parts, after elevation of the maxille, maxillary and labia! palps, and with the tongue
partly extended; magnified as in 2b.

Seb ja view of front region of head after complete extension of the mouth-parts; magnified
as in 1 and 2,

4b.—The completely extended mouth-parts; magnified as in 2b and 8.

lbr, labrum ; ma, mandibles ; ¢, cardo; st, stipes; la, lamina; pm, maxillary palp ; mt, mentum ;
li, ligula (tongue) ; pa, puraglosse ; pl, labial palp ; 0, eye.

and more specialised forms of mouth in bees. When at rest (1,
Fig. 11), the maxillz and Jabium in Prosopis are withdrawn into a
cavity on the lower surface of the head, which they completely
fill. They are retracted, not asin flies, by the contraction of a
membranous piece into transverse folds, but by the folding up of
stiff chitinous pieces jointed together, The two basal pieces or

part u.] THE INSECTS WHICH VISIT FLOWERS. 49

cardines of the maxille (¢¢, 4, Fig. 11), are hinged by two joints to
the sides of the cavity below the head, so that they can rotate
backwards and forwards. In the state of rest they are bent back-
wards ; the next segments (stipites) (st), and the mentum which is
placed between, are drawn back, so as to cover the cardines
completely. The lamin of the maxille (/a), with their palps
(pm) and the labial palps (p/), are also folded over, downwards
and backwards, and the mandibles (md) are laid over the bases of
these parts, and also cover the retracted tongue (/i) and the down-
ward-folded upper lip (/br, 2, Fig. 11). In the state of rest, the

mandibles alone are free to act, without any other part of the mouth

changing its place. When they are separated (2, Fig. 11), the
upper lip, the tongue, the bases of the retracted maxille, the
maxillary and labial palps, come into view.
fs When the bee wants to suck honey, it extends its maxille and
_ maxillary and labial palps forwards, and spreads out its tongue
_ (3, Fig. 11); then turning the cardines of the maxille forward
(¢ c, 4, Fig. 11) on their hinges, the maxillz and labium (mentum
and tongue) are advanced by twice the length of these cardines,
and the tongue may now be introduced into honey-receptacles if
not too deep or narrow.
The Sand-wasps possess in quite a similar manner the power of
_ folding up the lower parts of the mouth to bite, and extending
- them to suck, and so Prosopis can show no advance in fitness
_ for a floral diet beyond the ancestors of the bees. The only
peculiarity which Prosopis has developed is the habit of lining its
_ brood-cavities with slime, which hardens into a thin shell; this
_ habit necessitates a short, broad tongue, and therefore prevents
_ the development of a long tongue fitted for obtaining deeply-
_ seated honey.
Considerably higher in the scale than Prosopis, in regard to
_ such adaptations, are Sphecodes, and the closely allied, but still more
_ specialised genera, Halictus and Andrena. In all three, the tongue
_ (li, 4, Fig. 12; 1, Fig. 13) is moderately short, and is enabled to
reach more deeply-placed honey, not so much by its own length as
by the increased length of the mentum and the cardines. Unlike
Prosopis, the tongue here is pointed, and more or less covered with
hairs and fine transverse lines at the tip; since it has become
more freed from the task of nest-building,! it has grown narrower
and more elongated in many species of Andrena and Halictus, to

* These genera line their brood-cavities, which are generally subterranean, with
very little slime.

E

50 THE FERTILISATION OF FLOWERS. [PART Il.

be of greater service in honey-getting (1, Fig. 13). In a state of
rest, the lower parts of the mouth are even more securely hidden,
and the mandibles can move even more freely, in Sphecodes and
many species of Halictus than in Prosopis, for the upper lip (br, 2,
Fig. 12) folds down and completely covers the laminz and maxillary
and labial palps.

The three genera Sphecodes, Halictus, and Andrena have advanced
farther from the state of the ancestral bees in regard to the develop-
ment of their hairy coat than of their mouth-parts. Sphecodes has
made the first step in advance; Halictus and Andrena have
proceeded farther.

Fria. 12.—Sphecodes.

1.—-Right hindleg of S gibbus, L. 9., hind view. Lettering as in Fig. 10.

2.—Head, with mandibles opened, but the lower mouth-parts folded and hidden by the labrum. ©
8.—Head, after removal of the mandibles and labrum, with unfolded and protruded mouth-parts.
4.—End of labium, more highly magnified.

Lettering of 2, 3, 4, asin Fig. 11.

In Sphecodes the whole body is sparingly covered with hairs
which show the first traces of feathery branching; the legs are
more thickly clothed with hairs, especially the outer side of the
tibize of the hindlegs (#, 1, Fig. 12); the tarsi (¢’, 1, Fig. 12) are
about as narrow as in Prosopis, but the brushes on their inner side
are a little better developed. The species of Sphecodes feed their
young in a most primitive manner, viz. on the disgorged surplus of
their own food; yet they certainly derive advantage from the
hairy covering on their body and hindlegs, for the pollen which
sticks there in their visits to flowers they wipe off with their tarsal
brushes and use incidentally as food for themselves or their young.

™

D!
‘

ee

ices im

Part i.| THE INSECTS WHICH VISIT FLOWERS. 51

In the exceedingly numerous species of Halictus and Andrena,
the hairy covering of the hindlegs has so increased, and the
development of tarsal brushes has become so perfect, that the
practice of feeding the young on pollen collected by these hairs,
which was only a secondary matter in Sphecodes, is here exclusively
or mainly relied upon. The collecting hairs are spread over the
whole hindleg from the tibia to the coxa (2, Fig. 13); even the
last joint of the thorax sometimes bears two large tufts of hairs,

ij
fw

/
7
ea

ieee SA) he %
yi L
yy pea
y
EZ ;

Fic. 13.—Halictus and Andrena.

1.—Labium of Halictus quadricinetus, F, 2. mt, mentum; li, ligula (tongue); pa, paragloss ;
pl, labial palp.

2.—Right hindleg of the same bee.

3.—Metathorax and right hindleg of Andrena pratensis, Nyl. 9 ; x right tuft of hair on meta-
thorax. Lettering in 2 and 3 asin Fig. 10.

4.—Single hairs from the body of an A. pratensis taken on a willow. Numerous pollen-grains
adhere to their feathery branches.

under which considerable masses of pollen can be lodged (3, Fig. 13).
By a notable increase in breadth of the tarsi, the carrying-power
of the tarsal brushes is increased.

1 I have occasionally observed species of Andrena and Halictus feeding on pollen,
and I have seen captive specimens disgorge drops of honey yellow with pollen grains.

EB 2

52 THE FERTILISATION OF FLOWERS. _ [rarr it.

In Andrena and Halictus, although the chief supplies of pollen
are obtained by means of the hindlegs, yet in these and in all other
hairy bees the hairy covering of the body is undoubtedly of advan-
tage.. In many flowers this gets dusted without any direct effort
with a considerable quantity of pollen, which is then cleared off by
means of the tarsal brushes. In almost all bees highly specialised
for a floral diet, we find the body more or less thickly clothed with
long feathery hairs.

The development of the hairy covering is of the highest im-
portance for the fertilisation of flowers. For as the hairs easily take
up pollen, they give it up again as easily to viscid or rough stigmas.
It would far exceed the limits of our space to discuss the adaptive
modifications present in all the groups of our indigenous bees.
I can only explain the further development of the pollen-col-
lecting apparatus and of the lower parts of the mouth by a few
examples.

We have seen in Sphecodes, Halitus, and Andrena, how the
development of pollen-collecting hairs has gradually reached an
extreme pitch on those parts of the body where the burden is
least endangered by the movements of flying and creeping; viz.
on the whole of the hindleg from the tarsus to the coxa, and on
the hind part of the thorax. In forms higher than Andrena and
Halictus, this collecting apparatus has attained still greater per-
fection, in getting more and more restricted to those sections of
the hindleg to which the tarsal brushes can most readily apply
the pollen that they have collected, viz. the tarsus and tibia. In
the highest forms, this localisation of the collecting-hairs has been
attained without diminishing the mass of pollen, by an increased
growth of hairs on the tibia and tarsus and a withdrawal of the
more distal hairs: this we see most clearly in Dasypoda and
Panurgus.

In Dasypoda (1, Fig. 14), the collecting-hairs of the tibia and
tarsus have become so long that they can carry a much greater
load of pollen than the far more extensive collecting apparatus of
Andrena pratensis, Nyl. (3, Fig. 13); but the hairs on the femur,
trochanter, and coxa, are long and thick enough to take a large
share inthe work. In Panurgus (2, Fig. 14), the collecting apparatus
consists solely of the long hairs upon the tibia and tarsus. A
further advance is seen in Hucera and Anthophora, where an increase
in breadth of the pollen-collecting surfaces of the tibia and tarsus
compensates for the shortening of the collecting-hairs.

The last step in the evolution of the collecting apparatus on the

part 11.] THE INSECTS WHICH VISIT FLOWERS. 53

-hindlegs was attained through a new habit, which rendered possible
a great economy of collecting-hairs, and a great saving of time in
emptying the collecting apparatus and preparing the larval food.
This was the practice of moistening the pollen with honey before
placing it in the collecting apparatus, so as to form one connected
mass which could be easily removed from the collecting apparatus,
and at once used to feed the larve.

Macropis (1, Fig. 15) is in this way able to carry large balls
of pollen mixed with honey on its hindlegs, though the tarsus and
tibia are clothed with comparatively short hairs (2, Fig. 15).

In Bombus (8, Fig. 15) we have a still farther advance. The
pollen is kept entirely to the outer side of the hindlegs, which

Fic. 14.—Lo¢éalisation of collecting-hairs on the tibia and tarsus.

1.—Right hindleg of Dasypoda hirtipes, F. 2, seen from behind and within (x 7).
2 —The same leg of Panurgus Banksianus, K. 9 (X 7).

3.—The same leg of Anthophora (Saropoda) bimaculata, Pz. 9 (xX 7).

Lettering as in Fig. 10.

leads to a still greater economy.in collecting-hairs. For the outer
surface of the tibia of each hindleg is perfectly smooth, and only
surrounded at the edge with a fence of long hairs, some erect, some
bent inwards, forming a kind of basket, in which the pollen-mass
can be heaped high over the brim. So that not only is there a
saving of collecting-hairs, and a saving of time in unloading the
collecting apparatus, but the tarsal brushes of the hindlegs, which
even in Macropis got charged with pollen, here resume their free
use as brushes.

Apis, finally, stands on a higher level than Sombus in the
arrangement both of its collecting apparatus and its tarsal brushes.

54 THE FERTILISATION OF FLOWERS. [PART II.

While in Bombus the collecting basket is walled in by many
irregular rows of stiff hairs, still showing traces of the feathery
branching of the primitively undifferentiated hairy coat, in Apis
(5, 6, Fig. 15) these hairs have become simple smooth bristles with
no trace of feathery branching, and arranged in a few close-set rows.
The bristles of the tarsal brushes in Apis (¢’ 5, Fig. 15) are arranged
in regular rows, and much more uniformly than in Bombus (t' 8,
Fig. 15); and the now functionless tibial spurs, inherited from the
Sand-wasps, which, with most other bees, they aid in making holes

in earth, rotten wood, etc., have disappeared from the hindlegs. —
The collecting apparatus of the hindlegs, which culminates in

the hive-bee, is peculiar to one of the two main divisions of bees ;

3

;
My
Uy
fh

Yj,
Mi ht

i
NY

fd

Yo yy ATI :
; Mh

4) yy
Yh Wy

Fic, 15.—Last grades of perfection of the pollen-collecting apparatus of the hindleg.
1.—Right hindleg of Macropis labiata, Pz. 9. Seen from behind and within.
2,—The same laden with pollen of Lysimachia vulgaris.
8.—Right hindleg of Bombus Scrimshirianus, K. 8. Seen from behind and within.
4,—Its tibia, seen from the outside (pollen-basket).
5.—Right hindleg of honey-bee (Apis mellifica, L. $8). Seen from behind and within,
6.--Its tibia, seen from the outside.
Lettering as in Fig. 10.

No. 1 naturally shows only a side view of the hairs on the outer surface of the tibia and tarsus of
Macropis.

in the other division a collecting apparatus is formed by hairs on
the ventral surface of the abdomen. In these forms, at least in
our native species, we cannot trace a gradual development of the
collecting apparatus as in the others; but it possesses the same
main features in all genera of the group (Heriades, Chelostoma,
Anthidium, Osmia, Chalicodoma, Diphysis, Megachile) ; so that one
example will suffice for all.

The whole or nearly the whole ventral surface of the abdomen
is covered with a brush of stiff bristles inclined backwards, which

P ont
ee ee

8 ee heiomeey |

~

part u.] ‘THE INSECTS WHICH VISIT FLOWERS. 5D

vary in length, closeness, and colour in different species, but are
always smooth, without trace of feathery branching. This
abdominal collecting apparatus differs also in its action from the
collecting apparatus on the legs of the other forms; in the latter,
the tarsal brushes (formed of smooth stiff bristles) sweep the
pollen into the tufts of feathery hairs; in the present case, the
collecting apparatus consists of a great brush of feathery airs,
which themselves sweep up the pollen. More than nine-tenths of
the flowers visited by bees with abdominal brushes are such as are
adapted to dust the ventral surface of the bee with pollen (Zehium,
Papilionacee, Composite, etc.) without any action of the tarsal
brushes. Bees with abdominal brushes may be seen, for instance,
upon a composite flower, thrusting their tongues quickly into
one floret after another, and at the same time turning round
bodily so as to force the pollen which lies free on the surface of

Fic. 16.—Abdominal collecting apparatus.

1.—Abdomen of Osmia spinulosa, K. Ventral view. (x 7.)
2.—Lateral view of the same. (x 7.)

the capitulum between the hairs of the brush. The brush is quite
full after visits to a few capitula. I have, for instance, very often
seen Megachile lagopoda, K., acting in this manner on Onopordum
acanthium, and Osmia spinulosa, K., on Carduus acanthoides. More
rarely, bees with abdominal brushes may be seen feeding on flowers
whose pollen gets applied to their backs; in such cases, the
bee makes use of its tarsal brushes to sweep off the pollen
from the parts where it has fallen into the abdominal brushes.
I have seen Anthidiwm manicatum acting in this manner on flowers
of Ballota nigra.

The latter mode of getting pollen is adopted only exceptionally
by bees with abdominal brushes; the plan of sweeping it up directly

as their usual method, and is quicker and more productive than

the method used by bees whose collecting apparatus is on their
legs. There can be little doubt therefore that the bees with

56 THE FERTILISATION OF FLOWERS. [PART II.

abdominal brushes have adapted themselves to the flowers which
were fitted to dust their ventral surfaces (Papilionacew, Composite,
Echium, etc.), and the contrary view, that these flowers have
become adapted to the bees, is untenable, for the flowers are
visited and fertilised. by other and far more numerous insects ;
still more untenable is Delpino’s idea (e.g. in regard to Heriades
truncorum and Helianthus) of mutual predestination.

While a pollen-collecting apparatus, as we have seen, has been
developed in very different ways in the two main divisions of the
family, the adaptation of the mouth-parts for deeply-placed honey
has advanced similarly in both. In both, a natural limit to the
length of the cardines and of the mentum (by which, in Prosopis,
Sphecodes, Halictus, and Andrena, increased protrusibility of the
tongue was attained) has been fixed by the length of the head,
underneath which these parts must be withdrawn to give play to
the mandibles; and access to more deeply-placed honey is got by
lengthening the tongue itself, and by extension of the membranous
and elastic parts between the mentum and the cardines.

In the higher forms of both groups, we find that the tongue,
which was at first much shorter than the mentum, and retractile
into it, is many times as long as the mentum; the transverse
markings (absent. in Prosopis, slight in Sphecodes, well-marked in
Halictus) are present as strongly-marked transverse rings over the
greater part of the vermiform tongue ; the hairs of the tongue, which
have scarcely a definite arrangement in the lower forms, form whorls
upon each transverse ring, and can be erected or depressed forwards,
and the originally membranous and elastic parts between the
mentum and cardines are elongated and supported by chitinous
pieces, in such a way that when these fold together the mentum
is retracted between the stipites as far as the ends of the cardines,
and can be again protracted for the full length of the chitinous
pieces.

With these modifications of the lower lip, certain changes in
the maxille are closely associated, and advance similarly in both
divisions of the family. As soon as the tongue has so far increased
in length that it can no longer be quite withdrawn into the anterior
hollow of the mentum, it comes to be folded up downwards and
backwards, and both in the retracted and in the extended state it
is concealed between the laminz to avoid injury in nest-building
or in being introduced into honey-receptacles. The laminz, once.
devoted to the service of the tongue, elongate part passw with the
tongue itself; and correspondingly the labial palps and at first also

part u.] THE INSECTS WHICH VISIT FLOWERS. 57

the maxillary palps elongate also, in order to act still as organs
of touch. But the maxillary palps are soon outstripped by the
lamin, the labial palps, and the tongue, and becoming useless
gradually abort; the laminz and labial palps continue to advance
to the full extent of elongation of the tongue. This difference is
explained by the rise of a new function which the labial palps and
lamine assume, and which renders them quite indispensable and
renders the maxillary palps quite unnecessary. For as the tongue
elongates, the laminz develop more and more into a sheath closely
surrounding the tongue, which not only protects it in retraction
and when being thrust into a tubular flower, but also comes to

Fic, 17.—Tip of Hive-bee’s tongue. Highly magnified.

1.—End of tongue, seen from above. The covering bearing the whorls of hairs (Q) is torn away
at G to expose the capillary tube,

2.—The capillary tube with the covering removed, and opening into the spoon-shaped hollow.
Seen from below

3.—Side view of the same.

C, capillary tube; W, its wall; H, skin adhering to the capillary tube; G, ring, formed by
the expanded bases of the hairs ; Q, whorls of hairs; LZ, spoon-shaped hollow.

In 1 the hairy, concave upper side is seen ; in 2 the lower, convex, nearly naked side.

play the part of a suction-tube, in which the tongue, perhaps by a
progressive erection from before backwards of the whorls of hairs,
conveys the honey taken up at its point back towards the mouth.
In this the labial palps are also concerned, for their two or three
proximal joints become flattened and help the laminz in closely
surrounding the tongue, while the last joint or the two last retain
their original function as organs of touch. As soon as the proximal
joints of the labial palps have come in this manner to form part
of the suctorial apparatus, they naturally elongate pari passw with
the tongue and the lamine, and get transformed into long, thin,

58 THE FERTILISATION OF FLOWERS. [PART IT.

chitinous plates surrounding the tongue, while their terminal parts,
still acting as tactile organs, retain their original form, their short-
ness, and their free position. The maxillary palps, originally six-
jointed, get handed down as useless heirlooms, and show all stages
of abortion from six joints to none. |

A final increase in the length of the tongue over that of the
organs which insheathe it is got by making the proximal part of
the tongue coil twice round-and be retracted into the hollow end
of the mentum; so that the tongue, which in the retracted state
reaches quite to the end of its sheath, may be protruded by about the
whole length of the sheath beyond it. As subordinate adaptations
in the suctorial mechanism of bees, we have sharpening of the ends
of the laminz to pierce succulent tissues, and the development of
a membranous lobe at the end of the tongue. In the less
specialised bees, the tongue is supported throughout its whole
length by a chitinous ridge; this in the higher forms becomes
a capillary tube which opens out into the spoon-shaped hollow of
the terminal lobe. As soon as the terminal lobe reaches the
honey, a little honey ascends the capillary tube to the taste-
organs, and the bee may judge at once whether to continue
sucking or not.’ :

To follow out in detail the increasing complexity of the mouth
in bees, through all its stages, would be a work of special ento-
mological interest, as profitable as it would be comprehensive.
Having studied the first adaptations to a floral diet in Sphecodes,
Andrena and Halictus, we must pass over the manifold inter-
mediate forms,? and investigate the complex mechanism of the
mouth in the most specialised bees. I select for illustration the.
mouth of those bees which of all insects play by far the most
important part in fertilising our indigenous flowers; viz. humble-
bees (Bombus) and the hive-bee (Apis).

When we see the mouth-parts of these bees fully extended and
artificially separated (Fig. 18, 1 and 2), it seems at first sight
hardly possible that a suctorial apparatus so large and complex,
which many times exceeds the head in length, can be as com-
pletely received into a cavity below the head as it is in the least
specialised bees ; yet this takes place by help of the four folding

1 Wolff, Das Riechorgan der Biene, 1874; Hermann Miiller, Wechselbezichwngen,
p. 30. In the German edition of this book, 1873, the lobe is said to be employed
probably in licking flat surfaces of honey,

* Some of these intermediate forms are figured in my essay, ‘‘Anwendung der
Darwin’schen Lehre auf Bienen” (Verhandl. des naturhist. Vereins fiir pr. Rhein-
land und Westfalen, 1872).

PART 11.] THE INSECTS WHICH VISIT FLOWERS. 59

movements already mentioned, whose various actions we must
now consider. —

(1.) When the bee is sucking honey which is only just within
its reach, all the movable joints of its suction-apparatus, cardines,
the chitinous retractors at the base of the mentum, lamine,
labial palps, and tongue, are fully extended, as in Fig. 18, except
that the two proximal joints of the labial palps are closely applied

Fia. 18.
1.—Head of Bombus agrorum, F. 9, with completely extended and separated mouth-parts. Seen
from above (x 5).
2.—Mouth-parts of the Hive-bee, in the same position. Seen from below (x 12).

Uv, the lower joints of the labial palps modified as a tongue-sheath ; x, piece covering the mouth,
which lies between x and mt ‘epipharynz, Westwood); y, submentum (fulcrum, Kirby); 2 z,
retractors, i.e. those chitinous pieces which unite the submentum with the ends of the cardines,
and as they revolve backwards round the ends of the cardines, retract the mentum and its
appendages. (Kirby calls z z the cardines, and ¢ ¢ lora,) “¢

to the tongue below, and the laminz to the mentum and hinder
part of the tongue above. But as soon as the whorls of hairs
at the point of the tongue are wet with honey, the bee by rotating
the retractors (zz, Fig. 19) draws back the mentum, and with it
the tongue, so far that the laminz now reach as far forward as the
labial palps (i.e. to the point « in Fig. 18); and now laminz and
labial palps together, lying close upon the tongue and overlapping

60 THE FERTILISATION OF FLOWERS. [PART II.

at their edges, form a tube out of which only the part uw of the
tongue protrudes. But almost simultaneously with these move-
ments, the bee draws back the basal part of its tongue into the
hollow end of the mentum, and so draws the tip of the tongue,
moist with honey, into the tube, where the honey is sucked
in by an enlargement of the foregut, known as the sucking
stomach, whose action is signified externally by a swelling of the
abdomen.”

Fig. 19 represents the head of a humble-bee in the suctorial
position. If now the base of the tongue is drawn back into the
hollow of the mentum (as shown in Fig. 20), the tip (wv) is
drawn, wet with honey, into the tube. If the cardines (c, Fig. 19),

F

Ga. 19.—Head of Bombus hortorum, 2, with proboscis halt extended.

~

Seen from the side (x 7).. Lettering as in Figs. 11 and 18,

which are now directed vertically downwards, are rotated back-
wards, the base of the suctorial tube (at pm in Fig. 19) will
be drawn back to the opening of the mouth (between the base
of the mandibles and upper lip), and by a sucking action of the
sides of the body [and (?) a simultaneous action of the erectile
hairs on the tongue*], the honey is quickly carried into the
mouth.

1 In Apide and Vespide the “sucking stomach” is simply a lateral fold of the
foregut ; in Crabronide it is a vesicle attached by a short, narrow duct, much as
in Diptera. '

2 Of. the remarks on Lamium albwm.

3 I came to the above conclusion with regard to the action of the whorled hairs
from experiments made on bees and humble-bees under chloroform. In these, some-
times, if the tip of the tongue was dipped in syrup before complete loss of conscious-
ness, the suctorial movements took place so slowly that their separate stages could be

Seg ek eee ee

part 11.) THE INSECTS WHICH VISIT FLOWERS. 61

By now rotating the cardines (c) forwards, the whole suction-
apparatus is carried forward by twice the length of the cardines.
The retractors (zz) are now rotated forwards in their turn, and a
further advance of twice their length is given to the mentum (mt)
with its appendages, to the labial palps, and to the tongue, while
the maxillz remain in their place, and their laminz now inclose
only the mentum and the hinder part of the tongue. Finally, the
basal part of the tongue contained within the hollow part of the
mentum is projected forth, and the tip of the tongue now reaches
its farthest extension (20 to 21 mm. from the mouth in Bombus
| hortorwm), and dips again into the honey at the base of the flower.
In flowers which contain abundant honey, a humble-bee may be
seen to perform the act of sucking four or five, or sometimes even
eight or ten times, the tip of the tongue being each time dipped
into the honey, then drawn back into the sheath, and the sheath
brought up to the mouth.

(2.) To reach honey which lies less deeply, the bee need not
rotate the retractors (2); the tongue therefore remains constantly
insheathed by the laminz and labial palps, and only the basis of
the tongue moves in and out of its cavity in the mentum, bringing
its tip in and out of the extremity of the suctorial tube.

(3.) When the bee flies from one flower to another, it carries the
proboscis } extended, so as to introduce it in the act of alighting
into the tube of the flower; but the tongue is concealed within its
' sheath, to protect the delicate whorls of hairs, and to let the
terminal joints of the labial palps perform their function of tactile
organs.

So in flying from flower to flower the base of the tongue is
contained within the hollow of the mentum, and the retractors (2)
are directed backwards, while the cardines may be directed down-
wards (Fig. 19), forwards (Fig. 18, 2), or backwards, according to
the depth of the flower which the bee has in view.

clearly distinguished ; they were as described above. What went on between the
chitinous plates of the laminz and labial palps was of course invisible, but when
these parts were drawn aside, a progressive erection of the whorls from the tip of
the tongue backwards, could sometimes be clearly seen. The fact that the basal part
of the tongue, which gets drawn into the hollow of the mentum, is free from whorls,
seemed to stand in accordance with this action. At the same time, special muscles
for the erection of the whorls are not present ; and therefore my explanation becomes
unsatisfactory. In several Brazilian bees, my brother Fritz Miiller has found that
the hairs of the tongue are transformed into stalked scales, which seem hardly fitted
to drive the honey mouthwards by erection. In an undescribed azure-blue Luglossa,
the imbricated scales seem to form a tube round the tip of the tongue, so that here
suction may perhaps go on, without the tip of the tongue being withdrawn into
the sheath formed by the lamine and labial palps.
1 The whole suctorial apparatus is thus designated for shortness’ sake.

62 THE FERTILISATION OF FLOWERS. [PART IT.

(4.) The mouth-organs must assume exactly the same position
when the bee bores into delicate tissues by means of the sharp
points of its laminz; whether to secure the sap, as in the case
of our orchids which secrete no free honey, or to reach deeply-
placed honey through the aperture, as, for example, Bombus terres-
tvis does in the case of meadow-clover and many other long-tubed
flowers.

(5.) In collecting pollen, hive-bees and humble-bees use their
mouth-parts in two different ways to moisten it, according as it
is the fixed pollen of entomophilous, or the loose, easily scattered
pollen of anemophilous flowers. In the former case (e.g. when
Apis mellifica collects pollen on Salix), the bee has its suctorial
apparatus completely folded down (as in Fig. 21), bringing the
mouth-opening, which lies between the base of the mandibles and
the labrum, close over the pollen. The bee ejects a little honey on
the pollen, and then takes it up by means of its tarsal brushes and
places it in the baskets on the tibiz of its hindlegs; it often
makes use of its mandibles to free the pollen, before moistening it
with honey. In the latter case, which I have observed in Plantago
lanceolata and which will be fully described in my account of that
plant, the bee, hovering over the flower, ejects a little honey upon
the anthers from its suction-tube, which is fully extended but
completely sheathes the tongue. In this case, therefore, as when
alighting to suck upon a flower or when boring into soft tissues, the
base of the tongue is contained within the hollow of the mentum,
and the retractors are directed backwards. Since hive-bees and
humble-bees on entomophilous flowers suck honey with out-
stretched proboscis and collect pollen with it folded up, and
on anemophilous flowers collect pollen only, it follows that they
can never suck honey and gather pollen simultaneously; they
must always do first one and then the other, and since the pollen
has to be moistened with honey, the act of sucking must always
be the first.

But all forms of bees which collect dry pollen among their
feathery collecting-hairs, may, so far as the structure of the flower
permits, gather pollen and suck honey at the same time, and they
perform the latter action in exactly the same way as hive-bees
and humble-bees do. Bees with abdominal collecting-apparatus
may with the greatest ease perform both acts together on flowers
which present their pollen from below.

(6.) Finally, to place the mouth-parts in a position of rest,
or to make use of the mandibles, the bee brings all the four

part u.]| THE INSECTS WHICH VISIT FLOWERS. 63

folding movements which its suction apparatus is capable of
into play simultaneously. It draws back the base of the tongue
into the hollow end of the mentum (as in Fig. 20); folds the
tongue, together with the inclosing laminz and labial palps,
downwards and backwards (Fig. 20 shows this action beginning),
draws the retractors (z) backwards (half completed in Fig. 20),
and rotates the cardines ¢ (which in the figure are still directed
obliquely forwards), backwards ; the whole apparatus is thus folded
together, and lodged in the eavity below the head, completely
filling it (Fig. 21, 1).

# i,

Fic. 20.—Sucking apparatus of Bombus silvarum, L., half folded up. Side view.

The outer wall of the hollow end of the mentum is broken away to show the involution of the
lowest piece of the tongue, a abe.

Letters as in Fig. 18,—except: a, base of tongue; 6b, angle of fold; abc, part of tongue folded
in mentum,

When the hive-bees and humble-bees were declared to be the
most important of all insects in the fertilisation of our native
flowers, this assertion applied only to the individuals concerned

- in the care of the young, z.e. the workers among the hive-bees,

and the females and workers among the humble-bees.

In all species which provide for their own young, the males are
of much less use in fertilising plants than the females, as they only
look after their own maintenance, and accordingly neither collect

pollen nor visit flowers very diligently. Yet in all species in

64 THE FERTILISATION OF FLOWERS. [PART II.

which a more or less thick coat of feathery hairs has become
developed upon the bodies of the females, it has become trans-
mitted by inheritance to the males also,! so that they in their visits
to flowers collect pollen as well as the females. It is otherwise
with the majority of those bees which have acquired the habit of
not gathering pollen themselves to feed their young, but of laying
their eggs in the nests of other bees already stored with food.
Some of these “cuckoo-bees,” which have acquired the habit in
comparatively recent times, as the parasitic humble-bees (Apathus
or Psithyrus), have almost the same development of hairs as their
parent-form ; others which acquired it earlier, as Nomada, Epeolus,

Fic. 21.—Mouth-parts of a Humble-bee (B. hortorum, 8 ) in retracted condition.

1.—Head seen from below.
2 —Head, in side view, with proboscis bent slightly downwards. ant, antenne ; other letters as

in Fig. 18.

Celioxys, and Stelis, have almost entirely lost the hairy coat, while

retaining in perfection the suctorial apparatus which furnishes

them with their own food. Males and females of these “ cuckoo-
bees” thus plunder flowers of their honey, like the males of the
hairy bees, without being of corresponding advantage to the flowers
in the carriage of pollen ; for only very little pollen adheres to their
naked or almost naked chitinous bodies.’

1 For a further account of this hereditary transmission, see my work No. 613.

2 | have investigated the actions of male bees and of cuckoo-bees in regard to
flowers, and embodied my results in my essays, “ Die Entwickelung der Blumenthi-
tigkeit der Insekten,’’ and ‘‘ Verschiedene Blumenthitigkeit der Mannchen und
Weibchen” (Kosmos, ix. pp. 8351—870, 415—432, 1882.)

pant] THE INSECTS WHICH VISIT FLOWERS. 65

Lepidoptera.

If the chief divisions of insects are to be arranged in the order
of their importance as fertilisers of our native flowers, the first
place must decidedly be given to bees,—while the Lepidoptera take
only the second or third place, before or after the Flies. But if,
as here, we base our arrangement on the degrees of adaptation to
flowers, they undoubtedly take the first place, as the only order
which throughout, and not only in certain of its families, is fitted
for obtaining honey.

In the perfect state, butterflies, so far as they take food at all,
which is not the case in all species, restrict themselves almost
entirely to honey ; and since they take no further thought for their
young than to lay their eggs sufficiently concealed upon the food-
plant, their mouth-parts have been quite free to adapt themselves
to the easy winning of honey from the most various flowers. This
adaptation is attained by an astonishing development of the
maxillary laminz, with suppression of the greater part of the
rest of the mouth-organs. The upper lip, or labrum (/dr, 2,
Fig. 22), and mandibles (md) are aborted. The laminz of the
maxille are transformed into two immensely long, hollow, rounded
filaments, provided with semicircular grooves on their inner sur-
faces, and so forming a tube when placed in close apposition; in
the state of rest this tube is spirally coiled, and concealed between
the labial palps. The maxillary palps, which are not visible in my
figure, and also the labium, are usually more or less abortive. The
whole mechanism of the mouth, so complex and many-jointed in
bees, is thus here reduced to a long, thin, suctorial tube formed of
two apposed grooves and capable of being rolled up into small
space, and of a protective covering for this tube.

_ With this simple mechanism, Lepidoptera are able to probe
the most various flowers, whether flat or long and tubular, and
to secure their honey. Peculiar stiff, sharp-pointed appendages
at the ends of the lamine (5, Fig. 22) enable them also to tear
open delicate succulent tissues, and make use of the sap in flowers
which secrete no free honey (cf. Cytisus Laburnum, Erythrea
Centaurium, Carum, etc.). At the Cape of Good Hope, Lepidoptera
do damage to plums and peaches by piercing their skins in this
manner.! In Queensland also, the oranges are injured by a
nocturnal form, Ophideres fullonica, the powerful teeth on whose

1 Ann. and Mag. of N. H., September, 1869,
r

66 THE FERTILISATION OF FLOWERS. [PART II.

proboscis are figured and described by M. Kunkel,! Francis Darwin,?
Reginald Bligh Read,* and W. Breitenbach. My brother Fritz
Miiller thinks that some of the appendages of the proboscis in
Lepidoptera may be organs of touch or taste. These, which differ
much in number, size, and form in different species, are usually
somewhat movable, and bear at their tips a delicate rod, re-
sembling the tactile rods or olfactory hairs of Crustacea, etc.
Among the forms in which these have been noted are Prepona
Laertes, Hesperocharis Erota, Colenis Julia, Apatura Hiibneri.

Fic. 22,—Adaptive modifications in Lepidoptera.

1.—Head of Polyommatus Phileas, L., with proboscis half unrolled.

2.—Head of Vanessa Io, L., after both lamine of the maxille and the labial palps have been
cut away at their bases (x 7).

3. —Part of the lamina of Macroglossa fuciformis, L., seen from within ; more highly magnified.
a, channel.

“Transverse section of the apposed laminz of the same insect, equally magnified. aa, tube’

formed by apposition of the two channels.
5.—Point of lamina of Vanessa Atalanta, L.
Lettering in 2 as in Fig. 11.

In regard to their length, the maxillary lamine of our Lepi-
doptera show all degrees, from the proboscis of the Convolvulus
Hawk-moth, 80 mm. long, to a proboscis scarcely a millimetre
long. Their mouth-organs may be almost entirely abortive and
only comparable to those of the Phryganide, pointing to these as

1 Comptes Rendus, August 30, 1875.

2 Q. J. Micros, Sci. vol, xv. N.S., pp. 885—890.

3 Proc. Linn. Soc. N. S. Wales, August, 1878.

4 Archiv. f. Mier. Anat. Bd. xiv. pp. 308—317. Breitenbach has since pub-
lished some further studies on the boring apparatus of Lepidoptera (idbid., Bd. xv.
pp. 8—19 ; Entomol, Nachrichten, September 15, 1879, and February 15, 1880).

PART U.] THE INSECTS WHICH VISIT FLOWERS.

the ancestors of the Lepidoptera. In a former work1 I have
sought to establish the pedigree of Lepidoptera, which has been
foreshadowed by entomologists since last century: the subject has
been much more thoroughly discussed by my friend Dr. A. Speyer,?
by Mr. R. MacLachlan, and by my brother Fritz Miiller.t Apart
from tiny midges (¢.g. the fertilisers of Arum and Aristolochia),
and from those insects, especially beetles and bees, which occasionally
or habitually take up their quarters for the night in flowers,
Lepidoptera seem to be the only insects which do not confine
their visits to flowers to the daylight: a large number of their
species have acquired the habit of seeking their honey in the dusk
of summer nights and evenings, free from the competition of
other insects.2 But in our climate, summer evenings on which

twilight-loving and nocturnal Lepidoptera fly abundantly are not

_ very.numerous. Though the swift and violent movements of these
species may be due to the shortness of the period suitable for their
flight, or to the pursuit of bats, this peculiarity is of very great
importance to the plants they visit; for the more flowers will be
visited in a given time, the less time that is spent on each, and the
shorter the time that is spent in the flight from one to another.
_ This explains how many flowers have adapted themselves specially
_ to nocturnal insects, both by their light colours, visible in the dusk,
__ and by their time of opening, of secreting honey, or of emitting
| their odour. The Sphingide perform their work as fertilisers
| peculiarly rapidly, dropping their long proboscis into a flower
' while hovering over it, and instantly hastening away on their
_ violent flight to another. Accordingly most nocturnal flowers have
' adapted themselves specially to these Lepidoptera, hiding their
' honey in such deep tubes or spurs that it is only accessible to the
| Sphingide.

1 Verh. des naturh. Vereins f. pr. Rheinland und Westfalen, 1869, ‘‘ Corre-

_ spondenzblatt,” pp. 57—63.

2 Stettiner Entom. Zeitung, 1869, PP. 202—223,

3 J. Linn. Soc., Zool., vol. xi. p. 1

4 Kosmos, vol. iv. pp. ” 388—390,

> In South Brazil, according to my brother Fritz Miiller, a social wasp, Apoica
pallida, Lep., seeks honey only by night, sitting still in its nest by day.

PART III.

THE MECHANISMS OF FLOWERS.

In this section I propose to discuss such questions as the following, in
regard to a number of native or commonly cultivated plants. By what insects
is each visited? What does the insect come in quest of, and how does it
behave? In what manner does it effect transference of the pollen? What
peculiarities of the flower have special relation to the particular visitors ?

What special peculiarities of the flower aid cross-fertilisation in case of insect-_

visits? In absence of insects, can self-fertilisation take place, and to what
extent does it actually occur ?

There are few instances in which I am in a position to answer all these
questions. In some cases I have studied the structure of the flower but
have never had an opportunity of observing its insect-visitors ; in other cases
I have noted insect-visitors without studying closely the mechanism of the
flower. .

In choosing my figures I have taken account of those already existing.
In many cases I have omitted to figure flowers which happen to be well
illustrated in the works of Sprengel, Darwin, or Hildebrand (e.g. Aristolochia
Clematidis, Viola tricolor) ; in other cases I have selected a different species
of the genus (e.g. Iris, Polygala). And in most cases I have passed over with
a few words flowers which have been described elsewhere in great detail,
unless I had to correct or amplify the previous accounts. .

Professor Schenck of Weilburg has checked my identifications of the greater
part of my bees, wasps, and sand-wasps (/fossores) ; Mr. Frederick Smith has
compared all my species of bees, wasps, and sand-wasps with the collection in
the British Museum (which includes Kirby’s type-specimens) ; Dr. Speyer of
Rhoden has placed my determinations of Lepidoptera beyond dispute, and
Herr Winnertz of Crefeld has identified those Diptera concerning which I
remained doubtful. Herr Borgstette, jun., of Teklenburg, has sent me numerous
insects collected upon flowers in his neighbourhood, along with accurate
records of the plant on which each specimen was obtained.

Contractions employed in the Lists of Insects.

l.h.=licking honey ; s.=sucking ; ¢.p.=collecting pollen ; f.p,.=feeding
on pollen ; cor.=corolla; ab. abundant,

Se

PART III. | THE MECHANISMS OF FLOWERS. 69

Sld. =Sauerland (Warstein, Mohnethal, Briion) ; Tekl.=:Teklenburg (Herr
Borgstette) ; Th. Thuringia (neighbourhood of Miihlberg). In all cases in
which the locality is not specially mentioned, the observation was made near

Lippstadt.
Numbers placed in brackets after the names of insects indicate the length

of the proboscis in millimetres,

¢=male; 9? =female; § =worker.

Orv. RANUNCULACE 4.

1. CLEMATIS RECTA, L.—The flowers are destitute of honey.
When they open, the stigmas are still immature, and are covered
up partly by the stiff hairs of the pistil, and still more efficiently
by the stamens which press closely upon them. The outermost of
these latter soon begin to bend outwards, and their narrow anthers
dehisce lengthwise, so that the broad connectives appear covered
on both sides with pollen, At this time, the flowers are well fitted
to supply pollen to insects, but the stigmas are unable to retain
pollen with which the insect-visitors are coated. The bending
outwards and dehiscence of the anthers now proceeds centripetally,
and before the innermost stamens have joined the rest the stigmas
lie fully developed in the middle of the flower. Insects which come
at this period from other flowers and settle in the middle must
accomplish cross-fertilisation. Bees almost always alight in the
middle of the flower, both because they can more conveniently
reach the stamens from the centre than from the edge, and also
because the anthers near the centre are least likely to have been
already emptied. The pollen-eating flies which settle at random
on the flowers and creep about in them can produce self-fertilisation
as easily as cross-fertilisation. In default of insect-visits, self-
fertilisation readily takes place, for the outermost stigmas are often
touched by pollen at the bursting of the anthers, and frequently
part of the stigmas lie so that pollen may fall directly on them
from anthers above.

Since the flowers are destitute of honey, and all attractions for
insects therefore cease with the dispersal of the pollen, their pro-
terandrous condition has not been able to perfect itself. They are
naturally only visited persistently by pollen-seeking insects, but
by these in considerable abundance, owing to the large stock of
pollen. |

A. Hymenoptera—(a) Apide@ : (1) Prosopis signata, Pz. ¢,f.p.; (2) Andrena
Gwynana, K. 9; (3) A. albicans, K. 9; (4) Halictus sexnotatus, K. 92;
(5) Osmia rufa, L. 2; (6) Bombus terrestris, L. 9; (7) Apis mellifica, L. § ;

70 THE FERTILISATION OF FLOWERS. [PART III.

(b) Sphegide: (8) Oxybelus uniglumis, L., fp. ab. ; (9) Gorytes mystaceus, L.,
hovering over the flowers, perhaps in order to piunder flies ; (¢) Vespide:
(10) Odynerus parietum, L. 9, do. B, Diptera—(a) Syrphidw: (11) Syrphus
pyrastri, L.; (12) Helophilus floreus, L.; (13) Eristalis sepulcralis, L. ;
(14) E. arbustorum, L.; (15) Syritta pipiens, L.; (16) Xylota ignava, Pz. ;
(17) X. lenta, Mgn., all f.p.; (b) Muscide: (18) Prosena siberita, F.
C. Coleoptera—(19) Trichius fasciatus, L., devouring the whole of the anthers.

In Clematis Balearica, Rich. (C. cirrhosa, L.), the outermost
stamens are metamorphosed into spoon-shaped nectaries, which are
sucked by Bombus and Xylocopa ; in Clematis integrifolia, L., the -
inner stamens secrete honey (567, p. 8).

2. THALICTRUM AQUILEGIFOLIUM, L.—The stamens in this
plant play the part of petals: they are of a pale lilac colour,
thickened and club-shaped, and radiate outwards, forming consider-
able bundles, fifteen to twenty mm. in diameter. When the
flower opens, the stigmas are covered over and shielded from
insects by the central stamens, which are crowded together and
have their anthers still closed. In young flowers the insects
alight upon the anther-bearing points of the stiff filaments, and
climb with some difficulty around and over them in search of
pollen. In older flowers the central stamens are directed more
outwards, so that now the insects can alight more conveniently
. upon the stigmas. Thus cross-fertilisation is accomplished. In
default of insect-visits, self-fertilisation is provided for by part of
the stigmas always standing in the way of falling pollen.

_ The flowers are devoid of honey, and are Gilead oe by pollen-
seeking insects, —

A. Hymenoptera—-A pide : (1) Prosopis signata, Pz. ¢ 9, fp. ; (2) Halictus
sexnotatus, K.?, c.p.; (3) Apis mellifica, L. $,¢p. B. Diptera—Syrphide :
(4) Rhingia rostrata, L.; (5) Eristalisarbustorum, L. ; (6) E. nemorum, L. ;
(7) E. sepulcralis, L. ; (8) E. tenax, L., all f.p. C. Coleoptera—(9) Trichius
asciatus, L., devouring the anthers bodily. See also No. 609, p. 125.

Atragene alpina, L.—The pendulous violet flowers only give up
their honey to insects which can force asunder the numerous
stamens, which are set closely in several whorls,—viz. bees and
humble-bees; and in point of fact only these insects have been
observed to fertilise the plant (590, 609). The grooved inner surface
of the basal half of the filament secretes and lodges honey.

3. THALICTRUM FLAVUM, L.—This plant, which is abundant .
on meadows by the Lippe, has likewise honeyless flowers. I found

PART III. | THE MECHANISMS OF FLOWERS. 71

them to be chiefly visited by pollen-feeding flies, and on J uly I;
1868, I took the following :—

A. Diptera—(a) Syrphide; (1) Eristalis nemorum, L. ; (2) E. arbustorum,
L. ; (3) E. tenax, L. ; (4) E. sepulcralis, L., all four fp., very ab. ; (5) Syritta
pipiens, L., fp. ; (b) Muscide : (6) Pollenia Vespillo, F., fp.,ab. B. Hymen-
optera—A pide ; (7) Apis mellifica, L. 9, ¢.p.., very ab.

Thalictrum minus, L., is an anemophilous descendant of ento-
mophilous ancestors, The flowers are proterogynous, and retain, as
traces of their former entomophilous condition,—the non-simultane-
ous dehiscence of the anthers, slight cohesiveness of the pollen, and
perhaps also the conspicuous yellow colour of the anthers (590, 1.).

i

Fic. 23.—Atragene alpina, L.
A.—Flower in side view, X 3.
B.—Ditto, after removal of one sepal,
C.—One of the four large petals.
D.—One of the inner small petals, with a rudimentary anther-lobe
at one side (C and D seen from the inside).
K.—Stamen in side view.
F.—Ditto, seen obliquely from within.
G.—A carpel (O—G, x 43).
n, nectary ; sh, honey-receptacle.
Hepatica triloba, Gil. (Anemone hepatica, L.), is visited by bees
and Syrphide for its pollen (590, 1.).
Pulsatilla vulgaris, Mill. (Anemone Pulsatilla, L.)—The abun-
dant pollen is much sought by bees; honey is secreted by
rudimentary stamens reduced to short stalked knobs (590, 1.).
Pulsatilla vernalis, L.—My specimens from the Stelvio were
slightly proterogynous ; Ricca’s, from Val Camonica, were very

markedly so. The nectaries here also are modified stamens

(590, 609).

72 THE FERTILISATION OF FLOWERS. [PART III.

4, ANEMONE NEMOROSA, L.—This plant also has flowers destitute
of honey, in which, however, the sepals, not the stamens, play the
part of petals in rendering the flower conspicuous. When the
flowers open, the stigmas are still covered up and protected by the
stamens, but during the greater part of the period of flowering
both stigmas and anthers are mature at the same time, and exposed
to the touch of insects. These alight sometimes in the centre of a
flower, sometimes on a sepal, touching, therefore, either stigmas or
anthers first, and they accomplish self-fertilisation as well as cross-
fertilisation. The inclined position of the flower brings more or

Fic. 24,—Pulsatilla vernalis, L.

A.—Some of the outermost stamens metamorphosed into nectaries; and some of the next in order,

which retain their proper function. (x 7) ‘
B.—Top of style, with the stigma, more magnified.

less of the stigmas in the line of fall of the pollen, which leads to
self-fertilisation if insects’ visits fail; but experiment has yet to
decide on the efficacy of this self-fertilisation.

On February 25, 1868, out of seven flowers in my room, which
had opened simultaneously, I fertilised two with pollen from other
flowers, two with their own, and I left three untouched. On
February 29,in both of those which had received the pollen of
other flowers, all the anthers had fallen off and the ovaries were
distinctly swollen ; in the two which had been fertilised with their
own pollen, most of the anthers had fallen off and the ovaries were
swollen, but much less so than in the two former cases; the three
remaining flowers, which had been untouched, still retained all

a

— ee hl

PART III. | THE MECHANISMS OF FLOWERS. 73

their anthers. The sepals were still quite fresh in all seven flowers.
The experiment was not completed, as the plants withered in the
irregularly-heated room.

Visitors : A. Hymenoptera—(1) Halictus cylindricus, F, 9, ¢.p. ; (2) Andrena

fulvicrus, K.9, ¢.p.; (3) A. albicans, K. g, f.p. ; (4) Osmia fusca, Christ. ? ,
e«p.; (5) Apis mellifica, L. $, in hundreds, cp. and also s. B. Diptera—
(6) Scatophaga stercoraria, L. ; (7) Sc. merdaria, F., both fp. C. Coleoptera
_ —(8) Meligethes, fp. ; (9) Mordella pumila, Gyll. See also 590, I.

| Although I could not detect any honey, even by help of a
lens, I repeatedly observed a hive-bee flying from flower to
flower and thrusting its proboscis into one or more spots in the
_ base of the flower, between the sepals and carpels. Here the bees
_ doubtless tapped the juice which the flowers did not of themselves
furnish, and which the bees were in want of to moisten the pollen
that they collected at the same time. Once I saw a honey-bee
first suck honey on flowers of Cardamine pratensis and then fly off
to gather pollen on Anemone nemorosa.
“Even i in spots where Primula elatior was blooming suhestidantly:
hive-bees remained busily occupied upon the wood anemone.
Anemone alpina, L.—This species is androdicecious. The male
H flowers are distinctly smaller than the hermaphrodite, and the latter
are proterogynous. The plant is visited by numerous bees and flies,
though the flowers are devoid of honey (609).
— Anemone narcissifolia, L., is proterandrous, the stigmas not
_ being mature until the anthers have dehisced or have even been
emptied. The flowers are devoid of honey (609). |
Adonis vernalis, L.,is proterogynous and devoid of honey. The
_ visitors are chiefly bees and also ants (590, I.).
Myosurus minimus, L., is proterandrous, according to Delpino.
_ After the anthers wither, the apex of the ovary becomes lengthened
into a long cone and develops its stigmas. Delpino thinks that
_ the flowers are fertilised by flies (No. 177, p. 57).
| According to my own observations, the enormous elongation of
the axis bearing the pistil has simply the object of self-fertilising
most of the numerous stigmas by means of the small number of
_ anthers, for insect-visitors are very few. The anthers, which le
close around the axis, let their pollen emerge very gradually by
| two lateral slits, while the lengthening axis brings fresh stigmas in
contact with them. As visitors of this plant, I have observed
chiefly minute insects, not more than 1 to 14 mm. long ,viz. Diptera
of the genera Sciara, Chironomus, Scatopse, Phora, Cecidomyia,

wags

74 THE FERTILISATION OF FLOWERS. [PART III.

Oscinis, and Microphorus, besides small Pteromalide and minute
Ichneumonide, a small Haltica, some Anthomyie, and a single
Melanostoma mellina (570, vol. x. p. 129). |

5. RANUNCULUS AQUATILIS, L.—The yellowish base of each
petal serves to guide insects towards the honey; on it stands an
obliquely-placed tubercle, truncate above, and provided with a
honey-secreting hollow, which plays the parts of gland and
receptacle for the nectar. .

The anthers, which are few in number, dehisce one after the
other when the flower opens, and cover themselves all round with
pollen; the stigmas become developed at the same time, and often
come in contact spontaneously with the pollen on the anthers. |

The flowers are frequented by a large number of insects,
especially Diptera, which alight sometimes in the middle of the
flower, sometimes on the edge, and so effect self-fertilisation as well
as cross-fertilisation.

A. Diptera—(a) Syrphide: (1) Eristalis tenax, L.; (2) E. arbustorum,
L.; (3) E. nemorum, L., all three abundant, now sucking, now collecting

as

he on pe i i

pollen, plentifully dusted with pollen on the legs and especially on the soles %

of the feet; (4) Helophilus floreus, L. ; (5) Chrysogaster viduata, L., also s.
and f.p.; (b) Muscide: (6) Scatophaga merdaria, F., fp. ; various small
Muscide, s. and c.p. which escaped me. B. Hymenoptera—Apide : (7) Apis
mellifica, L. § , ad.,s. and ¢.p. ; (8) Bombus terrestris, L.9,s. C, Coleoptera—
Chrysomelide : (9) Helodes phellandrii, L., devouring anthers and petals. See
also No. 590, I., pp. 48, 49.

When the water is unusually high, the flowers of Ranunculus
aquatilis remain submerged and do not open, but fertilise
themselves (17, p. 14, 351, p. 17). eee

Ranunculus glacialis, L., is slightly proterandrous (Ricca) ;
R. alpestris, L., is homogamous or slightly proterogynous; 2. par-
nassifolius, L., and R. pyrenceys, L., var. bupleurifolius, D.C., are
proterogynous with persistent stigmas. In all these species the
shape of the nectaries is very variable (609).

6. RaNnuncuLUS FiLammuLA, L.—The flowers have scarcely
opened when the outermost anthers dehisce extrorsely, covering
their sides which are turned towards the petals with pollen, so
that insects which try to plunder the honey secreted by the little
scales at the base of the petals must of necessity dust themselves
with pollen. The stigmas are at this time concealed or almost
concealed by the inner stamens, and so are ensured against contact
with insects; they are, moreover, not yet fully developed. The

PART III. | THE MECHANISMS OF FLOWERS. 75

opening of the anthers progresses slowly towards the centre of the
flowers, and each stamen as it dehisces bends outwards and turns
its pollen-covered side outwards. These stigmas are fully developed
before the innermost stamens join the others, and the flowers,
which before could only dust their visitors with pollen, can hence-
forth be fertilised either with their own or other pollen. All
visitors which alight, bearing pollen, in the middle of the flower
effect cross-fertilisation ; others, which alight first on a petal and

Fic. 25.—Ranunculus Flammula, L.

1.—Flower just opening.
2—Flower in which the stamens are fully developed, the stigma still immature. é
3 —Esgential organs of a flower in which the stigmas are fully mature, and the anthers are not

_ yet withered.

a, immature anthers ; b, anthers about to dehisce ; c, ditto, dehisced ; d, ditto, empty ; e, carpel.

touch the anthers and then the stigmas, can accomplish either self-

fertilisation or cross-fertilisation. So if insects alight in equal

numbers in the two ways, cross-fertilisation must be the more

frequent result. After numerous observations on this and the

following species of Ranunculus, I am able to state that the two
modes of alighting are equally common for small insects; but all
larger insects (which are about as long as the diameter of the
flower) come in contact with the stigmas and the anthers at the

76 THE FERTILISATION OF FLOWERS. [PART III.

same time, and therefore must dust the stigmas with pollen from
other flowers ; hence the cross-fertilisations are still more numerous
than the self-fertilisations. In default of insect-visits, the power
of self-fertilisation is retained, some of the outermost stigmas being
often touched by pollen from the innermost anthers.

Although the arrangement of the flower is quite like that of
the following species of Ranunculus, #. Flammula is very sparingly
visited by isects, one reason at least being that its flowers are
much smaller and less conspicuous.

Visitors: A. Diptera—(a) Syrphide: (1) Syritta pipiens, L., ¢.p. and s.
(2) Cheilosia, sp. fp.; (8) Melithreptus teniatus, Mgn., fp. and s.; (bd)

inti ies le at ees,

ae se a

Muscide : (4) Scatophaga merdaria, F., f.p.; (5) Anthomyia sp. B.Hymen-

optera—Apide : (6) Halictus cylindricus, F. 2, cp. ; (7) H. flavipes F. 9,
cp. C. Lepidoptera—(8) Satyrus pamphilus, L., s.

Ranunculus montanus, L., is proterogynous with persistent
stigmas. (609).

7. RANUNCULUS ACRIS, L., R. REPENS, L., R. BULBOsUS, L.—
These species agree with Rk. Hlammula in the structure of their
flowers, and with each other in their habitat, in the conspicuousness
of their flowers, and therefore also in the insects which visit them.
Mr. "Thomas Whitelegge (No. 774) states that they are all some-
times gynodicecious. I have observed very many of the following

visitants in equal abundance and similarly engaged on all these ~

species; and I have even noticed the hive-bee, which in general

keeps strictly to one species of flower, pass from Ranunculus acris

to R. repens and R. bulbosus, or vice versd, without any distinction.
I accordingly catalogue the visitors of these three species together.

A. Diptera—(a) Empide: (1) Empis. tesselata, F., s.; (b) Asilide;: (2)
Dioctria atricapilla, Mgn. (Tekl. B.); (c) Syrphide : (3) Chrysotoxum arcu-
atum, L. (Sld.), s. and f.p. ; (4) Chr. festivum, L., s.; (5) Pipiza funebris,
Mgn.,s. ; (6) P. chalybeata, Mgn., f.p.; (7) Chrysogaster Macquarti, Loew. ;
(8) Ch. viduata, L., very ab., both s, and f.p.; (9) Cheilosia pubera, Zett.,
f.p., ab. ; (10) Ch. albitarsis, Mgn., ab.,s. and f.p.; (11) Melanostoma mellina,
L., s.; (12) Platycheirus albimanus, F. (Tekl. B), fp. ; (13) Syrphus ribesii,
L.; (14) Eristalis tenax, L.; (15) E. arbustorum, L.; (16) E. nemorum,
L. ; (17) E. sepulcralis, L.; (18) Melithreptus scriptus, L. ; (19) M. pictus,
Mgn.; (20) M. teeniatus, Mgn. ; (21) Syritta pipiens, L.,—the last nine ab.,
both s. and t.p.; (d) Muscidw: (22) Cyrtoneura ccerulescens, Meq., s. ;
(23) Anthomyia, sp. B. Coleoptera—(a) Nitidulide; (24) Meligethes, very
ab. s. and f.p.; (b) Dermestide: (25) Byturus fumatus, F., fip., ab. ; (©)
Buprestide : (26) Anthaxia nitidula, L. in copula on flowers of FR. repens;
(d) Mordellide ; (27) Mordella aculeata, L, ; (28) M. pusilla, Dej. ; (29) M.

.
:

PART III. | THE MECHANISMS OF FLOWERS. 77

pumila, Gyll.; (e) Cidemeride: (30) Cidemera virescens, L., ab.; (/)
Cistelide: (31) Cistela murina, L., devouring the petals and stamens ;
(g) Cerambycidw : (32) Strangalia nigra, L., do.; (hk) Chrysomelide: (33)
Helodes aucta, F., devouring the petals, along with its larvee (May 24, 1870) ;
(34) Cryptocephalus sericeus, L., devouring the anthers. C. Hymenoptera,—(a)
Tenthredinide : (35) Cephus spinipes, Pz., ab., s. and devouring the anthers ;
(36) Cephus, small undetermined species; (b) Sphegide: (87) Oxybelus
_ uniglumis, L. ; (c) Vespide: (88) Odynerus spinipes, H. Sch. 2 (quinque-
fasciatus, F.) ; (a) Apide : (39) Prosopis hyalinata, Sm. ¢, s. and f.p.; (40)
Halictus longulus, Sm. ?, s.; (41) H. flavipes, F.?, c.p. ; (42) H. villosulus,
_ K. 9; (43) H. sexsignatus, Schenck, ?, s.; (44) H. rubicundus, Chr. ?, s. ; (45)
_ H. quadricinctus, F.?, cp. ; (46) H. leucozonius, Schr. 9, laden with poilen,
sheltering itself from the rain in flowers of R. bulbosus (June 10, 1871) ;
(47) H. zonulus, Sm. ¢,s.; (48) H. cylindricus, F. 2, e¢.p.; (49) H. maculatus
Sm.? ¢,s. and «p.,ab.; (50) H. nitidiusculns, K.?,s.; (51) H. sexnotatus,
_K.9,cp. and s.; (52) Andrena fulvicrus, K.? ¢, s. and c.p., ab.; (53) A.
albicans, K. 9 ¢, do.; (54) A. albicrus, K.¢,s.; (55) Panurgus calcaratus
_ Scop.,.s.; (56) Chelostoma florisomne, L. 2? ¢, cp. and s.; (57) Osmia
rufa, L.¢, s.; (58) Apis mellifica, L. $, s. D. Lepidoptera—(59) Lyczna
icarus, Rott. ; (60) Satyrus pamphilus, L. ; (61) Polyommatus Phloeas, L.; (62)
Euclidia glyphica, L., alls. See also No. 590, 1., pp. 49—59 ; No. 609, p. 135.

If we compare the insect-visitors of these species of Ranunculus
with those of the typical Umbelliferze, we observe the following
remarkable differences. (1) Since the honey lies less exposed,
_ those insects which are least fitted for sucking flowers are ab-
sent, viz. Neuroptera, Ichneumonide, Tipulidae, etc.; Sphegide and
Vespide are only met with sparingly. (2) Of the flies, Syrphida
_ form the great majority; they are fond of brilliant colours, and
are attracted by the bright yellow of the Ranunculus flowers,
(This love of colours is clearly expressed in their own colours, the
_ result of sexual selection.) (3) It is also owing to their bright
colour that the flowers are frequented by the beetle Cryptocephalus
sericeus, and that Anthaxia nitidula resorts to them for pairing.
In these and in many other beetles, as in the humble-bees, it
seems as if the habit of feeding on flowers had called out the
colour-sense and the taste for bright colours, and that sexual
selection had then been guided by this taste. (4) Bees occur
much more abundantly on flowers of Ranunculus than on the
Umbelliferze, because the former .are richer in both honey and
pollen. These flowers seem especially to meet the wants of the
genus Halictus, of which I have taken twelve species on them,
mostly in abundance. Besides the least specialised bees (Drosopis,
Halictus, Andrena) and the most specialised (Apis), intermediate
genera, such as Panurgus and Chelostoma, which are absent from
Umbellifera:, visit the flowers of Ranunculus.

78 THE FERTILISATION OF FLOWERS. [PART 11.

8. RANUNCULUS LANUGINOSUS, L., is precisely similar in the
arrangement of its flowers to the three last-named species: but
growing in woods, where fewer flower-visiting insects occur, it is
frequented by a smaller number of species in spite of its larger
and more conspicuous flowers.

Visitors : A. Diptera—(a) Empide : (1) Empis livida, L., s. ; (b) Syrphide :
(2) species of Cheilosia, f.p., ab. ; (c) Muscide: (3) Anthomyia, f.p., very
ab. B. Coleoptera—(a) Nitidulide : (4) Meligethes zneus, F., ab. (I could
see distinctly with a lens how these small beetles gnawed the inner surface of
the petals and the stamens) ; (b) Dermestide : (5) Byturus fumatus, L., fip., ab.
C. Hymenoptera—(a) Tenthredinide: (6) Cephus pallipes, K1., very ab., fp.
and s., along with other species; (b) Apide: (7) Andrena eimsfecbaaae F. oO
cp. 3; (8) Chhelomtond florisomne, L. ¢,s. ; (9) Osmia fusca, Christ. 9, c.p., and
at the same turning round in the flower and emptying all the nectaries ; (10)
Bombus terrestris, L. 2, s. See also No. 590, 1, p. 51.

9. RANUNCULUS FicartA, L., also resembles 2. acris, 2. repens,
and &. bulbosus, but it blooms earlier when fewer flower-visiting
insects are abroad, a disadvantage which is perhaps partly
compensated for, by the insects having at that time fewer kinds of
flowers to choose from. At the beginning of the flowering period,
we find as in R. auricomus, many flowers with very few petals,
sometimes so few as two or three: later on the number increases
to eight or even eleven, and they expand in the sunshine to a golden
star 20 to 25 mm, in diameter.

Visitors: A. Diptera—(a) Syrphide ;: (1) Brachypalpus valgus, Pz., fp. ;.

(b) Muscide: (2) Sepsis, ab.; (3) Anthomyia radicum, L., very ab. ; (4)
Scatophaga merdaria, F. B. Hymenoptera—Apide: (5) Apis mellifica, L.,
S,s. and fp. ab.; (6) Andrena Gwynana, K. 9, ¢.p.; (7) A. albicans, K..
? d, cp. ands.; (8) A. parvula, K. ?,s.; (9) Halictus cylindricus, F. 9, s. ;
(10) H. albipes, F. 9, 8.; (11) H. lucidus, Schenck, ?,s.; (12) H. nitidius-
culus, K. 9,8. ©. Coleoptera—(13) Meligethes, ab., s., fp., and gnawing the
petals, D, Thysanoptera—(14) Thrips, very ab. Seealso No. 590, 1., pp. 51, 52.

10. RANUNCULUS AURICOMUS, L.—The flowers of this species
exhibit in their petals a great variety of forms of nectary, which
are very remarkable and help us to explain the various nectaries
of different Ranunculacez.

The corolla is seldom regular, but as a rule, some or even all
of the petals are more or less stunted or even absent, and the
sepals, with their bright yellow limb, take the place of petals
partly or completely. The honey-glands at the base of the petals
are subject to the following modifications, In the most perfect
petals (1 and 2, Fig. 26) the inner side of the triangular claw has

|

parrin.) = THE MECHANISMS OF FLOWERS. 79

usually a thickened border on either side: and these borders fuse
below, and at their junction form a little pit which secretes honey.
Some perfectly formed petals occur, however, in which the honey
is secreted not by this hollow, but by two smaller pits which stand
_ to the right and left, on the broader thickened margins (3, Fig. 26).
In very stunted petals (5 to 7 mm. long, and 3 to 4 mm. broad,)
_ there is developed upon the inner side of the base a smaller
lamina, which is fused with the larger for the space of 2 to 3 mm.,
_and has a free portion 1 to3 mm. long. Between the two lamin,
_ two honey-canals, separated by a fold, are deeply sunk (7, 8,
_ Fig. 26). Such petals have a striking resemblance to those of

, Fic, 26.
; -1~8.—Petals of Ranunculus auricomus. 9.—Petal of EHranthis hiemalis. n, nectary.

{ Biranthis hiemalis, Between these three varieties we find various,
often unsymmetrical, intermediate forms, (4, 5, 6, Fig. 26) in which
‘sometimes no honey is secreted (4, 5).

After completion of my manuscript I found (April 5 and 20, 1872) the
_ following insects in flowers of R. auricomus: A. Hymenoptera—(a) Apide :
(1) Andrena parvula, K. 9, ¢.p. ; (2) A. fulvescens, Sm. ¢,s. ; (3) Halictus cylin-
_ dricus, Bit: 0.7K $48) Formicide: (4) an undetermined sp., licking honey.
Bz Diptera—(a) Syrphide: (5) Pipizella virens, F., fp. ; (6) Cheilosia ver-
_ nalis, Fallen, f.p.; (6) Muscide: (7) Anthomyia shia, Mgn. @ 6, very
' ab., but so wild that I could not see what it was doing ; (8) Scatophaga mer-
- daria F., s. and fp. C. Thysanoptera—(9) Thrips, ab. Ants and Thrips
_ were observed in the flowers by Sprengel. See also No. 590, 1., p. 52.

Ii. CaLttHa patustris, L.—The honey is secreted by two
_ shallow depressions on the sides of each carpel, bounded by a slight
fold. It is so abundant that the drops secreted by the adjacent
sides of two neighbouring carpels often flow together into a large
_ drop filling up the cleft between. Anthers and stigmas ripen

80 THE FERTILISATION OF FLOWERS. [PART III.

simultaneously, but cross-fertilisation is favoured by the fact that,
as in Ranunculus, the anthers open outwards, and the outermost
are the first to dehisce. Self-fertilisation as in
Ranunculus is still possible. The very con-
spicuous golden-yellow flowers, which expand
to a diameter of more than 40 mm., are visited
in sunny weather by very numerous insects, of
comparatively few species owing to the early
time of year.

A. Diptera—(a) Stratiomyide : (1) Odontomyia ‘ar-
gentata, F.; (b) Syrphide: (2) Cheilosia sp., fp. ;
Caliha palustris, L. (3) Ascia podagrica, B., fp. ; (4) Rhingia rostrata, L,
st, stigma: n, nectary, /P-3 (5) Eristalis intricarius, L. (these handsome flies
bearingadropofhoney. displayed clearly their taste for bright colours ; they
hovered over the yellow flowers as the males of Eristalis
hover over the females, then suddenly settled to suck honey or feed on
pollen, and again flew off abruptly to another flower to repeat the same
actions) ; (c) Muscide: (6) Scatophaga merdaria, F., f.p.; (7) Anthomyia,
very ab., f.p. B. Coleoptera—WNitidulide : (8) Meligethes, very ab., s. and f.p.
C. Hymenoptera—Apide: (9) Andrena albicans, K. ¢, 8; (10) Osmia rufa,
L. ¢, s.; (11) Bombus terrestris, L. 9, making the circuit of each flower,
and licking the drops of honey from every carpel ; (12) Apis mellifica, L. $,
in hundreds, collecting pollen, and only sucking honey to aid in storing the
pollen. See also No. 590, 1., p. 52; No. 609, pp. 135, 136.

Trollius ewropeus, L., is homogamous. The stigmas are over-
topped by the anthers and are dusted regularly with their pollen,
which is probably outstripped in its action by pollen brought from
other flowers (609).

12. ERANTHIS HIEMALIS, Salisb.—This, the earliest of all
the Ranunculacez here considered, exhibits regularly in its petals
the same conversion into little pockets for honey that our earliest
species of Ranunculus, R. awricomus, displays occasionally. Its
calyx has completely assumed the function of rendering the flower
conspicuous, as do the sepals of 2. awricomus to a modified extent.
In other respects the arrangement of its flower agrees with those
last described.

On February 26, 1871, I saw the following insects on flowers of
E. hiemalis in my garden, during bright sunshine.

A. Diptera—Muscide : (1) Pollenia rudis, F., stroking petals, anthers, and
sometimes stigmas, with the end-flaps of its proboscis, but finally thrusting its
proboscis into the nectaries ; (2) Musca domestica, L., ditto ; (3) Sepsis, busy
about the anthers. B. Hymenoptera—Apide: (4) Apis mellifica, L. §, s.
and f.p., in great numbers, stfficient to fertilise all the flowers.

rarrim] THE MECHANISMS OF FLOWERS. 81

In many seasons with less favourable weather I have found
LE. hiemalis (which I have immediately in front of my window,
and can easily watch) not visited by insects at all, and yet bearing
fruit, but more sparingly than when insect-visits have taken place.
The reason of the smaller number of seeds is that, as in Ranun-
culus and Caltha, self-fertilisation can only take place to a limited
extent: for when I fertilised in my room, one flower with its own,
and another with extraneous pollen, both produced seeds in equal

abundance.

f The species of Helleborus are proterogynous, according to
_ Hildebrand (351).

| Nigella arvensis, L.—The ectmenidooti flowers of this plant
_ are provided with nectaries covered by movable lids, and are
_ fertilised by bees. They have been fully described by Sprengel.

4 Nigella damascena, L., is visited by Ceratina callosa, F. 3, and
Prosopis signata, Nyl. g (Apide) (590, 1).

13. AQUILEGIA VULGARIS, L.—The five sepals of the pendulous
flower form broad blue expansions, which help to render it
conspicuous. Each of the five petals is hollowed out from its
insertion upwards to form a hollow spur 15 to 22 mm. long, whose
i cup-shaped mouth is wide enough to admit the head of a humble-
__ bee, and whose narrow tubular part curves inwards and downwards
at its upper end. In this curved part is contained the honey,
_ which is secreted by a fleshy thickening in the extreme point of
_ the spur. Owing to its curvature the point of the spur is only
_ 10 to17 mm. above the insertion of the petal. To reach the honey
ina legitimate way, the bees hang on to the flowers below, grasping
the base of the spur with their forelegs, and holding on with their
_ mid and hindlegs to the column formed of the stamens and
_ carpels, which projects perpendicularly or obliquely downwards

from the centre of the flower; the head, meanwhile, is introduced

_ into the aperture of the spur, whose outer wall its upper surface
_ touches, and the end of the proboscis follows the curvature of the
_ spur. Since bees very ‘easily bend the end of their proboscis
_ downwards, but scarcely bend it voluntarily in the opposite direction,
_ the position just described is the only one suitable for them to
reach the honey. This position entails that in younger flowers
_ the hinder and lower surface of the bee’s body touch the anthers,
_ which closely surround the carpels and which are covered on their

1 See also Kerner, No. 386, p. 101, for an account of the pits in NV, sativa and
WN. elata.

G

82 THE FERTILISATION OF FLOWERS. [PART IIL.

outer side with pollen; while in older flowers the same parts
come in contact with the carpels which have elongated and spread —
their stigmas more widely apart. Cross-fertilisation is the inevitable
result. Thus the Columbine is admirably adapted for fertilisation
by humble-bees: but to reach the honey they must have a
proboscis at least 10 to 17 mm. long, even supposing that they
stick their heads fully into the mouth of the spur and so shorten
the passage by about 5 mm, This fully explains the actions of the
insects that I have observed on this flower. Bombus hortorwm,
L. 2 (with a proboscis 19 to 21 mm. long), is the only insect
that I have found very abundant on it; B. agrorum, F. 2 (with a
proboscis 12 to 15 mm. long) is found much more rarely, sucking
the flowers in the regular way and accomplishing cross-fertilisation.
I saw B. terrestris, L. 2 (with a proboscis 7 to 9 mm. long), fly on to
the upper surface of a flower, and lick over the base of the sepals,
and on finding nothing there, creep to the lower surface, and thrust its
head into the spur. Then it again crawled on to the upper surface,
and again licked fruitlessly the base of the sepals; and finally,
biting a hole in the spur at the curved part, it introduced its
proboscis and plundered the honey. Without further consideration
it proceeded to secure the honey of the other petals and of other
flowers in the same manner.. The numerous other individuals of
B. terrestris, L. 9, which I before and afterwards observed thus
perforating the spur, had probably first learned by trial how the
honey might be won.

I have often seen #. terrestris bite through the spurs of still
unopened flowers, and so forestall all legitimate visitors. The
hive-bee also, as Sprengel noticed, bites through the spur at the
bend and steals the honey: it often takes advantage of the holes
made by B. terrestris. |

I have seen smaller bees, Halictus Smeathmanellus, K. 2, and
HT. leucozonius, Schr. ? , collecting pollen on these flowers, which they
would naturally fertilise by doing so.

On a double garden-variety of the Columbine, in which seve-
ral spurs are placed one within another, I noticed a hive-bee
thrusting its head in the regular manner into the inner spur; and
I could see, through the transparent flower, the tongue stretched
— out to its fullest extent without reaching the honey.

In default of insect-visits, self-fertilisation must easily take
place, owing to the position of the parts of the flower.

Aquilegia atrata, Koch, is also proterandrous, and visited by
humble-bees (609, p. 137).

PART LIT. | THE MECHANISMS OF FLOWERS. 83

14, DELPHINIUM ELATUM, L.—This common garden plant is
marked off by the unusual function of the two whorls of the
perianth from most other plants, and in part even from other
species of larkspur; while it agrees with the latter in the early
development of the stamens and in the peculiar movements of
_ the stamens and stigmas.

Fig. 28.—Delphinium elatum, L.

1.— Young flower after removal of the calyx, seen from before. .

2.—The petals in their natural position, seen obliquely from before and below.

3.—Young flower after removal of the right half of the calyx.

4.—Older flower after removal of the calyx, seen from before.

5.—The sume flower as 3, after the right half of the corolla also has been removed.

aa, the two upper petals, which are prolonged backwards into two spurs, which secrete and

contain honey, and which in front form an entrance for the bee’s proboscis ; a*, their bases ; b b,
_ the two inferior petals, whose closely approximated surfaces bound the entrance for the bee’s

proboscis below—on their upper surfaces, each has a tuft of yellow hairs to serve as a path-finder,

_ while their peduncles (b’,2 stand so far apart that in the first stage the anthers, in the second the
stigmas, appear between them (at b*, 2) in the path of the insect’s re c, anthers whichhave

_dehisced, placed in the way of the insect’s proboscis ; d, anthers which have not yet dehisced, bent

downwards, covering the female organs; e, base of the stamens and carpels, which have been

removed ; f, withered stamens bent downwards ; g, ovaries ; h, stigmas which have ss themselves

in the same spot that the dehiscent anthers occupied in the first stage; i, left half of the upper

_ sepal. prolonged backwards into a long sheath for the spur (#’); i, left lateral sepal; 1, left inferior

a

3 and 5, natural size; 1, 2, and 4, enlarged,

The five large, blue, expanded sepals make the flowers visible
_ from far off to humble-bees, and serve the purpose of a corolla.
_ The hollow spur of the uppermost sepal neither secretes nor
contains honey. Its peculiar rough and crumpled wall serves
| rather as a cover for the organs which secrete and conceal the
honey, which without it would be exposed to the rain; and also
G 2

84 THE FERTILISATION OF FLOWERS. [PART III.

it forces the humble-bees to suck the honey by the way that alone
leads to fertilisation.

The two upper petals serve a very different purpose. In each the

hollow pointed end of the spur (a?, 3, 5), which is directed back-
wards and is inclosed in the hollow sepaline spur, secretes honey
and becomes so full of it that part rises into the wide, half-conical *
part of the spur which is open on the inner side (@’, 5). When
both petals lie close to one another, they form together a hollow
cone, which splits at the end into two points filled with honey,
and guides the insect’s proboscis, if long enough, safely to the
honey, while by its length it prohibits the access of insects with
shorter tongues. The anterior portions of the same petals
produce the upper part of this hollow cone further forwards, and
serve to give the bee’s proboscis a convenient entrance and more
certain path to the honey. Since these anterior portions of the
upper petals separate easily on slight pressure from within, the
whole head of a humble-bee may be thrust in between them,
whereby the distance to the honey is shortened by 6 to7 mm. The
length of the hollow cone from its entrance to the anterior end of
the honey-bearing prolongation is about 20 mm., and to the apex of
the latter 26 to 28 mm.; so that, when the whole bee’s head is
thrust into the aperture, a proboscis 13 to 14 mm. long is needed
to reach the honey, and one 19 to 22 mm. long to suck it all up.
Hence, of all our native bees, Anthophora pilipes, F., and Bonbus
hortorum, L., can alone exhaust the honey.

The two lower petals are of service in several ways. Their
anterior surfaces point by bundles of upright yellow hairs towards
the entrance to the honey, that is to say, they serve as path-
finders; and as they stand close together and bound this entrance
below, they leave the bee no choice but to thrust its proboscis into
the only proper place, viz., the mterval between the two pairs of
petals. Those parts of them immediately behind the entrance to
the tube stand, on the other hand, so widely apart (*, 2) that they
leave free space for the stamens and for the carpels (after the
stamens have withered and bent back) to erect themselves in that
part of the hollow cone lying close behind the entrance, where they
inevitably come in contact with the under surface of the body and
head of the bee.

With sufficient insect visits, which this handsome plant never fails
to receive, cross-fertilisation is completely insured by the proter-
androus dichogamy, and by the movements of stamens and earpels

} 7.e. forming the longitudinal half section of a cone, —

parti] THE MECHANISMS OF FLOWERS. 85

which are so completely in relation to the movements of the bee’s
head. The stamens in the unripe condition are bent down, when
they dehisce they stand upright in the path of the bee’s head,
and when they are withered they sink completely down. The
_ carpels erect themselves after the withering of the last of the stamens,
_ and their stigmas then stand in the way of the bee’s head. Self-
fertilisation cannot take place in absence of insects. Of the two
native bees whose proboscides are of sufficient length to suck the
honey of this flower thoroughly, Anthophora pilipes has finished its
period of flight and has disappeared when D. elatum flowers. B.
hortorum therefore remains as the only indigenous bee fitted for
sucking up the honey of Delphiniwm, and it is in fact found in
great abundance on the flower. Many of our other species of bees
are well fitted for sucking a portion of the honey, but I have never
seen any of them, or any other species of insect, sucking on D. clatum.
At Strassburg, D. elatuwm is visited also by Anthophora personata,
IIL. (590, 1).

Delphinium Staphysagria, L., described and figured by Hilde-
brand (356, p. 473) agrees in most points of its floral arrangement
with D, elatwm, and is, likewise fertilised by humble-bees.

15. DELPHINIUM Conso.ipA, L., differs in the arrangement of its
flower from D. elatwm chiefly by the coalescence of the four petals
_ into a single piece, which leads to the following modifications. The
_ two upper petals unite by means of their backward directed processes
into a single spur, the pointed end of which secretes and contains
_ the honey ; their expanded portions, which are turned forward, also
_ coalesce lengthwise with one another, and therefore cannot be thrust
apart on the entrance of the bee’s head; but in conjunction
with the lower petals they form a sheath which is well adapted to
receive the bee’s head, and is only open below. | Here in the first
_ stage of flowering it presents the anthers, and in the second the
_ stigmas, for contact with the under surface of the bee’s head. The
lower petals, which thus form the side walls of the sheath or tube,
unite with the upper ones, but not with one another, and yield
laterally when the bee’s head is thrust in. Path-finders and
a lower boundary of the entrance to the spur are wanting
here.

Since the cycle of development and movement of stamens and
anthers agrees with that in D. elatum, cross-fertilisation is in like
manner insured on the occurrence of insect-visits; and similarly,
if they fail to occur, self-fertilisation is impossible.

86 THE FERTILISATION OF FLOWERS. [PARY III.

In July, 1868, I assured myself of the actual certainty of cross-
fertilisation by direct observation. I saw, in Thuringia, upon a
field covered with wild larkspur in flower, numerous examples of
Bombus hortorum, L. 9 and §, sucking at the flowers of this species
with such diligence that certainly no flower in its. second period
can have escaped being fertilised.

Since the length of the spur is about 15 mm. from its insertion, to
which must be added the wide entrance, 7 mm. long, a proboscis
fully 15 mm. long is needed to suck the honey in the normal way.
Besides Bombus hortorum, L. (17 to 21), B. agrorum, F. (10 to
15), B. fragrans, K. (15) and B. senilis, Sm. (14 to 15), some
species of Anthophora, viz., A. wstivalis Pz. (15), A. retusa, L. (16
to 17), and -A. pilipes, F, (19 to 21), are all fitted for sucking the
honey; but all must do so with greater loss of time, through
having to force the head deep into the entrance to the spur,
except A. pilipes, whose season is over when Delphinium comes
into flower. Bombus hortorum seems thus to be the only species
which is well adapted for the flower; but the diligence of
this one species compensates the plant for the exclusion of
all other insects. I have noticed Satyrus and species of Hesperia
sucking at the flowers, and sinking their thin proboscides into
the spur, but apparently they did not touch the anthers or
stigmas. |

Dr. Ogle gives in the Popular Science Review (631) a description
of a species of larkspur which differs from those here described in
that the honey secreted by the upper petals is contained in the
spur of the posterior sepal. I unfortunately cannot determine
which species of Delphinium is referred to as “the blue larkspur
of our gardens,”

Delphinium Ajacis, L., described by Sprengel, agrees in most
points with D. Consolida, and is likewise fertilised by humble-
bees. .

16. AconttuM NAPELLUs, L.—This plant is distributed through-
out the Alps, especially about the Sennerei. It has distinctly proter-
androus flowers, which are visited by humble-bees, as Sprengel long
ago observed. The two posterior sepals cohere to form a helmet-
shaped structure, which shelters the anthers and nectaries; the
two lateral sepals give foothold to the mid and hindlegs of
humble-bees ; all four play, in addition, the part of petals, making
the flower conspicuous by their blue colour, Of the four petals,
the two anterior help to close in the essential organs laterally;

-

PART I11.] THE MECHANISMS OF FLOWERS. 87

the two posterior are transformed into long-stalked nectaries, only
accessible conveniently to humble-bees. The well-marked pro-
terandry insures cross-fertilisation if humble-bees visit the flower,
and, as a rule, prevents self-fertilisation in absence of insects

(609).

17. Aconitum Lycoctonum, L.—The structure of the flower
is for the most part similar to that of A. Napellus, but the
helmet and the nectaries are so exceedingly long that only an insect
_ whose proboscis is very exceptionally long can reach the honey.
In point of fact, in the plains (in a wood at Thiile, near Paderborn)
I have found it visited exclusively by Bombus hortorum, L. @
_ (proboscis, 21 mm.), whose proboscis is the longest among lowland

Fia. 29.—Aconitum Napellus, L.

| A.—Flower in first (male) stage. The anthers have become erect, have dehisced, and are coated
_ with white pollen. nes
e | B.—The same flower in side view. a, a hole bitten by Bombus mastrucatus.
C.—Ditto, in longitudinal section.
D.—Essential organs in the first (male) stage. a’, anther bent backwards and not yet dehisced ;
_ a’, ditto, becoming erect ; a3, ditto, erect, dehisced, and covered with pollen; a‘, ditto, empty,
and bending backwards ; a5, ditto, empty, and bent quite backwards,
E.—Essential organs in the second (female) stage,
A—C, nat. size; D, B, x 2.

__ humble-bees, and on the Alps exclusively by B. opulentus, Gerst.
(22 mm.), whose proboscis is the longest among Alpine species.
B. opulentus has not as yet been observed upon any other flower,
either by Prof. Gerstiicker, who discovered and described it, or by

| _ myself (609).

88 THE FERTILISATION OF FLOWERS. | PART ILI.

Acumitum septentrvonale, Koell., has likewise proterandrous flowers,
figured by Axell (17).
Peonia Moutan, Sims., according to Delpino, is regularly fertilised
by Cetonize, which lick the fleshy disk around the carpels.

REVIEW OF THE RANUNCULACEA,

While the Umbelliferze form a numerous family where a certain
sum of adaptations insuring cross-fertilisation has been inherited
from ancestral forms and descends through all branches of the
family, in Ranwnewlacee, on the other hand, we have a family
whose separate divisions have developed for themselves quite
distinct advantageous modifications. We see conspicuousness
insured in Ranunculus by the petals; by the sepals in Hranthis,
Helleborus, Anemone, Caltha ; by both together in Aguwilegia and
Delphinium ; by the stamens in Thalictrum. Honey is wanting
in Clematis, Thalictrum, and Anemone: it is secreted by the sepals
in certain Peonies ; by the petals in Ranunculus, Hranthis, Helle-
borus, Nigella, Aquilegia, Delphinium, Aconitum ; by the filaments in
Atragene ; by the anthers in Pulsatila ; by the carpels in Caltha:
it is sometimes easily accessible, at other times more or less
deeply hidden. Such a variety of different adaptations is explained
by supposing many different ways of attaining perfection to have
been available for the plants when their flowers had not yet been
modified so far as to insure cross-fertilisation.

An easily accessible situation of the honey in simple, regular
flowers carried with it the advantage of abundant insect-visits ; but:
at the same time the objection that the visitors crept about the
flowers in various ways, often accomplishing only self-fertilisation,
often leaving the flower still unfertilised. Honey more deeply
placed, brought the disadvantage that a great multitude of
insects were shut out; but this advantage, that the bees with long
proboscides had to move in a particular way to reach the honey,
and so stamens and pistils could in a simple manner be arranged
so as to render cross-fertilisation inevitable. We find self-fer-
tilisation possible in all regular Ranunculaceous flowers with
easily accessible honey; but prohibited by well-marked proter-
andry in all those with deeply situated honey, whether regular, as

1 Lists of visitors to the following additional species are given in my Weitere
Beobachtungen, pt. i.: Clematis Vitalba, \., Thalictrum minus, L., Hepatica triloba,
Gil., Pulsatilla vulgaris, Mill., Anemone silvestris, L., A. ranunculoides, L., Adonis
vernalis, L., Myosurus minimus, L., Actea spicata, L.

parrut] § THE MECHANISMS OF FLOWERS. - 89

_ Agquilegia, or irregular, as Delphinium and Aconitum ; and so we
. may conclude that in the Ranunculacee the certainty of cross-
fertilisation has been more effectually attained by flowers being
_ specially adapted for a few species of bees, than by attracting a
great multitude of different guests. We must however beware
_of taking this as a general conclusion; for in Umbelliferze the still
more open situation of the honey, aided by the massing together
of many flowers, insures cross-fertilisation, through proterandrous
dichogamy, even so far as to permit loss of the power of self-
- fertilisation.
Only those Ranunculacer seem to me to be adorned with
- blue colours which are cross-fertilised by bees, eg. Hepatica
_ triloba, which is fertilised by pollen-collecting bees, or the
species of <Aquilegia, Aconitum, and Delphinium, which seem
adapted for humble-bees by the whole structure of their flowers.
The easy transition in Hepaticas from blue to pink, and even to
white, may be most easily explained as a case of reversion (vide

also 6009).
Orv, CALYCANTHACEZ.

Chimonanthus fragrans, Lind., has, according to Hildebrand, pro-
_ terogynous flowers. In the first stage, the still immature stamens
are bent away from the stigmas, which receive pollen from other
flowers; in the second stage, the ripe stamens arch over the stig-
-mas and prevent access to them (356, p. 491). Delpino saw the
_ flowers visited by an Osmia at Florence (177, p. 59).
Calycanthus floridus, L., according to Delpino, is markedly pro-
terogynous with short-lived stigmas; it is devoid of honey, and
is probably fertilised by Cetoniw (177, p. 58).

Orv, MAGNOLIACE ZZ.

5 Lilicium religiosum has in the middle of the flower, according
_ to Delpino, little papillae, very rich in honey and resembling
_ stigmatic papillee, which probably serve as bait for a Cetonia (567).
i Magnolia Yulan, Desf., is proterogynous. According to Delpino,
bees fly into the upright flowers, and in the first period are neither
able to creep up the smooth petals, nor to rise in flight from the

| _ short pistil which stands erect in the centre of the flower. They
_ remain prisoners until in the second period the petals spread out,

5 and the bees then fly away, dusted with pollen, to another aver
1 (178, 360, p. 593).

90 -THE FERTILISATION OF FLOWERS. [PART III. ,

Magnolia grandiflora, L.—Rose-beetles (Cetonia aurata and
stictica) resort to the scarce opened flowers. They find shelter
beneath the three inner petals, which form a vault over the stigmas,
warmth which is so considerable that it is sensible to the touch,
and honey lying on and between the stigmas. They remain in this
pleasant refuge, until the sepals or petals fall off, and then, laden
with pollen, they fly away to other flowers. In the first period only
stigmas, and in the second only anthers, are mature, so selffer-
tilisation is impossible, and the beetles, flying from flower to flower,
accomplish cross-fertilisation regularly (178, 360, p. 594).

Orpd. ANONACE &.

Asimina triloba, Dunab., is proterogynous with short-lived
stigmas. In the middle of the bell-shaped, pendulous flower
rises a hemispherical mass of stamens, from the midst of which
some stigmas protrude. The three inner petals, which secrete
honey at their base, lie in the first period close upon the stamens ;

they compel the flies which visit the flower to touch the already —

mature stigmas on their way to the honey. Cross-fertilisation is
effected if the flies come bringing pollen from an older flower.
Delpino counted seven species of Diptera visiting the plant
(178, p. 231; 360, p. 672).

Orv. BERBERIDEL.

18. BERBERIS VULGARIS, L._—Sprengel describes and figures the

flowers as hanging down vertically. This, however, is seldom the.

case ; most are horizontal or inclined obliquely downwards. They
are not fully protected by their position from the weather, but the
three inner sepals and the six petals, which as well as the sepals
are curled inwards at their points, protect the stamens together
with the honey-glands and honey from rain. The three inner
sepals make the flower conspicuous by their yellow colour, and
the petals completely embrace the stamens so long as the latter
are undisturbed. The honey-glands are two thick, oval, fleshy,
orange bodies, lying quite close together on the inner side and
near the base of each petal. The filaments are so much expanded
as to touch each other at the base; before being irritated they are
bent so far back that each is in contact with the part of a petal
below the honey-glands, and also with the adjacent halves of the
two honey-glands. There is thus no room for the honey to
accumulate between petals and stamens, but it must flow into

PART Int | THE MECHANISMS OF FLOWERS. 91

the angles between stamens and ovary, which are always found to
be quite full of honey. Every insect-visitor must thrust its
_ proboscis into one of these angles; and in doing so it causes the
two stamens which the base of its proboscis touches to spring
inwards towards the pistil, and to dust with pollen one side of its
head, which is thus shut in between two anthers and the stigma.
The stigma is. represented by the papillose and viscid edge of a
dise which surmounts the ovary and occupies the middle of the
flower ; one side of the insect’s head, opposite to that touched by
the stamen, comes in contact with the stigma. The insect usually
flies away at once after the first drop of honey on being struck by
_ the stamen, and as it thrusts its head or proboscis into the flower
in many different ways as the different positions of the flower

“a

Fia. 30.— Berberis vulgaris, L.

1
a
. 1.—Flower seen from above. a, the three inner. larger sepals, which by their size and colour play
_ the part of a corolla; 6b, outer, b’, inner petals, ; ¢, nectaries; d, filaments ; e, stigma,
ig 2.—Position of the stamen after springing inwards.
8.— Petal with its two thick fleshy, orange nectaries.
4—7.—Stamens in various stages of dehiscence, erection, and rotation of the anther-valves. 4,
_ stamen with the anther-valves still closed ; 5, the valve of the right anther-lobe has opened, and is
beginning to move upwards, with the pollen attached to it; 6, both valves have nearly completed
_ their movement of rotation, the pollen masses are directed towards the right and left ; 7, both valves
_ have turned in such a way that the pollen-masses face the centre of the flower, and touch one
another with their adjacent edges ; 7b, ditto, inner aspect.

_ require, now under now over the stigma, now to the right, now to
the left, its head must soon be dusted all round with pollen, and it
| must fertilise every succeeding flower that it visits, It can only
| _ accomplish self-fertilisation if in the same flower it plunges its
| proboscis first to the right and then to the left, or first over and
if then under the stigma. In the case of the hive-bee I have
Bpeistinctly observed that it seldom proceeds in this manner, It
never makes a circuit of the flower, for it flies away and seeks

92 THE FERTILISATION OF FLOWERS. [parr ut.

another as soon as it is struck by the stamens whose bases it has
touched, and it rarely thrusts its proboscis a second time into the
same flower. When it plants its forelegs upon the flower, it
usually causes the greater number of the stamens to close in upon
the pistil.

I have often seen humble-bees, on the other hand, thrust their
proboscides again and again into the same flower.

It is clear from the above that Sprengel is in error when he
explains the flower of the barberry as adapted for self-fertilisation ;
and this is proved most unequivocally by a closer examination of
the movement of the anthers upon irritation.

Before the flower opens the anthers stand on a level with the
stigma; they are closely applied to the stigma in the bud, but in
the opening flower they are bent as far backwards as the sur-
rounding petals allow. As soon as the petals begin to diverge,
the anthers dehisce, the lid flying up and remaining attached only
to the extreme end of the connective, which is here at its broadest.
The anther-lid carries with it almost all the pollen, and after rising
to its full height it turns that side which bears the pollen inwards
towards the middle of the flower. If the stamens are now touched
at their bases and made to move inwards, the masses of pollen do
not come on a level with the stigma, but stand above it; so that
even those parts of the masses of pollen which do not touch the
insect, excluding some little scattered particles, do not come in
contact with the stigma: the insect’s head or proboscis, however,
in being drawn back and rubbed against the masses of pollen
gets dusted with pollen just in those parts which will come in
contact with the stigma in other flowers. 7

If insect-visits altogether fail, then, as the flowers wither, the
masses of pollen come of themselves into contact with the stigma
through the bending inwards of the anthers. I have observed this
in specimens kept in my room, but I cannot say what results follow
self-fertilisation at such a late period.

Visitors: A. Diptera—(a) Syrphide : (1) Helophilus floreus, L., very ab. ;
(2) H. pendulus, L. ; (3) Eristalis tenax, L., ab. ; (4) E. arbustorum, L. ; (5)
E. nemorum, L.; (6) Rhingia rostrata, L., ab. ; (b) Muscidae: (7) Onesia
floralis, R. D.; (8) O. sepulcralis, Mgn. ; (9) O. cognata, Mgn. ; (10) Musca
domestica, L.; (11) M. corvina, F. B. Hymenoptera—(a) Apide: (12)
Apis mellifica, L. §, ab.; (13) Bombus terrestris, L. 2 ; (14) B. pratorum,
L. 9 ; (15) Andrena Trimmerana, K. 9; (16) A, helvola, L. ¢; (17) A.
fulvicrus, K. ¢, ab.; (18) A. fulva, Schrk. 9, moderately ab.; (19) A.
albicans, K. 9; (20) A. Smithella, K. 9; (21) Halictus rubicundus, Chr. ? ,

ora

yarrun] THE MECHANISMS OF FLOWERS. 93

(b) Vespide : (22) Vespa holsatica, F. 9; (23) V. rufa, L. §. C. Coleop-
tera—(a) Dermestide: (24) Attagenus pellio, L.; (b) Coccinellide: (25)
Coccinella 14punctata, L. All were sucking honey ; Bombus pratorum and
Andrena fulva were also collecting pollen, See also 590, 1., and 609.

Orv, NYMPH MACE &,

19. NupHAR LUTEUM, Smith.—The sepals, as Sprengel clearly

showed, have, by their increased size and the yellow colour of their

upper surface, taken on the function of a corolla: the under side

of the petals secretes honey. Sprengel found only small beetles of
the genus Meligethes in the flowers: I have seen besides Meligethes
' various flies and other small beetles creeping about the flowers and
flying from one to another; they effected self-fertilisation and
_ cross-fertilisation indifferently. I was only able to catch Onesia
floralis, R.D. (Muscidae), and Donacia dentata, Hoppe (Chryso-
_ melide); both were richly dusted with pollen.

Nymphea alba, L., and Victoria regia, Lind., are, in Delpino’s
opinion, fertilised by Cetoniw and Glaphyride. See also No. 775.

Orv, PAPAVERACE ZL,

20. PAPAVER Rua@as, L.—The numerous anthers stand close

round the stigma, and dehisce before the opening of the flower.

They cover themselves with pollen, part of which reaches the

_ lower part of the stigmatic lobes, while the higher central parts
of the stigmatic lobes protrude free from pollen. Its flowers
' contain no honey, and are therefore visited solely by pollen-seeking
insects, which find the broad stigmatic surface the most convenient
| place on which to alight. They necessarily accomplish cross-
_ fertilisation if they have come from another flower, and this

cross-fertilisation probably prevails in its action over the self-

| fertilisation which has already taken place.

Visitors: A. Hymenoptera—Apide: (1) Halictus sexnotatus, K. 2, very

' ab, ; (2) H. flavipes, F. 9, ab; (3) H. longulus, Smith, 9; (4) H. cylindri-
_ cus, K. 9; (5) H. maculatus, Sm. 2; (6) Andrena dorsata, K. 2, ab. ; (7) A.

_ tulvicrus, K. ? ; all collecting pollen, and dusted thickly with it. B. Diptera
| —Syrphide ; (8) Cheilosia, fp. C. Coleoptera—Nitidulide : (9) Meligethes,

very ab., fp. D. Orthoptera—(10) Forficula auricularia, L., both larvee and
perfect insects hiding in the base of the flower, See also No. 590, I.

Whether, in default of insect-visits, the self-fertilisation which
inevitably takes place leads to development has still to be decided
by experiment, Probably it does so, as Hildebrand has found that

94 THE FERTILISATION OF FLOWERS. [PART IIT.

Argemone ochroleuca, Glaucitum luteum, and Papaver argemonoides
all bear seed when fertilised with their own. pollen (358).

Papaver Argemone, L.i—The flower has exactly the same
structure as P. Rhwas, the only difference being that a smaller
part of the stigmatic lobes is exposed to self-fertilisation.

In Papaver dubium, L., the stigma stands some millimeters
above the level of the anthers, so that self-fertilisation can only
take place in a down-turned position of the flower. Perhaps the
fact that this species is much rarer than the others (in Westphalia,
at least) is due to the impossibility of self-fertilisation.

Papaver alpinum, L., is homogamous, and (when cultivated)
is sterile to its own pollen. The flowers are devoid of honey, and
are visited by pollen-feeding Diptera (609).

Papaver hybridum, L., has cleistogamic flowers, at least when
under cultivation (369). |

21, CHELIDONIUM MAJUS, L.—In sunny weather the anthers
dehisce laterally as the flower opens, and the stigma is developed
at the same time. Since the stigma somewhat overtops the anthers,
insects alighting in the middle of the flower touch the stigma first
and accomplish cross-fertilisation, while those which alight on a
petal and crawl inwards may accomplish either cross- or self-
fertilisation. In dull weather the flowers remain closed longer,
and the stamens dehisce within the as yet unopened flower, causing
self-fertilisation.

The flowers contain no honey, and are visited and fertilised only
by pollen-seeking insects.

Visitors: A. Hymenoptera—Apide : (1) Bombus pratorum, L. § ; (2) B.
agrorum, F, §; (3) B. Rajellus, Ill. 9—/(all three alighted on the centre of
the flower and swept pollen in great haste with the tarsal brushes of the fore
and midlegs out of the anthers into the baskets on their ,hindlegs, and hardly
spent two to three seconds on the flower before passing to another ; they effect
cross-fertilisation regularly) ; (4) Halictus cylindricus, F. 2; (5) H. zonulus,
Sm. 9; (6) H. sexnotatus, K. 9; (7) H. sexstrigatus, Schenck, 9 —(these
small bees alight on the anthers and spend a much longer time on each flower,
passing round upon the anthers. They only come in contact with the stigmas
accidentally, and may effect self-fertilisation and cross-fertilisation indifferently).
B. Diptera—(a) Syrphide : (8) Syrphus balteatus, Deg. ; (9) 8. ribesii, L. ;
(10) Syritta pipiens, L.; (11) Ascia podagrica, F. ; (12) Rhingia rostrata,
L., all feeding on the pollen, and moving round the flower in the same way as
the species of Halictus ; (b) Empide : (13) Empislivida, L. See also No. 590, 1.

Eschscholtzia Californica, Chmss., furnishes an illustration of
varying capacity for self-fertilisation. My brother Fritz Miiller found

PART IIL, | THE MECHANISMS OF FLOWERS. 95

this species unfruitful in South Brazil, and Darwin found it fruitful
_ in England, when fertilised with its own pollen. Plants which Fritz
_ Miiller raised in South Brazil from seed sent from England by
_ Darwin yielded some seeds when fertilised with their own pollen,
_ but far fewer than in England. Hildebrand found this species not
absolutely barren, but very nearly so, when fertilised with its own

_ pollen (358).

Orv. FUMARIACE &.

_ Hypecoum procumbens, L.—In the bud, the two inner petals
receive all the pollen in two pockets developed upon their inner
_ surface, and these pockets close up before the development of the
stigma. On pressure from above, their edges separate and dust the
‘object pressing them with pollen. The stigmatic papillze do not
" attain’their full development until some time after the opening
- of the flower, and after the pistil has grown up above the level
- of the pollen-sacs, so that in each flower insects come in contact
| first with the stigma and then with the pollen. Cross-fertilisation
_ is insured (in case of insect-visits) first by proterandry, and secondly
_ by the projecting situation of the stigma (358).

} Hypecoum grandifiorum.—Hildebrand found that the flowers
_of this species were very nearly though not absolutely barren
when fertilised with their own pollen or with pollen from another
flower of the same plant (358).

«22, -DICLYTRA SPECTABILIS, D‘C.—The heart-shaped pendulous
+7 lowers contain honey in the two pouches at the base of the outer
_ semi-cordate petals. Each of these two petals incloses three
| stamens which follow the contour of its wall and then together
| form a channel leading from the middle of the flower to the honey.
; The exserted ends of the six stamens project straight downwards,
_ lying close together around the pistil, and being themselves sur-
2 rounded by the hood-like ends of the, two inner petals, which
_ cohere at the points.

Li Between the hood-shaped end of the inner petal and the curled
1 end of the outer one, there remains on the right and left a canal
leading to the honey. Ifa bee hanging from the flower thrusts its
| proboscis into one of the two canals, the lower surface of its
_ abdomen presses both the hood and the flexible stamens towards
_ the opposite side; and the stigma, which is at the end of a stiff
‘. ‘style and Pertork escapes being pushed aside, is rubbed by the

96 THE FERTILISATION OF FLOWERS. [PART III.

hairs on the lower surface of the bee’s body. When the bee flies
away the hood returns to its former position and again incloses the
stamens and pistil. At each visit this action is performed twice,
once on the right and once on the left, since there are two honey-
sacs and two canals leading to them.. Thus in young flowers the
pollen adhering to the stigma is brushed off on to the hairy body
of the bee, and in older flowers, which have been already robbed
of their own pollen, pollen from other flowers is brought and
applied to the stigma. Hildebrand saw humble-bees acting in the
manner described. Since the proboscides of our humble-bees vary
from 7 to 21 mm., and the canals leading to the honey in Dielytra
are 18 to 20 mm. long, the action of the different visitors deserves
closer examination. 3

I have only seen Bombus hortorum, L. 2 (20 to 21),and Anthophora
pilipes, F. 9 (19 to 20), both in fair abundance, sucking this flower in
the normal way: they sucked each flower twice, once on each side.
Bombus terrestris, L. 2, whose proboscis is only 7 to 9 mm. long,
climbs on to the upper part of the flower and bites a hole into
one of the honey-sacs; it tries to introduce its proboscis through

— - ©

"© ene Mise n> =;

the hole it has made, and if it does not at once succeed, it bites —

several times, and at-last succeeds in stealing the honey out of
both the pouches! I have seen Bombus pratorum, I. ? (11 to 12),
and B. Rajellus, Ill. (12 to 13), act in the same way. Osmia rufa,
L. 2 (9), Megachile centuncularis, L. 6 (6 to 7), and Apis mellifica,
L. & (6), often make use of the holes which humble-bees have
bitten, and which few flowers are free from.

The action of the hive-bee’on flowers of Diclytra convinced
me of the advantage that flowers derive from having convenient
landing-places for insects. If the bee tried to steal honey by means
of holes made by Bombus terrestris, it found no such resting-place,
but catching hold of the edge with some of its legs, it groped about
with the others on the smooth surface, and so stood insecure and
wasted much time.

Diclytra eximia, D.C.—The flower has been thoroughly described
and figured by Hildebrand (358). It resembles D. spectabilis, but
the space for the lateral bending of the hood is smaller and the
passage to the honey shorter.

In Dielytra cucullaria, D.C., the outer petals are provided with
long spurs and the honey is secreted by two long processes of the
middle stamens lodged in these spurs (358).

1 In North America, Diclytra Canadensis is bitten in the same way by the
short-lipped bee Bombus Virginieus, Oliv. (736).

ART IIL. | THE MECHANISMS OF FLOWERS. 97

23. CoRYDALIS CAVA, Schweigg. and Kért. The flower is
figured and described by Hildebrand (351, 358).

In contrast to the pendulous flowers of Diclytra and Adlumia,
which are symmetrical about two planes perpendicular to. one
- another, and permit a double motion of the hood, to right and left,
- we have in Corydalis cava horizontal flowers symmetrical about
one perpendicular plane, and whose hood can only be thrust by
insects in one direction, viz. downwards. The two outer petals,
_ which are here superior and inferior, have ceased to be symmetrical,
_ the upper one being produced into a long spur, curved downwards
at the end, and reaching some 12 mm. backwards over the flower-
stalk. In this spur is lodged a common prolongation of the upper
_ stamens, which secretes honey and extends as far as the curved part
of the spur.
ec The two inner petals stand at the sides, and are fused with the
upper petal at their bases; they are symmetrical, and unite at the
apex to form a hood. A bee, to reach the honey stored at the end
of the spur, must stand on the lower petal or on the hood, and
thrust its proboscis between the hood and the upper petal; in
doing this, it presses down the hood, and rubs the under surface
of its head on the stigma, which, being placed on a stiff pistil, does
not bend downwards, and has been covered with pollen before the
opening of the flower. The hood, on withdrawal of the pressure,
springs back into its former place, and covers the pistil and stamens
as before.

So, in young flowers, bees dust the lower part of their heads
with pollen ; in older ones they supply the stigma with pollen from

previously visited flowers. As the bees habitually go from below
“upwards on each plant, they bring pollen to the lower and older
flowers of one plant from the upper and younger flowers of
another, and thus regularly induce crossing of separate stocks.
This is very noteworthy, since Hildebrand has shown by many
experiments that the flowers of C. cava are absolutely barren to
their own pollen, very slight!y fertile to pollen from another flower
of the same plant, and only thoroughly fertile when impregnated
with pollen from a different plant.

Since the spur of C. cava is 12 mm. long, and is at the very
most filled with honey to the extent of 4 or 5 mm., it is quite
impossible for the hive-bee with its proboscis of 6 mm. to reach
_the honey in the legitimate way. Bombus terrestris, L. 2, might
succeed better with its proboscis of 7 to 9 mm., occasionally even

10 mm.; but even this species soon gives up thrusting its proboscis
H

98 THE FERTILISATION OF FLOWERS. [PART ITI.

between the hood and the upper petal. It more usually bites
a hole in the spur at, or a little in front of, its place of bending,
and through this hole thrusts its proboscis to the extremity of the
spur. I found the great majority of flowers to have been bitten
through in this way by JB. terrestris, 2, and through the holes I
saw not only the hive-bee, but also Andrena albicans, K. 9,
A. nitida, Foure. ¢, Sphecodes gibbus, L., and Nomada Fabriciana,
L. 2, obtain the honey. The only bee which I have seen sucking
the honey of C. cava legitimately is Anthophora pilipes, F. 2 and ¢,
with its proboscis of 19 to 21 mm. But this species visited the
flowers of Corydalis in such numbers and so diligently that it
should suffice for the fertilisation of all. I have only seen two
other insects legitimately sucking the honey of C. cava, viz.
Bombylius major, L. (10) and B. discolor, Mgn. (11 to 12), which,
hovering over the flowers, thrust in their long proboscides, without
however, accomplishing fertilisation. ‘The hive-bee must also be
included among the fertilisers of C. cava. I have often seen it
creeping in between the hood and upper lip with the fore-part of
its body in order to collect pollen, which it swept off the stigma
with the tarsal brushes of its middle legs, and placed in the pollen-
baskets on its hindlegs. An ant, Lasiws niger, L. %, enters the
flowers and makes its way to the honey (590, L.).

24, CORYDALIS SOLIDA, Sm., resembles the former species in
the mechanism of its flowers, and has a spur sometimes as long,
sometimes very slightly shorter. In the spot where I have observed _
it (Stromberg Hill), it grows together with C. cava, but in smaller —
numbers, and always with red flowers (C. cava being white or red). —
In this locality its honey is sucked legitimately, as in C. cava, by —
Anthophora pilipes, F., Bombylius major, L., and B. discolor, Mgn.;
the honey is stolen by means of a hole by JB. terrestris, L. ¢, and —
Apis mellifiea, L. $, and the plant is also visited and fertilised —
by the last-named for the sake of its pollen. }

Corydalis nobilis, Pers, and C. capnoides, Whinb., have, according —
to Hildebrand, a similar arrangement to that of C. cava (358).

Corydalis ochroleuca, K., is marked off from C. cava by the fact —
that the hood, when once bent down, does not rise again, while the —
stamens and pistil fly upwards and become concealed in a hollow —
of the upper petal. Hence each flower can only be visited by bees —
once in such a way as to influence these organs. This single visit —
dusts the under side of the bee with the pollen which has been.
heaped up on the stigma, and also brings other pollen to the

parti] § THE MECHANISMS OF FLOWERS. 99

stigma if the bee comes from another flower. Hildebrand’s
experiments prove that the flowers of C. ochroleuca are fertile both
with their own pollen and with that from another flower of the
same plant.

25. CoRYDALIS LUTEA, D.C., resembles C. ochroleuca in the
mechanism of its flower. I saw it repeatedly visited and sucked
in the legitimate way by Bombus agrorum, F. 2, whose proboscis
measures 12 to 15 mm. Other bees which I have seen visiting the
flower are enumerated in my Weitere Beobachtungen, pt. i. p. 54.

cam

26. FUMARIA OFFICINALIS, L.—The mechanism of the flower
resembles that of Corydalis cava ; but the flowers are much smaller,
and instead of the long spur, a short rounded pouch is present
in which a short process from the upper stamen is lodged and
secretes honey. Hildebrand found the flowers to be fertile to their
own pollen; but he doubts whether self-fertilisation often occurs
under natural conditions, and places full reliance on the agency
of insects.

I have often watched J/. officinalis, and have convinced myself
most clearly that it is very sparingly visited by insects. I have
“only occasionally observed the hive-bee sucking at this flower,
and I have very frequently watched in vain even in calm sunny
weather for a single insect visitor.

It is Sasi ale advantageous to a plant for its flowers to be
adapted for fertilisation not by one or a few, but by many species
of insects. In Fumaria officinalis, whose flowers might be visited
by most kinds of bees on account of the shallow situation of the

honey, this advantage which it has over C. cava is outweighed
by several disadvantages. For C. cava blooms in early spring at a
time and in places hers few flowers compete with it in attracting
insects (its chief rivals on Stromberg Hill are Primula elatior and
Pulmonaria officinalis); while Fumaria officinalis blooms in the
middle of summer when many flowers at the same time are trying
to divert the attention of honey-seeking bees. And further, while
C. cava with its handsome spikes of flowers is very conspicuous
in comparison with its neighbours, and displays a rich booty of
honey and pollen to its guests, the small flowers of Fumaria
officinalis are very inconspicuous In comparison, and give but a poor
promise of spoil. Hence we see that although the honey of
Corydalis cava can only be reached legitimately by one out of the
‘tnany species of bees that are on the wing during its flowering
H 2

100 THE FERTILISATION OF FLOWERS. [PART III.

period, yet it is so regularly fertilised by that one, that it has quite
lost the power of self-fertilisation ; while /wmaria officinalis, though
it might be fertilised by very many kinds of bees that are abundant
while it flowers, is so little visited that it is forced as a rule to
reproduce by self-fertilisation. I have repeatedly noticed how very
seldom Fumaria officinalis is visited by insects, and have observed
that notwithstanding almost every flower has borne fruit. I have
also found that during continued rainy weather which keeps every
bee away, F”. officinalis is still fully fruitful, and I cannot therefore
doubt that it makes the fullest use of its power of self-fertilisation.

The same holds good with regard to Fumaria capreolata, L.,
and /. parviflora, Lam., which on the whole agree, according to
Hildebrand, with / oficinalis in their mechanism of fertilisation,
but have lost the elasticity of the hood, probably through long
disuse. ,

In Fumaria spicata, L., on the other hand, the structure of the
flower resembles, according to Hildebrand, that of Corydalis lutea
and C. ochroleuca. The column, after once emerging from the
hood, springs up, owing to the tension of the upper stamens, and
buries itself in a depression in the upper petal. This species is
also fertile to its own pollen.

Fumaria capreolata, var. pallidiflora, has this remarkable
peculiarity, first mentioned by Moggridge, that its flowers, which
are at first almost white, assume a conspicuous pink or even
carmine tint after fertilisation. A similar change of colour occurs
in Lantana, Weigelia rosea, Ribes aureum, R. sanguineum, and
many other flowers which are fertilised by the more intelligent
insects (bees or Lepidoptera). The insects are attracted from a
distance by the bright colours of the older flowers, and they learn
to distinguish very quickly between these and the less conspicuous
younger flowers which alone contain treasure for them ; while the
less intelligent insects, useless in these cases for the work of
fertilisation, betake themselves chiefly to the more showy flowers
(74, 309, 530, 575, 590, L.).

Ord. CRUCTFERA.

27, NASTURTIUM SILVESTRE, R. Br.—At the base of the flower,
between every two stamens, there is visible a green fleshy gland,
which secretes a drop of honey. The anthers of the four longer
stamens are on a level with the stigma, the other two lie somewhat
deeper; all remain turned towards the middle of the flower. In

_ PART III. | THE MECHANISMS OF FLOWERS. — 101

- sunny weather, when the flowers open, the anthers spread apart a
little, and dehisce on the side turned towards the stigma. Insects
which make for the honey must thrust their heads into the flower
between the stamen and stigma, and bring one side of the head in
contact with one or two anthers, and the other with the stigma. If
they move round the flower licking up all the honey-drops, as a
rule the same side of the head remains turned to the stigma
_ throughout. In subsequent flowers the opposite side of the head
' may touch the stigma, and lead to cross-fertilisation. It may
| happen, and perhaps does so happen frequently, that the insect
_ plunges its head several times into the same flower, and so leads to
_ self-fertilisation. In rainy weather the flowers only partially
_ expand, and the anthers of the longer stamens remain in immediate
contact with the stigma, and accomplish self-fertilisation.

Fig. 31.—Nasturtium silvestre, R. Br.

3 Flower from above. In the centre is the stigma concealing the ovary; around it are seen four
larger (n) and two smaller (n’) honey-drops. a, the longer stamens; a’, shorter ditto, In all the
| stamens, the pollen-covered face of the anther is visible, turned towards the stigma.

, Visitors: A. Hymenoptera—(a) Sphegide: (1) Crabro Wesmeeli, v. d.
1 L., s.; (2) Tiphia minuta, v. d. L., s.; (b) Apide: (3) Apis mellifica, L.
| 8, «p., ab.; (4) Andrena Schrankella, K. 9, e.p.; (5) Halictus nitidius-
| culus, K. 9,8. B. Diptera—(a) Empide: (6) Empis livida, L.,s.; (b) Syr-
| phide: (7) Syritta pipiens, L.,s. and f.p.; (8) Syrphus sp.,s. and f.p.; (9)
rf Chrysogaster Macquarti, Loew., s.; (10) Eristalis arbustorum, L., s. ; (c)
_ Bombylide : (11) Anthrax hottentotta, L., s.

— _—— Nasturtium officinale, R. Br—There is a remarkable difference
_ between the flowers of this species and those of JV. silvestre. At
the inner side of the base of each short stamen are two green
fleshy honey-glands, placed close together. The shorter anthers
have their dehiscent sides turned towards the stigma, which stands
high above them; the taller, which stand at first on a level with
the stigma, but are afterwards overtopped by it, have their
| dehiscent sides turned towards the shorter stamens, so that the
head or proboscis of an insect passing down towards the nectary,

102 THE FERTILISATION OF FLOWERS. [PART III.

must touch simultaneously the stigma and the pollen-covered faces
of three anthers, one short and two long. If, in continued bad
weather, the flowers do not open fully, self-fertilisation is effected
by the longer anthers, as in JV. silvestre (590, 1., 609).

28. ARMORACIA AMPHIBIA, Koch. (Nasturtium amphibium, BR.
Br.).—The structure of the flower resembles that of Nasturtiwm
silvestre.

Visitors : A. Hymenoptera— Tenthredinide : (1) Tenthredo notha, K1., very
abundant, passing from flower to flower and dipping its proboscis down to
suck,—head and thorax richly dusted with pollen. B. Diptera—(a) Empide :
(2) Empis livida, L., s. ; (6) Syrphide : (3) Rhingia rostrata, L., s. ; (4) Syritta
pipiens, L., s.; (5) Eristalis arbustorum, L., s.

Arabis alpina, L., is homogamous (609).
Arabis bellidifolia, Jacq., is proterogynous, with long-lived
stigmas (609).

29. ARABIS HIRSUTA, R. Br.—The arrangement of the flowers
differs from that of Nasturtium silvestre in that only two glands
lying internal to the base of the shorter stamens secrete honey, and
that in most flowers the longer stamens arch over the stigma, and
shed their pollen on it, if it is not removed by insect visitors.
Flowers also occur in which the anthers of the longer stamens stand
on the same level as the stigma, and shed their pollen in immediate
contact with it.

Visitors : A. Hymenoptera—(a) Sphegide : (1) Ammophila sabulosa, L., s. ;
(b) Apide: (2) Apis mellifica, L. $,s.; (3) Halictus sexnotatus, K. 9, ep. ;
(4) Andrena albicrus, K. ¢,s. 3B. Lepidoptera—Bombyces : (5) Euprepia
Jacobee, L.,s. C. Diptera—Syrphide : Syritta pipiens, L., s.

30. CARDAMINE PRATENSIS, L.—This species differs greatly from
the preceding forms in the situation of its honey, in the position of
its anthers, in the conspicuousness of its flowers, and hence also in
the number of its visitors. Two large honey-glands surround the
bases of the two shorter stamens as green fleshy cushions which are
most marked at the outside and secrete their honey at that point :
two smaller honey-glands occupy the position of the two aborted
smaller stamens," 7.¢. they are placed antero-posteriorly, between the

1 Kichler’s view of the floral symmetry and number of the parts in Crucifere is
different from that advanced here by the author, and is now more generally adopted.
He regards the number two as the basis of the floral whorls, and looks upon the four
petals and the four inner stamens as due to the chorisis respectively of two antero-

posterior petals and stamens. On this view the whorls alternate regularly with each
other, and the flower is symmetrical. (Eichler, Blithendiagramme, vol. ii.)

PART III. | THE MECHANISMS OF FLOWERS. 103

pairs of long stamens. The honey secreted by these four glands
accumulates in the pouched bases of the sepals. Since the calyx in
this case serves to hold the honey it is more persistent than in most
other Crucifers, and the sepals are unusually large, in relation to the
great size of the honey-glands ; those which receive the honey from
_ the larger glands are broader and more swollen at the base than
the two others, so that one may tell by looking at the calyx from
' below where in the flowers the shorter stamens are placed. On
| tearing off the sepals, a honey-gland is seen between the claws of
_ each pair of adjacent petals.

I: In the young bud all the six anthers are turned towards the
pistil, which projects above them. Before the flower opens, the

Fic, 82.—Cardamine pratensis, L.

1.—Flower, from above,
2.—Ditto, in side view, after removal of the two anterior petals.
3.— Essential organs and nectaries (nm), enlarged.

_ four inner stamens elongate and overtop the stigma, and make a
1 quarter of a revolution outwards, each one towards the small
"7 stamen nearest to it: so that now an insect, in trying to reach the
1 honey of one of the larger glands, must rub its head or proboscis
ie against the pollen-bearing surface of one of the taller anthers.

In cold, rainy weather flowers are often found in which the
_ revolution is incomplete, or does not take place at all, and in such
} cases the pollen of the longer stamens falls of itself upon the
stigma. The shorter stamens always remain with the side at which
| they dehisce turned inwards towards the stigma, so that the pollen
_is rubbed off by the head or proboscis of any insect which is

Bresso

104 THE FERTILISATION OF FLOWERS. [PART III.

making for the smaller honey-glands. With reference to the
likelihood of cross-fertilisation the same remarks hold good as in
the case of Nasturtiwm silvestre. In many flowers the shorter
anthers stand lower than the stigma, in others on a level with it
or even higher. In the two last cases they may aid in self-
fertilisation.

Cardamine pratensis surpasses all the other Crucifers which grow
wild near Lippstadt in the conspicuousness of its flowers and the
abundance of its honey, and consequently in the number of its
insect visitors.

A. Hymenoptera—A pide : (1) Halictus cylindricus, F. 2. ¢p.; (2) An-
drena dorsata, K. 9,s.; (3) A.parvula, K. 9 ¢, cp. ands. ; (4) A. Gwynana,
K. 2, ¢p., (once it flew straight from the Curdamine to a short-styled flower
of Primula elatior and gathered pollen there also) ; (5) Nomada lateralis,
Pz. 9,s.; (6) N. lineola, Pz. ¢,s.; (7) Osmia rufa, L. ¢,s.; (8) Bombus terrestris,
L.?,8.; (9) Apis mellifica, L. $, very ab., c.p. ands. B. Diptera—(a) Bom-
bylide: (10) Bombylius major, L., once, hovering over the flower and suck-
ing,—it passed straight from the Cardamine to Primula elatior; (11) B.
discolor, Mgn., s. ; (6) Empide : (12) Empis opaca, F., s. ; (c) Syrphide : (13)
Rhingia rostrata, L., f.p. ; (14) Helophilus pendulus, L., s. ; (d) Muscide : (15)
Anthomyia sp., fp. ©. Lepidoptera—(16) Rhodocera rhamni, L. ; (17) Pieris
brassicee, L. ; (18) P. napi, L. ; (19) Anthocharis cardamines, L. D. Coleop-
tera—(a) Nitidulide: (20) Meligethes, ab., lh.; (6) Staphylinide: (21)
Omalium florale, Pk., very ab. E. Thysanoptera—(22) Thrips, s. and fp.
See also 590, I.

Cardamine chenopodifolia, Pers., has cleistogamic flowers which
burrow into the earth (296).

Cardamine impatiens, L., is visited by Andrena albicans,
K. 9 (590, 1.). |

Barbarea vulgaris, R. Br—EKach of the two shorter stamens has
on either side of its base a small, green, fleshy honey-gland ; a some-
what larger honey-gland is placed between each pair of longer
stamens, externally to their bases, in the position of the two short
stamens that have disappeared. On each of the six glands a colour-
less drop of fluid may be seen in fine weather. The anthers are
placed as if the glands between the longer stamens were absent.
The taller stamens, which overtop the stigma, make a quarter of a
revolution towards the neighbouring short stamens ; this movement
begins with the dehiscence of the anthers immediately after the flower
expands, and is just finished when the anther is completely covered
on one side with pollen. The two shorter anthers, which are on a
level with the stigma, remain turned towards it even after dehis-
cence, so that the position of the anthers is the same as in

PART IIL. ] THE MECHANISMS OF FLOWERS. 105

Nasturtium officinale, though the number of glands is as in N.
silvestre (590, I.).

31. DRABA VERNA, L.—Four small, green, fleshy honey-glands
occur in each flower, each being situated between the bases of a
short stamen and the long one next it; so that the base of each
short stamen stands between two honey-glands. Anthers and
_ stigma ripen together. The longer stamens reach to a level with
_ the stigma, and stand close around it: they dehisce on those sides
_ which are turned towards the stigma, and always dust it with
| pollen; the shorter stamens also turn their pollen-covered surfaces
| towards the stigma, but stand below it. Honey-seeking insects
_ must thrust their proboscides between the stigma and one of the
_ shorter stamens into the base of the flower, and so dust themselves
_ with pollen, especially from the shorter stamens, and carry it
_ elsewhere, Cross-fertilisation is chiefly effected with pollen from |
_ the shorter stamens, while the four longer ones regularly effect self-
fertilisation. Hildebrand has found by experiment that the latter
is productive. We may understand the extensive use that this
plant makes of self-fertilisation if we consider how small and
_ inconspicuous the flowers are, how small a supply of pollen or
honey they can yield, and how few insects they are for these reasons
visited by. I have only observed three species of bees on Draba
verna, VIZ :—

, (1) Apis mellifica, L. §, cp. (April 10, 1868); (2) Andrena parvula, K.
¢,. (March 28, 1869) ; (3) Halictus sp. 9, s. (March 28, 1869).

Draba aizoides, L., is proterogynous with persistent stigmas (600).
Draba Wahlenbergii, Hartm., is homogamous (609).

32. COCHLEARIA OFFICINALIS, L.—Near Niederalma, I saw the
following insects on flowers of this plant (July 12, 1869) :—

A. Diptera—Syrphide : (1) Eristalis tenax, L.; (2) Helophilus floreus,
_ L.; (8) Melanostoma mellina, L., ab., all three both s. andc.p. B. Coleoptera
_ —(4) Cetonia aurata, L., gnawing the parts of the flower.

Kernera saxatilis, Rich., is homogamous. The four longer
stamens bend laterally almost to a right angle, so that their anthers
come to lie quite close to those of the shorter stamens (609).

Thlaspi arvense, L., is homogamous. The shorter stamens are
concerned in cross-fertilisation ; the longer, in case of need, effect
self-fertilisation (590, I1.).

106 THE FERTILISATION OF FLOWERS. [PART IIT,

Pringlea antiscorbutica, Hook., grows on the tempestuous shores
of Kerguelen’s Island, where winged insects cannot exist, because at
every flight they run the risk of being drowned. Under these
circumstances the plant has become modified for fertilisation by
the wind, acquiring exserted anthers and long filiform stigmatic
papillz. It still retains traces of its descent from entomophilous
ancestors ; for while on the great part of the island it is devoid ot
petals, it occurs abundantly in sheltered places with petals. On
the same raceme some flowers may possess only a single petal,
others two, three, or four; and the petals, though usually of a
pale greenish colour, are occisignilly adorned with Bec (216,

372).

Fig. 33.—Kernera saxatilis, Rich.

A.—Flower, viewed from above.
B.—Ditto, from the side, after removal of two petals (x 7), k, short stamens.

33. TEESDALIA NUDICAULIS, R. Br.—The structure of this
flower, whose longest petals are only two mm. long, differs
remarkably from our other native Crucifers.

During the period of flowering, the flowers are aggregated into
a flat surface, whose outermost petals are larger than the others, as
in the case of Umbellifers. But in 7eesdalia, as flowering progresses,
the axis lengthens and draws out the flat surface into a raceme,
so that each flower comes to stand at the edge in its turn. So
it is not only certain flowers that stand from the beginning at
the edge, which have the corolla specially developed on the outer
side (as in many Umbelliferw and Composite), and thus become
symmetrical about a single axis (zygomorphic) ; but all the flowers
have their outer petals specially developed, and thus acquire a
zygomorphic symmetry.

Each flower has a superior (s), an inferior (s’), and two lateral
sepals (s”), which help to render the flower conspicuous by white
tips and a white median ridge; but conspicuousness is chiefly

}
}

i r

pi
Y

PART ILI. | THE MECHANISMS OF FLOWERS. 107

attained through the white colour of the petals, of which the

flower has two superolateral ones (p), and two anterolateral (p’),
twice or three times as long as the former. In addition, there
are petal-like appendages (y, 4, z, 2, 3) to the two lateral and

_ shorter stamens (a), and others, still larger, to the four longer
ones (a’, a). The petal-like appendages of these four inner
_ stamens closely surround the ovary, which is flattened antero-

posteriorly, sharp-edged on each side, bent slightly forwards, and

_ divided symmetrically by a partition wall.

The centre of the base of each petal has a small pouch, and

_ just above this each staminal protuberance is provided with a
similar structure; between the two lies a little drop of honey, and

concealed beneath this is a small, greenish, fleshy honey-gland.

Both the petals and the longer stamens can be torn away without
injuring or removing the glands; which seem therefore to belong
to the base of the flower (receptacle),

scaanieeestnc aniline
as »

nape, —

Fic. 84—Teesdalia nudicaulis, R. Br.

1.—Flower, from above.

2.—Anterior half of flower.

3.—One of the longer stamens, with a nectary, seen from without.
4.—One of the two shorter stamens, from without.

x, y, foliar appendages of filaments ; n, nectary.

Before the flower opens, the six anthers are all turned towards

_ the stigma, the four longer ones overtopping it slightly, the others

standing on a level with it. After the flower has expanded, all
six stamens twist through a quarter of a revolution; each of the
_ longer ones turns its anther towards the adjacent shorter one ;
while each of the two shorter ones turns towards the outside

_ of the flower. Now the anthers dehisce, and at the same time

the stigma becomes mature. Insects in reaching the two outer

_ honey-drops cannot avoid touching with their head or proboscis

the pollen-covered sides of the two neighbouring anthers; while

_ those that suck the inner drops only come in contact with the

: — ,

pollen of a single anther. Owing to the small size of the flower,

| the insect must touch the stigma at the same time with another

108 THE FERTILISATION OF FLOWERS. [PART III.

part of its proboscis or head. As we have scen in other cases,
this must regularly lead to cross-fertilisation if the insect thrusts
its head only once into the flower, but may equally well produce
self-fertilisation if it does so more than once. In absence of
insects self-fertilisation is always accomplished by means of the
longer stamens.

On April 27 and 28, 1872, I and my son Hermann saw the
following insects visit a luxuriant patch of Teesdalia in sunny
weather :— |

A. Hymenoptera—A pide : (1) Sphecodes ephippia, L., sucking on thirteen
inflorescences successively. B, Coleoptera—(a) Chrysomelide: (2) Haltica
nemorum, L., three specimens, apparently sucking ; (8) Plectroscelis dentipes,
E. H., one specimen, do. ; (4) Cassida nebulosa, L., two specimens flew on to
the inflorescence without making use of the flowers; (b) Curculionide: (5)
Ceutorhynchus pumilio, Gylh., two specimens, s. ; (¢) Elateride : (6) Limonius
parvulus, Pz. ; (d) Hydrophilide : (7) Cercyon anale, Pk. (these last two beetles
also settled on the flowers, but I could not see that they made use of them in any
way). C. Diptera—(a) Syrphide : (8) Melithreptus sp. ; (9) Ascia podagrica,
F., both fp. ; (6) Muscide: (10) Sepsis putris, L., ab., s. Also many minute
Muscidz and gnats, 1 to 4 mm. long.

Biscutella levigata, L., is homogamous. I have found it
visited by thirty-six species of insects, mostly Diptera (609).

Hesperis tristis, L.—This plant, by elongation and close approxi-
mation of the sepals and the claws of the petals, excludes all
insects except Lepidoptera from its honey. By the time of ex-
panding and emitting its perfume it has become adapted for
cross-fertilisation by crepuscular and nocturnal forms (570, vol. xii.).

34. HESPERIS MATRONALIS, L.—Honey is secreted by two
very large, green, fleshy glands surrounding the base of the shorter
stamens, and especially developed on their inner sides; it collects
on each side of the flower between the pistil and the bases of
the three stamens of that side.

The taller anthers stand at the entrance of the flower, and only
project beyond it when they have withered. ‘The shorter stand a
little deeper within the flower, and when they dehisce their tips
closely surround the stigma, which is afterwards protruded beyond
the flower by the lengthening of the pistil. All the anthers
dehisce inwards, and cover the stigma with pollen. If insect-
visits take place at the proper time, cross-fertilisation is also
effected: regularly by the honey-seeking species, for they touch

q PART III. | THE MECHANISMS OF FLOWERS. 109

stigma and stamens with opposite sides of the proboscis, and, at
least sometimes, by pollen-seeking forms.

: Visitors : A. Diptera—(a) Stratiomyide : (1) Nemotelus pantherinus, L.
f.p.; (b) Syrphide : (2) Chrysogaster enea, Mgn. (Tekl. B.), f.p. ; (3) Eris-
talis nemorum, L.; (4) E. tenax, L., both f.p.; (5) Volucella pellucens, L.
(Tekl. B.); (6) Rhingia rostrata, s., very ab. B. Hymenoptera—A pide : (7)
Halictus leucopus, K. 2 ; (8) Andrena albicans, K. ?; (9) Apis mellifica, L.
%,allthree cp. C. Lepidoptera—{10) Pieris brassice, L., s.; (11) P. napi,
Ls. ; (12) P. rape, L., s. D. Coleoptera—(13) Anthocomus fasciatus, L. See
also, 590, II.

35. ALLIARIA OFFICINALIS, Andrzj. (Sisymbrium Alliaria,
_ Scop).—The honey-glands agree in character and situation with
those of Cardamine pratensis. But while in C. pratensis the honey
- is secreted towards the outside, and collects in the pouched sepals,
in A: officinalis it exudes inwards from the glands at the base of
the short stamens, and forms four drops in the base of the flower.
These each lie between a short stamen and the adjacent’ long
one, and finally fill the lower part of the space between the
stamens and pistil, to which parts they adhere firmly. I have
never observed secretion on the part of those glands which occupy
_ the position of the two aborted short stamens; they seem to be
functionless ancestral structures. The sepals, which persist as
receptacles for the honey in C. pratensis, are in A. officinalis only
useful in the bud, as a protection for the parts within, and by
~ contributing by their white colour to the conspicuousness of the
inflorescence ; when the flower expands they cease to be of use
and easily disp off.

: All the anthers dehisce inwards; the inner ones surround the

_ stigma so closely that they alnaye effect self-fertilisation, and
_ this, as I have proved, leads to the production of good seed.
_ Cross-fertilisation must, as in the foregoing species, be effected

i very frequently by honey-seeking insects, and at times by pollen--
__ seeking species ; and it probably then outstrips self-fertilisation in
its action.

Visitors: A. Hymenoptera—Apide : (1) Apis mellifica, L. $,s. B. Dip-
tera—(a) Syrphide: (2) Syrphus decorus, Mgn. (Tekl. B.); (3) Rhingia
rostrata, L.,s.; (b) Muscide : (4) Anthomyia, s. C. Coleoptera—(a) Nitidulide :
_ (5) Meligethes, ab.; (6) Epurea; (b) Curculionide: (7) Ceutorhynchus, a
minute species. See also 590, Il.

36. SISYMBRIUM OFFICINALE, Scop.—The structure of the
flower agrees fairly with that of the foregoing species. Each of

110 THE FERTILISATION OF FLOWERS. [PART III.

the two shorter stamens -has on either side of its base a honey-
gland; each of the four honey-drops secreted by these lies in the
space bounded by one of the shorter stamens, the adjacent long
one, and the pistil. The anthers ripen along with the stigma,
which their pollen-covered sides face; the taller anthers overtop
the stigma and arch inwards, the shorter stand on a level
with it, and curve slightly outwards. In default of insect-
visits pollen regularly falls upon the stigma from the four long
stamens.

The flowers are very small, and for that reason insect-visits are
scarce. The honey, however, seems to be particularly liked by cer-
taininsects. On June 27, 1868, ona waste patch where S. officinale
and Capsella bursa-pastoris were growing abundantly with several
other plants, I noticed’ Pieris napi, L., and P. rape, L., flying about
in great numbers, and sucking the flowers of this plant only. The
point of the insect’s proboscis is thrust in between the stigma and
the anthers. I also saw several specimens of Andrena dorsata,
K. 9, in quest of pollen: they were probably as likely or more
likely to effect self-fertilisation than cross-fertilisation.

Visitors: A. Hymenoptera—Apide: (1) Andrena dorsata, K., ¢.p. and

f.p. B. Lepidoptera—Rhopalocera: (2) ‘Pieris napi, L., s.; (3) P. rape

L., s. See also 590, it.

37. CAPSELLA BURSA-PASTORIS, D.C.—The only difference
to be noted between this and the foregoing is that the long
stamens stand on a level with the stigma, and effect self-fertilisa-
tion regularly. Specimens which I kept in a room and protected
from insects were fully productive.

Visitors : Diptera—(a) Syrphide: (1) Eristalis nemorum, L., s. and fp. ;
(2) Syrphus balteatus, Deg., do. ; (3) Syritta pipiens, L. ; (4) Ascia podagrica
F., s. ;(5) Melithreptus scriptus, L. ; (6) M. teeniatus, Mgn. ; (7) M. pictus, Mgn.,
the last three s, and f.p. ; (b) Muscide : (8) Anthomyia,s. See also 590, U1.

38. LepipiIumM sativuM, L.—The flowers are inconspicuous,
but their strong scent is perceptible even to us several paces off.
Owing doubtless to this, they are more abundantly visited than
any other Crucifer which I have observed, partly for their honey,
partly for their pollen. The honey is secreted by four green,
fleshy glands, situated between the long and short stamens, and
opposite to the petals; the two long stamens on each side face
the broad surface of the silicula, and arise close together between
the two lateral petals. The anthers dehisce introrsely, and the

ee ee EN ene - eer

“parr ut] THE MECHANISMS OF FLOWERS. 1

stamens undergo no twisting, but in sunny weather they bend
backwards as far as the nearly upright sepals permit them. As
to the likelihood of cross- or self-fertilisation, the same holds as
in the case of Nasturtium silvestre. When in rainy weather the
flowers do not fully open, or when they close up again without
4 being visited by insects, self-fertilisation occurs.

Visitors: A. Diptera—(a) Leni : (1) Argyromeeba aca Fallen ;
(bd) em (2) Eristalis pide be .; (3) E. nemorum, L. ; (4) E. sepul-
eralis, L. ; (5) Helophilus floreus, L. ; (6) Syritta pipiens, L., very ab. 3 ; (7)
Melithreptus teeniatus, Mgn. ; (8) ‘Aéeia podagrica, F., very abe ; (9) Pipiza
chalybeata, Mgn., all these Syrphide now s., now fp. ; (c) Muscide : (10)
Siphona cristata, F. B. Hymenoptera—(a) Ichneumonide : stragglers; (b)
Sphegide: (11) Oxybelus bellus, Dib., ab. ; (12) O. uniglumis, L., very ab. ;
(18) Cemonus unicolor, F.; (14) Cerceris variabilis, Schrk., very ab.; (c)
Uhryside : (15) Hedychrum lucidulum, F. ¢; (7) Apide: (16) Prosopis com-
"munis, Nyl. ¢ 2, very ab., s. and f.p.; (17) P. armillata, Nyl. ¢ 9, do. ; (18)
if Halictus nitidiuseulus, K.9, 5. ; (19) H. lucidulus, Schck. 2, s.; (20) Andrena
- parvula, K.? ; (21) A. pilipes, F.¢,s. C. Coleoptera—(a) Dermestide -: (22)
_ Anthrenus pimpinelle, F.; (b) Malacodermata: (23) Dasytes flavipes, F. ;
(24) Anthocomus fasciatus, F, ; (25) Malachius bipustulatus, F., gnawing the
anthers and petals. D, Lepidoptera—(26) Sesia tipuliformis, L., s., frequent.

Hutchinsia alpina, R. Br., is proterogynous with persistent
stigmas. It is visited and cross-fertilised by Diptera (609).

39. BRASSICA OLERACEA, L.—Two honey-glands lie on the
inner side of the bases of the two short stamens, and two others
occupy the position of the aborted pair, 7.c. are antero-posterior.
| a honey-drops secreted by the two former distribute themselves
ach between a short stamen, the two adjacent long ones, and the
; F nistil and are easily visible on looking straight downwards into
F in. open flower; the drops from the other pair of glands lie
ctside eticen the two adjacent long stamens, and these drops
increase until they sometimes reach the sepals. The two shorter
Manithers stand sometimes on a level with the stigma, usually
: 4 owever they are not so high; they curve outwards, but their
?P ollen-covered sides face the centre of the flower. The long
- stamens perform a quarter- or half-revolution without increasing
| their distance from the centre of the flower, so that the pollen-
covered sides of their anthers are either turned towards the
neighbouring short stamen, or else directly outwards. An insect
in sucking the honey at the base of a short stamen touches with
one side of its head or proboscis the stigma, and with the other
_ a short stamen and usually a long one at the same time: the

2.

112 THE FERTILISATION OF FLOWERS. [PART II. :

other two drops of honey can be reached without touching the

4

nt
al
|

stigma, and seem to afford no aid in fertilisation. In default —

of insect-visits the upper part of each of the long anthers bends
back so far’as to touch the stigma, thus effecting self-fertilisation.

This self-fertilisation is probably efficient: at least B. rapa, L.,
was found by Hildebrand to produce seed when self-fertilised (351).
In sunny weather I have always found the honey very evident.
Sachs,! who says “the dark-green nectaries lying between the
stamens of Brassica retain their secretion within them,’ has
probably examined the flowers in dull weather.

Visitors: A. Coleoptera—Nitidulide : (1) Meligethes, very ab., feeding on
the petals and on pollen. B. Hymenoptera—Apide : (2) Andrena nigroznea,
K. 9,s.; (8) A. Gwynana, K. 9, s. and fip.; (4) A. fulvicrus, K. 9, cp. ;
(5) A. nana, K.?,s. and f.p. ; (6) Halictus cylindricus, K. 9 ; (7) Apis mellifica,
L. $,s.andf.p. (I did not see the hive-bee preserve any definite order in

visiting flowers of this plant ; frequently a bee after visiting a second flower —

returned to the first). C. Thysanoptera—(8) Thrips, ab.

40. SINAPIS ARVENSIS, L—The honey-glands are placed as
in Brassica. When the calyx expands, the glands are visible and
accessible from the outside, and insects can reach them without
touching the essential organs of the flower. The close aggregation
of the flowers however renders it more convenient for the insect
to thrust its proboscis down between the stamens, and in point
of fact I have never seen an insect visitor obtain the honey from
the outside. The twisting of the stamens and the likelihood of
cross-fertilisation are as in Cardamine pratensis; as the flowers
wither, however, the anthers turn their pollen-covered sides up-
wards, and finally their tips bend downwards, so that they effect
self-fertilisation if their pollen has not already been removed.

Visitors : A. Diptera—Syrphide : (1) Eristalis eneus, Pz.; (2) E. arbus-
torum, L. ; (3) Rhingia rostrata, L., all these both s. and fp. B. Hymen-
optera—(a) Tenthredinide : (4) Cephus spinipes, Pz., and several small sp.
in great abundance, lh. and f.p.; (b) Apidew: (5) Halictus leucozonius,
Schrk. 9, ¢.p.; (6) Andrena nana, K. ¢,s.; (7) Apis mellifica, L. $, very
ab., both s, and c.p. (I found it collecting pollen on Sinapis on Oct. 2, 1869).
©. Coleoptera—(8) Coccinella Tpunctata, L., lh, D. Lepidoptera—(9)
Euclidia glyphica, L., s. See also §90, IL.

A variety of Sinapis arvensis bears cleistogamic flowers at St.
Croix, where the temperature is 25° C. (762).

1 Lehrbuch der Botanik, 2nd ed., p. 110.

‘

:
;

PART III. | THE MECHANISMS OF FLOWERS. ; wa

41. RAPHANUS RAPHANISTRUM, L., has four honey-glands
| arranged as in S. arvensis, but all the anthers remain turned
towards the stigma, the shorter ones standing on a level with it, so
that the chance of self-fertilisation is increased.

‘I have seen the honey-bee, which usually confines itself to
_ one species of plant, visit flowers of R. raphanistrum and S. arvensis
_ indiscriminately.
| Subularia aquatica, L.—When the water is unusually high, the
| flowers remain closed and submerged, and fertilise themselves (17,

i; REVIEW OF THE CRUCIFER&.

With great uniformity in the general structure of the flower,
_ Crucifers show such variability in the number and position of
_ the honey-glands and in the situation of the anthers in relation
_ to these and to the stigma, that scarcely two of the species that we
have discussed agree fully i in these points.
_ The number of honey-glands may be two, four, or six; they
are placed on or between, the bases of the stamens: and in the
priier case, either on their inner side, their outer side, or round
about them; intermediate positions are sometimes assumed by
: Bstortive and furictionless glands. The honey when secreted either
remains in drops upon the glands or fills spaces between the
_ stamens and pistil or accumulates in sepaline pouches.
____ All or certain of the anthers are placed so that honey-seeking
insects must touch them with one side and the stigma with the
other; but their situation is not always the most favourable for
this Fedult; and the more they diverge from the position most
| favourable to cross-fertilisation, the more chance do they give of
' self-fertilisation.
| This is explained by the following circumstances.
Tn all the Crucifersee which we have considered, the position of
_ the anthers in relation to the honey-glands and the stigma renders
_ cross-fertilisation likely, but not by any means inevitable, on the
visit of a honey-seeking insect; but it does not in any way favour
_ cross-fertilisation more than belffortilisation if the insect comes to
feed on or gather pollen. The abundance as well as the diversity
_ of insect-visitors is not great in the species we have considered ; we
find chiefly ‘flies (especially Syrphide), bees (especially the less
Specialised forms), and in less degree other Hymenoptera (espe-
| cially Sphegide), Coleoptera, and Lepidoptera. Hesperis tristis is
I

114 THE FERTILISATION OF FLOWERS. [PART JIT.

alone adapted for nocturnal insects, and Pringlea has become

anemophilous in the absence of insects suitable for its fertilisation.

On the whole, Crucifers are far behind Umbellifers in the number |
and variety of their insect-visitors, both on account of their less —

conspicuous flowers and their less accessible honey ; and not rarely

plants remain altogether unvisited. The possibility of self-fertilisa-_
tion is useful if not necessary for the preservation of all the Crucifers—

that we have considered; in many we find that self-fertilisation

takes place to a very considerable extent; and in several we have —

experimental evidence that it is productive of seed. Under these

circumstances it would be better-for the plant to forego attaining —
in its anthers the most favourable position possible for dusting —
honey-seeking insects with pollen, if by doing so, while retaining ~

the chance of cross-fertilisation if insects did come, it could fully
- insure self-fertilisation if they did not.

It is impossible, therefore, to consider with Hildebrand that the |
twisting of the stamens in Crucifers is “a remarkable expression —
of repugnance to self-fertilisation” (351, p. 48); it rather refers —

solely, as Axell rightly explains, to the dusting of insects with the
pollen on their way to the honey (17, p. 19). But even Axell’s
statement needed correction and completion, since he only acknow-
ledged two distinct cases in the arrangement of the honey-glands
and the twisting of the stamens, and referred all Cruciferz to
one or other of these two types; and further, he did not take the
position of the anthers into account as an aid to self-fertilisation.
-The way in which conspicuousness is attained throughout the
Umbelliferze by association of many flowers in one surface, and by
asymmetrical development of florets for the common good, is
exemplified only in isolated genera of Cruciferze (Teesdalia, R. Br.,

Iberis, L.); and, in TZeesdalia at least, it does not so far insure

cross-fertilisation that self-fertilisation may be dispensed with.

Orv. CAPPARIDE.
Capparis, L., Cleome, L., and Polanisia, Rafin., are proterandrous,
according to Delpino (172, 352). )
Orv, RESEDACEZ.

42. RESEDA ODORATA, L.—The receptacle is raised up between
the petals and stamens in the upper half of the flower into a
perpendicular quadrangular plate, velvety on its anterior surface,

PART 111. ] THE MECHANISMS OF FLOWERS. © 115

which is yellowish during the time of flowering and orange-red
afterwards. It serves'as a guide towards the honey, which is
secreted and lodged upon the smooth green posterior surface.

. The expanded claws of the upper and middle petals lie close
to the hinder surface of this plate and surround its upper and

dies

,

Ih Xx fy,

A>
4)

ree
{ \ Ht
Wid lt

| Ms

Fie. 35,—Reseda odorata, L.

| - 1.—Flower before the anthers have dehisced, seen from the front.
__2.—Ditto after some of the anthers have dehiseed.

_ 8.—Young fruit in side view.

_ 4.—Left superior petal.
_ §.—Left lateral ditto.

_ 6.—Left inferior ditto.
_ _ a, sepal; b, petal; c, expanded claws of the superior and lateral petals, which surround the
) Shield-shaped swelling of the dise (hk); d, anther bent downwards, not yet dehisced; e, anther
ehiscing and rising up; jf, anther dehisced and erect; g, pistil; h, shield-shaped swelling of the
ise ; i, nectary and honey.

teral borders with their anteriorly directed lobes, thus pro-
scting the honey effectually both from rain and from useless
visitors (flies). The lamin of these petals, which are split into
white, radiating, club-shaped strips, assist the red anthers in
3 I 2

116 * THE FERTILISATION OF FLOWERS. [parr mu.

_ making the flower conspicuous. It is also rendered perceptible at
a distance by its powerful scent.

There is no true expansion of the flower, since its parts lie open .

even in the bud: the commencement of the flowering-period is
marked rather by the honey-glands beginning to secrete, and by
some of the anthers (1, Fig. 35), which had been bent down under
the pistil, dehiscing and rising up towards the honey-secreting plate,
while the three or four carpels at the same time develop stigmatic
papille at their apices.

Since the pistil projects considerably from the middle of the :
horizontal flower, it forms the most convenient landing-place for —

honey-seeking insects, and is hence very readily covered with
pollen from other flowers. In default of insect-visits self-fertilisa-
tion takes place, as the stigmas lie immediately underneath the
erect anthers. Plants which were kept protected from insects
yielded capsules filled with good seed.

The flowers are especially visited by species of Prosopis. In

July, 1867, I had some pots of mignonette in flower in the open .

window of my room. Specimens of Prosopis kept constantly
coming and fluttering, sometimes five or six together, in an un-
usually lively way about the flowers. They sometimes plunged
their heads between the shield-like plate and the upper petals,
licking up the honey with outstretched tongue, and sometimes

gnawed through the still unopened anthers and devoured the
pollen. In subsequent years I have repeatedly observed these

actions on J. odorata and R. luteola, L., both cultivated and wild.
Altogether I have noted the following insects as visitors of our
species of Reseda, including R. odorata.

A. Hymenoptera—(a) Apide: A Prosopis communis, Nyl. BS 6, very

ab. ; (2) P. armillata, N. 9 ¢; (3) P. signata, Pz. 9 ¢, ab.; (4) P. pictipes ©
Nyl. ¢; (5) P. annularis, Sm.?; (6) Apis mellifica, L. $, ab. s. ‘and Cp. 5

(7) Halictus zonulus, Sm. 9c.p.; (8) H. Smeathmanellus, K. Qc.p.; (b) Sphe-
gidew: (9) Cerceris variabilis, Schrk. 2 ¢, s. and f.p. B. Diptera—Syrphide :
(10) Syritta pipiens, L., f.p. C. Thysanoptera-—(11) Thrips, very ab,

43. RESEDA LUTEOLA, L. :—

Hymenoptera—Apide: (1) Prosopis armillata, Nyl. 2 ¢, ab.; (2) P.

communis, Nyl. 2? ¢, very ab., s. and fp. ; (3) Apis mellifica, L. 9, s. and e.p. ;

(4) Andrena nigroznea, K.?,s8, See also 590, I.

44, RESEDA LUTEA, L, (Thuringia) :—

Hymenoptera—(a) Sphegide: (1) Cerceris arenaria, L., scarce; (2) C.
labiata, F., ab.; (3) C. variabilis, Schrk., very ab.; (0) Vespide: (4)
Odynerus parietum, L. ¢, all sucking.

#

‘parr iu.) |THE MECHANISMS OF FLOWERS. NG

Orv. CISTINEZ.

45, HELIANTHEMUM VULGARE, L. (Sauerland).—The flower
has three sepals, five petals which spread out to face the sun, and
“many more than 100 stamens whose anthers mature simultaneously
with the large capitate stigma. The stigma slightly overtops the
anthers, which at first stand close around the centre of the flower,
but move outwards when touched, dusting the insect that touches
them with pollen. The result of this irritability of the stamens is
that the flower is most conveniently approached from the outside,
2¢. from the corolla, by the first visitor, and at least as conveniently
from the centre by subsequent visitors. If an insect which has
‘been dusted with pollen in the first flower alights in the middle of
the next, it always effects cross-fertilisation. In default of insect-
visits, self-fertilisation results in the closed and slightly nodding
flowers. The flower contains no honey, for which the excess of
pollen is some compensation.

Visitors: A. Diptera—Syrphide: (1) Helophilus pendulus, L.; (2)
Syrphus pyrastri, L.; (3) S. ribesii, L.; (4) Melithreptus scriptus, L. ;
(5) M. teeniatus, Mgn. ; (6) Ascia podagrica, F., all fp. B. Hymenoptera—
Apide : (7) Apis mellifica, L. $, ab. ; (8) Bombus muscorum, L. § ; (9) Halictus
oo K.?; (10) Andrena fail vierun; K.@,allep. C, Coleoptera—Ceram-

bycide : (11) Strangalia nigra, L., devouring the anthers.

On the Alps I have found H. vulgare visited by fifty-three

‘Species of insects ; the small-flowered H. alpestre by fourteen. They
were mostly Peers Apide, and Coleoptera, but in part also
Lepidoptera (609).
| Most North American species of Helianthemum produce, in
_ addition to the ordinary flowers, much more numerous cleistogamic
ones. The same occurs in the case of H. Kahiricwm and H. Lippii
in Egypt (531).
The flowers of H. guttatum only open in the morning and
close after a few hours, fertilising themselves if cross- fertilisation
has not meanwhile taken place. The same is the case in H. vil-
losum, Thib., H. eh a ong? L., Cistus hirsutus, L., and C. villosus,
LL. (12).

Lechea, L., also bears cleistogamic flowers (399).

Orv. VIOLARIEZ.

46. VIOLA TRICOLOR, L.—The peculiar arrangement of Viola
' Was in substance elucidated by Sprengel. Hildebrand subsequently
|} drew attention to the lip-like valve of the stigmatic cavity, by

118 THE FERTILISATION OF FLOWERS. [PART III.

which cross-fertilisation is assisted in Viola tricolor, which had been
overlooked by Sprengel. I have observed (No. 570) that this lip,
which insures cross-fertilisation, is only developed in the large-
flowered variegated variety of V. tricolor, while in the small-
flowered, whitish-yellow variety, V. arvensis, the orifice of the

stigma is devoid of a lip and is curved inwards; in this form the

flower fertilises itself spontaneously very soon after opening.

- In all our violets the spurs of the lower anthers act as honey-
glands, and the hollow spur of the lower petal which contains
them forms a receptacle for the honey. To reach the honey in
Viola tricolor, the insect must thrust its proboscis into the flower
close under the globular head of the stigma. This lies in the
anterior part of a groove, fringed with hairs, on the inferior petal.
The anthers, which together form a cone, shed their pollen inte

this groove, either of themselves or when the pistil is shaken by —

the insertion of the bee’s proboscis. The proboscis, passing down
this groove to the spur, becomes dusted with pollen; as it is
drawn back it presses up the lip-like valve so that no pollen can
enter the hollow stigmatic chamber; but as it enters the next
flower it leaves some pollen on the upper surface of the valve, and
thus cross-fertilisation is effected.

I have observed very numerous bees visiting a handsome,
large-flowered. variety which is not uncommon on sandy soil at
Lippstadt, growing along with V. arvensis. Apis mellifica, L. %,
always sucks in a reversed position with its head downwards ;
it often alights in the usual position and then turns round
Humble-bees usually suck hanging back downwards to the

flowers, which are bent down by their weight. Bombus terrestris.

(7 to 9) and B. lapidarius (12 to 14) usually turn round, so as to
introduce their proboscis in the same way as the honey-bee.
B. hortorum (18 to 21) and Anthophora pilipes (19 to 21) grasp the
flower from behind with their forefeet, and insert their tongues
from below in an opposite direction to the honey-bee (590, IL).
Andrena albicans, K. 6, made efforts to suck honey, thrusting
its proboscis repeatedly into the same flower. The attempt must
have been fruitless, as the proboscis of this bee is only 2 to 2} mm.
long, while the pollen-collecting groove described above is 3 mm,
long, and the spur extends for another 3 mm.; in this case, the
repeated insertion of the proboscis into the same flower must have
led to self-fertilisation. I repeatedly noticed a common small fly,
Syritta pipiens, L., eating pollen in the groove and on the anthers
of V. tricolor; as it often touched the stigma also with its

PART III. | THE MECHAN ISMS OF FLOWERS. 119

proboscis, it might easily accomplish self-fertilisation. Delpino
saw V. tricolor visited by Anthophora pilipes. Darwin found it
visited by Bombus sp. and Rhingia rostrata.
| I have found V. tricolor, var. arvensis, to be very sparingly
_ visited, chiefly by bees and humble-bees, more rarely by Rhingia
and by butterflies (590, I1.).
q Viola calcarata, L., greatly surpasses V. tricolor in the size
of its flower and the length of its spur (13 to 25 mm.). It is
| fertilised only by Lepidoptera, chiefly by Macroglossa _ stella-
| tarwm (25 to 28 mm.); our quickest worker. I have seen this
insect visit 194 flowers on different plants in 6? minutes, and I
could see it cross-fertilise them by means of the tip of its proboscis
dusted with white pollen (609).

Viola cornuta, according to Mr, W. E,. Hart (308), is adapted
_ for fertilisation by nocturnal Lepidoptera by its long spur and by
_ emitting its perfume most powerfully by night. He found it visited
by humble-bees, by Hipparchia Janira, and by Cucullia umbratica.

Viola arenaria, D.C., is visited by butterflies (609).

Viola biflora, L., is adapted for fertilisation by Diptera (609).

47, VIOLA opoRATA, L.—Here the end of the pistil which
bears the stigma is not globular and close to the lower petal, but
| stands ata short distance from the latter and is bent downwards
| into a hook. When a honey-seeking insect thrusts its head or
proboscis beneath the stigma it pushes up the pistil and opens
} t the conical ring of anthers; the pollen is thus shed upon the
inserted organ. Thus in every flower the insect touches first the
_ stigma and then causes shedding of the pollen.
ba Sprengel’s experiments led him to the conclusion that if insects
i are excluded the flowers bear no seed.

: t Visitors : A. Hymenoptera—Apide : (1) Apis mellifica, L. %, very ab.,
's, (as Sprengel described and figured (title-page xi.) it comes downwards and
inserts its proboscis into the flower from above) ; (2) Anthophora pilipes,
__F. g, sucks, clinging to the lower petal,—the following species do likewise ;
(3) Bombus hortorum, L. 9 ; (4) B. lapidarius, L.? ; (5) B. Rajellus, Ill. ¢ ;

(6) Osmia rufa, L. ¢ 2, very ab., also enters the flower from above as a rule.
_B. Diptera—Bombylide : (7) Bombylius discolor, Mgn., s. C. Lepidoptera—
(8) Vanessa urtice, L., s. ; (9) Rhodocera rhamni, L., s.

48, VIOLA SILVATICA, Fries. (V. silvestris, Lam .).—The spur is
7 mm. long ; the honey-secreting appendages to the inferior anthers.
which project into it are 5 mm. long. As in JV. trivolor, the cayity

Up»
Wy ON
YL a)

4;

hg

v

Fig. 36.—Viola calearata, L.

A.—Front view of flower, from Piz Umbrail, nat, size. z
B.— Ditto, lateral view (July 16, 1875).
C.—Front view of flower, from Albula, nat. size.
D —Lip of ditto. with its spur (August 2, 1876), ;
E —Front view of the mouth in A (x 84). ‘
F.—Section of A, after removal of the greater part of the corolla (x 84). |
a. anthers; c¢, rf ae of the connectives ; h’, pollen-collecting hairs; h?, hairs which in
species of Viola fertilised by hees aid the bee in clinging to the flower, here preserved as a function- —_
less hereditary character ; k, stigma; J, lip on the under side of the entrance to the cavity of the
stigma (st); sd, honey receptacle ; si, filaments ; ov, ovary.

parr ut] § THE MECHANISMS OF FLOWERS. 121

sn. stigma is protected by a lip-shaped valve; but the pollen
is shed directly upon the insect’s proboscis or head, as in V. odorata.

Visitors: A. Hymenoptera—Apid@ : (1) Bombus agrorum, F., 9,s._ B.
_ Diptera—Bombylide: (2) Bombylius discolor, Mgn. s. C. Lepidoptera—
- (3) Anthocharis cardamines, L., s. ; (4) Pieris brassicae, L.; (5) P. napi, L., s. ;
(6) P. rape, L., s. ; (7) Rhodocera rhamni, L., s.

49, VIOLA CANINA, L. :-—

lq Visitors: A. Hymenoptera—Apide: (1) Bombus lapidarius, L. 9, s. ;
(2) Osmia rufa, L. ¢, s.; (3) O. fusea, Chr. 9,8. B. Diptera—Bombylide :
_ (4) Bombylius major, L.,s. C. Lepidoptera—Rhopalocera: (5) Pieris rape,
© L.,s.; (6) P. napi, L., s.

Cleistogamic flowers have been observed in many Violarice : in
_ V. mirabilis, L., by Dillenius; in V. pinnata, L., and V. montana,
_L,, by Linnzus; in V. elatior, Fr., V. pumila, var. lancifolia, Thor. ;
i] Y. odorata, L., bid V. canina, L., by Daniel Miiller; in Somidtum,
SS , by Bornouilli: I can add V. bicolor* to this list. In the
/ summer of 1859, I gathered some plants of this species at
Ramsbeck Waterfall, and placed them in a plate with water under
the shadow of a bush in my garden, to let the flowers expand ; the
plants, which I watched daily, grew well, and though no flowers
_ opened I obtained plenty of capsules with good seed. Cleistogamic
- flowers have been seen by Mr. T. H. Corry in V. silvatica, Fries.,
and in V. stagnina, Kit.; they are rare in the latter. Bennett has
observed cleistogamic flowers in Viola cucullata, Ait., V. silvatica,
V. floribunda, and V. sagittata, Ait. (79).

EVOLUTION OF COLOUR IN VIOLETS.

Various facts show that the flowers of the Violet were originally
yellow.

The smallest, most short-spurred of our Violas is V. biflora,
ae is visited by Diptera, and only exceptionally by short-lipped
es; its flowers are yellow. The smallest-flowered form of
_V. tricolor (var. arvensis) has whitish-yellow flowers. The large-
ia flowered V. tricolor, var. alpestris, shows all stages in the passage
; from yellow flowers to blue; many plants have flowers which are
| gyellow throughout, in others the flowers are yellow when they

1 VY. bicolor, Pursh., is a form of V. tricolor, var. arvensis.—Asa Gray, North
| American Flora,

122 THE FERTILISATION OF FLOWERS. [PART IIL. |

open, but change gradually to blue, and in others the change to
blue occurs immediately after opening, or even before.

The most specialised form, V. calcarata, is almost always blue,
but occasionally it reverts to the ancestral yellow colour (609).

— ee

Orv. POLYGALEZ.

ae

50. PotyGALaA comosa, Schk.—The structure of the flower
of P. vulgaris, which agrees in all essential points with that of
_ P. comosa, here figured, was first explained by Hildebrand (352).

The two lateral sepals (alw), which are large and coloured, —
render the flower conspicuous. The inferior petal (p’) is furnished

weit)
eet

Fic. 37.—Polygala eomosa, Schk.

1.—Flower in side view (the flower should naturally be horizontal). s, sepa!; p, petal; s’, one of —
the two lateral sepals which play the part of a corolla; p’, anterior petal, provided with digitate —
appendages, to which the insect clings.

2.—Flower, from below. ;

3.—Anterior petal, with the essential organs inclosed in it, from above. a, anthers; s, stigma,
which applies sticky matter to the insect’s proboscis passing over it ; 1; spoon-shaped end of the —
style, which receives the pollen issuing from the anthers. >

4.—Pistil, from above.

5.—Ditto, seen obliquely from above.

6.—Ditto, in side view.

7.— Anterior petal of a flower just about to expand, split to show the anther inclosed by it.

8.—The united anthers.

9.—An anther dehisced. po, pollen-grains.

at its apex with finger-like processes, which support the bee when
it alights. On the upper surface of this petal is a pouch with two —
valves, inclosing the essential organs; in it lies the spoon-shaped
style with its concavity upwards, and in this the anthers on both —
sides lie and shed their pollen; close behind its hollow extremity
the style bears a. viscid stigmatic lobe, bent sharply downwards,
An insect which tries to reach the honey secreted in the base
of the flower must, while clinging to the fimbriate processes —

parru.] THE MECHANISMS OF FLOWERS. 123

of the lower petal, thrust its proboscis between the two valves of
the pouch, and thus come in contact both with the pollen and with
the viscid stigma; the proboscis being thus rendered adhesive
_ carries some pollen with it out of the flower, and when it is drawn
out of the next flower in a similar manner it leaves some of this
pollen either caught by the stigmatic hook or adherent to the
_papille. Thus cross-fertilisation goes on regularly. In default
of insect-visits the stigmatic lobe curves over upon the pollen
~ accumulated in the “spoon,” and is thus self-fertilised.

On the Alps P. comosa is visited by Lepidoptera, but in Low
. Germany chiefly by bees (590, IL. ; 609).

i Polygala alpestris, Rehb., is visited by butterflies (609).

51. PoLYGALA VULGARIS, L, :—~

Visitors: A. Hymenoptera—Apide : (1) Bombus terrestris, L. 9, s., very
frequent ; (2) B. lapidarius, L. §, s.; (3) Apis mellifica, L. $,s. B. Lepid-
_ optera—(4) Polyommatus Eurydice, Rott. (Chryseis, W. V.),s. See also No.
590, II.

Polygala Chamebuxus, L.—The pollen is stored in a cup at
the end of the style, beside which is the sticky stigma-disc
_ The mechanism of fertilisation shows a certain resemblance to
that of Papilionacee. In both, the stamens and style lie in the
inferior part of a tubular horizontal flower, at the end of which
_ they bend upwards, and bear the anthers and stigma. Those parts
lying in the anterior part. of the flower are in both sheltered by a
carina formed of coherent petals, and emerge, or at least permit
_ the stigma and pollen to emerge, when the carina is pressed down,
as it is by every insect which obtains the honey in the legitimate
manner.

In Polygala Chamebuzus, as in Lotus and several other Papii-
- tonacece, it is not the anthers themselves that emerge when the
carina is depressed, but only part of the pollen which escapes ;
and after repeated depressions the stigma also emerges, and
cross-fertilisation is thus insured. A full description of this
interesting flower is given in my book Die Alpenbumen.

Polygala myrtifolia, L., has also, according to Delpino, a floral
arrangement comparable to that of Papilionacez. The two upper
petals represent the vexillum ; the lower one represents the carina,

and like it surrounds the reproductive organs and allows them to

124 THE FERTILISATION OF FLOWERS. [PART 111.

protrude on being pressed down by the weight of an insect:
serrate processes on the lower petal supply the place of ale. The
stamens cohere, forming a tube incomplete superiorly, where a
longitudinal split admits the insect’s proboscis to the nectaries

Fic. 38.—Polygala Chamebueus, L.

.

A.—F lower, from the side, natural size. a
B.—Ditto, front view (x 23). :
C.—Flower, after removal of the two alar sepals.

D —Ditto, from above. : ‘

E.—Ditto, from below (x 3).

F.—The two petals of the left side, separated from the inferior petal to which they naturally
cohere ; inner view (x 24). p3, superior petal; p?, lateral ditto, to which the filaments adhere.

G.—Bud in section after removal of the calyx (x 54).

H.—Full-grown flower in section (x 53).

J.—Base of flower, from the front, after removal of the superior sepal (x 7). 8’, superior, s*,
lateral, s3, inferior sepals; p’. inferior petal; p?, lateral ditto, completely united with p3, superior
ditto. The anterior part of the inferior petal serves as a carina, and rotates by means of a hinge,
a, upon the posterior part; b, cup at end of style; e, eutrance of the flower; ki, adhesive matter

on the stigma.

surrounding the base of the column. The flowers have the same

want of symmetry as those of Lathyrus and Phaseolus, and are

fertilised in the same way by Xylocopa violacea (178, 360).
Polygala has cleistogamic flowers, according to Kuhn (399).

parr] © THE MECHANISMS OF FLOWERS. 12

Or

Orv. CARYOPHYLLEZ; a. SILENEZ.

t 52. DIANTHUS DELTOIDES, L.—The stamens and petals spring
_ from an annular ridge of the receptacle encircling the stalk of the
_ ovary. This ridge bears on its inner border a yellow fleshy cushion
_ which secretes honey.

The pistil, the stamens, and the claws of the petals, which are
_ grooved to inclose the five inner stamens, are all closely surrounded
_ by the tube of the calyx, which is 12 to 14 mm. long, and a
little over 2mm. wide. A very narrow passage is thus left,

Fic. 39.—Dianthus delloides, L.

k 1.—Flower in first stage, viewed from above. Five anthers. covered with pollen, protrude from
the flower; two that have not yet dehisced are visible in the mouth of the tube.
1 2.—Pistil at close of the first stage, after all the ten anthers have dehisced. The two styles are
still twisted together,
__. 8.— Ditto, with the base of the petals and stamens, more magnified. a, nectary, surrounding the
base of the ovary as a fleshy ridge ; b, filaments; c, petals.
4 OE ead in second stage, after removal of the petals. Most of the anthers have fallen off,
st. stigma. ‘
5.—Pistil in second stage. The two styles have separated, but each retains its spiral twist, so
that stigmatic papille are turned towards all sides,

12 to 14 mm. long, leading to the honey, which is lodged between
the base of the stamens and the ovary. This passage is, in the
first state of the flower, so much blocked by the five inner
anthers, that the honey is only accessible to the proboscis of
_ Lepidoptera. The flowers are thus specially adapted for butter-.
flies; but their protruding anthers are taken advantage of by
pollen-seeking insects which act as subsidiary fertilisers.

Flowering begins by the petals, hitherto erect and involute,
spreading out horizontally; they are rose-red, with’ slightly in-
dented purple transverse lines near the base, and spreckled
externally to these transverse lines with small white spots, each

Aa Dy a

126 THE FERTILISATION OF FLOWERS. [PART III.

of which bears an upright hair. The limb of the corolla forms
a rosy circle, finely notched at its circumference, indented by five
deep incisions, and with its white centre surrounded by a purple
ring, outside which are scattered white spots (Fig. 39,1). As soon
as the flower has expanded and thus made itself attractive to the
eminently colour-loving butterflies, the stamens, with their anthers
coated all round with pollen, elongate and protrude one after
another in rather quick succession from the narrow tube, so that
every butterfly which inserts its proboscis must dust at least its
head with pollen. . The five inner stamens still remain in the tube,
rendering it too narrow for anything save the butterfly’s proboscis.
As the outer stamens wither, the five inner ones protrude in succes-
sion; but the two styles still lie twisted together within the tube
(Fig. 39,2 and 3). Only after the stamens have withered, and
have for the most part lost their anthers, do the styles elongate
and allow the stigmas to emerge from the flower; the stigmas now
spread apart, still retaining their spiral twist, so that from which-
ever side a butterfly comes to suck honey it cannot fail to touch
some part of the stigmatic papilla with its head.

Pollen-seeking insects, if they only resort to young flowers
whose anthers still have pollen, cannot act as fertilisers ; but they
may do so if they alight, as flies often do, upon older flowers with
mature stigmas, in which case they fly away again disappointed.

Self-fertilisation is completely prevented by the well-marked
dichogamy.

As normal fertilisers of Dianthus deltoides, | -have only observed
Pieris rape, L., and Satyrus Janira, L., but these I have noted
repeatedly. Several Syrphide, viz., Rhingia rostrata, L., Meli-
threptus scriptus, L., M. pictus, Mgn., and Helophilus pendulus, L.,
resort to the flower for the sake of pollen. I once noticed Rhingia
rostrata make a vain attempt to reach the honey; it plunged its

proboscis with a great effort into four flowers successively, but

as its proboscis is only 11 mm. long it never reached the honey;
in a short time it resigned the attempt, and betook itself to eating
pollen.

53. DIANTHUS CARTHUSIANORUM, L., has the same floral mech-
anism as the preceding species. In Thuringia I have observed
numerous visitors upon its flowers, consisting almost solely of

Lepidoptera,

(a) Rhopalocera: (1) Colias hyale, L., frequent ; (2) Rhodocera rhamni,
L., very ab.; (3) Polyommatus Phloas, L.; (4) Hesperia, frequent; ())

parr] THE MECHANISMS OF FLOWERS. 127

, Sphinges: (5) Macroglossa stellatarum, L. ; (6) Zygena carniolica, Scop. ;
(ce) Noctue : (7) Plusia gamma, L., ab.—The only other insect that I have
found on the flowers was a small Halictus, c.p. (Sept. 1871). See also No.

590, II.

| 54, DIANTHUS CHINENSIS, L.—I have seen flowers in my
garden repeatedly visited by Noctuw: (1) Plusia gamma, L.:
(2) Agrotis pronuba, L.; and (3) Brotolamia meticulosa, L.

_ Species. of Dianthus which I have observed on the Alps
| (D. superbus, L., D. silvestris, Wulf., and D. atrorubens, All.), are,
like the three preceding species, distinctly proterandrous, and
visited by diurnal Lepidoptera (609).

As in the proterandrous Alsinez, gynodicecism seems to be
widespread in the genus Dianthus. It occurs in D. superbus,

Fic. 40.—Gypsophila paniculata, L.
1.—F lower in first (male) stage, 2 Ditto in second (female) stage.

OD. carthusianorum, and D. deltoides, and the last of these shows
all gradations between hermaphrodite, gynomoneecious, and gyno-
dicecious flowers (607).

_ 55. GYPSOPHILA PANICULATA, L, —Although the corolla, when
fully expanded, is barely 4 to 5 mm. in diameter, the many
hundreds of flowers borne at once by a single plant, and the
_ abundant and easily accessible honey and pollen, attract numerous
insects. The power of self-fertilisation has been entirely lost.
_ The honey lies between the ovary and a green fleshy ring at
the base of the ten stamens; the cup at the bottom of which
it lies is 24mm. decp, and about the same in width at the
entrance. The honey is therefore accessible to short-lipped
| insects. First the five outer stamens, which alternate with the

128 THE FERTILISATION OF FLOWERS. [PART III.

petals, and afterwards the .inner five, ripen and protrude from —
the flower with an inclination outwards. They wither, curving —
outwards and downwards, and then the two short styles, hitherto —
bent inwards, elongate and protrude from the flower, diverging
from one another.

Visitors : A. Diptera—(a) Teeae : (1) Chrysops bib, Li, a4
(b) Syrphide: (2) Eristalis eneus, L.; (3) E. nemorum, L. ; (4) E. arbus-
torum, L., all three =e s. and fip.; (5) Syritta pipiens, Efe very ab. ;
(6) Ascia podagrica, F.; (7) Syrphus balteatus, Deg. ; (8) Melithreptus
pictus, Mgn. ; (9) M. teniatus, Mgn., alls. or fp. ; (¢) Muscide : (10) Pyrellia
gains L. ; (11) Onesia floralis, Rob. Desv. ; (12) Sarcophaga carnaria,

L;; (13) Lucilia silvarum, Mgn., all s.; (14) Anthomyia sp. ; (15) Sepsis.
B. Hymenoptera—(a) Evaniide : (16) Feenus jaculator, FE. ; a Formicide :
(17) several species ; (c) Sphegide : (18) Oxybelus uniglumis, L. ; (d) Vespide :
(19) Odynerus simplex, F, ; (20) O. parietum, L.,—all the Hymenoptera 8.

er a ee

Gypsophila repens, L., when flowering on sunny slopes of the —
Alps where insects are plentiful, is so distinctly proterandrous $
that spontaneous self-fertilisation is impossible. In less favourable —
localities it fertilises itself when not visited by insects (609).

Saponaria ocymoides, L., is distinctly proterandrous, and is
frequented by butterflies. It clothes sunny gravelly slopes in
the sub-alpine region with its handsome red flowers. I saw it ©
visited by thirty-three species of Lepidoptera, twenty-eight of —
which were butterflies, besides some humble-bees and Bombylide.

Saponaria vaccaria, L., is also fertilised by butterflies (590, 11.).

:
56. SAPONARIA OFFICINALIS, L.—This species is adapted for '
nocturnal Lepidoptera, as the foregoing species of Saponaria and ;
Dianthus are for the diurnal forms, The bright colour and elegant —
markings which attract butterflies are absent: the flowers are of —
one colour, and their scent is strongest in the evening. As in the —
other species, the honey lies hidden in the base of a long narrow —
tube. The calyx-tube is 18 to 21mm. long, but the claws of the —
petals stand a few millimetres higher. The flowers are markedly |
proterandrous. First, the five outer stamens protrude a few milli- —
metres from the flower, and dehisce immediately over its entrance;
afterwards they spread apart and leave the entrance free. The five
inner stamens now follow the same course, turning, as the others —
did, the pollen-covered surface of their anthers upwards. The —
styles are still inclosed within the tube, and are only slightly —
separated at their apices. When the inner stamens have withered,
the two styles grow up out of the flower, and spread apart, turning

PART III. | THE MECHANISMS OF FLOWERS. 129

their papillar inner surfaces upwards. The honey is secreted as in
Dianthus. I omitted to watch the flowers in their season, and can
only mention Sphinx ligustri, L., as a fertiliser; it visited the
flowers of this plant in my garden one evening during slight rain,
and sucked them with the usual rapidity of the hawk-moths. I
have also found Halictus morio, F. 9 collecting pollen on the
flowers (July 13, 1869).

| Silene rupestris, L., is proterandrous, and is visited by numerous
insects. It fahabits the same localities as Gypsophila repens,
and secretes and conceals its honey in the same way as that
species. Its flowers are equally conspicuous, but stand some-
what isolated on sparingly branched stalks; owing probably to
this circumstance, the power of self-fertilisation has not been
entirely lost (609).

Silene acaulis, L., ascends in the higher Alps to a height of
over 10,000 feet. Its low tufts closely studded with pink or
carmine flowers attract so many butterflies that as a rule the plant
has been able to dispense with the power of self-fertilisation.
Most tufts are exclusively staminate or pistillate, and only rarely
hermaphrodite and proterandrous. The latter in case of need fer-
tilise themselves. I have observed eighteen species of butterflies
on this flower (609).

As Silene acaulis is adapted for diurnal Lepidoptera, so S. inflata,
Sm., and S. nutans, L., are adapted for the nocturnal forms. I
found both on the Alps, visited in the evening by Noctuide, and
in the daytime. by bumble-bees. Silene nutans, L., is markedly
proterandrous. According to Kerner, each flower opens upon
three successive nights, on which the outer stamens, the inner
stamens, and the stigmas are exserted respectively. According to
Ricca (665), the flowers are sometimes diclinous by incomplete
development of the stamens, that is to say, gynodiecious. Silene
inflata. L., is tricecious and polygamous, like S. acaulis.

Lychnis flos-Jovis, L., is distinctly proterandrous; L. rubra,
Weigel, is tricecious and polygamous. Both have bright red
flowers, and are greatly frequented by butterflies on the Alps (609).
" Lyehnis Viscaria, L., is also adapted for cross-fertilisation by
butterflies (590, I1.).

: Lychnis alpina, L.—The proterandrous flowers are figured and

described by Axell (17).

57. LYcHNIS FLOS-cucuLI, L.—In regard to the position of
the honey, the flowers of this plant are intermediate between
K

130 THE FERTILISATION OF FLOWERS. [.111 PART

those of Stellaria, Cerastium, and Gypsophila paniculata, where
the honey is fully exposed, and Dianthus and Saponaria, where
it is only accessible to Lepidoptera. The insect-visitors include
bees, Lepidoptera, and some long-tongued flies. The nectaries,
which lie at the base of the stamens, cohere into a fleshy
ring surrounding the ovary. The calyx tube is 6 to 7 mm. long,
and bears teeth 3 mm. long, which stand erect and support
the claws of the petals. The honey is thus accessible to insects
which have a proboscis 9 to 10 mm. long; or which, with a pro-
boscis at least 6 mm. long, have strength enough to push apart
the claws of the petals, above the level of the calyx-tube ; or,
finally, to insects small enough to creep down the tube. .

The flowers are distinctly proterandrous. First, the five outer
anthers dehisce, while standing in the entrance of the flower and
having their pollen-covered sides turned towards one another. The
tube, though it permits a butterfly’s proboscis to pass easily down,
is so much obstructed by the anthers that the proboscis cannot fail
to be dusted with pollen. These stamens then elongate, and bend
outwards to lie in the intervals between the petals, while the inner
whorls take their place in the entrance of the flower. When these
wither, the five styles grow up, and the stigmatic papille, which
clothe the whole of their inner surfaces, attain their full develop-
ment. The styles reach to the entrance of the flower, and their
ends make 13 to 2 spiral turns, so that an insect cannot fail to
touch some part of the stigmatic surfaces with its proboscis in
thrusting it down into the flower.

The flowers are chiefly visited for the sake ot their honey; I
have only seen the hive-bee collecting pollen, and two species
of Syrphidze feeding on it.

Visitors : A. Hymenoptera—Apide : (L) Bombus Rajellus, Ill. 9 (12 to 13) ; —

(2) B. lapidarius, L. 2 § (10 to 14) ; (3) B. agrorum, F. ? (12 to 15); (4) B. ©
terrestris, L. § (7 to 9) ; (5) Apis mellifica, L. $ (6), ab., s. ande.p. ; (6) Osmia —
rufa, L. 2 (9) ; (7) Andrena nitida, K. 9 (3 to 4), they sought in vain for honey in
several flowers. B, Lepidoptera—(a) Rhopalocera: (8) Pieris brassicae, L.
(15); (9) P. rape, L., both ab. ; (10) Lycena Icarus, Rott. ; (b) Sphinges:
(11) Macroglossa fuciformis, L.; (12) Ino statices, L.; (c) Noctuew: (138)
Euclidia glyphica, L., very ab. C. Diptera—-Syrphide : (14) Rhingia rostrata,
L. (11 to 12), s.; (15) Volucella plumata, L., fp. ; (16) Syrphus pyrastri,
L., f.p.

I have observed the stamens of Z. flos-cuculi dusted with —
butterflies’ scales, and a Pieris rape which I caught upon the —
flower had a number of its pollen-grains among the hairs and —
scales on the forepart of its head.

é PART 111. | THE MECHANISMS OF FLOWERS. 131

58. LYCHNIS VESPERTINA, Sibth. (L. dioica, 8, L.).—The structure
of the flower has been thoroughly explained by Sprengel. Honey
is secreted by the lower, fleshy part of the (developed or abortive)
ovary, and lies at a depth of 20 to 25 mm. in fertile or pistillate
flowers, and of 15 to 18 mm. in barren or staminate ones. Both
_ kinds of flowers are much constricted near their upper end by the
_ calyx, and can only be forced open a little at the very brim by an
} insect’s head ; a thin proboscis at least 15 to 20 mm. long is needed
to reach the honey. The pure white flowers, which have no
guiding marks, expand in the evening, though they are not
completely shut by day. These characters taken together exclude
diurnal insects except such as come seeking pollen, and make the
- flowers so much the more attractive to crepuscular and nocturnal
Lepidoptera. According to Delpino (178, p. 161), the anthers ripen
two by two, a fact which I have not observed. A further remark of
Delpino’s, that the flowers stand horizontally, and let the stamens
emerge at their highest part, does not at all hold good of the
specimens in my neighbourhood, which have an almost perpen-
dicular position, as Sprengel figures them.

I have repeatedly seen Sphinx porcellus, L., visiting and cross-
fertilising the flower.

59. Lycunis Girmado, L., is, like Dianthus, adapted for fer-
tilisation by butterflies, and resembles Dianthus in regard to its
-nectaries, the position of its honey, its Se sean dichogamy,
‘and the order of development of its anthers (702, p. 254).

_ Visitors : A. Lepidoptera—Rhopalocera : (1) Hesperia silvanus, Esp., s. ; (2)
Pieris brassicee, L., s., very ab. B. Diptera—Syrphide : (3) Rhingia rostrata, L.,

I saw it insert its proboscis repeatedly, seeking in vain for honey. See also
No. 590, IL.

_ The species of Silene and Lychnis have a relation, according to
Dr. Buchanan White, to species of Dianthwcia (Noctwide) like that
ppaich exists between ‘Yucca and the Yucca-moth. The species of
Dianthecia fertilise Silene and Lychnis, and thereby make provision
for their larvae, which feed exclusively on the unripe seeds of these
plants. But Silene and Lychnis have many other insect-fertilisers

besides (773).

Orv. CARYOPHYLLEZ; b. ALSINE.

60. CERASTIUM ARVENSE, L.—The flowers resemble those of

_ &S. Holostea in the position of their nectaries, in the order of develop-

ment of the two staminal whorls and the stigmas, and hence also
K 2

132 THE FERTILISATION OF FLOWERS. [PART III.

in the likelihood of cross-fertilisation in case of insect-visits, and
of self-fertilisation in their absence. They are equally con-
spicuous, and are visited to about the same extent.

Visitors : A. Diptera—(a) Stratiomyide : (1) Stratiomys sp., s. (6) Empide:
(2) Empis opoca, F.; (3) E. rustica, Fallen, both very ab., s. ; (c) Leptide:
(4) Leptis strigosa, Mgn., s. ; (d) Syrphide : (5) Eristalis nemorum, L. ; (6) E.
arbustorum, L. ; (7) E. sepulcralis, L. ; (8) Syritta pipiens, L., all four ab.,
s.; (9) Platycheirus manicatus, Mgn., ab.,s.; (10) Syrphus, sp., s.; (11)
Melanostoma mellina, L., s. ; (e) Muscide : (12) Sepsis ; (13) Anthomyia etiva,
Mgn.,s. B. Hymenoptera—Apide: (14) Andrena argentata, Sm. 9, s. ; (15)
A. albicans, K. 9, s. ; (16) Halictus, ? (the size of H. nitidiusculus)s. C. Cole-
optera—Staphylinide : (17) Omalium florale, Pk. D. Thysanoptera: (18)

Thrips, frequent in the base of the flower. E. Lepidoptera—(19) Polyom- —

matus Phloeas, L., s. See also No. 590, 11., and No. 609.

Fia. 41.—Cerastium arvense, L.

1.—Flower in first stage. The outer whorls of anthers are covered with pollen, the inner are not
yet full grown ; the styles are curled inwards.

2.—F lower at the end of the third stage. The outer anthers are in part fallen off, and in part —

withered ; the inner are still sparingly coated with pollen; the stigmas are mature.

61. CERASTIUM TRIVIALE, Link, has smaller flowers and fewer :
insect-visitors ; accordingly it is less markedly proterandrous than —

C. arvense. It produces seed by self-fertilisation in the absence of
insects (Axell, 17).

Visitors : Diptera—(a) Syrphide: (1) Syritta pipiens, L., s. and fp. ;
(b) Empide: (2) Empis livida, L., s.

62. CERASTIUM SEMIDECANDRUM, L., has still smaller flowers

and is still less frequently visited than the preceding species; it is —

still less distinctly proterandrous, and fertilises itself regularly in
absence of insects. |
As in Stellaria media, the inner honeyless stamens are usually

abortive, but remains of their filaments, sometimes attaining half _

the length of the outer stamens, frequently remain. When the
anthers dehisce, they occupy the middle of the flower, and the
stigmas still lie close together, though their tips are bent outwards
and easily receive pollen. Later, the anthers pass outwards, the
stigmas lengthen slightly and spread out, turning their imner

PART III.] THE MECHANISMS OF FLOWERS. 133

surfaces, which are covered with long papille, upwards. An insect
visiting a young flower dusts itself with pollen, and also applies
pollen from the same or from another flower to the tips of the
stigmas; in an older flower it is likely to dust the outspread
_ stigmas with pollen from another flower ; in the absence of insects
the stigmas as they curve outwards come in contact with the
anthers still covered with pollen.

Visitors: A. Diptera—(a) Syrphidw: (1) Rhingia rostrata, L., s. (May
_ 10, 1870); (b) Muscide: (2) Pollenia vespillo, F. ; (3) P. rudis, F., both
_ s, and inserting the proboscis three to five times in each flower (April 17, 1871).
_ B. Hymenoptera—Apide : (4) Apis mellifica, L. $,—I saw (April 3, 1871)
the honey-bee in great numbers flying over a bare field of C. semidecandrum,
sucking the tiny flowers by dipping its proboscis once into each.

Cerastium viscosum, L., has cleistogamic flowers (40). >

63. MALACHIUM AQUATICUM, Fries.—The flowers of this plant
are more conspicuous than those of Cerastiwm triviale and C. semt-
decandrum, but less so than those of C. arvense and Stellaria
Holostea ; in the same intermediate position stands the amount of
its insect-visits and its floral arrangement, which favours both cross-
and self-fertilisation. The flower is proterandrous, and in absence
of insects the ends of its outspread stigmas come in contact with
the pollen-covered anthers. The styles vary in number from three
to five, the latter number being most frequent, so that Malachiwm
here probably resembles the common ancestors of Cerastiwm and
Stellaria.

Visitors : A. Diptera—(a) Syrphide: (1) Helophilus lineatus, F. ; (2) Eristalis
arbustorum, L. ; (3) Syritta pipiens, L. ; (4) Ascia podagrica, F., all ab., s. ;
| (b) Muscide : (5) Anthomyia sp., s. B. Coleoptera—Nitidulide : (6) Meli-
gethes, ab., Lh. OC. Thysanoptera: (7) Thrips, very freq. D. Hymenoptera
| —Apide: (8) Prosopis communis, Nyl. 9, s. ; (9) Pr. hyalinata, Sm. 2, s. ;
(10) Halictus sexnotatus, K. ¢, s.

64. STELLARIA GRAMINEA, L.—The nectaries surround the bases
of the five outer stamens as green, fleshy swellings. The flowers ©
exhibit three stages, which, however, merge one into another. In
the first period, the five outer stamens curve in towards the middle
of the flower, and their anthers dehisce widely, covering them-
‘selves all round with pollen; the inner stamens are meanwhile
bent outwards, and their anthers are still closed. The styles are
not yet fully developed, and are curved inwards with their papillar
surfaces directed downwards. ‘The five inner stamens dehisce
before the other five have withered, but still remain bent farther
outwards; this marks the second stage. As these inner stamens

134 THE FERTILISATION OF FLOWERS. [PART III.

wither and shrivel up, the styles rise up, and spread outwards
turning their papillar surfaces upwards, and curving their ends,
also papillar, outwards and downwards (third stage). Every insect
which is not too small, whether it alights in the middle of the —
flower or on one of the petals, must, to reach the nectaries,
come in contact with pollen in younger flowers or with the —

ee

Fic. 42.—Stellaria graminea, L.

1.—Flower in first stage. The five outer anthers are covered with pollen, and are bent inwards,

2.—Flower in last stage. All the anthers are empty and shrivelled. The styles are spread out
above the stamens, and are recurved, turning their papillar surface upwards.

a’, outer whorl of anthers ; a?, inner whorl; », nectary,

stigmatic papille in older ones. In default of insect-visits, the
stigmas as they continue to curve outwards come in contact with
the pollen-covered anthers. Insect-visits are scarce, as the incon-
spicuousness of the flowers would lead us to expect. I have only
once found Volucella bombylans, L. (Syrphide), sucking honey on
the flowers.

vi onal - Vs 7 ’
es 7 ’
ee ee ee ee

PART II, | THE MECHANISMS OF FLOWERS. 135

65. STELLARIA HoLostTEA, L.—The arrangement of the flower
resembles that of S. graminea; but the flowers are larger and
more conspicuous, the nectaries are yellow, confined to the outer
side of the outer stamens, provided above with a honey-secreting

_ pit,and yielding more abundant honey. The three stages are more
_ clearly marked off than in S. graminea. In the first stage the outer
_ stamens, in the second the inner ones, stand close round the centre
_ of the flower, turning their pollen-covered surfaces more or less
_ upwards,—the other five being in each case bent out of the way.
In the first period the stigmas are bent inwards (as in 1, Fig. 42),
in the second they stand erect but with their papillar sides turned
_ inwards towards each other, in the third they are spread out (as in

2, Fig. 42), while the anthers have mostly fallen off or remain as
withered scales attached to the corolla.

In flowers which I kept‘in my room however, self-fertilisation
often took place, for the ends of the stigmas, as they spread out-
wards, often came in contact with the inner anthers still bear-

Ing their pollen, and moreover pollen often fell wpon other parts of

the stigmas.

Visitors : A. Diptera—(a) Empide : (1) Empis tesselata, F. ; (2) E. opaca,
F., both frequent, s. ; (b) Syrphide : (3) Rhingia rostrata, L., ab., s. and f.p.,

_ standing on a petal and applying the proboscis now to the base of the flower,
_ now to the anthers ; (4) Eristalis arbustorum, L., s. and fp. ; (5) Platycheirus

peltatus,Mgn., do. ; (6) Syrphus ribesii, L., do., ab. ; (ec) Muscidae : (7) Hydro-

tea dentipes, F., s. B. Hymenoptera—(a) Apidae: (8) Apis mellifica, L.%,
ab. and persistent, s. (May 27, 1871); (9) Nomada flavoguttata, K. 9 ;
- (10) N. ruficornis, L.? ; (11) Andrena cineraria, L. 9 ; (12) A. parvula, K. 9,
the last four s.; (13) Halictus cylindricus, F. 2, fip.; (b) Tenthredinide -
_ (14) Cephus pallipes, Kl, s. C. Coleoptera—(a) Nitidulide: (15) Meli-
_ gethes, ab., s.; (b) Cdemeridw: (16) CEdemera virescens, L. (Tekl. B.)
_ D. Lepidoptera—Rhopalocera: (17) Pieris napi, L., s. E. Thysanoptera—
_ (18) Thrips, ab. See also No. 590, 1.

66. STELLARIA MEDIA, Vill.—The flowers are less conspicuous

than the two preceding species, and, since they appear at all times

of the year except.in severe frost, they are for a great period

shut out from insect-visits ; they therefore depend largely on‘ self-

fertilisation. Accordingly they differ considerably in their arrange-

ment from the former species. Of the ten stamens, there are
almost always some, usually five to seven, abortive ; and, on. the
_ whole, I think that the number of abortive stamens is greater the

colder the time of year. The five inner stamens are always reduced,

and often disappear completely ; the five outer ones, which bear the

i.

136 THE FERTILISATION OF FLOWERS. [PART III.

honey-glands on the outer side of their bases, only show signs of
abortion when the inner series are all abortive; at most, two of
them disappear, but the corresponding glands always remain.

In sunny weather so much honey is secreted that the five
drops are easily seen by the naked eye. The stamens, especially
when their number has been reduced to three, come to maturity in
slow succession. Immediately after the flower opens, the first
anther begins to dehisce, and the stigmas still stand erect with their
papillar sides turned inwards; but their tips are already slightly
outspread. While the second and third stamens dehisce, the

stigmas expand fully, and turn the whole of their papillar surfaces _

upwards. So from the beginning cross-fertilisation and self-ferti-
lisation, in the event of insect-visits, are both equally likely; in
absence of insects the stigmas regularly fertilise themselves by
coming in contact with the anthers. This self-fertilisation is
undoubtedly efficient, for S. media produces abundant seed in
winter when no insects are about, and in long-continued rainy
weather.

Stellaria media has the greatest chance of cross-fertilisation in
early spring, for before that time no insects are on the wing, and
afterwards many more attractive flowers compete with it. My own
observations confirm this.

A. Hymenoptera—Apide : (1) Andrena Gwynana, K. 9, s. and c.p. (April
11, 1869) ; (2) A. albicans, K. g, s. (do.) ; (3) A. dorsata, K.?,s. (do.) ; (4) A.
parvula, K.g,s. (April 21, 1869) ; (5) A. albicrus, K. ¢,s. (do.) ; (6) Osmia
rufa, L. ¢, s. (April 17, 1869). B. Diptera—(a) Syrphide: (7) Syritta
pipiens, L., s. (May 27, 1870) ; (6) Muscide: (8) Chlorops circumdata, Mgn.,
diligently s. (March 9, 1872) ; (9) Musca corvina, F., do. ; (10) M. domestica,
L., do. C. Thysanoptera—(11) Thrips, dusted with pollen, creeping in and
out of the flower (April 30, 1868). See also No. 590, 1.

Stellaria cerastoides, L., is homogamous and is visited by
Diptera. It fertilises itself in case of need (609).

67. ARENARIA (M@HRINGIA) TRINERVIA, L.-—At the base of
the expanded flower, on the outer side of the base of each outer
stamen, we see a rather large drop of honey. The fleshy swellings
at the bases of these stamens, which act as honey-glands, are so
strongly developed and extend so far on either side, that they
coalesce, and the five together form a ring round the ovary; from
this ring the five inner stamens (which alternate with the others,
and stand opposite to the petals) seem to spring.

When the flower opens, the stigmas are already separated and
turn their rough papillar surface upwards, while the anthers remain

parti] © THE MECHANISMS OF FLOWERS. 137

closed. In the second stage, the anthers of the outer and longer
stamens dehisce ; in the third stage those of the inner and shorter
stamens, the stigmas still remaining fresh. The flowers are thus
_ proterogynous with long-lived stigmas. Cross-fertilisation is likely
to occur not only in the first stage, but also in the later stages, since
an insect on alighting will probably touch the stigmas before the
ik stamens.

i In several cases I have found the outer stamens so much

bearing tiny shrunken anthers devoid of pollen. Here apparently
the time between the ripening of the stigmas and that of the
_ stamens was lengthened; and hence the chance of cross-fertilisation
increased. In default of insect-visits, self-fertilisation is attained by
_ the stamens (both outer and inner) bending inwards, still covered
with pollen, and coming in close contact with the stigmas.
I found asmall beetle, Olibris affinis, Sturm, one of the Phalacride,
licking honey on this flower.
Arenaria (Mehringia) muscosa, L., is fertilised by Syrphide
(609).
Honkeneja (Ammodenia) peploides, Ehrh., is polygamous (Warm-
ing, 762).
Sagina nodosa, K. Meyer, is proterandrous (17, 38) and visited
by Anthrax (609).
The following additional species are discussed in my <Alpen-
blumen :—Arenaria biflora, L.; Alsine recurva, Whinb.; A. verna,
Bartling; Cherleria sedoides, L.; Cerastium adpinunn, BG,
_ latifolium, L.

REVIEW OF THE ALSINEZ.

a he cmap

_ The foregoing Alsinez are all more or less dichogamous, and are
mostly proterandrous in various degrees, Arenaria Trinervia being
_proterogynous. Dichogamy is the more marked the more con-
' spicuous the flowers, and the more abundant the visits of insects.
‘Self-fertilisation is totally excluded in none of the above-mentioned
forms, and is the better insured, the more inconspicuous the flowers
are, and the more scanty the insect-visits either from that cause or
on account of the unfavourable time of year. The insect-visitors are
very various, on account of the accessible position of the honey, but
_ consist chiefly of flies and the less specialised bees.
__ Most of the above remarks hold good also for the species which

138 THE FERTILISATION OF FLOWERS. [PART ITI.

I have observed on the Alps. Alsine verna, Jacq., Cherleria sedoides,

L., and Mehringia muscosa, L., are so markedly proterandrous, that

spontaneous self-fertilisation can only rarely and exceptionally take —

place in them. Arenaria biflora, L., and Cerastiwm latefolium, L.,

also ripen their anthers before their stigmas, but, im default of —

insect-visits, fertilise themselves.

I found Stellaria cerastoides, L., to be homogamous, in which |

respect it stands alone among the higher Alpine Alsinez.

As bees are scarce in the higher regions of the Alps, Diptera —
take their place as cross-fertilisers of the Alsine more than in the —
lower grounds, and were alone observed on several of the above-_—

mentioned species (600).

Dr. T. Ludwig of Greiz has recently made the interesting

discovery that most if not all of the distinctly proterandrous
Alsinez are also gynodicecious; and that the plants with small and

purely pistillate flowers are chiefly in bloom at the beginning of the ©

flowering-period of the large-flowered hermaphrodite plants. So
these subsidiary pistillate plants make up for the preponder-
ance of the staminate condition in the hermaphrodite flowers at
that time (426, 427).

Orv. CARYOPHYLLEZ; c. POLYCARPEZ.

Polycarpon tetraphyllum, L., has cleistogamic flowers (Batalin,
40).

REVIEW OF THE CARYOPHYLLE2.

The Caryophyllee exhibit an interesting series of gradations

in the concealment of their honey, while the anthers remain
throughout fully exposed ; a comparison of their insect-visitors will
thus show what effect differences in the situation of the

honey produce.

The flowers of Alsinew, and the short and wide flowers of |
Gypsophila paniculata, which all expose their honey freely, are
chiefly frequented by flies and by a few beetles and other short-—

lipped insects; when visited by bees, it is either by the least
specialised forms (Prosopis, Halictus, Andrena) or by the most
specialised and most diligent (Apis). Lychnis flos-cuculi, whose
honey is hidden 9 to 10 mm. deep, and beyond the reach of short-
lipped insects, is almost exclusively visited by highly specialised

| PART 111. | THE MECHANISMS OF FLOWERS. - 139

bees and by Lepidoptera, one drone-fly, Rhingia, coming also to
share the honey. The benefit which results from and has brought
about the lengthening of the tube in Lychnis flos-cuculi lies in the
fact that, by excluding short-lipped insects from the honey, a larger
_ number of insects with long proboscides are tempted to come, and
these, requiring more food, are more diligent in their visits and in
their work as cross-fertilisers. That the exserted anthers can be ,
robbed by pollen-eating flies and pollen-collecting bees is scarcely
adisadvantage; for the pollen is seldom completely removed, and
_ these pollen-seeking insects act as subordinate fertilisers.

When the passage to the honey is still further lengthened and
__harrowed, as in the species of Dianthus, Saponaria, and Lychnis,
even bees are excluded and Lepidoptera only can gain access. For
this result to be advantageous we must suppose that the visits of
Lepidoptera are the better insured by exclusion of other insects.
Exposure of the anthers is as little injurious here as in Lychnis
_ flos-cuculi. As the honey gets more deeply concealed, and access
more strictly limited to butterflies, we find pari passu among the
| Caryophyllee increasing development of sweet scents, bright red
colours, fine markings round the entrance of the flower, and
{ indentations at the circumference. All these characters, which are
so attractive to us, seem to have been produced by the similar
tastes of butterflies.

Orv. HYPERICACEZ.

68. HypERICUM PERFORATUM, L.—The flowers, from their size
and bright colour, and from numerous plants being usually
associated together, are very conspicuous, and attract many insects
seeking both honey and pollen; they however contain no honey,
' and possess no contrivances to insure cross-fertilisation. The
large production of pollen, and the capability for self-fertilisa-
‘a en compensate in part for these disadvantages. ‘The numerous
amens, usually over eighty in number, radiate from the bottom
a of the flower in three groups, which are united at the base; the
anthers are directed upwards and dehisce in rather. aaaine
centrifugal succession, covering themselves with pollen. The
three styles also radiate outwards, so that their terminal stigmas,
which are developed simultaneously with the anthers, come
to stand on a level with the anthers in the intervals between
the groups of stamens. Since these. staminal bundles usually
touch one another, and sometimes interlock slightly at their

Re
| <*>

140 THE FERTILISATION OF FLOWERS. [PART III.

margins, the stigmas come into close relation or even immediate
contact, with the pollen-covered anthers. Insects alight as a rule
upon one of the five outspread petals, and then find that the
easiest course towards the anthers lies between two groups of
stamens; they thus frequently come in contact in the first
instance with a stigma, and may thus cause cross-fertilisation.
On the other hand, they often come in contact first with some
of the anthers and thus occasion self-fertilisation. Later on, the
petals and stamens draw together towards the axis of the flower,
thus bringing anthers and stigmas in contact with one another,
and insuring self-fertilisation.

Although the flowers have only pollen to offer, they attract
a good many honey-seeking insects, which fly away again after a
vain search for honey, and after sometimes even boring into the
tissue at the base of the flower. I have noticed the following —
insects on the flowers of H. perforatum :—

A. Hymenoptera—(a) Apidae: (1) Bombus agrorum, F. 9, ¢p.; (2) B.
terrestris, L. %, cp. ; (3) Saropoda bimaculata, Pz. ?, s. ; (4) Andrena dorsata,
K.9,cp.; (5) A. coitana, K. 9, cp. ; (6) Nomada lineola, Pz. 2,8. ; (7) N.
lateralis, Pz. 9,8; (8) Prosopis armillata, Nyl., fip.; (b) Tenthredinide :
(9) Tenthredo sp., vainly seeking honey. B. Diptera—(a) Bombylide:
(10) Argyromeeba sinuata, Fallen, vainly seeking honey ; (11) Bombylius
canescens, Mik., s.; (b) Empide: (12) Empis livida, L., s., the two last
obviously bored into the base of the flowers; (c¢) Syrphidw: (13) Eristalis
nemorum, L, ; (14) E. arbustorum, L. ; (15) E. tenax, L. ; (16) E. sepuleralis,
L. ; (17) Syrphus balteatus, Deg. ; (18) S. ribesii, L., all six species very ab. ;
(19) Helophilus pendulus, L.; (20) H. trivittatus, F.; (21) Melanostoma —
mellina, L. ; (22) Melithreptus scriptus, L. ; (23) M. pictus, Mgn. ; (24) Ascia
podagrica, L., all these Syrphide were diligently collecting pollen. C. Lepi-
doptera—Rhopalocera : (25) Hesperia silvanus, Esp. ; (26) Satyrus Janira, L.
both thrust their proboscides to the base of the flower, but were obviously
groping about for honey and unable to pierce the necfariferous tissue. D, Co-
leoptera—Chrysomelide : (27) Cryptocephalus sericeus, L., devouring both
stamens and pollen. See also No. 590, 11.

Hypericum tetrapterum, L., is visited by pollen-collecting bees
and pollen-feeding flies (590, I1.).

Hypericum hirsutum, L.—The structure of the flowers for the most —
part resembles that of H. perforatum, but they are smaller and
have far fewer stamens, only seven to nine in each bundle. The
plants bear fewer flowers, and stand more isolated, which greatly
restricts the number of insect-visitors; in fact, I have never
succeeded in observing H. hirsutwm visited by any insect. The
bundles of stamens, on account of the small number they contain,
are separated by wider intervals, in which the styles pass outwards

varrut.] THE MECHANISMS OF FLOWERS. 141

_ without the stigmas ever comimg im contact with the anthers in
an expanded flower. But when the flowers close up, on fading,
_ self-fertilisation abnay® takes place, and seems to result in full
_ productiveness.

_ Hypericum miiidaliouiacs, L., is intermediate between J.
| perforatum and H. hirsutum in regard to the size of its flowers
and the number of their stamens. Each flower contains between
_ fifty and sixty stamens, in bundles consisting of from sixteen
it to twenty-two. In the expanded flower, I have never seen the
stigmas in immediate contact with the anthers; though such
; contact. regularly occurs ultimately, when the mart of the flower
_ draw towards the centre. The want of symmetry in the petals
is noteworthy; it occurs also in other species of Hypericum, but
not so strongly marked. Each petal is more expanded on one

4
€
a Fic. 43.—Hypericum hirsutum, L.
2 Flower, seen obliquely from above, a, a, a, the three stigmas.

| “side than on the other, and the broader side bears notches from
its apex to about the middle, a black gland lying in each notch.
3 broad and glandular side is sometimes on the right and
_ Sometimes on the left, but is on the same side in all the petals
| cof one flower. The flowers are visited by flies, which feed on the
"pollen (590, 1.)
Hypericum humifusum, L., has smaller flowers and fewer
_ stamens (three to five in each group) than any of our other
) species. The anthers only come in contact with the stigmas as
the flower closes up.
_ I have observed no insects on this species, or on #,
quadrangulum.

In all the above-mentioned species, the grouping of the
stamens in three bundles and the position of the styles between

142 THE FERTILISATION OF FLOWERS. [PART III.

them increase the chance of cross-fertilisation ; rendering it likely
in spite of the great number of anthers, that an insect on alighting
will touch a stigma first, though self-fertilisation is also very
probable. In all, self-fertilisation occurs in default of insect-
visits, and is without doubt the usual mode of reproduction in
the less conspicuous forms. :
Cratoxylon formosum has dimorphic flowers (167, 213).

Orv. MARCGRAVIACE LZ.

In this order bracts secrete honey and make the flower
conspicuous by their bright colours. They have accordingly
the most various forms (spurs, spathes, etc.), and are of as much
importance to the plant as petals usually are. Delpino bases a

new subdivision of the order upon the modifications of the bracts. —

The flowers are proterandrous.
In Marcgravia nepenthoides there occurs beneath a wreath of
pendulous flowers a group of honey-secreting cups. They attract

insects, which in turn attract insectivorous birds, and these, while —
feeding on the insects sitting upon the nectar-cups, touch and —

cross-fertilise the flowers above (56).

An interesting paper on Marcgraviacez and their Nectaries,
with fine figures, was contributed by Ludwig Wittmack to
Kosmos, vol. v., 1879 (784.)

Orv. MALVACE LZ.

MALVA SILVEsTRIS, L., and M. rotrunpirot1A, L.—These ©
species often occur together, and flower side by side for months ~

at atime. In the struggle for existence, IZ. rotwndifolia has the

advantage in being content with poorer soil, in the appearance of

its flowers from one to several weeks earlier, and in the possibility

of regular self-fertilisation; JZ silvestris, on the other hand, in~
its more vigorous growth, and much greater attractions for ~
insects. These advantages seem to balance one another, for, —
about Lippstadt at least, both species grow together in equal

abundance,

In both species, a pyramidal group of anthers occupies the
middle of the young flower, and surrounds the stigmas which are
still unripe and folded together; later on, the stigmas become
exserted and radiate outwards. Honey is secreted in five pits
between the bases of the petals, and protected by hairs, and insects

PART III. ] THE MECHANISMS OF FLOWERS. 143
| eeking it must wipe off pollen from the anthers in young flowers
‘and apply it to the stigmas in older ones. In Malva silvestris,
which attracts insects by the larger size and brighter colour of
its flowers, and receives very numerous visits, the ends of the
f laments, before the stigmas are mature, curl outwards so far
that spontaneous self-fertilisation is impossible. MJ. rotundifolia,
whose much smaller and paler flowers attract few insects, regu-
arly fertilises itself in default of insect-visits, for its anthers
emain extended in such a position as to be touched by the
papillate sides of the curling stigmas. (Fig. 44, 5).

The following lists of insects which I have observed dur-
‘ing four summers upon the two forms, show how great is the
difference in this respect between them.

i

\ i),

Fig, 44.

_1—4.—Malva silvestris. 1, essential organs from a bud; 2, ditto, in the first stage of the flower
ditto, between the first and second stages ; 4, ditto, in the second stage.
i 5. —Malva rotundifolia in the act of self-fertilisation,

69. MALVA SILVESTRIS, L. :—

Visitors: A. Hymenoptera—(a) Apidw: (1) Apis mellifica, L. §,s., very
/ ab. ; (2) Bombus lapidarius, L. 2, ab. ; (3) B. hortorum, L 9 ; (4) B. silvarum,
L. 2; (5) B. agrorum, F.$; (6) Cilissa hamarrhoidalis, F,? ¢, freq. ;
(7) Andrena parvula, K. ¢; (8) A. Gwynana, K. 2; (9) A. fulvicrus, K. 9° ;
| 10) Halictus maculatus, Sm. 9; (11) H. albipes, F. 2 ; (12) H. morio, F. ? ;
13) H. Smeathmanellus, K. 9; (14) H. zonulus, Sm. ¢; (15) Nomada late-
Talis, Pz. 2; (16) Osmia enea, L. ¢; (17) Megachile Willughbiella, K. ¢. ;
(18) M. ligniseca, K. ¢; (19) Coelioxys simplex, Nyl. 9 ¢; (20) Chelostoma
-campanularum, L. ¢,—all these twenty species though always dusted with
| pollen, never collected it, but came for honey only ; (21) Ch. nigricorne, Nyl.
. 6 @, very ab., both s. and ep., this is the only species which I have seen
collecting the pollen ; (22) Prosopis hyalinata, Sm. ¢; (23) P. communis,
Nyl. 6 2, freq.; (24) P. signata, Schenck, ¢; (25) P. pictipes, Nyl. ¢;
(26) P. dilatata, K. ¢, all sucking ; (b) Ichneumonide : (27) various species,—
Tam unable to say whether they succeeded in reaching the honey. B. Diptera
-(a) Stratiomyide : (28) Sargus cuprarius, L. (seemed to derive no advantage

| =
4
\

%

144 THE FERTILISATION OF FLOWERS. [PART III.

from the flowers, though attracted by them; (b) Syrphide: (29) Rhingia
rostrata, L., s., ab. C. Lepidoptera—(30) Pieris rape, L.,s. D. Coleoptera—
(31) Haltica fuscicornis, L., in the flowers. See also No. 590, 11.

70. MALVA ROTUNDIFOLIA, L. :—

Visitors: Hymenoptera—Apide: (1) Apis mellifica, L. $; (2) Bombus
agrorum, F. §; (3) Anthophora quadrimaculata, F. ¢; (4) Halictus morio,
F, g,all sucking. See also No. 590, 11.

The following observation shows that even Malva silvestris is
not perfectly adapted to its conditions of life. In the afternoon,
when the flowers begin to close, I have very often seen hive-bees —
clambering up the outside of the calyx of closed but still fresh —
flowers; thrusting the proboscis past the sepals, they emptied the
nectaries from outside. Sometimes I have even seen bees, after
sucking several closed flowers in this manner, perform the same
operation on the next open flower. Thus the flowers of Malva
silvestris have not sufficiently secured their honey from plunder.

71. Marva Atcrea, L.—The flowers standing on longer stalks, —
and expanding their rosy petals to a diameter of 40 mm., —
are still more conspicuous than those of J. silvestris. Self-
fertilisation is obviated by the same arrangement as in I. silvestris,
and insect-visits are probably at least equally numerous. I have
only once, in scarcely favourable weather, observed a few specimens
in flower (July 13, 1868).

Hymenoptera—Apide: (1) Apis mellifica, L.$, very ab., s. covering |
itself with pollen; (2) Cilissa heemorrhoidalis, F. 9, s ; (3) Halictus
cylindricus, F.?,s. See also No. 590, 11. |

72. MALVA MoscuaTA, L.—The flowers are as distinctly pro- —
terandrous as those of the three foregoing species. According to a —
sketch which I made in 1867, the ends of the filaments curve down-
wards on the withering of the anthers; the stigmas spread out
above them, apparently obviating self-fertilisation. However, at —
that time I did not pay particular attention to cases where self-
fertilisation occurs in default of insect-visits.

Visitors: A. Hymenoptera—A pide : (1) Apis mellifica, L. $, s.; (2) Che-
lostoma nigricorne, L. ?, s.; (8) Andrena Coitana, K. ¢, s. (Sld.). B,

Diptera Bombylide : (4) Systoechus sulfureus, Mikan s. (Sld.), C. Lepidop-
tera : (5) Hesperia silvanus, Esp., s.

Delpino mentions Xylocopa violacea as a visitor of the Malvacew
(172). Dr. Ogle says (631) that in many Malvacee anthers

“Part 111] THE MECHANISMS OF FLOWERS. 145

and stigmas ripen together, and self-fertilisation takes place
regularly; he says that in these forms no nectaries are present,
‘since the aid of insects is not required. Unfortunately he does
‘not name the species to which he refers,
_ Anoda hastata, Cav.—Hildébrand figures and describes the
proterandrous flowers. In the first stage the ripe anthers are
erect and the stigmas are folded down, while in the second the
stigmas project above the anthers (351).
Gossypium herbaceum, L., has floral and extra-floral nectaries.
‘It is visited by Ruby-throated Humming-birds, and by numerous
‘insects (730).
i Abutilon, Girtn—My brother Fritz Miiller has performed
many experiments on this plant at Itajahy, with the following
“results :—
(1) All the species of Abutilon growing there, and their
hybrids are barren (with perhaps one exception) when fertilised
with their own pollen.

(2) In those species which are unproductive with their own
pollen, the pollen of their near relations (the parent-plants or
their offspring) is less efficient than pollen from more distantly
related or unconnected plants.

(3) The application of pollen from several different species
ives a greater yield of seed than pollen from a single other
species Buty,

(4) The simultaneous application of pollen of two species
ways produces seedlings of two kinds: not as in the experi-
ents of Koelreuter and Giirtner on other plants, where the

i
ic
a
a
Simultaneous application of two species of pollen always produced
8 seedlings of one kind only.

(5) Among hybrids of the genus <Abutilon, there is more or
less complete sterility between nearly related. individuals—between
parent- -plants and their offspring, between offspring of the same.
parents, or even between plants which have only one parent in
common.

By considering from a common point of view the diminution
fertility in too close interbreeding and in the production of
hybrids, Fritz Miiller arrives at the following law :—Every plant,
| j0 produce vigorous and prolific offspring, requires a certain degree
of difference between the male and female principles hil
“coalesce ; and when this amount of difference is too great or
too small, i.c. when the parent-plants are too distantly or too

- closely related; the productiveness falls off. Further, the greater

e.
¢

i

146 THE FERTILISATION OF FLOWERS. [PART III,

the amount of difference between the sexual principles that is
requisite for full productiveness in a certain plant the greater

i

chance will there be — ceteris paribus—of that plant proving

fruitful when crossed with much more distant relatives. Thus
species in which individuals are quite sterile to their own pollen,
and more or less unfertile to pollen from closely related indivi-

duals, will in general be specially likely: to form hybrids with other —

species. (Compare Abutilon, Lobelia, Passiflora, Oncidiwm) (558).

The natural fertilisers of Abutilon at Itajahy are humming- -

birds, which perform their work so diligently that, as we have
seen, the power of reproduction on self-fertilisation has been
dispensed with.

Pavonia hastata, Cav., has cleistogamic flowers without
nectaries (318).

Goethea coccinea, according to Delpino, is proterogynous with
long-lived stigmas. The tetraphyllous involucre renders the
flower conspicuous; the honey is secreted in five glands at the
base of the urceolate calyx, and is sheltered by the corolla.
Delpino supposes bees or humming-birds to be the fertilisers

(177, 351). |

Orv. STERCULIACE.

Melochia parvifolia, H. B. and K. (Caracas), is, according to
Ernst, dimorphic and heterostyled (225).

Orv. TILIACE ZL.

73. TILIA EUROPHA, L.—Sprengel has fully described the
flower of the lime: its proterandrous condition, which he
overlooked, was noted by Hildebrand (356).

The honey is secreted and lodged in the hollow sepals, and
is accessible to insects with short proboscides. The sepals and
petals are overtopped by the stamens, which are numerous and
curved outwards; and insects can only alight on the anthers, or
on the stigmas, or in the space between them. The possibility
of self-fertilisation is almost excluded by the stamens remaining
bent outwards to the last, while the pistil occupies the axis of
the flower; only rarely is a flower met with in which an anther
has become curved inwards to touch the stigma. The lime, which
rarely produces seed in England, attracts great numbers of insects

RT 11. | THE MECHANISMS OF FLOWERS. 147

f various orders, by the number and strong scent of its flowers

and the accessible position of their honey,
y

_ A. Hymenoptera—(a) Apidae: (1) Apis mellifica, L. $,s. (limes when in
ower are the resort of thousands of bees in fine weather,—I found none with
allen in their baskets, but all seemed to come for honey); (2) Bombus
srorum, I, 2, ab., s.; (3) Prosopis, ab. ; (b) Sphegidw: (4) Oxybelus
niglumis, L., ab., licking honey. B. Diptera—(a) Syrphide: (5) Eristalis
smorum, L.; (6) E. arbustorum, L.; (7) E. sepulcralis, L.; (8) E. tenax,
.; (9) Helophilus floreus, L., all very ab., now s. now f.p.; (10) Volucella
ellucens, L. ; (b) Muscidw: (11) Sareophaga carnaria, L., s.; (12) Lucilia
icina, F,; (13) Musca domestica, L., s.; (¢) Zalanide: (14) Tabanus
ovinus, L., s.

Orv. LINE.

_ 74. Linum catruarticum, L.—The five filaments are adherent
yy their expanded bases to a fleshy ring in the base of the flower,
rhich secretes five honey-drops from as many flat inconspicuous
glands on its outer side, opposite to the stamens: these honey-
drops enlarge till they reach the underlying sepals. To this fleshy
ring the petals are attached, a little above the honey-glands, and
a ternating with the stamens. The lower halves of the petals
ire in contact with one another, but narrowing suddenly at the
se they leave a round opening between each pair, immediately
bove the honey-gland.
The five anthers become mature at the same time as the
‘stigmas, and stand on a level with them. They cover themselves
all round with pollen, but for a short time after the opening
of the flower they stand at some distance from the stigmas, so
hat self-fertilisation cannot take place. An insect coming from
nother flower and plunging its proboscis into the middle between
ae and anthers wiil effect cross-fertilisation, but if it inserts
8 proboscis into the flower outside the anthers these will be
ressed against the stigmas and self-fertilisation will result.
If insect-visits do not occur, self-fertilisation takes place by
he bending inwards of the stamens. It seems to be efficient ;
or every one of the small, white, solitary flowers, which close
in the evening and receive very few insect-visits, produces a
capsule full of good seeds.
In spite of the great abundance of the plant, I have only

' Once seen two insects at work upon its flowers; viz. :—

- (1) Systeechus sulphureus, Mik. eee) (2) Hepes livida, L., s.
# Thur.).

Ea

148 THE FERTILISATION OF FLOWERS. [PART In.

75. Linum vsrratissiuuM, L.—This flower resembles the —
preceding one in regard-to its honey, and to. the simultaneous —
ripening and relative positions of anthers and stigmas ; hence also 4
in the likelihood of cross-fertilisation in case of insect-visits, and —
in the constancy of self-fertilisation if they fail. were

Hildebrand has shown by direct experiment that self-fertilisation
is efficient. ek

The flowers are more conspicuous and therefore more, visited —
by insects than those of L. cathartvcwm. Sprengel observed a
humble-bee on them; I have noted :— ; a. |

A. Hymenoptera—Apide : (1) Apis mellifica, L. 9, ab., s.; (2) Halictus
cylindricus, F. 2, cp. B. Lepidoptera—Noctue : (3) Plusia gamma, L., s.
See also No. 590, II. .

Fic. 45.—Linum catharticum, L.

1.—Young flower, from above ; the anthers are not yet in contact with the stigmas. a

2.—Ditto, viewed obliquely from above.

8.—A slightly older flower, from above; the five anthers are covered with pollen, and are in
contact: with the stigmas.

ne after removal of the calyx, to show the insertion of the petals and the position of the
nectaries.

5,—Essential organs removed from the flower, in the position of self-fertilisation.

6.—Sepal from the inside, with a drop of honey.

a, anther ; sf, stigma; n, nectary; a’, coherent filaments.

The dimorphic species of Linum have been the subject of
several important researches.

Darwin, as early as 1863, recorded dimorphism in L. grandi-
Joorum, Desf, L. perenne, L., and L. flavum, L., and made
experiments on the two first. In Linum grandiflorum the short-
styled flowers gave, on self-fertilisation, more seed than the long-
styled, which remained almost barren. Both proved to be far

- PART III, | THE MECHANISMS OF FLOWERS. 149

more fertile when legitimately fertilised. As a rule the pollen-
- grain failed to develop its pollen-tube when on the stigma of a
flower of its own kind (157).
| In Linum perenne illegitimate pollination of the ine Styled
form was quite unproductive, and in the short-styled form very
nearly so; in both forms, legitimate pollination led to full fertility
in three cases out of four. Hildebrand found that in this species
short-styled flowers were quite infertile with their own pollen,
with that from another flower on the same plant, or from any other
short-styled flower; but invariably fertile to pollen from a long-
styled flower (339, 340).
[In Linum Lewisti, Pursh. (L. Sibiricum, D.C.), according to
_ Planchon, each plant bears flowers of three kinds, one long-styled,
_ one short-styled, and one with styles and stamens of equal length ;
- that is to say, it is trimorphic, though not in the same sense that
_ Lythrum Salicaria is so. Dr. Friedrich Alefeld enumerates twenty-
nine dimorpbic species of Linum, all natives of Europe, Asia, or
- North Africa; while all the species from North and South America
and from the Cape are monomorphic (1). (Cf. Darwin, 167.)
Radiola linoides, D.C. (R. miliegrana, 8m.), is visited by minute
_ Diptera (590, IL).
_Erythroxylon is dimorphic.

a
i

Ord. MALPIGHIACEZ.

Camarea, St. Hil., and Janusia, A. Juss., according to Adr. de
Jussieu, have cleistogamic as well as normal flowers; Aspicarpa
ureus, Rich., occurs with only cleistogamic flowers (531); Gaudi-
chaudia, H. B. and K., also is placed among cleistogamic forms by
Kihn (399).

In Bunchosia gaudichaudiana the glands on the exterior of the
valyx seem not to be protective in function. They are visited by
4 various bees (Tetrapcedia and Epicharis), which in feeding on them

dust the under surface of their bodies with pollen, with which they
_ cross-fertilise other flowers (360).

Lie he Teg RR IRE ah 5 eh ty i a mr
_ t a5 - .

Orp. GERANIACEZ.
Tribe Geraniee.

a 76. GERANIUM PALUSTRE, L.—The structure of this flower was
thoroughly described and figured by Sprengel, who, however,
] observ ed no insect-visitors. In sunshine the flowers expand their

150 THE FERTILISATION OF FLOWERS. [PART IT.

purple petals to a diameter of 30 to 40 mm., and turn towards the ~
sun, so that, being brightly illuminated, they are visible at a great —
distance. )
The darker lines which converge to the centre, and the pale-
coloured claws of the petals, serve to direct insects towards the
honey, which is secreted by five glands at the bases of the outer
stamens, and protected from rain by hairs at the bases of the —
petals; it is accessible to very short-lipped insects. Insect-visits —
are so frequent that the power of self-fertilisation has become
completely lost. Each flower passes through three well-marked ~
stages, in which first the five outer stamens, next the five inner
stamens, and thirdly, when these have withered, the five stigmas,
become in turn ripe and stand up prominently in the middle of
the flower. Each whorl of stamens bends outwards as its anthers —
wither. hehe
Near Lippstadt this plant is confined to a single locality,
and I have only once watched it, for about half an hour, in a light
east wind and changeable sky (August 21, 1871). I was convinced —
in this short time of the great number of insects which frequent —
the plant. Whenever the sun shone out, I found the flowers visited —
by numerous flies and bees, especially species of LHalictus.

A. Hymenoptera-—A pide; (1) Halictus cylindricus, F. ¢; (2) H. albipes,
F.¢; (3) H. flavipes, F. ¢; (4) H. longulus, Sm. 9; (5) H. nitidiusculus, —
K.? ¢; (6) H. zonulus, Sm. ¢; (7) Andrena dorsata, K.¢; (8) A. fulvicrus, —
K. ¢; (9) Prosopis communis, Nyl. 9. B. Diptera—(a) Syrphide: (10) —
Rhingia rostrata, L. ; (11) Melithreptus scriptus, L. ; (12) Eristalis tenax, L. ; ‘
(13) Helophilus pendulus, L. ; (14) Platycheirus peltatus, Mgn. ; (b) Muscidae :
(15) small species of Anthomyia. C. Lepidoptera—(16) Pieris rape, L.,
—all sucking. _@

77. GERANIUM PRATENSE, L.—This is generally the most conspi- —
cuous and most abundantly visited plant in the meadows where it —
grows, just as G. palustre is in the marshes. It agrees in structure —
for the most part with the former species, and like it has lost
the power of self-fertilisation. Hildebrand gives (351, p. 19) —
a drawing and short description of its markedly proterandrous
flowers. He has shown that, at the time when the anthers dehisce ©
and are bent over the stigmas, these latter as a rule are incapable —
of fertilisation; they become capable ‘of fertilisation when the
anthers have diverged away from them, and finally lose this
capability on the falling off of the petals (342.)

Visitors: A. Hymenoptera—Apide: (1) Apis mellifica, L. §, very ab., s. ;
(2) Osmia rufa, L. 9,8. (May 27, 1868) ; (3) Chelostoma nigricorne, L. 9, s.

rarvun}| ‘HE MECHANISMS OF FLOWERS. 151

(Thur.) ; (4) Stelis aterrima, Pz. 2? ¢ (Thur.), s. ; (5) Andrena Coitana, K. ¢
_ (Sid.), 9 (Thur.), s.; (6) Halictus cylindricus, F. ¢; (7) H. albipes, F. ¢;
(8) H. leucozonius, K. ? ; (9) H. longulus, Sm. ¢; (10) H. maculatus, Sm. ¢
_ (Thur.),—all sucking ; (11) H. lucidulus, Schenck, ?, c.p.; (12) Prosopis

hyalinata, Sm. ¢,s. B, Diptera—Syrphidq: (13) Melithreptus pictus, Mgn., f.p.
_ See also No. 590, It.

78, GERANIUM PYRENAICUM, L.—The flowers are _proter-
androus, and regulariy fertilise themselves in default of insect-
visits. Before the bud expands, all the filaments have their thin
ends bent slightly outwards.

As soon as the flower opens, the five outer stamens, which
alternate with the petals and which bear at their base the honey-
glands, rise up so that their anthers overtop the divisions of:

em an arms

A\ UM) iY) y
ia
"4

; Fic. 46.—Geranium pyrenaicum, L.
F 1-4.—Positions of the reproductive organs at successive stages.

the stigma, which are still closely united, and each anther turns
that side where dehiscence is about to take place outwards and
upwards: this whole surface becomes covered with pollen. At the
_ same time the thin ends of the five inner stamens curve down-
_ wards, so that their anthers which are still closed are out of the
' way of insects, and do not hinder them from dusting themselves
with pollen. A day later these five inner stamens rise up and
] dehisce, so that now the stigmas are surrounded by a circle of ten
_ anthers, all dusted on their outer sides with pollen.

H ' After a day or two more, the stigmas at last begin to separate
} i from one another, and when they do so, they lie on a level with
| the anthers. If the pollen has not in the meanwhile been removed,
| an insect-visitor may now accomplish self-fertilisation as easily as

i

152 THE FERTILISATION OF FLOWERS. [parr ut.

cross-fertilisation, but if insect-visits have taken place to a sufficient
extent, the pollen is wholly removed before the stigmas separate,
and cross-fertilisation is the inevitable result of further insect-
visits. If insects do not visit the flower at all, self-fertilisation
always takes place, as the edges, at least, of the recurving stigmas
come in contact with the pollen, as I have repeatedly seen in the
case of specimens flowering in my room.

The fertilisation of the plant is therefore provided for under all ©

possible conditions.

I have not had a direct opportunity of observing this plant
fertilised by insects; but in sunny weather its insect-visitors must
be fairly numerous, for Herr Borgstette, to whom I am indebted
also for living examples of the plant, sent me the following insects
caught by him on its flowers at Teklenburg :—

A. Hymenoptera—(a) Apidw : (1) Andrena fulvago, Christ. 2, with pollen
of Geranium on its collecting-hairs ; (2) A. Gwynana, K.? ¢; (8) A. parvula,
K.9; (4) A. dorsata, K.?; (5) Halictus cylindricus, F.? ; (6) H. maculatus,
Sm. ?; (7) H. Smeathmanellus, K. 2 ; (8) Sphecodes gibbus, L. 9 ; (9) Osmia
fusea, Christ. (bicolor, Schrank), 2; (10) Chelostoma nigricorne, L. 9? ; (0)
Sphegide: (11) Ammophila sabulosa, L. ; (c) Vespide: (12) Odynerus
(Hoplopus) quinquefasciatus, F. B. Diptera—(a) Syrphide: (13) Helo-
philus floreus, L.} (14) Chrysotoxum bicinctum, L.; (15) Melithreptus
teeniatus, Mgn. ; (16) M. pictus, Mgn. ; (17) Syrphus balteatus, Deg. ; (18)
S. ribesii, L.; (19) 8. pyrastri, L.; (20) Ascia podagrica, F.; (21) Rhingia
rostrata, L. ; (22) Pelecotoma tricincta, Men. ; (b) Muscide: (23) Echinomyia
fera, L.; (24) Scatophaga stercoraria, L. C. Coleoptera—(a) Dermestide :
(25) Byturus fumatus, L. ; (6) Cistelide: (26) Cistela murina, L.; (e)
Malacodermata : (27) Malachius eneus, L.

On the Alps I found G. pyrenaicum abundantly visited by
insects, and incapable of spontaneous self-fertilisation (609). The
stamens bent far outwards before their anthers withered, and the

stigmas did not expand until all the anthers or at least the outer
five had fallen off.

79, GERANIUM SANGUINEUM, L., in spite of its flowers being
much more conspicuous, agrees fully i in the manner of its fortilieat
tion with G. pyrenaicum ; its conspicuousness seems therefore not
to insure cross-fertilisation in any greater degree but only to
compensate for its more shady habitat.

Visitors: A. Hymenoptera—(a) Apidae: (1) Halictus maculatus, Sm. 9 ;
(2) H. sexnotatus, K, ? (both usually alight on a petal, and go round
the flower, licking one nectary after another—their sides rub against. the
anthers in young flowers and the stigmas in old ones,—sometimes they alight

bt

ae pe ee, Smo CO TS me Pi we

PART III. | THE MECHANISMS OF FLOWERS. 153

- in the middle of the flower) ; (b) .Sphegide : (3) Oxybelus sp.,s. B. Diptera
_ —Syrphide : (4) Rhingia rostrata, L., settles sometimes in the meddle of the
flower, sometimes on a petal, and sacks all the five drops of honey in
succession, See also No. 590, m1, and No. 609.

80. GERANIUM MOLLE, L.—When the flower opens, the
divisions of the stigma lie close together so that their papillar
‘sides are hidden. The anthers are all closed and distant from the
“middle of the flower; the thin ends of their filaments are bent
outwards, the inner row of stamens which stand opposite to the
petals being bent farther outwards than the others which alternate
with the petals.

_ Now the outer stamens begin, one after the other, to bend
inwards, so as to lie over the apex of the stigma, and to dehisce
there; the flower is thus for a time male only. But even before
the first five stamens have all dehisced, the divisions of the stigma
begin to separate; so that the five anthers which lay over their

Fic. 47.—Geranium molle, L.

1—5. —Reproductive organs in successive stages. In 2, the inner whorl of stamens has been
removed. a’, outer stamens, alternating with the petals, and provided at the base with nectaries ; a’,

st whorl, opposite the petals, bent further out than the outer whorl when the flower opens ;
@ s gma,

_ apices come to lie in the angles between them, and let some part
of their pollen fall upon the stigmatic papilla.
| While the divisions of the stigma are expanding still more
widely, the inner anthers, which hitherto were closed, begin to
_ curve inwards and to dehisce. When all the anthers have shed
their pollen, they lie partly in the angles, partly over the ends
of the outspread stigmas, and only a little above them; so that
insects which alight in the middle of the flower touch saithiers and
_ stigmas at the same time, and can accomplish self-fertilisation as
\4 swell as cross-fertilisation.
The likelihood of self-fertilisation is thus - greater in these
less conspicuous and therefore less visited flowers than in either
| of the two preceding species, since anthers and stigmas come into
immediate contact with one another early in the flowering period.
The probability of cross-fertilisation is in consequence so much the

154 THE FERTILISATION OF FLOWERS. [PART IIT,

less, since even with abundant insect-visits the possibility of self-
fertilisation remains throughout.

Visitors : A. Diptera—(a) Syrphide: (1) Ascia podagrica, F., s., very ab. ;
(2) Rhingia rostrata, L., s. ; (3) Helophilus pendulus, L. Bee ; (4) Syritéa
pipiens, bi s.; (bd) Mastiches (5) Scatophaga “ierdaniie F., 88: Hymen-
optera—A pide : (6) Halictus sp., s. ; (7) Andrena Gwynana, K. 2, s.; (8)
Apis mellifica, L. § (I saw the hive-bee once (June 10, 1871), in a spot
where G. molle and G. pusillum were growing together, dip its tongue into
some flowers of G. molle, but abandon it immediately for Gleehates Pee
mention this’ apparently trivial circumstance because it shows (1) that
G. molle with its larger and darker flowers is preferred by an insect which has
to choose between it and G. pusillum, and (2) that even G. molle has not
sufficient attractions to win the services of the hive-bees, See also No, 590, 11.

81. GERANIUM PUSILLUM, L.—Although on superficial exa-
mination very easily confused with G. molle, G. pusillum differs
considerably from that species in the structure of its flower. _

Only the five stamens which alternate with the petals bear
anthers, and these stamens are provided at their base with honey

Fic. 48,—Geranium pusillum, L.
Essential organs of a flower whichis just opening, seen from above. st, stigma; a, anther.

glands, When the flower opens, the stamens are all erect and
closely applied to the pistil. The five divisions of the stigma are
spread out for half their length, their papillar surfaces are turned

upwards, and the anthers, which are still closed, lie a little below —
the stigmas in the angles between them. The flower therefore is —

as yet female only, and can only be fertilised through insect-ageney
by pollen from older flowers.

Soon after this, the anthers dehisce, covering themselves on
both sides with viscid pollen-grains, and the stigmas spread still
further apart, so that the anthers come to lie in the angles between
them and dust the papille on their edges with pollen. The flower
is now as much male as female. It can be fertilised more easily
with other pollen than with its own in case of insect-visits, but it
has already begun to fertilise itself.

At length the divisions of the stigma are fully outspread ;
while the ends of the filaments bend towards the middle of the

aor

—

ae Ae | ie

PART 111. | THE MECHANISMS OF FLOWERS. 155

flower, so that the anthers, still dusted with pollen, are closely
pressed together, and lie over the stigmas; they must therefore be
touched before the stigmas by an insect alighting in the middle of
the flower. In this stage the flowers are adapted for dusting the
bellies of insect-visitors with pollen for the fertilisation of other
flowers ; but their own stigmas are more easily reached by their own
than by other pollen.

: The anthers now easily fall off, and one often finds the older
flowers without anthers, but with five fully outspread stigmas.
These flowers are therefore again female only, but their stigmas
have already come in contact with their own pollen, though they
may still be fruitful with that from younger flowers.

If we compare the flowers of G. pusillum with those of its
near ally G. molle, with which it grows in company, and blooms at
_ the same time, we see that the former are smaller and paler, and
are accordingly more rarely visited by insects. In each case,
_ however, the regular occurrence of self-fertilisation compensates
for the great uncertainty of cross-fertilisation; and further, the
very early development of the stigmas enables the rare insect-visits
to be made full use of when they do occur. Finally, the more
rapid development of the flower permits the number of anthers to
_ be reduced to one-half.

In spite of frequent watching, I have only noticed the flowers
| of G. pusillum to be visited by one insect, a small gnat, Ascia
| podagrica, F., but by that on several occasions. It settled in the
_ middle of the flower and sucked honey from it. See also No.

590, II.

rr ——

REVIEW OF THE PRECEDING SPECIES OF GERANIUM.

If we exclude G. sanguinewm, which grows in more shady
_ spots, and arrange the other species according to the size and
conspicuousness of their flowers, we get a series as follows:
(1) G. palustre and G. pratense ; (2) G. pyrenaicum ; (3) G. molle ;
(4) G. pusillum. We get practically the same series if we arrange
| these species according to the decreasing chance of cross-ferti-
_lisation in case of insect-visits; and so also if we take them
according to the increasing likelihood of self-fertilisation in
_ default of insect-visits. For (1) in G@. pratense and G. palustre,
_ self-fertilisation never takes place in the ordinary flowers,’ while

_ _ 1 I say “in the ordinary flowers,” because it is possible, and even probable, that
| homogamic flowers oceur, as Axell has shown in the case of @. silvaticwm,

156 THE FERTILISATION OF FLOWERS. | PART II.

cross-fertilisation is thoroughly insured through the separation of
the sexual products both in time and space; (2) in G. pyrenaicum,
self-fertilisation never takes place in the earlier period, but it takes
place regularly though not abundantly tow ards the end of the
flowering period if insect-visits do not occur,—cross-fertilisation is
insured, as in the two preceding species, if insect-visits occur early,
but if they are delayed till the second stage they result more easily
than in the other two species in self-fertilisation also; (3) in
G. molle, even if insect-visits occur early and abundantly, self-
fertilisation is not excluded; and it takes place to a greater extent
than in the former species long before the flowering period ends, if
insect-visits do not occur,—though self-fertilisation is at no time
excluded, cross-fertilisation is favoured in case of insect-visits, by
the position of the reproductive organs in both stages of the
flower; (4) in @. pusillwm, self-fertilisation takes place abundantly
in every case before the end of flowering, but if insect-visits
take place in time, the stigma, which is developed before the
anthers, receives pollen from outside before self-fertilisation can
take place, and when pollen of the same flower is afterwards
applied to the stigma it is probably rendered useless by the
“prepotency ” of the other: if insect-visits are delayed till a later

period, so that pollen from outside is brought only to a stigma:

already laden with pollen of its own flower, we may still suppose
that the former outstrips the latter.

Thus in these Geraniums we see clearly how, as the number of
insect-visits diminishes with the censpicuousness of the flower, the
plant makes amends by an increasing likelihood of self-fertilisation
for the diminished chance of cross-fertilisation.

Geranium dissectum, L.—The manner of fertilisation is similar
to that of G. pusillum, but the flower has ten anthers. When
it opens, the stigmas already stand widely outspread, and
the anthers which stand close around them are still closed and
dehisce gradually one after another, dusting the stigmas with
pollen. I have seen it visited by flies and by Andrena (vide
No. 590, II. p. 217).

82. GERANIUM ROBERTIANUM, L.—When the flower opens,
the five stigmas are folded close together; the five outer stamens
stand close round them, in the middle of the flower, and their
anthers, which project a little above the stigmas, dehisce, covering

oT

ee ee ee ee ee eee ee ee

PART 111. | THE MECHANISMS OF FLOWERS. 157

their upper surfaces with pollen. The five inner stamens are still
bent outwards as far as possible, so as to lie upon the petals and
be out of the way of insects which alight on the flower. Before
the period of the outer stamens is over, the stigmas separate and
expand, so that their papillar surfaces which were hidden before
are now fully exposed in the middle of the flower.

As the outer stamens wither, the five imner ones rise up to
surround the style, which lengthens meanwhile, so that its five
stigmas stand a little way above the circle of pollen-covered
anthers.

Honey is secreted, as. in all our Geraniums, by the outer side of
the base of each outer stamen, and is collected in a slight hollow at
_ the base of each sepal: it may be reached by means of a proboscis
at least 7 mm. long, without which the insect must thrust its head
into the narrow part of the flower. I have seen Rhingia rostrata
- in great abundance, sucking up the five honey-drops one after
_ another with its proboscis, which is 11 to 12 mm. long ; it stood
first on one petal, then on another, and in older flowers its proboscis
touched first the stigmas and then the ripe anthers, in younger ones
the ripe anthers only. It effected cross-fertilisation regularly, but
at times, in drawing out its proboscis, it must also have effected
self-fertilisation. I have quite as often found this fly busy eating
| pollen. I have noted, in all, the following visitors :—

A. Diptera—Syrphide : (1) Rhingia rostrata, L., s. and f.p., ab. B. Cole-

| optera—(2) Dasytes flavipes, F., sucking and biting the petals. C. Lepid-
| optera—(3) Pieris napi, L., very ab., s. (Stromberg, May 15, 1868). See also

No. 590, II.

Cross-fertilisation is here insured, at first by the early develop-
ment of the outer stamens, and afterwards by the position of the
_ mature stigmas above the level of the anthers ; but sclf-fertilisation
is not absolutely excluded. I have not included this species in
_ the foregoing series, because I have not yet made sure whether
self-fertilisation does result in default of insect-visits.
Geranium silvaticum, L., is not only widely distributed in
Low Germany and in Britain, but occurs also in the Alps, where it
_ extends to far above the limit of trees and is one of the most

- abundantly visited plants. I have found upon its flowers :—

| Coleoptera, 8 ; Diptera, 21; Hymenoptera, 24 (Apide, 17) ; Lepid-
) optera, 21: in all, 74 species. |

fe This plant is historically interesting, since it suggested to
_ Sprengel the first idea of his theory. It is also remarkable for
} being gynodiecious, and for exhibiting transitions both towards

158 THE FERTILISATION OF FLOWERS. [PART III.

homogamy and towards dicecism (609). (List of visitors in Low
Germany, 590 Il. p. 218.

Geranium phoeum, L., is proterandrous. The two whorls of
stamens develop in succession, and the stigmas do not expand
until the stamens have again bent outwards. The flowers are
visited for their honey by humble-bees and by the hive-bee
(229, 665).

Geranium macrorhizon, I., is proterandrous, and the earlier
flowers are female only. The same is true of several species
of Pelargonium (356, p. 479).

83. Eropium cicutarium, L’Hérit—The honey is secreted
and stored as in all our other Geraniums; the five outer anthers

Fic. 49.—Erodium cicutarium, L’ Heérit.

1.—Flower, seen from above and in front.

2.—One of the two superior petals, magnified half as much again, showing the hairs at its base
which protect the nectar. The three dark lines converging towards the base form a ‘‘ path-finder "’
common to all the petals ; the elliptic spot is a ‘‘ path-finder’’ peculiar to the two upper petals.

8.—The reproductive organs. a, anthers; st, stigma; n, nectary; hk, drop of honey; ji, the five
filaments of the inner whorl of stamens, whose anthers are aborted.

4.—Centre of the flower, after removal of the pistil. A, point of attachment of the pistil; n,
nectaries. with their honey-drops protected by the two rows of hairs,

5.—Coccinella septempunctata, an awkward visitor of this flower.

only are fertile, as in G. pusillum. As in other Geraniums the
flowers turn towards the sun, rendering themselves conspicuous, in
spite of their short stalks, among all the other flowers of the bare,
sunny slopes where they chiefly grow.

While in the species of Geranium, the flowers though set
obliquely are quite regular, here there is a distinct difference

PART IL. | THE MECHANISMS OF FLOWERS. 159

between the upper and lower petals, the (two, rarely three) upper
ones bearing “ path-finders” in the form of fine black lines, the
_ (three, rarely two) lower ones being elongated to form convenient
_ alighting-places.

The flowers are distinctly proterandrous, so that cross-fertilisa-
tion never fails if insect-visits take place in time: if they do not
take place, then the flower is regularly self-fertilised.

I have only noted the following visitors :—

A. Hymenoptera—Apide: (1) Apis mellifica, L. §, s. and cp., ab.
(Sprengel found hive-bees and humble-bees collecting pollen). 3B. Cole-
optera—(2) Coccinella septempunctata, L., licking honey.

The awkward way in which this beetle, which is not fitted to
feed on flowers, obtained the honey, was too amusing to pass by
without notice. While seated on a petal, it applied its mouth to
one of the nectaries at the base thereof; while so doing, the petal
_ usually broke off, and the beetle was left olinging to the next petal,
or fell with its own to the ground. In the former case it kept on
_ its way round the flower, and frequently pulled off: all five petals,
one after another ; but when it fell it was always at once on its
legs again, running to another stalk of the same plant to climb up
anew. I saw one beetle fall four times to the ground without
growing wiser by experience.

_ __ Ludwig has published more comprehensive researches on the
mechanism of fertilisation in Hrodium (433, 434, 438).

Tribe Pelargonie,

Some general remarks on the structure of the flower in
| Tropewolum are given by Delpino (172); the structure in 7’
_ majus, L., was thoroughly described by Sprengel, who noted its
_ proterandrous condition

Tribe Oxalidee.

_ Hildebrand has investigated all the species of Ozalis in the
Botanic Gardens of Berlin and Bonn, in the Royal Herbarium of
_ Berlin, the Munich Herbarium, and the collections of Treviranus,
| A. Braun, and Selmeyer. He distinguishes twenty trimorphic
) species, whose different forms were in many cases looked upon as
distinct species previously; fifty-one species possess two forms,
and thirty have one only. Our three native species, O. acetosella, ie
0. stricta, L., and 0. corniculata, L, are shown to be mono-

- morphic (348).

a

160 THE FERTILISATION OF FLOWERS. [PART II.

Experiments on artificial pollination and the growth of the
resulting seeds, which Hildebrand afterwards instituted with two
trimorphic species, O. Valdiviana and O. Regnelli, Miquel, led to
results similar to those of Darwin in the case of Lythrum Salicaria.
They showed (1) that productiveness is greatest, or exists only,
after legitimate fertilisation ; (2) that both parent-plants influence
the fora of the offspring; (3) that pollen-grains from stamens of
equal length are of the same size, and diminish from the tallest to
the shortest anthers.

Hildebrand gives a figure of the trimophic flowers of Oxalis
gracilis, Jacq. (348). H. v. Mohl has described the cleistogamic
flowers of O. acetosella (531).

Tribe Balsaminee.

:

Impatiens Balsamina, Tilo.—In younger flowers the anthers lie —

upon the still closed stigmas, and dust their pollen upon the backs
of insects (bees) which dip their proboscides into the spur; in older
flowers, when the crown of anthers has withered, the outspread
stigmas come in contact with the same parts of the bee.

H. v. Mohl has described cleistogamic flowers in Jmpatiens
Noli-me-tangere, L., and in North American species (531).

On cleistogamy in Impatiens fulva, Nutt, see M. A. Loche

(417); on cleistogamy in both species, see Bennett (72, 79).
Impatiens parviflora, D.C., according to Bennett, never produces
cleistogamic flowers, but according to Henslow it is liable to
spontaneous self-fertilisation.
North American species of Jipatiens are visited by humming-
birds (164).
Orv. RUTACE A,

84. RUTA GRAVEOLENS, L.—The most prominent features of

the flower have been described by Sprengel.

A fleshy disc situated beneath the ovary secretes ines in
eight to ten glands upon the bases of the stamens, sometimes in
larger glands between these, besides producing small drops over its

whole surface: the honey lies quite exposed and freely accessible. _

The strong scent and the greenish-yellow colour of the flowers

seem able to attract only Hymenoptera and Diptera, the latter in —

very great numbers. The stamens, when the flower opens, lie
two in each of the petals, which are hood-shaped and spread out
horizontally. According to Sprengel, two stamens on opposite
sides of the flower rise up simultaneously, bending inwards so that

J PART III. | ‘THE MECHANISMS OF FLOWERS. 161

_ their anthers now covered with pollen come to lie above the ovary
in the middle of the flower; as they wither they bend back again,
_ and two others take their shins: The stigma only ripens after all
_ the stamens have withered, so that all possibility of self-fertilisation
is excluded.
___ My own observations, made upon plants flowering in my room,
differ from Sprengel’s in several points. In all the flowers which
I examined, the stamens rose up not in pairs but singly, and
each was joined by its successor a short time before it withered
and fell back ; so that when two were erect at the same time, one
of them was at the close the other at the commencement of its
_ period. After all the stamens have bent back the stigma ripens,
but before it withers the stamens rise up again; and if, through
lack of insect-visitors, they still retain a stock of pollen, they shed
“some of it upon the stigma. So Treviranus’ assertion that the
approach of the stamens to the stigma takes place for the purpose
(3 of self-fertilisation is not quite groundless; but such self-fertilisa-
tion takes place only when the flowering time is passing away
_ without insect-visits having taken place.
The whole arrangement of the flower greatly resembles that of
_ Parnassia. In both we have fully exposed honey and successive
_ development of the stamens and then of the stigma; in both the
_ conveyance of pollen is insured by the centre of the flower, where.
_ an insect is most likely to alight, being occupied successively by a
_ pollen-covered anther and a mature stigma; both are visited by
_ many Diptera and Hymenoptera. But while the white flowers of
_ Parnassia are visited by beetles, the yellowish flowers of Ruta are
_ altogether avoided by them.

_ Visitors: A. Diptera—(a) Stratiomyide: (1) Sargus cuprarius, L. ; (d)
_ Syrphide : (2) Syrphus ribesii, L., ab. ; (3) S. nitidicollis, Mgn. ; (4) Meli-
threptus pictus, Mgn. ; (5) Ascia podagrica, F. ; (6) Eristalis sepulcralis, L. ;
(7) Helophilus floreus, L. ; (8) Syritta pipiens, L., very ab.,—all mainly
sucking, but sometimes also eating pollen; similarly (¢c) Muscide: (9)
Lucilia silvarum, Mgn. ; (10) L. cornicina, F. ; (11) Sarcophaga carnaria, L. ;
| (12) S. hemarrhoa, Mgn. ; (13) S. albiceps, Mgn. ; (14) Calliphora erythro-
eephals, Mgn. ; (15) Pollenia rudis, Mgn. ; (16) Sepsis; (17) Anthomyia
| radicum, L. » very ab. ; (18) A. obelisca, Men. ; ; (19) A. pratensis, Mgn., (the
i last three species were determined for me by Herr ‘ecg B. Hymen-
. 0 ptera—(a) Evaniade : (20) Feenus affectator, F.; (21) F. jaculator, F. ;
(b) Ichneumonidae : (22) various species ; (c) Chryside: (23) Chrysis ignita,
_ L.; (d) Sphegide : (24) Crabro oo v. d.L. 9; (25) Oxybelus bellus,
Dib. ; (26) Trypoxylon figulus, L. ; (27) Rhopalum clavipes, L. ; (28) Agenia
a pret, F. $; (29) Tiphia minuta, v.d. L. ¢; (e) Vespide : (30) Odynerus
M

~

162 THE FERTILISATION OF FLOWERS. [PART III.

parietum, L. 9; (f) Apide: (31) Halictus sexnotatus, K. 9; (32) Prosopis
sinuata, Schenk, ?, freq. ; (33) Apis mellifica, L. § ,—all the Hymenoptera
only sucking. See also No. 590, 1. $).

Dictamnus, L., is visited by humble-bees, whose ventral surfaces
come in contact with the reproductive organs of the flower. In
the first stage the style lies hidden among the stamens, in the
second it is bent outwards with its mature stigma (178, 360,
p- 658).

Correa, Sm., is proterandrous, according to Delpino (178,
p. 170).

Orv. CELAST'RINEL.

85. EvonyMus EUROPA, L.—The honey is secreted by a
fleshy disc surrounding the style, and lies in so thin a layer that
it can only be attractive to short-lipped insects. The dull yellow
colour of the flowers moreover excludes those insects which are
enticed only by bright colours. Like other flowers of the same

a

colour, these are visited only by Diptera and Hymenoptera, and —

especially by the former ; the flies run irregularly over the flowers, —

attacking the honey-covered surface, now here now there, with their
outspread ‘ end-flaps’ (abelle), and in consequence touching anthers
and stigmas now with one part of their bodies, now with another.
In such circumstances the flowers could only attain regular cross-
fertilisation by separation of the sexual organs, either in time or

space. Both separations have in fact taken place, and self- —

fertilisation, which had become unnecessary owing to the abundant
insect-visits, has finally become impossible. .

The four anthers stand at a distance from the stigma upon
stiff filaments, and dehisce directly outwards, while the stigma is —
still immature and its lobes remain tightly closed. These only —
separate several days later, and again close up after fertilisation.

Thus self-fertilisation cannot take place without the aid of insects ;

and with their aid only if the earlier days of flowering have passed —

by without the flower being visited (cf. Delpino, 177).
Li. europea is polygamous according to Darwin (167).

Visitors: A. Diptera—(a) Syrphide: (1) Eristalis tenax, L. ; (2) Helo-
philus floreus, L. ; (3) Syrphus ribesii, L. ; (4) Syritta pipiens, L. ; (5) Xantho-
gramma citrofasciata, Deg. all sucking ; (b) Muscide: (6) Musca domestica,
L.; (7) Calliphora vomitoria, L.; (8) Sarcophaga carnaria, L., very ab. ;

>
(9) Seatophaga stercoraria, L. ; (10) Lucilia cornicina, F.; (c) Bibionide : (11)

PART III. | THE MECHANISMS OF FLOWERS. 163

Bibio hortulanus, L., all sucking ; (12) numerous small midges, B. Hymen-
optera—Formicide ; (13) Formica sp. Spiders weave their webs about these
_ flowers to catch the numerous flies. I saw a species of Vespa alight and
_ capture a Sarcophaga carnaria.

Orv. RHAMNEZ,

Paliurus aculeatus, Lam., is distinctly proterandrous, according
to Delpino. The stamens are at first erect or inclined slightly
inwards, but bend backwards when the stigmas develop. The
fertilisers are probably flies of moderate or large size (177).

Fic. 50.—Rhamnus Frangula, L.

1.—Young flower, from above.

; —Ditto, after removal of the anterior half of the calyx
3.—Older flower, from above.

8, sepal; p, petal ; a, anther; st, stigma; ov, ovary ; n, nectary.

_ 86. Ruamnus FrAnGcuLA, L.—The receptacle forms a hemi-
spherical, fleshy disc, which secretes and contains the honey.
_ It is produced at its margin into five triangular white calycine
| lobes, which are directed obliquely outwards in the flowering
_ period. Between these sepaline lobes, there occur on the margin
of the receptacle five small white bi-lobed petals; close below
them, and half surrounded by them are five stamens, which are
3 inclined inwards, and dehisce introrsely.
M 2

164 THE FERTILISATION OF FLOWERS. [PART III,

From the base of the flower rises the ovary ; whose short style
is terminated by a bi-lobed stigma below the level of the stamens.
When the anthers dehisce, the stigmatic lobes are still small, and
probably incapable of fertilisation, but when the stamens wither,
they are four times as large as at the commencement of flowering
(Fig. 50). The flowers are thus proterandrous. An insect sucking
the honey must touch the stamens with one side of its head or
proboscis, and the stigma with the other; in this case self-
fertilisation cannot occur, though the stigma and anthers ripen
at the same time, but cross-fertilisation proceeds regularly.
Pollen-collecting insects and sometimes even those sucking
honey, if they thrust their heads several times into the same
flower, effect self-fertilisation as well as cross-fertilisation.

The honey on account of its open situation is accessible to
very various insects, but the flowers are so inconspicuous that they
are very little visited. Self-fertilisation can take place if needed,
as the stamens on withering may shed their pollen on the now
mature stigmas. :

Visitors: A. Hymenoptera—(a) Apide: (1) Apis mellifica, L. $,s. and
c.p.; (2) Bombus agrorum, F. 9 §, 8. ; (3) Macropis labiata, Pz. ¢, s. ; (b)
Vespide: (4) Vespa silvestris, Scop. ab, s.; (5) Eumenes pomiformis, L., s.
B. Diptera—(6) Culex pipiens, L. ¢,s.

Lhamnus lanceolatus, Pursh., is dimorphic, according to Darwin,
but it is not heterostyled in the strict sense (Darwin, 167).

Rhamnus pumilus, L.—The size of the flower and the number —

of its parts is reduced in this species, but the plant is visited by

numerous insects. The flower is generally tetramerous, and the —

petals exhibit all stages of abortion to complete disappearance

(609).

Thamnus catharticus, L., is dina with two sub-forms of each |

sex (167).
Orv. SAPINDACEZ.

Serjania cuspidata, St. Hil—The flower resembles the labiate
type, and, lke Paullinia, L., and Cardiospermum, L., is
proterandrous.

Many species of Acer, according to Delpino, are proterandrous
and are fertilised by flies (178, 360).

87. AiscuLus Hippocastanum, L.—The arrangement of the
flower was thoroughly described by Sprengel. My own notes and

PART 111] THE MECHANISMS OF FLOWERS. 165

_ drawings of the horse-chestnut flower, made before I became
- acquainted with Sprengel’s work, differ in one point from his
- account, and agree with that of Hildebrand. While Sprengel
_ declares that in the younger flowers insect-visitors come in contact
only with the stamens because the style is as yet low down, I
found just the opposite condition, as the annexed figures show.
_ Although I neglected to compare microscopically stigmas of younger
_and older flowers, I can hardly doubt that Hildebrand is right
in stating the hermaphrodite flowers of the horse-chestnut to be
_ proterogynous. According to Dr. Ogle (632), there occur usually
_ in the lower part of each inflorescence flowers whose anthers fall
_ off without dehiscing although their loculi are full of pollen, and
_ which thus play the part of purely female flowers.

| The chief fertilisers are humble-bees ; therefore the dimensions
‘ of the flower are just such as to suit dine insects. The style

Fig. 51.—A4sculus Hippocastanum.

1.—Section of male flower.

2.—Hermaphrodite flower in first (female) stage, seen obliquely from the front.
3.—Section of ditto, in second (male) stage.

a, anther ; n, nectary ; ov, ovary ; ov’ rudimentary ovary ; 8, sepal; p, petal.

and stamens protrude so far from the flower (in a curve concave
superiorly), that a bee on alighting just touches stigma or anthers
_ with the hinder part of his body. The legs fit into the interspaces
__ between the petals, so that the insect finds itself at once in the
most convenient position for sucking, and immediately thrusts
its proboscis in the direction 2 (1, 3, Fig. 51) into the honey-
_ holding base of the flower. Such a position also permits the
insect to fly away very readily, and thus the whole time occupied
is reduced to a minimum: alighting, thrusting in the proboscis,
| and flying away again is the work of a few seconds.

_ Other bees, whose dimensions do not correspond so well to
those of the flowers, have to spend more time over the operation.
The humble-bee is also favourably placed for carrying off pollen
; on the tarsal brushes of the middle and hindlegs. The quick

Be

166 THE FERTILISATION OF FLOWERS. [PART III.

action of the insects is of as much importance to the plant as
to themselves: for the quicker they work, the more young
hermaphrodite flowers get fertilised in the same time, with pollen
from male flowers or older hermaphrodite flowers; and this in
changeable weather is an important consideration.

I have only seen the following humble-bees visiting the horse-chestnut :—
(1) Bombus terrestris, L.; (2) B. lapidarius, L., both species s. and ep.,
though I have heard bees humming all day long about the trees in flower in a
neighbouring garden. My notes for visitors to this plant refer only to a single
afternoon (May 14, 1867). The other visitors noticed were :—(3) Apis mellifica,
L. §, s. and c.p., very ab. ; (4) Eucera longicornis, L. ¢, s.; (5) Osmia rufa,
L. g,s.; (6) Halictus rubicundus, Christ., 2, cp. ; (7) Andrena sp.

In &sculus Pavia (rubicunda), D.C., according to Hildebrand,
all the hermaphrodite flowers are proterogynous, as in Aseulus
Hippocastanum ; but the first flowers of each inflorescence are male
only, to supply pollen for the opening proterogynous flowers (351).

Orv. AVNACARDIACE ZL.

Fie. 52.—Rhus Cotinus, L.
1,—Male flower, 2.—Hermaphrodite ditto. 3.—Female ditto, n, nectary.

88. Ruus Corinus, L. (the Wig-tree).— Rhus Cotinus shows all
possible transitional stages between staminate, hermaphrodite, and
pistillate flowers: the first of these are largest, most expanded, and
most conspicuous; the last are least so. Hence most insect-
visitors come to these flowers in the most advantageous order.
(Cf. Ribes alpinum, Salix, Bryonia, Asparagus.)

In both staminate and pistillate flowers of 2. Cotinus traces of
the aborted organs remain visible.

The flowers secrete abundant honey on the orange-red fleshy
dise surrounding the ovaries, and display it conspicuously.
They are visited by numerous insects, chiefly forms with short
proboscides. Cross-fertilisation is usually effected even in the

PART III. | THE MECHANISMS OF FLOWERS. 167

hermaphrodite flowers owing to the wide separation of the stamens
and pistil. Like all other flowers of a dull yellow colour they are
almost completely avoided by Coleoptera.

Visitors: A. Diptera—(a) Syrphide : (1) Helophilus floreus, L., very ab. ;

_ (2) H. pendulus, L. ; (3) Syritta pipiens, L., very ab., all three s. and f.p. ;

_ (6) Muscide : (4) Calliphora erythrocephala, Mgn. ; (5) Sarcophaga carnaria,
L. ; (6) Lucilia cornicina, F., s., also several undetermined flies and gnats.
B. Coleoptera—Dermestide : (7) Anthrenus pimpinelle, F., licking honey.
_C. Hymenoptera—(a) Tenthredinide: (8) Tenthredo marginella, Kl.; (0)
Sphegide: (9) Oxybelus uniglumis, L.; (10) Gorytes campestris, L. ; (c)
_ Vespide: (11) Eumenes pomiformis, Spin.; (12) Odynerus sinuatus, F. ;
_ (13) O. spinipes, H. Sch. (quinquefasciatus, F.), the last six all licking honey ;

iF (d) Apide: (14) Andrena albicans, K. 9, c.p.; (15) Halictus sexstrigatus,

Schenck, 2; (16) H. sexnotatus, K. 2; (17) Apis mellifica, L. %, the last

three sucking honey.

ee

‘ie 89. Ruus typHina, L.—I have had little opportunity of
watching the flowers of this plant at the proper season. They are
very conspicuous, and secrete abundant and easily accessible honey,
and the possibility of self-fertilisation is excluded by diccism, I
have as yet only observed the following visitors :—

| A. Hymenoptera—Apide : (1) Apis mellifica, L. $, very ab., s.; (2)
_ Prosopis communis, Nyl. 2 ¢,s. B. Neuroptera—(4) Panorpa communis, L.
licking honey.

According to Delpino, many species of Rhus are > proterandrous
and fertilised by flies (177).

Orv. CORTARIEZ.

17 Coriaria myrtifolia, L., is markedly proterandrous, according to
| _ Hildebrand, and the first flowers are male only (356).

Orv. LEGUMINOS.
Tribe Lotee.
90. Lorus cornicuLatus, L.—The structure of the flower of

__ Lotus corniculatus is described briefly by Delpino (172, p. 25). He

; - gives it as an example of a papilionaceous flower furnished with

{ a piston-apparatus, and he subsequently compared it fully with

i; Coronilla Emerus (178, pp. 39-44). I have devoted especial
te 1 attention to the fertilisation of these plants, and I shall discuss
_ their structure fully.

168 THE FERTILISATION OF FLOWERS. [PART IIT.

The anthers dehisce in the bud, whilst both carina and ale are
still covered by the vexillum, and before any of the petals have
nearly attained their full size. At an earlier period the five outer
stamens, which alternate with the petals, and the five inner
stamens are unequally developed, so that the anthers form two
whorls, one behind the other round the style; but when they are
ready to dehisce all ten stamens are of equal length, and their

Fic, 53.—Lotus corniculatus, L.

1.—Front view of flower.

2.—Oblique view.

8.—Side view, after removal of the vexillum.

4.—F lower, seen from above, after removal of the vexillum.

5.—Side view, after removal of the ala, more magnified.

6.—From the right side, after careful removal of the right half of the carina.

7.—F lower viewed from above, after removal of the vexillum and ale.

8.—The essential organs inclosed in the front half of the carina, as shown in 6, more magnified.

9.—Side view of the essential organs from a bud, immediately after the pollen has been shed.
A comparison of 8 and 9 shows how much longer and thicker the outer stamens become during the
interval between the shedding of the pollen and the opening of the flower.

10.—The same organs seen from above, to show how the outer, terminally-thickened stamens
spring apart when freed from the pressure of the carina.

11.—The nine synadelphous stamens of a fully developed flower spread out.

a, entrances to the honey ; b. the upward curvature of the free stamens; c, the carinal depres-
sions, into which fit the two depressions of the ale (c’): d, the tive inner stamens, which remain
short; ¢, the five outer, which grow long and club-shaped ; f, stigma; e-g, apex of carina, full of
pollen ; g, orifice through which the pollen is expelled.

anthers reach to the base of the conical apex of the carina, The
ends of the filaments are still very much alike, but the five outer

Mics

7
-

PR ee et eee, ee

a a
eh

a ae ee

PART III. | THE MECHANISMS OF FLOWERS. 169

_ show a slight, club-shaped thickening, which afterwards becomes
- much more apparent ; the five inner, including the superior solitary
_ stamen, remain unthickened throughout. The anthers, while yet

fully twice as broad as the ends of the filaments, dehisce in the base
_of the cone, completely filling it with pollen, and when they have
"discharged their contents they shrivel up to a fourth of their former
size. All the petals now grow to their full size, and the five
_ outer stamens elongate and the ends of their filaments thicken, so
: that, in spite of the continual growth of the carina, they still reach
_ to the hollow cone formed by its apex, and completely fill its lower
and wider portion notwithstanding that the five inner stamens
_ have remained behind. When the flower has reached maturity, the
essential organs occupy the relative positions shown in 8, Fig. 53.
_ The five inner stamens (d) are useless after shedding their pollen,
and, far outstripped in development by the other organs, they lie
_ shrivelled up in the lower and wider part of the carina. The five
| outer (e), which have still an important part to play, have continued
- to grow, and lie with their thickened ends tightly closing in the
_ base of the hollow cone now filled with pollen. Somewhat below
_ the apex of the carina lies the stigma (7), and at the apex (near g)
is a narrow opening; the entire space between the thickened
_ filaments and the orifice is filled with compressed pollen, and thus
} the piston-mechanism is complete. On the application of a slight
| downward pressure to the carina, the thickened filaments are
_ forced further into the apical cone of the carina, and squeeze a
_ certain amount of pollen through the orifice in a narrow ribbon.
_ When the pressure ceases, the thickened filaments, thus squeezed
_ together, tend to spring apart, and so raise up the apical cone and
_ restore the whole carina to its former position ; the elasticity of the
_ carina itself assists in this action. If the carina be drawn or
_ pressed still further down, the end of the style protrudes, covered
_ with pollen, from the orifice. When the pressure ceases it returns
again into the carina; but the edges of the orifice, which readily
yield to a pressure from within and allow the stigma and pollen to
pass out without hindrance, spring together and scrape off almost
the whole of the pollen from the stigma as it returns within
the carina.

As soon as the piston-mechanism has become so far complete, the
vexillum rises up perpendicularly so as to direct its broad, dark

- surface straight to the front, and both the alz arch their
_ surfaces into two hemispheres inclosing the carina, so as to strike
| the eye equally well from before, from behind, or from either side.

(

170 THE FERTILISATION OF FLOWERS. [PART III.

The fleshy thickened base of the coalesced stamens secretes honey
on the inner surface, which lies surrounding the base of the ovary
and is only to be reached through two small openings on either
side of the base of the superior stamen, and the flower is now
ready to receive insect-visitors (1, 2, Fig. 53). It only remains to
explain how the downward pressure of the carina is effected. This
important service is rendered by the ale. They form a platform
for the insects, and are so combined with the carina that it is bent
downwards along with them. Each ala has at the base of its limba
deep depression (3, ¢’), which fits into a corresponding hollow on the
upper surface of the base of the carina (5, ¢), and close behind this
spot the upper edges of the alee cohere together. If a bee comes,
and, whilst clasping the ale with its mid and hindlegs, thrusts its
head and forelegs under the vexillum to insert its proboscis into
either of the honey-passages, the ale and with them the carina
bend downwards, and a quantity of pollen oozes through the tip
of the carina and becomes attached to the hairy ventral surface of
the bee. If the bee forces its way further into the flower and thus
presses the alee and carina down still more, the stigma protrudes
from the apex of the carina and rubs against the ventral surface
of the insect.

The insect’s belly is covered with innumerable pollen-grains
from the same and from previously visited flowers, and cross-
fertilisation takes place without fail. And it is scarcely possible
to doubt, though it is hard to prove by direct observation,
that the pollen brought from other flowers is prepotent in
its action.

Delpino considers that the stigma does not become capable of
fertilisation until its papille have been slightly rubbed, by which
the stigmatic surface is made sticky. If this view is correct, cross-
fertilisation must take place regularly, in the course of repeated
visits, since the stigma must be cleared of its own pollen before its
papillze become exposed to friction. In either case it is very much
to be desired for the sake of a clear understanding of the mechanism
of this flower, that experiments should be instituted to show
whether Lotus does or does not produce seed when protected from
insects,

The process of squeezing out a little ribbon of pollen by de-
pressing the carina may be repeated eight to twelve times, if the
carina is pressed down only a little way each time. But bees when
collecting pollen press the ale and carina down as far as possible to
get all the pollen that they can, so that the supply is exhausted

partir] § THE MECHANISMS OF FLOWERS. 171

_ after a very few visits. Bees, and especially those with abdominal
collecting-brushes, are the chief fertilisers of the plant.
(i
ie Visitors: A. Hymenoptera—(a) Apide: Bees with abdominal collecting-
brushes: (1) Osmia interrupta, Schenck, 2 (L. Sld. Thur.) ; (2) O. aurulenta,
Pz. 2 (Sid., Thur.), very freq. ; (3) O. enea, L. 2 ¢@, (L.), freq.; (4) Diphysis
serratulee, Pz. 9 ¢ (L. Sld.), freq. ; (5) Megachile Willughbiella, K.? (L.Sld.) ;
(6) M. pyrina, Lep. 2‘¢, freq. ; (7) M. circumcincta, K. ? ¢ (L. Sld.), ab. ;
(8) Anthidium manicatum, L.? (L.); (9) A. punctatum, Latr. ? ¢ (Thur), ab. ;
(10) A. strigatum, Latr. ? ¢ (Thur.), freq. The females of all these species
collect pollen and suck honey at the same time ; (b) Bees with femoral and
tibial collecting-baskets ; (11) Bombus agrorum, F. ? %,s., more rarely c.p. ;
(12) B. terrestris, L. 2 do. ; (13) Apis mellifica, L. 9, very ab., do. ; (14)
_Eucera longicornis; L. 9 ¢, very ab., only s.; (15) Rhophites canus, Eversm.
¢ 6 (Thur.),s. ; (16) Andrena labialis, K.?, s.; (17) A. xanthura, K. 2, c.p. ;
(18) A. convexiuscula, K. 9, s. ande.p.; (19) Halictus rubicundus, Chr. 9, s.
_ and c.p. ; (20) H. flavipes, K.?,s.; (¢) Cuckoo-bees : (21) Nomada ruficornis,
L. 9,°s.; (22) Celioxys, sp. ¢, s. B. Diptera—(a) Conopide ; (23) Conops
flavipes, L. (4—5), s. only observed once,—thrusting its tongue beneath the
— vexillum ; (b) Syrphide : (24) Melanostoma mellina, L., b.p. C. Lepidoptera
_ —(a) Rhopalocera: (25) Lyczena Icarus, Rott., s. ; (26) Hesperia tages, L. s. ;
(27) H. alveolus, H. s. ; (6) Sphinges: (28) Sesia empiformis, E. (Thur.), s. ;
(29) Zygena lonicere, Esp. (Thur.), s.; (ce) Bombyces: (30) Porthesia
auriflua, S. V. (sucking vainly for honey); (@) Noctuw: (31) Euclidia
glyphica, L., s. Lepidoptera and Conops thrust their tongues beneath the
_ vexillum without perceptibly depressing the carina; they were therefore quite
useless for fertilisation.

Twenty-seven additional visitors (19 Apide, 5 Lepidoptera.
3 Diptera) are recorded in my Weitere Beobachtungen, I. p. 246.
Altogether, I have observed upon Lotus :—

Apide, Lepidoptera. | Diptera. Total.
In Low Germany... ae 17 25 1 43
On the Alps 41 12 3 56

.

That is to say, in each hundred species of visitors there are :

Apide, |Lepidoptera.| Diptera. Total.
In Low Germany... 39°5 581 2°3 99°9
On the Alps to'2 21°4 5°38 99°9

172 THE FERTILISATION OF FLOWERS. [PART IIT.

91. ANTHYLLIS VULNERARIA, L.—Anthyllis vulneraria belongs
to the group of papilionaceous flowers with piston-mechanism, but
it differs so strikingly from Lotus in many points that it deserves a —
special description. : |

The very long claws of the petals are surrounded by a calyx,
9 to 10 mm. long, somewhat swollen in the middle and covered
with soft hairs (1 a, Fig. 54). From this the vexillum projects to a
distance of 6 to 7 mm., inclined obliquely upwards ; a groove on the ~
lower part of its blade (7 0’) receives the alz, and two rounded lobes -
at its base (7d, d) clasp round them inferiorly, so that the als are
completely embraced by the vexillum.

Fic. 54.—Anthyllis vulneraria, L.

1.—Flower from below.

2.—WDitto, from the side, after removal of the calyx.

3.—Ditto, from above; the vexillum also has been removed.

4.—Anterior half of the carina seen obliquely from the left side and above,

5.—Anterior half of carina and the right ala.

6.—Lower side of left ala: the claw is cut short.

7.—Vexillum from below (1—7 x 34).

8.—Apex of carina, after removal of its left half (x 7).

a, calyx ; b, under side of vexillum ; b’, its groove ; ¢, upper (outer) surface of vexillum ; d, lobes
of vexillum which grasp the ale and carina; e, inner, f, outer, sides of ala; g, deep narrow groove
on the outside of the vexillum, visible inside as a sharp ridge, h; i, hollow in the 8 surface of
the carina (k), into which the ridge h fits ; 1, sharp process or tooth of the carina, which fits into a
hollow h’, behind the ridge h; m, carinal orifice, at which the pollen emerges ; m’, anterior infolding
of the upper border of the ala; n, column; o, entrance to the honey; p, thickened ends of the
filaments ; g, empty withered anthers; r, pollen; s, stigma; tt, claws of the ale.

An insect which tries to reach the honey at the base of the
flower must grasp the sides of the ale and thrust its proboscis (at
least 9 to 10 mm. long) under the vexillum.

The alw surround the carina, and are so connected with it that
when the alee are depressed the carina is forced down with them,
This connection is formed in three ways: (1), a deep narrow groove
(3, g) exists at the base of each ala, appearing on the inner side as

PART III. | THE MECHANISMS OF FLOWERS. 173

_asharp ridge (5, 6,2) which fits into a groove on the carina (4, 5, 2) ;
_ (2),a sharp triangular tooth (4, 5, /) is borne by the carina behind
\ this groove, and catches in the space (5, 6, h’) behind the ridge on
_ the inner surface of the ala; and (3), the upper borders of the ale
are folded inwards for a linet space (3, 5, 6, m’), and at this fold
_ they cohere together above the carina. Close in front of the spot
_ where the upper borders of the alse are thus firmly applied to each
' other, the apex of the carina emerges when the alz are pressed down.
| The upper margins of the carina are coherent except at the apex,
' where they leave a longitudinal slit, and when the carina (along
_ with the ale) is depressed, there emerges from this slit a ribbon-
_ shaped mass of pollen, pressed forwards by the thickened ends of
the ten stamens (8, 7).

When the pressure is removed the ale and carina return to their
i former position ; when they are again pressed down another portion
_ of pollen is pressed out. After the greater part of the pollen has
been squeezed out in this way, the stigma (8 s) emerges at the same
_ slit; it has lain imbedded in pollen in the carina but emerges free
= Ben it, for its papillze are not yet adhesive and the pollen-grains are
scraped off by the edges of the slit.

____ If the stigma is rubbed with slight pressure over a glass plate a
line of moisture marks its course; if it be now brought in contact
with pollen, the pollen adheres to it so firmly that it is not easily
_ removed. Doubtless the same effect is produced by insect-visits ;
1 he flower gives up pollen to the ventral hairs of its first visitors ;
and after its pollen is spent, the superficial cells of the stigma
coming in contact with the insect get ruptured and exude their
fluid contents; pollen from other flowers, with which the insect is
already dusted, now adheres to the stigma and the act of cross-
fertilisation is complete. Whether in absence of insects the flower
is fertilised by its own pollen has still to be decided by a simple ex-
periment. I observed the following bees fertilising this plant near

a (1) Bombus silvarum, L. § (10'), s.; (2) B. hortorum, L. 2 (21), s.; (3)
i B. muscorum, F. ? (13—14), s. ; (4) Osmia aurulenta, Pz. 9 (8—9), ep., (all
very frequent). I also saw Lycena alsus, W. V. 9, and a Capsus vainly
\ ~ attempting to suck the honey. I have seen it visited on the Alps by 12
| Bepecies of bees, and 10 of Lepidoptera (609).
—~Doryenium (Bonjeania) hirsutum, Ser—According to Delpino,
_ the flower has a piston-action, and the ends of the filaments are
: ‘ ickened (179, p. 45).

: ‘ 1 These numbers in brackets indicate the length of the insect’s proboscis,

174: THE FERTILISATION OF FLOWERS. [PART 111.

Tribe T7rifolie.

92. ONONIS sSPINOSA, L.—This plant also has flowers with a
piston-mechanism, which however differ materially both from Lotus
and Anthyllis. They are devoid of honey, and, like almost all the
honeyless Papilionacez, monadelphous, for the separation of the
superior stamen in other forms is only useful in giving access to the
honey. The ale, which serve as in most other Papilionaceze for
bees to alight on, and as levers to depress the carina, embrace the
upper part of the carina (3, Fig. 55) and are united to it by two
projections directed downwards and forwards (5d), which fit mto
deep grooves in the two halves of the carina. Two lobes at the
base of the upper borders of the ale (3, 6, ¢) directed backwards,
but not pouched, lie over the staminal column without touching it,

Fic. 55.— Ononis spinosa, L.

1,— Essential organs from a bud.

2.—Ditto, from a flower (x 7).

3.—Flower, from the side, after removal of calyx and vexillum. ;

4.—Some stamens, more magnified, to show the difference between the outer and inner filaments.

5.—Left ala, from the inside.

6.— Ditto, from the outside.

a, outer, b, inner stamen ;c, pollen, seen through the carina; d, alar processes pointing down-
wards and forwards ; e, lobe of the upper border of the ala, pointing backwards,

and can give little help in keeping the parts in their proper places.
The two alze never cohere with one another.

The upper borders of the carina cohere at first, leaving a small
opening at the tip, and the pollen is squeezed out as in Lotus. But
sooner or later after repeated depressions this suture ruptures, and
now if the carina be depressed the anthers themselves emerge. Ifthe
carina was not thrust down too far they return within the carina
when the pressure is relieved ; but if the carina was pressed violently
down, as it frequently is by bees, the anthers remain along with the
stigma partly or wholly exposed, |

a a ee

Vea oe

We

cmt

aa.

partrun] § THE MECHANISMS OF FLOWERS. 175
F

_ We must, therefore, take young flowers, to see the squeezing
out of the pollen. Thus the flowers of Ononis afford a stage inter-
mediate between Lotus with its piston-mechanism, and Melilotus in
which the reproductive organs simply emerge from the carina.
In regard to the formation of the “piston,” Ononis stands
between Lotus and Anthyllis. In Lotus the five outer filaments,
which alternate with the petals, are thickened at their ends to
express the pollen; in Anthyllis the ends of the filaments are all
_ thickened alike ; in Ononis they are all thickened, but the outer
whorl much more so than the inner. While the outer stamens thus
perform the function of a piston to a greater extent than the inner,
' the inner (1b) produce pollen in much larger amount than the outer
(la). This is an interesting step towards separation of the two
_ whorls of stamens for two distinct purposes.

i Though the flowers of Ononis possess no honey they are visited
_ by numerous bees, but in the number of their visitors they are far
behind Lotus, which has abundant honey. It is curious that not only
female bees but males also often visit several flowers in succession
-and perform all the actions of sucking. They have obviously no
outward token of the lack of honey, but must discover it by
experience. The females, after making sure that there is no honey,
take to collecting pollen ; the males, on the other hand, abandon the
' flowers after a few vain attempts, though they may remain some
time about the plant in pursuit of the female. The visitors are ex-
usively bees, and mainly forms with abdominal collecting-brushes,

A. Bees with abdominal collecting-brushes : (1) Osmia aurulenta, Pz. 9
(Thur.), ab. ; (2) O. wenea L. 9, freq. ; (3) Megachile versicolor, Sm. (Haar) ;

(4) M. pyrina, Lep. 2 ¢, freq.; (5) M. circumcincta, K. 9, ab. ; (6) M
maritima, K. 9; (7) Anthidium manicatum, L. 2 g, ab.; (8) A. punctatum,
tr. 2 ¢; (b) Bees with tibial pollen-baskets: (9) Apis mellifica, L. § ; (10)

- Cilissa leporina, Pz. 2 ; (11) Anthophora quadrimaculata, Pz. 9 ¢, ab. (Thur.) ;
_ (12) Bombus lapidarius, L. §; (13) B. terrestris, L. 9.

a

; Ononis repens, L., is also visited exclusively by bees (590, II.
ip. 254).

r According to Bentham, most species of Ononis in southern

Europe are liable to abortion of the corolla in spring, and cleisto-

_gamic self-fertilisation then takes place (399, p. 67; 531, p. 312).

Parochetus, Ham., has eptogemic flowers, according to Kuhn.

93, MEDICAGO SATIVA, eelay Wee as the mechanism of this
flower has been several times the subject of careful study, it is by

176 THE FERTILISATION OF FLOWERS. [PART III.

no means fully explained yet. I hope at least to advance our know-
ledge of the means by which the elastic tension of the parts is
produced and controlled. Medicago sativa has, like Sarothamnus

scoparius and Genista tinctoria, explosive flowers. As in these

latter, the staminal column before explosion is inclosed within

the carina, whose upper edges cohere together; and when an

insect presses down the carina the column not only emerges but

springs violently up and is unable to return to its former place.

As in G. tinctoria, the reproductive organs after explosion are
pressed against the vexillum and are not affected by further insect
visits. But Medicago sativa differs from these two plants by having
both the elastic tension and the force which restrains it localised in
different parts of the flower.

Fic. 56.—Medicago sativa, L.

1.—Young (virgin) flower from below.

2.—Ditto, from above, after removal of the vexillum and the upper half of the calyx. |
3.—Inner view of right ala.

4.—Carina seen obliquely from above.

5.—Exploded flower seen obliquely from above ; the vexillum and upper half of the calyx ha
been removed (x 84).

a, calyx; b, vexillum ; ¢, ala; d, its claw; e, invaginated process of ala, directed inwards and

forwards ; f, its externa] opening; g, digitate process or lobe of ala, directed inwards and back- —

wards ; h, carina ; i, invaginated pouches in the carina, which receive the alar processes, (e); &, the
coherent filaments; 1, the upper free stamen ; m, entrances to the honey; , anthers; 0, stigma.

While in Sarothamnus it is the style only which acts as a
spring, in Genista tinctoria the column tends to spring upwards, and
the ale and carina together tend to spring downwards. In Medicago
sativa the elastic tension resides almost exclusively in the upper

stamens. ‘his can be shown clearly by dividing the upper from —

the lower stamens, whereupon the upper part of the bundle curves

still more strongly upwards, and the lower part sinks down till it

stands almost horizontal.
In Medicago sativa it is not the coherent upper margins of the

PART II. } THE MECHANISMS OF FLOWERS. 177
f

carina, as in Sarothamnus and Genista, which prevent the column
_ from springing up in the young flower, though these margins are
coherent here also, but we may separate them completely from one |
another without explosion taking place. The structures which
: "prevent it are two pairs of projections developed on the petals of
the carina and ale, which lie upon the column.
Two are directed forwards, and consist of deep pouches in the
‘superior basal angles of the carina (7, 4, 5) which meet in the
middle line above the column. Into these fit still deeper pouched
“processes of the ale (¢, 2, 5), which both connect the ale firmly
( eh the carina, and also help to strengthen the hold upon the
ome. These anterior pouches of the ale (e, 2,5) are only a
urther development: of those shallow depressions by means of which
Bie alee are united to the carina in Trifolium and Melilotus.
| Besides this anterior pouch, each ala possesses at the base of its
upper border a long finger-shaped process, which is directed back-
wards, and is a further development of that which we shall see
“appearing in Melilotus. The two processes (g, 2, Fig. 56) curve
upwards and inwards so that their ends almost meet in the middle
line above the staminal column.
___ If in a young flower we cut through the claw of the carina, the
_ column springs upwards to some extent, carrying with it the carina
and ale. If in another unexploded flower we carefully cut through
i one of the digitiform processes of the ale, the parts remain motion-
less; but on cutting the process of the other side explosion at
1 Bice follows. The pouched processes of the carina (7) are thus
' not sufficient to hold the column down without the aid of the
| processes (g) of the alse, nor are the latter sufficient after section
of the carina. Explosion can therefore be effected equally well by
| separating the anterior pouches (e, 2), by separating the digitiform
_ processes (g, 2), or, finally, by depressing the alz and carina.
If an insect inserts its proboscis in the middle line between the
| anterior pouches and the digitiform processes, or if it stands upon
the alze and thrusts its head in the middle line under the vex-
| illum, in either case explosion follows. The stigma (0, 5) projects
beyond the anthers, and, therefore, is the first to strike the under
) surface of the bee’s body or proboscis; an instant later the anthers _
' come in contact with an area close around the spot that the stigma
| touched, dusting it with fresh pollen. The first flower that the
i asect visits is, of course, not cross-fertilised, but as the bee with-
draws from the flower self-fertilisation inevitably occurs. Self-
rtilisation is undoubtedly efficient, for Hildebrand has shown that
N

178 THE FERTILISATION OF FLOWERS. [PART III,

flowers which wither unexploded when insects are excluded produce
seed by self-fertilisation.

In spite of their very accurate mechanism, I have observed by
watching insect-visitors that the flowers have two imperfections.
In the first place they continue to secrete honey after explosion,
and in the second, the young unexploded flowers very frequently
permit insects to obtain the honey without performing any service
in return.

It is plain that the continued secretion of honey after explo-
sion is detrimental to the plant; for it leads the insects to visit
exploded flowers instead of restricting their visits to flowers that re-
quire their aid. I have seen hundreds of hive-bees sucking honey
on exploded flowers, thrusting the proboscis laterally over one of
the alz, and not coming in contact at all withthe stigma or anthers,
which were pressed close up against the vexillum.

The other imperfection is also taken advantage of by the
hive-bee, as Henslow has remarked. The bee probably finds it —
unpleasant to have its proboscis struck by the exploding column
at each visit; for it prefers, even in the case of young flowers, to
insert its proboscis laterally close to one of the alz,so that no
explosion results. Although bive-bees are by far the most
numerous visitors of this flower, I have never seen them effect
explosion ; but I have often observed them from a short distance
acting in the manner just described. Though I have frequently
watched this plant, I have never succeeded in seeing explosion
actually performed, though the number of exploded flowers that
we meet with shows that it must take place very frequently.
Butterflies visit the flowers in great numbers, and it is doubtless
by them that explosion and cross-fertilisation are effected; but they —
are generally too wild to permit close observation of their move-
ments. Once I had a good view of Hesperia thawmas, Hufn., suck-
ing a young unexploded flower, but like the bees it inserted its
proboscis from the side and did not cause explosion. A fine needle
inserted in the middle line of the flower causes explosion, and the
thin proboscis of a butterfly is undoubtedly sufficient to do the same.

A. Hymenoptera—A pide : (1) Apis mellifica, L. %, s. very freq. ; (2) |
Megachile pyrina, Lep., s. B. Lepidoptera—(a) Rhopalocera: (3) Pieris
brassice, L.; (4) P. rape, L.; (5) P. napi, L., all three ab. ; (6) Vanessa
urtice, L.; (7) Colias hyale, L.; (8) Satyrus hyperanthus, L. ; (9) Tuyceena
argiolus, L. ; (10) Hesperia thaumas, Hufn. ; (6) Noctue : (11) Plusia gamma, L.

Fifteen additionsl visitors (eleven Apidae, three Lepidoptera, and Bembex
rostratus) are recorded in No, 590, 11.

- PART III. | THE MECHANISMS OF FLOWERS. 179

94. MepIcAGo FALCATA, L.—Though on the whole the flower
of this species resembles that of JM. sativa, it possesses certain
peculiarities which facilitate explosion, and make it more difficult
_ for bees to obtain the honey without releasing the column. For the
_ pouches directed forwards and the processes directed backwards on
the alz grasp the column less firmly, as may be seen in 2, Fig. 57,
so that a less pressure is followed by explosion; but on the other
hand a thin proboscis can pass more easily to the base of the flower
without bringing about explosion. The ale leave less room for a
proboscis to enter, as they are shorter and broader and rest on the

Fic. 57.—Medicago faicata, L.

; P —Flower, viewed obliquely from above.

— Ditto, after removal of calyx and vexillum, from above.

- 3 — Left ala, 4.— Carina.

a 5.—Exploded flower, after removal of vexillum, seen obliquely from ‘the right and above; the
olumn appears considerably foreshortened

a, calyx ; b, vexillum; ¢, pathfinder ; d, claw of ala; e, lamina of ala ; f, invaginated process of
ale directed forwards ; : 9, lobe of ala directed backwards ; h, coherent claws of earina; i, coherent
lamine of ditto; kk, carinal pouches, which receive "Ne processes f; 1, column; m, superior free
Stamen; nn, entrances to the oney ; 0, stigma. (xX 7

en tn
, a ai S
by ——f a

carina for a shorter space in their basal half. Accordingly, of the

gery many bees which I observed on flowers of M. falcata, I did not
ee one sucking or collecting pollen on unexploded flowers without
releasing the column, but I saw many Lepidoptera sucking without
causing explosion. The flowers of J. sativa seem fitted rather for
Seabsation by Lepidoptera, and those of MW. falcata rather for ferti-
sation by bees. And my lists may lead us to conclude that the
flowers of M. sativa offer special attractions for Lepidoptera, and
N 2

180 THE FERTILISATION OF FLOWERS. [PART II.

those of M. falcata, on the other hand, for bees; yet I am not able
to account for this difference in attractiveness.
Visitors, at Rehmberg, Thuringia, July, 1868 :—

A. Hymenoptera—Apide : (1) Apis mellifica, L. §, s., freq. ; (2) Bombus
muscorum, F. $,s.; (3) Rhophites canus, Ev. ? 2, +. ; (4) Cilissa leporina,
Pz. 2 ¢, s. and c.p.; (5) Andrena denticulata, K. 2, s.; (6) A. fulvicrus,
K. 92, .8.; (7) Halictus quadricinctus, F. 9, cp. ; (8) Nomada Solidaginis;
Pz. 9,8.; (9) N. varia, Pz. 9,8. ; (10) N. ferruginata, K. 9,s.; (11) Osmia
aurulenta, Pz. 9, s. and «p., ab. B. Diptera—(a) Bombyliide: (12) Sys-
teechus sulfureus, Mik., s.; (b) Syrphidw: (13) Helophilus trivittatus, F.
©. Lepidoptera—(a) Ehopalocera: (14) Hesperia, s.; (15) Lyceena, s.; (0)
Sphinges: (16) Sesia asiliformis, Rott., s.; (17) Zygeena carniolica, Esp., ab. ;

(c) Noctue: (18) Euclidia glyphica,. L., s. Four additional visitors (ia ry

doptera) are recorded in No. 590, II.

95. MerpICcCAGO LUPULINA, L.—The flowers ‘of this species,
whose upper stamens seem to possess very little elasticity, are —
exceedingly minute but yet attract many diligent visitors.

A. Hymenoptera—Apide : (1) Apis mellifica, L. §, s., very freq. (It is
characteristic of the honey-bee that it does not disdain even this flower’s tiny
store of honey. The whole inflorescence is pulled down by the weight of the
bee, which then sucks the flowers head downwards. It sucks a few flowers, at
most four, on one inflorescence, and then flies away to another plant of the same _
species ) ; (2) Andrena convexiuscula, K..9,s.; (3) A. xanthura, K. 9,¢p.; —
(4) Halictus flavipes, K. 9, c.p.; (5) Bombus agrorum, F.? §, s. B.
Diptera—Conopide: (6) Myopa buccata, L., s.; (7) M. testacea, L., s.
C, Lepidoptera—Rhopalocera : (8) Thecla rubi, L. 9, s.

Darwin also saw MZ. lupulina visited abundantly by bees. He i

found the plants very much less fertile when protected from insects
by a net.

96. MELILOTUS OFFICINALIS, Willd.—The mechanism of the flower —
resembles that of 7'rifoliwm repens, with certain slight variations.

The calyx is much shorter (only 2 mm. long) and at the same —
time wider, thus admitting insects with shorter tongues to the
honey, and also giving greater range of movement to the petals.
The alz and carina can rotate much farther downwards, since their
claws are not adherent to the staminal column as in 7. repens,
Their return to their former place when relieved from pressure is —
insured by two finger-like processes (/) which replace the pouches of
1’. repens at the superior basal angle of the ale; they grasp the
staminal column superiorly, and, when the carinz are drawn down,
they separate slightly but still remain closely applied to the

PART 111. | THE MECHANISMS OF FLOWERS. 181

-staminal column ready to spring back and grasp it as firmly
as before. The stigma projects further beyond the anthers

Fic. 58.— Melilotus officinalis, Willd.

1.—F lower, from the side.

2.—Ditto, from above, after removal of calyx and vexillum.

3.—Ditto, from the side, after depression of the al and carina.

a, anthers ; d, point of flexure of carina; e, depressions in the ale, whose inner surfaces are
_ connected with the outer surfaces of the carinal petals by interdigitation of their cells ; J, digitate
Seg of the superior basal angles of the ale ; g, column; hh, entrances to the honey; gr, style ;
, stigma.

than in J’. repens, so that self-fertilisation is rendered even
more unlikely.
Visitors : Hymenoptera—(a) Apid@: (1) Apis mellifiea, L. 9 very freq.,
| sand c.p. ; (2) Andrena dorsata, K. 9, s. and c.p.; (3) Heriades truncorum,
| LQ, cp. ; (4) Colioxys quadridentata, L. ¢,s.; (5) Osmia sp.; (b) Sphegide :
| (6) Ammophila sabulosa, L. g, s.; (¢) Tenthredinide: (7) Tenthredo sp.,
| vainly seeking honey.
_ 97. MeLILotus vuLGaRis, Willd (7. alba, Thouill.).—This
“Species is visited by the honey-bee, which I have found in
undreds busy sucking honey and collecting pollen on the plant :
also by Macropis latiata, Pz., and by Empis livida, L.

_ 98. TRIFOLIUM REPENS, L.—The floral mechanism is here
simpler than in Lotus, and is one of the simplest to be found
among Papilionaces. Stamens and pistil are inclosed in the carina ;
| when the latter is pressed down they protrude, but they return
_ within it when the pressure is removed, and the pollen is thus
i protected from the weather and from robbery. As in all other
Papilionaceous flowers which contain honey, the honey is secreted

182 THE FERTILISATION OF FLOWERS. [parr ut. —

by the bases of the cohering stamens, it surrounds the base of
the ovary, and can only be reached through two apertures, one on
either side of the base of the superior free stamen. An insect,
to reach the honey, must thrust its head in beneath the vexillum,
and must stand in doing this upon the two ale. In climbing
on to the ale and thrusting its head below the vexillum, it forces
up the latter and presses the ale and carina down; and the re-
productive organs, protruding from the carina, are forced up against |
the ventral surface of the insect. The organs all return to their |

Fic. 59.—Trifolium repens, L.

1.—F lower, from below.

2.—Ditto, from above, after removal of calyx and vexillum.
3. —Inner view of right ala.

ce’, pouched swelling.

former place when the insect leaves the flower; and cross-fertili-
sation takes place regularly, since the stigma projects slightly
beyond the anthers and therefore comes first in contact with the
ventral surface of the insect.

In addition to these characters, which Trifoliwm repens —
possesses in common with many other Papilionaceous flowers, the _
following are peculiar to itself: (1) the arrangements for excluding
certain short-lipped insects; (2) the conditions of rotation of the
alse and carina; (3) the provisions for bringing back the parts of —
the flower to their former place when pressure is removed.

(1) The calyx-tube, which surrounds the claws of the petals
and limits the movements of the vexillum and ale, is only 3 mm,

parr] | THE MECHANISMS OF FLOWERS. 183

long; so that the less specialised bees, such as Andrena and
Halictus, are not shut out from the honey.

q (2) The ale cohere with the carina at one point on each side
(¢, 2, 8, Fig. 59), so that both rotate upwards and downwards
together; this rotation is facilitated by the very thin and weak
claws of the alz and carina, which adhere for the greater part of
their length to the staminal tube, but are free anteriorly. Since
_ the alz project considerably beyond the carina, they play the part
| of a long lever-arm in this action. The long anterior end of the
| yexillum has a similar action.

(8) The return of the parts to their original position is brought
- about chiefly by the vexillum and the alz, in addition to the part
_ played by the calyx-tube. The strong, broad claw of the vexillum
overlaps the other petals and the reproductive organs, being
_ closely applied to them above and at the sides; by its elasticity it
? returns forcibly to its own place after it has been moved, and forces
the organs within into their place also; the anterior part of
the taminal column is also kept in check by the ale, whose
superior basal lobes are modified into two vesicles (v) which lie close
; _ together upon the upper part of the column.

_ Visitors: A. Hymenoptera—Apide : (1) Apis mellifica, L. §, very ab., s.
_ and cp. ; (2) B. pratorum, L. 9%, s.; (8) Megachile Willughbiella, K. ¢; (4)
Halictus tarsatus, Schenck, ?, s. ; (5) H. maculatus, Sm. 9, ep. ; (6) Andrena
| fulvicrus, K. 9,8. B. Diptera—(a) Syrphide: (7) Volucella bombylans, L.,
| 8.3 (b) Conopide : (8) Myopa buccata, L., s.; (9) M. testacea, L.,s. C. Lepid-
re ptera—Fhopalocera : (10) Pieris brassice, L., s. Of these visitors it is only
the bees that act in the manner described and effect cross-fertilisation regularly ;
| i s other visitors only do so occasionally. See also No. 590, I1., and No. 609.

The Dutch Clover was one of the first Papilionaceous
flowers in which the necessity of insect-visits for full productive-
ness was demonstrated. Darwin found that when insects were
xcluded by means of a fine net the plant was only one-tenth
as productive as when insects were freely admitted (152).

99. TRIFOLIUM FRAGIFERUM, L.—This species agrees generally
‘in the characters of its flower with 7. repens ; but the flowers are
‘much smaller, the calyx-tube is only 2 mm. long, and the ale are bent
‘outwards. I have seen the hive-bee visiting its flowers abundantly.
‘Though the hive-bee as a rule keeps very strictly to one species
| of flower for a time, yet, where 7. fragiferum and T. repens grow
_ together, it visits the flowers of both indiscriminately.

184 THE FERTILISATION OF FLOWERS. [PART III.

100. TRIFOLIUM PRATENSE, L.—The honey lies at the base of a
tube, 9 to 10 mm. long, formed by cohesion of the nine inferior
stamens with each other and with the claws of the petals; it is
secreted by the bases of the stamens, and accumulates in the tube
around the base of the ovary. But while in Trifolium repens, as in
Lotus and most other Papilionacez, only two small openings, one on
either side of the base of the superior stamen, give access to the
honey, and compel the bee to thrust its proboscis down to them
outside the staminal tube, in 7’. pratense the bee’s proboscis, after
being thrust under the vexillum, passes at once into the staminal

|! Hf ) ih ;

Fic. 60.—Trifolium pratense, L.

1.—F lower, from below.

2.—Ditto, from above, after removal of the vexillum. :

3.—Anterior part of flower, twice as much magnified ; the edges of the carina have been forced
apart. .
4.—Right ala, from within. ‘

5.—Right half of the carina, from without. (The claws of 4 and 5 have been broken short off.)

6.—The essential organs emerging from the depressed carina.

a, calyx; b, tube formed by coalescence of the nine filaments with the claws of the vexillum, ale,
and carina; c, vexillum ; d, concave part of the inner side of the ala; e, lower border of ala, bent
outwards ; f, outward surface of ala; g, pouched swelling on the base of the ala; h, carina; i, style ;
k, superior free stamen ; 1, stigma; m, anthers; n, point of union between ale and carina; 0, point
of flexure of the carina; p, part of the upper border of the ala, bent outwards; q, downward
extension of vexillum.

tube, to which in this case the claws of the petals are adherent.
The insect’s proboscis, passing down the tube in the middle line
superiorly, would be impeded by the superior stamen which is
inclosed in the tube if this retained its normal position ; but its two
ends only are situated in the middle line, and the rest of the stamen
lies wholly to one side.

From the anterior end of the common tube come off the

|
:
:

~ PART III] THE MECHANISMS OF FLOWERS. 185

various organs as follows: (1) The broad base of the vexillum,
which is continuous with the superior and lateral portions
of the tube, and even with part of its inferior aspect by means
of an expansion (¢) just at the base of the free limb. (2) The
base of the carina, which is attached to the inferior part of the
edge of the tube in the interval left by the vexillum: though
not half so broad as the base of the vexillum, it is broad and strong
- enough to return quickly to its place after being bent downwards.
| (3) The two al, whose flexible claws spring from the common
' tube; the lamina of each bulges out at its base (g) more
distinctly than in 7’. repens, to cover over the top of the staminal
- column and help to keep it and the petals in their proper relative
_ positions. (4) The ‘staminal tube, which is split superiorly to
admit the free tenth stamen, and which divides in the hollow of
the carina into stiff filaments which curve upwards and are slightly
thickened at their ends. |
; In the midst of the stamens lies the style, curving upwards till
_ its stigma slightly overtops the anthers.
If now a bee inserts its proboscis beneath the vexillum, while
_ it clings with its forelegs on to the ale (which are coherent with the
carina) resting its middle and hind legs on a lower part of the
inflorescence, the carina and ale are drawn downwards, and the
stigmas and anthers are thrust up against the under side of the
_ bee’s head; the stigma, standing highest, receives the pollen
_ brought by the bee, and instantly afterwards the anthers dust the
bee with fresh pollen. Cross-fertilisation is thus insured ; self-
fertilisation may take place as the bee draws back its head, but is
__ probably neutralised and superseded by the immediately preceding
cross-fertilisation.
_ Inorder to reach the honey in this way, an insect must possess
_ a proboscis at least 9 to 10 mm. long. The pollen is accessible to
all insects which can press down the carina; and it is clear that
_bees when collecting pollen on the flower rericrn cross-fertilisation
as well as when sucking honey. The red clover, like most flowers
_ whose honey lies more than 7 to 9 mm. deep, is liable to the attacks
of Bombus terrestris and other insects which use the holes that B.
) terrestrishas made. The small flowers of clover become conspicuous
__ byaggregation into heads, and contain very abundant honey.

A. Hymenoptera—A pide : (1) Bombus silvarum, L. 2 (proboscis 14mm.) !
(2) B. ian abc L. $2 (10—14)! (3) B. Rajellus, Ill. § § agape
_ (4) B. agrorum, F. § 2 (10-—15)! (5) B. senilis, Sm. Q (14—15)! (6) B

186 THE FERTILISATION OF FLOWERS. [PART IIT,

confusus, Schenck, § 2 (12—14) ! (7) B. muscorum, F. 9 (13—14)! (8) B.
fragrans, K. 9 (15)! (9) B. (Apathus) rupestris, F. 9 (14)! (10) B. vestalis,
Foure. 9 (12) ! (11) B. campestris, Pz. Q (10—12) ! (12) B. Barbutellus, K.?
(12) ! all s, some also c.p. ; (13) (Bombus terrestris, L. [7—9]), bites through
the tube and so reaches the honey with some delay,—it has, however, the
advantage of obtaining honey even from unexpanded flowers ; (14) (B. pratorum,
L. % [8]), behaves in the same way) ; (15) Apis mellifica, L. § (6), usually
visits the red clover only for its honey, which its proboscis is not able to reach
in the legitimate manner,—yet I have now and then seen hundreds of honey-
bees on a patch of red clover, all busy collecting pollen ; (16) Anthophora
pilipes, F. 2 (19—20), s.! (17) Eucera longicornis, L. 9 ¢ (10), s.! (18)
Cilissa leporina, Pz. 2 (33), c.p.! (19) Andrena xanthura, K. ? (3), ep. !
(20) A. Schrankella, Nyl. 2 (4); (21) A. fulvicrus, K. 2 (3%); (22) A.
fasciata, Wesm. 2 ¢ (3—4),—all three sought in vain for honey, their collecting-
hairs remained free from pollen ; (23) Colletes fodiens, K. 2 (24), ep. ! (24)
Halictus flavipes, K. 2 (23), ¢.p.! (25) Anthidium manicatum, L. 9 ¢ (9—10),
s.! (26) Megachile circumcincta, L. @ (11), s. and c.p.! (27) Osmia enea,
L. 9 (9—10), s. and c.p.! (28) Diphysis serratule, Pz. 9 (7—8) cp.! B.
Diptera—(a) Bombyliide: (29) (Systeechus sulfureus, Mikan [6—7]); (0)
Syrphide : (30) (Volucella bombylans, L. [7—8]) ; (¢) Conopide : (31) (Sicus
ferrugineus, L. [6—7]),—I have seen all these three flies thrusting their tongues
beneath the vexillum, though their tongues are too short to reach the honey in
the legitimate way). C. Lepidoptera—(a) Rhopalocera : (32) Pieris brassice,
L. (15); (83) P. rapze, L. ; (84) Vanessa urtice, L. (12) ; (85) Satyrus Megeera, L. ;
(36) S. Janira, L. ; (37) Hesperia sylvanus, Esp. ; (38) H. thaumas, Hfn. ; (0)
Noctue : (39) Plusia gamma, L., all s.

Trifolium badium, Schreb.—The flower is in like manner
adapted for Lepidoptera. On the Alps I found it visited by four
Apide and eleven Lepidoptera (609).

Trifolium alpestre, L.—The flower is similarly arranged, and was
seen to be visited by two species of Apidze and nine Lepidopter
(Weit. Beob. I1.).

Kuhn describes cleistogamic flowers in Trifolium (399), and
T. polymorphum is cleistogamic according to Darwin (Forms of
Flowers, 2nd ed.).

Trifolium alpinum, L., T. pallescens, Schreb., and 7’, nivale, Sieb.

(7. pratense, L., var. nivale), are described in my Alpendblumen
(No. 609).

101. TRIFOLIUM ARVENSE, L.—The tube is hardly 2 mm. long.

Visitors: A. Hymenoptera—-(a) Apide: (1) Apis mellifica, L. %; (2)
Bombus Rajellus, Ill. 9 $, very freq. ; (3) B. lapidarius, L. $; (4) Cilissa
leporina, Pz. 2 ; (5) Andrena xanthura, K. 9; (6) Halictus zonulus, Sm. 9 ;
(7) H. quadricinctus, F, 2; (8) Colletes marginata, Sm. ¢; (9) Diphysis
serratule, Pz, ¢; (10) Osmia ceementaria, Gerst. ¢ (Thur.) ; (11) Megachile
maritima, K. ¢, all sucking only ; (b) Sphegide: (12) Psammophila affinis,
K. 2,8. B. Lepidoptera—(13) Hesperia thaumas, Hufn., s.

f

-

PART III. | THE MECHANISMS OF FLOWERS. 187

102. TriroLiIuM RUBENS, L. (Thuringia, Rehmberg near

_ Mublberg).—This species shows certain adaptations for Lepi-

doptera as well as for bees; I have found it visited by six species

_ of Bombus and Anthophora, and by seven species of Lepidoptera.

103. TRIFOLIUM FILIFORME, L :—
Visitors :—Apide ; (1) Apis mellifica, L. §,s. ; (2) Halictus albipes, F. 3,

_s.; (3) H. cylindricus, F. 9, ¢.p. Lepidoptera: (4) Lyczna egon, s.v.s.

104. TRIFOLIUM MEDIUM, L. :—

Visitors: Apidw: (1) Andrena dorsata, K. 2, ¢.p. ; (2) Bombus agrorum,
F. 9, sucking normally, Eleven additional visitors are recorded in No. 590, 11.

105. TRIFOLIUM PROCUMBENS, L. :—

Visitors: Apide: (1) Apis mellifica, L. §, s.; (2) Halictus flavipes,

_K, 9,8. Five additional visitors are recorded in No. 590, 11.

106. TRIFOLIUM MONTANUM, L.—I have found this species
visited in Low Germany by four Apidz, one Sphegide, and four

iF Lepidoptera (590, I1.); on the Alps by eight Apide and eight
_ Lepidoptera (609). Besides the adaptations to bees usual in

Papilionacee, it shows an adaptation to cross-fertilisation by

_ Lepidoptera, the closely folded vexillum bringing the insect’s
proboscis in contact with the stigma and anthers.

Genistec.

107. Lupinus LuTEus, L.—The flowers of Lupinus luteus, like

_ those of Ononis spinosa, are devoid of honey and are provided
_ with a piston apparatus; they present the following peculi-
arities:—The ale are coherent with one another at the an-
__ terior border, and each possesses a lateral fold near its base, fitting
_ into a depression in the carina. They surround the carina as in

Lotus, but are flat instead of being strongly convex, and since the

sides of the vexillum are bent backwards the flower is more con-

" spicuous from the side than from the front. The division of labour

which began to be marked in Ononis between the two whorls of
stamens, one whorl producing the pollen, the other pressing it
forwards, is much more complete in Lupinus (1, 2, Fig. 61). The
anthers of the five outer stamens are much larger than those of
the inner ; they dehisce within the bud, while the others are much
shorter and very far from maturity (1, Fig. 61); and then after

placing their pollen in the apex of the carina, they wither

188 THE FERTILISATION OF FLOWERS. | PART III.

completely, and remain in the wide lower part of the carina ~
(2, Fig. 61). The five inner anthers now begin to grow rapidly, and
squeeze the pollen in the point of the carina more by means of their
anthers, which remain spherical, than by the thickened ends of
their filaments; they thus do the work of a piston, except the
superior stamen (1), which remains inferior to the others in length
and thickness. |

Fic. 61.—Lupinus luteus, L.

1.—Essential organs, from a bud ; the outer anthers are dehiscing.
2. Pic wre from a flower.
2, 4, 6, 8, 10, the tive outer ; 1, 3, 5, 7, 9, the five inner stamens; 2, stigma.

The spherical stigma is surrounded at its base, like that of the
Laburnum, by a ring of stiff erect hairs which prevent or limit the
application of its own pollen.

I have noticed only the following visitors :—

Hymenoptera—A pide: (1) Apis mellifica, L. %, ab., c.p.; (2) Bombus
lapidarius, L. §, scarce, c.p. ; (8) Megachile circumcincta, K. ?, ¢.p.

The flower of Zupinus albus differs in certain points from the
preceding species (cf. Delp. 178, pp. 46, 47).

Lupinus, sp—Mr. Swale observed that in New Zealand cultivated
varieties of Lupinus were unfertile unless he released the stamens
with a pin. In England, according to Darwin, the Lupines are
fertilised by humble-bees, not by hive-bees (152).

108. GENISTA TINCTORIA, L.—In the young bud the ten stamens
are distinctly seen to form two whorls (1, Fig. 62). The five
anthers of the outer whorl (2, 4, 6,8, 10 in 1, Fig. 62), overtop
those of the inner, and the four superior ones are the first to

PART IIT. | THE MECHANISMS OF FLOWERS. 189

ripen. In the bud, they are already on the point of dehiscing, while
those of the inner whorl have attained scarcely a quarter of their
_ full size. The ten stamens, and the style, which projects far beyond
_ them, are all inclosed by the carina, whose two petals cohere along
_ both their upper and lower margins. As the four superior anthers
of the outer whorl dehisce introrsely and then wither, their pollen
remains lying above the style, which courses along the lower edge of

Fie. 62.—Genista tinctoria, L.

, —Essential ge from a young bud.

- 2.—Position of the parts inclosed in the carina of a young (virgin) flower.
i —Inner view of right ala.

4.—Exploded flower.

5.—Young (virgin) flower, from above, after removal of calyx and vexillum.

6.—Ditto, after the carina has been cleft to near its apex by pressure, from above.
7 —Young flower, from above, after removal of vexillum and ale.

8.—Anterior half of a young flower, cleft so far that explosion must result; from above, twice
as iach magnified
; a, coluinn ; b, the four outer stamens, which remain short (2, 4, 8, 10, in Fig. 3 ce, the five
inner stamens qa. 3, 5, 7, 9); d, the stamen of the outer whorl which remains below the s tyle; e, tip
of style; f, stigma : 9; pollen ; h, lateral fold of carina into which a fold (h’) of the corresponding
ala fits ; kl, non-coherent part "of the upper borders of the carinal petals; m, ala; n, carina, ends of
f laments ; q empty, shrivelled anthers ; 7, pollen; s, stigma; ¢é, claws of ale.

_ the carina, and it gets pushed forward into the apex of the still
elongating carina by the inner stamens which quickly extend
beyond the now empty outer stamens. The inferior stamen of
the outer whorl (6 in 1, Fig. 62), which lies immediately below the
‘Style, remains closed when the other four dehisce, and it grows to the
ame length as the five inner stamens and dehisces with them.

190 THE FERTILISATION OF FLOWERS. [parr 1.

If it dehisced along with the other four stamens of its own
whorl and then withered, its pollen would lie useless in the lower
part of the carina, a little in front of its middle point, and would
never be pressed forward ; but since it grows to the same length as
the inner stamens and dehisces simultaneously with them, its
pollen unites in great part with that of the two neighbouring
stamens (5 and 7 in 1, Fig. 62), and is heaped with it above the
style.

The inner whorl of stamens and the inferior stamens of the
outer whorl dehisce and wither a short time before the vexillum
expands. The position which the organs occupy at this time
within the carina may be easily seen by holding the carina up to
the light, and is represented in 2, Fig. 62.

The carina still forms a much compressed sheath, closely
surrounding the style and the pollen of all the ten stamens which is
heaped above it. It is kept horizontal by the action of two equal
and opposite forces. The column of stamens with the contained
style possesses a tension upwards, so that if it be freed from the
surrounding petals it springs up close to the perpendicular vexillum.
The claws of the ale and of the two petals which form the carina
- possess a downward tension, and if the upward pressure of the style
is removed, they suddenly bend downwards and place the ale and
carina in a vertical position. The ale are kept in connection
with the carina by means of a bulging protuberance at the base
and near the upper border of each (h’, 3, 5, 6), which les in the
angle between the upper border of the carina and another pro-
tuberance directed outwards and upwards from each half of the
carina near its base (h, 7).

The opposite tensions balance one another so long as the upper
borders of the carina cohere together (7, 5) and the pouched lobes of
the alee (m, 5) meet one another above the staminal column.

As soon, however, as an insect places its feet upon the alee and
thrusts its head beneath the vexillum, the pouched lobes of the alv
slip down below the staminal column (m, 6); at the same time the
union between the upper borders of the carina is ruptured from
behind forwards by the pressure of the essential organs in its posterior
part, and as soon as the splitting reaches the tip of the style the
two opposite forces are set free, and the staminal column springs
upwards while the alz and carina spring downwards. If we hold
the flower in one hand, and press down the tip of the carina with
a needle or a pencil-point, we see clearly the split spreading
forwards, and the pouched lobes of the ale separating, so that the

PART IIL. | THE MECHANISMS OF FLOWERS. 191

flower passes from the young, closed state (Fig. 62, 5) to the half-
opened state (Fig. 62, 6); if we press a little harder, the split
passes forward beyond the tip of the style (Fig. 62, 8), and in the
“same instant the column flies upwards to the vexillum, scattering
-a cloud of pollen, and the alz and carina spring down into the
vertical position.

If an insect performs the above operation while standing on the
alz and thrusting its head beneath the vexillum, the column is pre-
vented from springing up to its full height; it cannot scatter a cloud
of pollen into the air, but the ascending style forces its stigma and
instantly afterwards the mass of pollen against the under side of
_ the insect. If the insect has been dusted with pollen in a pre-
¢ viously visited flower, cross-fertilisation is thus effected ; if not, the
_ stigma is dusted with its own pollen as the insect creeps backwards
: out of the flower. Whether self-fertilisation occurs in absence of
insects is a point that has still to be settled by experiment.
_ Specimens with young virgin flowers which I left standing in
water for over fourteen days withered without either exploding
or producing seed.

Since the flowers contain no honey, and expend all their pollen in
_asingle explosion, after which the staminal column and style are
concealed by the vexillum which closes over them as in the bud,
. peey.can only offer attractions for pollen-collecting insects, viz. :
female bees busy with the care of their young ; and even these are
only permitted a single visit. The flowers, however, are visited by
very various insects, which fly away after a vain attempt to obtain
pollen or honey, I observed the following visitors in sunny weather
in July, 1869, on a stretch of land covered with G. tinctoria near
- Brilon and Warstein :—

+4 a Hymenoptera—(a) Apide : (1) Megachile circumcincta, K, ?, very ab.,
.; (2) M. centuncularis, L. 9, very ab., c.p.,—the males occasionally ek
in Bin for honey ; (3) M. villosa, Behunok. 2, one specimen, c.p.; (4) M
versicolor, £ Em. ?, freq. ; (5) M. Willughbiella, K. ¢; (6) Diphysis sentatalen,
Pz. $; (7) Anthidium punctatum, Latr. ¢,—the last three come in vain
arch for honey ; (8) Apis mellifica, L. §, ab., c.p. ; (9) Bombus terrestris,
9 , scarce, ¢.p. ; (10) Colletes Davieseana, K. 2, .p. ; (11) Andrena albicrus,
| K. ¢; (12) A. fulvescens, Sm. ¢,—both vainly seeking honey; (13) A
of hae ¢ ; (14) A. fulvicrus, K. 2; (15) Halictus rubicundus, Chr. @ ;
¢ 6) H. albipes, F. 9; the last four scarce, »c.p. (all, including the honey-
seeking males, caused the flowers to explode, and effected cxbas feat Taal: (b)
Vespide : (17) an bealyy trifasciatus, F. 9. B. Diptera—(a) Conopide : (18)
) Sicus ferrugineus, L.; (19) Myopa testacea, L. ; (b) Syrphidw: (20) Chryso-
_ toxum pbicinctum, LC. Lepidoptera—Rhopalocera ; (21) Satyrus Megeera,

{-
if
ie
if

ee THE FERTILISATION OF FLOWERS. _. [part 11.

L.—the last five obtained neither honey nor pollen, and did not cause the
flowers to explode. D. Coleoptera—Chrysomelide: (22) Cryptocephalus
sericeus, L. ; (23) Cr. vittatus, F.; (24) Cr. morei, L., feeding on the tissues of
the flower. Four additional visitors are recorded in No. 590, II. .

This list is of special interest, as it shows that flower-loving
insects do not restrict themselves by hereditary instinct to those
flowers which are most useful to them, but that they search widely
for their food in flowers, and so very often seek in vain.

Of the pollen-collecting bees, those with abdominal collecting-
brushes have the easiest work, since the explosion of the flower
forces the pollen directly on to the collecting-hairs ; they are also
the most useful to the plant, as they fly from flower to flower with
least loss of time. :

109. GENISTA ANGLICA, L.—In this species the. opposed
tensions of the column on the one hand and the ale and carina on

Fic. 63.—Genista anglica, L.

1,—Young (virgin) flower, from the side.

2.—Ditto, from the front.

83.—Inner view of right ala.

4.—Exploded flower ; the style is less recurved than usuai.
5.—Exploded flower from the left ; a more normal specimen than 4.

the other are much less marked. When the flower explodes, the
carina and alze move only a short way downwards, and the whole
column does not bend upwards, but only the style, whose tip curves
inwards also. The only visitors that I have noticed are bees with
tibial and femoral collecting-baskets. But it would be premature
to conclude, even in the case of G. tinctoria, that because its
flowers are chiefly plundered and fertilised by bees with abdominal
brushes, they have been specially adapted only for those bees.

I had a most favourable opportunity of watching the actions
of the hive-bee on flowers of G. anglica one sunny morning,
May 3, 1871. It was the first sunshine after long-continued rain,

PART II. | THE MECHANISMS OF FLOWERS. 193

--and so all the flowers were still unfertilised. The bees flew
humming from one flower to another, clung by their legs to the
alee, and thrust their heads with outstretched proboscis beneath
the vexillum while the abdomen hung down. While the head
and its proboscis were thus placed just as if they were sucking
honey from the base of the flower, the midlegs were in active
movement, scraping pollen into the baskets on the hindlegs. On
May 14, 1871, I again watched the hive-bee at work, when most
_of the flowers had now exploded. A single bee flew on to ten or
twenty plants, whose flowers had all been fertilised, without
stopping on any flower. At last it found a young unfertilised
flower, on which it eagerly descended. This long search and
occasional descent upon young unfertilised flowers was frequently
_ repeated ; but sometimes I saw a bee, after seeking in vain for
_ young flowers, settle on an old exploded one, and insert its pro-
boscis as if the flower contained honey. Sometimes also I saw a
hive-bee visit a young flower without causing it to explode.

Besides the hive-bee, I have only seen Andrena fulvicrus,
_ K. ?, A. nigro-aénea, K. 2, and Halictus cylindricus, F. 2, collecting

_ pollen on this plant, all very frequently.

110. Genista pILosa, L.—The mechanism of this flower is like
that of G. anglica. It has been thoroughly described by Delpino,
_ who found the plant sterile to its own pollen (178, 360). I have
only seen the honey-bee collecting pollen on it.

- 111. Cytisus Lasurnum, L.—In the flowers of Cytisus La-
} burnum, as in those of Melilotus and Trifolium, the reproductive
organs simply emerge from the carina and return within it. The
connection of the ale with the carina is not a firm one, being
formed simply by a shallow bulging depression in each ala (e, 1)
which fits into a corresponding depression on the side of the
carina ; yet this is quite sufficient, as a slight pressure suffices to
epress the ale and carina. The elasticity of the carina is small ;
| it is sufficient to bring the carina back to its original place after
repeated slight depressions, but not sufficient if the carina be
| pressed far down. Accordingly, after repeated visits of humble-
| bees the essential organs protrude freely from the slit.
| The flowers are characterised by a peculiar kind of proteran-
drous dichogamy. Immediately before the bud expands, the stigma
} lies in the apex of the carina surrounded by transparent, stiff, erect
| ib hairs ; these overtop the stigma, and in the young flower they
O

194 THE FERTILISATION OF FLOWERS. [PART III.

bend over its papillar surface, protecting it from immediate con-
tact with the insect-visitor. Gradually these hairs wither, so that
in older flowers the stigmatic papillz are freely exposed (5, Fig. 64),
and at the same time the style bends more and more inwards, so
that the stigma protrudes farther and farther from the carina.
_Cross-fertilisation is thus insured and self-fertilisation prevented
in case of insect-visits, while spontaneous self-fertilisation is also
prevented in absence of insects.

The most remarkable peculiarity in the flowers of the La-
burnum is that, like those of Orchis mascula, O. morio, &c., they
only supply nectar inclosed in cellular tissue. The ordinary .
secretion of honey and the ordinary means of access to the honey —

Fic. 64.—Cytisus Laburnum, L.

1,—Basal part of an old flower, seen from above, after removal of calyx and vexillum.

2, 8, 4.Stigmas of younger flowers.

5.—Stigma of an old flower.

aa, cut base of calyx; b, point of insertion of vexillum ; ¢, fleshy eminence, anterior to insertion —
of vexillum, which is probably probed by insects ; d, claw of ala; e, shallow pouched depression of
saps which fits into a corresponding depression on the upper surface of the carina; f, carina;
g, its cleft.

are here wanting, and the stamens are monadelphous; but in~
front of the point of attachment of the vexillum is a thick, fleshy
swelling, so rich in honey that if a fine glass tube be inserted in it
a column of clear fluid ascends the tube. The vexillum is marked
with dark lines pointing towards the base of the flower, which can
only be interpreted as pathfinders, and an insect’s proboscis inserted
beneath the vexillum comes without fail to the nectary. I have
seen both bees and butterflies inserting their tongues into numerous -
flowers in succession, spending some time on each; the bees had
their pollen-baskets empty, and were therefore not engaged in
collecting pollen, It seems therefore impossible to doubt that the
swelling at the base of the vexillum is actually pierced by bees
and butterflies for the sake of its secretion. ;

parrius) THE MECHANISMS OF FLOWERS. 196

) A. Hymenoptera—A pide : (1) Bombus lapidarius, L. 9 $, sometimes s.,
- sometimes c.p.; (2) B. terrestris, L. 9, s.; (3) Andrena atriceps, K. 2 ¢,s.;
(4) A. albicans, K. 2, c¢.p.; (5) A. xanthura, K. 2, c.p.; (6) Apis mellifica,
L. $,¢p., very ab. B. Lepidoptera—Noctue: (7) Plusia gamma, L., s., freq:
©. Coleoptera—Nitidulide: (8) Meligethes, creeping about within the
- flowers.

Cytisus sagittalis, Koch, is visited by bees only ; I have noted
- eight different species upon its flowers (590, I1.).

In Cytisus canariensis, L., and C. albus, Link., according to
Hildebrand, the carina bends down slightly under pressure, and
the anthers and style first move slightly downwards with it, and
then spring upwards so that the pollen flies out and part of
it is applied without fail to the stigma (No. 346). It is, however,
hardly conceivable that such an action effected by insects should
lead only to self-fertilisation.

_ 112. Cytisus (SAROTHAMNUS) scopARIUS, Koch.—The flowers,
_ like those of our species of Genista, are explosive and devoid of honey.
| Darwin noticed that the flowers do not explode spontaneously, and
_ scarcely set a single capsule if protected from insects; but that
when an insect visits the flower, first the short stamens explode, dust-
ing it with pollen below, then the longer stamens, dusting it above,
and that finally the pollen applied to the under side of the insect
_ by the shorter stamens fertilises those stigmas which are not
_ covered with pollen at the moment of explosion.

__ I have observed the way in which insects operate on the flower
most closely in the case of the hive-bee. The bee, on alighting,
_ grasps the alz with its mid and hindlegs, thrusting its forelegs and
_ head below the middle of the vexillum. The ale and with them
‘the carina are thus pressed forcibly down, and the united upper
+3 “margins of the carina split asunder from behind forwards. [The
alze are connected with the carina by means of a fold ( jf; 4b) which
Biches j in the angle between the upper edge of the carina and the
“sharp pouched protuberance at its side (7; 4, 4c, 6)]. As soon as
I ithe split has extended midway, the five shorter stamens spring out ;
_ they had dehisced in the bud, pressing their pollen against the
closed upper edge of the carina (5, Fig. 65), and now they force
} ip of their pollen against the under side of the bee. The shock
- not enough to drive the bee away; at most it pauses for a
‘moment, and then resumes work with increased diligence. The
we ‘split now quickly extends further, and it has scarcely reached the

place where the tip of the style lies than a second and much
| E ; 0 2

-e

196 THE FERTILISATION OF FLOWERS. [PART III.

more violent explosion occurs. The style lies until this second
explosion, along the lower part of the carina, and its flattened
terminal part lies in the apex of the carina above the longer
anthers which have long since dehisced; when freed from
restraint it curls inwards, forming more than a complete spiral
turn (7, Fig. 65). As soon as the split extends to the point where

Fic, 65.—Sarothamnus scoparius, Koch.

1.—Young (virgin) flower, from the side.

2.—Ditto ; the vexillum is rather more erect, and shows the pathfinder.

3.—Ditto, after removal of the vexillum, from above.

4.—Ditto, after removal of the ale also.
- 4b.—Left ala, from the inside, showing the concavity /, which rests upon the convexity f’ of the —
carina,

4c.—The convex swelling of the carina, viewed from the front.

5.—Position of the essential organs in the young flower.

6 ee after explosion of the short stamens, from the side; the vexillum and ale have been
removed.

7.—Position of the parts after complete explosion.

8.—Staminal tube, slit open immediately to the right of the superior median stamen (1).

9.—End of the style, from within. :

pl, flattened portion which expels the pollen; n, stigma.

the end of the style lies, the style springs up, striking the back of
the bee with its stigmatic tip; almost in the same instant, the
greater part of the pollen carried away by the expanded end of
the style is shed upon the bee’s back, and at the same time the
long stamens, to which some pollen still adheres, curl inwards and
issue from the flower. When, as often happens, the bee is so held
that the stigma cannot slip off at the side but remains pressed

parr] = THE MECHANISMS OF FLOWERS. 197

against its back, it stays for some seconds motionless as though
stunned, and then turns round, freeing .itself from the style,
and begins to gather pollen upon the anthers with its mouth
and legs.

The behaviour of humble-bees is on the whole similar to that
of the hive-bee. But while the hive-bee is only strong enough
_ to cause the flower to explode, often causing only the shorter
stamens to escape, humble-bees are able easily to force open any
_ flower in which the vexillum has become erect; and they may be
seen not unfrequently to break open, though with considerable
effort, flowers in which the alz are still inclosed by the vexillum,

Cross-fertilisation is insured, since the stigma is always mature

in flowers capable of exploding, and since the bee’s back is always
touched by the stigma an instant before the fresh pollen is applied
- to it. And even the flower to which the bee pays its first
_ visit, and whose stigma is not pollinated in the first instance, has
a fair chance of being fertilised subsequently, as the style curls
round so far as to bring the stigma again uppermost. A second
visitor can therefore easily apply pollen to it from the same or from
another flower, and the flower is certain to be again visited. I
have only occasionally seen hive-bees and humble-bees visit
exploded flowers, but the pollen that they leave is gleaned by the
"smaller bees, flies, and beetles, which are not strong enough to

force open the young flowers. I have found females of Andrena
_fulvicrus, K., Halictus zonulus, Sm., and Osmia fusca, Chr., busily
collecting pollen on exploded flowers; Rhingia rostrata and the
beetles Meligethes and Anthobium are often to be seen feeding on
these remnants of pollen. There is no doubt that many flowers
of Sarothamnus, which have been exploded by bees not yet dusted
_ with pollen, are fertilised by such supplementary visitors. The
shorter stamens which apply their pollen to the under sides of bees
or of Rhingia, and the position of the stigma after explosion when

it also is liable to come in contact with the under surfaces of
insects, stand in close relation with this supplementary process of
fertilisation.
In the Broom as in Laburnum, the vexillum is marked in its
| lower part by dark lines coursing towards the base of the flower.
If the flower contained honey, these lines could only be explained
as pathfinders, but here the’ flowers have neither any free honey
/ nor a nectariferous swelling such as exists in and round the in-
sertion of the vexillum in Laburnum. In this case the dark lines
_ may either be a useless inheritance from ancestors whose flowers

198 THE FERTILISATION OF FLOWERS. [PART III.

contained honey, or else they may be of use to the plant by leading
bees which visit it for the first time to expect honey and accord-
ingly to perform the actions necessary for exploding the flower.
When the explosion occurs, the bee finds its hopes of honey gone,
but its labour is repaid by such an abundant store of pollen that
it proceeds to visit other flowers merely to collect pollen.

Visitors: A. Hymenoptera—Apide : (1) Apis mellifica, L. $! very ab. ;
(2) Bombus lapidarius, L. 2 ! (3) B. terrestris, L. 9 ! both ab. ; (4) B. agrorum,
F, 9! (5) B. hortorum, L. ¢! (6) Andrena fulvicrus, K. 9; (7) Halictus
zonulus, Sm. 9; (8) Osmia fusca, Christ. 9, all c.p. (those marked (!) forced
the flowers open). B. Diptera—Syrphide: (9) Rhingia rostrata, L., fp., ab.
C. Coleoptera—(a) Staphylinide : (10) Anthobium, f.p. ; (0) Nitidulide : (11)
Meligethes, f.p.

Ulex ewropeus, L., has eine flowers, which, according to
Dr. Ogle’s description, agree Sa with those of Genzsta
tinctoria (633).

Amorpha fruticosa, L., and A. canescens, .N utt.—The carina and
alze are abortive ; the stanions and style are exserted. The small
flowers, devoid or a platform for insects, are arranged in a spike, on
which bees can easily creep from flower to flower. The flowers are
proterogynous, with persistent stigmas. They are cross-fertilised,
according to Beal, by bees and wasps, which work upwards
beginning at the bottom of the spike (41, 178, 590, I1.).

_ Indigofera—According to Hildebrand’s figures and descrip-
tion (346), the flowers are so far explosive that the carina and
alze flap downwards, while the reproductive organs remain erect ;
self-fertilisation takes place as the flower withers. Henslow (323)
described the flowers of J. speciosa with reference to Hildebrand’s
description, and maintained justly that their structure was only
intelligible on the supposition that it led to cross-fertilisation.

I, macrostachya, Vent., was seen by Delpino to be visited by
Bombus Italicus (178).

113. CorontILLA Emerus, L.—Delpino has thoroughly described
in the case of this flower the piston-apparatus which we have
studied in Lotus corniculatus. As visitors he observed Bombus,
Anthophora pilipes, Eucera longicornis, and Xylocopa violacea.

114, CORONILLA VARIA, L., resembles Lotus corniculatus in
regard to its piston-apparatus, but the flower contains no honey;
it is nevertheless diadelphous (178, p. 45). In Thuringia I have
seen it visited abundantly by hive-bees.

Mr. T. H. Farrer discovered that honey occurs on the fleshy

OEE ts ll la ly Sag gaa

PART III. | THE MECHANISMS OF FLOWERS. 199

outer surface of the calyx. He found that bees obtained this
honey in the following manner: they alighted on the flowers in
the usual way, and inserted their tongues as usual beneath the
vexillum; then, however, the proboscis came through the wide
interspace which is left between the unusually narrow claws of the
petals, and so reached the outer side of the calyx. The same holds
— good of Coronilla montana, Scop, C. glauca, L., and C. minima, L.
(244). 3

Fia. 66.-- Hippocrepis comosa, L.

_A.—Flower, from the side (x 4).

B.—Ditto, from the front.

C.—Ditto, after removal of the vexillum and the upper part of the calyx, from above (x 7).

C'.—Part of the claw of the vexillum, from below.

C2.—Ditto, from the side ; vp, process which closes the entrance to the honey.

D.—The same flower (C), after removal of the ale also.

E.—JInner view of right ala.

¥.—Carina, from the side. -

G.—Ditto, in section, more magnified. ;

‘a, anthers; ca, calyx; e, pouched depression in the ala, fitting into the corresponding depres-
sion e’ in the carina; ex, terminal orifice of carina; f, vexillum ; f’, its claw; fa, fold of ala which
_ fits into the corresponding fold fa’ of the carina; fi, filament; fl, ala; fl’, claw of ala; o, superior
_ free stamen ; ov, ovary ; po, pollen; s, carina; st, stigma; v, coherent filaments,

| 115. Hippocrepis comosa, L.—This flower resembles that of
Lotus in the way in which the pollen is pumped out (178, 360),
_ but it is characterised by the peculiar way in which the honey is
_ concealed.

. The claw of the vexillum is so narrow and so much curved (A)
_ that one can see between it and the stamens. On the under side

200 THE FERTILISATION OF FLOWERS. [PART IIT.

of its base it bears a flattened triangular process (vp. C! C?) which
fits exactly over the nectaries (1) and closes them with considerable
firmness. <A bee visiting the flower can only obtain the honey by
using the vexillum as a long lever to raise up this lid; and to do
this it must insert its head beneath the vexillum, and consequently
effect cross-fertilisation. .

On the Alps I observed various bees cross-fertilising the plant,
and also numerous Lepidoptera which visited the flowers but only
effected cross-fertilisation occasionally (609).

Fic. 67.—Onobrychis sativa, Lam,

1.—Flower, from below (x 8),

2.—Ditto, after removal of the vexillum and the upper half of the calyx, from above.

3.—Essential organs, from the side (x 7).

a, calyx; b, carina; c, ala; d, vexillum, pale red with darker lines (pathjinders) ; e, claw of ala ;
f. coherent filaments ; g, free stamen; h, entrance to honey; i, cleft of carina, through which the
anthers and stigma emerge.

116. ONOBRYCHIS SATIVA, Lam.—The flower has the same
simple structure as we have studied in the case of Melilotus and
Trifolium : when the carina is depressed, the stigma and the anthers
(which dehisced in the bud) emerge, and when the pressure is
removed the carina springs up and again incloses these organs.
The arrangement in this case is still simpler than in the two
above-named genera, since the carina performs by itself the fune-
tions which the alee formerly shared with it; for the ale are very
much reduced, only covering the claw of the carina, and serving
to prevent or to render difficult the removal of honey at either

PART IIT. | THE MECHANISMS OF FLOWERS. 201 |

side. The carina alone forms the platform for insects to alight ve
i and the lever by which its own downward rotation is effected:
H own elasticity brings it back to its former position on removal ie
the pressure.
Cross-fertilisation is insured, in case of insect-visits, by the
prominence of the stigma, which must touch the under surface
of an alighting insect in advance of the anthers. In absence of
insects, self-fertilisation cannot occur, especially as the style con-
tinually grows, so that in older flowers it protrudes for a distance
of 1 to 14 mm. beyond the carina. The brightly coloured flowers,
‘massed in racemes, attract numerous insects. The calyx-tube is
only 2 to 3 mm. long; the broad vexillum ascends at a very small
angle from the horizontal, and is the better fitted to serve as a
fulerum against which the bee may place its head while thrusting
down the carina with its legs. Both honey and pollen are thus
rendered accessible to short-lipped bees. In sunny weather the
flowers are the resort of so many insects that they can well
afford to dispense with the power of self-fertilisation.

~ Visitors: A. Hymenoptera—Apide: (1) Apis mellifica, L. 9 (6), s. and

©.p. ; so abundant as to make nine-tenths of all the visitors ; (2) Bombus senilis,
| Sm. 2 (14—15) ; (8) B. silvarum, L. 9 (12—14) ; (4) B. agrorum, F. 9 (12—
15) ; (5).B. confusus, Schenck, 2 (12—14) ; (6) B. terrestris, L. 2 (7—9) ; (7)
_ B. muscorum, F. 9 § (10—14) ; (8) B. pratorum, L. 9 § (8—11}); (9) B
Scrimshiranus, K. §:—all sometimes suck honey, sometimes collect pollen ;
~ (10) B. (Apathus) rupestris, F. 9 (12—14), s.; (11) B. campestris, Pz. @
~ (10—12), s. ; (12) Eucera longicornis, L. ¢ 9 (10—12), s. and cp. ; (13) An-

drena labialis, K. 9 ¢, s. and e.p.; (14) A. nigroswnea, K. ¢ (3); (15)
_ Halictus albipes, F. 2 (3), s. and cp. ; (16) H. flavipes, F. 2, s. and c.p. ; (17)
H. lugubris, K. 9; (18) Megachile circumcincta, K. 9, s. and e.p.; (19)
Osmia aurulenta, Pz. 9 (8—9), s. and ce (Thur.) ; (20) O. spinulosa, K. 9
(Thur.) ; (21) Chalicodoma muraria, F. 2 (10), s. and ep. (Thur.) ; (22)
Ceelioxys conoidea, Ill. 9,8. B. Diptera—Syrphide : (23) Volucella plumata ;
mi—8). ©. Lepidoptera—i(a) Rhopalocera: (24) Pieris napi, L., s.; (25)
yeeena sp. ; (b) Sphinges : (26) Zygeena carniolica, Scop. (Thur.) ; (¢) Noctue :
_ (27) Euclidia glyphica, L.; (28) Plusia gamma,:L., ab.,—all sucking, but
apparently not effecting fertilisation. See also No. 590, 1

:
=
re

Stylosanthes, Swartz, Arachis, L., Heterocarpea, Phil., Lesperdeza,
Rich., and Chapmannia, Torr. nid’ Gr., have cleistogamic Howers
} -ac Biding to Kuhn.

_ £rrum lens, L., is visited by the honey-bee and by Lepidoptera
(590, 11.).

Vicia hirsuta; Koch, is remarkable for the great simplification
of the whole mechanism of the flower, in relation to its great
_ reduction in size (590, II).

202 THE FERTILISATION OF FLOWERS. [PART III.

117. Victa Cracca, L.—The Vetches afford an instance of how
much caution is needed before drawing conclusions for a whole
genus from a single species. Delpino describes a brush of hairs
upon the style as a character of the genus Vicia, without mention-
ing what species he observed it in (178); but his description
applies only vaguely to V. sepium, and not at all to V. Cracca, In
other peculiarities of structure the Vetches which I have examined
show remarkable diversity. |

In V. Cracca the style is very short (about 13 mm. long), and
for some distance below the stigma it is covered with long, slanting -
hairs (5, Fig. 68). Though the hairs are longer and closer on the
outer side than on the inner, they form a cylindrical brush rather

Fic. 68.—Vicia Cracea, L.

1.—Flower, from the side (x 3).

2.—Ditto, after removal of calyx and vexillum, from above, a little more magnified.

8.—Ditto, after removal of the ale also.

4.—Inner view of left ala.

5.—Style, highly magnified. .

a, b, anterior and posterior infoldings of the superior border of the ala; a’, b’,.corresponding de- —
pressions in the carina; ¢, process, a lobe of the superior border of the ala, directed backwards —
and inwards; d, claw of ala; e, claw of carina; jf, swollen point of the carina, containing. the
pollen ; g, superior basal lobes of carina; h, honey; p, brush; 0, orifice for exit of style; st, stigma.

than a basket (cestella) as Delpino describes them. The anthers,
which lie close round the brush of hairs, dehisce and shed their
pollen upon the hairs when the flower has scarcely attained half
its full size; and the stigma, which is overtopped all round but
especially on the outer side by hairs, is also covered with pollen,
The brush of hairs, thus covered above and all round with pollen, lies
in a pouch of the flattened tip of the carina (f, 2, 3), and emerges
when the carina is depressed from the narrow slit at its tip. |

As in other Papilionaces, the carina is depressed by means of the
ale, which are firmly connected with it and which serve as long
levers on which the insect alights. |

Kach ala is connected at two points with the margin of the

parti.) | THE MECHANISMS OF FLOWERS. 203

carina. In the middle of its upper border, each ala has a small but
deep fold (a, 2, 4), which fits into a concavity in the upper surface
_ of the carina (a’, 3) immediately behind the swelling which contains
F the pollen. Close behind this the side of each ala bulges inwards,
_ forming a depression, much broader and not less deep, which unites
‘so firmly with a broad but shallow concavity in the upper surface of
the carina ()’, 3) that it requires the greatest care to separate the
two without tearing. This intimate union is due to the fact that
the epidermis of the two petals over part of the surfaces of contact
is composed of large hexagonal cells (,'; to ;4y mm. in diameter) of
which those on the one petal are strongly convex, and fit into cor-
responding concavities in the cells on the other. Thesame kind of
_ union thus connects individual cells as on a larger scale connects the
two petals.

The ale and carina return after each depression to their former
_ place. This is due: (1) to their own elasticity ; (2) to the processes
(¢, 2, 4) which pass backwards and inwards from the superior basal
angles of the ale to lie upon the staminal column ; (3) to the two
superior basal lobes of the carina (g, g, 2, 3), which embrace the
staminal column, and leave only a narrow slit between them in the
middle line; (4) to the broad base of the vexillum, which curves
round on each side so as to embrace completely the claws of the
ale and carina, while it in turn is embraced and held firmly in
position by the calyx. By these four conditions all the parts of the
flower are caused to return accurately to their former places after
each insect-visit. The flowers therefore preserve the same appear-
ance, and are visited repeatedly by insects, so that their pollen is
zarried away bit by bit, and the stigma at length rubbing on the
} ‘under side of the insect becomes -vincid (cf. Lathyrus pratensis)
and covered with pollen brought from other flowers.
Though the parts of the flower close up firmly, their small size
akes it easy for most bees to reach the honey. The abundance of
honey and the aggregation of the flowers in handsome racemes
lead to plentiful insect-visits.

| A. Hymenoptera—(a) Apide : (1) Apis mellifica, L. 8 , exceedingly abundant.
(It passes up the racemes, sucking for two to three seconds on each flower. When
| collecting pollen, it thrusts its head farther into the flower to depress the
' carina as much as possible ; it takes at least six to eight seconds to brush off
the pollen) ; (2) Bombus agrorum, F. 9 &; (8) B. Berne L. $; (4) B
R ajellus, Ill. §; (5) B. Scrimshiranus, K. ¢ 2 %; (6) B. (Apathus) vestalis,
Foure. ¢; (7) Eucera longicornis, L. ? ) al only sucking: Various species
vith abdominal collecting-brushes, viz.: (8) Megachile versicolor, Sm. 9; (9) |
y circumeincta, K. 9, ab. ; (10) M. aiimaet. K .%;(11) M. Willughbiella,

204 THE FERTILISATION OF FLOWERS. [PART IIT,

K. 92; (12) Diphysis serratule, Pz. 9; (13) Osmia adunca, Latr. 9, both s.
and ¢.p. ; also the males of 9, 12, 13, sucking ; (b) Vespidew: (14) Odynerus
simplex, F. 9. B. Diptera—Hmpide : (15) Empis livida, L., ab., s. (It stands
upon a neighbouring flower, and inserts its tongue beneath the vexillum without —
effecting fertilisation). C. Lepidoptera—(16) Pieris rape, L., s., without
effecting fertilisation. See also No. 590, 11., and No. 609.

118. Victa sEPruM, L.—The style is 23 mm. long; close beneath
the oval stigma it bears on the outer and inner sides two brushes,
quite separate from each other, each about 1 mm.long. The brush

Fic. 69.— Vicia sepium, L.

1.—Flower, from the front.

2.—Ditto, from above, after removal of the calyx and yexillum.
3.—Ditto, after removal of the alz also.

4.—Ditto, from the side,

5.—Style, with brush and stigma, from the side,

6.—Brush and stigma, from above.

7.—Essential organs of a bud, -

(Letters as in Fig. 68.)

on the inner side, which must go in advance when the style emerges
from the carina, is formed of a single row of stiff hairs, slanting
upwards in the middle line. The brush on the outside consists of
a single row of hairs at its lower end only, and farther upwards it
broadens out until immediately below the stigma it more than half
surrounds the style; its hairs, which in the lower part are stiff and
slanting upwards, diverge more and more, until close beneath the —
stigma the truncated end of the brush forms a shallow saucer-
shaped hollow (p, 5,6). In the bud the two brushes lie, surrounded
by all the anthers (p, 7), im an expanded part of the apex of the
carina (f, 3, 4). The anthers dehisce when the petals are nearly

vant ut| THE MECHANISMS OF FLOWERS. 205

full-grown, and surround the brushes with pollen; they themselves
are withdrawn from the expanded part of the carina by contraction
Bot the filaments. As soon as this has taken place, the blade of the
vexillum, which is adorned with dark lines, becomes erect, and its
sides bend backwards ; the ale arch outwards, forming a convenient
platform for bees, and the flower, which had begun to secrete honey
abundantly in the later stages of the bud, is now in every respect
ready for its visitors.
Though the mechanism of the flower resembles that of V.
Cracca except in regard to the brushes on the style, its larger size
and some apparently slight differences in structure, cause a great
_ difference in the number of visitors, and exclude flies and Lepid-
_ optera, which in V. Cracea suck the honey without benefiting
_ the flower.
- The following conditions produce this result :—
(1) The flowers are not only considerably larger, but the petals
_ are notably thicker and stronger, so that much more force is needed
to push apart the vexillum and alz than in V. Craceca.
(2) The calyx-tube surrounds the claws of the petals for a
greater distance,
| (3) In V. Cracca as well as in V. sepiwm the entrance between
yexillum and alz is firmly closed by two grooves on the upper
surface of the vexillum where the claw joins the blade, which
project on the lower surface as two ridges fitting tightly to the ale.
n V. Cracca these are thin-walled, and even an Hmpis can insert
its proboscis beneath the vexillum; but in V. sepium they are much
thickened. ; ‘
(4) The ale in V. sepium form a relatively much shorter lever
for depressing the carina than in V. Cracca.
_ Owing to all these circumstances, it is only the most powerful
bees, viz., Bombus and Anthophora, which can possess themselves of
the honey in a legitimate way.
_ Thisis an advantage, in so far as it completely excludes flies and
Lepidoptera, which in V. Cracca often steal the honey without being
of any use to the plant ; but it brings with it a disadvantage which
probably quite neutralises the advantage. For Bombus terrestris,
finding it difficult to reach the honey legitimately, regularly bites a
hole in the side of the flower through calyx and corolla, and so
inserts its proboscis. In many cases it is hard to find a flower
| which has not been robbed in this manner, and often even unopened
| buds are robbed. The difficulty of depressing the carina so far as
} is needful in collecting pollen, prevents those bees which suck

;

Re = a een a ee ae ee et te i A arom gaia ae A eee sme RE
i

206 THE FERTILISATION OF FLOWERS. [PART ILI.

honey legitimately on V. sepiwm from collecting pollen also on its
flowers, and thus diminishes the number of their visits.

The stigma of V. sepiwm resembles that of Lathyrus pratensis
in the way in which, when it is rubbed on a piece of glass, first its
own pollen is rubbed off, and then its papillz are injured and exude
a sticky fluid.

The visitors are all bees, viz. :—(1) Bombus agrorum, F. 9 § ; (2) B. Rajellus,
Ill. 2; (8) B. lapidarius, L. 9 $; (4) B. silvarum, L. 9; (5) Anthophora
pilipes, F. 9 ¢,—-all sucking normally ; (6) Bombus terrestris, L. ?, biting a
hole and stealing the honey ; (7) Osmia rufa, L. 9 ; (8) Apis mellifica,. L..% ,—
both make use of the holes made by B. terrestris. Both species have tongues
long enough (Osmia rufa 8 mm., Apis 6 mm.), but are not strong enough to
reach the honey in the legitimate way. See also No. 590, IL.

Vicia angustifolia, Roth.—The brushes on the style are similar
to those in V. sepium. The visitors are humble-bees, Saropoda,
and Lepidoptera (590, II.).

119. Victa Faba, L.—The brushes on the style are similar to
those of V. sepium. In spite of the much greater size of the flower,
both its honey and pollen are more accessible than those of V. sepiwm,
though to reach the honey a longer proboscis is needed. The vexil-
lum and alee fit much less firmly together, and the carina is much
more easily depressed. The thickened processes which in V. sepiwm
project from the under side of the vexillum are here wanting; the claw
of the vexillum (13 to 16 mm. long) is only loosely embraced by the —
calyx-tube, and for a distance of only 6 to 7 mm. above, and 8 to 10
mm. below. The vexillum is therefore easily pushed upwards, and
those humble-bees which have a proboscis long enough to reach
the honey in V. Faba, can do so more easily in that flower than in
V. septum. The two depressions by which the ale and carina are
united in V. Cracca and V. sepium occur also in the Bean, but in the
latter the interlocking of the individual cells is less marked than in
the others, so that the alee and carina may be easily separated with-
out tearing. The two posterior processes of the alee, whose use is to
keep the al and carina in their proper place in relation to the
staminal column, are here much reduced and easily slip down from
the upper surface of the carina. The ale and carina are easily —
depressed, all the more that the ale project far beyond the carina,
forming a powerful lever acted on by the weight of the bee. Thus
to reach the honey is here a matter of little difficulty, and is
possible even for the smaller bees. |

PART 111. | THE MECHANISMS OF FLOWERS. 207

Owing to the small elasticity of the ale and carina in the bean-
| flower, they fail to return to their former place if they are
thrust far down, but leave the end of the style with its stigma and
i brushes and even the empty anthers exposed.

Visitors: A. Hymenoptera—Apide: (1) Bombus hortorum, L. Q (21) ;
(2) B. senilis, Sm. 9 (14—15) ; (3) B. confusus, Schenck, ? (14) ; (4) B. lapi-
darius, L. 2 (12—14) ; (5) B. silvarum, L. 2? (14),—all sucking in the normal
way, ab.; (6) B. terrestris, L. 9 (7—9), sucking honey through holes bitten
the tube ; (7) Apis mellifica, L. 9 (6), sometimes c.p., sometimes sucking
through the holes bitten by B. terrestris ; in the former case it effects cross-
fertilisation as well as those bees which suck in the normal manner ; (8) An-
drena convexiuscula, K. 9, c.p. ; (9) A. labialis, K. ¢, seeking in vain for honey ;
(10) Osmia rufa, L. 9, sucking normally,—it creeps so far into the flower that
its whole head is hidden under the basal part of the vexillum. B. Coleoptera
_ --Malacodermata: (11) Malachius bipustulatus, F., feeds upon the stamens
after they have been laid bare by repeated visits of humble-bees.

Darwin found the fertility of the bean reduced to a third when
insects were excluded by a net; but if the flowers were shaken
| they produced good and well-filled pods though still protected from
insects (152).

Vicia amphicarpa, Dorthes., has, besides its ordinary flowers, cleis-
_ togamic flowers without petals on subterranean shoots (399, 531).

120. LATHYRUS PRATENSIS, L.—This plant affords us another
example of a papilionaceous flower, in which when the carina is
depressed the tip of the style only emerges, and sweeps part of the
pollen out of the apex of the carina by means of a brush, applying
it to the under side of the bee, afterwards returning within the
carina when the pressure is removed.

The style, which ascends vertically from the end of the
horizontal ovary, curving slightly inwards, expands immediately
below the oval stigma into an elliptic lamina. This lamina is
x Bickod, not only on the edges, as Delpino says (178), but on the
whole surface turned towards the base of the flower, with hairs
| pointing obliquely upwards; it lies in the conical apex of the carina,
which points directly upwards (5, Fig. 70), and its hairy surface,
_ turned towards the base of the flower, faces also the free edges of
if me tip of the carina. Between it and the margins of the carina is
a deep pouch on each side (p, 5, 6), which is separated by a deep
fold (a’) from the margin, and has its only entrance at the apex of
the cone (m, 4, 5, 6). In the bud, this pouch contains all the
_ anthers, which only dehisce immediately before or during the

. coeemancas es ere

208 THE FERTILISATION OF FLOWERS. [PART III.

expansion of the flower. The pouch becomes quite filled with
pollen, and the anthers withdraw into its lower part. The hairy
surface of the style and the stigma are thus covered with pollen in
the opening flower, and each time that the carina is depressed they
emerge at its apex sweeping a little pollen out. Since the hairs of
the style do not pass into the lateral pouches, these would remain
full of pollen, were it not that when the carina is depressed, the

Fig. 70.— Lathyrus pratensis, L.

1.—Flower, slightly enlarged, from the side.

2.—Ditto, from above, after removal of the calyx and vexillum (x 38).

3.—Inner view of left ala.

4.—Flower, from above, after removal of vexillum and al.

5.—Bud about to expand ; the calyx, vexillum, and ale have been removed.

6.—Fore-part of ditto, from above.

7.—Style, from above.

8.—Ditto, from within. :
a, slight concavity in the ala, which fits into the much deeper depression (a’) in the carina;

b, infolded process of the margin of the ala, pointing forwards and downwards, and fitting into the —
narrowest part of the depression in the carina; ec; transverse depression in the ala, into which the _

ridge (0) of the vexillum fits; d, posterior alar process ; e, claw of ala; f, incurved margin of ala;
99, edges of the carina ; h, superior stamen ; i, the coherent filaments ; k k, the entrances to the honey :
l, claw of carina; m, point where the stigma emerges. when the carina is depressed; n, foliaceous
expansion developed at the line of junction of the two carinal petals; o, ridge on the inferior sur-
face of the vexillum, corresponding to a groove on its superior surface; p, bulge in the carina,
beneath which are the anthers and style,—it is separated by a deep fold from the upper margin of
the carina on each side.

empty anthers and the ends of the filaments pass into and push the

pollen out of the pouches into the apex of the cone, whence it is —

swept out by the style. It requires considerable force to depress
the carina, since the style with its hairs has at the same time to be
forced through the slit at the apex of the carina.

It stands in close relation to this arrangement that the union —

of the two halves of the carina is strengthened by an anterior

Fo fie Te PK, cee 1"

parrut] THE MECHANISMS OF FLOWERS. 209

- membranous outgrowth (n, 4), and that the ale and carina are
connected very firmly with one another and with the staminal
- column. The union between the ale and carina is formed in the

following way:—The two folds or grooves, which in the erect
extremity of the carina separate the two pouches from the free
margins, are continued along the whole horizontal part of the carina

‘near its upper border, and where the erect part joins the horizontal
(at a’, 4, 5, 6) they each form a broad, rounded pit in which a fold
of the ala (a, 1, 2, 3) lies; further towards the base of the flower
_ they form a deep, narrow depression on each side of the cleft of the
carina (0’, 4), in which a process directed downwards and forwards

from the upper margin of the ala (0’, 2, 3) fits firmly. This inter-
locking is rendered more secure by the presence of numerous blunt

projections on the marginal process of the ala (b), and in the full-
- grown flower it is difficult to separate the ala from the carina
without tearing.
_ The union of the alse and carina with the staminal column is
effected, as in Medicago sativa, by two long, pouched processes of the
ale (directed backwards) which lie upon the column (d, 2, 3), meet-
Ing one another in the middle line. When the al and carina are
_ depressed, these processes clasp the sides of the column, and as
soon as the pressure is removed they return to their former place
on its upper surface. The vexillum closes down firmly on the
_ alg, preventing useless insects, eg. flies, from obtaining the honey
; which is secreted abundantly in the ordinary position and is
reached by two unusually large openings. The vexillum, at the
junction of its claw and lamina, bears two deep, narrow depres-
sions which project below as two sharp ridges converging
anteriorly (0, 1), and these fit firmly into two depressions in the
alze (c, 2, 3). Though the stigma is at first surrounded by the
pollen of its own flower, it is probable that in case of insect-
Visits, cross-fertilisation is ensured. For this pollen with which
the stigma is covered, is easily rubbed off if we draw the
Stigma over a glass plate; but immediately afterwards the stig-
matic papille get rubbed away and leave a line of clear sticky
fluid on the glass. Owing to the force which the mechanism
of the flower renders necessary, the stigma must be rubbed hard
on the under side of the bee, and thus without doubt, as Delpino
| supposes, its own pollen is rubbed off, its surface is rendered
sticky by breaking down of the oS and new pollen is made

_ to adhere to it.

Whether in absence ‘of insects. the stigma finally becomes
P

Se

210 THE FERTILISATION OF FLOWERS. [PART IL. |

viscid and capable of fecundation spontaneously, and is thus self-
fertilised, is still undetermined.
The visitors are exclusively bees.

(1) Eucera longicornis, L. ¢,s., ab. ; (2) Bombus agrorum, F. 2, s., freq. ;
(3) Diphysis serratulae, Pz. 9,8; (4) Megachile maritima, K. ¢,s.; (5) M
versicolor, Sm. 9, s. ande.p. (Brilon, 10 July, 1869.)

121. LatHyrus TUBEROSUS, L.—I saw this plant visited very
abundantly by the honey-bee in July 1868,in Thuringia. In suck-
ing, the bee inserted its proboscis at one side, above one of the ale.
As it clung to one of the ale and thrust its proboscis in laterally
between the vexillum and carina, it pressed the carina so far down
that the style and pollen emerged. In some cases the pollen did
not come in contact with the bee, in others the stigma and the
hairs of the style touched the bee on its side.

When collecting pollen, the bee clung to both ale, thrusting its —
head and forelegs beneath the vexillum in the middle line. The ©
stigma emerging from the carina came directly in contact with the
under side of the bee, and cross-fertilisation was effected regularly.
Besides the honey-bee I only saw two butterflies, a yellow Hesperia,
and Pieris rape, L., sucking honey on the flowers.

122. LATHYRUS SILVESTRIS, L.—I saw this plant in Sauerland
(July 12, 1869) visited also by hive-bees, both sucking and —
collecting pollen, and by numerous Lepidoptera, which however
did not effect fertilisation (Rhodocera rhamni, L., Pieris rape, L.,
Vanessa To, L., V. urtice, L., Plusia gamma, L.).

Delpino <onnhiors as the chief fertiliser of this plant xX ylocopa
violacea, which does not occur in Westphalia, and justly emphasizes
the slanting position of the style-brush as an adaptation rendering
it easier for the bees to depress the carina (178).

Francis Darwin observed that bees rob Z. silvestris of its honey
by biting through the vexillum close above the calyx, and almost
always just above the left honey-passage, which is commonly the
larger,—a proof of capability to profit by experience. The un-
symmetrical development of the passages leading to the honey in
L, silvestris is in relation to the twisting of the style, and thus
unsymmetrical development of the fruit seems related to both of
these facts (169).

123. LATHYRUS MONTANUS, Bernh. (Orobus tuberosus, L.).—In
Sauerland (July 1869) I saw this plant visited by Zucera longicornis,

uu] | THE MECHANISMS OF FLOWERS. 211

» %, s. and ep; Bombus pratorum, L. %,s.; and Hesperia
ilvanus, Esp. s.

_ 124, Larnyrus oporatus, L., is visited by Anthidium mani-
vatwm, L. 2, s. |

125. LATHYRUS VERNUS, Bernh. (Orobus vernus, L.).—I have
epeatedly found Bombus hortorum, L.:?, sucking honey on this
ower. A list of eleven other visitors, exclusively bees, is given in
Yo, 590, IL., p. 257.

iathyrus grandiflorus is very rarely visited by bees in England.
f the flowers are shaken they prove more fertile (152).

_ Delpino mentions the genera Apis, Bombus, Eucera, Anthophora,
4 Xylocopa, as the chief fertilisers of the various species of
Lathyrus (178).

126. Pisum sativum, L. (the Pea)—The mechanism of this
flower agrees in most essential points with that of Lathyrus
| pratensis, but it has so many peculiarities that we must discuss it
n almost complete detail.
7 _ style ascends almost perpendicularly to the horizontal
| , but its tip curves inwards so far that the stigma points”
alm Bet horizontally towards the base of the flower (s¢. 7). The style
‘3s not swollen at the end, but is covered with long hairs on the side
wing the base of the flower for over one-third of its length down-
ards from the stigma (7, 8, fig. 71). The style follows the line
of union of the two halves of the carina, so the carina also is
_ curved inwards in the shape of a sickle, and its conical tip, which
‘incloses the brush upon the style, points towards the base of the
' flower (1, fig. 71). In this species also, as in L. pratensis, there is
| present in the bud on each side of the tip of the carina (a, 1, 4) a
puch, within which are the anthers ; but the pouches are shallower
and the folds separating them from the free margin are less
arked, and the space in which the anthers lie in the bud is on
the whole conical. The apex of the carina leaves, of course, an
: ! ‘opening for the passage of the style (0, 4, 5). The anthers dehisce
shortly before the bud expands; they fill the conical point of the
wina with pollen and withdraw into the base of the cone, so
nat at the commencement of the flowering-period the stigma and
1e style-brush are covered with pollen, part of which is swept
it at the apical orifice each time that the carina is depressed.
The edges of the orifice yield to a pressure from within, but close
P 2

212° THE FERTILISATION OF FLOWERS. [parr it.

up again, so that while the stigma and style-brush return |
within the carina, great part of the pollen is swept off and remains —

outside, The ends of the filaments, lying in the base of the

conical point of the carina, are slightly swollen even in the bud

(7, fig. 71), but after the anthers have dehisced they enlarge more
(9), and so press the pollen forward more effectively than in the —

case of Lathyrus pratensis. They press the pollen in the base of |

Fig. 71.—Pisum sativum, Li. >

1 —Flower, after removal of left ala. i
2.—Inner view of left ala. ;
3.—Antcrior view of vexillum.
4,—Carina, from above, enlarged.

5.—Ditto, inclosed by the ale.

6.—Basal half of left ala; outer view.

7.— Essential organs from a bud (x 383).

8.— Anterior part of style, from within (x 7).
9.—One stamen of the flower.

(For letters, see the text.)

the cone forward to its apex, so that the style-brush on returni
within the carina becomes covered again with pollen, and so :
new portion of pollen is forced out at each depression of
carina. Thus the flower of the Pea combines the brush-mechanis
with the piston-mechanism.

The force needed to depress the carina is both absolutely
relatively greater than in Lathyrus pratensis, since the style-b

PART III. | THE MECHANISMS OF FLOWERS. 213

is curved more inwards, and the swollen ends of the filaments move

with friction in the cone. On this account the union of the

two carinal petals is strengthened by a still more marked out-

growth (b, 1, 4), and the ale and carina are connected with each

other and with the staminal column still moré firmly. Each ala
has at the base of its limb, close below its upper margin, a
‘depression or invagination pointing forwards and downwards
(¢, 2, 5, 6), which is very firmly attached to a corresponding
depression on the upper surface of the carinal petal (¢, 1, 4);
not only are the two pouches closely applied to one another
_ throughout their whole extent, but over a great part of the surfaces
in contact large hexagonal cells of the one petal project into hollows
_ in corresponding cells on the other, so that it is scarcely possible
to separate the petals from one another without tearing. More-
_ over, the anterior part of the ala is kept in a definite position
relatively to the carina by a fold or groove (d’, 2,5) in its upper
margin which fits into that groove (d) upon the carina which
- separates the pouch (a) from the edge. This second union of alz
and carina is strengthened by two deep and narrow depressions of
the vexillum, which appear on its under side as hard, sharp ridges,
converging anteriorly (d’, 1, 3), and are received into the anterior
alar grooves (d’).

The position of the alz and carina relatively to the staminal
column is maintained very firmly and accurately. Each carinal
} pe etal possesses a lobe at its base (e, 4, 5), directed upwards and
pawards, which lies upon the upper surface of the column and
extends almost to the middle line. These two carinal lobes which
Biibtace the column are pressed down and kept in their place by
two processes of the ale (e¢’, 5, 6), directed inwards and backwards ;

the alar processes are themselves made secure by the Neate:
_ on whose broad, strong base two rounded swellings occur (0’, 3)
which rest upon two narrow surfaces of the ale (0d, 5, 6) passing
horizontally backwards from the alar processes (e’).

_ This firm union of the parts of the flower is of service to the
plant in three ways. In the first place, it obliges an insect in
| search of honey, when standing on the alee and thrusting its head
_ beneath the vexillum, to use so much force in separating the ale
and vexillum that the brush and piston mechanism is set in action.
Se ondly, it ensures the perfect return of all the parts to their
| original position when the pressure is removed, and sa_causes the
IP flower to retain its youthful appearance and to receive the repeated
visits that its whole construction is designed for. Thirdly, it

214 THE FERTILISATION OF FLOWERS. (PART 111.

excludes all insects from the honey which are not strong enough
to perform the actions necessary for fertilisation.

Along with these obvious advantages, the firm closure of the
flowers has the very important consequence that it makes the
work difficult even for such bees as are able to reach the honey and
to effect cross-fertilisation, and deters them from the plant when
other more convenient flowers are at hand. In its original home
the Pea no doubt adapted itself to some strong and at the same
time diligent and skilful species of bee, which could easily depress
the carina, and was plentiful enough in ordinary weather to act as
the regular fertilising-agent. Under such conditions the advan-
tages of firm closure would outweigh the disadvantages. In our
climate, the Pea fails to find bees adapted for its flower, and it
would be much better for it under these altered conditions to have
its flowers less firmly shut. I have often watched beds of peas
in bloom in my garden in sunny weather and have only occasionally
seen a visitor, while beans, blooming at the same time in alternate
beds, were abundantly visited by humble-bees.

The only insects which I have seen on the flowers in the course of four
summers are: (1) Eucera longicornis, L. ; (2) Megachile pyrina, Lep ;—the ¢
of both species, s.; the 9, s. and c.p.; both freq., but not abundant ; (3) Two
specimens of Halictus sexnotatus, K. 9 ;—they collected pollen with difficulty,
holding the edges of the carina apart anteriorly with their legs.

Though most flowers remain unvisited by insects, they all pro-
duce good fruit. The self-fertilisation which the structure of the
flower necessitates must therefore be quite efficient; and this
indeed has been shown experimentally by Dr. Ogle, who found the
Pea as productive when insects were excluded as when left
unprotected (633).

Tribe Phaseolec.

Amphicarpea, according to Torrey and Asa Gray (NV. Amer.
Flora, t., p. 291), has fertile cleistogamic flowers, and also flowers
which open, but are for the most barren. Both kinds of flowers
are above ground. Darwin found that subterranean pods of
Amphicarpea monoica which he received from Meehan, contained
each a single seed, while the ordinary aérial pods, which he culti-
vated himself, contained from one to three small seeds; these latter
averaged only 7's of the weight of the subterranean seeds (167,
2nd Ed.).

The genera Neurocarpum, Desv., Martiusia, Schult., Glycine, L.,

‘parvu] © THE MECHANISMS OF FLOWERS. 215

Galactia, P. Br., and Voandzeia, Pet. Th., are stated by H. v. Mohl
and Kuhn to possess cleistogamic flowers.
| Glycine chinensis, Curt., is visited by bees only (590 IL).
—- Centrosema virginiana and Clitoria mariana both have their
flowers inverted (729).
In Erythrina crista-galli, according to Delpino, the flower i is
inverted, the ale are almost entirely aborted, and the carina forms
a sheath covering the column and expanded below into a large
| honey-receptacle. Since the stigma somewhat overtops the
_ anthers, the visitors, probably humming-birds, touch first the
_ stigma then the anthers, and so effect cross-fertilisation. In
| £. velutina the flower is not inverted; the ale and carina are
_ reduced to minute rudiments, and the column lies fully exposed
_ beneath the vexillum. The visitors, probably bees, must make their
| way between the column and the vexillum to reach the honey,
which is secreted as in other Papilionacee, and so they come in
contact with the stigma and anthers (178, 360). Belt (56) sawa
_ species of Erythrina fertilised by humming-birds, which came in
_ search of small insects that sucked honey in the flowers. Trelease
saw Lrylhrina herbacea visited abundantly by ruby-throated
humming-birds, and believes that the flower is adapted for cross-
fertilisation by their agency (731).

Darwin states on the authority of MacArthur’s observations
that, in New South Wales, Erythrina does not produce good fruit
unless the flowers are shaken (152).

_ PHASEOLUS.—The species of Phaseolus are distinguished from
_ the other Papilionaceze which have brush-hairs on the style by
_ the helicoid twisting of the style and of the tip of the carina
which incloses it; but here, as in the rest, when the carina is
__ pressed down, the tip of the style issues with its stigma and pollen-
_ brush, and these return within the carina when the pressure is
' removed. The twisting is towards the right in some species and
_ towards the left in others, according to Delpino, and shows all
stages from a mere sickle-shaped curvature (P. angulosus, etc.) to a
helix of four to five coils (P. Caracalla), (172, 178).

____ The mechanism of the flower and the mode of fertilisation in the
_ Scarlet Runner (P. coccineus, Lam.) have been thoroughly described
_ by Mr. T. H. Farrer (240). The hive-bee and other small bees
| which are unable to press the carina down, obtain the honey by
taking advantage of holes which a humble-bee (I suppose B.
|. terrestris, L.) bites through the calyx. More powerful bees, with

}

216 THE FERTILISATION OF FLOWERS. [PART IIT,

sufficiently long proboscides, alight on the left ala, and in forcing
the proboscis down into the flower bring its base in contact with
the stigma.

Now, when the ale and the carina (which is emer to them) .
are further depressed, there emerges from the tubular apex of the
carina, which is coiled nearly into two complete whorls, the
similarly coiled style; and it emerges in such a way that its
stigma points downwards and towards the left, and its pollen-
covered hairs come in contact with the base of the insect’s
proboscis, dusting it with fresh pollen. In this manner is cross-
fertilisation insured and self-fertilisation prevented in case’ of

Fia. 72.—Phaseolus vulgaris, L.

1.—Flower, viewed obliquely from above and in front.
2.—Pistil, enlarged.

a, calyx; 6, vexillum; ec, ale; d, apex of carina; e, ovary; f, style; g, its brush; h, stigma.

insect-visits; in absence of insects self-fertilisation cannot occur,
since the stigma protrudes from the carina while the pollen is
iclosed within it.

The similar mode of fertilisation in the Kidney Bean (Phaseolus
vulgaris, L.) was described ten years earlier by Darwin (51), who
showed by experiment that insect-visits are essential for the
fertilisation of this plant. Plants covered with a fine net remained
completely barren, unless the action of bees was artificially
imitated. When Darwin repeated the experiment on a larger
scale a few flowers on some specimens bore fruit; small insects
(Thrips) had presumably gained access to these."

' Dr. Ogle (No. 633) also gives a thorough description of the floral mechanism

in P. vulgaris (French bean) and P, coccinea (Scarlet Runner). Of the flowers which
Dr. Ogle protected from bees by means of a gauze net, no single one bore fruit.

parti.) | THE MECHANISMS OF FLOWERS. 217

Darwin had also shown that cross-fertilisation by insect-agency
¢ takes place to a large extent in Phaseolus. Mr. Coe planted four
rows of Negro Dwarf Kidney Beans between some rows of white
and brown Kidney Beans; near by were some Scarlet Runners.
He let the black Kidney Beans run to seed, and over # of the
beans produced showed all gradations from light brown to black,
and some were mottled with white. Of the plants reared from
these seeds every one differed from the rest in stature, leaves,
colour and size of flower, time of flowering and of ripening fruit,
size, form and colour of the pods ; and the beans produced by them
were of all shades between black and light-brown, some dark-
purple, some’ slightly mottled, and of various shapes and sizes
(151, 152).

In P. multiflorus the carina, with the inclosed style, are so bent
that when the carina is depressed the style emerges pointing
downwards and towards the left, so that a bee can only accomplish
cross-fertilisation if it enters the flower to the left of the coil.
_ Francis Darwin has pointed out that the tenth, free, stamen bears
an appendage which prevents the bee from taking any other way
towards the honey (169).

at eee es NUS
if a :

In regard to Treviranus’ opinion that self-fertilisation is the general rule in
Papilionacez, it is needless to discuss his arguments, since the only objection
which he made to Darwin’s experiments, viz. that the nets sheltered the plant
_ from movements of the air (742) was experimentally refuted by Darwin. For
the flowers in which Darwin imitated the action of the bees, though they grew
beneath the net, were completely fertile.

RETROSPECT OF PAPILIONACE.

The Papilionaceze which we have studied are all fertilised by
bees, and in spite of their manifold peculiarities of detail they all
agree in the following points regarding the arrangement and
function of the parts of the flower:
__ The flowers stand more or less horizontal; except Sarothamnus
they expose the stigma and pollen to contact only with the
| ventral surface of the bee, since the reproductive organs occupy the
inferior side of the flower and are only curved upwards at the
_ extremity. In the bud the reproductive organs are inclosed by the
_ two inferior petals, these by the two lateral, and these again by the
superior petal.
_ The two inferior petals cohere to form a “carina,” which

218 THE FERTILISATION OF FLOWERS. [PART IIT,

incloses the reproductive organs and protects them from rain and
from pollen-feeding insects. The two lateral petals (ale) have
a threefold function, serving (1) as a platform for bees to alight
on; (2) as a lever to depress the carina; (3) to keep the carina in
its place as regards the reproductive organs, and to bring it back to

—_—

its place after depression if repeated insect-visits are necessary for —

fertilisation. In order to serve as levers for depressing the carina,

the ale must be united firmly therewith. This is either accom- ~

plished by certain areas of the alar laminz bulging out and being
received in hollows of the carina, or by interdigitation of processes
on the contiguous surfaces of both; and such union is the firmer
the more frequently the carina has to be depresséd and again

brought back to its original position in order to ensure cross-

fertilisation.
The carina is mainly kept in its proper place and brought back
to it after depression by basal lobes of the alee which embrace

the column; sometimes they form swollen pouches (Trifolium), —

sometimes they are produced into long processes (Melilotus,
Medicago, ete. ).

The vexillum, with its large, erect, coloured surface, is the
chief agent in rendering the flower conspicuous; it also serves
as a fixed point or fulcrum against which a bee may place its head
while it pushes the carina with its feet resting upon the ale.

The stigma and pollen must be applied to the ventral surface
of the bee if cross-fertilisation is to result. The necessary

arrangement is attained by the filaments cohering to form a ~

cylinder round the pistil. In all Papilionacese which contain
honey, the honey is secreted on the inner sides of the bases of the
filaments, and it accumulates in the space between the stamens
and pistil. Since the reproductive organs have to come in contact
with the under side of the bee, it is clear that access to the honey

must only be permitted above the reproductive organs. We find, —

accordingly, that in all Papilionaceee which contain honey the
coherent filaments leave a passage superiorly. One stamen here
is separate from the rest and leaves two entrances to the honey
free on either side of its base, either by curving upwards at its
base, or by the neighbouring filaments curving outwards there,
or in both modes combined.

The arrangement and action of the various parts of the flower
in which all the Papilionaceze (except Onobrychis) agree, cause the
bees to act and move in a perfectly definite way, such as to ensure
the stigma and pollen coming in contact with their under surfaces.

_ PART IIL. | THE MECHANISMS OF FLOWERS. 219

Four different types of structure may be distinguished in
_ Papilionacew, according to the manner in which the pollen is
q applied to the bee. These distinctions were first drawn by
| Delpino (172, 178, 360), and transitions are not wanting from one
_ to another:

1. Papilionaceze in which the stamens and stigma emerge from
_ the carina and again return within it. They admit repeated visits.
(Melilotus, Trifolium, Onobrychis, Cytisus).

| __- 2. -Papilionaceze whose essential organs are confined under
_ tension and explode (Medicago, Genista, Surothamnus). In these
_ only one insect’s visit is effective, sometimes under certain
conditions two (Sarothannus).

3. Papilionaceze with a piston-mechanism, which squeezes the
pollen in small quantities out of the apex of the carina, and not
_ only permits but requires numerous insect-visits. (Lotus, Anthyllis,
— Ononis, Lupinus).

4, Papilionaceze with a brush of hairs upon the style which
"sweeps the pollen in small portions out of the apex of the carina.
y ' They for the most part require repeated insect-visits. (Lathyrus,

_ Pisum, Vicia, Phaseolus).
In all these groups, the stigma and the pollen are applied to
the under side of the bee. ‘The pollen can therefore as a rule be
_ collected quickest and most conveniently by bees with abdominal
\ _ brushes ; and so we find Lotus, Ononis, and Genista tinctoria visited
especially by these forms. In Sarothaimnus both the upper and
lower surfaces of the bee are dusted with pollen and come in
contact with the stigma.
In those Papilionaceze whose reproductive organs either simply
' emerge or spring out with an explosion, cross-fertilisation is ensured
_ bythe stigma projecting beyond the anthers, and coming first in con-
tact with the bee. In those forms in which the pollen is squeezed
' or swept out bit by bit, the stigma is at first coated with its own
_ pollen, which has probably no action upon the stigma and is
_ rubbed away by the first visitors; and the stigma only becomes
adhesive and so capable of fertilisation after its papillae have been
exposed to friction. In absence of insects, self-fertilisation seems
take place on a large scale in very few Papilionacesze (Piswm) ;
} ™ several it occurs to a small extent (Z'rifolium repens, Vicia

. and in many it never occurs (Phaseolus, Onobrychis,
) Sarothamnus). In cases where self-fertilisation is impossible in
the ordinary flowers, cleistogamic flowers which regularly fertilise
| themselves probably compensate.

220 THE FERTILISATION OF FLOWERS. [PART III.

Though almost exclusively adapted for fertilisation by bees,
many Papilionacez allow their honey to be ‘stolen by Lepidoptera
and long-tongued flies (e.g. Onobrychis, Lotus, Medicago falcata).
In others (e.g. Vicia sepium) the petals close up so firmly that only
those bees which are in the habit of burrowing with all their
strength, can force an entrance. Such forms as these exclude all
visitors which would rob the flower of its honey without giving
any return; but this advantage is more or less cancelled by the
great diminution in the number of serviceable visitors.

Trifolium pratense excludes short-lipped bees from its honey
by adhesion of the nine coherent filaments with the claws of the

petals to form a long tube; the same end is attained in Vicia faba :
by the length of the claws of the petals and of the calyx-tube. —

Both plants are the more visited on this account by the hard-
working humble-bees ; but on the other hand they are liable to be
often plundered by robber-bees which bite through the tube.

The great variety of arrangements in the various Papilionacez

seems to be partly due to the manner in which every advantageous ~

modification brings some disadvantage in its_.train ; for in this way

it is possible to have various combinations existing together, all —

perfectly adapted to the given conditions of life

CHSALPINIACEZ AND MIMOSACE.

In these two families the essential organs are freély exposed. —

The petals or the stamens, or both together, attract insects. In

Mimosacee the flowers are regular and united in capitula. In —

Acacia Julibrizzin the central flower of the capitulum is trans-

formed into a great nectary. In Amherstia nobilis the carina is—

abortive, and the alz assume the function of rendering the flower
conspicuous ; the honey-receptacle is hollowed out into a long tube,
which, together with the brilliant colour of the flowers, suggests
humming-birds as the fertilisers (178, 360).

Fritz Miiller found Cassia multijuga (Cosalpiniacee) abundantly :

visited by bees (Xylocopa, Centris) in South Brazil. The pedicles

were covered with larvae of Membracide, which secreted drops of —
honey at the posterior end of the abdomen, and this honey was

sought by 7'rigonia cacafogo (590, III.).

Cassia (?) is visited by humming-birds (J/imus) in Chili (Darwin,
No. 164).

pa 29 ren pages

ae

\

\

PART IIT. | THE MECHANISMS OF FLOWERS. 221

Orv. ROSACEA.

9

Tribe Prunee.

127. PruNUS comMuNIS, Hups., a, (P. spinosa, L.), Blackthorn,
Sloe.—When the flower opens the style stands some millimetres
above the stamens, whose anthers are still closed, and which are
bent down towards the centre of the flower. The stigma is already
mature, and projects even from the half-open flower; insects, in
_alighting, come first in contact with it. In due course the petals
spread out into a plane, and even further; the stamens become
erect and incline outwards; the anthers dehisce, beginning with the
outermost; the style also elongates, and overtops the shorter
stamens immediately around it: its stigma is still fresh, and insect-
visitors may therefore now lead to self-fertilisation. The flowers
turn towards the sun, and in default of insect-visits self-fertilisation
_ may take place by pollen falling on the stigma.
The numerous white flowers are very conspicuous on the black,
still leafless twigs ; their abundant honey attracts numerous insects,
particularly flies and Andrene, all the more that the plant flowers
early (April and beginning of May) in advance of most competitors.

ae

Visitors: A. Hymenoptera—(a) Apidae: (1) Halictus cylindricus, F. 9, s.
and ¢.p., ab. ; (2) H. albipes, F. 9, ditto ; (3) Andrena dorsata, K. 9, ep. ;
(4) A. parvula, K. ?,s.ande.p.; (5) A. fasciata, Wesm. ¢, s. ; (6) A. albicans,
‘K. 2 $, cp. and s.; (7) A. fulva, Schrank, 9,8. and c.p. ; (8) A.:fulvicrus, —
K. 2 g,s8.; (9) A. Gwynana, K. ?,s. and ep.; (10) A. rose, Pz. 9, s. and
¢@.p.; (11) A. Schrankella, Nyl. 9, cp. ; (12) A. atriceps, K. 9 ¢, 8.; (13)
~ Nomada succincta, Pz. ¢,s.; (14) Osmia rufa, L. ¢,s.; (15) Apis mellifica,
iL. §, s. and ep.; (b) Tenthredinide: (16) Dolerus gonager, Kl. 5. B.
Diptera—(a) she sa : (17) Empis rustica, Fall, s.; (6) Syrphide: (18)
‘Eristalis arbustorum, L. ; (19) E. nemorum, L. ; (20) E. intricarius, L., all
_ three s. and c.p.; (c) Muscide: (21) Scatophaga stercoraria, L.; (22) S.
| merdaria, F., both sucking; (23) Chlorops, s.; (24) Sepsis, s. ab. ; (25)
Species of thease: s.; (d) Bibionide: (26) Bibio Marci, L., lh. OC.
Coleoptera—Nitidulide : (27) Meligethes, Lh. D. Lepidoptera—Rhopalocera :
8) Vanessa To, L., s.

‘128. Prunus Papus, L., Bird Cherry—This species agrees on
__ the whole in its proterogynous arrangement with P. spinosa, but
ia the stamens remain throughout aired inwards, so that in the
_ second stage insect visits may lead to self-fertilisation more readily
_ than in the preceding species. In absence of insects, spontaneous
self-fertilisation takes place regularly—since the inner stamens

222 THE FERTILISATION OF FLOWERS. [PART III.

dehisce while still bent down below the stigma, whose edge they
come in contact with when they afterwards rise up.

Visitors: A. Diptera—Hmpide: (1) Empis livida, L. s. ; (2) E. rustica,
Fallen, s. Also numerous small gnats, licking honey. B. Hymenoptera—
Apide: (8) Andrena parvula, K. 9, s. OC. Coleoptera—WNitidulide: (4)
Meligethes, lh. See also No. 590, II.

129. PRuNus pomesTicA, L., P. avium, L., and P. Cerasus, L.
—Anthers and stigmas ripen simultaneously, and spread apart out
of the flower; the stigmas overtop the inner stamens but stand
on a level with the outer ones. Cross-fertilisation is favoured by
the likelihood of insects touching the stigma and anthers with
different parts of their bodies while sucking the honey secreted by
the receptacular tube. Insects collecting or feeding on pollen must
lead to self-fertilisation and cross-fertilisation indiscriminately. In
flowers obliquely placed, pollen may readily fall from the taller
anthers upon the stigma.

Visitors: A. Hymenoptera—Apide: (1) Apis mellifica, L. 2, 8. very
ab. ; (2) Bombus lapidarius, L. 2 ; (3) B. terrestris, L. 9; (4) B. hortorum,
L. 9, all three sucking ; (5) Osmia rufa, L. 9 ¢, s., ab. ; (6) O. cornuta;
Latr. 9 ¢, s.; (7) Andrena fulva, Schr. 9, s. and c.p.; (8) A. albicans,
K. 9 g, epand s.; very ab. B. Diptera—Syrphide: (9) Rhingia rostrata,
L., s., ab.; (10) Eristalis tenax, L.; (11) E. arbustorum, L., s. C. Lepi-
doptera—Rhopalocera: (12) Pieris brassice, L.; (13) P. rape, L. ; (14) P.
napi, L., all three sucking. See also No. 590, 11.

Tribe Spirwe.

130. SPIRHZA ULMARIA, L.—The flowers contain no honey but
a great quantity of pollen. The stamens at first arch over towards
the middle of the flower, so as to cover the stigmas completely ;
they gradually become erect and incline outwards in centripetal
succession, and the anthers then dehisce, covering themselves all
round with pollen. When the stamens have risen up, the centre
of the flower becomes the most convenient place both for small
insects to settle on, and for larger insects traversing the inflorescence
to step upon. Cross-fertilisation is thus readily performed, but
self-fertilisation is also very liable to occur.

The crowded inflorescences not only attract numerous insects
but also lead to great economy of time in the process of fertilisation.
In the absence of insects, self-fertilisation almost always takes

PART III. | THE MECHANISMS OF FLOWERS. 223

place, and cross-fertilisation may also occur by the outer stamens
of one flower coming to stand over the stigmas of the next.

Fia. 73.—Spirea ulmaria, 1.

1.—Young flower.
2.—Older ditto.

Visitors: A. Hymenoptera—(a) Apidew: (1) Apis mellifica, L. 9, ab.,

.; (2) Andrena Coitana, K. ?, ¢.p. ; (3) Prosopis communis, Nyl. 9, f.p. ;
@) Chryside: (4) Chrysis ignita, L.; (5) Elampus auratus, Wesm. ; (6)
Hedychrum lucidulum, F. (I have never seen Chryside eating pollen, and so
_ I suppose that these species were attracted by the flowers without finding any-
thing useful in them). B. Diptera—(a) Syrphide: (7) Eristalis horticola,
Deg. (Sld.) ; (8) E. arbustorum, L. ; (9) E. nemorum, L. ; (10) E. tenax, L. ;
_ (11) E. sepuleralis, L.,—all eating pollen, in great numbers ; (12) Volucella
jombylans, L. ; (13) Helophilus floreus, L. ; (14) Syritta pipiens, L., all f.p. ;
_ (0) Muscide : (15) Anthomyia sp. C. Coleoptera—(a) Nitidulide : (16) Cy-
chramus luteus, F.; (b) Dermestide: (17) Anthrenus pimpinelle, F. ; (c)
Lamellicornia: (18) Trichius fasciatus, L.; (19) Cetonia aurata, L.,—both
eeding on the tissues of the flower ; (d) Mordellide : (20) Mordella aculeata,
u.; (e) Cerambycide: (21) Pachyta 8-maculata, F, (Sld.); (22) Strangalia
uttenuata, L.,—both feeding on the anthers.

131. Sprr#A FILIPENDULA, L.—The flowers secrete no honey,
and are, therefore, visited only by pollen-seeking insects, which,
Fg wing to the position of the parts, usually alight on the stigmas and
_ perform cross-fertilisation. The petals are bent backwards and
ownwards when the flower is fully expanded, and they are attached
»y such narrow claws that they dip down under the weight of a
small bee or fly, and are, therefore, unsuitable for a standing-place.
The stamens before dehiscing are bent far outwards, and in the

iy
3 entre of the flower nine to twelve broad bifid styles spread out into

224 THE FERTILISATION OF FLOWERS. [PART 1II.

a horizontal plane, forming a disc round whose edge the stigmas, —
directed outwards and upwards, stand. In absence of insects, self
fertilisation may readily take place, simce the innermost stamens —
often remain directed inwards until dehiscence has taken place.

(2) H. sexnotatus, K., 9, cp. B. Diptera—Syrphide: (3) Eristalis arbus-
torum, L.; (4) E. nemorum, L.; (5) Helophilus floreus, L.; (6) Syritta
pipiens, L.-—all eating pollen. _ C. Coleoptera—Lamellicornia: (7) Trichius

;

Visitors: A. Hymenoptera—Apide : (1) Halictus zonulus, Sm., 2, e.p. ;
i]

fasciatus, L., rapidly devouring the anthers. }
Ps

= =.
fog

132. Sprraa ARuNcus, L.—The flowers of this species also are
devoid of honey.

i eda ae

Visitors (in my garden at Lippstadt): A. Hymenoptera—(a) Apide: i
(1) Prosopis signata, Pz. 2 g, f.p. ; (6) Sphegide: (2) Oxybelus bellus, Dlb., —
f.p.; (c) Vespide : (3) Odynerus sinuatus, F., seeking vainly for honey. B.
Diptera—(a) Syrphide : (4) Syritta pipiens, L., fip., very ab. ; (6) Muscidae : —
(5) Species of Anthomyia, f.p. C. Coleoptera—(a) Nitidulide : (6) Meligethes, —
ab.; (6) Dermestide: (7) Anthrenus Scrophularie, L., not rare; (8) A.
pimpinelle, F., very ab. ; (9) A. claviger, L., scarce.

133. SPIRHA SALICIFOLIA, L., S. ULMIFOLIA, L., S. SORBIFOLIA,
L.—These commonly cultivated species secure very numerous
insect-visits by their densely crowded inflorescences and their
abundant pollen and honey. The distinctly proterogynous condi-
tion of the flowers favours cross-fertilisation to a great extent, but —
self-fertilisation is also provided for in case of continuous wet
weather. -An annular, orange-coloured disk in the base of the
receptacular tube, internal to the insertion of the stamens, secretes
abundant honey in the form of small drops. In S. salicifolia, this
disk has ten notches.

Already before the flower opens, the broad stigmas are provided
with papillze and overtop the incurved stamens. When the flower
expands, the stamens gradually rise up, and, one by one, beginning
with the outermost, their anthers dehisce, coating themselves all
round with pollen. The stigmas still remain fresh, and thus, though
at first only cross-fertilisation is possible, later on self-fertilisation
also may take place.

The three species grow with us in the same localities and in
nearly equal abundance. They are visited by the same insects, and ©
I have grouped the visitors in a single list.

A. Diptera—(a) Stratiomyide : (1) Stratiomys riparia, Mgn., s.; (0)
Empide: (2) Empis opaca, F., ab, ; (3) E. tesselata, F., very ab. ; (4) E.

PART III. | THE MECHANISMS OF FLOWERS. 225

| -punctata, F., all three sucking ; (c) Syrphide: (5) Chrysotoxum festivum, L. ;
(6) Pipiza funebris, Mgn. ; (7) Chrysogaster viduata, L. ; (8) Syrphus ribesii,
| L,,fp.; (9) S. excisus, Zett. ; (10) Melithreptus strigatus, Steg. ; (11) Ascia
podagrica, F., s. ; (12) A. lanceolata, Mgn., do. ; (13) Rhingia rostrata, L., s.,

Fic. 74.—Spircea sorbifolia, L.

1.—Young flower.
2.—Older ditto, whose anthers (a) have in part dehisced.
n, nectary ; st, stigma; a, dehisced anther.

very ab. ; (14) Volucella plumata, Mgn. ; (15) Eristalis arbustorum, L. ; (16)

_#. nemorum, L, ; (17) E. sepuleralis, L. ; (18) E. tenax, L.; (19) E. pertinax,

‘Scop. ; (20) E. intricarius, L., all both s. and f.p., very ab. ; (21) Helophilus

| floreus, L., s., freq. ; (22) Xylota ignava, Pz.; (23) X. segnis, Pz. ; (24) X.
Q

226 THE FERTILISATION OF FLOWERS. [parr mr.

lenta, Pz. ; (25) Syritta pipiens, L., s. and f.p., very ab. ; (d) Conopide: (26)
Physocephala rufipes, F., s.; (27) Myopa polystigma, Rondani, s.; (e) Mus-
cide: (28) Gymnosoma rotundata, L.; (29) Echinomyia fera, L.; (30) E.
magnicornis, Zett. (Tekl. B.); (31) Sarcophaga carnaria, L., s.; (32) S.
albiceps, Mgn., do. ; (33) Onesia cognata, Mgn. ; (34) O. floralis, R. D. (both
identified by Herr Winnertz) ; (35) Mesembrina meridiana, L. ; (36) Lucilia
cornicina, F., s.; (37) L. silvarum, Mgn., s. ; (38) Musca corvina, F. ; (39)
Cytoneura simplex, Loew. (identified by Herr Winnertz) ; (40) -species of
Anthomyia; (f) Bibionide : (41) Bibio hortulanus, L., lh. ; (g) Tipulide:
(42) Pachyrrhina pratensis, L., do.; (h) Chironomide: (43) Ceratopogon,
very ab.,s. B. Hymenoptera—(a) Tenthredinide : (44) Tenthredo bicincta,
L., Lh. ; (0) Ichneumonidae : (45) Various ; (c) Formicide : (46) Many small
ants lick the honey, and also capture the numerous small midges which are
attracted by it; (d) Chryside: (47) Hedychrum lucidulum, F. ¢; (e)
Sphegide : (48) Oxybelus uniglumis, L., very ab., s.; (49) O. bellus, DIb.,
do. ; (50) Crabro lapidarius, Pz. ¢, s.; (51) Psen atratus, Pz. s.; (52)
Passalcecus monilicornis, Dlb. 9, 8s. ; (53) Cerceris arenaria, L., not rare ; (54)
Ammophila sabulosa, L. ; (55) Pompilus neglectus, Wesm., s. ; (f) Vespide :
(56) Odynerus quinquefasciatus, F. ; (g) Apide: (57) Halictus sexstrigatus,
Schenck, 9,8. ; (58) H. sexnotatus, K. 9,c.p.; (59) H. flavipes, K. 9 ; (60)
Andrena albicrus, K. 2 ¢,c¢.p. and s., ab.; (61) A. fucata,Sm. 92,5. and
c.p.; (62) A. Schrankella, Nyl. ¢,s. ; (63) A. fulvicrus, K. ¢, s.; (64) A.
parvula, K. 9,8. and c.p., ab. ; (65) A. dorsata, K. 2,8. and e.p., very ab. ;
(66) A. albicans, K. 9,8. and cp., ab. ; (67) A. nigroznea, K. ¢,s.; (68) A.
Trimmerana, K, ?,s.; (69) Osmia rufa, L. 2, c¢.p.; (70) Bombus terrestris,
L. 9, ¢.p. and s.; (71) B. senilis, Sm. 9, cp. ; (72) B. Scrimshiranus, K. 9,

c.p. ; (73) Apis mellifica, L. $, ep. and s. C. Coleoptera—(a) Dermestide : —

(74) Anthrenus scrophularie, L.; (75) A. pimpinelle, F.; (76) A. muse-
orum, L. ; (77) Attagenus pellio, L. ; (78) Byturus fumatus, L., all five very
ab., Lh.; (0) Nitidulide : (79) Meligethes, ab. ; (c) Elateride : (80) Lacon

murinus, L. ; (81) Cardiophorus cinereus, Hbst., Lh.; (d@) Lamellicornia: (82)

Trichius fasciatus, L. ; (83) Phyllopertha horticola, L., both feeding on the
tissues of the flower; (e) Malacodermata ; (84) Malachius bipustulatus, F.,
devouring the anthers; (85) Dasytes flavipes, L. ; (/) Mordellide: (86) An-

aspis frontalis, L., ab. ; (87) A. maculata, Fourc., both lh. ; (g) Cerambycide :—
(88) Clytus arietis, L., 1h. ; (89) Strangalia nigra, L. ; (90) Str. attenuata, L., —

freq. ; (91) S. armata, Hbst. ; (92) Leptura livida, F., very ab. ; (93) Gram-
moptera ruficornis, F., all Lh. ; (h) Cistelide: (94) Cistela murina, L., ab.,
feeding on the anthers and other tissues. D. Neuroptera—(95) Panorpa
communis, L., Lh, ; (96) Agrion, flew not infrequently on to flowers of Spiraea
but apparently only to sun itself (June 4, 1870). E. Lepidoptera—(97) Tor-
trix plumbagana, Tr. ; (98) Adela sulzella, W. V., ab., s. (both identified by
Dr. Speyer). See also No. 590, 1.

Tribe Rubee.

134, Rusus Ipmvus, L.(Raspberry).—In the Raspberry and Black-

berry honey is abundantly secreted by a fleshy ring or disk upon
the border of the receptacular tube, internal to the attachment of
the stamens. In the Raspberry the small narrow petals remain

PART 111.] THE MECHANISMS OF FLOWERS. 227
} erect, and even inclined towards one another above, and the
stamens, which dehisce either on the side towards, or on that away
| from, the centre, have no room to spread out, but remain closely
| packed between the styles and petals ; so that an insect may easily
| insert its proboscis, but scarcely its whole head, between the styles
and stamens to reach the honey-secreting ring. The accessibility of
the honey is thus greatly reduced, but at the same time, since
part of the stigmas come in contact with the anthers, self-fertilisation
/isinsured. In the event of insect-visits cross-fertilisation is easily
accomplished ; for the insect often alights in the centre of the
_ flower, touching the stigmas first, and in bending the head down
_ between stigmas and stamens the former may easily be dusted with
pollen from another flower. The much less conspicuous flowers and
less accessible honey cause insect-visits to be fewer and less varied
_, than in the case of the bramble; and self-fertilisation is very
frequently made use of.

Visitors: A. Hymenoptera—(a) Apide: (1) Apis mellifica, L. $, very
ab., both s. and c.p.; (2) Bombus agrorum, F. 2, s., ab. ; (3) B. pratorum, L.
| 64,8. and cp., freg. ; (4) B. hortorum, L. 9, ep. ; (5) B. senilis, Sm. ?, s. ;

(6) B. silvarum, L. 2, s.; (7) Andrena nigroznea, K. ¢,s. ; (8) A. albicrus,
K. g, 8.3; (9) Halictus sexnotatus, K. 2; (10) H. lucidus, Schenck, $ ; (11)
_H. nitidiusculus, K. ?, all three sucking; (b) Sphegide: (12) Gorytes
_ mystaceus, L. ; (c) Tenthredinide : (13) Tenthredo rustica, L. B. Diptera—
_ Syrphide: (14) Rhingia rostrata, L., s. and f.p. ; (15) Volucella pellucens, L.
- (Sid.),s. and fp. C. Coleoptera—(a) Dermestide : (16) Byturus fumatus, L.,

devouring the anthers and licking honey ; (6) Cerambycidw: (17) Pachyta
8-maculata, F., licking honey and feeding on the tissues of the flower, ab.
in Sid.

135. Rusus Fruticosus, L. (Blackberry, Bramble).—The flowers
of the bramble have advantages in several respects over those of
the Raspberry ; the large petals, spreading out flat, are very con-
_ Spicuous; and the stamens also spreading outwards leave the honey-
| ‘ ecreting ring easily accessible, These two characters induce much
more numerous and varied insect-visits than the Raspberry obtains.
' The outermost anthers are the first to dehisce, and the stigmas
Tipen at the same time; and most flowers have been cross-
_ fertilised before the inner anthers are mature. Insects may alight
with equal convenience either in the centre or at the circumference
| of the flower, and therefore come in contact either with the stigmas
or with the ripe stamens. Only the innermost stamens rise up
after they have dehisced, to come in contact with the outermost
| stigmas.
t z Q 2

— ss

228 THE FERTILISATION OF FLOWERS. [PART III.

Visitors: A. Hymenoptera—(a) Apidew: (1) Apis mellifica, L. §, cp. and
s., very ab.; (2) Bombus agrorum, F. 2; (3) B. terrestris, L. 2; (4) B.
hortorum, L. $; (5) B. pratorum, L. § ¢; (6) B. Scrimshiranus, K. 9 ; (7)
B. silvarum, L. 9, all these humble-bees sometimes suck, sometimes collect
pollen, while the following parasitic humble-bees of course only suck ; (8) B.
(Apathus) vestalis, Foure. 2 ; (9) B. campestris, Pz. 2 ; (10) Macropis labiata,
Pz. $; (11) Andrena Gwynana, K. 9 ; (12) A. albicrus, K. ¢ ; (13) A. thoracica,
K. 2; (14) Halictus zonulus, Sm. ? ; (15) H. lucidulus, Schenck, ? ; (16) H.
villosulus, K. 9; (17) H. sexnotatus, K. 2; (18) H. cylindricus, F. 9g, —
(10)—(18) all sucking ; (19) H. leucozonius, K. 9, c.p. ; (20) H. albipes, F. 9,
c.p. ; (21) Celioxys umbrina, Sm. ? ¢; (22) Nomada ruficornis, L. ¢; (23) —
N. lineola, Pz. ¢; (24) N. lateralis, Pz. 9; (25) N. Fabriciana, L. 2; (26)
Diphysis serratule, Pz. 2 ; (27) Osmia fusca, Christ. ? ; (28) Stelis breviuscula,
Nyl. ¢; (29) Prosopis excisa, Schenck, ¢; (30) P. variegata, F. g; (31) P.
communis, Nyl. ¢, all sucking ; (b) Sphegide: (32) Crabro patellatus, v. d.. 4
L. 2 ¢; (33) Oxybelus uniglumis, L. 2 ¢; (834) Ammophila sabulosa, L.? ¢; :
(35) A. (Miscus) campestris, Jur. ¢ ; (36) Cerceris nasuta, Dlb. g, ali sucking.
B. Diptera—(a) Stratiomyide : (37) Sargus cuprarius, L., s. ; (88) Chrysomyia
formosa, Scop. s.; (b) Empide : (39) Empis livida, L., ab. ; (40) E. tesselata, —
F., both sucking; (c) Syrphide: (41) Ascia podagrica, F.; (42) Syritta
pipiens, L., ab.; (43) Eristalis tenax, L., ab.; (436) Helophilus pendulus, —
L., ab.; (44) Chrysotoxum arcuatum, L. (Sld.) ; (45) Volucella pellucens, L.
(Sld.) ; (46) Rhingia rostrata, L., all sometimes sucking, somtimes collecting —
pollen ; (d) Conopide: (47) Physocephala rufipes, F., s. ; (e) Tipulide: (48)
Tipula oleracea, L., s. C. Coleoptera—(a) Dermestide : (49) Byturus fumatus,
L., s. and feeding on the tissues of the flower ; (b) Eluteride : (50) Diacanthus ©
eneus, L.; (51) Limonius cylindricus, Payk., both feeding on the softer ©
tissues; (c) Lamellicornia: (52) Trichius fasciatus, L., do.; (d) Malaco-
dermata: (58) Telephorus rusticus, L., (54) Malachius bipustulatus, F., do. ; _
(e) Ctdemeride: (55) C&demera virescens, L., do., and licking honey; (f)
Cerambycide : (56) Clytus arietis, L. ; (57) Leptura livida, F.; (58) Pachyta
8-maculata, F. (Sld., ab.) ; (59) Strangalia armata, Hbst. ; (60) S. atra, F. ;
(61) S. nigra, L. ; (62) S. melanura, L., all sometimes licking honey, sometimes
feeding on pollen, anthers, and other parts of the flower; (g) Nitidulide : (63)
Meligethes, ab. D. Lepidoptera—Rhopalocera: (64) Argynnis Paphia, L. ;
(65) Pieris crategi, L.; (66) P. napi, L.; (67) Hesperia paniscus, F., all
sucking. ‘Twenty-six additional visitors are enumerated in No, 590. I.

eS ee

fiubus saxatilis, L., is proterogynous, with long-lived stigmas.
Its arrangements for cross-fertilisation resemble those of Cotoneaster.
The fertilising agents are chiefly bees (609, fig. 85).

Tribe Potentillee.

Dryas octopetala, L., is androdicecious. Its hermaphrodite
flowers are usually feebly proterogynous, after the manner of Gewm
urbanum, Li.; but sometimes the stigmas are covered over by the

parr.) | THE MECHANISMS OF FLOWERS. 229

inner stamens even for some time after the outer anthers have
dehisced, and such flowers therefore are essentially proterandrous

_ (609).

136. GEUM RIVALE, L.—The honey exudes in numerous minute
drops from the base of the receptacular tube, and is diligently
sought by humble-bees while most of the flowers are still in the
bud. Bombus terrestris, L. 9, which steals honey from many
‘different flowers, sucks honey in Gewm rivale also from the -outside
‘in yet unopened flowers, thrusting in its proboscis between the
‘sepals and petals. Even after the flower is expanded, B. terrestris
often, and other species of Bombus occasionally, obtain the honey
in this way; but for the most part humble-bees hang suspended
to the flower, which they grasp with their mid and _ hindlegs,
putting their forelegs and head inside the flower. The outer
_ portion of the honey they seem to reach more easily from the
outside. This liability of the honey to be reached from the out- |
side is a serious imperfection in the flower, which thus gets deprived |
_ of its honey without receiving cross-fertilisation in return.
The flowers are proterogynous, and in young flowers the ripe
stigmas project far beyond the still closed anthers. Cross-
fertilisation is thus insured if at this time a bee inserts its head
in the legitimate manner. Later, the stamens elongate till their —
anthers stand on a level with the outermost stigmas ; in dehiscence, —
the anthers cover themselves all round with pollen. When the
flower closes, the anthers are brought in contact with the outer-
most stigmas, and self-fertilisation results, unless the pollen has
been removed by bees. Since the plant grows sheltered in woods, |
_ it is visited by numerous bees even in unfavourable weather.
According to Mr. T. Whitelegge, @. rivale is occasionally andro- |
-moncecious (774).
_ Visitors: A. Hymenoptera—Apide: (1) Bombus terrestris, L. 9 ; (2) B.
| lapidarius, L. 2; (3) B. confusus, Schenck, ? ; (4) B. hypnorum, L. ? ; (5)
| 8B. pratorum, L. 9 §; (6) B. Scrimshiranus, L. 2 $; (7) B. hortorum, L.
2%, very ab. ; (8) B. agrorum, F. 9; (9) B. fragrans, K. 9, very scarce ;
| (10) B. senilis, Smith, 9; (11) B. silvarum, L. 9, ab., all sucking (B. sil-
_ yvarum, 2, and B. pratorum, §, also collected pollen, hanging back downwards
_ to the flower) ; (12) Apis mellifica, L. $, sucking the flowers from outside,
_ab.; (13) Andrena helvola, L. 9, seeking vainly for honey. B. Diptera—
_ Syrphide (14) Rhingia rostrata, L., very ab.,s. and fp. C. Coleoptera—
Nitidulide : (15) Meligethes, ab.

» Geum reptans, L., and G. montanum, L., are proterogynous and
__androdicecious; that is to say, besides the ordinary individuals

i

230 THE FERTILISATION OF FLOWERS. [PART II.

with hermaphrodite proterogynous flowers, other plants occur in
all of whose flowers the pistil is suppressed while the stamens
remain (609).

137. GEUM uRBANUM, L.—The flowers are much smaller than
those of G. rivale, and appear at a season (July, August) and in
spots where many more conspicuous flowers compete with them.
They accordingly receive few insect-visits, and rely for the most

part on self-fertilisation.

Honey is secreted by a green, fleshy, annular ridge at the
base of the receptacular tube, internal to the insertion of the
stamens. When the flower opens all the stamens are bent inwards,
so that their anthers lie close upon the outer carpels, while the
inner styles with ripe stigmas project in the centre of the flower.
The outermost stamens now bend outwards and the anthers dehisce,
turning their pollen-covered surfaces upwards; when the innermost
stamens dehisce in their turn, some of their pollen almost always
comes upon the outer stigmas. If the flower is visited early by —
insects, its feebly-marked proterogynous dichogamy may insure
cross-fertilisation ; if the visits are deferred till later, crossing may
still be effected by an insect which alights, dusted with pollen,
in the centre of the flower. But self-fertilisation must take place
very often, both spontaneously and by the agency of insects which
alight at the edge of the flower.

I have only observed the following visitors: A. Diptera—Syrphide : (1)

Melithreptus scriptus, L., s. and f.p. B, Coleoptera—Dermestide : (2) Byturus
fumatus, L., f.p.

138. FRAGARIA VESCA, L. (Strawberry).—The honey is secreted —
by a narrow, fleshy ring at the base of the receptacular tube, —
sheltered between the stamens and the outer carpels. The petals
spread out into a level disk, forming a convenient alighting-place
for insects, An insect standing on a petal must, to reach the
honey, thrust its head between the stamens, and bring it in contact
with the stigmas. If both stigmas and anthers ripened together
self-fertilisation would thus be occasioned directly by the insects,
but as a matter of fact the stamens come to maturity much later
than the stigmas. Cross-fertilisation is also favoured by the shape —
and manner of dehiscence of the anthers; for these are expanded
into flat disks, so that the intervening spaces are so much narrowed
that even Halictus and the smaller flies cannot reach the nectary
with their heads, without rubbing against some of the anthers. The

PART III. | THE MECHANISMS OF FLOWERS. ~ at

_ anthers dehisce at their edges, and are only covered with pollen
at these parts. In absence of insects, I have noticed, in the case of
_ plants blooming in my room, that some pollen falls at length upon
the stigmas, in consequence of the oblique (light-seeking) position
of the flower.
Visitors: A. Diptera—(a) Empide: (1) Empis livida, L., s.; (b) Syr-
_ phide: (2) Eristalis sepulcralis, L., s.; (8) Syrphus, s.; (4) Melithreptus
_ menthastri, L., s. ; (5) Rhingia rostrata, L., s. ; (6) Syritta pipiens, L., s., ab. ;
_ (c) Muscide: (7) Anthomyia sp. ; (8) Musca corvina, F. B, Coleoptera—
(a) Dermestide : (9) Anthrents pimpinelle, F., 1h.; (10) A. scrophularia,
iL, Lh. ; (b) Nitidulide: (11) Meligethes, ab.; (c) Malacodermata: (12)
_ Dasytes flavipes, F. ; (13) Malachius bipustulatus, F., both species licking
honey, and also devouring the anthers; (d) Mordellide : (14) Mordella acu-

leata, L., lh. ; (e) Cerambycide : (15) Grammoptera ruficornis, Pz., not rare,

1h., and also devouring the anthers. C. Thysanoptera—(16) Thrips, ab., s.
_D. Hymenoptera—(a) Apide : (17) Prosopis communis, Nyl. 2; (18) Hal-
_ ictus’ lucidulus, Schenck, 9, s. ; (19) H. sexstrigatus, Schenck,? ; (20) An-
drena dorsata, K. 2, ¢.p.; (21) Nomada sexfasciatus, Pz. ¢; (22) N. rufi-
cornis, L. 2, s,; (23) N. signata, Jur. ¢,s.; (24) Apis mellifica, L. $, cp. ;

_ (b) Sphegide : (25) Oxybelus uniglumis, L., Lh, See also No. 590, 1, and

No. 609.

In the United States, cultivated species of Fragaria incline to
- dicecism.

: 139. PoTENTILLA VERNA, L.—The annular ridge on the inner
wall of the receptacular tube, which surrounds the base of the
stamens and is marked by its dark, sometimes reddish-yellow,
colour, and bright polished appearance, secretes honey not in drops
but in a very evident smooth adherent layer. The anthers get
covered on both sides with pollen, and ripen simultaneously with
the stigmas. Insect-visitors alight sometimes in the middle of the
flower, sometimes on the petals ; in the latter case they dust them-
selves with pollen, but are not likely to come in contact at all with
the stigmas, as the honey-secreting ring lies farther outwards than

| in the preceding species ; if they alight in the middle of the next

flower, cross-fertilisation is accomplished. Self-fertilisation must
in any case be a frequent occurrence. In dull weather the flowers
close partially, and at night they shut completely, bringing the
anthers in contact with the stigmas.

Visitors (from April 21 to May 24): A. Hymenoptera—Apide : ©
“Halictus leucopus, K. 9,s. and cp. ; (2) H. flavipes, K. ?,¢.p.; (3) H

-sexstrigatus, Schenck, 2, c.p.; (4) H. cylindricus, F. 2, cp. ; (5) Andrena
albicans, K. 2 ¢, ep. and s., ab. ; (6) A. albicrus, K. ¢,s.; (7) A. nana, K.
: | = s.; (8) A. argentata, Sinith (= A. gracilis, Schenck), g,s.; (9) A. fulvi-

232 THE FERTILISATION OF FLOWERS. [PART III.

crus, K. ¢,s.; (10) A. parvula, K. 9,s.; (11) A. dorsata, K. 9,¢p.; (12)
A. chrysosceles, Nyl. 9, s.; (13) Nomada ruficornis, L. ¢ ; (14) Osmia
fusca, Christ. (bicolor, Schrank), 9, s. and c.p.; (15) Apis mellifica, L. §, s.
B. Diptera—(a) Stratiomyide : (16) Odontomyia argentata, F., s. ; (b) Syr-
phide : (17) Syritta pipiens, L., s.; (18) Syrphus, s.; (19) Rhingia rostrata,
L., s.; (20) Cheilosia preecox, Zett., ab.,s.; (21) Ch. modesta, Egg.,s.; (ce)
Muscide: (22) Pollenia vespillo, F.; (23) Onesia cognata, Mgn.; (24) O.
floralis, R. D.,—all three sucking. C. Coleoptera—Nitidulide : (25) Meligethes,
licking honey, ab. See also No. 590, 11.

= FS ZZ,
Z j

7
}

!) f
i] }
|

Fia. 75.—Potentilla minima, Haller fil.

A.—Flower, from above (x 7).

B.—Ditto, in longitudinal section.

C.—Upper end of a stamen ; the anther has dehisced laterally (x 35). ;

a, epicalyx; b, calyx; c, corolla; d, stamen;‘e, yellow fleshy ring on which the stamens are in-
serted, and which secretes honey; /, internal orange-coloured part of the ring, which becomes
covered with a layer of honey; g, ring of hairs which protect the honey h, orange spot at the base
of each petal (pathfinder); ¢, carpel.

(Heuthai, Berninahaus, August 8, 1877.)

Potentilla minima, Haller jil—The annexed figure may serve
as an illustration of a simple, open, regular flower, cross-fertilised
by a miscellaneous lot of short-lipped insects, which has already
acquired, besides a nectary, a honey-receptacle, a contrivance to
shelter the honey, and guides or pathfinders to point towards it.

140. PoTENTILLA REPTANS, L.—The floral mechanism resem-
bles that of P. verna, and the fertilising agents in like manner
are chiefly the less specialised bees, |

iN

anrut.] THE MECHANISMS OF FLOWERS. 233

_ A. Hymenoptera—Apide: (1) Prosopis armillata, Nyl. ? ; (2) Pr.
hyalinata, Sm. 2 ; (8) Halictus maculatus, Sm. ?, ¢.p.; (4) H. leucozonius,
Schrank, 9, ¢p.; (5) H. sexstrigatus, Schenck, 9, c.p. and s.; (6) Andrena
albicrus, K. ¢; (7) A. nana, K. ¢,s.; (8) Sphecodes gibbus, L. ¢,s.; (9)
Nomada xanthosticta, K. ¢,s.; (10) N. succincta, Pz. ¢,s.; (b) Sphegide:
(11) Ammophila sabulosa, L. ¢. B. Diptera—Syrphide : (12) Syrphus
reuatus, Fallen, fp. See also No. 590, 11.

141. PoTENTILLA ANSERINA, L.—The floral mechanism resembles
shat of P. verna.

Visitors: Hymenoptera—(a) Apide : (1) Halictus flavipes, K. 9, cp.
2) H. sexstrigatus, Schenck, 9, c.p. ; (b) Sphegide : (3) Oxybelus uniglumis,
L; (4) O. bellus, Dib. See also No. 5y0, 11, and No. 609.

142. PoreNnTILLA FRUTICOSA, L.—In this flower also I have
failed to discover distinct drops of honey, but the smooth shining
‘ing or disk at the base of the receptacular tube, surrounding the
tigmas, is so much visited by insects, including even the honey-
ee, that I can scarcely doubt that a thin layer of honey covers the
pidermis in this part. The stigmas ripen simultaneously with the
nthers, which dehisce laterally. Insects, as they happen to
ight in the centre of a flower or on a petal, touch stigmas or
tamens first, and thus cross-fertilisation and self-fertilisation seem
qually probable. In absence of insects, some of the stamens curve
vwards as they wither, and come, still dusted with pollen, in con-
with the stigmas. In sunny weather the conspicuous flowers
tract very numerous insects.

Visitors: A. Hymenoptera—(a) Apidew: (1) Apis mellifica, L. §, ab.
ne bee alights in the middle of the flower, and turning round passes its
mgue over the whole honey-bearing ring which surrounds the bases of the
ameus,—it effects cross-fertilisation regularly) ; (2) Halictus zonulus, Sm.
}, also licking honey ; (0) Sphegide: (3) Oxybelus bellus, Dlb., very ab.
ten four at once in a flower; (4) O. unigiumis, L., scarce, both licking
mey. B. Diptera—(a) Stratiomyide: (5) Sargus cuprarius, L., ab. ; (d)
abanide: (6) Chrysops cecutiens, L. ¢; (ce) Syrphide: (7) Eristalis
pulcralis, L.; (8) E. arbustorum, L.; (9) Helophilus pendulus, L. ; (10)
. floreus, L. ; (11) Melithreptus teeniatus, Mgn.; (12) Syritta pipiens, L.
(11) all ab., sometimes 1.h., sometimes fp. ; (d) Conopide: (13) Sicus
Tugineus, L.; (e) Muscide: (14) Sarcophaga carnaria, L.,ab. ; (15) Lucilia
varum, Mgn.; (16) L. Cornicina, F., both ab.; (17) Anthomyia, very ab. ;
8) Scatophaga merdaria, F., ab. ; (19) Sepsis, very freq. (12)—(18) only 1.h.
_ Coleoptera—(a) Nitidulide : (20) Meligethes, very ab., fp. ; (6) Malaco-
ermata ; (21) Dasytes flavipes, L., licking honey and devouring the anthers.

143. Porentitta TorMENTILLA, Nestl.—The floral mechanism
| iS as in P. verna, but the secretion of honey is more evident. The

234 THE FERTILISATION OF FLOWERS. [PART IIL.

flattened anthers dehisce edgewise as in Fragaria, and only their
thin edges remain coated with pollen.

Visitors: A. Hymenoptera—Apide : (1) Andrena denticulata, K. 2 g,s.
and cp.; (2) A. parvula, K. 2, cp. B. Diptera—(a) Bombyliide: (3) Sys-
teechus sulfureus, F., s, (Sld.) ; (b) Syrphide : (4) Chrysotoxum:bicinetum, L.,
freq. (Sld.) ; (5) Melithreptus scriptus, L., f.p. ; (6) Cheilosia sp. (pictipennis,
Egger ?), f.p. See also No. 590, 11, and No. 609.

Potentilla iiaouiek: Lodd.—The flowers, according to
Delpino, are proterandrous, with short-lived stigmas: in the first
stage the anthers are unripe and radiate outwards; in the second,
they stand erect on a level with the stigmas. Andrena and
Halutus were observed to visit the flower (178, 360).

Potentilla argentea, L.—Twenty species of insect-visitors are
enumerated in my Weitere Beobachtungen, I. :

Potentilla Salisburgensis, Haenke (= P. aurea, var. 8), P. aurea,
L., P. grandiflora, L., P. caulescens, L. (vide Die Alpenblumen, pp.
218222),

Sibbaldia procumbens, L.—The honey lies fully exposed, and
the tiny, greenish-yellow flowers are abundantly visited by small,
short-lipped insects (Muscide, Ants, Ichneumonide),. Stigmas and
anthers ripen simultaneously, but stand too far apart for spontaneous
self-fertilisation to take place (609, fig. 87).

Tribe Poteriec.

144, ALCHEMILLA VULGARIS, L.—The tiny flowers are desti-
tute of a corolla. A yellow fleshy ring on the inner wall of th

Fia. 76.—Alchemilla vulgaris, L.
a —Flower with | pce stamens and short style, from above.

2.—Ditto, viewed obliquely, from above,

8.—Ditto, with three perfect and one abortive stamen, and perfect style.
4,—Ditto, with style still more developed, and all the stamens abortive.
a, epicalyx ; b, calyx ; ¢, stainen; c’, abortive stamen ; d, stigma; e, nectary.

receptacular’ tube, which surrounds the style and, later on, th
ovary, secretes a thin layer of honey and gives a greenish-yello
appearance, at a little distance, to the whole inflorescence. Owin

ART III. | THE MECHANISMS OF FLOWERS. 235

to the small supply of honey, insects with long proboscides do not
Hy visit the flower or do so sparingly, and beetles and other insects
which are only attracted by bright colours are also absent.
_ Cross-fertilisation is favoured by partial separation of the sexes,
Flowers seldom occur in which both male and female organs are
equally developed. In the great majority of flowers either the
stamens are fully developed and the pistil remains so short as
scarcely to project above the honey-secreting ring (Fig. 76, 1, 2),
or the style is long and exserted (Fig. 76, 4), and the anthers
completely aborted: sometimes, however, flowers occur (Fig. 76,
_ 3) in which one or two stamens are developed in addition to the
pistil, the others being suppressed.
I have never observed a case of self-fertilisation.
At Lippstadt I have found Alchemilla vulgaris, L., visited by
one of the Syrphide, Xanthogramma citrofasciata, Deg. ; on the
Alps by three butterflies and six flies (Alpenbl. pp. 223, 224).
Alchemilla alpina, L., A. jfissa, Giinth., and A. pentaphylia, L.,
are frequented by short-lipped insects, and do not differ materially
in their arrangements for fertilisation from A. vulgaris. They
show all transition-stages between hermaphrodite and purely female
flowers; and in A. /issa, at least, among very many flowers
bearing seed I found none with more than one stamen, so that
flowers with more than one stamen seem to have lost their female

~ functions (609).

145. AcRimoniA EvpatoriA, L.—The two styles, which project
rom the centre of the flower, are united at their base to a fleshy
ring, on which I have not observed honey. The five to seven
| stamens, which are inserted at the edge of this disk, bend slightly
, inwards; their anthers, which dehisce laterally, stand on a level
/ with the stigmas, and come in contact with them before withering
ny bending still farther inwards. Insect-visits are scanty, and
nust, in many cases, induce mainly self-fertilisation, for cross-
’ fertilisation only results when the insects alight well in the centre
of the flower. Since all the flowers are found to produce seed,
’ self-fertilisation is doubtless quite efficient.
| __ Eug. Warming gives a thorough description of the development
| of the flower (762).
Visitors : A. Diptera—(a) Syrphide: (1) Syritta pipiens, L. ; (2) Ascia
7 yodagrica, F.; (3) Melithreptus scriptus, L. ; (4) M. dispar, Loew. ; (5) M.
‘pictus, Mgn. ; (6) M. teeniatus, Mgn.; (7) Melanostoma mellina, L.; (8)
Eristalis tenax, L., all fp. only ; (9) Rhingia rostrata, L., do. ; (b) Muscide :

236 THE FERTILISATION OF FLOWERS. [PART III. |

(10) Anthomyia sp., fp. B. Hymenoptera—Apide : (11) Halictus, small
species, 2, c.p.

146. PoTErIuM SancuisorBA, L., is anemophilous, with red
penicillate stigmas, and anthers hanging out of the flower on long
thin filaments. On June 27, 1869, I saw a wasp, Odynerus
parietum, L. 3, settle on the flower, attracted probably by the
red colour; but after a short and vain search it flew away again.

147, SANGUISORBA OFFICINALIS, L.—The flowers are devoid
of petals, whose function devolves entirely upon the calyx. The

Fic. 77.—Sanguisor ba officinalis, L.

A —Flower, viewed from above.
B.—Ditto, from the side.
C.—Ditto, in longitudinal section
D.—A sepal, from the inside. (x 7.)

calyx, in its lowest! part, surrounds the ovary ; its middle portio 2
constituting a fleshy ring around the base of the style, secretes
honey ; and its uppermost part spreads out into four dark purple
sepaline lobes. Anthers (a) and stigmas (st) are developed simul.
taneously. The divided stigma resembles that of an anemophilous
flower, and is doubtless a character inherited from an anemophilous
. ancestor resembling Poteriwm (609). :

Tribe Rosew.

148, Rosa cAntnA, L.—-The upper border of the calyx-tube
internal to the attachment of the stamens, is provided with a thick
fleshy ring, which closely surrounds the styles, letting the stigmas
only protrude. The flowers seem either to secrete no honey at ¢

1 'The lowest and middle part really belong to the receptacular tube.

art im.] | THE MECHANISMS OF FLOWERS. 237

or only a thin adherent layer of it; at least, I have never found drops
of honey, in spite of repeated searching: The flowers, which attract
‘notice by their large petals and their strong scent, compensate the
“numerous insect-visitors for the want of honey by the abundance of |
pollen which the numerous stamens supply. The ring surrounding |
he style is of material importance ; for since the stamens, when the
lower opens, are inclined outwards and the petals remain directed
more or less upwards, the ring and the stigmas within it form the
mly convenient alighting-place for insects: thus insects coming
lusted with pollen from another flower are brought into contact
vith the stigmas first. And this is the only character present to
sromote cross-fertilisation, for stigmas and anthers come to maturity
together.

Tn long-continned dull or rainy weather, insect-visits may cease
Imost completely; but the flowers, turning towards the sun, all
tand more or less obliquely, so that part of the pollen falls upon

e stigmas.

— A. Hymenoptera—A pide : (1) Apis mellifica, L. §, ¢.p.; (3) An-
a albicans, K. 9 ¢, ¢.p.and fip.; (3) A. fucata, Sm. 2, c.p. ; (4) Halictus
itidus, Schenck, ?, ¢.p.; (5) Megachile circumcincta, K. 2, ¢.p. ; (6) Prosopis
ommunis, Nyl. 9 ¢,f.p., ab. B. Diptera—Syrphide : (7) Helophilus floreus,
1; (8) Syritta pipiens, L., ab., both fp. C. Coleoptera—(a) Nitidulide: (9)
Meligethes, ab. ; (b) Dermestide: (10) Anthrenus pimpinelle, F.; (11) A.
erc phulariz, L,, both ab., fp.; (¢) Malacodermata: (12) Anthocomus
iatus, L. ; (d) Edmallicobata’: (13) Cetonia aurata, L. ; (14) Phyllopertha
" ticola, L. (both often bite large holes in the petals, shit often even devour
le stigmas and all the anthers) ; (e) Mordellide : (15) Mordella aculeata, L. ;
6) Anaspis frontalis, L. ; (f) Cerambycide : (17) Rhagium inquisitor, F. ;
18) Strangalia armata, Hbst.; (19) S. nigra, L., devouring the anthers and
hher delicate tissues; (gy) Chrysomelide : (20) Luperus flavipes.

Sse RTE Oy Se eg EM F-

149. Rosa ceNnTIFoLIA, L.—In consequence of its more con-
picuous flowers, this species is still more largely visited by insects ;
or though I have observed it more rarely than R. canina, I have a
mger list of its insect-visitors.

A. ao Apide: (1) Andrena albicans, K. 2? ¢, ¢. nt and f.p.,
ery ; (2) A. pilipes, F.-9? ¢, do., scarcer ; (3) A. dorsata, K. 9°, “P>
b. 5 ; ra alictas zonulus, Sm. 9? ; (5) H. sexstrigatus, Schenck, 9; (6) H
xnotatus, K. 9, all three c.p.; (7) Megachile cireumcincta, K. ? ; (8) M.
er tuncularis, L. 2, both ¢.p., ab. ; (9) Prosopis propinqua, Nyl. 2 ¢; (10)
communis, Nyl. ? ¢, both very ab., fp. ; (b) Chryside : (12) Chrysis ignita,
—4L.; (13) Chr. cyanea, L. ; (c) Sphegide : (14) Crabro patellatus, v.d. L. B.
_ Diptera—Syrphidw: (15) Brachypalpus valgus, Pz.; (16) Eristalis eneus,
_Scop.; (17) E. nemorum, L.; (18) Chrysogaster viduata, L. ; (19) Syritta

}

| , sys Fok
_ accessible honey attract many insects, and cross-fertilisation is_

agi _— se

238 THE FERTILISATION OF FLOWERS. [PART III,

pipiens, L., all fp. C. Coleoptera—(a) Nitidulide : (20) Meligethes, ab. ;
b) Dermestide : (21) Anthrenus pimpinelle, F.; (22) A. scrophularie, id
ab. ; (23) A. claviger, Er., scarce ; (c) Malacodermata : (24) Dasytes sp., scarce ;
(25) Anthocomus fisbinkas L., at (d) Lamellicornia : (26) Cetonia aurata 7

L.; (27) Phyllopertha horiesia’ L .; (28) Melolontha vulgaris, L., all three —
devouring the soft tissues indiscriminately ; (¢) Mordellide : (29) Mordella
aculeata, L. ; (30) Anaspis ruficollis, F.; (f) Cistelide: (81) Cistela murina, —
L. ; (g) Cerambycide : (32) Strangalia atra, F.; (33) S. attenuata, L.; (34) —
Grammoptera ruficornis, F., very freq. ; (35) Clytus arietis, L., all feeding
on the soft tissues, especially the anthers.

r
£
?,
&

These last two lists not only afford a new example of how”
increasing conspicuousness leads to more numerous insect-visits } |
but they also disprove Delpino’s theory, that the proper fertilisers —
of Roses are Cetoniw: and Glaphyr ide and that therefore the —
geographical distribution of Roses is limited by the range of these _ €
beetles.t

Rosa rubiginosa, L., Sab hs: an obvious secretion of honeys

(590, IL).

Tribe Pomee.

150. Pyrus Mats, L.—The five stigmas overtop the stamens —
and ripen before them. The conspicuous flowers and easily

insured by the proterogynous condition, and also by the prominent
position of the stigmas. In the absence of insects, self-fertilisation
results ; for most flowers are directed sideways, towards the light, so”
that pollen can fall of itself upon the stigmas. Here and there
flowers occur in which the stigmas are in immediate contact with |
the anthers.

Visitors : A. Hymenoptera—(a) Apidew: (1) Bombus terrestris, L. ? ; (2)
B. agrorum, F. ?; (3) B. lapidarius, L. 2; (4) B. hortorum, L. 9, all four
very ab.; (5) Apis mellifica, L. $ ; (6) Anthophora pilipes, F. 2; (7) An-
drena albicans, K. ¢ 9, all seven s. and ¢.p. ; (8) Halictus sexnotatus, K. 2, s. ;
(9) Osmia rufa, L. ¢, s. (the bees almost: always alight in the middle of the
flowers, and so usually perform cross-fertilisation even in older flowers, since
the stigmas are the first to touch the pollen-covered belly of the insect). (0)
Formicide; (10) various species, ab., s. B, Diptera—(a) Bombyliide : (11) _
Bombylius major, L., s. ; (b) Empide : (12) Empis livida, L., s.; (e) Syrphide =
(13) Rhingia rostrata, L., very freq., usually s. but also f.p.; (14) Syrphus
pyrastri, L., s. and f.p.; (d@) Muscide: (15) Onesia floralis, R. D., s.; (e)
Bibionide : (16) Dilophus vulgaris, Mgn., very ab., s.

a Alcuni App. p. 18, “Le peonie e le rose debbono arrestarsi dove st ‘arrestano
le Cetonie.”

rerur] § THE MECHANISMS OF FLOWERS. 239

} 151. Pyrus communis, L.—The stamens are here longer than |
he styles, but when the flower opens they are curled inwards and
immature, while the stigmas are ripe and project. Cross-fertilisa- |
tion is insured only if insects come soon after the opening of the
flower. In absence of insects, self-fertilisation takes place as in
Pyrus Malus. I have often observed by experiment how easily
pollen from a ripe stamen adheres to the stigmas of a flower, long
efore its own anthers are ripe.
_ Visitors: A. Diptera—(a) Syrphide : (1) Eristalis tenax, L., very ab. ; (2)
®. arbustorum, L.; (3) E. nemorum, L., ab, ; (4) E. intricarius, L. ; (5)
| Syritta pipiens, L. ; (6) Ascia podagrica, F., both ab. ; (7) Melanostoma mellina,
L,, all the Syrphide both s. and f.p. ; (b) Muscide : (8) Anthomyia radicum,
'R.D. ¢ 9, very ab. ; (9) Pollenia Vespillo, F.; (10) P. rudis, F. ; (11) Musca
corvina, F, ; (12) M. domestica, L. ; (13) Lucilia cornicina, F. ; (14) Calliphora
-erythrocephala, Mgn.; (15) Sepsis sp., all s.; (16) Scatophaga merdaria, F.,
‘s. and fp. B. Hymenoptera—(a) Apidw: (17) Apis mellifica, L. $, very
ab.,s. and c.p.; (18) Bombus terrestris, L. 2, s., scarce, and flying away after
siting a few flowers ; (19) Andrena albicans, K. ? ¢, ¢.p. and s., ab. ; (20)
.. Gwynana, K. 2; (21) A. parvula, K. 2 ; (22) A. Collinsonana, K. 9, all
both s. and ec. P- 5 (23) Halictus rubicundus, Chr. 9, ¢.p. and s. ; (6) Formicide :
24), Lasius niger, L. %, 1h. ; (c) |Tenthredinide : (25) Dolerus gonager, K1.,
e; (26) Nematus capreee, L., freq., s. C. Coleoptera—(a) Nitidulide :
27) Meligethes, ab. ; (0) Civculiowides ; (28) Rhynchites squatus, L.; (¢)
occinellide : (29) Coccinella 14-punctata, L. ; (d) Phalacride : (30) Olibrus
peus, F., all four licking honey. D. Thysanoptera—(31) Thrips, ab.

152. Pyrus AucupaRIA, Gert.—When the flower opens, the
amens are still immature, the outer ones standing erect, the inner
‘ones bent inwards so that their anthers are placed below the
igmas. The stigmas are ripe, and project in the centre of the,
ower. The anthers, which open inwards, cover themselves all |
‘round with pollen. In cold, dull weather, the innermost anthers —
jremain bent down below the stigmas even after dehiscence; the
. : er ones stand above the stigmas, incurved towards them; thus,
}im absence of insects, self-fertilisation takes place readily. On the
/ other hand, in warm sunshine, the stamens are inclined away from
\t e stigmas, and the honey-secreting ring is visible between,
| protected with hairs issuing from the base of the style. Insects, in
‘di pping down to the honey, touch stamens and stigmas with
| Mpposite sides of their heads. The small flowers are rendered
bi mspicuous by aggregation, and the rich supply of honey attracts
" ry numerous insects.

Visitors : A. Hymenoptera—(a) Apide: (1) ae mellifica, L. $,s. and
. py very ab. ; (2) Andrena albicrus, K. 9 ¢; (3) A. albicans, K. 9, very

240 THE FERTILISATION OF FLOWERS. [PART III.

ab. ; (4) A. dorsata, K. 9 ¢, all three sucking and collecting pollen ; (5) A.
Smithella, K. 9, ¢p.; (6) A. atriceps, K. 2; (7) A. convexiuscula, K. 9;
(8) Halictus rubicundus, Chr. 2; (9) H. zonulus, Sm. ¢, all sucking and
collecting pollen ; (10) Nomada ruficornis, L. 9? ¢; (11) N. signata, Jur. 2,
both sucking ; (b) Formicidw: (12) Formica congerens, N. % ; (13) Lasius”
niger, L. § ; (14) Myrmica sp.,$, all three s., ab. B. Diptera—(a) Empide:
(15) Empis livida, L. ; (16) E. rustica, Fallen, both s., ab. ; (b) Syrphide :
(17) Helophilus floreus, L. ; (18) Eristalis arbustorum, L. ; (19) E. nemorum,
L. ; (20) E. horticola, Mgn. ; (21) Rhingia rostrata, L., all five s. and fp., ab. ;
(c) Muscide: (22) Echinomyia fera, L.; (23) Onesia floralis, R. D. ; (24)
Scatophaga stercoraria, L. ; (25) S. merdaria, F., the last three ab., s.; (26)
Sepsis, ab. ; (d) Conopide: (27) Myopa testacea, L.; (e) Bibionide: (28)
Dilophus vulgaris, F., ab., s.,—besides several undetermined flies and midges.
C. Coleoptera—(a) Nitidulide: (29) Epurea; (30) Meligethes, both in
hundreds; (b) Dermestide: (31) Byturus, in hundreds; (32) Attagenus

pellio, scarce ; (c) Elateride: (33) Agriotes aterrimus, L.; (34) Dolopius —
marginatus, L. ; (35) Corymbites holosericeus, L. ; (36) Limonius cylindricus, —
Pk. ; (37) L. parvulus, Pz.; (d) Lamellicornia: (38) Cetonia aurata, L. ;
(39) Melolontha vulgaris, L., both devouring all the tissues of the flower ; (e) —
Malacodermata : (40) Malachius zneus, F., 1.h., and devouring the anthers ;_
(f) Mordellide: (41) Anaspis rufilabris, Gylh.; (9) Tenebrionide: (42) —
Microzoum tibiale, F. !—only once ; (2) Cureulionide : (43) Apion sp. ; (44) _
Phyllobius maculicornis, Germ., both s.; (¢) Cerambycide: (45) Clytus (
arietis, L., s.; (&) Chrysomelide : (46) Adimonia sanguinea, F,, s. |

153. Crarzaus OxyacantHa, L.—The flowers resemble those —
of Pyrus Aucuparia in regard to their proterogyny, the manner
dehiscence and the bending inwards .of their stamens, and hence
also in the great likelihood of cross-fertilisation. The outer stamens |
begin to dehisce one or two days after the opening of the flower,
Dung-flies and flesh-flies are attracted in special abundance by |
the odour of the flowers. In absence of insects, many flowers
fertilise themselves. The young shoots sometimes exude a sweet
sap, which is sought by insects. On May 9, 1868, on bushes that
were just beginning to flower, I saw <Anthophora pilipes, F. 6,
Bombus terrestris, L. 2, an Andrena, and Odynerus parietum, L.
all feeding on this sap.

Visitors: A. Diptera—(a) Empide : (1) Tachydromia connexa, Mgn., ab. ;
(2) Empis livida, L.,s., very ab.; (3) Microphorus velutinus, Macq. (identified by
Herr Winnertz) ; (b) Syrphide: (4) Pipiza notata, Mgn. ; (5) Rhingia rostrata,
L., 8., very ab. ; (6) Eristalis tenax, L. ; (7) E. intricarius, L. ; (8) E. nemorum,
L.; (9) E. arbustorum, L. ; (10) E. sepulcralis, L.; (11) E. pertinax, Scop,
—all the species of Eristalis s, and f.p. ; all except E. intricarius very ab. ; (12)
Helophilus floreus, L. ; (13) H. pendulus, L., both ab. (14) Xylota segnis, L. ;
(c) Muscide: (15) Echinomyia fera, L.; (16) Sarcophaga carnaria, L., s. ;
(17) Onesia floralis, R. D., 8. ; (18) O. sepuleralis, Mgn., s. ; (19) Graphomyia

parti.) THE MECHANISMS OF FLOWERS. 241

“maculata, Scop. ; (20) Mesembrina meridiana, L. ; (21) Cyrtoneura sp. ; (22)
fe icia serva, Mgn. ; (d) Bibionidw: (23) Bibio Marci, L., s. ; (24) Dilophus
vulgaris, L., very ab. B. Coleoptera--(a) Dermestide : C5) Attagenus pellio,
a, 1h. ; (26) Anthrenus scrophulariz, L., very ab. ; (27) A. pimpinelle, F.,
7) ‘Il more ab.; (28) A. claviger, Er., scarce, all three Lh. ; (b) Nitidulide :
(29) Meligethes, Lh., very ab. ; (e) Bugréaides (30) Anthaxia nitidula, L. ;
(d) Malacodermata : (31) Malachins (elegans, Ol. ?), feeding on the anthers ;
(32) Telephorus testaceus, L.; (e) Gidemeride: (33) Asclera coerulea, L. ;
f) Mordellide : (34) Anaspis frontalis, L., ].h. ; (35) Mordella abdominalis,
P., Lh. ; (g) Cerambycide: (36) Clytus bsvetions. L., Lh. ; (37) Grammoptera
. Bicornic, F., ab., Lh. ; (h) Chrysomelide : (38) Clythra cyanea, F., gnawing
the petals. C. Pyinenopters-— Api : (89) Andrena Schrankella, Nyl. g,s. ;

40) A. helvola, L. 9, s.; (41) A. fulvicrus, K. 2 ¢, s.; (42) A. nitida, K
2 S, very freq., s. and c.p.; (43) A. varians, Rossi, 2 ; (44) A. Trimmerana,
K. 9 6; (45) A. atriceps, K.? ¢; (46) A. Gwynana, K. 9 ; (47) A. fulva, K. 9 ;
(48) A. albicans, K. 9 4, very ab.; (49) A. dorsata, K. 2; (50) A. chryso-
“seeles, K. 9; (51) A. parvula, F. 9; (52) A. connectens, K. 9, the last ten
‘both s. and c.p. ; (53) Halictus cylindricus, K. 2, s.; (54) Nomada ruficornis,
L929 6,58.3 (55) N. signata, Jur. 9; (56) Eucera longicornis, L. ¢,s8.; (57)
Apis mellifica, L. $, s. and e.p., ab.

154. CorongasTeR vuLcaris, Lindl—This plant in the Alps
ften grows on the same rocks to which a wasp (Polistes gallica)

Ny Cr WM} }

O10)
Oy

Fic 78.— Cotoneaster vulgaris, Lind .

A.—Flower, in slightly oblique side view.
B.—Ditto, from above.

C.—Ditto, in longitudinal section.

nm, nectary. (xX 7.)

(From Rosegthal, Pontresina, June 18, 1879.)

s attached its stalked, open nest. The hemispherical calyx of
flower is filled with honey, which the petals arch over and pro-
tect t, excluding a great many insects. I have found the flowers

| t ited solely by the above-mentioned wasp, whose head just fits
0 the flower. Cross-fertilisation is insured by proterogyny ; in
bsence of insects, self-fertilisation occurs (600).
} R

242 ‘THE FERTILISATION OF FLOWERS. [PART IIT.

Amelanchier vulgaris, Moench. (Aronia rotundifolia, Pers.).—
This plant is imperfectly proterandrous. Of the three whorls of
stamens, the outermost dehisce, while the others are still bent in- —
wards and shelter the immature stigmas. The inner anthers and
the stigmas are ripe together (609).

REVIEW OF THE ROSACE.

t
:
;
if

In all honey-yielding Rosacez the honey is secreted and
carried by an annular region (disk) of the inner wall of the re- |
ceptacular tube, sometimes closely surrounding the pistil, some-
times shifted farther outwards: this ridge shows all transitions
between abundant and evident drops of honey, a thin sweet
layer invisible to us but eagerly licked by insects, and, lastly,
absolute barrenness.

The abundance of insect-visits depends here, as elsewhere, on
the conspicuousness of the flowers and the amount of spoil they
furnish ; and, similarly, the variety of insects which frequent the
flowers ‘depends on the accessibility of the spoil. For instance,
the small, yellow, honeyless flowers of Agrimonia Hupatoria are
sparingly visited by a few pollen-feeding Syrphidew and pollen-
collecting bees; while the equally honeyless roses attract a very
numerous company of insects, which come for the sake of the
pollen and the delicate tissues of the flower. The effects of
conspicuousness are well illustrated by the Raspberry and the.
Blackberry. The effect of diminished accessibility of the honey
in restricting the variety of insect-visitors is shown in the case
of Gewm rivale; the flowers of which remain half-closed, and,
though yielding abundant honey, are only visited by specially
long-tongued bees and flies (Bombus and Rhingia): the Rasp-
berry and Blackberry may be contrasted to illustrate this poin }
also. 7 |

In Rosaceze whose honey lies concealed and which are fertilised
by a motley crowd of short-lipped insects, the flowers are for
most part greenish-yellow, yellow, or white in colour; in Comarwi
palustre, Potentilla atrosanguinea, and Sanguisorba officinalis they are
dark-red or purple, probably owing to the influence of carrion
feeding flies. |

In Rosaceze whose honey lies more deeply placed, which aré
mainly fertilised by long-tongued bees, we find in part red colour

ani] THE MECHANISMS OF FLOWERS. 243

(Amygdalus Persica, Cydonia japonica). In this relation the
- genus Geum is interesting ; for that species which is fertilised by
bees (G. rivale) exhibits a red colour in which the influence of the
primitive yellow is still evident.

Rosaceve visited for the sake of their pollen have white flowers
when their chief visitors are small, short-lipped insects (Spirwa
Ulmaria, S. Aruncus) ; but show a tendency to red when frequented
~ mainly by bees or Syrphide (Rosa). In the whole order of Rosacez
‘no species seems to have acquired a violet or blue flower, nor to have
_ become adapted exclusively for fertilisation by Lepidoptera.

Orv. SAXNIFRAGACE.

Tribe Saxi/ragee.

_ Dr. A. Engler? has investigated thirty-eight species of Saaifraga
and found them to be all proterandrous with movement of the
amens singly in succession towards the middle of the flower.
“On the other hand, he found Bergenia (Saxifraga crassifolia, L.),
Mitella, L., Heuchera, L., and Drummondia, DC. (= Mitella pent-
andra, Hook.) to be proberogynous without movement of the
tamens (221). On species of Saxifraga flowering in the open air
_ he observed beetles (Haliica, small Staphylinee), flies, and especially
bees. He doubts Sprengel’s interpretation of the so-called honey-
e ides (Saftmal), for though present in some Saxifrages they
‘ re absent in others. In plants whose honey varies between
ully exposed and hidden situations, such a fluctuation of the
: Bate marks is very natural, and rather strengthens Sprengel’s
Cory.
In my Alpendlumen I have tried to prove that those species of
axifraga which have dotted petals show all transitions from mere
: eament by which insects are attracted to ornamentation which
arves also as a “ pathfinder.”’
The proterandrous flowers of S. aizoides, L., and S. oppositifolia,
| L,, are figured by Axell (17).
| Saxifraga sarmentosa, L. fil., has asymmetrical flowers (Todd,
| 722). . ,
_ Of the numerous Alpine species of Saxifraga, I have examined
and figured thirteen. All show, more or less distinctly, the
seculiarity that the anthers ripen one after another; at the same
iP

|
|
f

1 “** Monographie der Gattung Saxifraga,” p. 26. Breslau, 1872.
R 2

244 THE FERTILISATION OF FLOWERS. [PART IIT.

time they bend in towards the centre of the flower, but after
dehiscing they again move outwards. This peculiarity was known
to Treviranus, but was explained by him as aiding self-fertilisation
(742). ‘On the contrary it aids cross-fertilisation, by causing the
insect-visitors to come in contact with the pollen-dusted anthers.
In most of the species of Saxifraga which I have investigated
(S. rotundifolia, L., S. stellaris, L., S. aspera, DC., 8S. bryoides,
L. = S. aspera, var. B, S. aizoides, L., 8S. Aizodn, Jacq., S. coesia, L.,

Fic. 79.—Sawifraga Seguieri, Spreng.
A.—Flower, in first (female) stage, seen obliquely from above. The stigmas are mature. Anthers,

.

petals, and sepals are still far from their full size. 3 5
B.—Flower, at commencement of second (male) stage. The stigmas are shrivelled at the tip
the anthers are all still closed. (a’ dehisced while the drawing was being made.) ;
C.—Flower, at the beginning of the second half of the second (male) stage. The five oute
anthers are already empty; of the five inner, a has dehisced, and a? is in the act of dehiscing
The stigmas are entirely shrivelled up. .
D.—A still older flower. Of the five inner anthers three are still covered with pollen, one i
still closed.
E.—Section of flower in second stage. (x 7.)

S. exarata, Vill., S. stenopetala, Gaud.), the stigma only ripens ¢
the anthers have withered. Engler thought that this was the es
in all the species, but S. oppositifolia, L., and also S. tridactyli
L., a lowland species, are only feebly proterandrous in certe
localities, and in others are feebly proterogynous ; and three species,
S. androsacea, I, S. muscoides, Wulf., and S. Seguieri, Spr., I have:
found tio be everywhere distinctly proterogynous, only the first of the
three being able in case of need to fertilise itself.
As in diecious entomophilous plants the male flowers

pPART ut| = THE MECHANISMS OF FLOWERS. 245

usually larger and more conspicuous than the female, so in the
Y three distinctly proterogynous species of Saxifraga, the: flowers
while in their male stage are more than twice as large as they were

at first while in their female stage. As Sprengel “supposed, it is
i; probable that many insects are thus induced to visit the male
flowers first, and then, having dusted themselves with pollen, to
proceed to the female flowers and fertilise them. The annexed
- figure may serve to show this distinction between the flowers in
their male and female stages.
The honey is quite visible in the above-named species of
| Sawifraga, except S. oppositifolia. Very various short-lipped
insects, but especially flies, serve therefore as fertilising agents.
To the selective influence of flies, therefore, the development of
_ the ordinary colours—white, dull-yellow, white with yellow or purple
spots—must be mainly ascribed. In particular, the prettily dotted
petals of S. rotundifolia and S. umbrosa, L., seem to be due to the
nfluence of certain elegant and prettily coloured Syrphide by which
they are especially visited and cross-fertilised (S. rotundifolia by
— Sphegina clunipes and Pelecocera sccevoides; S. umbrosa by Ascia
podagrica).
| _— Saxifraga aizoides, L., with its large golden flowers dotted with
_ orange, is the most conspicuous form, and attracts most insect-visitors.
I have found it to be visited by 126 species of insects (Coleoptera,
; Diptera, 85; Hymenoptera, 20; Lepidoptera, 13). (609.)
The honey is most deeply placed in S. oppositifolia ; the flowers
_of this species are diligently and persistently visited by butter-
flies and are arrayed in carmine or purple, the favourite colour
_ of most of these insects.!

5
h
q
5

3
;

155. CHRYSOSPLENIUM ALTERNIFOLIUM, L.—The flowers have
a great superficial likeness to the apical flowers of -Adoza, and
are visited by a very similar set of tiny insects.

From the middle of the flower the two styles stretch, diverging
and bending outwards slightly, capped at the apex by the smooth,
capitate stigmas, and surrounded at the base by a broad, fleshy,
yellowish disk, secreting numerous minute drops of honey. At
_ the edge of this disk the calyx, which coalesces below with the
_ ovary, expands horizontally into four broad rounded sepals, bright
_ yellow, and slightly recurved. There is no trace of petals. Be-
_ tween each pair of sepals, and also facing each one, there stands on
the edge of the disk a stamen, erect, and reaching as high as the

1 609, Figs. 26-38 ; in connection with S. wmbrosa, see 604.

246 THE FERTILISATION OF FLOWERS. [PART IIL,

styles. First the four outer ones, which stand opposite the sepals,
ripen one after the other, and then the other four. All the stamens
dehisce on both sides, and flap open so widely that they are covered
almost all round and also above with pollen. The stigmas are
susceptible of fertilisation during the whole time of flowering. A
number of such flowers, from five to upwards of a dozen, are closely
packed in an almost level cyme, and, together with the broad green
bracts that lie nearly in the same plane, form a conspicuous expanse
with a golden-yellow centre.

Numerous minute insects of different orders are attracted.
Most of them touch a stigma with one part of their body, and with
another one or more of the anthers; and so cross-fertilisation is
promoted. But self-fertilisation is not unfrequently induced by the

tiny guests that creep irregularly about the flower. In default of —

insect-visits, self-fertilisation can only take place in a perpendicu-
lar or nearly perpendicular position of the flowers; fur ouly then
can pollen fall.upon the stigmas. On April 13, 1872, I collected
forty-six insects upon flowers growing in the shade.

A. Diptera—(a) Muscide: (1) Five specimens of Sciomyza cinerella,
Fallen ; (b) Simulide: (2) Simulia sp., three specimens ; (c) Cecidomyide :
(3) Six specimens ; (d) Mycetophilide : (4) Five specimens ; (e) Chironomide :
(5) Three specimens, besides minute species. B. Hymenoptera—(a) Formi-
cide: (6) Lasius niger, L. §, eight specimens; (7) Myrmica ruginodis,
N. & (t), two specimens; (8) M. levinodis, N. %, three specimens; (d)
Cynipide : (9) Eucoila, Westw. (Cothonaspis, Hart.), one specimen. C. Cole-
optera—(a) Phalacride : (10) Olibrus zeneus, F. one specimen ; (b) Lathridii :

(11) Corticaria gibbosa, Hbst., two specimens ; (c) Curculionide: (12) Apion —

varipes, Germ., four specimens ; (13) A. onopordi, K., three specimens ; all the
visitors were licking honey.

Also, I found small snails (young Succinee) upon many flowers, —
either creeping about, or devouring the stigmas or anthers. In the

slimy matter left upon the flowers, pollen-grains could as a rule be
recognised : in several cases I could distinctly see that pollen was
placed upon a stigma by help of the snails.

Now if, under some changed conditions, insect-visits altogether
failed, it would obviously be of advantage to the plant to have
cross-fertilisation promoted by the snails, at least on the supposition
that by new modifications the ravages of the snails should ke
obviated. This example may explain the origin of such a floral
arrangement as Delpino observed in Alocasia odora and Rhodea
japonica. And so the doubt which I formerly published concerning
the truth of Delpino’s theory is now removed,

/ > 90> uel sme tall

cparrim.] THE MECHANISMS OF FLOWERS. 247

Chrysosplenium oppositifolium, L., is proterogynous with per-
sistent stigmas (78).

156. BerGENIA (SAXIFRAGA) CRASSIFOLIA, L.—I saw (April 4,
1868) hive-bees and Bombus hortorum, L. ¢, greedily sucking
honey on this plant, and found pollen on the stigmas of several |
flowers whose anthers were not yet open.

157. PARNASSIA PALUSTRIS, L.—Sprengel described very fully
the structure of this plant, but remained in doubt not only as to

Fia. 80.—Parnassia palustris, L.

_ A,—Flower, seen from above, after removal of three sepals and four petals. The flower had just
opened. One stamen has risen up and placed its anther on the centre of the pistil, whose stigmas
et yet nature; the anther is on the point of dehiscing, and will cover its upper surface with
polien,.

B.—-Essential organs of a flower, in which four stamens have shed their pollen; the fifth lies,
covered with pollen, upon the pistil. The stigmas are not yet developed.

C.—Essential organs of a flower in the second (female) condition. (A—C, x 54.)

D.—A staminode, more magnified.

ildebrand has observed Helophilus floreus, L., wpon its flowers.
The anthers before maturity lie close upon the conical ovary,
which rises up in the middle of the flower and overtops them ;
they ripen slowly one after the other, each in turn elongating till
it brings its anther immediately over the end of the pistil, and
then dehiscing on the upper surface. It afterwards bends outwards
_and is succeeded by another, and finally, when all the anthers have
dehisced and moved away, the stigma becomes developed.
The curious nectaries stand immediately opposite to the petals,
alternating with the stamens. Each consists of a short, broad
peduncle, broadening above into a fleshy disk, which secretes

248 THE FERTILISATION OF FLOWERS. [PART ITI.

honey in two shallow depressions on its inner side, leaving it
fully exposed. Above it gives off seven to eighteen yellow, knobbed,
glandular bodies, which surround the upper portion of the ovary
and are probably of service in making the nectaries more obvious
to flies which alight in the middle of the flower. |

These yellow knobs placed at the ends of the hairs look so
exceedingly like drops of fluid that it needs special examination
to convince one that they are perfectly dry. An observation of
my son Hermann’s proves that even flies are deceived by this
appearance ; he observed from a very short distance a specimen
of Eristalis nemorum trying to lick these bodies for a long time,
until at last it flew away on his coming closer.

We have thus in Parnassia palustris a very well-marked
example of a deceptive flower, which deludes the foolish flies by
displaying a multitude of conspicuous but sham drops of honey ;
and which, after thus alluring them, affords them indeed some
easily accessible honey, which repays their trouble but is quite
incommensurate with the apparently bountiful display. The
smaller flies generally travel round the flower, to reach all the
nectaries ; the larger ones rest in the middle of the flower for this
purpose, and so dust their under sides with pollen in younger
flowers and accomplish cross-fertilisation on passing to older ones.

Visitors: A. Diptera—(a) Syrphide: (1) Eristalis nemorum, L., s. ab. ;

(2) E. arbustorum, L., s. ab. ; (3) Helophilus floreus, L., s. ab. ; (4) Syrphus ;

ribesii, L., s. ab. ; (5) S. balteatus, Deg., very ab., s.,{sometimes f.p.: (6) S.
pyrastri, L. ab. s.; (7) 8. excisus, Zett, s.; (8) Melanostoma mellina, L., s. ;
(9) Melithreptus scriptus, L., s.; (10) M. menthastri, L., s. ; (11) M. teeniatus,

Mgn., s.; (12) Syritta pipiens, L., ab. s.; (b) Muscide: (18) Sarcophaga —
earnaria, L., s.; (14) Pollenia vespillo, F., s.; (c) Tipulide: (15) Tipula —

oleracea, L. B. Hymenoptera—(a) Tenthredinide : (16) Tenthredo sp., s. ;

(b) Ichneumonide : (17) Many small species, s. ; (c) Sphegide: (18) Pompilus —
viaticus, L.; (19) Gorytes campestris, L, C. Coleoptera—(20) Coccinella —

7-punctata, L. ; (21) C. 14-punctata, L., both very ab., 1h. A list of Alpine
visitors (including 43 Diptera) is given in No. 609.

Tribe Hydrangee.

Philadelphus coronarius, L., is proterogynous. When the flower —

opens the stigmas are already ripe, but the stamens still immature.

In weather favourable for insect-visits, it is easy to find flowers —
whose anthers are still closed but whose stigmas are sprinkled —

with pollen. The numerous anthers stand, both before and after
dehiscence, close round the stigma, some on a level with it, some
higher, some lower; the outermost dehisce first, the innermost
last ; all cover themselves all round with pollen. Honey is secreted

——>

> Seam
SS Vite

Joint lyn Yemege- -

w

partim.| § THE MECHANISMS OF FLOWERS. 249

by a white, fleshy disk on the upper surface of the ovary. Insect-
visitors, collecting or feeding on pollen or thrusting their heads
_ down between the stamens towards the honey, can thus lead to
_ cross-fertilisation only in young flowers, but in old ones cross-
fertilisation and self-fertilisation are alike possible. In absence of
insects, self-fertilisation may easily take place, for the stigmas
stand partly in the line of fall of the pollen. But the honey, only
hidden by the stamens, is accessible to so many insects, and the
white colour and strong scent are such powerful attractions, that in
fine weather insect-visits can seldom fail.

Tribe Ribesien.
_ 158. Rises ALpinuM, L.—This species presents its honey in a
shallower depression than any of our other species of Ribes, so

Fic. 81.—Ribes alpinum, L.

1.—Female flower, from above,

2.—Ditto, in section.

3.—Male flower, in section.

a’, rudimentary anthers ; st’, rudimentary stigma; n, nectary.

' that it is easily accessible to very various insects, and is con-
| sequently visited by the most manifold forms. Although I only
had an opportunity of watching a few plants in a hedge, I saw
upon their flowers the following :

\q = A. Hymenoptera—A pide : (1) Andrena albicans, K. 9 ¢, s. and f.p., very
~ ab.; (2) A. Gwynana, K. ¢,s.; (8) A. nana, K. ¢,s. ; (4) Halictus nitidus,
| Schenck, ?, s.; (5) H. nitidiusculus, K. ?,¢.p.; (6) Sphecodes gibbus, L.
' 9, s. B. Diptera—(a) Muscide: (7) Scatophaga ‘stercoraria, L.; (8) S.
merdaria, F.; (b) Syrphide: (9) Syritta pipiens, L., all three ab., s.

: Upon this abundance of insect-visits, which insures cross-
fertilisation, depends the dicecism, evolved from a previous
_ hermaphroditism and still showing traces thereof, which would
\ of necessity be fatal in default of insect-visits. The male flowers
are of scarcely larger size, but their greenish-yellow colour is
) more conspicuous than the green female flowers. The calyx
| almost alone plays the part of signal to the insects. |

250 THE FERTILISATION OF FLOWERS. © [parr ill.

159. Rrpes nigrum, L.—The stigma and anthers are both —

alike ripe at the opening of the flowers. The anthers open on the

inner side, and are brought so close to the stigma by the conver- —

gence of the petals that an insect’s head, when pushed into the
flower, must touch with one side the pollen-dusted face of one or
two anthers, and with the other, at the same time
or a little before, the slightly protruding stigma.
Since the bell-shaped calyx, whose floor secretes
honey, is 5 mm. deep, and the red tips of the
sepals and the small white petals make the pendu-
lous flowers only slightly conspicuous, insect-visits
are not plentiful: I have only seen the honey-
bee sucking at this species. It put its head only
once into each flower, and touched the stigma now
on the upper side, now on the lower, sweeping
away pollen each time on the opposite side and so regularly ac-
complishing cross-fertilisation. As compensation for the paucity of
insect-visits, self-fertilisation takes place regularly in unvisited

Fic. 82.—Ribes nigrum,
L.

Lateral view of flower.

flowers, pollen falling of itself out of the anthers upon the recurved

margin of the stigma.

160. RIBES RUBRUM, L., is likewise homogamic, but has much

flatter, more widely open, and more conspicuous flowers than
R. nigrum, and more easily accessible honey. So it is more
abundantly visited by insects, and is cross-fertilised after the same

manner as &. nigrum but is self-fertilised less easily; the flowers —
are turned sideways, and self-fertilisation only takes place when ~
pollen falls upon the stigma from the anthers above it. I have

seen the following insects upon the flowers :—
Hymenoptera—(a) Apidae; Andrena fulva, Schrank, ?, s. and ¢.p., freq. ;

(2) A. Smithella, K. ¢, s.; (3) A. nana, K. ¢, s.; (4) Apis mellifica, L., ~

%, 8. and cp., ab. ; (b) Tenthredinide: (5) Nematus hortensis, Htg,, s.

161. Rises GrossuLariA, L.—The anthers dehisce when

the flower opens: the styles have not as yet attained their full

length, nor have the stigmas developed their papillae. Since the
flowers mostly hang down perpendicularly and the stamens stand
around, and on a level with, the stigmas, self-fertilisation can as a-

rule not take place, even in default of insect-visits. This, like the

proterandry, points to more numerous insect-visits than the former —

species receives ; and these really take place, induced by the large
recurved sepals, the large, perpendicular, downward-pointing petals,
and the easily accessible honey.

|
:

PART IIL. | THE MECHANISMS OF FLOWERS. 251

Visitors: A. Hymenoptera—Apidew: (1) Bombus terrestris, L. 2, freq. ;
(2) B. pratorum, L. ? (in Stromberg), very ab. ; (3) B. Scrimshiranus, K. 9 ;

_ (4) Apis mellifica, L. $, very ab. ; (5) Andrena nitida, K. ¢, all sucking ;
| (6) A. albicans, K. ¢ 2; (7) A. Gwynana, K. ¢ 9; (8) A. fulva, Schrank,
_ 9, the last three both s. and f.p.; (9) Halictus rubicundus, Chr. 9,s._ B.
Diptera—(a) Muscide: (10) Scatophaga stercoraria, L., s. ; (11) Calliphora
erythrocephala, Mgn., s. ; (b) Syrphide: (12) Eristalis eneus, L., s. and f.p. ;
(13) Syritta pipiens, L., do. The insect-visitors cause cross-fertilisation in the
same way asin R. nigrum. See also No. 590, I.

_ —

Ribes sanguineum, Pursh.—The calyx-tube is 3 mm. deep; the
erect petals form a tube more than 5 mm. deep. As a rule, there-
fore, the honey is obtained and the Rowers fertilised by bees only,
especially the hive-bee.
ftibes aurewm, Pursh—The calyx-tube is 10 to 11 mm. deep,
and the erect petals add 3 mm. more to its depth. The honey is
only accessible to very long-tongued bees, and the flowers have been
found by Delpino in Italy and by me in Lippstadt to be visited
only by Anthophora pilipes, 2? , whose proboscis is the longest among
our native bees (20 mm.). In the two last species the flowers
persist a long time after the reproductive organs are withered, and
even become more conspicuous, since the petals in 2. sanguinewm
change from white to pink, and those of &. awrewm from bright
yellow to carmine. By this peculiarity, not only is the power of
attracting insects increased, but the more intelligent fertilising
_ agents are told at the first glance which flowers contain no more
. treasure for them, the result being that they visit and fertilise more
_ flowers in the same time (590, I.). The same kind of colour-change
/ occurs in several species of Fuchsia and Lantana, in Diervilla
(Weigelia) rosea, Melampyrum pratense, L., Fumaria capreolata, var.
| pallidiflora, Jord., and others (575).
= kttbes petreum, Wulf., is, according to Ricca, slightly pro-
terogynous (665); according to my own observations it is
_ homogamic (609).

Hk cera LE LOE TE EET GP DO NAO A Fa

Orv. CRASSULACE Z.

Bryophyllum calycinum, Salisb., is proterandrous, and has hang-
g, tubular flowers, rich in honey. Delpino supposes humming-birds
be the fertilisers, despite the pale greenish colour (177).

4 162. SepuM AcRE, L.—Although the plant is small, it is
i endered conspicuous on the bare spots where it grows by its

252 THE FERTILISATION OF FLOWERS. [PART III.

bright yellow flowers, and dense tufted habit. The flowers secrete
honey from five yellowish scales at the base of the flower, lying
between the anthers and carpels. The honey is accessible to —
insects with very short tongues, and the flowers are visited by
numerous species of different orders. Cross-fertilisation for the
most part takes place. For when the flowers open, and their —
petals spread fully out into a five-rayed star, the five stamens
which alternate with the petals and which stand erect round the
middle of the flower now dehisce ; while the five others which are —
inclined outwards with the petals remain closed: the stigmas are
still quite immature. As the first five stamens wither, the others ©
rise up towards the centre and open; very soon, even before this ©

Fic. 88.—Sedum acre, li.

i 1.—Flower, in first stage. 8, sepals; p, petals; a*, outer anthers, alternating with the petals a

a’, inner anthers, opposite the petals; n, nectaries; ov, ovaries.
2.—Apex of a style, in first stage. .

8.—Ditto, in second stage, after all the anthers have dehisced.

second ring of stamens withers, the stigmas ripen. By sufficient _
insect-visits, which in sunny weather never fail, the pollen is
wholly, or in great part, removed before the stigmas are capable
of being fertilised. If, however, in dull, windy weather, insect-_
visits are lacking, the anthers remain stored with pollen until the
full ripening of the stigmas, and self-fertilisation becomes possible.
Since the flowers are small compared with the insects, the latter

of the flower or creep inwards from the edge. ‘

Visitors: A, Hymenoptera—(a) Apidae : (1) Bombus Rajellus, K. $ ; (2)
Cilissa tricincta, K. 9; (8) Andrena cingulata, K. 9 ; (4) A. parvula, K. 2 ¢,

art ut) THE MECHANISMS OF FLOWERS. 253

ab. ; (5) Sphecodes gibbus, L. 9, freq. ; (6) Nomada ferruginata, K. 9 ; (7)
Prosopis armillata, Nyl. 2, ab. ; (8) Pr. variegata, F. ¢; (9) Pr. brevicornis,
Nyl. ¢ ; (10) Megachile circumcincta, K. 2, all sucking ; (11) M. centuncularis,
‘L. 2, «p.; (b) Sphegide: (12) Ammophila sabulosa, L.; (13) Oxybelus
uniglumis, L., ab., both sucking. B. Diptera—(a) Syrphide: (14) Eristalis
tenax, L., fp. ; (b) Muscide : (15) Pyrellia wnea, Zett., s.

163. SEDUM REFLEXUM, L., with a similar arrangement of its
flowers, is in like manner visited by insects of various orders.

I saw upon its flowers: (1) Megachile maritima, K. ¢ (Apide), sucking ;
(2) Eristalis tenax, L. (Syrphide), both sucking and eating pollen. A further
list is given in No. 590, 1.

Sedum album, L.—This species is so decidedly proterandrous,
i that spontaneous self-fertilisation as a rule can scarcely result even
in default of insect-visits. I have found the plant visited abun-
dantly by insects, both on the granite of Luisenberg in the Fichtel-
gebirge (590, I.) and in the subalpine region of the Alps (690).

- 164, Szepum TELEPHIUM, L.—The stamens dehisce introrsely,
first the five alternating with the petals, and then the inner series,
and at once cover themselves all round with pollen. The stigmatic

Fic, 84.—Sedum Telephium, L.

1.—Flower, from above.
_2.—Ditto, after removal of the pistil, to show the five nectaries.

_ papillse develop upon the pointed ends of the styles, after the last
Stamens have withered. Since the petals and stamens are spread
_ out as widely as the adjacent flowers permit, self-fertilisation does
10t take place in default of insect-visits, even when the anthers
re still stored with pollen at the ripening of the stigmas.

_ The honey-glands are at the points of long scales hidden under
he ovaries, at the bases of the petals. Insects which creep oyer

—-

254 THE FERTILISATION OF FLOWERS. [parr im.

the closely packed flowers, to suck honey or gather pollen, come at
once in contact with the stamens or stigmas of many flowers, and,
as a rule accomplish cross-fertilisation by help of the proterandrous
condition : old flowers alone, which retain some pollen upon their
stamens when the stigmas are ripe, are liable to self-fertilisation.

In spite of the smaller flowers and more hidden honey, this

species can dispense with the possibility of self-fertilisation, since
the close association of many flowers insures insect-visits and con- —
sequent distribution of pollen more completely than is the case

in Sedum acre. Although I only once watched the flowers of
Sedum Telephium (August 16, 1869) in sunny weather I saw the

following insects visit it :—

A. Hymenoptera—(a) Apide: (1) Bombus (Apathus) campestris, Pz. ¢;_

(2) B. silvarum, L. 9 §, freq. ; (3) B. agrorum, F. ¢, these three sucking ;
(4) B. lapidarius, L. $,¢.p.; (5) Halictus zonulus, Sm. 9, s. ; (b) Tenthre-

dinide: (6) Allantus notha, Kl. (Tekl. B.). B. Diptera—Muscide : (7) _

Echinomyia magnicornis, Zett., s.

Sedum atratum, L., is, according to Ricca, proterogynous with
short-lived stigmas (665). I have found it, however, on the
Alps to be likewise proterogynous, but liable to regular and even
early spontaneous self-fertilisation, which is probably indispensable,
as the plant is but little visited by insects (609).

Sedum repens, Schleich.—This species also is proterogynous on
the Alps, and in the absence of insects it likewise fertilises itself;
but its flowers are rather conspicuous and more visited by insects,
so that the need for self-fertilisation is less urgent than in the
case of S. atratwm (600).

THE COLOUR AND SIZE OF THE FLOWER IN CRASSULACEZ,

The colour of the flower in Crassulaceze depends closely upon
the adaptation of the flower to a narrow or wide circle of visitors.
In the species of Sedum, whose honey is still quite visible and
accessible to the most short-lipped insects, the flowers are greenish-
yellow, yellow, or white; in Sempervivum Funkii, Braun., S.
montanum, L., S. arachnoideum, L., and 8S. tectorwm, L., whose
honey lies hidden, and which I have seen visited on the Alps by a
miscellaneous company of bees, Lepidoptera, and long-tongued flies,
the flowers are purple; in Sempervivum Wulfenii, Hopp., whose
honey is still more concealed, the flowers, which are chiefly visited

wut] THE MECHANISMS OF FLOWERS. 255

by humble-bees, are sulphur-yellow, and only remain purple at the
base. I say only remain purple at the base, because this colouring
is now useless, and seems only explicable as a remnant inherited
from purple-flowered ancestors. The sulphur-yellow colour of
empervivum Wulfenii seems not to stand on the same rank as the
yellow colour of some Sedums; but rather to have been developed
from a purple colour by the selective influence of humble-bees.
In connection with the size of the flower, we see in many
Crassulaceze the number of the parts increased or decreased :
increased in Sedum from 5 to 7, in Sempervivum arachnoideum
to 9—11, in S. montanum to 9—12, in 8. Funkii to 10—13, in S.
ectorum to 11—13, in S. Wulfenii to 13—16; decreased in
x Re iliarda, DC., to 4, in Tillwa, L., to 3 (609).

Orv. DROSERACEZ.

Drosera, L., occurs with cleistogamic flowers (169).

Orv. HALORAGE.

——s- Callitriche verna, L.—The proterogynous flowers are figured by
Axell (17). Axell considers them to be anemophilous; Ludwig

le ooks upon the submerged flowers as hydrophilous, and the others

as entomophilous (435).

— Myriophyllwm spicatum is anemophilous, and I. verticillatum is

partly anemophilous and partly hydrophilous, according to Ludwig

(435).

Orv. COMBRETACE &.

— Combretum, L., is very diligently visited by humming-birds in
South Brazil (Fritz Miiller, 359). My brother informs me by letter
that it is also frequented by butterflies (Callidryas).

Orv. MELASTOMACEL,

_ Heeria, Schlecht., has: two kinds of stamens, one serving,
apparently, to attract the fertilising-agents, and the other supplying
_ the pollen for cross-fertilisation (606).

Orv. LYTHRARIEL.

165. LyTarum SanicartA, L.—This plant has acquired, through
Darwin’s numerous and laborious experiments (158), so important

256 THE FERTILISATION OF FLOWERS. [parr ur. —

a place in the question of the origin of species, that its fertilisation

by insects in the wild state also deserves our special attention. I
shall recapitulate first the peculiarities of its flower, next the results —
of Darwin’s experiments, and finally the insect-visitors that I have —

observed.

The flowers, which are set in close whorls on a long spike, are
almost regular, usually hexamerous but sometimes pentamerous, —
both forms occurring on the same spike ; they have lost something
of their regularity by standing not quite horizontally but directed

slightly upwards. Of the five or six petals which are inserted on

the edge of the cylindrical calyx-tube, 5 to 7 mm. long, the three

lower (outer) are usually a little longer than the two or three

Fig. 85.—Lythrum Salicaria, L.

. —Long-styled flower from above, after removal of one-third of the calyx, corolla, and stamens. —

2.—Mid-styled flower, ditto.
3.—S8hort-styled flower, ditto.

a, long anthers or stigma; the stigma in Fig. 1, the anthers in 2 and 3 are coated with

green pollen.
b, mid-sized ditto; the stigma in Fig. 2, the anthers in 1 and 3 are coated with yellow

pollen.

ce, short ditto; the stigma in Fig. 8, the anthers in 1 and 2 are coated with yellow pollen. —

d, honey
4,—Mid- styled aout. viewed obliquely from above and frou the right side.

upper ones; the former are 7 to 11 mm. long, the latter 6 to 10 mm.
When the flower is fully expanded, as, owing to the crowded
arrangement, it seldom is, the upper petals stand vertically while
the lower project obliquely forward; and the latter form, therefore,
a rudimentary platform for insects. The irregularity in position of
the stamens and pistil is of more importance; they all occupy the
inferior (outer) part of the tube, so that insects cannot reach the
base of the flower between them, but only above them ; and their

ends are bent upwards, so that the ventral surface of the insect

Ce ee ee ee

— ee ee

must come in contact both with anthers and stigma. Honey is —

secreted by the fleshy base of the flower, and surrounds the short

}

PART III. | THE MECHANISMS OF FLOWERS. 257

stalk of the ovary and fills the space between it and the sides of the
tube. Insects are attracted from a distance by the crimson spikes
of flowers, and are guided on their way to the honey by the dark
red colour of the inner surface of the calyx and by the dark lines
in the middle of each petal. These insects are caused to perform
_ regular cross-fertilisation by the trimerphism of the flowers, which
forms the most remarkable feature of the plant.
In each flower the reproductive organs, which consist of one pistil
and two whorls of stamens, of five or six each, are of three different
i lengths ; the shortest are inclosed in the calyx-tube, the intermediate
ones project 3 to 4 mm., and the longest 6 to 8 mm. beyond it, and
either the style or one or other whorl of stamens may be the longest.
_ All the flowers on any one plant are of the same kind, and the three
forms are designated by Darwin, the Long-styled, Mid-styled, and
ie Short-styled. Both pollen-grains and stigmatic papille differ
according to the length of the organs which bear them. All the
pollen-grains are elliptical when dry, and swell into a spherical form
when moistened. The pollen-grains of the longest stamens are
_ green, those from the middle-sized and shortest stamens are yellow.
he pollen-grains vary in size also according to the length of the
stamen that they come from, and there is even a slight difference
in size between pollen-grains from stamens of the same length but
belonging to flowers of different kinds. The following table exhibits
| these differences :—

} | Size of dry pollen-grains | Diameter of
ee el ee ee
Length. Breadth. | in 335 mm.
Long-styled . | Intermediate. | 74—84 4—4} 7—74 | Yellow. |
| Long-styled . | Short . 1—74 34—4 6—64 | Yellow.
| Mid-styled . | Long . 9—10 6—7 9—10 | Green. |
_| Mid-styled . | Short . 6—7 34—4 6 Yellow.
' | Short-styled . | Long . 10—11 6—8 94—104 | Green.
| Short-styled . Intermediate. 7—8 4—5 7—74 | Yellow.

So the longest stamens have the largést pollen-grains, and the
hortest the smallest.

: The pollen-grains of the long stamens differ more from those of
e middle-sized and short stamens than these from each other.
The stigmatic papille in the long-styled forms are considerably
) longer and have their free ends farther apart than those in the
| eo tyled and short-styled forms, which in this respect also do not
S

258 THE FERTILISATION OF FLOWERS. [PART IIL.

differ so much from each other. In all these forms the stigmatic
papille consist of long cells, whose ends are cut off as round or
elliptical knobs by a narrow neck. In the long-styled flowers these _
cells are 49-9 mm. long, and as the part below the constriction is —
about twice as thick as the knob above, these knobs stand at a
distance from each other equal at least to their own diameter. In~
the mid-styled form these papillze are only *f,%° mm., and in the
short- styled 25-45 mm. long; and in both, the knobs stand very near
together, since the part of the cell below the constriction is little
thicker than that above.

Now it was Darwin’s great service to prove beyond question, |
by a long series of patient experiments, that in Lythrum Salicaria —
reproductive organs, when of different length, behave to one another
like different species of the same genus in regard both to direct
productiveness and the character of the olipeind: and that con- —
sequently mutual barrenness, which was once thought conclusive
proof of difference of species, is worthless as such, and the last —
barrier that was raised between species and varieties is broken —
down. |

Now of the eighteen possible ways of fertilisation —applyail
the six different kinds of pollen to the three kinds of stigmas,—
those six only are fully productive in which a stigma receives
pollen from a stamen of equal height. The probability that the
large pollen-grains from the long stamens are only suited to the
long, widely separate papille on the long styles (and so forth in che
other cases) is thus fully confirmed by experiment. But such ¢
adaptation, such a differentiation of the sexual parts, is only
intelligible if it can be shown that under natural conditions insect-
fertilisation causes the distribution of pollen to the proper stigmasy,
and it is clearly proved by observation that this is so,

The honey of Lythrum Salicaria, inclosed at the base of a tube
5 to 7 mm. long, is accessible (1) to insects which have a proboscis
5 to 7 mm. long; and (2), since the entrance to the tube is 23 to
3 mm. wide, to insects whose head is small enough to be thrust
partly or entirely into the tube ; and (3) to insects small enough to
creep down to the base of the flower. 4

Almost every insect, whose body along with its proboscis is at
least 12 to 15 mm. long, must in sucking the honey touch the
shortest organs with its proboscis, or, if this is less than 5 to 7 mm. -
long, with the under side of its head ; the next series with a part of
its ventral surface 4 to 5 mm. Gorkher back, and the third seri
with another part of its ventral surface the same distance behind

parrut}] .THE MECHANISMS OF FLOWERS. 259

the last. Thus all the three kinds of stigmas will tend in time to
"receive pollen from stamens of their own length. If the middle-
sized and longest organs were also inclosed within the tube, the
| proboscis or head of the insect in passing down would come in
contact with all, one after the other, and cross-fertilisation could not

"be e nearly so well restricted to its proper lines. In point of fact, the
insect alighting on the middle-sized and longest organs never has

_ occasion to touch these with its proboscis or the fore-part of its
ventral surface, the parts that are to come in contact with the
shortest organs; nor is the posterior part of the ventral surface
which has been in contact with the longest organs, ever brought
forward during the process of sucking to touch the intermediate
ones. So that, as a rule, “ legitimate crossing” only is performed.

In the action just described, which leads regularly to legitimate
© ossing, only the larger and middle-sized bees and the eee flies
take part.

_ I have observed : (1) Cilissa melanura, Nyl. ¢ and 9, wherever Lythrum
Salicaria grows, both sucking honey and gathering pollen, and almost confining
‘itself to this one plant. (Since its proboscis is only 3—4 mm. long, it must thrust
Beret part of its head, which is 2—3 mm. broad, into the tube : it then touches
the shortest reproductive organs with the under surface of its head, the next
_ with the ventral surface of its thorax, and the longest with the ventral surface
_ of its abdomen ; so that its dimensions suit the flower, just as well as the flower
' must suit it, for the insect to confine its visits so exclusively to it. I have only
found one exception to this exclusiveness, for I once found a male of Cilissa
melanura sucking honey on Thrincia hirta, D.C.) ; (2) Saropoda rotundata, Pz.
; 3) frequently (body without proboscis 10—1I mm., proboscis 9 mm. long) ;
3) Apis mellifica, L. § (body without proboscis 1I—13 mm., proboscis 6 mm.
long) ; (4) Bombus terrestris, L. § (body 12—16 mm. S seoboseis 7—9 mm. ); (5)
'B. agrorum, F. § (body 10—13 mm., proboscis 9—11 mm.) ; (6) B. silvarum,
. § (body 10—12 mm., proboscis 10—12 mm.). All the humble-bees were
1 equent, and, like Nos. 2 and 3, sucking honey only ; (7) Megachile centun-
ew aris, L. ¢ (body 10 mm., proboscis 6—7 mm.), also sucking honey. The
ast six species, as the aimexed measurements show, have all. tongues long
| enough to reach the honey by thrusting in the tongue alone ; they all therefore
touched the shortest organs with their tongues, the next series with the lower
' Surface of the head, and the longest with a part of the ventral surface of the
| body 4—5 mm. further back. The hive-bee must, in full-sized flowers, have
arust the extremity of its head 1 mm. deep into the calyx-tube.
__ Besides these bees, which deserve to be placed in the first rank as legitimate
fertilisers, the Loosestrife is visited by a number of long-tongued flies, especially
| Rhingia rostrata. This fly, standing on one or more of the petals, after gently
rubbing its forefeet together, and brushing its tongue and head with them,
stretches its proboscis out to a length of 11—12 mm., and thrusts it down into
the flower, letting it remain there from six to ten sheonls Immediately after
withdrawing it from the tube, it usually manipulates one of the anthers with its
Ss 2

260 THE FERTILISATION OF FLOWERS. [PART III.

labellz for a short time (one to two seconds) in order to add to the liquid
non-nitrogenous food some solid nitrogenous matter in the shape of pollen- —
grains, In inserting its proboscis into the tube, the conical prolongation of
the head comes in contact with the middle-sized reproductive organs, while the
proboscis itself touches the shortest ; the longest organs come at timesin contact _
with the ventral surface of the fly, but very often fail to do so ; and so this fly,
as a rule, only performs two-thirds of the legitimate work of fertilisation.
Two other Syrphide, Helophilus pendulus, L., and H. trivittatus, F. (proboscis.
6—7 mm. long), alight upon the longest reproductive organs, and fertilise all
three kinds of flowers legitimately ; so also does Volucella plumata, L., whose
proboscis is 7—8 mm. long. Several smaller Syrphide, whose proboscis is too
short to reach the honey, viz. Syritta pipiens, L. (proboscis 3 mm.), Syrphus —
balteatus, Deg. (2 mm.), and Melithreptus teniatus, Mgn., feed on the pollen, —
which they may chance to carry to the stigmas; but they are as likely to _
perform illegitimate as legitimate fertilisation. The same holds good of Halictus
eylindricus, F. ¢, which has likewise too short a proboscis to reach the honey,
and only collects pollen on this flower ; and also of some very small insects, _
Nanophyes lythri, F., Meligethes, and Thrips, which creep down into the tube, —
and of a species of Capsus which runs about indiscriminately on the leaves and —
also on the flowers of the plant. Va

Two butterflies also, Rhodocera rhamni, L., and Pieris rape, L., are to be .
seen rather abundantly on the flowers of the Loosestrife. The butterfly, sitting —
upon one flower, thrusts its proboscis (15 mm. long) into the next; it thus —
touches the shortest organs regularly with its proboscis, but seldom the middle- —
sized ones, and the longest scarcely ever, but the middle-sized and longest _
organs of the flower on which it is seated come in contact with the ventral
surface of its body. y

In the following list, those insect-visitors which regularly accomplish cross-—
fertilisation in its three forms are marked with (!) ; those which as a rule only —
effect one or two forms of crossing are printed without special mark ; and
those which only occasionally fertilise the plant, and perform illegitimate ~
as often as legitimate fertilisation, are placed in parentheses.

A. Hymenoptera—Apide : (1) Cilissa melanura, Nyl. $ 9! s. and e.p., ab. 3
(2) Saropoda rotundata, Pz. ¢ 9!s., not rare; (3) Apis mellifica, L. $! s. 3
(4) B. terrestris, L. §!s.; (5) B.agrorum, F. §!s.; (6) B. silvarum, L. $! 5. 5
(7) Megachile centuncularis, L. ¢!s. ; (8) (Halictus minutissimus, K. 2, s.);
(9) (H. eylindricus, F. 2,¢.p.). B. Diptera—Syrphide : (10) Rhingia rostrata,
L,, s. and ¢.p.; (11) Helophilus pendulus, L.!s.; (12) H. trivittatus, F.!s. 5
(13) Volucella plumata, L.!s.; (14) (Syritta pipiens, L., fp.) ; (15) (Syrphus_
balteatus, Deg., f.p.) ; (16) (Melithreptus teeniatus, Mgn., f.p.). C. Lepidoptera”
—Rhopalocera: (17) Rhodocera rhamni, L.,s., ab.; (18) Pieris rape, L.,s., ab,
D. Coleoptera—(a) Curculionidae : (19) (Nanophyes lythri, F.) ; (b) Nitidulide =
(20) (Meligethes). E, Thysanoptera—(21) (Thrips). F, Hemiptera—(22)
(Capsus). See also No. 590, 11. .

* 7

Lythrum Graeffert, Ten., is, like Z. Salicaria, trimorphic; DL.
thymifolia, L., is dimorphic, and L. hyssopifolia, L., homomorphie
(Darwin, No, 154).

Besides Lythrum, Nesea, Commers., and Lagerstremia, L., have

anti] § THE MECHANISMS OF FLOWERS. 261

trimorphic species ; Pemphis, Forst., has dimorphic species (Kuhn,
No. 399, Darwin, No. 167, 2nd ed.). Koehne’ mentions twenty-one
_heterostylic and 340 homostylic species of Lythrum ; according to
him, L. thymifolia is not heterostylic (394). Pemphis acidula,
Forst., and some species of Rotala,» L., and Neswa are clearly
heterostylic and dimorphic.

Amimannia latifolia, L., has cleistogamic flowers (394).

_ Cuphea silenoides, Nees, C. floribunda, Lehm., and C. Melvilla
Lindl., according to Treviranus, fertilise themselves before the

ae
) ae

_ flower opens (742).
Ord. ONAGRARIE &£.

166. EPILOBIUM ANGUSTIFOLIUM, L.—The markedly proter-
r undrous flower was thoroughly discussed by Sprengel, who noticed
humble-bees as its fertilisers. The bright crimson racemes, a foot
long, are very conspicuous, The honey is secreted by the green,
fleshy, upper surface of the ovary, and is easily accessible to insects
and yet well sheltered from rain. The expanded lower ends of the
filaments form a hollow cone, which incloses the base of the style
and the surrounding honey; where the style issues at the apex of
this cone, hairs upon the style prevent the entrance of raindrops,
while insects easily gain access between the filaments.
In young flowers the stamens, covered above with pollen, project
| forwards as an alighting-place for insects, while the style is still
short and bent downwards, with its stigmas folded together ; in older
| flowers, the empty stamens are bent downwards, and the style,
' greatly increased in length, projects forwards with its four stigmas
outspread and recurved. Alighting, sucking, and pollen-collecting
are thus all made easy, cross-fertilisation in case of insects-visits is
insured, and self-fertilisation rendered impossible. In fine weather,
| sufficient insect-visits are always insured by the conspicuous colour,
/size, and grouping of the flowers, and by the abundance and
/accessible position of the pollen and honey.

: Visitors: A. Hymenoptera—(a) Apide : (1) Apis mellifica, L. $,s., very
b.; (2) Bombus lapidarius, L. 2 $8; (3) B. pratorum, L. 9? $9 4; (4) B.
terrestris, L. 2 § 3; (5) B. confusus, Schenck, ?, all ab., s. ; (6) B. agrorum,
y F 2 & g, very ab.,s.; (7) B. (Apathus) campestris, Pz. ¢, s. ; (8) Sphecodes
‘\gibbus, L. 9, s.; (9) Nomada Roberjeotiana, Pz. 9, s. ; (10) N. Jacobaxe,
z. 3, 8.3 (b) Sphegide: (11) Cerceris nasuta, Latr. ; (12) Crabro alatus, Pz. ;
3) Ammophila sabulosa, L. ; (c) Tenthredinide : (14) Tenthredo scrophularie,
, all sucking. B. Diptera—(a) Empide: (15) Empis rustica, Fallen ;

1 Vide Bentham and Hooker, Genera Plantarwm, i. p. 776.

262. THE FERTILISATION OF FLOWERS. [PART Il

=

(16) E. livida, L., both sucking, abundant; (17) Syrphus ribesii, L., tpl
D. Lepidoptera—Sphinges : (18) Ino statices, L,, s. See also No. 590, IL @ and ;

No. 609.

Epilobium Fleischeri, Hochst. (#. denticulatum, Ulender), 1
visited by numerous humble-bees. It is sometimes homogam a
sometimes proterandrous, sometimes proterogynous, and the short
style always occupies the same position below the stamens. Cross
fertilisation is generally insured, but self-fertilisation is not quite
excluded (No. 609, fig. 82).

Insect-visitors of #. Dodonwi, Vill., #. origanifoliwm, Lam
and FL. montanum, L. (E. collinum, Grek are enumerated in Di

Alpenblumen.

167. EPILOBIUM PARVIFLORUM, Schreber.—In regard to the |
power of attracting insects and the possibility of self-fertilisation, -
two species of the same genus could scarcely stand in greater

jt nt ac ee ee ee

He,

Fic. 86.—Epilobium parvijlorum, Schreber.

Flower, in side view, the greater part of the calyx and ovary and the two anterior petals havit
been removed,
st, stigma; a*, longer stamens; a2, shorter ditto.

contrast to each other than Hpilobium parviflorum and £. ang
tifolium ; for the solitary, pale-red flowers of the former species <
easily overlooked even by the practised eye, and generally expo: se
their honey to no purpose, receiving insect-visits only one
Accordingly self-fertilisation is a regular occurrence. ;

The honey is secreted by the upper surface of the ovary
lodged round the base of the style ; it is sheltered from rain not
so much by the stamens as by a ring of hairs projecting inwe ds
from the petals. Stamens and stigmas ripen together. The for

arti] | THE MECHANISMS OF FLOWERS. 263

shorter stamens are set apart for cross-fertilisation, as they stand
if below the stigmas and are touched without fail by honey-seeking
sects. The stigmas, standing in the centre of the narrow flower,
must be touched first by an insect-visitor. The four longer stamens
are concerned in self-fertilisation, and stand close round the stigmas,
which are provided with long stigmatic papille on their outer as
well as on their inner sides. We must suppose that in case of
nsect-visits the pollen brought from without predominates in its
ction over the pollen belonging to the flower. In spite of frequent
vatching, I have only observed Pieris rape and a Meligethes sucking
1oney on this plant.

168. EPILOBIUM ORIGANIFOLIUM, Lam.—This Alpine species is
— in many respects to E. parviflorum. The flowers are
mall, tubular, and inconspicuous; the style is unbranched, and
tig matic papillee form a uniform covering for its upper end. The
stigma is fully ripe on the opening of the flower, the stamens reach
maturity a little later. The upper whorl of stamens performs self-
ertilisation regularly, while the lower whorl provides for occasional
crossing. Argynnis Pales was observed sucking several flowers.

Epilobium -hirsutum, L.—The flowers of this species, whose
osy corolla expands to a diameter of 25 to 30 mm., are, taken

Fig. 87.—Epilobium hirsutum, L.

ir naly, still more conspicuous than those of EL. angustifoliwm ; but
2 latter is rendered the more conspicuous of the two by the
egation of more numerous flowers. I have had no opportunity
of E ching E. hirsutum in the right places at the right time; but
rom the arrangement of its flowers, as well as from its less striking
ippearance, it is probable that its insect-visitors- are not so

1
264 THE FERTILISATION OF FLOWERS. [PART II.

numerous as those of Z. angustifolium. For while in the latter d
species distinct proterandrous dichogamy and the change in posi-—
tion of the reproductive organs have quite excluded self-fertilisation,
it remains possible in £, hirsutum. The stigmas here od dal
simultaneously with the anthers: cross-fertilisation is insured in
case of insect-visits by the more prominent position of the stigmas
but in absence of insects the stigmas curl backwards, and come ind
contact with the pollen of the eee stamens.

Epilobiuin alpinum, L., produces seed by self-fertilisation im
the absence of insects (Axel, No, 17).

A review of the foregoing species of Hpilobium brings us to thell .
same result that a comparison of the Geraniums, Polygonums, —
Alsinew, etc., leads us to, and confirms the view that no general —
deduction for a whole genus can be drawn from the floral mechanism ,
of a single species, but that each new species must be investigated _
afresh. When Delpino (175A) characterised the genus Hpilobiwm
as dichogamic and fertilised exclusively by bees, this description -
may perhaps have been true of some particular species that I am
unacquainted with; but it certainly cannot be sustained for the
whole genus,

—

ae Se Sites

169. GENOTHERA BIENNIS, L.—The structure of this flower was
minutely explained by Sprengel. The flower opens and is most
strongly odorous in the evening, and seems to have adapted itself in
this way to crepuscular and nocturnal Lepidoptera. But not only
is the pollen exposed to bees and flies, as in the nocturnal flowers
hitherto described, but the honey also is accessible to long-tongued
bees. The colour of the flower is not white, as most nocturnal
flowers are, but bright yellow, and the flower remains open or
partially open dicing the day ; so that it is probably more correct
to look upon the flower as adapted simultaneously for bees and —
nocturnal Lepidoptera.

Visitors: A. Lepidoptera—Sphinges: (1) Macroglossa stellatarum, L.,
towards evening, sucking without settling on the flower. This species was_
probably observed by Sprengel also (No. 702, p. 221). B, Hymenoptera—A pide :
(2) Bombus lapidarius, L. 9; (3) B. silvarum, L. 2; (4) B. agrorum, F. 9, |
all three sucking ; (5) Apis mellifica, L. $, s.ande.p. ; (6) Colletes Davieseana,
K. 2, ¢p.; (7) Panurgus calcaratus, Scop. ? é dusting itself with the pollen.

C, Diptera®-Syrphide ; (8) Eristalis tenax, L. ; (9) E. arbustorum, L. ; (10)
E. nemorum, L,; all three feeding on pollen, very abundant.

Gnothera sinuata, Mx.—Trelease saw this flower visited by
Ruby-throated Humming-birds (731).

ART III. | THE MECHANISMS OF FLOWERS. 265

Cnothera tenella, Bert. (Godetia Cavanillesit, Spach.), in the
- central province of Chili, produces cleistogamic flowers in spring.!
Fuchsia, L., is visited in New Zealand by Nectarinide (Anthornis
— melanura); and in North America by Ruby-throated Humming-
pirds (Potts, No. 652A, and Trelease, No. 731).
___ Lopezia coronata, Andr.—The floral mechanism of this plant is
described and figured by Hildebrand (346). In each flower there
js present one perfect stamen; a second, standing immediately
| below, is reduced to a spathulate leaf, whose two halves fold
upwards, and in the first stage, projecting horizontally from the
- flower, inclose the anther of the perfect stamen. The stalk of the
‘spathulate leaf has an elastic tension downwards, the filament of
_ the stamen an elastic tension upwards ; so when an insect alights
on the projecting spoon-shaped blade, as the only convenient spot
from which to reach two drops of honey that seem to rest upon a
knee-shaped bend in the upper petals, the leaf springs downwards,
and the stamen is set free and flies upwards, dusting the lower
‘surface of the insect with pollen. When the stamen has thus served
_its purpose, it gradually curves upwards out of the flower; and the
style which was hitherto undeveloped grows gradually out of the
flower in a horizontal direction, so as to form another alighting-
place. Self-fertilisation is rendered impossible by this marked
proterandry. I have frequently seem the whole process performed
in my room by the house-fly (Musca domestica, L.), and by the
common gnat (Culex pipiens, L.); and also at an open window by
the hive-bee.
What seem to be drops of honey on the two upper petals are
| Sin reality dry, shining bodies which deceive the flies as well as us.
| Lopezia coronata is therefore a deceptive flower like Parnassia ;
jut like the latter, also, it possesses real nectaries in addition,—
_ two yellow pits at the base of the two stamens, the functional and
$ the abortive (Delpino, No. 178).
| _ Lopezia racemosa, Cav., seems, from Ogle’s description (No.
931), to agree fully in the structure of its flower with L. coronata.
_—s Lopexia miniata, D.C., is likewise markedly proterandrous ;
_ but its stamen is not ievitabls: and does not lie inclosed by the
| spoon-shaped staminode, but stands above it (Hildebrand, No. 356).

_—«-:170. Circ#a LuTETIANA, L.—This plant is fertilised much in
, the same way as Veronica Chamedrys, L., in spite of the small

1 Philippi, Bot. Zeit. 1870, pp. 104-106,

266 THE FERTILISATION OF FLOWERS. [PART III, |

affinity between them. Two stamens and the single style project,
diverging from one another, from the middle of the erect corolla;
they form the platform on which an insect must stand to reach
the honey, which is secreted by a fleshy ring surrounding the base

_ of the style and is lodged in great abundance in the base of the —

flower. Since the style stands a little lower than the two stamens
and projects a little further forward, it forms the most convenient

alighting-place, and is that most usually selected. When an
insect settles on it, it touches with its ventral surface the stigmatic _
knob at the end. As it stretches forward, and grasps with its —

Fia. 88.—Circea lutetiana, L.

Flower viewed obliquely from above.

a, ovary.

b, the two sepals.

¢c, the two bilobed petals, alternating with the sepals.
d, the two anthers.

é, stigma.

forefeet the bases of the two stamens, which are the only available ;
supports, it involuntarily draws the stamens (which are very thin —
at their base, and therefore easily moved) inwards and downwards, —
so that the anthers dust the under surface of its body with pollen. -
Though this is apparently the simplest course which an insect —
can take, and that which most surely leads to cross-fertilisation, it
is not the only one. The insect not unfrequently alights upon —
one of the stamens, and as this bends downwards it grasps the base —
of the same stamen and of the style with its forefeet. If the style —
now brings its stigma in contact with the ventral surface of the ©

insect, as is usually, but not always, the case, it touches the side

1

_ PART III. | THE MECHANISMS OF FLOWERS. 267

opposite to that which the anther touches at the same time; and

_ so cross-fertilisation may result if the insect has come from another

flower.

In absence of insects, the flowers mostly wither without self-

fertilisation taking place, as I have observed in specimens in my

room. I have found a few flowers in which the stigma, instead of

being directed obliquely downwards between the two stamens, was
in contact with one of them from the beginning.

The only visitors that I have seen are small flies which behaved in the
manner described. I have collected (a) Syrphidw: (1) Baccha elongata, F. ;
(2) Ascia podagrica, F.; (3) Melanostoma mellina, L.; (b) Muscide : (4)
Anthomyia sp., with yellow abdomen. Several other small Muscide and

_ Syrphidee escaped me.

or

On a bunch of Circzea lutetiana which I kept in a glass of water in my room,
I found a great number of house-flies: (5) Musca domestica, L., sucking honey

_ and fertilising the flowers,

Orv. LOASEZ.

Cajophora lateritia is distinctly proterandrous, according to

_ Delpino. In the first period the anthers, which lie in five bundles
in the hollow and outspread petals, rise up one by one, bend
_ inwards towards the middle of the flower, and pass back into their
old position after giving up their pollen to insects. With these five
_ bundles there alternate five groups each containing five metamor-

phosed stamens; in each of these latter groups the three outermost

__ staminodes cohere and form in their expanded base a honey-recep-

tacle, while the two inner ones incline as stiff rods towards the

_ middle of the flower, and their bases, expanded and fringed with
hairs, give shelter to the honey. After the anthers have all withered,
_ the pistil grows up and unfolds its stigma.

In the first period the insects cling to the central tuft of

stamens; in the second, to the stiff metamorphosed protective

staminodes. The fertilisers seem to be bees, according to Delpino
(177). This is in direct contradiction to Treviranus’ view, that the
flowers of Cajophora are self-fertilising (742).

Orv. PASSIFLOREZ.

Passiflora cerulea, L., was thoroughly described by Sprengel,
who recognised it as a proterandrous form in which the anthers in
the first stage, and stigma in the second, came in contact with the

268 THE FERTILISATION OF FLOWERS. [PART IIT, —

back of the insect-visitor. Delpino has observed humble-bees and 4
Xylocopa violacea accomplishing cross-fertilisation in this manner.

(172).

divided by rings of hairs into three chambers, the lowest of which
contains the honey. From the size of the flowers, and their rich
store of honey, Delpino imagines that humming-birds are the
fertilisers; and he supposes that the triple fence serves to keep
away less intelligent visitors (178).

My brother Fritz Miller has observed in his garden at Itajahy
that some Passifloree are fertilised exclusively or chiefly by hum-
ming-birds; but he is convinced that abundance of honey is no
proof of the flower being visited by humming-birds, ‘for one
species in his garden, which is very diligently visited by them,

contains no honey and is odourless, while another smaller white ~

species flowering in Itajahy, in spite of great abundance of honey

and a pleasant scent, is never visited by humming-birds. The —

numerous corone, projecting ledges, etc., seem to him to be of
service in detaining small insects in the lowest chamber (which

often contains no honey) and keeping them caged for the hum- —

ming-birds, rather than in making access to the chamber difficult
for unprofitable visitors of low intelligence.

Orv. CUCURBITACEZ.

171. Bryonta pioica, L,—The lower part of the calyx and

corolla, both in the male flowers and in the female flowers (which

are only half as large) is adherent to a hemispherical cup-shaped

disk, whose naked, fleshy floor secretes honey. In the male flower
five irregularly formed fleshy stamens arise on the edge of this cup,
and are so expanded and inclined inwards that they completely —

roof in the cup. Four of the anthers cohere, to form two pairs ;
the fifth is free on both sides. Thus the honey-holding cup has
three narrow lateral entrances each placed between two stamens
and fringed with long hairs; and also an entrance from above in the
midst of the upper ends of the stamens. The anthers form narrow
ridges on the broad stamens, and the long, narrow slits by
which they dehisce are so bent that the greater part of each
faces one of the lateral openings, while the uppermost portion
looks directly upwards. A honey-seeking insect alighting in the
middle of the flower may thrust its proboscis down in the midst of
all the stamens, or approaching from the side it may reach the

In Passiflora racemosa, Brot. (P. princeps, Lodd.), the tube is :

ion

Ba

Ea EINE

46 omy he ee

PART 111. | THE MECHANISMS OF FLOWERS. 269

honey through one of the lateral entrances ; in either case it gets
‘dusted with pollen —in the former case on the lower surface of
its body, in the latter on both sides of its head. The pollen seems
_ to be rendered adherent by the sticky contents of the colourless
_ spheres (i, 4) which border the narrow strips of pollen; they must
come in contact with the head or ventral surface of the insect just
as the pollen itself does.

_ In the female flowers the pistil rises up from the middle of
_ the cup, and splits into three divergent branches, broad at the
_ ends, lobed, and set with projecting points. These touch the head
_ or ventral surface of an insect-visitor with their papillz and retain
the pollen that may be brought. As the male flowers are twice

'
?
i
it
‘

Fic. 89.—Bryonia dioica, L.

1, 2.—Anthers of the male flower. The arrows point to the lateral entrances.
3.— Male flower, in longitudinal section, magnified. mn, nectary.

4.—Ditto, more magnified, from above.

a, filament; p, pollen; k, colourless spherules.

is large as the female, they are generally the first to be noticed and.
visited.

To push the head between closely approximated parts of a
| flower is a characteristic action among wasps and bees, which
acquire the habit in constructing the chambers for their young.
_ The honey is easily accessible to the thin proboscis of a butterfly,

_ and the pollen of the male flowers is available to flies and beetles ;

_ but the latter can have no part in the process of fertilisation since
they confine their visits to male flowers.

_ Visitors: A. Hymenoptera—(a) Apide: (1) Andrena florea, F. 2? ¢ (A.

' rubricata, Sm.), by far the most abundant visitor of this plant, s. and c.p. ; it

/ seems to restrict itself exclusively to this plant ; (2) A. nigroaenea, K., freq., s.

, and c.p.; (3) A. fulvicrus, K. ¢,s.; (4) Halictus sexstrigatus, Schenck, ?,
|

|

270 THE FERTILISATION OF FLOWERS. [parr m1. j

e.p. only ; (5) H. sexnotatus, K. 9, cp. only ; (6) Ceelioxys simplex, Nyl.
2,8.; (7) Apis mellifica, L. $, cp.; (6) Sphegidw: (8) Gorytes mystaceus,

L., freq., s.; (9) Ammophila sabulosa, L., freq.,s.; (c) Vespide : (10) Eumenes
pomiformis, L. ¢; (11) Odynerus parietum, L.?, both sucking. B. Coleoptera
—Malacodermata : (12) Dasytes sp., only on the male flowers, fp. C. Lepi-

doptera—Rhopalocera: (13) Pieris napi, L.,s. See also No. 590, 11.

The flowers of a species of Zrianosperma in South Brazil are
visited, according to Fritz Miiller, very abundantly all day long by —
Apis mellifica and species of Melipona, although they are scentless,
greenish, quite inconspicuous, and to a great extent hidden by

foliage (597).
Orv. UMBELLIFERL.

The general phenomena of pollination in Umbellifere have —
been already so clearly and thoroughly described by Sprengel, that
I may confine myself to a short account of the most important —
peculiarities. The main features of the flowers are: firstly, the
open situation of the honey, making it accessible to even the most
short-lipped insects; and secondly, the union of many flowers in
one head, making them not only more conspicuous, but also per-—
mitting them to be more quickly searched and fertilised. Cornus
shares both of these characters with the Umbelliferz, but in a
much less perfect form.

In most Umbellifers the honey is rendered even more accessible —
than in Cornus, by the secreting disk being more convex and —
cushion-shaped, and by the stamens spreading further apart. The —
close association of many flowers is more perfectly attained in
Umbelliferze than in Cornus, far more numerous flowers uniting in
one close-set surface, so that a visitor quickly traverses the whole ;
and the florets are differentiated in the service of the community,
those in the centre being condensed, and those towards the edges
more expanded, rendering the whole more conspicuous.

As a further advantage comes proterandrous dichogamy, often
developed to such a degree that all the florets of one whole in-—
florescence only protrude their styles and develop stigmas after
the shedding of the pollen : so that in the first period of flowering ©
a whole community dusts with pollen the insects that visit it, and
in the second, exposes its stigmas to be dusted in return. So cross-
fertilisation of separate inflorescences always takes place, and the
impossibility of self-fertilisation is still further assured. Hence it
happens that in many Umbellifers (e.g. Myrrhis) towards the end
of the season only male flowers are produced, which furnish. pollen

\RT U1. | THE MECHANISMS OF FLOWERS. 271

or the last of the androgynous flowers, now in their second or
female stage.

| Hydrocotyle americana is visited in Kew by minute flies
(Henslow, 330).

Hydrocotyle vulgaris, L.—The exceedingly inconspicuous flowers
ertilise themselves. I have not yet seen them visited by insects

590, I),

d _ 172. Erynerum campsstre, L. (Thuringia).—As in all other
| Umbellifers, the upper surface of the ovary secretes and lodges the

F:c6. 90 —Eryngium campestre, L.

1.—Flower, in first (male) stage.

2.—Ditto, in second (female) stage.

3.—Ditto, after removal of sepals, petals, and styles. m, nectaries.
4.—Petal, seen from within.

(Letters as in Fig. 91).

oney : but the honey-gland here does not form, as usual, a swollen
' cushion covering the whole surface of the ovary, but a hollow
_ rounded disk five-sided in outline, and surrounded by a ten-lobed
| rough wall of tiny (accumbent) bristles. The five equal-sized

petals stand stiff and upright, with nearly the whole of their upper
halves folded inwards: they stand about 3 mm. high, and are
rertopped by the stiff, bristle-like sepals which alternate with
, them: the equally stiff and bristle-like bracts protrude still further. —
| So the honey is accessible only to insects which have a proboscis at

272 THE FERTILISATION OF FLOWERS. [PART IIT,

least 3 mm. long, or are strong enough to push apart the floral
organs which protect it. Accordingly, in connection with the fully —
developed proterandry, cross-fertilisation alone, as in all other
Umbellifers, can take place. Hryngiwm shares only slightly in that
special advantage which Umbellifers in general possess from having
their flowers massed together in one surface, for the bristle-like
bracts render it difficult for the insects to go creeping about
the umbel. This disadvantage is somewhat atoned for by the
richer secretion and better protection of the honey. Hence, in spite
of the prickly flowers, insect-visits are by no means scarce, but in
sunny weather we see the’ plant abundantly visited by wasps and
flies, bees coming in much smaller numbers. I have observed as

visitors and fertilisers :— i

}

A. Hymenoptera—(a) Sphegide; (1) Cerceris albofasciata, Dlb., scarce 2
(2) C. labiata, F., ab. ; (3) G. nasuta, K1., ab. ; (4) C. variabilis, Schr., not rare ; _
(5) Philanthus triangulum, F. ; (6) Asanoptile sabulosa, L., ab. ; (7) Tiphia
femorata, F.; (8) Priocnemis bipunctatus, F. 9; (d) Feopidins (9) Odynerus —
parietum, L. 9; (10) Polistes gallica, L., and var. diadema, very ab., almost
always to be found in sunny eeithon= (c) Chryside: (11) Chiereda sp., all
sucking ; (d) Apide: (12) Nomada Roberjeotiana, Pz. 9; (13) Andrena —
Rose, Pz. 2; (14) Halictus cylindricus, F. ¢; (15) H. longulus, Sm. ¢; (16)
Apis mellifica, L. %; all only sucking. B. Diptera—(a) Syrphide: (17)
Eristalis tenax, L. ; (18) E. arbustorum, L. ; (19) E. nemorum, L. ; (20) Helo-—
philus floreus, L.; all four abundant; (6) Muscide : (21) Lucilia Caesar, L. ;
(22) Sarcophaga carnaria, L.; (23) Echinomyia fera, L.; (24) species of
Anthomyia, all sucking. m

173. ASTRANTIA MAJOR, L.—In Astrantia major, the special
advantages which most of the other forms develop so fully, and
resemble each other so much in, are very little developed.

The umbels are simple, their florets form no close-packed
surface, the petals remain rolled up in the middle of the flower, —
and while they thus protect the honey from rain, they make it
less accessible and the flowers less conspicuous. Although the last
objection is to some extent removed by the bright white bracts,
insect-visits are less abundant than to most other forms of this
order, I have noted the following in my garden at Lippstadt :—

A. Hymenoptera—Apide: (1) Andrena albicrus, K. ¢; (2) Prosopis |
signata, Pz. ¢; (3) Pr. armillata, Nyl. ¢, all three sucking. B. Diptera— |
(a) Syrphide : (4) Eristalis arbustorum, L., fp. and Lh. ; (b) Muscidae : (5)
Lucilia cornicina, F., l.h. ; (6) Miltogramma. punctata, Mgn. C, Coleoptera—
Dermestida : (7) Anthrenus pimpinelle, F, On the Alps I have found the
plant visited by seven species of Coleoptera, three Diptera, two edane e
and one butterfly (609).

rant} THE MECHANISMS OF FLOWERS. 273

Every inflorescence bears, besides the proterandrous, androgynous
flowers, numerous male flowers which mostly develop later, and
are of obvious service in this marked case of proterandry in
fertilising the last of the androgynous flowers.

aibratisie minor, L., is both andromoncecious and androdicecious,
‘The plant bears as a rule only one umbel, which usually consists
‘of male flowers surrounded by hermaphrodite flowers ; the weaker
plants usually bear an umbel consisting only of male flowers.

ry
‘¥
‘3

=
=
i

TFT Jabulgiieigcd

Fia. 91.—Astrantia major, L.

__1,—Male flower beginning to expand. One stamen has risen up, but its anther has not yet
ehisced ; the other four are still bent down within the flower.

2.—Male flower at the middle of its flowering-period. All five stamens are erect; two anthers
Bye dehisced and are coated with pollen.

8.—Hermaphrodite flower “day inci, to expand. Two anthers are erect, but still closed ; the others
re still bent down within the flower. The styles protrude, but their stigmas are not yet "developed.

7 Be —Hermaphrodite flower in its second (female) stage. All the stamens have disappeared ; the
styles have elongated, and their stigmas are mature.
3 E oe, ovary; s, sepal; p, petal; a, anthers, still bent down within the flower; a’, ditto, erect;
', ditto, dehisced ; st, stigma, immature; st, ditto, mature.

_ In regard to the distribution of the sexes, the condition in
_ Astrantia minor is almost the same as in Veratrum album, with
_ this exception, that in Astrantia minor no plants occur bearing
on y hermaphrodite flowers. Veratrum album exhibits the pas-
sage from proterandrous androgyny through andromonecism to
androdicecism ; Astrantia minor, with similarly proterandrous herm-
aphrodite flowers: shows only the passage from andromoneecism

to androdicecism (609).
T

274 THE FERTILISATION OF FLOWERS. [PART IT.

Sanicula europea, L., is andromoneecious. Each umbel contains
one to three proterandrous hermaphrodite flowers, surrounded by
ten to twenty male flowers which develop later. Both kinds
resemble those of Astrantia major in structure (590, I.).

174. ContumM MACULATUM, L.—The adjoining figures serve to”
illustrate a peculiarity of the Umbellifers not well displayed in the
other figures, namely the very slow and gradual development of
the flowers, at first wholly male, and later wholly female.

Fig. 1 represents a flower beginning to expand, but still far
below its full size. The anther a! has dehisced and is covered with
pollen; a is on the point of dehiscence; the other three are not

oR ely ae

Fic. 92.—Conium maculatum, L.

1.—Flower at the commencement of its first (male) stage.
2.—Ditto, in the middle of its male stage.
3.—Ditto, in its second (female) stage.

hh oe ee Se a ee

ID eae

yet ripe; a° is more advanced than a; and a, the most backward, —
is still curled inwards: no trace of styles is yet to be seen. Each —
anther stands at a distance of two-fifths of the circumference from the —
preceding one. The second figure shows a slightly older and full-
sized flower, in the middle of its male period. The anther a} is
empty and withered; a? is half shrivelled and has still a slight
dusting of pollen; a? has just dehisced and is fully coated with
pollen; a* is on the point of dehiscing,—it opened while the
drawing was being made; a is still closed. The styles are still
short and bent inwards with undeveloped stigmas. Lastly, the
third figure shows a flower in its second stage: the anthers
have fallen off; the styles have raised themselves erect; a
stigmatic knob has been developed on the end of each style.
Even this notoriously poisonous plant receives abundance of
insect-visitors who greedily lick up its honey. .

PART IIT. | THE MECHANISMS OF FLOWERS. 275

. Visitors: A. Diptera—-(a) oye : (1) Sargus ncaa L. ; (0)
i - Muscide : (2) Calliphora vomitoria, L. ; (3) Lucilia cornicina, F. ; (4) Scato-
_ phaga stercoraria, L.; (5) Sepsis sp. B. Coleoptera—(a) Nitidulide: (6)
it y eligethes, ab. ; (b) Dermestide : (7) Anthrenus pimpinelle, F. ; (c) Lameilli-
i cornia: (8) Trichius fasciatus, L. C. Hymenoptera—(a) Tenthredinide : (9)
_ Nematus vittatus, L. ; (10) Several undetermined species of Tenthredo ; (0)
_ Ichneumonidae: (11) Various species ; (c) Sphegide : (12) Pompilus tritiation
2; (d) Apide: (13) Andrena lepida, Schenck, ¢. See also No. 599, 1.

}
4
}

i _ 175. BupLeuruMm FALcatum, L. (Thuringia).—I have found

the dull-yellow flowers visited only by flies and Hymenoptera.

- Visitors: A. Diptera—(a) Syrphide : (1) Syritta pipiens, L., very ab., s,
4 fp. ; (2) Eristalis arbustorum, L., s.; (3) Pipizella annulata, Macq., s. ;
(b) Bombylide: (4) Anthrax flava, Hffsgg.,s. B. Hymenoptera—(a) Ten-
thredinide : (5) Hylotoma rosarum, F., s.; (6) Vespide: (6) Polistes gallica,
u., and var. diadema, s. ; (¢) Jchnewmonide : (7) Various species, s. ; (d) Apide :
8) Halictus interruptus, Pz. ¢,s, See also No. 590, 1.

aes

q 176. CARUM (PETROSELINUM) sATIVUM, L.—The visitors are
hietly flies.

A. Diptera—(a) kg : (1) Eristalis arbustorum, L. ; (2) E. sepulcralis,
4.; (3) Helophilus floreus, L. ; (4) Syritta pipiens, L. ; (5) Xanthogramma
trofasciata, Deg. ; (b) Muscidew: (6) Lucilia cornicina, F.; (7) Cyrtoneura
mplex,. Loew {determined by Herr Winnertz) ; (8) Sarcophaga carnaria, L,
. Hymenoptera—A pide : (9) Sphecodes gibbus, L, ¢,s. See also No. 590, 1.

177. Carum cARvuI, L, :—

- Visitors: A. Diptera—(a) Stratiomyide : (1) Stratiomys longicornis, F. ; (2)
hrysomyia formosa, Scop. ; (b) Syrphide : (3) Chrysotoxum festivum, L. ; (4)
ipizella virens, F. ; (5) Melanostoma mellina, L. ; (6) Pyrophena sp., s. ; (7)
tphus ribesii, L., s.; (8) Platycheirus peltatus, Mgn.; (9) Melithreptus
niatus, Mgn. ; (10) Eristalis arbustorum, L.; (11) E. horticola, Deg. ; (12)
-gneus, Scop. ; (13) Helophilus floreus, L., very ab. ; (14) H. pendulus, L. ;
5) Syritta pipiens, L. ; (c) Muscide : (16) Gymnosoma rotundata, L. ; (17)
thinomyia fera, L.; (18) Zophomyia tremula, Scop.; (19) Sarcophaga
maria, L., and albiceps, Men. ; (d) Bibionide : (20) Bibio hortulanus, F. ;
_ *‘Tipulide; (21) Tipula, lh. B. Coleoptera—(a) Curculionidaw : (22)
ruchus, freq. ; (23) Phyllobius oblongus, L. ; Malacodermata ; (24) An-
s comus Meititain: L. ; (25) Telephorus rusticus, L. ; (c) Chrysomelide : (26)

oceris 12punctata, L. C. Hymenoptera—(a) Tenthredinide:: a mee
toma femoralis, Kl. ; (28) H. rosarum, F. ; (29) H. ceerulescens, F. ; (30) H
el Es L. ; (31) Selandria serva, L. ; (32) Athalia spinarum, F. ; (33) Tens
edo tricincta, F. ; ~e T. bifasciata, L., etc. ; (85) Dolerus eglanteria, F. ;
(6 Cimbex sericea, L.; (37) Cephus troglodytes, L. ; (b) Ichneumonide :
3) 3) Numerous species ; (c) Sphegide : (39) Cemonus unicolor, F., freq. ; (40)
Gorytes campestris, L. ¢; (41) Crabro lapidarius, Pz. 2 ; (42) Cr, pterotus,
KF do; (48) Cr. vagabundus, Pz. 2; (7) Apidae: (44) Prosopis brevicornis,
Loe T 2

- 276 THE FERTILISATION OF FLOWERS. [PART IIT,

Nyl. ¢; (45) P. communis, Nyl. ¢; (46) Halictus maculatus, Smith, 2, 8»
freq. ; (47) H. sexnotatus, K. ?, c.p.; (48) H. albipes, F. 9, c.p.; (49) An- —
drena nigrownea, K. 2, s.; (50) A. albicans, K. 9 ¢,8.; (51) A. parvula, Eg

s.ande.p. ; (52) A. fulvierus, K. 9,8. ; (53) A. nana, K. ¢,s.,and A. minutula, —
K. 9, s. D. Lepidoptera—Tineide: (54) Adela, s. E. Neuroptera—(55) —
Sialis lutaria, L. See also No. 590, 1., and No. 609.

178. StuM LATIFOLIUM, L. :—

A. Diptera—(a) Empide : (1) Empis sp. ; (b) Dolichopide : (2) Dolichopus
eeneus, Deg. ; (c) Syrphide : (3) Syrphus ribesii, L. ; (4) Eristalis nemorum, —
L.; (5) E. arbustorum, L.; (6) E. eneus, Scop. ; (7) Syritta pipiens, L.; (8) ~
Helophilus floreus, L. ; (d) Muscide: (9) Mesembrina meridiana, L., s. ; (10) _
Lucilia silvarum, Mgn. ; (11) L. Cesar, L. ; (12) L. cornicina, F. ; (13) Musea —
corvina, F. ; (14) Aricia incana, Wied., freq. ; (15) Cyrtoneura simplex, Loew ; —
(16) Calliphora vomitoria, F. ; (17) Ocyptera brassicaria, F. ; (18) Tetanocera ~
ferruginea, Fallen ; (19) Sepsis sp. ; (e) Stratiomyide : (20) Stratiomys riparia, —
Mgn. B. Coleoptera—(a) Mordellidw : (21) Mordella fasciata, F. ; (b) Mala-—
codermata : (22) Telephorus melanurus, L. ; (c) Lamellicornia: (23) Trichius—
fasciatus, L. C. Hymenoptera—(a) Tenthredinide ; (24) Selandria serva, F. ;
(25) Athalia rose, L. ; (26) Tenthredo notha, Kl. ; (b) Ichneumonidae: (27)
Numerous species; (c) Sphegide : (28) Crabro dives, H. Sch. ¢; (29) 7
lapidarius, Pz. ¢ 9, freq.; (30) C. pterotus, F. ¢; (81) C. vagus, L. g.

D. Hemiptera—(32) A small species of Anthocoride. ,

179. A®copopium PopaGcrariaA, L.—The flowers of thi
common weed are the resort of very numerous insects of various
orders. I have found upon them :— :

A. Diptera—(a) Stratiomyide : (1) Stratiomys Chameeleon, Deg. ; (2) Sargu: ¢
cuprarius, L. ; (3) Chrysomyia formosa, Scop. ; (0) Bombylide : (4) Anth 1x
flava, Mgn. (Thur.) ; (c) Empide : (5) Empis livida, L. ; (6) E. punctata, F. ;
(d) Therevide : (7) Thereva anilis, L. ; (e) Dolichopide : (8) Gymnopternus
cherophylli, Mgn. ; (f) Syrphide : (9) Pipizella virens, F. ; (10) Chrysogaster
viduata, F. ; (11) Ch. ccemeteriorum, L.; (12) Ch. chalybeata, Mgn. ; (13)
Syrphus pyrastri, L. ; (14) S. ribesii, L. ; (15) S. nitidicollis, Mgn.; (16)
Melithreptus taniatus, Mgn. ; (17) Volucella pellucens, L. (Tekl. B.) ; (18)
Eristalis arbustorum, L. ; (19) E. nemorum, L. ; (20) Helophilus floreus, L.,
ab. ; (21) Syritta pipiens, L., freq. ; (g) Muscide : (22) Echinomyia fera, L. ;
(23) Zophomyia tremula, Scop. ; (24) Sarcophaga albicans, Mgn. ; (25) Lucilia
cornicina, F, ; (26) L. silvarum, Mgn., ete, ; (27) Musca corvina, F, ; (28) Ariciv
obscurata, Mgn. ; (29) Species of Anthomyia ; (30) Scatophaga stercoraria, L. ;
(31) S, merdaria, F,; (32) Sepsis, ab. ; (kh) Tipulide: (33) Pachyrrhir
histrio, F. ; (34) P. erocata, L. B, Coleoptera—(a) Nitidulide : (35) Cych-
ramus luteus, F, (Tekl. B.) ; (b) Dermestide : (36) Anthrenus pimpinelle, F. ;
(c) Lamellicornia : (87) Phyllopertha horticola, L. ; (38) Cetonia aurata, L, ;
(39) Trichius fasciatus, L. ; (d) Elateride: (40) Agriotes aterrimus, L. ; (4 y
Lacon murinus, L, ; (42) Athous niger, L.; (e) Malacodermata: (48) Te e-
phorus fuscus, L. ; (44) Malachius bipustulatus, F. ; (45) Dasytes flavipes, F, :
(46) Trichodes apiarius, L.; (f) Cistelide: (47) Cistela murina, L.; ()

PART III. | THE MECHANISMS OF FLOWERS. 277

Mordellide: (48) Anaspis rufilabris, Gylh.; (49) A. frontalis, L.; (50)
- Mordella fasciata, F. ; (51) M. aculeata, L., very ab. ; (h) Curculionide : (52)
_ Spermophagus cardui, Schh. ; (¢) Cerambycide: (53) Pachyta octomaculata,
it F. (Tekl. B.); (54) Leptura livida, F.; (55) Grammoptera ruficornis, Pz.
a ©. og Tenthredinide : (56) Hylotoma femoralis, K1.; (57)
H. rosarum, F.; (58) H. ustulata, L. ; (59) H. vulgaris, Kl. ; (60) Selandria
serva, F., ab. ; (61) Tenthredo bifasciata, L.; (62) T. flavicornis, L. ; (63) T
‘notha, Kl, ab. ; (64) T. atra, Kl. ; (65) T. sp. ; (66) Cimbex iécives, Dis (b)
Ichneumonide : (67) Numerous species ; (c) Evaniade : (68) Foenus affectator,
. (Thur.); (69) F. jaculator, F. (Thur.) ; (d) Chryside: (70) Hedychrum
lucidulum, F. 4, freq. ; (¢) Sphegide: (71) Crabro sexcinctus, v. d. L. g
(Thur.) ; (72) Cr. cephalotes, H. Sch. ¢ (Thur.) ; (73) Cr. lapidarius, Pz. 9 ;
(74) Cr, vagus, L. 2 ; (75) Oxybelus bipunctatus, Ol. g ; (76) O. bellicosus, Ol.
> freq. ; (77) O. se Dlb. g; (78) O. uniglumis, L., very freq.; (79)
' Philanthus triangulum, F. ; (80) Cerceris variabilis, Schr. 9 ¢, not rare ; (81)
orytes campestris, L. 2 g°, not rare ; (82) Hoplisus laticinctus, Lep. 2? (Thur.) ;
(83) Pompilus niger, F. ? (Tekl. B.); (84) P. spissus, Schi. 9; (85) P
pes Wesm. ¢ (Thur.) ; (86) Myrmosa melanocephala, F. 2; (f) Ves-
: (87) Odynerus quinquefasciatus, wi Se 68) O. elegans, F. 2; (g)
vide: (89) Prosopis communis, Nyl. ¢; (90) P. clypearis, Schenck, ¢
(Thur.) ; (91) Halictus albipes, F. 9; (92) H. cylindricus, F. 2; (93) H
minutus, K. 9; (94) Andrena parvula, K. 2? ¢; (95) A. albicrus, K. 9 ; (96)
A. helvola, L. 9? ¢, cp. and s.; (97) A. fulvago, Christ. 9, cp.; (98) A.
proxima, K. 9,s. and c.p.; (99) A. albicans, K., s.; (100) A. pilipes, F. ¢,
s.; (101) A. dorsata, K. 9, ep.; (102) A. fucata, Sm. 9, s.; (103) Apis
mellifica, L. 9, ¢.p. D. Neuroptera—(104) Panorpa communis, L.

180. PimpiNELLA MAGNA, L.—lI have had very little oppor-
tunity of observing this species, and I have only noticed the
ollowing insect-visitors in Low Germany.

1 | Apide: (1) Andrena parvula, K. 2, sand c.p. ; (2) A. Rose, Pz. ¢,s.

In the subalpine region of the Alps it usually bears only
jnkish flowers (P. magna, {3 rosea, Koch = P. rubra, Hoppe), which
ircumstance may be attributed to the more intense action of
ight in this region. I have found the pink variety on the Alps
_ visited by six species of beetles, seven flies, two Hymenoptera, and

_ one butterfly (609).

| ; 181. PIMPINELLA SAXIFRAGA, L. :—

Visitors: A. See in Tabanide: (1) Tabanus micans, Mgn. ; (2)
a ysops ceecutiens, L.; (b) Asilide: (3) Isopogon art Mgn.; (c)
} phide: (4) Syrphus nitidicollis, Mgn. ; (5) S. pyrastri, L. ; (6) Eristalis
- icola, Mgn. ; (d) Conopide: (7) Conops 4-fasciata, Deg.; (e) Tipulide :
8) Pachyrrhina crocata, L. B. Se ae Malacodermata: (9) Tele-
orus melanurus, F,; (10) Dasytes flavipes, F. (Thur.) ; (0) Cerambycide :
() Pachyta octomaculata, F., ab. (Sld.) ; (ce) Chrysomelide: (12) Clythra

278 THE FERTILISATION OF FLOWERS. [parr m1,

scopolina, L. (Thur.).. C. Hymenoptera—(a) Tenthredinide : (13) Hylotoma
rosarum, F,; (14) Selandria serva, L. ; (15) Tenthredo bicincta, L. ; (16) T.
notha, K1., ab. ; (17) T. bifasciata, L., etc. ; (18) Cimbex sericea, L. ; (b) Ichneu-
monide : (19) Numerous species ; (ce) Apidw: (20) Sphecodes gibbus, L., s. ;
(21) Andrena parvula, K., s. and e.p. ; (22) A. fulvescens, Sm. g. D. Neuro
ptera—(23) Panorpa commmtitic L.

182. Myrruis oporaTa, Scop.—The accompanying fi
represent flowers of this species as I saw them towards the end
of their flowering period, June 13, 1871. The flowers last
developed are male only, their anthers and petals fall off without
their developing styles or stigmas upon their stunted ovaries. —
These male flowers, as in cases described above, furnish pollen
for the last of the hermaphrodite flowers when in their second —
or female stage. I have had no opportunity of observing the

Fic. 93.—Myrrhis odorata, Scop.

1.—Male flower, at the end of its flowering-period.

2.—Diito, withered.

3 —Hermaphrodite flower in its last stage.

ov, ovary; n, nectary; p, petal ; a, anther ; a’, ditto, not yet dehisced,

fertilisation of Myrrhis odorata, which, in the neighbourhood of |
Lippstadt, occurs wild only in an isolated patch. Herr Borgstett

sent me the following list of species which he collected on the
flowers of this plant at Teklenburg :—

A. Diptera—(a) Bombylide : (1) Bombylius major, L. ; (6) Empide: (2
Empis tesselata, F. ; (c) Syrphidw: (3) Xylota femorata, L. B. Coleoptera
Chrysomelide : (4) Galeruca calmariensis, L. C. Hymenoptera—(a) Jehner
monide: (5) Several species ; (b) Apide: (6) Halictus maculatus, Sm.
have since added twenty-seven species to this list (590, 1.). |

183. CHAROPHYLLUM HIRSUTUM, L, :—

Visitors: A. Diptera—Syrphide: (1) Eristalis pertinax, Scop. B. Cole
optera—(a) Elateride : (2) Agriotes gallieus, Lap. (Thur.) ; (b) Gidemeride

east ee ee

parti] § THE MECHANISMS OF FLOWERS. 279

(8) CGEdemera flavescens, L. herve C, Hymenoptera—(a) Tenthredinide :
(4) Hylotoma enodis, L., ab.; (5) H. segmentaria, Pz, (Thur.) : (6) ert
_ bifasciata, L. (Thur.) ; (7) T. notha, Kl.; (8) T. sp. ; (9) Athalia rose, L. ; (b)
_ Evaniade: (10) Foenus affectator, F. (Thur.) ; : ‘(c) Chryside : (11) Chrysis
ignita, L. (Thur.) ; (d) Sphegide: (12) Crabro subterraneus, F, ¢ (Thur.) ;
(13) Pompilus pectinipes, v. d. L. (Thur.) ; (14) Myrmosa melanostoma, F.
(Thur.) ; (e¢) Apide: (15) Sphecodes ephippia, L.

184. CHAROPHYLLUM TEMULUM, L, :—

Visitors: A. Diptera—(a) Stratiomyide : (1) Chrysomyia formosa, Scop. ;
(b) Syrphide : (2) Cheilosia scutellata, Fallen ; (3) Chrysogaster coemeteriorum,
L. ; (4) Melanostoma mellina, L. ; (5) Melithreptus scriptus, L. ; (6) Baccha
élongata, F.; (7) Eristalis nemorum, L.; (8) Helophilus floreus, L. ; (9)
Syritta pipiens, L. ; (b) AMuscide: (10) Gymnosoma rotundata, L. B. Cole-
optera—(a) Nitidulide : e es Sea (6) Dermestide ; (12) Anthrenus
8c ophularie, L.; (13) A. pimpinelle, F.; (¢) Cerambycide : (14) Leptura
livida, L. ; (15) Pachyta S-rnietulata, F, (Tekl. B.). C. Hymenoptera—(a)
Z atatinicles (16) Tenthredo flavicornis, Ll. ; (17) T. notha, Kl. ; (18) T.
re stica, L. ; (19) Several undetermined species of Tenthredo ; (b) Sphegide :
20) Crabro cribrarius, L. 9 ¢; (21) Entomognathus brevis, v. d. L. 2; (c)
ee: (22) Odynerus parietum, L. 2 ; (d) Apide: @8) Andrena Collinsoniana,
if and cp. See also No. 590, 1.

185. ANTHRISCUS SILVESTRIS, Hoffm.—The accompanying
igures show some of the special adaptations which all typical
Umbbelliferse share. These features are: (1) the fully exposed

Fic. 94.—Anthriscus silvestris, Hofim.

_ 1.—Flower in first (male) stage. a, anthers not yet dehisced ; a’, ditto, dehisced. The styles
‘e not yet visible.
_ 2.—Flower in second (female) stage. The stamens have fallen off, the styles have appeared, and
‘th eir stigmas : are mature.
PD, inner, p’, outer petals; ov, ovary ; oy nectary ; st, stigma.

; tuation of the honey, due to the cushion-shaped swelling of
, the disk which secretes it, to the absence at first of styles,
_ to the widely outstretched position of the petals, and to the

280 THE FERTILISATION OF FLOWERS. [PART IIT.

peculiar nature of the anthers which, before dehiscence, are
bent backwards outside the flower, and afterwards, erecting
themselves slightly, stand pointing obliquely outwards, and
easily fall off altogether at the coming of an insect; (2) the
complete proterandry, so fully developed that every trace of
anthers has disappeared when the stigmas arrive at maturity ;
(3) the loss of regularity in the separate flowers for the good of
the community, the outer petals developing at the cost of the
inner ones,

As in the forms just mentioned, we find visiting Anthriscus
silvestris a very miscellaneous company of insects, chiefly with
short proboscides, to lick up the flat layer of honey from the
disk ; a few bumble-bees and Muscidz to feed on pollen, anda —
few bees to collect it, As they pass quickly over the surface of —
the umbels, and frequently fly from one to another, they easily
dust their body and legs with pollen upon young flowers, and
accomplish numerous cross-fertilisations in a short time.

I have repeatedly found hive-bees collecting pollen on
Anthriscus silvestris; they ran over the umbels with the utmost
speed, so quickly that I could not follow with my eye the act of
pollen-gathering, and they stripped off many anthers completely. —
In spite of their industry, which is so often very useful to other
flowers, they are of little or no use to Anthriscus silvestris ;
for they take away the pollen, but never or only rarely go to
umbels in the second stage, and so seldom or never effect
cross-fertilisation. |

Visitors: A. Diptera—(a) Stratiomyide : (1) Nemotelus pantherinus, L. ;

(2) Stratiomys Chameleon, Deg. ; (b) Empide: (3) Empis punctata, F.; —
(4) E. stercorea, L. ; (c) Syrphide : (5) Syrphus corolle, F. ; (6) S. ribesii, L. ; _
(7) Melithreptus scriptus, L. ; (8) M. pictus, Mgn. ; (9) Ascia podagrica, F.;
(10) Eristalis arbustorum, L. ; (11) E. pertinax, Scop. ; (12) Helophilus floreus, —
L. ; (13) Syritta pipiens, L..; (d) Muscide: (14) Echinomyia fera, L.; (15) —
Zophomyia tremula, Scop. ; (16) Sarcophaga sp. ; (17) Lucilia sericata, Mgn. ;
(18) Musca corvina, F. ; (19) Graphomyia maculata, Scop. ; (20) Scatophaga
merdaria, F, ; (21) S. stercoraria, L., ab. ; (22) Sepsis sp. ; (23) Psila fimetaria,
L. ; (e) Bibionide : (24) Bibio hortulanus, F.; (f) Tipulide: (25) Pachyr- —

rhina crocata, L. ; (26) P. pratensis, L. B. Coleoptera—(a) Nitidulide: (27) —

Epureea sp. ; (28) Meligethes ; (b) Elateride: (29) Synaptus filiformis, F. ;
30) Lacon murinus, L., freq. ; (81) Athous niger, L. ; (82) Corymbites quereus,
Ill. ; (¢) Malacodermata : (33) Telephorus fuseus, L. ; (84) T. rusticus, F. ;
(35) T. lividus, L. ; (86) Malachius wneus, L.; (87) M. bipustulatus, F. ; (d)
Cistelide : (38) Cistela murina, L. ; (e) Mordellide: (39) Mordella fasciata,
F. ; (40) M. pumila, Gyll. ; (f) Curculionide : (41) Bruchus, freq. ; (g) Ceram-
bycide ; (42) Clytus arietis, L.; (43) Pachyta collaris, L. (Thur); (44) P.

PART 111. ] THE MECHANISMS OF FLOWERS. 281

octomaculata, F. (Thur.) ; (45) Grammoptera lurida, F. (Tekl. B.) ; (46) G
ruficornis, F, C. Hymenoptera—(a) Tenthredinide : (47) Hylotoma femoralis,
_ Ki. (Thur.) ; (48) Macrophya neglecta, Kl. ; (49) Tenthredo notha, K1. ; (50)
1. rape, K1.; (61) T. annulata, F.; (52) T. rustica, L. ; (53) T. sp.; (54)
' Selandria serva, F.; (55) Athalia rose, L. ; (56) Dolerus cenchris, Htg. ; (57)
Nematus vittatus, Lep.; (58) N. mapacticlis; F.; (b) Ichneumonide : (59)
Various species; (c) Formicide: (60) Various species ; (d) Sphegide: (61)
abro sexcinctus, v. d. L. ¢; (62) Cr. cephalotes, H. Sch. g (Thur.) ; (63)
Hoplisus laticinctus, Lep. 9 (Thur.) ; (64) Pompilus neglectus, Wesm. 9?
(Thur.) ; (65) P. viaticus, L. 9; (e) Vespide : (66) Odynerus elegans, H. Sch.
© (Tekl. B.) ; (f) Apide: (67) Halictus Smeathmanellus, K. ? ; (68) Andrena
parvula, K., s. and c.p.; (69) A.Collinsoniana, K. 9; (70) A. fucata, Sm. 9 ;
71) Apis mellifica, L. $, ep. D, Neuroptera—(72) Sialis lutaria, L. ; (73)

~

emerobius sp. See also No. 590, I.

186. ANTHRISCUS CEREFOLIUM, Hoffm. :—

Visitors: A. Diptera—(a) Syrphide: (1) Eristalis arbustorum, L.; (2)
E. nemorum, L. ; (3) Syritta pipiens, L.; (b) Muscide: (4) Gymnosoma
rotundata, L.; (5) Exorista vulgaris, Fallen; (6) Sarcophaga heemarrhoa,
Meigen (determined by Herr Winnertz) ; (7) 8. dissimilis, Mgn. (do.) ; (8)
oo simplex, Loew. (do.) ; (9) Anthomyia radicum, L. (do.) ; (10) Sepsis
., Lh. ; (ce) Bibionide: (11) Bibio hortulanus, F. B. Coleoptera—(a) Niti-
hulide : (12) Meligethes, very ab., l.h., also pairing on the flowers; (6d)
: Dermestide : (13) Anthrenus pimnpitiellen, .; (14) A. serophularie, L., both
ab., lh. ; “a Malacodermata : (15) Anthocomus fasciatus, L. ; (16) Malachius
eneus, F .; (d) Mordellide ; (17) Anaspis frontalis, Lh. ; (ce) Cerambycide :
(18) Grammoptera ruficornis, F., lh. C. Hymenoptera——(a) Ichneumonide :
(19) Numerous species ; (6) ormicida (20) Several species ; (ce) Sphegide:
(21) Oxybelus uniglumis, L., ab. ; (22) Pompilus pectinipes, v. d. L. ¢;
(23) P. spissus, Schi. ; (d) A cot : " (24) Prosopis communis, Nyl. ¢; (25) P.
imillata, Nyl. 9; (26) Apis mellifica, L. $, e.p.

oe een e

=)

a ll

187. CGENANTHE FISTULOSA, L. :—

Sa ie me ala AE Sat

_ Visitors : A. Diptera—(a) Stratiomyide : (1) Stratiomys Chameleon, Deg. ;
b) Empide : (2) Empis livida, L. ; (3) E. rustica, Fallen ; (c) Leptida : (4)
Antherix = L.; (d) Syrphide: © Syritta pipiens, ah (6) Eristalis
ne morum, L .; (7) E. arbustorum, L.; (8) E. sepulcralis, L.; (9) Various
| a ecies of Lucilia, all sucking. B. Coleoptera—Lamellicornia : (10) Trichius
' fasciatus, L. C. nie gorge pide: (11) Macropis labiata, Pz. ¢, s. ;
( 12) Heriades truncorum, L. 2, s. ; (13) Prosopis sp. See also No. 590, I.

5 'f

188. CENANTHE PHELLANDRIUM, Lam. :—
1a ; ‘ Visitors: A. Diptera—(a) ie Maly yide : (1) Odontomyia viridula, F. ; (d)
yrphide : (2) Syritta pipiens, L. ; (3) Eristalis arbustorum, L., and others ;

© Muscide: (4) Lucilia cornicina, F.; (5) Aricia vagans, Fallen ; (6)
I i Cyrtoneura curvipes, Macq. (determined by Herr Winnertz) ; all sucking ; (d)

282 THE FERTILISATION OF FLOWERS. [PART LIT.

Mycetophilide : (7) Sciara Thome, L. B. Coleoptera—(a) Chrysomelide :

(8) Helodes Phellandrii, L., devouring whole umbels down to the pedunele ;
(b) Cerambycide: (9) Leptura livida, L., ab., licking the fleshy disk; (¢)
Elateride : (10) Adrastus pallens, Er. C. Hymenoptera—(a) Tenthredinide: —
(11) Athalia rose, L.; (12) Tenthredo sp. ; (b) Ichneumonide: (13) various —
species ; (c) Sphegide : (14) Tiphia ruficornis, K. ; (15) Oxybelus bipunctatus,
Ol. 2; (16) Pompilus viaticus, L. ; (17) P. trivialis, Kl. 9; (d) Apidae: (18)
Prosopis variegata, F. ¢; (19) Sphecodes gibbus, L. ¢. D. Lepidoptera—
(20) Vanessa C-album, L.

SO

189. SILAUS PRATENSIS, Bess.—I can only mention the follow-
ing as fertilisers of this species, which I have had few opportunities
of observing :— |

Hymenoptera—(qa) Tenthredinide : (1) Tenthredo notha, K1. ; (b) Sphegide :
(2) Pompilus viaticus, L. g, 1h. ; (ce) Apide: (3) Halictus longulus,Sm.g,s.

190. ANGELICA SILVESTRIS, L, :—

Visitors: A. Diptera—(a) Syrphide: (1) Syritta pipiens, L.; (2) Helo- —
philus floreus, L. ; (8) Eristalis pertinax, Scop. ; (4) Pipizella virens, F.; (6) —
Muscide : (5) Tachina prepotens, Mgn. (determined by Herr Winnertz) ; (6) —
Echinomyia fera, L. ; (7) Mesembrina meridiana, L. ; (8) Scatophaga stercorari ;
L.; (9) S. merdaria, F. ; (10) Lucilia silvarum, L. ; (11) Sarcophaga sp. B.
Coleoptera—(a) Dermestide: (12) Anthrenus pimpinelle, F.; (b) Lamelli
cornia: (13) Trichius fasciatus, L., 1h. ; (ce) Malacodermata: (14) Telepho Ss
melanurus, L. ; (d) Coccinellide : (15) Coccinella 7-punctata, L., s.; (16);C.
14-punctata, L., s.; (e) Nitidulide: (17) Meligethes, ab. C. Hymenoptera— —
(a) Tenthredinidw: (18) Athalia rose, L.; (19) Species of Tenthredo ; (b)
Ichnewmonide : (20) Various species ; (c) Evaniade : (21) Foenus affectator, F. ;_
(d) Sphegide : (22) Crabro lapidarius, Pz. ¢ 2 (Thur.), ab. ; (23) Philanthus
triangulum, F. ; (e) Vespidew: (24) Odynerus sinuatus, F. 9 ; (25) O. debili- —
tatus, Sauss.; (26) Vespa rufa, L. $,s.; (f) Apide: (27) Species of Pro-
sopis, 8. ; (28) Andrena pilipes, F. 9, 8. D. Lepidoptera—(29) Argynnis —
Paphia, L. (Willebadessen) (s.?) E. Neuroptera—(30) Panorpa communis, L., —
Ih. See also No. 590, 1., and No. 609. |

191, PEUceEDANUM CrRvariA, Lap.—On the slope of
Rehmberg, near Miihlberg in Thuringia, a locality rich in
plants, I found on the last sunny days in August, 1869, the followin:
insects, many of them rare, upon this still rarer Umbellifer :—

et Oise Samy,

at

ee ee

A. Diptera—(a) Bombylide : (1) Anthrax maura, L.; (6) Muscide: (2)
Phasia crassipennis, F., ab. ; (3) Ph. analis, F., scarce ; (4) Gymnosom
rotundata, L., very ab. B, Coleoptera—(a) Chrysomelide: (5) Clythr
scopolina, L. ; (b) Cerambycide : (6) Strangalia bifasciata, Miiller. C. Hymen-
optera—(a) Chryside: (7) Hedychrum lucidulum, F. ¢ 2; (b) Sphegide:
(8) Crabro vagus, L. 9; (9) Cr. cribrarius, L. ¢ 9, ab. ; (10) Nysson mac
latus, v. d. L. 9; (11) Tachytes unicolor, Pz. 9; (12) T. pectinipes, v. d. Li

Bre Rp aai onioniye

varrut] © THE MECHANISMS OF FLOWERS. 283

9; (13) Ammophila sabulosa, L.; (14) Psammophila viatica, L. ¢; (15)
- Pompilus viaticus, L. ¢ ; (16) Priocnemis bipunctatus, F. 2 ; (17) Pr. obtusi-
_ ventris, Schiddte, 9; (18) Ceropales maculata, F. 9; (19) C. variegata, F.
96; (20) Tiphia femorata, F., very ab., all licking honey ; (c) Vespide:
(28) Polistes gallica, L., and var. dindenha’: ; (d) Apide: (22) Prosopis
| variegata, F., s.; (23) Halictus leucozonius, Schrk. ¢ ?, s. and e.p.; (24)
H. quadricinctus, F. 2,8. ; (25) Andrena minutula, K. 92, freq., c.p. ; (26)
Megachile lagopoda, Pz. 2, once, sucking.

It is a remarkable fact that this scarce Umbellifer is visited by
a choice collection of rare insects, while the most common visitants
are absent. I do not think that this is due to a special taste of its
honey, but I suppose that the same conditions necessary for the
plant’s existence are also favourable to special insects.

_ 192. PeucEDANUM (ANETHUM) GRAVEOLENS, L.—The dirty-
yellow flowers of this plant are, like those of Bupleurwm, visited
by Diptera and Hymenoptera, but far more plentifully and
i by a greater variety of forms, owing, doubtless, to the strong
odour of the flowers. No species of beetle occurs among the very
numerous visitors.

_ Visitors: A. Diptera—(a) Stratiomyide: (1) Chrysomyia formosa, Scop.,
3.; (b) Bombylidw: (2) Anthrax maura, L. (Thur.); (c) Syrphide: (8)
Cheilosia scutellata, Fallen ; (4) Syrphus pyrastri, L., sucking, as also were the
following : (5) Eristalis arbustorum, L. ; (6) E. nemorum, L.; (7) E. sepulcralis,
L. ; (8) E. tenax, L. ; (9) Syritta pipiens, L. ; (2) Muscide: (10) Gymnosoma
' rotundata, L., ab. ; (11) Lucilia cornicina, F. ; (12) Musca corvina, F. ; (13)
_ Oyrtoneura simplex, Loew., and curvipes, Macq., the last two identified by Herr
Winnertz; (14) Sepsis, ab.; (e) Tipulide: (15) Tipula sp. B. Hymenoptera :
(a) Tenthredinide : (16) Several species of Tenthredo ; (b) Ichneumonide : (17)
Numerous species ; (¢) Lvaniade : (18) Foenus affectator, F. ; (19) F. jaculator,
F. (Thur.) ; (d) Formicide: freq. ; (e) Chryside: (20) Hedychrum lucidu-
lum, F. 2 ¢, freq. ; (21) Chrysis ignita, L. 9; (22) Chr. bidentata, L. ¢ ;
(f) Sphegide : (23) Crabro sexcinctus, v. d. L. ¢ (Thur.); (24) Cr. vexil-
latus, Pz. 2 (Thur.) ; (25) Cr. podagricus, H. Sch. 9 (Thur.) ; (26) Cr. denti-
erus, H. Sch. ; (27) Cr. Wesmeeli, v. d. L. ¢; (28) Oxybelus uniglumis, L.,
b. ; (29) Tripoxylon clavicerum, v. d. L. 2; (80) Cemonus unicolor, F. 9 ;
' (81) Tacytes pectinipes, L. 9 (Thur.) ; (32) Psen atratus, Pz. ? ¢ (Thur,) ;
| a Pompilus cinctellus, v. d. L. 9 ; (34) P. neglectus, Wesm. @ (Thur,
pty 14, 1870 !) ; (35) Tiphia femorata, F. ¢; (36) Myrmosa melanocephala,

. (Thur,, July 14, 1870!) ; (g) Vespide : (37) Odynerus parietum, L. ; (38)
0. atts, Sauss. ; (39) Eumenes pomiformis, L. ¢; (40) Polistes gallica,
cree.) 5 ; (h) Anida: (41) Prosopis sinuata, Schenck, ¢ 2 (Thur.) ; (42)
. communis, Nyl. 2 ¢ (Tekl. B.) ; (43) Pr. armillata, Nyl. ¢ (Tekl. B.) ;
(a4) Sphecodes gibbus, L. ¢ 2, ab.; (45) Andrena parvula, K. ?, cp. ; (46)
A. dorsata, K. 9, e.p.

284 THE FERTILISATION OF FLOWERS. [PART IIT.

193. PeucepANUM (PaAsTINAcA) SATIVUM, L. (Thuringia) :—

Visitors: A. Diptera—(a) Bombylide: (1) Anthrax flava, Hffsgg., Lh. ;
(b) Syrphide: (2) Chrysotoxum bicinctum, L, ; (8) Syritta pipiens, L. ; (e)
Muscide: (4) Dexia rustica, F.; (5) Onesia sepuleralis, Mgn.; (6) Lucilia
silvarum, Mgn. ; (7) Sarcophaga carnaria, L. B. Hymenoptera—(a) Tenthre-
dinide : (8) Several species of Tenthredo ; (b) Ichneumonidae : (9) Numerous
species ; (c) Sphegide : (10) Crabro sexcinctus, v. d. L. ¢ ; (11) Tiphia femo-
rata, F.; (12) Mutilla europea, L. 9; (d) Vespide: (13) Polistes gallica, L.,
and var. diadema ; (14) Odynerus parietum, L. ¢. See also No. 590, 1.

So the dull yellow flowers of this plant, like those of Bupleurum
and Anethum, are visited only by Diptera and Hymenoptera, not —
by Beetles.

194. HeERACLEUM SPHONDYLIuM, L. :—

Visitors : A. Diptera—(a) Bombylide : (1) Anthrax flava, Hff. (Sld. Tek].

B.) ; (b) Empide: (2) Empis livida, L.; (c) Asilide: (3) Dioctria Rein-—
hardi, Wied., ab. (Sld.); (d) Syrphide: (4) Chrysotoxum bicinctum, L. |
(Sld.) ; (5) Ch. festivum, L. (Tekl. B.) ; (6) Pipizella virens, F.; (7) P. annu-—
lata, Macq. ; (8) Chrysogaster viduata, L.; (9) Cheilosia scutellata, Fall. ;
(10) Syrphus glaucius, L. ;-(11) S. ribesii, L.; (12) S. pyrastri, L.; (13) —
Melithreptus ee L.; (14) Ascia peer F.; (15) Eristalis tenax,
L.; (16) E. nemorum, L. ; (17) E. arbustorum, L. ; (18) E. sepulcralis, L. ;_
(19) E. eneus, Scop. ; (20) E. pertinax, Scop. ; (21) E. horticola, Mgn. ea)
(22) api gee Ronan L., ab. 3. (23) Xylota see L. (Sld.) ; (24) Syrit

pipiens, L. ; (e) pase (25) Zodion cinereum, F. (Sld.); (f) Muscide :
(26) Echinomyia grossa, L. (Haar); (27) E. fera, L.; (28) E. magnicornis,
Zett. ; (29) Nemorea sp. ; (80) Exorista vulgaris, Fallen ; (81) Tachina eru-
carum, Rond. ; (32) Sarcophaga carnaria, L., ab. ; (33) S. hemarrhoa, Mgn. ; —
(34) Onesia sepulcralis, Mgn. ; (35) O. floralis, Rob. Desv. ; (36) Grapho- —
myia maculata, Scop. ; (37) Lucilia oa Mgn.; (38) L. Caesar, L. ; (39) ©
L. silvarum, oe (40) L. cornicina, F.; (41) Pyrellia enea, Zett. ; 5
Musca corvina, F.; (43) eye eunteahia: l.; (44) C. erythrocephala, ;
Mgn. ; (45) Scatophaga merdaria, F., ab. ; (46) Sepsis cynipsea, L., ab. ; (g)_
Tabanide: (47) Tabanus rusticus, L.; (h) Mycetophilide: (48) ’Platyt aS:
sp. ; (i) Tipulide: (49) Pachyrrhina histrio, F. B. Coleoptera—(a) Nitidu-
lide: (50) Thalycra sericea, Er. (Siebengebirge) ; (51) Meligethes, ab. ; (b)
Dermestide : (52) Anthrenus pimpinelle, F. ; (c) Lamellicornia : (53) Hoplia
philanthus, Sulz., very freq. (Sld.) ; (54) Trichodes fasciatus, L., ab. ; (55)
Cetonia aurata, L., very ab., (Sld. Siebengeb.) ; (d) Elateride: (56) Agriotes
ustulatus, Schaller (Thur.) ; (57) Corymbites holosericeus, L. ; (58) C. hema-
todes, F. (Siebengeb., July 8, 1871); (e) Malacodermata: (59) Telephorus
melanurus, F., very freq. ; (60) T. fuscus, L.; (61) T. lividus, L. ; (62) Tri-_
chodes apiarius, L. ; (f/) Mordellide : (63) Mordella fasciata, L. ; (g) Gide-—
merida : (64) C&demera virescens, L.; (kh) Cerambycide : (65) Rhagium >
inquisitor, F, (Sld.) ; (66) Pachyta 8- maculata, F., ab. Les Siebengeb.) ; (67) |
Strangalia melanura, L., very “3 Berd (68) S. nigre, .3 (0) Chrysomelide :
(69) Cryptocephalus sericeus, L. ; (hk) Coccinellide: (70) Exochomus auritus,

@

arvit.| THE MECHANISMS OF FLOWERS. 285

Scriba. ©. Hymenoptera—(a) Yenthredinide: (71) Tenthredo bifasciata, L.,
b. ; (72) T. notha, Kl, not rare; (73) T. tricincta, F. ; (74) T. sp.; (75)
T. annulata, F. ; (76) ee serva, F., very ake ; (77) Athalia rose, L. ;/
_ (78) Hylotoma rosarum, F, ; (79) H. coerulescens, F.; (80) H. ustulata, L. ;
(81) H. vulgaris, Kl. ; (82) H. femoralis, K1. ; (83) Cimbex sericea, L., not tare
( Sld.) ; (b) Ichneumonide : (84) Numerous species ; (¢) Sphegide: (85) Crabro
lapidarius, Pz.? ¢, freq. ; (86) Cr. vagus, L.? ¢; (87) Cr. cribrarius, L.? ¢;
(88) Oxybelus nniglomis, L., ab. ; (89) Philanthus triangulum, F. ?; (90)
G ory tes campestris, L. 2 ¢, not rare ; (91) Dinetus pictus, F. 9 ¢, ab.; (92)
M imesa bicolor, Sh. (Thur.) ; (93) M. unicolor, vy. d. L. (Thur.) ; (94) Pom-
jilus viaticus, L. ¢ ; (95) P. pectinipes, v. d. L. ¢; (96) Priocnemis exaltatus,
. (Thur.) ; (97) Ceropales maculata, F., not rare ; (98) by tae femorata, F., ab. ;
Vespide : (99) Odynerus pariétam, L., ab. ; (100) O. sinuatus, F. ; (101)
O. trifasciatus, F. 2; (102) Vespa rufa, a 2; (103) V. holsatica, F. ¢ ; (104)
V. vulgaris, L. 9; (e) Apidw: (105) Prosopis armillata, Nyl. 2; (106) Hal-
ictus cylindricus, F. 2, covered with pollen on the whole hairy ventral sur-
fi ®; (107) H. leucopus, K. ¢; (108) H. flavipes, F. 9; (109) Andrena

nana, K. 2,s.; (110) A. fucata, Sm. 2, ab.,s. and c.p.; (111) A. coitana,
Ki@, not rare (Sld.) ; (112) A. Rose, Pz. 9, freq. ; (118) Sphecodes gibbus,
L tS: s.; (114) Nomada ferruginata, K. 2,s.; (115) Megachile centuncu-
aris, L. 2, ¢.p.; (116) Bombus terrestris, L. 9, ¢.p.; (117) Apis mellifica,
8, ‘: and ¢. Pe D. Hemiptera—(118) Several bugs. See also No. 590, 1., and
No. 609.

195. Daucus Carota, L.:—

.
,

a: A. Diptera—(q) Stratiomyide : (1) Stratiomys Chameleon, Deg.,
; (2) S. riparia, Mgn., ab.; (b) Bombylide: (3) Anthrax flava, Hf.
T har): (c) Syrphide : (4) Pivtsella annulata, Macq. ; (5) Pipiza funebris, F. ;
(6) Chrysogaster viduata, L. ; St Cheilosia soror, Zett. ; (8) Syrphus pyrastri,
4.; (9) Melithreptus scriptus, L. ; (10) M. teeniatus, Mgn. ; (11) Ascia poda-
3 F. ; (12) Eristalis sepuleralis, L. ; (13) E. arbustorum, L. ; (14) Helo-
philus floreus, L. ; (15) Syritta pipiens, L.; (d) Muscide: (16) Gymnosoma
otundata, L. ; (17) Sarcophaga albiceps, Mgn. (Thur.) ; (18) Species of Lucilia ;
19) Species of Sepsis. B. Coleoptera—(a) Dermestide : (20) Anthrenus pim-
i nelle, F. ; (6) Lamellicornia: (21) Trichius fasciatus, L. ; (c) Elateride :
22) Agriotes sputator, L. (Thur.) ; (23) A. ustulatus, Schaller (Thur.) ; (24)
__ A. gallicus, Lap. (Thur. ; ; (d) Malacodermata: (25) Dasytes pallipes, Pz.
~ (Thur.) ; (e) Mordellide: (26) Mordella fasciata, F.; (27) M. aculeata, L. ;
(f) Cureulionide: (28) Spermophagus cardui, Sch. (Thur.) ; (g) Corane-
bycide : (29) Strangalia bifasciata, Miller (Thur.). C. Hymenoptera—(a)
| $ . Tenthredinide : (30) Hylotoma ustulata, L. (Thur.) ; (31) H. femoralis, K1.
1 = ¢ hur.) ; (32) Selandria serva, F.; (33) Athalia rose, L. ; (34) Tenthredo
‘notha, Kl. ; (6) Ichneuwmonide : (35) Various ; (c) Chryside: (86) Hedychrum
Incidulum, F. ¢ 2 (Thur.), ab. ; (d) Sphegide: (37) Oxybelus ee L.,
; (38) O. bipunctatus, Ol. ; (39) Pompilus niger, F. ¢; (40) P. viaticus,
4. 6; (41) P. neglectus, Wesm. ¢; (42) P. intermedius, Schenck ; (43) Prio-
ne nis obtusiventris, Schi. (Thur) ; (44) Ceropales maculata, F. ; (45) Tiphia
lemorata, F., freq. ; (46) Mutilla europea, L. ¢ (Thur., July 14, 1870) ; (47)
is wariabilis, Schr. 2; (e) Vespide: (48) Odynerus sinuatus, F. 9°;

286 THE FERTILISATION OF FLOWERS. [PART 11,

(f) Apide : (49) Prosopis variegata, F. ¢ (Thur.) ; (50) P. sinuata, Schenck ;
&; (51) Sphecodes gibbus, L. 9 ; (52) Halictus albipes, F. ¢; (53) H. inter-
ruptus, Pz. 9 (Thur.) ; (54) H. fulvicornis, K. ¢; (55) Andrena parvula, K.;%
(56) A. nana, K. 9,s.; (57) Nomada lateralis, Pz. Q (Thur.). D. Lepidop-
tera—(a) Rhopalocera: (58) Hesperia lineola, O., s. ; (b) Tineina: (59) Nemo-
tois, Hbn., sp., s. E. Hemiptera—(60) Tetyra nigrolineata, L. (Thur.), ab,
F. Neuroptera—(61) Hemerobius. See also No. 590, I.

Daucus (Orlaya) grandiflora, Hoffm.—tThis species has three —
different kinds of flowers, all differmg in form and degree of
conspicuousness: (1) In the centre of the umbellule the florets _
are male only, and have small incurved petals; (2) at the edge of —
the umbellule the florets are asexual, and the outermost petal is ~
greatly enlarged; (3) at the margin of the whole umbel are ~
female florets, in which the outer petals attain a gigantic size ~
(590, I.). . . |

Caucalis daucoides, L., is visited by Tetyra nigrolineata, L.
(Hemiptera) (590, I.). | 3

196. CaucaLis (TorILIs) ANTHRISCUS, L. :—

Visitors : A. Diptera—(1) Gymnosoma rotundata, L., freq. B, Hymenop- —
tera—(a) Tenthredinide : (2) Tenthredo notha, Kl. (Tekl. B.) ; (b) Sphegida :
(3) Crabro vagus, L. 9; (4) Oxybelus bellicosus, Ol. ; (5) O. uniglumis, L., —
ab. ; (6) Ceropales maculata, F. ¢ 9, ab. ; (c) Vespide: (7) Odynerus pari- —
etum, L.; (d) Apidew: (8) Prosopis variegata, F. ¢. C. Lepidoptera—(9) —
Pieris rape, L. See also No, 590, 1.4 ~ EE

REVIEW OF THE UMBELLIFERA,

A survey of the Umbelliferee and their insect-guests proves —
most definitely that in flowers. otherwise constituted alike the
visitors vary in abundance and variety in proportion to the con-
spicuousness of the flowers. For our comparison we must naturally —
choose flowers that have been observed to much the same extent. —
If we select a number, eg. Agopodium, Carum, Pimpinella
Saxifraga, Heracleum, Torilis, Anthriscus silvestris, Daucus, and
Cherophyllum temulum, and arrange them in the order of con
spicuousness, this arrangement will not differ materially from tk
following, in which they are placed according to the number o

? The following additional species are discussed in my Alpenblumen ;—Bupleurum
stellatum, ls. ; Cherophyllum Villarsii, Koch. ; Gaya simplex, Gaud. ; Loserpiti
hirsutum, Lam. ; Mewm Mutellina, Girtn. ; Peucedanum Ostruthiwm, L. Lists o
visitors to the following are given in my Weitere Beobachtungen, pt. 1. ; thusu
Cynapium, L. ; Buplewrwm rotundifolium, L, ; Thysselinwm palustre, Hofim,

LN aT OBIS GN ANN I em

é

ART IIT. | THE MECHANISMS OF FLOWERS. 287

lifferent species of their insect-guests: 1. Heraclewm (118); 2.
Figopodium (104); 3. Anthriscus silvestris (73); 4. Daucus Carota
(61); 4. Carwm carui (55); 6. Cherophyllum temulum (23) and
Pimpinella Saxifraga (23); 7. Torilis (9).
Those insects which are most specialised for obtaining honey
e the least frequent visitors of Umbellifere. On most Umbel-
ifers butterflies are never seen, and on the others only rarely.
n cases where I saw them on several flowers one after another
mking their proboscides on to the fleshy disk, I have set them
own as sucking; but the point may be reserved whether they
eally can suck up honey off the flat surface, or were tearing the
isk with the sharp appendages of the proboscis and sucking the
uice set free, or whether they were only looking for honey
successfully.
_ We find on Umbellifers, on the one hand, the least specialised
genera of bees (Prosopis, Sphecodes, Halictus, Andrena) licking
he flat layer of honey or gathering pollen, and, on the other
hand, the most diligent forms (Apis, Bombus,) collecting pollen,
r more rarely sucking honey.
_ The odour of Umbellifers is shown to be of marked influence
n bees’ visits, as the strong-smelling umbels of Anethum graveolens
ted with special preference by the equally strong-smelling
decies of Prosopis. The great majority of the visitors of Umbellifers
fe Be ort-lipped flies, beetles, wasps, and other short-lipped insects
‘im immense variety. As a peculiarity which influences this
semblage of insects, I must mention the yellowish colour, for
have never found the flowers of Bupleurum, Silaus, or Pastinaca
isited by beetles. These seem to be mainly attracted to flowers
y bright colours.
_ Rare Umbellifers, confined to particular localities, have rare
| insects as their visitors.

Orv. ARALIACEZ.

Hedera, L., is proteranderous, according to Delpino, and is
fertilised by Biss (177). Ihave seen it visited also by beetles and

by praspe (590, 1).
Orv. CORNACE A.

197. CorRNUS SANGUINEA, L.—The fleshy ring surrounding
| the base of the style secretes honey, which, lying open on the flat

288 THE FERTILISATION OF FLOWERS. [PART I 1.

surface, is much more easily licked up by the tongues of short-_
lipped insects, or by the end-flaps (/abelle) of Diptera, than by :
the long proboscis of bees. I have never seen bees upon the —
flowers of C. sanguinea, although they may occasionally frequent —
them for the sake of pollen or even honey; but I have noticed —
many other insects licking the honey on these flowers. £
Since the anthers are developed at the same time as the
stigma, and since they open inwards and stand on a level with
it at a little distance, the insect, alighting on the flower and
bending its head down to the fleshy disk, generally touches the
stigma with one side of its head or body and one or two anther:
with the other; and so passing from flower to flower, and touchin
the stigma now with one side of its head now with the other,

Fie. 95.—Cornus sanguinea, L..

}

1.—Flower, from above.
2.—Ditto, in side view.

it produces cross-fertilisation, especially as in its movements it
touches anthers and stigmas with its legs or the underside of its
body. Only the smaller insects (Witidulide, Byturus, small Diptera)
which creep about irregularly in the flowers can occasion sel
fertilisation also. In default of insect-visits, pollination, and evel
cross-pollination, may here and there occur by the stigma acci-
dentally touching an anther of a neighbouring flower.

Visitors : A. Coleoptera—(a) Nitidulide : (1) Thalycra sericea, Er.; (2) Me ;
gethes ; (b) Dermestide : (3) we ibe fumatus, F.; (¢) Llateride : (4) Dolopius
ees .; (5) Athous niger, L.; (d) Curculionide: (6) Otiorhynchus
picipes, F. ; (e) Cer apps ere (7) Strangalia atra, F. ; (8) Str. armata, Hbst. ;
(9) Str. attenuate, L .; (10) Grammoptera lurida, F. ; (11) Gr. levis, F.; (fF)
Malacodermata : a”) Telephorus pellucidus, F. B. Diptera—(a) Empide:
(13) Empis livida, L. ; (6) (14) a small midge in very great numbers. ©

Hymenoptera—Sphegide : (15) Pompilus sp. ; all the visitors were licki
honey on the fleshy disk. See also No. 590, 11.

antun] THE MECHANISMS OF FLOWERS. — 289

Orv. CAPRIFOLIACE 2.

- 198. Apoxa MoscuaTELiina, L.—The flat, exposed layer of
1oney limits or prevents the visits of long-tongued insects, while
he greenish-yellow colour of the flowers must cause them to
smain unnoticed by most flower-haunting Coleoptera. As in
ther flowers of a similar colour and displaying their honey in a
imilar way, the visitors are exclusively or almost exclusively
iptera and Hymenoptera, which in this case are specially
tracted by the» musky smell. The honey is secreted by a
eshy ring surrounding the bases of the stamens. The stamens

rq

Kh

1

Fic. 96.—Adoxa Moschatellina, L.

-1.—Apical flower, from above (x 34).

2.—Ditto, from below.

ate : flower, not yet mature, unfolded artificially; the style is still bent down; viewed -
1 nt.

4.—Ditto, from behind.

5,—Lobe of the corolla, with two (divided) stamens (x 7).

§.—Stigma of the apical flower, from the side (x 7).

a, anther, not yet dehisced ; a’, ditto, after dehiscence : s, sepal; p, petals of the apical flower ;
uperior, p*, inferior, p3, lateral, petals of a lateral flower ; st, stigma; ov, ovary; n, nectary.

e each split into two halves, and their pollen-covered surfaces
e directed upwards in the terminal flowers, and outwards in the
eral flowers. Insects crawling over the small inflorescence
ing their feet and proboscides in contact now with anthers now
with stigma, and effect cross-fertilisation as in the case of the
| Guelder-rose and Elder (cf. Ricca, No. 665).

_ After my M.S. was finished I found a patch of Adoxa visited rather
abundantly by small insects one sunny afternoon (April 7, 1872). I caught
fifty-two examples of the following species. A. Diptera—(a) Muscide : (1)
Borborus niger, Mgn., 2 specimens ; (b) Mycetophilide : (2) various species
U

290 THE FERTILISATION OF FLOWERS. [PART II,

14—4 mm. long., 11 specimens; (c) Simulidw: (3) Simulia sp., 14 speci-
mens ; (d) Cecidomyide : (4) various species, 10 specimens. B. Hymenoptera— _—
(a) Pteromalini: (5) Eulophus, ¢, 1 specimen; (6) seven other species, —
9 specimens; (b) Ichneumonide: (7) Pezomachus, Gray., two species, 2 spe- —
cimens. ©, Coleoptera—Curculionide: (8) Apion columbinum, Grm., 3 _
specimens. Many of these small guests scrambled over the inflorescence, others

flew from flower to flower ; all licked the thin layer of honey, and none were —
feeding on the pollen. .

199. Sampucus NicRA, L.—I have never found honey in the
flowers. The relative positions of the essential organs are as in
the following species, save that the stamens diverge still more |
widely. Many flowers are aggregated together, and the corymb—
is here so large and conspicuous that enlargement of the marginal
flowers is unnecessary. The flowers are much less visited by
insects than those of the Guelder-rose, and I have never found :
pollen-collecting bees upon them. It would be premature

A ep arent y edire~ttt adaiiabamee hse

Fig. 97.—Sambucus nigra, L.

1.—Flower, from the front.
2.—Ditto, obliquely from the front and side.
8.—Ditto, obliquely from behind. (x 3.)

conclude from this that the strong scent of the flowers
distasteful to bees, for I have frequently found bees, and even the
hive-bee, visiting Ruta graveolens, in regard to which Delpino
advanced the same opinion. Fertilisation is effected in the
same way as in the previous species; but as cross-fertilisation
is less perfectly insured, self-fertilisation takes place much more
freely, pollen falling directly wpon the stigma in many flowers. —

Visitors : A. Diptera—(a) Stratiomyide : (1) Sargus poe L.; (i

Sy vere (2) Eristalis arbustorum, L. ; (3) E. nemorum, L. ; (4) E. tenax
L.; (5) E. horticola, Mgn. (Sld.) ; (6) Volucella pellucens, L., all: f.p.
Coleoptera—Lumellicornia: (7) Cetonia aurata, L. (Sld.) ; (8) Trichiu
fasciatus, L., both of these beetles feed on the petals and other parts of th
flower, and an therefore more destructive than useful. See also No. 590, {

Sambucus Ebulus, u—The flowers are visited on the Alps b,
hive-bees, humble-bees, and Syrphidee (Volweella) (609, Pp: aoe
in Low Germany by Diptera (590, III.).

arr] THE MECHANISMS OF FLOWERS. 291

200. VinurNuM OpuLus, L.—The flowers are aggregated in a
at corymb, whose marginal flowers have the petals greatly enlarged
at the expense of the essential organs. They thus attain conspicuous-
1ess, useless to themselves, but of the highest importance to the
community, as Sprengel correctly explained (702, p. 159). When
1e flowers expand (Fig. 98, 2) the anthers have already begun to
lehisce, and the stigmas are already so far developed that if pollen
e applied to them it adheres easily and in large amount. Shortly
terwards the anthers become covered all round with pollen, and
rotrude, diverging, from the flower, while the stigmas remain in
ie base of the flower close above the ovary, whose upper surface
‘secretes honey. The honey is fully exposed, and forms a flat,
‘adherent layer, so that it is only attractive to flies and other

Fic. 98,—Viburnum Opulus, L.

‘ —Marginal flower, from above, showing rudimentary pistil and stamens (x 24).
2.—Fertile flower, soon after expansion (x. 42).
8.—Ditto, after removal of the anterior part of the corolla and stamens (x 4%).

ort-lipped insects; the pollen attracts both flies and pollen-
lecting bees; the white colour of the flowers makes them
tractive to beetles, some of which are very destructive visitors.
e most frequent visitors and the most efficient fertilisers are
0 those which get most benefit from the flowers, viz. flies,
hich by turns suck honey and feed on pollen. As each flower
contains a very small amount of honey, the insects rapidly
a; the corymb; and they repeatedly effect fertilisation,
which is usually cross-fertilisation, since in each flower anthers
d stigmas generally come in contact with different parts of the
sect’s feet or proboscis. In absence of insects, self-fertilisation is
not impossible, for, in spite of the divergence of the stamens, the
igma comes to lie in many flowers immediately below an anther.
U2

292 THE FERTILISATION OF FLOWERS. [PART m0

Visitors : as ene sho gi : (1) Eristalis ae L.3
E. nemorum, L.; (3) E. sepuleralis, L.; (4) E. tenax, L.; (5) pee Fi
floreus, L. ; (6) H. pendulus, L., all ab., s. pee f.p. ; (bd) Musidas (7) Echino-
myia fera, L. B. Hyincnovters —Apete ; (8) Halictus sexnotatus, K., ¢, f
©. Coleoptera—(a) Nitidulide : (9) Meligethes, ab. ; (6) Lamellicornia : (10) .
Phyllopertha horticola, L., feeding on the petals and other parts of the flow
See also No. 590, II.

201, SYMPHORICARPOS RACEMOSUS, Michx.—The flowers of th
Snowberry seem to be specially adapted for wasps, like those of
Scrophularia. The corolla is pendulous, bell-shaped, and of —
reddish colour, 7 to 8 mm. long and 5 mm. wide, cleft nearly ©
the middle into five lobes. A wasp’s head (5 mm. broad, 2 to 25
mm. thick) can be conveniently accommodated in it, and in point
of fact, wasps, in places where they are abundant, are the mo. 3
numerous visitors of this plant. The
wasp hangs below the flower, thrusting
in its head and licking the honey which
is secreted very abundantly by the fleshy
swelling at the base of the style. The
-honey collects in the base of the flower
and on the inner wall of its dilated lowe
portion ; it is prevented from flowing ou

Fic. 99.—Symphoricarpos
racemosus, Michx. (2$.) by long close hairs upon the five lobes o

1—Flower, viewed from theside. the corolla extending inwards to th

2.—Ditto, in section.
centre of the flower, and protected fror

rain both by these hairs and by the obliquely age positio
of the flower. ;
In the lowest part of the hairy lining, viz. that neares
the mouth of the flower, are the five anthers, which dehise sc
introrsely and converge towards the centre of the flower; th
filarnents are attached to the corolla near its middle. Immediatel
above the hairs, in the middle of the flower, stands the stigms
which ripens at the same time as the anthers. As the wasp thru 4
its head wholly into the flower, it comes at once in contact y
all five anthers and then touches with one side the stigma ; but ©
its way to the stigma little or no pollen remains attached to it, par
because the pollen is very slightly adhesive, and partly because a
grains that do attach themselves are brushed off before :
reach the stigma by the hairs lining the corolla, It is only wh
being withdrawn moistened with hone y that the insect’s head acqui
a plentiful coating of pollen to be carried to the stigma of the ne:
flower. Thus, in case of wasps’ visits, cross-fertilisation is insurec

i
f

erin] § THE MECHANISMS OF FLOWERS. 293

| absence of insects, self-fertilisation cannot well occur owing to
2 relative positions of anthers and stigma.

) “Visitor: Hymenoptera—(a) Vespide : (1) Vespa holsatica, F.; (2) V
edia, Degeer ; (3) V. saxonica, F. ; (4) V. rufa, L. ; (5) Polistes gallica, L.
| var. diadema ; in Thuringia these five species make nine-tenths of all the
Store ; in Lippstadt, where wasps are much less abundant and Polistes does
yt occur, the honey-bee preponderates ; (6) Odynerus sp., bit holes in the
rolla and introduced its head ; (b) Apidw: (7) Apis mellifica, L. 2, ab. ; (8)
pmbus agrorum, F. 8; (9) B. pratorum, L. §; (10) B. muscorum, F. 8, all
e species scarce ; (11) Eucera longicornis, L. ¢; (12) Megachile centun-
E is, K. g, alls. ; (3) Halictus sexnotatus, K. 9,s. and c.p. ; (c) Sphegide :
}) Ammophila sabulosa, L., s. See also No. 590, 111.

Linnea borealis, Gron.—The position of the flower shelters the
mey from rain, and hairs on the interior of the corolla exclude
any small insects. Five purple lines on the interior of the
rolla and a patch of orange colour on its inferior side, near the
se, act as honey-guides. Cross-fertilisation is favoured by the
sition of the stigma in advance of the anthers (600, Fig. 158).

Fic. 100.—Lonicera Caprifolium, L.

1.—Flower, from the side. Nat. size. The figure should be horizontal.
2.—Ditto, from the front.

202 Lonicera Capriroiium, L.—The flowers are adapted for
tilisation exclusively by long-tongued crepuscular and nocturnal
pidoptera They bloom at the season when hawk-moths are

&

294 THE FERTILISATION OF FLOWERS. [parr nr

most abundant (May, June), they expand and exhale their
perfume most strongly in the evening, and they conceal their
honey in so long and narrow a tube that Lepidoptera alone of our
native insects are able to reach it. The tube, whose inferior fleshy
part secretes honey along its middle line, is about 30 mm. long,
and for the greater part of its length only 1 to 2 mm. wide, and |
still further narrowed by the style; while the longest proboscides |
among our native bees measure 21 mm. (Bombus hortorum and
Anthophora pilipes), and among our flies only 11 to 12 mm,
(Rhingia, Bombylius discolor). Certainly the tube becomes filled
to past the middle with honey so that even insects with a proboscis
15 mm. long can reach part of it; but this depth of honey is only
attained in the evening, when heed and flies have ceased to seek
their food. I have never seen bees or flies sucking on this honey-
suckle ; and it is all the more plentifully visited by ; hawk-moths on
the warm, calm evenings of May and June. I ite on a single
plant on May 27 and 29, 1868 :—

Lepidoptera—(a) Sphingide : (1) Sphinx convolvuli, L. (65—80), 2 speci-
mens ; (2) S. ligustri, L. (837—42), 6 specimens ; (3) S. pinastri, L. (28—33),
5 specimens ; (4) Deilephila elpenor, L. (20—24), 17 specimens; (5) D
porcellus, L. (20), 1 specimen ; (6), Smerinthus tiliz, L. (23), 1 specimen ;
(b) Noctue: (7) Diantheecia capsincola, 8. V. (23—25), 2 specimens ; (8)
Cucullia umbratica, L. ¢ (18—22), 2 specimens ; (9) Plusia gamma, L. (15)
1 specimen ; (ce) Bombyces: (10) Dasychira pudibunda, L. (0), 1 specimer

Smerinthus tilie and Dasychira pudibunda which have com-
pletely aborted proboscides were doubtless attracted by the sme
only, without having anything to gain from the plant; Plusi
gamma might sip a little honey from untouched flowers, and the
four preceding species might drink deeply, but only the first three
could drain the honey. I examined the specimens I had collecte
not only with reference to the length of their tongues but alse
with reference to the extent to which they were dusted with
pollen. In all (except the two last short-lipped species), at leas
the hairs upon the palps which cover the base of the proboscis
were richly covered with pollen; and in several of the largei
species the hairs and scales on the whole of the under side of the
body from the head to the middle of the abdomen, including the
proboscis, antenne, legs, and wings, were thickly dusted. The
most richly coated were individuals of the first three Sphingide
which had flown violently away, while Dianthecia, Cucullia, anc
Plusia were the least so. The pollen-grains are rounded tetrahedre
‘047 mm. in diameter; they adhere to the hairs and scales of the

arr] ‘THE MECHANISMS OF FLOWERS. 295

msect and afterwards to the stigma by their sticky surface, and
by the aid of small, sharp processes with which they are thickly
covered.

The visits of the above-named Lepidoptera result, in spite of
he simultaneous development of anthers and stigma, regularly in
sross-fertilisation, in consequence of the position of the stigma in
\dvance of the anthers. The stamens project about 15 to 18 mm.
nd the style about 25 mm. beyond the mouth of the flower; both
re slightly curved upwards at their ends, and the pollen-covered
aces of the anthers are turned upwards, Lepidoptera, whether
hey alight, or suck the honey while. poised in the air, must
touch first the stigma and then the anthers with their ventral
surfaces. |
_ On warm, calm evenings, insect-visits are so abundant that on
he following day all the flowers are found to have had their pollen
mtirely removed. On the other hand, on days following cool,
vindy evenings, the flowers display abundant pollen, which is then
rathered by bees and flies.

- On such days I have found the honey-bee and Halictus
eanotatus, K. 2, busy ‘collecting, and several Syrphide, Yylota
wy quis, L., Rhingia rostrata, L., and Syrphus ochrostoma, Zett., busy
eding on the pollen which remained upon the anthers. These
Boondary visitors occasionally effect fertilisation, but they must
orm self-fertilisation as readily as cross-fertilisation, and at any
ate the flower has not been adapted for them.

— Lonicera cerulea, L.—The yellowish-white flowers are adapted
_ for humble-bees, by which they are chiefly visited and fertilised.
__ The tube is over 10 mm. long and pendulous. The stigma stands
ell in advance of the anthers, favouring cross-fertilisation ; but in
he absence of insects, pollen may easily fall on the stigma and
fect self-fertilisation (609).

| ionicerc Periclymenum, L.—The general structure of the flower
es embles that of LZ. Caprifoliwm, and the plant is visited and fer-
4 ed by the same hawk-moths. The tube, however, is only
2 to 25 mm. long, so: that the honey as soon as it has collected
| 0 the depth of a few millimetres is accessible to many of our bees.
On July 17, 1867, I saw Bombus hortorum, L. 2 (21 mm.), sucking
honey from some flowers of L. Periclymenum. The bee wasted
considerable time in obtaining a convenient position for sucking,
and it crawled from the broad upper lip to the mouth of the tube
: w without touching the stigma and anthers; and the amount of
ney it obtained must have been small, fos after visiting a few ©

—

296 THE FERTILISATION OF FLOWERS. [PART UT,

Fic. 101.—Lonicera cerulea, I.

A.—Pair of pendulous flowers (Xx 8).
B.—Flower in section (x 4).
(Bergiin, June 9, 1879.) rs

. 2 oa .
—_ - ”
oa 7 7
ee See DNS were é

Fia. 102,—Lonicera Periclymenum, L.

2.—A Hawk-moth (Sphingw Ligustri) sucking one of the flowers.

pe paca slit down the middle line superiorly, and laid open. n, nectary,
4.—Stigma.

5.—Bection of ovary.

6.—Ovary and calyx.

PART I11.] THE MECHANISMS OF FLOWERS. 297

flowers it flew away, though the plants were in full bloom. Bees,
therefore, are only accidental visitors, which have had no influence
in developing the special characters of the flower.

203. Lonicera TATARICA, L.—Honey is secreted and lodged in
the shallow pouch at the base of the tube, which is 6 to7 mm. long.
Stigma and anthers are matured simultaneously, and protrude from
the flower in close proximity with one another, the stigma being
slightly overtopped by the anthers. An insect-visitor inserts its
head between the anthers and stigma, and so dusts one side with
pollen while the other comes in contact with the stigma. The
flowers stand unsymmetrically in pairs, causing the insect’s head to
_ enter in various positions and so favouring cross-fertilisation. When
__ the stigma is thrust aside, its opposite side usually comes in contact
_ with those anthers which are not touched by the insect’s head, and
it thus becomes dusted simultaneously with the pollen of its own
_ flower. Flowers are frequently found in which the stigma is in
close contact with one or two anthers, and self-fertilisation doubtless
often takes place in absence of insects.

Visitors: A, Hymenoptera—Apide: (1) Apis mellifica, L. $,s., ab. ; (2)
Megachile centuncularis, L. ¢,s. ; (3) Andrena albicans, K. ?, ae in vain
to reach the honey. B. Diptera—Syrphide: (4) Rhingia rostrata, L., s. and
fip., very ab.

Lonicera nigra, L.—This species is adapted for bees, which alight
not on the under lip, which is bent backwards out of the way, but
on the style and stamens. The flowers are homogamous. The
Stigma stands below the anthers, and in absence of insects
Self-fertilisation must occur (609, Fig. 159).
|
| q 204. LonicerRA XyLostEuM, L.—Honey is secreted and lodged
sin L. tatarica, but the tube is only 3to4mm. long. The anthers
. * stigma are matured simultaneously and project far beyond the
mouth of the flower ; the former are divergent and stand at a dis-
tance from the sigue Humble-bees thrust their heads some-
_ times to one side sometimes to the other, sometimes above some-
_ times below the anthers, and in the course of repeated visits they
_ dust their heads (or head and thorax) all round with pollen. In
_ €ach flower one side of the bee’s head touches the stigma and the
_ other the anthers, so that cross-fertilisation proceeds regularly. I

_ have never found flowers in which the anthers stood in immediate

1 See No. 590, 111. p. 75, fora case of atavism in this species.

298 THE FERTILISATION OF FLOWERS. [PART IIT.

contact with the stigma ; ; but in the absence of insects, self-
fertilisation may result in many flowers by — falling upon the
stigma.
Visitors : A. Hymenoptera—Apide : (1) Apis mellifica, L. §, very ab., 8. ;
(2) Bombus muscorum, F, §,s. ; (3) B. pratorum, L. §,s. B. Diptera—(a@)
Empide : (4) Empis opaca, F., s., ab. ; (6) Syrphide: (5) Rhingia rostrata, L.,
s. and f.p.

The chief fertilisers are humble-bees, since they never insert
their tongues into a flower without touching stigma and anthers —
with opposite sides of the head ; while flies and the honey-bee
never touch the stigma at all in many flowers.

Lonicera alpigena, L.—This ‘species is fertilised by bees and
humble-bees, and also still more frequently by wasps. It resembles”

Fig, 103.—Lonicera alpigena, Li.

A pair of recently expanded flowers (x 4). The flower on the right hand has an additional stamen.
(Bergiin, June 8, 1879.)

other wasp-fertilised flowers (Serophularia, Symphoricarpos, Epi-
pactis palustris) in having an expanded pouch-like honey-receptacle
containing an unusually large supply of honey, and it is just wide
enough to admit a wasp’s head easily. The flower is reddish-brown
in colour, like that of Scrophularia (609).

SI Se mae Sh Tlie

parvum] § THE MECHANISMS OF FLOWERS. 299

| Weigelia (Diervilla) rosea, L.—The flower is adapted for bees,
and undergoes a change of colour after fertilisation like Ribes
aurewm (590, III.).

REVIEW OF THE CAPRIFOLIACEX.

The small group of Caprifoliacew is remarkable for the great
variety of visitor’ to which nearly related plants have adapted
_ themselves, chiefly by differences in the length of the tube.
Lonicera Caprifolium, L., with a tube about 30 mm. long, permits
_ only a few Lepidoptera to reach the honey; LZ. Periclymenum, L.,
_ in which the tube is only 20 mm. long, admits also a few specially
_ long-tongued bees ; LZ. cwrulea, L., with a pendulous corolla and a
_ tube over 10 mm. long, is adapted for humble-bees ; in Z. tatarica,
| L,, and L. Xylostewm, L., the length of the tube falls to 7 to 3 mm,
and certain long-tongued flies, in addition to a larger company
_ of bees, visit and fertilise the flowers; the short, wide honey-
_ receptacles of Symphoricarpos and Ledasione alpigena, L., are easily
accessible even to wasps, which are attracted in great numbers by

the large supply of honey ; Linnea is farnished with an infundi-
-buliform corolla, but apparently attracts, for the most part, flies ; in

Viburnum the honey is freely exposed, but only as a flat, adherent

layer, and the plant is visited chiefly by short-lipped insects, e.g.
flies and beetles; Sambucus attracts a similar set of insects, which
are less varied and fewer in number owing to the absence of
honey; Adoxa attracts only minute honey-seeking insects. In
case of insect-visits, cross-fertilisation is insured in all, but in very
_ various ways; self-fertilisation in the absence of insects is rendered
possible in those species which are least visited. In the least
; specialised and most generally accessible Caprifoliaceze (Adoxa,
i Sambucus, &c.) the flowers are white or greenish; in those species
fertilised by wasps they are reddish (Symphoricarpos) or reddish-
‘ brown (Lonicera alpigena, L.); in several species of Lonicera fer-
tilised by bees (eg. Z. tatarica) they are bright red, in LZ. cwrulea
_ they are yellowish-white, but they are pale in those species which
have the longest tubes and are adapted for crepuscular Lepidoptera
(L. Perichymenaini, L. Caprifolium).

300 THE FERTILISATION OF FLOWERS. [parr mt.

Orv. RUBIACE 4.

205. Gatrum Mot.uco, L.—A fleshy disk lying upon the ova:
and surrounding the base of the style secretes honey, but in s ch
small amount that it remains adhering in a very thin layer to a
disk. In young flowers (Fig. 104, 1) the anthers stand erect and are
covered all round with pollen, while the two stigmas as ie lie
close together. Afterwards the stamens spread out horizonta.
and finally their ends curve downwards between the petals outside
the flower, while at the same time the two styles diverge (Fig. 104, 2 :
The stigmatic papillae seem to be as well developed in the fi st
period as in the second, and are not unfrequently covered witl
pollen while the stigmas still stand close together. The movement

Fic. 104.—Galium Mollugo, L.

1.—Young flower, with stamens and styles erect.
2—Older ditto. The stamens are bent out of the flower, and the styles have sa
8.—Centre of the flower, from above, more magnified.

a, two stigmas ; b, fleshy disk above the ovary.

of the stamens seems therefore not to be accompanied by dichog am i
but to be the sole contrivance to prevent self-fertilisation and,
case of insect-visits, to insure cross-fertilisation. 7
The thin layer of honey can scarcely tempt long-tongued ins
to repeated visits. The colour of the flowers oe llowishamal in
the bud and in the young flower, becoming purer white afterwards,
—seems to repel all those insects, e.g. beetles, which are only
attracted by bright colours. In this relation a comparison of t
insect-visitors of G. Mollugo and G. verwm is instructive. a
In this and the following species of Galiwm the pollen is con-
veyed to the stigma chiefly by the feet and, in a less degree, by by
the proboscides of insects creeping over the inflorescence, ao

Visitors : A. Diptera—(a) Stratiomyide : (1) Odontomyia viridula, F., Lh,
not rare ; (b) Bombylide: (2) Anthrax flava, Hffs. (Thur.), do. ; (8) Syste-
chus sulfureus, Mik. (Thur., Sld.), s., probably boring into the nectary ; (c )
Syrphide ; (4) Syritta pipiens, L., ab., s. and f.p.; (5) Syrphus ribesii, L., 8

ae

oak a seh r. ae * 02

PART U1. | THE MECHANISMS OF FLOWERS. 301

and f.p., not rare; (d) Muscide: (6) Musca corvina, F.; (7) Scatophaga

merdaria, F., s. ; (e) Tipulide : (8) Pachyrrhina crocata, L.,s. B. Hymenoptera

—-Sphegide: (9) Ammophila sabulosa, L. 9, once only,—I could not see
whether it gained anything from the flowers. See also No. 590, 111.

Galium silvestre, Poll—This species resembles G. Mollugo in

_ the mechanism of its flower; it is frequented on the Alps by
_ Syrphidz and by numerous Lepidoptera (No. 609, Fig. 156).

206. GALIUM vErUM, L.—The structure of the flower agrees

; closely with that of G. Mollugo. Different individuals show a very
_ marked difference in the size of their flowers (Fig. 105, 1—4) ; but
_ since the flowers are rendered conspicuous merely by aggregation,
a diminution in their size does not diminish the number of
insect-visitors so seriously as it does in most cases. The apparently
unimportant circumstance that the flowers are bright yellow, and

Fic. 105.—Galium verum, L.

1.—Young flower, of a small-flowered plant (x 7). The anthers are erect, and covered with

' pe: the stigma is not yet mature.

2.—Older flower, of the same plant. The shrivelled anthers are bent out of the flower ;*the

oe are mature and divergent.

3.—F lower, of a large-flowered plant; older than 1, but younger than 2 (x 7).
4.— Ditto, from the side.

not yellowish-white as in G. Mollugo, leads to the plant being
visited by Coleoptera in addition to the other orders.

G. verwm is very scarce near Lippstadt, and I have only
watched its flowers once or twice in Thuringia and in Sauerland, so
I have not obtained a long list of insect-visitors.

A. Diptera—(a) Conopide : (1) Conops flavipes, L. (Sld.) ; (6) Muscide :
_ (2) Ulidia erythrophthalma, Mgn., ab., 1-h.(Th.). B. Soleo sters—{a) Lamelli-
cornia : (3) Cetonia aurata, L., ab. (Th, ; ; (b) Elateride: (4) Agriotes gallicus,
lap, (Th.) ; (c) Mordellide : "(5) Mordella fasciata, F. (Th.) ; (6) M. oe

L, (Th.). C. Hymenoptera—Tenthredinide : (7) Tenthredo rape, K. (Sld.).
See also No. 590, II.

Galiwm boreale, L.—This species agrees with G. silvestre in regard
to the position of its honey, its imperfect proterandry, the relative
Positions of stamens and pistil, and therefore also in the probability
‘of cross-fertilisation in case of insect-visits, and the possibility of
self-fertilisation in absence of insects ( 590, 609).

302 THE FERTILISATION OF FLOWERS. | PART III,

Galium boreale, L., palustre, L., and uliginosum, L., are all stated
by Axell to be proterandrous (17).

Galium tricorne, With.—Honey is abundant, but the small
isolated flowers are very inconspicuous and very little visited.
They cannot dispense with the power of self-fertilisation, which
takes place regularly, as the stamens do not curve outwards till
they wither (590, 111.).

207. ASPERULA CYNANCHICA, L.—Honey is secreted, as in
Galium, by a fleshy ring surrounding the base of the style, but it
exists not as a smooth adherent layer but filling up the base of the
tube ; the latter is 2mm. long. Anthers and stigmas mature sim-
ultaneously. The two stigmas stand close together in the middle of

Fic. 106.—Asperula cynanchica, L.

1.—Flower, with smooth white petals, from above (x 7).
2.—Ditto, after removal of half of the corolla.

3.—Ditto, with rough petals, marked with red lines.

4. —Ditto, from above.

ov, ovary ; », nectary; st, stigma; a, anther.

the tube; the anthers converge towards one another in the throat of
the corolla. In case of insect-visits, cross-fertilisation is favoured
by this condition only, that in consequence of the convergence of
the anthers the proboscis of an insect-visitor is less readily dusted
with pollen in entering a flower than in being drawn out, and also
that the proboscis usually comes in contact with pollen on one side
only and rubs the stigma with the opposite side (cf. J/yosotis).
In absence of insects, self-fertilisation occurs by part of the pollen
falling on the stigma. On sunny slopes in Thuringia (Miihlberg, near
Erfurt) I found this species bearing two different forms of flowers.
Many plants had smooth, white, somewhat obtuse petals (Fig. 106,

1 The following additional species of Golium are discussed in No, 590, lI. : G.
savatile, L. ; G. stlvatiewm, L,

santut.] THE MECHANISMS OF FLOWERS. 303

1, 2); on other plants, the petals were rough on the upper
‘surface, marked with a red elliptic line, and with another red
line traversing the long axis of the ellipse, and were produced at
the end into a slightly recurved point.

Visitors: A. Hymenoptera—Apide: (1) Bombus muscorum, F. § (Thur.,
July 8, 1872),s, B. Diptera—Bombylide: (2) Systechus sulfureus, Mik.,
s. (Thur., July 14, 1868). Additional visitors (four beetles, six flies, two Lepid-
optera) are enumerated in No. 590, 11.

- Fic, 107.—Asperula taurina, L.

-—Herma peatise flower, from the side.

.—Pistil o P the same flower, with nectary.

x ae hrodite flower, with the lobe of the corolla revolute, the stigmas more exserted, and
r papille: obvious.

ah age flower, whose stigmas overtop the black shrivelled anthers on which a few pollen-grains
-E.—Half-withered flower, in which the styles project still further.
_ F —Abortive pistil of a male flower.

_ G.—Male flower, with three teeth, from the side. (x 7.)

a _ (Churwalden, May 31, 1879.)

a Asperula taurina, L.—This plant is adapted for nocturnal
Lepidoptera by its white colour, and by its long, narrow tube,

304 THE FERTILISATION OF FLOWERS. [PART III,

9 to 11 mm. long. The plant is andromonecious, and the herma- —
phrodite flowers are markedly proterandrous (609). f
Asperula azurea is adapted for diurnal Lepidoptera (590, 111).
Asperula odorata, L.—In the structure of the flower and the —
length of the tube this species closely resembles A. cynanchica. —
The hive-bee is a frequent visitor. Additional visitors (four beetles, —
four flies, one moth) are enumerated in No. 590, III.

Sherardia arvensis, L., is gynodicecious (590, IIL, 605).

Manettia, Mut., is very diligently visited by humming-birds in ©
South Brazil (360).

Caffea arabica, L., according to Bernouilli,* produces in Guate-
mala, at the bootinibie of the season, small pistillate fertile flowers. —
Prof. Ernst was unable to discover these small flowers at Caracas” :

224 cs
. een Te species of Borreria, Hedyotis, and Manettia are dimor-
phic (Fritz Miiller, 353); Hedyotes had already been il to be ©
dimorphic by Treviranus (742). F

Mitchella, Knoxia, and Cinchona are dimorphic eae to
Darwin (154, 167). | :

Chasalia, Nertera, Ophiorrhiza, and Luculia are dimorphic *
according to Kuhn (399). %

Other heterostyled Rubiacez are. mentioned by Darwin in his
Forms of Flowers, where he also discusses the passage from
heterostyly to diecism in this order.

Faramea, Aubl.—My brother Fritz Miiller (554) gives an account
of a dimorphic species of this genus, which is of interest in several —
respects. (1) It affords the only known instance of a striking dif-
ference in the character of the surface of the two kinds of pollen-
grains. The smaller pollen-grains, which are produced in the
long-styled flowers (whose anthers are inclosed in the tube), are
smooth ; the larger pollen-grains of the exserted anthers of the
short-styled flowers are covered with short, rather close points,
which prevent their being dispersed by a puff of wind. The pollen
of the long-styled flowers, lying low down in the corolla, is in no
danger of being blown away. (2) In the short-styled form the
stamens twist round upon their axes, so as to turn their pollen-
covered faces outwards. The short stamens (of the long-styled
flowers) do not rotate but dehisce on their inner sides ; and in both —
cases the pollen is thus placed in the best position for adhering to
an insect’s proboscis when inserted in the flower. But it is a
very remarkable fact that this faculty of rotation is by no means

1 Bot, Zeitung, 1869, p. 17.

parti) THE MECHANISMS OF FLOWERS. 305

perfect, for many of the long stamens do not twist properly, and
to a great extent waste their pollen.
Posoqueria (Martha) fragrans, Roxb. has been described by my
_ brother Fritz Miiller (549).? It affords a most remarkable example
_of adaptation to Sphingidz. The white colour of the flowers, their
strong perfume, the long, narrow tube 11 to 14 em. long, all point
it out as such. The abundant honey at the base of the tube can
only be reached by the tongues of Sphingidew; and only these
insects, ¢.g., S. rustica, L., whose proboscis is 15 mm. long, have
been seen to visit the flower (F. Miiller, Oct. 1873).
_ The five exserted anthers are united into an oval knob directed
obliquely downwards and containing the loosely coherent pollen
which escaped from the anthers before the expansion of the flower.
The filament of the inferior stamen possesses a very great elastic
tension acting upwards, those of the superior and lateral stamens
have a similar tension outwards. The insect’s proboscis has only
one available point at which to enter the flower, and when in doing
so it touches one of the superior stamens at a certain spot the
tension of the filaments is released. "The inferior stamen springs
up with such violence that it hurls the loosely coherent pollen
against the insect’s proboscis at an angle of 50° with the tube of
the corolla, and with an initial velocity of about 3 mm. per
Second ; at the same time it closes the entrance of the tube. The
superior and lateral stamens spring at the same time to the sides,
the empty anthers of a superior and a lateral stamen remaining
coherent on either side. About twelve hours afterwards the
inferior stamen extends itself again and leaves the entrance to the
honey open once more. If a hawk-moth, after exploding a flower
in the male stage, comes to one in the stage under consideration,
it is repaid for its startling reception in the former case by a rich
supply of honey ; and in thrusting its pollen- -dusted proboscis down
(0 the base of the flower it brings it in contact with the stigma
which stands in the middle of the tube.
_ My brother, in his paper on Faramea (554), refers again to
f = osoqueria, and points out that most of the flowers (whose only
: fertilisers are abroad in the evening) open towards evening, but
% that a considerable number open at various hours of the day,
ractimes even in early morning, and that these are exploded
by diurnal insects which cannot effect fertilisation. This is

1 4a Grifuuhia Fragrans, W. A.

__ ? Darwin wrote tome: ‘ Your brother s paper on Martha i is, I think, one of the -
, 4 ost wonderful ever written.’

4 x

ae.

306 THE FERTILISATION OF FLOWERS. [PART II.

another interesting case of an adaptive modification imperfectly —
attained. ?
The Rubiacez include more dimorphic (heterostyled) genera t
than any other order. Darwin (167) discusses many of these
cases, enumerating seventeen dimorphic genera, in addition to which
Chasalia, Commers., Ophiorrhiza, L., and Luculia, Sweet, are men-
tioned by Kuhn (399). Darwin discusses the probable transition —
from heterostylism to dicecism in Rubiaceze. Mitchella, L., which is |
normally heterostyled, is in some places dicecious (Meehan, 465). ®
Asperula scoparia, Hook., and A. pusilla, Hook., two Tasmanian —
species, were stated by Treviranus (742) to be dimorphic, but |
according to Darwin the former at any rate is dicecious. Our own :
Asperula taurina, L., and Galium cruciatum, With., are both —
andromoneecious, and Sher ardia arvensis, L,, 1S pvndédicecions (605).

Te
(at: <

Orv. VALERIANE 4.

Delpino in his work on the Artemisiacez rightly insists that the
calyx in Composite could only become transformed into a pappus
after the involucral bracts had assumed the usual functions of a
calyx ; and he considers the Valerianes to be offshoots of the Com-
positze, which have in part retained this hereditary development of —
a pappus, and in part have acquired other means of dissemination
of the seeds by the wind. .

208, VALERIANA OFFICINALIS, L.1 is distinctly proterandrous. — .
The florets, in spite of their small size, are rendered conspicuous by.
aggregation. In each floret the tube is 4 to 5 mm. long, and half
a millimetre from the base is a small pouch with a green, fleshy
floor, which secretes and lodges the honey; this is accessible to _
numerous insects with moderately short proboscides, especially as
the tube widens above to a diameter of 2mm, Insect-visits are”
numerous and various, and the well-marked dichogamy ensures —
cross-fertilisation in case of insect-visits. In the first period the
anthers, covered all round with pollen, in the second the three out-
spread stigmas, project freely from the flower, and are touched by —
the feet and under surfaces of insects creeping over the inflorescence
and by the heads of insects sucking honey from the florets; in the
second period the anthers are bent away outside the floret. I
have never seen florets which fertilised themselves ; stigmas which

* Compare Sprengel, No. 702, pp. 63-65.

PART III. | THE MECHANISMS OF FLOWERS. 307

| ~ come in contact with the anthers of neighbouring flowers are, on the
_ other hand, not uncommon.

ah Visitors : A. Hymenoptera—Apide: (1) Apis mellifica, L. 8, ab.; (2)
F Bombus pratorum, L. $, s.; (3) a small Halictus, 9 ¢,s. B. Diptera—(a)
' Tabanide: (4) Tabanus luridus, Pz. ; (b) Empide: (5) Empis livida, L. ; (6)
_ E. rustica, F., both species very ab., s. ; (c) Syrphide: (7) Eristalis nemorum,
_ L.; (8) E. arbustorum, L. ; (9) E. sepulcralis, L. ; (10) E. horticola, Mgn.
_ (Sid.) ; all four species ab., fp. ; (11) Volucella bombylans, L. ; (12) Helo-
_philus floreus, L. ; (13) H. pendulus, L. ; (14) Syritta pipiens, L. ; (15) Chry-
sotoxum festivum, L., all sometimes s., sometimes f.p; (d) Conopide: (16)
Sicus ferrugineus, L., s.; (e) Muscide: (17) Sarcophaga carnaria, L. ; (18)
- Onesia floralis, E. D. ; (19) Lucilia cornicina, F. ; (20) Musca domestica, L. ;
(21) Calliphora erythrocephala, Mgn. ; (22) C. vomitoria, L., all ab.,s. See
also No. 590, 11. I have found it visited on the Alps by one beetle, sixteen
species of Coleoptera, and fifteen Lepidoptera (609).

209. VALERIANA DIoIcA, L.'—Honey is secreted as in the
previous species, but cross-fertilisation is ensured not by dichogamy,
but by dicecism. The male flowers, being notably larger than the
_ female, are almost always visited first by the insect, .as I have
repeatedly observed. Sprengel insisted rightly that in this order
_ alone could the insect-visits be useful to the plant. _ In the male
florets the tube is 2} to 34 mm. long, widening above; in the
female it is only 1 mm. long, so that in both the honey is accessible
to insects with very short proboscides. The capitulum is much
less conspicuous than in J, officinalis, but the flowering period is
so early that the plant is exposed to much less competition. Insect-
visitors are less various than in the previous case, but still fairly
numerous. In this plant there are four kinds of individuals, with
four different kinds of flowers: (1) male flowers without any rudi-
- ment of a pistil, and with large corollas; (2) male flowers with
a rudimentary pistil, and a somewhat smaller corolla; (3) female
flowers with evident traces of anthers, and with still smaller corollas ;
(4) female flowers with scarcely visible traces of anthers, and with
_the smallest corollas of all (No. 584, p. 131).
Visitors : A. Hymenoptera—A pide : (1) Apis mellifica, L. $,s, very ab. ;
) Andrena albicans, K. 9, freq. B. Diptera—(a) Syrphiden - (3) Eristalis
| Seebustorum, L., s. ; (4) Rhingia rostrata, L., fp. ; (0) Tipulide : (5) Tipula,
“sp.,s. CO. Papldspters—Rkopalocera ; (6) Pieris napi, L.,s. D. Coleoptera—
| Nitidulide : (7) Meligethes, very ab. |

? AR
) Valeriana montana, L., is ; gynodicecious, some plants having

distinctly proterandrous, hermaphrodite flowers with a large corolla,

=. a> 1 Compare Sprengel, No. 702, pp. 65-67.
2 x 2

308 THE FERTILISATION OF FLOWERS. [PART 11.

a...

others having only female flowers with a small corolla. The latter —

retain their stamens in an apparently almost perfect form, but their
anthers do not contain a single grain of pollen (609).

Valeriana tripteris, L., is dicecious. In this species also there

are large-flowered and steaill- flowered plants, but the larger flowers
are not hermaphrodite as in V. montana, but male only; they
retain a style, but stigmatic papille are not developed (609).

These four species of Valeriana form an interesting series :— —
V. officinalis, with one kind of individual only, and proterandrous F

hermaphrodite flowers; V. montana, with large-flowered and small-
flowered individuals, the anthers in the latter being abortive ;
V. tripteris, in a similar condition, but with the pistil in the large-

flowered individuals rudimentary also; finally, V. dioica, also —

dicecious, but exhibiting four different nds of individuals (609).

Valeriana cordifolia, L., is distinctly proterogynous, according to —

Ricca (665).

Centranthus ruber, D.C., and Fedia cornucopia, are distinctly

proterandrous, according to Delpino (178).

| Valerianella olitoria, Much.—I have found this plant visited —
by four Coleoptera, eighteen Diptera, one Hemiptera, eleven Apidee, —

and two Lepidoptera (590, III).

Orv. DIPSACE.

Morina elegans.—The stigma is developed at the same time

as the anthers, but overtops them, so that insect-visitors touch first
the stigma and then the anthers, and usually effect cross-fertilisation.
In the absence of insects the stigma curls inwards so as to touch
the anthers and lead to self-fertilisation (356).

210. Dipsacus sILvEestRIs, L.—The tube is 9 to 11 mm. long;
the flower is markedly proterandrous; the style divides into two
branches, whose inner surfaces are closely covered with stigmatic
papillze, but one of which is always partly, and sometimes entirely,
aborted. The bracts stand up from the convex head as stiff, sharp

spines; they distinctly overtop the anthers and stigmas and pre-

vent them from being touched by the ventral surface of a bee
creeping over the inflorescence. The anthers and stigmas are only
touched by the bee’s head as it is inserted in the flower; and in
this process one stigma is in the way of the other, and the whole
stigmatic surface of one is much more thoroughly rubbed by the
bee’s head when the other is absent. We seem to have here in

PART 111. | THE MECHANISMS OF FLOWERS. 309

the abortion of one stigma an adaptive modification in progress
_ and not yet perfected. —

M (1) Bombus rupestris, L. 9 (12—14) ; (2) B. lapidarius, L. ¢-§ ? (8—14),
' ab., (¢ as late as October 2); (3) B. agrorum, F. § @ (12—15), all three
_ species sucking. See also No. 590, II.

211. ScaBiosA (KNAUTIA) ARVENSIS, L.—In fine weather the
flowers, owing to their great conspicuousness and their easily
accessible honey and pollen, are visited by very miscellaneous
‘insects in great numbers. Cross-fertilisation is ensured by markedly
_proterandrous dichogamy, and in the unlikely event of insect-visits
not taking place, self-fertilisation is very unlikely to occur.

Fic. 108.—Scabiosa arvensis, L.

1.—Hermaphrodite flower in first anes stage, after removal of one lobe of the corolla (x 34
2.—Ditto, in second (female) stag
3.—Female flower, after removal of one lobe of the corolla.

a, stigma; b, anther still within the flower; ¢, ditto, dehiscing ; d, ditto, empty and shrivelling
a re, abortive anther.

2

About fifty flowers unite in a capitulum which may be hemi-
_ Spherical or only slightly convex, and become gradually larger
_ from the centre to the margin by an increasing development of the
_ outer lobe of the corolla. While in the central florets the tube is
i= only 4 to 6 mm. long, and the lobes of the corolla, which are all
similar, only 3 to 4mm. long, in the marginal florets the tube is
_7 to 9 mm. long, the external lobe of the corolla 6 to 11 mm., each
of the two ical lobes 4 to 7 mm., and the internal lobe wale 3 to
4mm. long.

____Inpite of the length of the tube the honey is easily accessible
| toavery large number of insects of the most various orders ; for

310 THE FERTILISATION OF FLOWERS. [PART IIL.

the tube widens out superiorly, and the more so the longer it is, so
that many short-lipped insects can reach the honey by creeping a
greater or less distance down the tube. The honey is secreted by
the upper surface of the ovary, and is lodged in the base of the
tube; in spite of the funnel-shaped widening of the tube, it is
sheltered from rain by hairs lining the tube. The pollen also is
easily accessible, for the stamens, which are at first curled up in
the bud, straighten themselves after the flowers open and protrude
4 to 5 mm. beyond the tube, with the pollen-covered faces of the
anthers directed upwards. Thus the flower offers great attractions
to insects whether in quest of honey or of pollen, and all the more
that the close aggregation of the flowers prevents waste of time in
passing from one to another. Honey-seeking insects are induced
to make repeated visits to the same capitulum by the gradual
development of the florets and by the length of time during which
they secrete honey; pollen-seeking insects are led likewise to
repeat their visits, because the anthers in each flower do not
develop simultaneously but one by one (Fig. 108, 1, 3, ¢, d).

The style elongates after all the stamens have fully developed ;
its immature stigma stood previously in the mouth of the flower,
but now protrudes 4 to 5 mm. from the corolla and becomes

mature (a, 2). The empty anthers, if they have not been removed —

by the insects, as frequently happens, are retracted to the mouth
of the flower by the filaments shrivelling up (d, 2). In each
capitulum the florets open and the anthers develop in succession

from the circumference towards the centre; but the styles only —
begin to elongate and the stigmas to develop after all the stamens —

on the capitulum have completed their development, and then
almost simultaneously throughout the capitulum. Since here the

whole capitulum is at first male, and later, if insect-visits have —
taken place, wholly female, cross-fertilisation takes place regularly —
between separate capitula in case of insect-visits; and since all the —
stigmas on a capitulum develop simultaneously, while the anthers —
succeed each other very gradually, cross-fertilisation en masse may

be effected by a single insect’s visit, and the possibility of cross-

fertilisation is extended over a long period of time. So even a —

period of fine weather very short in comparison with the whole
flowering period of the plant may suffice for complete fertilisation
of the flowers.

Besides plants with hermaphrodite flowers, others occur whose
flowers all possess more or less aborted anthers which do not dehisce
and which contain small and often very deformed pollen-grains.

x

' ~~
Pee ee I I 6 Reger OA we Sk -

‘parrut] THE MECHANISMS OF FLOWERS. 311

ae if these female plants flowered earlier than the hermaphrodites,
i ‘so that their stigmas were mature cotemporaneously with the
anthers of the first hermaphrodites, then their origin might be
explained on the principle of economy, as a saving of the first
stamens which have no stigmas to fertilise. Ifthe female capitula
_ were less conspicuous than the others, the same explanation might
__ be applied in this case as I have put forward in describing Thymus
and Glechoma. But here neither the one fact nor the other is true ;
but the female heads are just as conspicuous as the others at:
develop cotemporaneously with them. I can only account for
_ their existence by the very great difference between the duration
of the stigmas in the hermaphrodite capitula and the length of
time that the anthers are covered with pollen.
It is of special importance for Scabiosa arvensis that the anthers
‘on the same head should develop gradually throughout several
days, and that the stigmas should ripen all on the same day, almost
simultaneously. For owing to the first character there is never a
, lack of pollen, and owing to the second, as soon as a few sunny
hours occur and bring out the insects, in a very short time all the
‘stigmas on a capitulum are fertilised with pollen from another.
_ Both characters together are therefore of use to the plant in the
changeable and often continuously rainy weather of our summers.
But when a spell of sunny weather appears the number of herma-
_ phrodite flowers in the male condition must always be much
eater than in the female condition; the pollen of many heads
must be wasted, and it must be an advantaxe to the plant if in
- some cases the stamens are aborted and the stigmas come so much
ra the quicker to maturity. As every character of advantage for the
maintenance of the species, which appears accidentally as an
abnormality, can and must be retained by natural selection, so in
| Scabiosa arvensis, abortion of the stamens, occurring accidentally
in certain plants, must have been perpetuated and intensified.
_ The power of self-fertilisation is not quite lost in the herma-
phrodite plants; for in capitula allowed to flower in the house and
LL eft untouched, many of the stigmas as they grow up may be seen
_ to come in contact with anthers still dusted with pollen. But as
» a rule insect-visits are so numerous that self-fertilisation can
_ only come into action in long-continued bad weather.
) : Visitors : A. Hymenoptera—(a) Apide: (1) Apis mellifica, L. § (6), ab.,
Sy more rarely c.p. ; (2) Bombus hortorum, L. g 9 9 (17—21) ; (8) B. terres
-: L. 2 ¢ (7—9) ; (4) B. lapidarius, L. § (10—12) ; (5) B. pratorum, L.

312 THE FERTILISATION OF FLOWERS. [part a

2 9 g (8—11) ; (6) B. enki Ill. ¢ (10) ; (7) B. agrorum, F. 2 (12—15) if
(8) B. hypnorum, L. ¢; (9) B. silvarum, L. 2? § (12—14) ; (10) B. rupestris, —
L. 2 (12—14) ; (11) B. vestalis, Foure. 2 (12); (12) B. campestris, Pz. 2 ¢
(10—12) ; (13) B. Barbutellus, K. ¢ 2 (12) ; all these humble-bees only s. ‘
(14) Andrena Hattorfiana, F. ¢ 2 (6—7),s. and c.p.: it confines itself almost —
exclusively to this flower, and I have only once taken a male on Jasione —
montana, and again, a female on Dianthus Carthusianorum, s. ; (15) Andrena |
Gwynana, K. ? (24), c.p.; (16) Halictus albipes, F. 9; (17) H. leucozonius,
Schk. ¢ (4); (18) H. eylindricus, F. 2 ¢ (8—4) ; (19) H. sexnotatus, K. 2 —
(4) ; the species of Halictus sometimes s., sometimes c.p. ; (20) Nomada Fabri-_
ciana, L. 9 ;-(21) N. lineola, Pz. 2 3 6) ; ; (22) N. Jacobaew, Pz. 2; (23) N. «
armata, Scheff. 9 ; (84) Megachile Willughbiella, K. ¢; (25) M. maritima, Ke
& 2, freq. ; (26) M. circumcincta, K. 9 ¢; (27) M. centuncularis, L. ¢ ; (28) |
—. perratulee, Pz. 2 S, very ab., like all the species of Nomada and ~
Megachile, only sucking ; (29) Osmia Folviy anes. Pz. 9, cp. ; (30) O. eenea,
L. g, 8.3; (31) Coelioxys quadridentata, L. ¢ 9, ab. ; (32) C. conoidea, Ill. 2 |
(33) Heriades truncorum, L. ¢; (34) Stelis breviuscula, Nyl. ¢, the last |
four species, s. ; (b) Sphegide : (35) Bembex rostrata, L. (7) ; (36) Psammophila
affinis, K. 9 (5); (387) Ps. viatica, L. g (4), all s.; (c) Vespidw: (38)
Odynerus parietum, L. ¢ (8), s. B. Diptera—(a) Empide: (39) Empis—
tesselata, F. (3, 4) ; (40) E. livida, L. oa) both very ab., s.; (0) oe oe |
(41) coe tenax, L. (7, 8); (42) E. arbustorum, L. (4, oe ; (48) E.
nemorum, L. ; (44) E. ae L.; (45) Rhingia rosea amy SS 12); =
(46) Volucella bombylans, L. ; (7, 8); ; (47) V. plumata, L. ; (48) v. pellucens,
L. (Sld.), all these Syrphides dis "s. and f.p.; (49) Syrphus ribesii, L. (3, 4),
f.p. ; (c) Conopide: (50) Sicus ferrustnsien L., ab., s.; (d@) Muscide: (51)
Echinomyia tesselata, F.; (52) Ocyptera cylindrica, F.; (53) Micropalpus
fulgens, Mgn., all three s. C. Lepidoptera—(a) Rhopalocera: (54) Colias
hyale, L. (Th.), ab. ; (55) Vanessa urtice, L. (12); (56) Satyrus Janira, L. £3
(57) S. Medea, 8S. V. (Sld.) ; (58) Papilio Machaon, L. (18) ; (59) Hesperia”
lineola, O. ; (b) Sphingide: (60) Zygeena lonicerze, Esp. (Th.), ab. ; (61) Ino-
statices, L. ; (c) Noctuw : (62) Mamestra serena, 8. V. 9 (Th.) ; (63) Euclidia.
glyphica, L. ; (d) Tineina : (64) Adela sp., very ab., sometimes as many 0 iam
on one capitulum. D. Coleoptera—(a) Nitidulide : (65) Meligethes, ab., fp. ;
(b) Phalacride : (66) Olibrus bicolor, F., f.p. ; (¢) Lamellicornia : (67) Hoplia
philanthus, Sulz. (Sld.), feeding on the organs of the flower ; (68) Trichius
fasciatus, L., very ab., feeding on the tissues and also pairing on the flowers 2
(d) Conacabaicsdes (69) Toxotus ba rag L., (Siebengeb.) ; (70) Pach
octomaculata, F. (Sld.) ; (71) Strangalia wage by Siebengebos (72) Str. arma
Hbst. See Fd ; (73) Str. attenuata, L.; (74) Str. melanura, L.; (75)
Leptura livida, F.: these Cerambycide feed on pollen and on the anthers,
and those with minal heads, especially Str. attenuata, also suck honey ; (e)

Chrysomelide : (76) Cryptocephalus sericeus, L., feeding on the parts of ie
flower

Co carte

" ‘m] THE MECHANISMS OF FLOWERS. 313

Altogether, I have observed upon Scabiosa arvensis, L. :—

Apidae. Lepidoptera.' Diptera. Other Insects Total.

In Low Germany ... 45 19 17 | 20 101

On the Alps.., —... 10 22 4 4 45

- That is to say, in each hundred species of visitors we have :—

Apide. Lepidoptera.| Diptera. |OtherInsects.| Total.

InLow Germany ...| 44°6 18°8 16°8 19°7 100

Onthe Alps... .. | 22°2 489 20°0 8°9 100

s No. 609, pp. 399, 400: No. 590, 111, pp. 76, 77.)

212. ScaBiosa succisa, L.—The hemispherical capitulum con-
is of fifty to eighty florets, nearly equal in size, which develop in

Fia. 109.—Scabiosa succisa, L.

1.—Flower, before dehiscence of the anthers (after removal of the epicalyx).
2.—Ditto, after the anthers have ican aa’
3.—Ditto, in female stage.

entripetal order. Honey is secreted by a small, fleshy ring above

e€ ovary, surrounding the base of the style, and collects in the
= ow, smooth base of the tube. The tube is 3 to 4 mm. long,
nd above the smooth honey-containing portion it is lined with

314 THE FERTILISATION OF FLOWERS. [PART IT.

hairs to exclude rain. The honey is accessible to short-lipped
insects, especially as the tube widens superiorly to a diameter of
2 mm. at the mouth, and the four (rarely five) rounded lobes of the
corolla, of which the external is the largest, are easily thrust apart..
On the damp, unproductive spots where Scabiosa succisa chictms :
grows, its blue, hemispherical heads, about 20 mm. in diameter,

are among the most conspicuous flowers; and in sunny wena |
until the middle of September, they are visited by very numerous
insects, and are regularly cross-fertilised owing to their pro-
terandrous dichogamy. When the flower opens the stamens which —
were bent inwards in the bud straighten themselves one by one;
then, while as yet the style scarcely extends beyond the mouth of
the corolla (Fig. 109, 2), the anthers dehisce in succession ; only when —
the stamens are completely withered, and the anthers, if insect-—
visits have taken place, are shaken off (Fig. 109, 3), does the style
attain its full length, and the stigma, a little later, becomes viscid,
Self-fertilisation can therefore only occur exceptionally, if at this —
time an anther, still dusted with pollen, comes by accident in contact
with the stigma. In plants flowering in my room I have observed —
this to take place not unfrequently, but never in the open air.

Visitors: A. Hymenoptera—Apide: (1) Apis mellifica, L. $, s. and e.p.,
ab. ; (2) Bombus silvarum, L. 9 § ¢ (as late as Oct. 7) ; (3) B. lapidarius, L.,
% 3; (4) B. agrorum, F. § ¢ (both as late as Oct. 15, 1871) ; (5) B. senilis,
Smith, $ ¢; (6) B. terrestris, L. 3 ¢; (7) B. pratorum, L. $; (8) B. vestalis,
Foure. 9 ¢; B. rupestris, L. ¢ (Oct. 15, 1871), all very ab., s. ; (10) Andrena —
Cetii, Schrank. 2, ¢.p.; (11) A. convexiuscula, K. 3; (12) Habitus rubicundus,
Christ. ?,¢p.; (13) H. leucozonius, Schrank. ¢; (14) H. cylindricus, F. by
all freq. B. Diptera—(a) Bombylide: (15) Exoprosopa capucina, F., ab. in’
July ; (b) Syrphide : (16) Helophilus pendulus, L., ab., also pairiele on the
flowers (Sept. 4, 1870) ; (17) Eristalis arbustorum, L.; (18) E. nemorum, L. ; 4
(19) E. tenax, 1, (beginning of November) all ab., s. and fip.; (20) E
intricarius, . scarcer; (21) Syrphus pyrastri, L., s. and f.p. ; (22) Rhingia
rostrata, L., s.; (c) Empide : (23) Empis livida, L., s., very ab. ; (d) Muscide :
(24) Species of Lucilia; (25) Musea cornicina, F. C. Lepidoptera—(a)
Tthopalocera : (26) Pieris rape, L., ab. ; (27) Satyrus Janira, L. ; (28) Polyom-
matus Phloeas, L., very ab.; (b) Noctue: (29) Plusia gamma, L., ab.; (ce)
Crambina : (30) Botys purpuralis, L., all s. D. Coleoptera—Chrysomelide :
(31) Cryptocephalus sericeus, L., feeding on the organs of the flower. See also_
No, 590, III.

This species, also, has been shown to include female as well as —
hermaphrodite plants in England by Darwin (167), in France by
Lecoq,' and in Germany by Magnus (449).

S. atropurpurea, L., also, is gynodicecious (167).

1 Géographie botanique, 1857, vi.

anrut] THE MECHANISMS OF FLOWERS. 315

213. ScapiosA CoLumBARIA, L.—This species for the most
resembles S. arvensis in the structure of its flower, but besides
_ the five-lobed corolla it presents the following noteworthy differ-
| nces. In S. arvensis the florets increase in size from the centre to
he circumference of a capitulum, but in S. Columbaria this
radual increase is much less marked, though in the marginal
lorets the lobes of the corolla are large and conspicuous. Thus in
me specimen, which I examined closely, the tube in the marginal
lowers was 6 mm. long and 2 to 2} mm. wide at the mouth; the
xternal lobe of the corolla was 7 to 8 mm. long, the lateral were
}mm., the internal 2 to 3 mm. _ In the florets of the disk, imme-
iately contiguous to these marginal florets, the tube was 5 mm.
mg and 2 mm. wide at the mouth, and the lobes of the corolla
rere respectively 3, 2, 1; mm. long; finally, in the central florets
f the capitulum the tube was still 4 mm. long and 1} mm. wide
the mouth, and the lobes of the corolla were 1 to 2 mm. long.
n consequence of the smaller size of the central florets and the
ight increase of size from the centre towards the margin, many
ore florets find room on equal space in S. Columbaria than in
S.arvensis. So, although the capitula in S. Columbaria are distinctly

maller than in S. arvensis, they contain half as many florets again
eventy to eighty).
I have never found plants with abortive stamens in S. Colum-

_ This species only occurs near Lippstadt, in one locality and in
{ amount, sol have had little opportunity of watching its
usect-visitors.
A. Hymenoptera—A pide: (1) Apis mellifica, L. $, s., ab. ; (2) Bombus
| lapidarius, L. ¢, very freq.,s. B. Diptera-—(a) Syrphide : (3) Eristalis tenax,
| L.; (4) E. nemorum, L.; (5) Helophilus trivittatus, F., all three species ab., s.,
and f.p. ; (b) Conopide : (6) Sicus ferrugineus, L.,s. A list of Alpine visitors
(six flies, eight bees, and twenty-eight Lepidoptera) is given in No. 609, p. 400.

aa Scabiosa lucida, Vill., is visited by butterflies and Syrphide
(609).

[=

Orv. COMPOSITE.

: ‘The numerical preponderance which this family has attained
_ M species and genera,! and the extreme abundance of many of the
| Ԥ pecies, are due to the concurrence of several characters, most of

1In Dr. Ludwig Pfeiffer’s Synonymia Botanica over 10,000 genera of Phanerogams
are enumerated ; of these, over 1,000 belong to the Composite.

316 THE FERTILISATION OF FLOWERS. [PART JIT.

which, singly, or in some degree combined, we have become 3
acquainted with in other families, but never in such happy com-_
bination as in the Composite. The following points deserve
special mention: (1) the close association of many flowers; (2) the -
accessibility of the honey, as well as its plentiful secretion and
its security from rain; (3) the possession of a pollen-mechanism,
which renders ovoss-fertilisation certain in the event of insect-
visits. |

1. The association of many flowers in one head is advantageous, —
for the following reasons: '

(a) The flowers are rendered much more conspicuous, and are
accordingly more visited by insects. Conspicuousness is in most
cases increased still further either by the florets being directed
outwards (Cynaroidee), or by the limb of the corolla developing
into a long lobe directed outwards, both of which phenomena
become more marked towards the margin of the capitulum;
or by the marginal florets becoming large coloured radiating ”
laminz, at the expense of the stamens or of both stamens and
pistil (Asteroidec) ; or, finally, by the innermost bracts performing
this function (Carlina). q

(b) Insects can fertilise numerous flowers with much less loss”
of time than when the flowers are separate; and so the chance —
of being fertilised is increased for every flower in the same ratio.
The florets of the disk usually constitute a flat surface over which
the insect crawls, and from which the reproductive organs protrude —
far enough to permit simultaneous fertilisation of many florets.

(c) As the involucre of the whole capitulum plays the part
of a calyx in protecting the flowers, the calyces of the separate
florets can be dispensed with entirely, or they may be adapted
for a new and important purpose by being transfotmed into _
structures which aid the dispersion of the seeds by the wind, or
into barbs furnished with recurved hooks (Bidens), which aid the
transport of the seeds by animals.

2. The free accessibility of the honey is a character which
most Compositee share with Umbelliferze ; and, accordingly, the two
orders rival one another in the variety of their insect-visitors (vide
Cirsium arvensis). But while in Umbelliferze the honey lies fully —
exposed to the rain upon the fleshy disk which secretes it, im
Composite it is secreted by a ring surrounding the style at the |
base of a narrow tubular corolla, and as it accumulates it rises up
into the wider part of the corolla where it is accessible to the most
short-lipped insects, and where the anthers shelter it from rain.

PART 111. | THE MECHANISMS OF FLOWERS. 317

Thus, while the flat layer of honey in Umbelliferse is only suitable
_ for short-lipped insects, the honey of Composite is not only
accessible to them but may be sucked by Lepidoptera and bees
also.

_ 3. The pollen-mechanism agrees essentially with that of
_ Lobeliaceze. The anthers cohere to form a hollow cylinder, and
dehisce introrsely, filling the cylinder with pollen, before the flower
' opens. The two stigmas lie at first closely applied together in
| the lower part of the anther-tube, and as the style grows they
- brush the pollen out of the tube by means of the hairs on their
outer surface. So in the first period the pollen is exposed to
' insect-visitors, and in the second the stigmas separate and expose
their papillar surfaces.

The arrangement of the hairs and of the stigmatic papille
shows some diversity in Composites. The former sometimes, as in
Lobeliacex, sweep the pollen before them, forming a simple ring
' round the style at the base of the stigmas (e.g. Centawrea, Cirsiwm),
or aggregated in a tuft at the extremity of the stigmas (e.g.
Achillea, Chrysanthemum); sometimes they are spread over more
or less of the surface of the style, and the pollen remains en-
tangled among them (e.g. Leontodon). The stigmatic papille
sometimes wholly or partially cover the inner surfaces of the
stigmas, and sometimes are restricted to broader or narrower
» at the margin. This sweeping mechanism, which is
_ apparently inherited from Lobeliacezw, is perfected in many
| Composite by a peculiar irritability of the filaments, which
_ contract when touched by an insect’s proboscis and draw the
anther-tube downwards, squeezing the pollen out at the upper
end exactly at ics proper time for it to be carried to other
flowers.

Crose-fertilisation i in case of insect-visits is thoroughly ensured
for the separate florets in the same way as in Lobeliaces, and
' it is rendered in many cases very probable, and in others in-
_ evitable, for the inflorescence as a whole. For in all cases in
_ which the development of the hermaphrodite flowers progresses
so slowly from the margin of the capitulum towards its centre
- that one or more rows of florets in the female stage are always
surrounded by several rows in the male, the crossing of separate
_capitula must at least be effected by all insects which alight at the
margin (Bellis, Chrysanthemum, ete.); but in many Cynaree the |
florets open centripetally in such quick succession that the
_ capitulum is for a time male only, and afterwards for some time

'
|

318 THE FERTILISATION OF FLOWERS. — [parr mt, —

female only, and in this case all insect-visitors must lead to the ;
crossing of separate capitula (Carduus). Lastly, in the few
Composite in which the florets are all unisexual, either the male
and female florets are confined to separate capitula or the outer
florets in all the capitula are female and the inner male (Calendula,
Silphiwm, etc.). In the former case the crossing of separate
capitula is obviously inevitable, and in the latter (since the outer
florets develop first) it is probable, and more so than in the
case described where centripetal development proceeds slawhy in
a capitulum of hermaphrodite florets.

In absence of insects self-fertilisation is often rendered possible 4
in the hermaphrodite flowers by the stigmas curving backwards till ‘
their papillee come in contact with the pallang :

The irritability of the filaments in Centaurea, Onopordum,
Cichorium, Hieracium, ete., was observed more than a hundred :
years ago by Koelreuter (396, Pt, 11). Severin Axell gives a —
résumé of more recent observations on this point by Morren, Cohn, :
Unger, and others (17). fi

Sprengel recognised the significance of the enlarged margaial
florets, the closing of the capitulum during rain, the brushes on the
style or stigmas, and the distinct proterandry (702, pp. 365-384).

Hildebrand made the floral mechanism of Composite, especially
the distribution of the brushes and the stigmatic papillz, the sub-_
ject of a very elaborate paper containing many magnified figures ,
of styles (357). - In the same year (1869) Delpino gave a full ~
account of the adaptive modifications of Composite (178), and
appended some notes on the bees seen by him visiting Composite.
In a more recent work (180) he tries to prove the gencticg
connection of Composite with Campanulacez and Lobeliacez, and
to trace the gradual passage from entomophilous Senecionide to i
distinctly anemophilous Artemisiacew. I am unacquainted with
most of the forms which Delpino treats of, and am therefore ~
unable to criticise his conclusions, so I confine myself to a general —
reference to his interesting research.

Tribe Hupatoriacee.

My brother Fritz Miiller tells me by letter that at Itajahy,
Adenostemma, growing at the borders of woods, is the haunt of
Zygenide and Glaucopide.

-*
My

214. EUPATORIUM. CANNABINUM, L.—The capitulum contains
five, sometimes only four florets, in each of which the tube is”

PART 111.] THE MECHANISMS OF FLOWERS. 319

24 mm. long, and the wider throat 2 mm. long in addition. By
themselves the capitula are small and insignificant, but very many
(usually several hundred) are closely ageregated ; in an inflorescence.
The red-bordered bracts, the reddish corollz of the florets, and
the white projecting stigmas give this inflorescence a reddish-white
appearance. In this plant the divisions of the style are quite as

Fig. 110.—Eupatorium cannabinum, L.

1.—A capitulum of four florets, in their first (male) stage.

_ 2.—A single floret, in second (female) stage.

From a to b each branch of the style bears a strip of stigmatic papilla on each edge; from b to
t is clothed with hairs.

, 1 0 brig as the whole corolla (5 mm.), They are furnished with rows
| of stigmatic papillz along their edges, only for the first quarter
% their length (a, b, Fig. 110, 2); forthe remaining three-quarters

ey are thickly clothed all round with hairs. In the first period
2 lower stigmatic part of the branches of the style remains still

I
|
if
Po a n nclosed i in the anther-cylinder (Fig. 110, 1); the ends, furnished with

320 THE FERTILISATION OF FLOWERS. [parr m1.

hairs, project beyond it, and diverge so widely that insect-visitors
come in contact with them all round, and carry off upon their
hairy or scaly coats the pollen that had been entangled in the —
hairs of the styles. Afterwards, the lower stigmatic portions _
emerge from the anther-cylinder and from the throat of the
corolla (Fig. 110, 2), and they too diverge so widely that an insect —
in obtaining its honey must come in contact with them. Cross- —
fertilisation is thus ensured, if insect-visits have taken place to a —
sufficient extent to clear all the pollen from the hairs of the style —
before the stigmas in the same floret are exposed. But if these _
hairs still bear pollen when the stigma becomes exposed, an insect-
visitor may effect self-fertilisation as easily as cross-fertilisation. —
If no insects visit the flower at all, fertilisation and even cross- —
fertilisation are still possible, for the outspread branches of the |
style sometimes come in contact with the stigmas of neighbouring
florets.
Visitors: A. Hymenoptera—Apidw: (1) Apis mellifica, L. $, s.; (2)
Bombus (Apathus) inane: Foure. g, 8. 2 Diptera—(a) Syrphide: (3)
Eristalis arbustorum, L.; (4) E. nemorum, L.; (5) E. tenax, L., all three ~
species, ab., f.p.; (6) Muscide : (6) Echinomyia fera, L. ;: (7) tera canina, —
F.; (8). Lucilia albiceps, Mgn. C. Lepidéptera——Riopalodara® (9) Pieris”
rape, L.; (10) Thecla quercus, L.; (11) Lyczena, sp. ; (12) Vanessa Io, L., ab. ;
(13) Argynnis Paphia, L., ab.; (14) Satyrus Galatea, L.; (15) 8. Medusa, S. ~
V.; (16) S. Egeria, L.; (17) Hesperia lineola, O. I saw all these butterflies
together sucking the flowers of Eupatorium on a sunny slope near Willebadessen
(August, 1871) : they took no heed of other neighbouring flowers. D. Neuro-

ptera—(18) Panorpa communis, L. This list is very remarkable on account
of the preponderance of butterflies. See also No. 590, rt.

Tribe Asteroidee.

215. SOLIDAGO VIRGA-AUREA, L.—In the florets of the disk
the style is identical with that of Chrysocoma (cf. Hildebrand, 357).
But while in Chrysocoma numerous capitula unite to form one
surface, and can therefore dispense with ligulate marginal florets,
in S. virga-aurea the capitula are distributed over an elongated
axis; and the disk of each capitulum (4 to 5 mm. in diameter) is
rendered conspicuous by five to seven golden-yellow marginal
florets which increase the whole diameter of the capitulum to 14 or
even 19mm. The marginal florets have acquired their excessive
development of corolla at the expense of their stamens, which are
quite absent ; the branches of the style have almost entirely lost —
their useless sveening saa and bear stigmatic papille along thee
whole length of both borders of their inner surfaces. |

(ban... < aed ds. Dib ty Supine

4

PART III] THE MECHANISMS OF FLOWERS. 321

Visitors : A. Hymenoptera—Apide : (1) Apis mellifica, L. §, 8. ab.; (2)
Bombus rupestris, L. ¢,s.; (3) B. campestris, L. ¢,s.; (4) B. terrestris, L.
3, 8.; (5) Andrena denticulata, K.? ¢,¢.p.ands. (Tekl. Borgst.). B. Diptera
—Syrphide : (6) Eristalis arbustorum, L.; (7) E. nemorum, L., both species
f.p.,ab. C. Lepidoptera—Rhopalocera: (8) Thecla ilicis, Esp., s. A list of
Alpine visitors (six bees, twenty-two flies, twenty-seven Lepidoptera) is given
in my Alpenblumen (No. 609).

216. SoLIDAGO CANADENSIS, L, :—
_ Visitors: Diptera—(a) Syrphide: (1) Eristalis arbustorum, L.; (2) E.
nemorum, L. ; (3) Syritta pipiens, L., all three species f.p., ab. ; (b) Muscide :
(4) Sarcophaga carnaria, L., f.p.; (5) Numerous small Muscide. See also
No. 590, Il.

! 217. BELLIS PERENNIS, L.—Numerous tiny florets 1 to 2 mm.
- in length unite to form a flat, yellow disk 6 mm. in diameter. The

_ white outer lobes (5 mm. long) of the marginal florets bring the

_ diameter of the whole capitulum up to 16 mm. The marginal
florets have no stamens, and their styles have lost their sweeping-
hairs; the two branches of the style are furnished with stigmatic
_ papillze on their edges for their whole length (cf. Hildebrand, 357).

On the other hand, in the florets of the disk the style is short,

_ broadly oval, and closely covered with sweeping-hairs on the outer
surface from the broadest part to the tip; these hairs both sweep the
_ pollen out of the anther-cylinder as the style elongates, and after-
_ wards hold it until it is removed by insects. The branches of the
style in the disk-florets are only furnished with a short strip of -
_ stigmatic papillae on each border below the broadest part. After
_ fertilisation the branches of the style are again drawn within the
corolla, so that the placing of more pollen on the already fertilised
stigma is avoided.

} Visitors: A. Hymenoptera—(a) Apide: (1) Apis mellifica, L. $, ¢p.,
} freq.; (2) Andrena parvula, K. 9, c¢.p.; (3) Halictus minutissimus, K. ?, c.p.,
freq. ; (4) H. cylindricus, F. ?,s.; (5) Sphecodes gibbus, L. 9, s.; (6) Nomada
' lineola, Pz. ¢,s.; (7) N. flavoguttata, K. ¢,s.; (8) Osmia rufa, L. 2,5, and
¢@p.; (b) Formicide: (9) Myrmica levinodis, Nyl., tried to suck. B.
_ Diptera—(a) Empide: (10) Empis livida, L., s., very ab.; (11) E. opaca, F.,
s.; (b) Syrphide: (12) Eristalis arbustorum, L.; (13) E. sepulcralis, L.; (14)
| E. tenax, L. ; (15) E. pertinax, Scop, ; (16) Rhingia rostrata, L., all five species
f.p., very ab.; (17) Syritta pipiens, L., fp. and s, ab. ; (18) Melithreptus
| scriptus, L., fip.; (c) Muscide: (19) Scatophaga stercoraria, L.; (20) Se.
| merdaria, F., both species f.p., ab. ; (21) Lucilia cornicina, F., f.p., freq. ; (22)
Musca corvina, F., do. All these flies had their tongues, legs, and under surface,
especially of the thorax, thickly coated with pollen. C. Lepidoptera—Rhopa-
| locera: (23) Satyrus pamphilus, L., s.; (24) Polyommatus dorilis, Hufn.,
; Y

322 THE FERTILISATION OF FLOWERS. [PART III.

D. Coleoptera—(a) agent (25) Meligethes, f.p.; (b) Gidemeride : (26)
(Edemera virescens, L.; (c) Cerambycide: (27) Leptura livida, L., fp. - See
also No. 590, III.

218. ASTER CHINENSIS, L.—I have noticed on the flowers in
my garden :—
A. Diptera—Syrphide : (1) Eristalis nemorum, L.: (2) E. arbustorum, L.,

both species s. and f.p., ab. B. Lepidoptera —Iphopalaanas (3) Vanessa artic .
L., s. ©. Hymenoptera—Apide: (4) Celioxys simplex, Nyl. 9, s.

Aster alpinus, L.—I have found this plant on the Alps visited
by two beetles, two flies, two bees, and thirty-six Lepidoptera (609). —

219, ASTER AMELLUS, L. (Haarhausen, in Thuringia).—I found
the flowers (Sept. 18, 1871) visited by Hristalis arbustorum, L., in
considerable numbers to feed on the pollen.

Erigeron alpinus, L.—The ligulate marginal florets are female
only; between them and the hermaphrodite florets of the disk isa
zone of female florets which secrete no honey, and in which the ~
teeth and the wide throat of the corolla is not developed ; in these
two classes of female florets the style is devoid of sweeping-hairs.
In Erigeron uniflorus, L., the intermediate zone of tubular female
florets is absent (609).

220. CoNYZA SQUARROSA, L. :—

Visitors: Hymenoptera—-(a) Apide: (1) Halictus quadricinctus, F. 2? g,
c.p. ands.; (2) H. flavipes, F. ¢; (3) H. morio, F. ¢; (4) H. leucopus, K. 9; —
(5) H. longulus, Sm. ¢; (6) H. leucozonius, Schr. ¢; (7) H. cylindricus, F. ~
6; (8) H. maculatus, Sm.? ¢; (9) H. albipes, F. ¢, all in great abundance, —

the ¢s., the 9 s. and c.p. ; (10) Nomada Solidaginis, Pz. 9, s.; (b) Sphegide :
(11) Ganvseys labiata, F. 2.

221. CHRysocoma LinosyRis, L. (Thuringia, near Haarhausen).
—All the florets in the capitulum are alike; those at the edge are
merely slightly curved outwards. Radiating marginal florets are —
useless and therefore absent, for the same reason as in the case of
Tanacetum. The golden-yellow surface formed by the conjunction
of many capitula is conspicuous enough to attract insects from a
considerable distance. When near at hand, capitula in the first
(male) stage (Fig. 111, 1) are more conspicuous than those in the -
second (female) stage; for in the former the teeth of the corolla,
which are 3 mm, long, are widely outspread, but afterwards they

become more and more erect. So insects are induced to visit the
capitula in the proper order. ;

o>.

;
i

PART III. | THE MECHANISMS OF FLOWERS. 323

| The tube of each floret is 35 to 44 mm. long, the wider throat
- into which the honey rises is 1} mm. long, so that the honey is
_ easily accessible. The simultaneous fertilisation of numerous
_ flowers is here rendered possible in a way different from that in
_ Tanacetum. The branches of the style are 1} mm. long, and they
_ bear on their outer borders a row of stigmatic papille (nm, 2) up
_ toa point above their middle ; above this point they broaden, and
are covered with hairs both on their outer surface and on their

Fic, 111.—Chrysocoma Linosyris, L.

1.—Flower, in first (male) stage.
2.—Ditto, in second (female) stage.
n, stigmatic papille ; p, pollen; b, brush of hairs ; a, anthers; ov, ovary.

| Even in the second (female) stage, their tips remain in
1? Rontact, and they only curve asunder in the middle. Insects

creeping over the capitulum, bend down the ends of the styles
. y with the under surfaces of their bodies, and so brush over the
! — of many florets simultaneously.

A. Hymenoptera—Apide : (1) Halictus flavipes, F. ¢; (2) H. albipes, ¥.
3, very freq. ; (3) H. cylindricus, F. ¢, ab. ; (4) H. aapoemtns! K. 6, freq.,
' ls. B. Diptera—(a) Syrphide : (5) Syritta pipiens, L -; (6) Eristalis arbu-
| rem, L.3 @) E. nemorum, L., all three species s. and f.p., very ab.; (d)

i= ¥> 2

324 THE FERTILISATION OF FLOWERS. [parr —

Muscidae : (8) Ocyptera cylindrica, F.,s. C. Lepidoptera—(a) Rhopalocera :
(9) Polyommatus dorilis, Hfn. ; (10) Lyceena alsus, W. V.; (6) Noctue: (11)
Plusia gamma, L., all three s.

Tribe Jnuloidee.

222. GNAPHALIUM LUTEOALBUM, L., as a rule only comes into
bloom at Lippstadt in September. On the wet, sandy places
where it grows, it is by far the most conspicuous plant, especially
as it grows associated in considerable numbers. One sunny day
at noon (Sept. 29, 1869) I noticed the following insects upon its
capitula :—

Visitors: A. Hymenoptera—(a) Apide: (1) Sphecodes gibbus, L. ¢ 9,
several varieties including ephippia, L., s. ; (2) Halictus sexsignatus, Schenck, —
3 9,8.; (b) Sphegide : (3) Pompilus viaticus, L., s.; (4) Ceropales maculata —
F.,s. B. Diptera—(a) Syrphide: (5) Melithreptus scriptus, L.; (6) Melano- —
stoma mellina, L., both f.p.; (6) Muscide: (7) Lucilia, freq.; (8) Pollenia —
rudis, F., both f.p.

Gnaphalium uliginosum, L.—On the inconspicuous capitula of ;
this plant I once caught Sphecodes ephippra, L., s. |

223. PULICARIA DYSENTERICA, Giirtn.—The disk of the capitu-
lum consists of more than 600 florets. Each floret has a tube about
4. mm. long, narrow below and wider above, terminating in five
triangular teeth. I could not discover that the honey rose up —
into the wider part of the tube, but even without its doing so it —
is accessible to moderately short-lipped insects. In these florets —
of the disk no part of the style, except its two stigmatic branches,
protrudes from the anther-cylinder, The stigmas spread apart
horizontally, close above the corolla, in the same spot where the —
pollen lay in the first stage, so that here also many florets can be —
fertilised simultaneously by an insect-visitor. The branches of —
the style are covered over their whole inner surfaces with stig-—
matic papillee, and on the upper third of their outer surfaces with —
hairs which point obliquely upwards. Along the edges of the
triangular valves which form the upper end of the anther-cylinder
stand unicellular hairs, which are much longer and thicker than
the sweeping-hairs on the style and which serve to hold the
pollen that has been swept out of the anther-cylinder, The disk —
is surrounded by nearly 100 marginal florets, each of which has
an outer golden-yellow lobe 5 to 7 mm. long; in these the tube is
2 to3 mm. long, and from it a style protrudes identical with that in

PART III. | THE MECHANISMS OF FLOWERS. 325

the florets of the disk, possessing even the sweeping-hairs that are
here useless from the absence of stamens.

Visitors: A. Hymenoptera—Apide: (1) Heriades truncorum, L. ? ¢,
_ very freq., s. and c.p.; (2) Halictus longulus, Sm. ¢; (8) H. maculatus, Sm.
6; (4) H.albipes, F. ¢; (5) H. cylindricus, F. ¢; (6) H. nitidus, Schenck, ¢,
alls. B. Diptera—Syrphide : (7) Eristalis arbustorum, L. ; (8) E. sepulcralis
L., both species, fp., very ab.; (9) Melithreptus scriptus, L., fp. C. Lepid-
optera—(10) Polyommatus dorilis, Hfn.; (11) Lycana sp. ; (12) Hesperia
thaumas, Hfn., s. D. Coleoptera—Chrysomelide : (13) Cassida murrea, L.,
whose larva feeds on the leaves of this plant, often creeps about the flowers and
effects cross-fertilisation.

Tribe Helianthoidee.

Zinnia, my brother Fritz Miiller tells me, is visited almost
exclusively by Lepidoptera, especially Hesperidz, at Itajahy. In
North America it is visited by ruby-throated humming-birds also
(731).

_ 224, HELIANTHUS MULTIFLORUS, L.—Delpino found Helian-
_ thus fertilised chiefly by Heriades truncorwm, l.., which tapped the
f lowers in their first (male) stage with its abdomen, and dexterously
swept up the pollen that exuded from the anther-cylinder with its
“abdominal collecting-hairs ; hence he concluded that the insect
and the plant had been specially created for one another. The
various relations of insects to flowers, as they are described in this
book, prove such a conception to be untenable.

I have observed as visitors of H. multiflorus :-—

_ <A. Hymenoptera—Apide: (1) Megachile centuncularis, F., ep. ; (2)
iB ictus zonulus, Sm. Siw’ , 8 B. Diptera—Syrphide : (3) Eristalis tenax, L, ;
Bp eytphus pyrastri, L. ; (5) S. ribesii, L., all three f.p. and s,

Tribe Anthemidee.

— 225. AcHILLEA MILLEFOLIUM, L.—This plant is a very heel
. astance of the advantage of many small flowers being united
| ster, both for attracting insects and for simultaneous cross-
ilisation of many flowers by a single insect-visitor.

\j In the florets of the disk, the corolla consists of a tube scarcely
nm. long, passing above into a throat 1 mm. long and equally
de, ending in five triangular teeth. Honey is secreted by an
ular ridge (0, Fig. 112, 2) surrounding the base of the style,

326 THE FERTILISATION OF FLOWERS. [PART IIT.

and rises up into the throat and so is accessible to the most short-—
lipped insects. When the flower opens, the two divisions of the
style are closely appressed and project into the lower part of the
anther-cylinder which is filled with pollen (Fig. 112, 2). They are

ee a a

lt

Fia. 112.

1—5.—Achillea Millefolium, L.

1.—A capitulum, from above. a, stigmas of female flowers; b, stigmas of florets of the disk iz
their second stage; c, anther-cylinders of disk-florets in their first stage; d, bud about to open
Numerous younger buds are hidden in the centre of the capitulum. :

2.—Floret of the disk, just expanding; in section. e, ovary; f, ne x orice | the b
of the style; g, style; h, tube of corolla; #, filaments; k, two divisions of the style ; 1, tip of st: yle
Aan brush of hairs; m, anther-cylinder; m, throat of corolla; 0, valves, closing the anther
cylinder.

a disk-floret, slightly more advanced, with its bract; the pollen is issuing from the anth
cylinder.

4.—Older disk-floret. The stigmas are separate and exserted ; the anthers have been withdra
into the corolla by contraction of the filaments. sot 7

5.—Tip of style of a disk-floret in its first (male) stage. k’, stigmatic papille ; 1, sweeping-hair
p, pollen-grains,
6—8.— Chrysanthemum leucanthemum, L.

6.—Disk-floret, in first (male) stage.
7.—Ditto, in second (female) stage.
8.—Tip of one stigmatic branch, seen from the inner side (x 60).

ee ee

furnished at the tip with divergent hairs (5), so that as the sty
elongates the pollen is pressed out at the upper end of the anther
cylinder, whose terminal valves (0, 2) separate. Finally the
branches of the style emerge, spread apart, turning their stigmat:

SE > ht Rance NI has tiple Wing ac ‘oe

PART III. | THE MECHANISMS OF FLOWERS. 327

inner surfaces upwards, and bend their hairy tips so far backwards
_ and inwards that some of the pollen which remains adhering to
them is removed from the chance of contact with insects (Fig.
112, 4). While the pollen is being forced up the anther-cylinder
projects slightly beyond the corolla (Fig. 112, 3); when the
stigmas are exposed, the anther-cylinder lies more deeply in the
_ throat of the corolla, having been drawn down by the contracting
1 filaments. The stigmas thus come to lie immediately above the
corolla, in the same spot where the pollen was before. The result
' is that as the under-sides of insect-visitors sweep over the cap-
_ itulum they come in contact with many florets and effect many
cross-fertilisations at the same time. In this species, twenty or
more florets (which, however, do not develop simultaneously, but
_ centripetally) are united in a disk about 3 mm. in diameter ; but
since five florets at the margin have each an external lobe over
3mm. long and rather more than 3 mm. broad, the diameter of
the disk is increased to 9 or 10 mm. The marginal florets have
~ attained this enormous development of the corolla at the expense
_ of the stamens, which are quite absent; they possess a style how-
ever, which divides into two branches, covered on their upper
_ surfaces with stigmatic papillz but destitute of hairs. In spite of
the enlargement of the corolla in the marginal florets, the capitula,
__ when they stand alone, are not very conspicuous ; but very many
| capitula, often more than one hundred, are united in a corymbose
inflorescence, which is not only very conspicuous but permits still
' more extensive cross-fertilisation to be effected at once by an
insect-visitor.

_ 226. AcHILLEA Prarmica, L., is distinguished from A. Mille-
folium by the much greater size of its separate capitula, which are,
however, associated in much less numbers in an inflorescence. About
eighty to over one hundred florets, each scarcely 2} mm. long, are
- united in a disk 6 to 7mm. in diameter, at whose edge eight to
_ twelve marginal florets stand. Each of these latter possess an
' outer lobe 4 to 6mm. long and not quite so broad, whereby the
_ diameter of the attractive surface of each capitulum is increased to
_ 15 oreven 18 mm. In other points the flowers agree with those of
A, Millefolium. Both plants grow in equal abundance in the same
localities, they flower at the same time, and are visited to the same
extent by the same insects. In both, but especially in A. Mille-
folium, the strong odour of the plants is probably a great additional
_ attraction ; for species of Prosopis, which are especially fond of

328 THE FERTILISATION OF FLOWERS. [PART III.

strong-smelling flowers, are often found in great numbers on both
plants, particularly on A. Millefolium.

The following list of insects, which I have observed on the
flowers of these two species, shows how successfully the attractive
contrivances described and the easily accessible pollen and honey
effect their purpose :—

A. Hymenoptera—(a) Apidae: (1) Prosopis variegata, F. 2? ¢, very ab. ;
(2) P. pictipes, Nyl. 2 ¢, both species s., and gathering pollen with their
mouths ; (3) Sphecodes gibbus, L., all varieties, including ephippia, L., 2 ¢, 8.,

ab. ; (4). Halictus cylindricus, F, 9 g,¢p.ands.; (5) H. maculatus, Snijacp. :
(6) H. leucozonius, K. 2, ¢.p.; (7) H. morio, F. 9, ¢p.; (8) H. villosulus,

Wh ee eo rohicandce Chr. ¢,s.; (10) H. quadricinctus, F. ¢, s.;

(11) Andrena fulvicrus, K. 9 ¢, ¢.p.. ands. ab.; (12) A. pilipes, F. ¢,s.;
(13) A. dorsata, K. 9 g,¢.p. and s., ab.; (14) A. chrysosceles, K. $; (15) A.
fuscipes, K. ¢; (16) A. nana, K. ¢,s.; (17) A. argentata, Sm. ¢,s.; (18) A
albicans, K. ¢,s.; (19) A. lepida, Schenck, ¢,s.; (20) A. nigripes, K. 2,5. ;
(21) A. denticulata, K. ¢,s.; (22) Colletes fodiens, K. 2? ¢,c.p., fp. and s.,

very ab.; (23) C. Davieseana, K. 9 @, still more ab.; (24) Nomada zonata,

Pz. 9, s.; (25) N. ruficornis, L. 9,8. ; (26) Stelis breviuscula, Nyl. 9, s.;
(27) Heriades truncorum, L. 9 ¢, cp. and s.; (28) Chelostoma nigricorne,
Nyl. g,8.; (29) Osmia spinulosa, K. 9, c.p.; (30) O. leucomelena, K. 2,
c.p.; (b) Sphegide: (31) Crabro alatus, Pz., Lep. 2 g, ab. ; (82) Cr. subter-
raneus, F. ¢ ; (33) Lindenius albilabris, F., freq. ; (84) Oxybelus bellus, Dib. ;
(35) O. trispinosus, F.; (36) O. unigluinis, L., Dlb., all three ab. ; (37) Philan-
thus triangulum, F. ? ¢, freq.; (388) Cerceris arenaria, L. (v. d. L.), not rare;
(39) C. labiata, F., ab.; (40) C. variabilis, Schrk., very ab.; (41) Dinetus
pictus, F.; (42) Ammophila sabulosa, L. ; (48) Pompilus trivialis, Kl. ¢; (44)
P. chalybeeatus, Schiddte, 9; (45) P. plumbeus, Dhlb. 2 ¢, (46) P. rufipes,
L. 2 6; (47) P. viaticus, L. ¢; (48) Ceropales maculata, F., freq. ; (c) Vespide:

(49) Odynerus sinuatus, F. ? ; (50) O. parietum, L. ¢; (51) Pterocheilus —

phaleratus, Latr. 9; (d) Chryside : (52) Hedychrum lucidulum, Latr., Dhib,
2.4, freq. ; (e€) Tenthredinide : (53) Tenthredo notha, K1., s., very freq. ; (54)
Tenthredo scrophularie, L.; (55) Several undetermined sp. of Tenthredo. B.
Diptera—(a) Stratiomyide : (56) Odontomyia viridula, F., ab. ; (6) Tabanide :
(57) Tabanus rusticus, L., freq. ; (c) Bombylide: (58) Exoprosopa capucina,
F., freq. ; (d) Empide: (59) Empis livida, L., ab.; (e) Syrphide : (60) Meli-

poigtig scriptus, L.; (61) M. teeniatus, Men. ; (62) Volucella bombylans, L. ;

ve . pellucens, L. (Almethal) ; (64) Eristalis sepulcralis, L. ; (65) E. tenax,
L.; (66) E. arbustorum, L. ; (67) E. nemorum, L., all four ab., both s. and f.p.,
usually covered below with pollen ; (68) Syritta pipiens, L., s. and f.p., ab. ;
(69) Eumerus sabulonum, Fall.; (f) Conopide: (70) Osriops flavipes, Li
(71) Physocephala vittata, F., both freq., s. ; (g) Muscide: (72) Gymnosoma

rotundata, Pz. ; (73) ee cylindrica, F.; (74) Echinomyia ferox, Pz., —

freq. ; (75) E, tesselata, F. ; 4 Gonia capitata, Fallen, C. Lepidoptera—(qa)

Rhopalocera: (77) Pierisnapi, L.; (78) age igr silvanus, Esp.; (79) Satyrus
pamphilus, L. ; (80) Polyommatus Phileas, L.; (81) Lycena Egon, S. V.; (8)

Crambina : (82) Botys purpuralis, L., alls. D, Coleoptera—(a) Buprestide :
(83) Anthaxia nitidula, L, (Thur.) ; (6) Cerambycide : (84) Leptura testacea,

- al

varrurj] THE MECHANISMS OF FLOWERS. 329

_L.; (85) L. livida, F., both f.p.; (e) Coccinellide : (86) Exochomus auritus,

Scriba, ab. ; (d) Chrysomelide : (87) Cryptocephalus sericeus, L., feeding on
_ the tissues of the flower. Forty-three additional visitors (including fifteen
_ beetles) are enumerated in No. 590, 11. See also No. 609.

Hq 227. ANTHEMIS ARVENSIS, L.—The structure of the flower is
similar to that of Chrysanthemum lewcanthemum and Matricaria
~Chamomiilla ; in regard to conspicuousness and amount of insect-
visits it stands between the other two. Each capitulum forms
_ a white circle 21 to 27 mm. in diameter, with a central yellow
disk 5 to 7 mm. in diameter. Since the plant does not possess
the strong odour of MZ. Chamomvilla it is visited by numerous bees.
| Visitors : A. Hymenoptera—(a) Apide : (1) Apis mellifica, L.$,s.; (2) An-
drena Schrankella, Nyl. 9, ¢.p. and s.; (3) A. nigrownea, K. 9, c¢.p. and s. ;
_ (4) A. fulvierus, K. 9, cp. and s.; (5) A. nana, K. ?,s.; (6) A. minutula,
_K. ¢; (7) Halictus lucidulus, Schenck, 2; (8) H. nitidiusculus, K. ? ; (9)
_ Colletes Davieseana, K. 9 g, cp. and s, ab.; (b) Sphegide: (10) Cerceris
' variabilis, Schrk. ¢; (11) Crabro cribrarius, L., Dib. 2; (12) Cr. alatus, Pz.
623 (¢) Tenthredinide : (13) Tenthredo notha, Kl. B. Diptera—(a) Stra-
_ tiomyide : (14) Nemotelus pantherinus, L., very ab. ; (b) Syrphide-: (15) Eri-
’ stalis arbustorum, L.; (16) E. nemorum, L.; (17) E. tenax, L.; (18) E
sepulcralis, L., all four fp., ab. ; (19) Syritta pipiens, L.; (c) Muscide : (20)
Echinomyia Gecnelata F.; (21) Scatophaga stercoraria, L. ; (22) Sc. mae
f., all three fp. C. Coleoptera—(a) Elateridew : (23) Athous niger, L. ; (d)
reulionide : (24) Bruchus sp.; (¢) Cerambycide : (25) Leptura livida, L.

228. ANTHEMIS TINCTORIA, L. (Thuringia, July, 1868 and
| 1870) :—

Visitors ; A. Hymenoptera—(a) Apid@: (1) Colletes marginata, L. ¢, s. ;
' (2) Halictus maculatus, Sm. 9, ¢.p.; (3) Heriades truncorum, L. ?,s. and
| e.p.; (b) Ichneumonide: (4) Various sp. B. Diptera—(a) Syrphide: (5)
Eristalis arbustorum, L. ; (6) Syritta pipiens, L.; (7) Melithreptus teeniatus,
~ Mgn., all three fip.; (b) Conopidw: (8) Myopa sp., s.; (c) Muscide: (9)
_ Gymnosoma rotundata, L. ; (10) Ulidia erythrophthalma, Mgn., in hundreds.
| D. Coleoptera—(a) Elateride ; (11) Agriotes gallicus, Lap. ; (b) Mordellide :

| (12) Mordella fasciata, F, Delpino mentions as a visitor of this plant Lomatia
_ Beelzebub, F. (Diptera, Bombylide). (No. 178, p. 121.) The flowers are
‘described and additional visitors are enumerated in No. 590.

__—- 229. CHRYSANTHEMUM LEUCANTHEMUM, L. (Fig. 112, 6—8).
Four to five hundred florets, in which the corolla is scarcely 3 mm.
_ long, unite to form a yellow disk 12 to 15 mm. in diameter;
at its edge are twenty to twenty-five florets with abortive
stamens, each of which has a white external lobe, 14 to 18 mm.
“cng, 3 to 6 mm. broad, so that the yellow disk is surrounded by a

white border as broad as or broader than itself, and the whole attrac-
| tive surface now has a diameter of 40 or more millimetres, In the

*, alll

z

330 THE FERTILISATION OF FLOWERS. [PART ILI,

florets of the disk, the throat, into which the honey rises, is s
1 mm. deep, so that the honey is accessible to the most shores
lipped insects. In the first stage (Fig. 112, 6), the pollen, and in
the second (Fig. 112, 7), the stigmas, stand immediately above the
corolla; insects moving over the capitulum must cross-fertilise many
florets simultaneously. The branches of the style end in a thick
tuft of divergent hairs (/, 8), which sweep the pollen out of the
anther-cylinder (p, 6) as the style elongates. The inner surface of
each division of the style bears two broad rows (k’, 8) of sigue
papille, separated by a narrow interval; these stigmatic papil ee
extend over the outer edges, and are there regularly dusted hb
pollen if the pollen Has has got heaped above the anthers
cylinder by the protruding style is not removed by insects. Self-
fertilisation is as inevitable in absence of insects as cross-fertilisation
is when their visits occur. The stigmatic surfaces in the margir -.
florets are just as in the florets of the disk ; but the now functionles
sweeping-bairs are distinctly shorter in the marginal florets.

Visitors: A. Hymenoptera—(a) Apide: (1) Prosopis communis, N. $i
(2) Sphecodes gibbus, L. @ ¢, all varieties, including ephippia, L.; (8) H
lictus maculatus, Sm. 2 g,¢.p. and s., freq. ; (4) H. leucozonius, Schr. 2, Pe :
(5) H. albipes, F. ¢,s.; (6) H. eylindetan F. 2 g,¢.p. and s., very ab. ; A
H. villosulus, K. 2 g, cp. ands.; (8) H. rubicundus, Chr. 9, e.p. ; (9) An
drena xanthura, K. 9, s.; (10) A. nigrownea, K. 2, ep.; (11) Colletes
Davieseana, K. 2 ¢,¢.p. and s., very ab. ; (12) Bombus terrestris, L. 9, 8.5
once. (Here also Delpino’s distinction between Composite adapted for Ha-
lictus and those adapted for bees with abdominal brushes falls to the ground,
for though the flat disk of Chrysanthemum leucanthemum must, according to
Delpino, be fertilised mainly or exclusively by bees with abdominal ite
found no such bees on it, but many specimens of Halictus, Andrena, 2
Colletes). (b) Sphegide : (13) Cerceris variabilis, Schrk. ; (14) Crabro cepha:
lotes, Shuck. 9; (15) Cr. cribrarius, L., oe 6, freq.; (16) Oxybelus
uniglumis, L., Dlb., ab.; (17) O. tridpinosam F .3 (ce) Ichneumonide : (18)
Various sp. ; (d) Tenthr edinide : (19) Tenthredo (Allantus) notha, K1., s. ; (20)
T. scrophularie, L. ; (21) Several undetermined sp. of Tenthredo ; (22) Cim
bex sericea, L. B. Diptera—(a) Empide: (23) Empis rustica, ee (b) Stra-
tiomyide : (24) Nemotelus pantherinus, L., exceedingly abundant, sucking ;
(25) Odontomyia viridula, F., very ab., s.; (c) Bombylide: (26) Systechus
sulfureus, Mikan, s. (Sld.) ; (d) Sirpbhdle (27) Pipiza lugubris, F. ; be
Cheilosia fraterna, Mgn.; (29) Syrphus nitidicollis, Mgn., fp. ; (30) Meli
threptus teeniatus, Mgn., f.p.; (31) Volucella pellucens, L. (Sld.) ; ‘(32) Syritta —
pipiens, L., s. ; (33) Eristalis Bp neta . 3 (84) E. horticola, Deg. (Sld.)
(35) E. semdobum, 2 .; (86) E. sepuleralis, L. ; (87) E. eeneus, Scop., all five
species very ab., f.p. ; (88) Helophilus floreus, L., fp. ; (89) H. pendulus, Le
(e) Conopide : (40) Conops flavipes, L., s. ; (41) Sicus ferrugineus, L., 8.3; (F7 )
Muscidae : (42) Echinomyia tesselata, FE. ; (48) Pollenia Vespillo, F., fp. a
8. 5 (44) Lucilia cornicina; F: ; (45)-L. silvarum, Mgn. ; (46) Pyrellia eT

PART III. | THE MECHANISMS OF FLOWERS. 331
| Lett. ; (47) Musca corvina, F. ; (48) Scatophaga stercoraria, L., s.; (49) Mac-
quartia preefica, Zett. ; (50) Sepsis sp.,s. C. Lepidoptera—(a) Rhopalocera :
(51) Melitaa Athalia, Esp. ; (52) Hesperia alveolus, H. ; (53) Satyrus Janira,
—L.; (0) Sphinges: (54) Ino statices, L., freq. ; (c) Noctue: (55) Anarta
myrtilli, L., alls. D. Coleoptera—(a) Nitidulide : (56) Meligethes, very ab. ;
(bd) Dermestide: (57) Anthrenus pimpinelle, F., f.p.; (¢) Elateride: (58)
_Athous niger, L.; (d) Lamellicornia: (59) Cetonia aurata, L. (Sld.) ; (60)
_ Trichius fasciatus, L., ab, ; (61) Tr. nobilis, L.; (e) Malacodermata: (62)
Malachius eneus, L. ; (63) Dasytes flavipes, F. ; (64) Trichodes apiarius, L. ;
_(f) Mordellide : (65) Mordella aculeata, L., ab. ; (66) M. fasciata, F.; (g)
| Cerambycide : (67) Strangalia attenuata, L. ; (68) St. armata, Hbst. ; (69) St.
atra, F.; (70) St. melanura, L., ab. ; (71) Leptura livida, F., very freq. ; (72)
Pachyta octomaculata, F. (Sld. Siebengebirge). See also No. 590, m1., and
No. 609.

i Altogether I have observed on C. leucanthemum—

i

LY Other |

& Lepido- Coleo- Hemi-

i? Apide. | Hymeno- Diptera. | Total.
i P aba 4 | P | ptera, ptera. “t

. |

| In Low Germany| 14 11 8 | 30 | 21 — 84
t

(| On the Alps... 5 2 34 | 20 | 6 1 68

In each 100 insect-visitors there are therefore—

. Other ;
Lepido- Coleo- He
Apide. cee. ae eh Diptera. ptera. wria Total.
| In Low Germany} 16°6 131 9°5 35°7 25°0 ~ 99°9
\Onthe Alps ..| 74 | 29 | 50:0 | 294 | 88 | 1-4 | 99°9

¢
_ _- 230. CHRYSANTHEMUM INODORUM, L.—The only visitors that I
have noticed are Hedychrum lucidulum, Dhlb. 3 (Chryside), and

| Ulidia erythrophthalma, Men. (Muscide).

231. CHRYSANTHEMUM CoRYMBOSUM, L.—(Thuringia) :—

____ Visitors : A. Hymenoptera—Sphegide : (1) Cerceris variabilis, Schrk. 9.

B. Diptera—Muscide: (2) Ulidia erythrophthalma, Mgn. C. Hemiptera—
(8) Capsus sp., s. Additional visitors (nine Coleoptera, four Diptera, one
_ Hemiptera, five Hymenoptera, three Lepidoptera) are enumerated in No.

590, 111.

332 THE FERTILISATION OF FLOWERS. [PART I re

<i]
re.

232. CHRYSANTHEMUM PARTHENIUM, Pers :—

Visitors : Lepidoptera—Sphinges : Sesia tipuliformis, L., s., also Halie u S
and Foenus (No. 590, III.). -

233. MATRICARIA CHAMOMILLA, L.—The general structure < s
the flower agrees with that of C. lewcanthemum, but the receptz
of the capitalum is always more convex in this plant. d

As the centripetal development of the florets proceeds, the
receptacle rises up into a cylinder, rounded off above. Those
florets which have ceased blooming always occupy the outer he .
around the cylinder, those that are still in the bud cocupy
rounded apex, those that are in full bloom occupy the space betwee
on which insects alight. The result of this peculiarity is that inse
always come at once to the right spot for obtaining their hooky a
for fertilising the flowers.

In regard to conspicuousness, WV. Chamomilla is far inferior to
C. leucanthemum ; for each capitulum forms a white circle 18 ©
24 mm. in diameter against 40 mm. or more in C. Jeucanthenll
with a yellow central disk 6 to 8 mm. in diameter against 12 to 15 mm n.
in the other. Accordingly its insect-visitors are far less numerous
and less varied. The strong odour which the capitula emit seems
disagreeable to most bees; only the species of Prosopis, which are
themselves strong-smelling, are fond of the plant, as they are also
of Ruta graveolens, etc. The odour seems pleasant, on the o ner
hand, to flies; they are found abundantly on the capitula, anc
constitute the chief fertilisers of the plant.

Visitors: A. Hymenoptera—(a) Apide: (1) Prosopis signata, Py, 39
ab. ; (2) Sphecodes gibbus, L. 9 ¢; (b) Sphegide : (8) Oxybelus uniglun nis,
L., ab. B. Diptera—(a) Stratiomyide : (4) Nemotelus pantherinus, L., very
PM . 8.3 (b) Empide: (5) Empis livida, L., ab., s.; (c) Syrphide: (6) E
stalis arbustorum, L. ; (7) E. nemorum, L. ; (8) E. sepulcralis, L., ee ay me
very ab., fp. ; (9) Syritta pipiens, L., very ab., f-p.; (d) Muscide : (10) §
phaga carnaria, L., ab. ; (11) S. haemarthoo, Mon. ; (12) Pollenia Ves
F., all three f.p. ; (18) Lucilia cornicina, F. ; (14) Spilogaster nigrita, Fa
G, Coleoptera—(a) Nitidulide: (15) Meligethes, ab.; (6) Cerambycie
(16) Leptura livida, L.; (17) Strangalia attenuata, L., both not rare. See
also No. 590, MII. | +

234, TANACETUM VULGARE, L.—Several hundred florets are
united in a flat discoid capitulum, to which radiating margina
florets would be of no use, since numerous capitula stand clo se
together almost forming a single surface. The union of capitula

partut] § THE MECHANISMS OF FLOWERS. 333

i

to form one golden-yellow surface is not only of advantage to
this plant by increasing its conspicuousness and thereby attracting
‘more insects, but also, as in Achillea, because the insects easily
pass without interruption over the whole surface and _ cross-
fertilise very many florets with their feet in the shortest possible
time. It is of especial advantage to pollen-collecting bees and
pollen-feeding flies, letting them perform their work in the quickest
and most convenient manner; and this advantage to the insects
“reacts: upon the plant itself, since these pollen-seeking insects
naturally prefer those flowers which offer them such perceptible
/advantages. The honey is generally accessible, since the throat of
the corolla is only 1 mm. deep. The condition of the style aids in
the simultaneous fertilisation of many florets by a single visitor.
It bears at its apex a capitate tuft of divergent hairs, and in the
first stage of the flower it presses the pollen out of the anther-
cylinder, raising it just so high that it can be swept off the surface
of the capitulum by the insects ; afterwards in the second stage, it
sprea(s out its two branches, set with stigmatic papille on their
‘inner surfaces, in the same place that the pollen occupied before.

EF - Visitors: A, Hymenoptera—(a) Apidw: (1) Apis mellifica, L. $,s.; (2)
‘Colletes fodiens, K. ¢ 2,8. and c.p., very ab. ; (8) C. Davieseana, K. ¢ 9,8.
and c.p., still more ab. ; (4) Halictus maculatus, Sm. g @, s. and c.p. very ab. ;
) Andrena fulvicrus, K. ¢,s.; (6) A. denticulata, K. 9, c¢.p.; (7) Sphecodes
gibbus, L. ¢ 9, several varieties, including ephippia, L., s., and receiving some
| pollen upon their hairs; (6) Sphegide: (8) Dinetus pictus, F. 9 ¢, freq. ;
' (9) Mellinus arvensis, L.; (10) Crabro sp.; (c) Vespidw: (11) Odynerus
peta, L. ¢. B. Diptera—(a) Stratiomyide : (12) Odontomyia viridula,

. ab, ; (6) Syrphide : (13) Eristalis arbustorum, L. ; (14) E. nemorum, L. ;
5) Syrphus ribesii, L., all three f-p., ab. ; (16) Syritta pipiens, L., s. and f.p.,
"very freq. ; (17) Malithrontrs teeniatus, Mgn., f.p.; (c) Muscide: (18) Sar-
| cophaga carnaria, L. C. Lepidoptera--(a) PRhopalosara’s (19) Polyommatus
' Phiceas, L. (as late as Oct. 19) ; (20) P. dorilis, Hfn. ; (21) Vanessa Atalanta,
| L. (as late as Sept. 27) ; (b) Noctuew : (22) Hadena didyma, Esp. g, s., by day ;
(c) Crambina : (23) ye hte dete alls. D. Coleoptera—Cocc iethiilie’ (24)
' Coccinella bipunctata, L. ; (25) C. quinquepunctata, L. E. Hemiptera— (26)
Several species of bugs. E, Neuroptera—(27) Panorpa communis, L., freq.
See also No. 590, mI.

235, ARTEMISIA Dractuncutus, L., is anemophilous, but Herr
| Borgstette has seen it visited by Melanostoma mellina (Syrphide).

——

Tribe Senecionidee.

7 236. TussILaAco FARFARA, L—In centre of each capitulum are
thirty to forty male florets, around which stand about three hundred

334 THE FERTILISATION OF FLOWERS. [PART In.

female florets. At night and in dull weather the capitulum closes up,
but in sunshine it expands to a golden-yellow disk 20 to 25 mm. in
diameter. The central florets have an ovary with an abortive ovule ;
around the base of the style is a yellow, fleshy nectary, which is
visible through the base of the white tube of the corolla, which is
4mm. long. The honey rises into the dark-yellow, conical throat,
which is more than 1 mm. long; from this throat the anther-
cylinder protrudes. The branches of the style remain hea
almost to the tip, and are covered above and on their outer eee 3
with short sweeping-hairs. The marginal florets have a perfect C
ovule, a tube 3 mm. long, devoid of honey, and a narrow linez
outer lobe 6 to 8 mm. long. The style projects 2 to 3 mm. beyon F
the tube of the corolla, and divides into two branches not half a
millimetre long, furnished on their inner surfaces with stigmatic
papillae and on their outer surfaces and at their tips with
sweeping-hairs which are no longer of use to them. Thus division
of labour has here taken place: the marginal florets make the
capitulum conspicuous and produce seed, while the central florets
secrete honey and produce pollen. The stigmas in the marginal
florets are distinctly developed before the pollen emerges at the
top of the anther-cylinder ; so that if sufficient insect-visits occur, .
cross-fertilisation of separate capitula always takes place. In
absence of insects self-fertilisation is obviously impossible.

‘Visitors (April 11, 1869, Stromberg Hill): A. Hymenoptera—A pide:
(1) Apis mellifica, L. §, in hundreds, s, and c.p.; (2) Andrena fulvicrus,
K. 2, do.; (3) A. Gwynana, K. 9, s. and e.p., freq.; (4) A. parvula, K.
2, do.; (5) Halictus nitidus, Schenck, 2?,¢p. B. Diptera—(a) Bombylide
(6) Bombylius major, L., s.; (b) Syrphide: (7) Eristalis tenax, L., fp. U
Coleoptera—Nitidulide : (8) Meligethes, f.p., freq. A list of Alpine visitor:
(twenty-one flies, three bees, one ant, two Lepidoptera) is given in m
Alpenblumen (609). ;

Petasites albus, Girtn., is dicecious, and, as is usual in dicecious
plants, the male capitula are the more conspicuous. In the femal
capitula there are two kinds of florets. In the centre are some whose —
only function is to produce honey, but which possess functionless —
stamens and pistil ; and around these stand a much larger number
of female florets, which produce no honey and possess no stame ns
The male capitula may consist of florets of one kind only; thes
secrete honey and possess a style, whose branches sweep out the
pollen from the anther-cylinder by means of hairs in the ordinar
way but are not provided with stigmatic papille. But the male
capitula, as often as not, contain some small fwnetionless florets

parr ur.] THE MECHANISMS OF FLOWERS. 335

also; these occupy the same position in the male capitulum as
the sexual florets in the female, and they resemble the latter in
the complete absence of a nectary and of stamens, in the possession
of a style, and in the very narrow tubular corolla. They are
obviously degenerate female florets, which occupy in reduced
numbers and in a functionless condition the place that in the primi-
tively hermaphrodite or gynomoncecious capitulum was occupied by
functional female florets (609).

_ Homogyne alpina, Cass., is gynomoneecious. The marginal
female florets secrete no honey and have lost all traces of stamens,
-and their corolla is reduced to a short and narrow tube with a
more or less insignificant remnant of a ligulate limb. I have
seen the plant visited by five Diptera, one humble-bee, and
twenty-eight Lepidoptera (609).

237. ARNICA MONTANA, L. (Sld.) :—

_ Visitors: A. Hymenoptera—Apide: (1) Apis mellifica, L. $, s. and
¢.p., ab. ; (2) Bombus pratorum, L. $, 8. ; (3) Andrena Gwynana, K. 9,c.p.
B. Diptera—(a) Bombylide: (4) Anthrax hottentotta, L. ; (b) Empide : (5)
Empis tesselata, F., s., ab. ; (c) Syrphide: (6) Eristalis horticola, Mgn. ; (7)
E, arbustorum, L. ; (8) E. nemorum, L., all three very ab., 8. ; (9) Syrphus
‘Tibesii, L., ab.; (10) S. umbellatarum, Mgn. ; (11) Volucella bombylans,
I, te (12) V. pellucens, L., all s. and fp. (d) Conopide: (13) Sicus
ferrugineus, L.,s. C. Lepidoptera—Rhopalocera: (14) Argynnis Aglaia, L.
(15) Vanessa urtice, L.; (16) Vanessa Io, L., all threes, D. Coleoptera—(a,
| Lamellicornia: (17) Trichius fasciatus, L. ; (b) Chrysomelide : (18) Crypto-
cephalus sericeus, L.

i The structure of the flower is described in my Alpenblumen.
On the Alps I have found it visited by three beetles, seven flies,
‘four humble-bees, and thirty-four Lepidoptera.

238. SENECIO JACOBHA, L.—Sixty to eighty florets, each con-
‘sisting of a tube 2} to 3 mm. long and a throat equally long, are
‘united into a disk 7 to 10 mm. in diameter; twelve to fifteen
radiating marginal florets increase this diameter threefold. The
‘style has the same characters as in Tanacetum.

Visitors : A. Hymenoptera—(a) Apide: (1) Apis mellifica, L. 9, s. and
ep. ; (2) Bombus lapidarius, L. § ¢, ep. ands. ; (8) B. pratorum, L. § ¢,
ep. and s.; (4) B. campestris, Pz. ¢,s.; (5) Andrena fulvicrus, K. 9, cp.
(6) A. denticulata, K. 9, ¢.p. ; (7) Halictus cylindricus, F. ¢; (8) H. albipes,
'F. ¢; (9) H. maculatus, Sm. ¢; (10) H. nitidus, Schenck, @, all s. ; (11)
/Nomada varia, Pz. 9, very freq. ; (12) N. zonata, Pz. 2; (13) N. fulva, Pz.
9; (14) N. ferruginata, K. 9, all s.; (15) Osmia spinulosa, K. 2, ep.

§

336 THE FERTILISATION OF FLOWERS. [PART III.

(Thuringia) ; (16) Heriades truncorum, L. 9 d,s. ande.p. (b) Tenthredinide :
(17) Tarpa cephalotes, F. (Thur.) B. Diptera—(a) Stratiomyide : (18) Odonto-
myia viridula, F., s. ont f.p., very ab. ; (0) met ee (19) Eristalis tenax, L.;
(20) E. nemorum, L.; (21) E. arbustorum, L . 3 (22) E. sepulcralis, L. ; (23)
E. eneus, Scop. ; (24) Syritta pipiens, L. ; (25) Ascia podagrica, F., all very
ab., both s. and f.p.; (26) Cheilosia soror, Zett.; (27) Ch. preecox, Zett.
(Teklenburg, Borgst.), freq. ; (¢) Empide: (28) Empis fee L., very a.b., 8. 5
(d) Muscide: (29) Lucilia sp. ; (30) Pollenia rudis, F. ; (31) Aricia incana,
Wiedem. ; (32) Onesia floralis, R. D. ; (88) O. sepulemlis, Mgn. ; (34) Oliviera
lateralis, Pz., very freq. ; (e) Mycetophilide : (35) Sciara Thome, L. C. Lepi-
doptera—(a) - iepigroe : (36) Polyommatus Phloas, L.; (37) Saty ag
hyperanthus, L. ; (b) Sphinges : (38) Sesia asiliformis, Rott. (Thur.), all s.
D. Coleoptera : (39) Cidemera virescens, L., fp. E. Hemiptera—(40) Co
sp. See also No. 590, Itt.

239. SENECIO VULGARIS, L.—Sixty to eighty florets unite to
form a capitulum. In each the tube is 3} to 4 mm. long, the
throat, to whose base the honey rises, is only 1 to 14 mm, long;
the honey is therefore very easily accessible. But since the
capitula have no marginal florets with long outer lobes, and are
scarcely 4 mm. in dines they are very inconspicuous and ¢
very sparingly visited by insects.

In the course of fifteen years I have only seen the plant
visited by one drone- Ay, Syritta pipiens, s. and c.p. freq., and by
Pyrocoris aptera, L., s.; Dr. Buddeberg found two bees, seo
morio, F. 2, ¢.p., and Horindis truncorum, L. d,s.

On the other hand, self-fertilisation takes place regularly. The
pollen-grains, swept out by the hairs at the tip of the style, remain
partly on the edge of the stigmas and partly fall upon their mner
surfaces when they separate. It is certain that this self-fertilisation
is effectual, for the plant is fully productive even in periods of bad
weather, when it is assuredly not visited by insects. -

Tribe Cynaroidee.

240, ECHINOPS SPHAROCEPHALUS, L.—The corolla is 5 to 6 mm,
long and almost filled up by the style; it is cleft nearly to the
base into five linear lobes, and the honey is therefore accessible
to very short-lipped insects. The stigmas are not only surroondell |
by a ring of long hairs at their base, but are covered with short
hairs on the whole of their outer surfaces. As the style emerges
from the anther-cylinder it sweeps the greater part of the pollen
before it but remains dusted with a small part. After emerging,
its two branches (stigmas) remain still for some time folded together,
so that the insect-visitors may remove the pollen adhering to their —

PART III. ] THE MECHANISMS OF FLOWERS. 337

outer surfaces ; finally they separate and display their inner sur-
- faces (which are smooth, but capable of fecundation) to the touch
of visitors. Self-fertilisation cannot occur.

Hymenoptera—(a) Apide : (1) Bombus lapidarius, L. % ; (2) B. silvarum,
_L. %; (3) B. muscorum, F. § ¢; (4) Halictus quadricinctus, F. 9 ¢; (5)
_ H. rubicundus, Chr. ¢, all s. ; (b) Vespide: (6) Polistes gallica, L., and var.
_ diadema, ab., s. See also No. 590, 111.

_ Fig. 118.—Echinops spherocephalus, L.

1.—Flower, at close of the first (male) stage.

2.—Ditto, in second (female) stage.

3.—Section of style and corolla-tube around it.

a, filaments ; b, anthers; c, brush on style; d, stigma; e, nectary.

_ chinops Ritro, L., was found by Delpino to be visited by a
- sand-wasp, Scolia bicincta (178).

«241, CARLINA ACAULIS, L.—In this plant the involucral bracts
play a more important part than usual. The outer ones are armed
with such strong spines that, in connection with the spiny leaves, they
form a strong safeguard against any attempt to devour the plant.
The inner ones help to thake the flower conspicuous by day, and
t night and in rainy weather close in over the flower to protect it
from wet. and cqld (609).

The opening and closing of the capitulum in Carlina and other

Z

| =
| ee

338 HE FERTILISATION OF FLOWERS. [parr iit,

Cynaree 1 is brought about, according to Rathay,! by loss and gain
of fluid in a layer of sclerenchyma in the involucral bracts. — :

Visitors in Low Germany: A. ye : (1) Bombus
lapidarius, L. ¢; (2) B. confusus, Schenck, ¢; (3) B. silvarum, L. go; (4)
B. agrorum, F. ¢; (5) B. muscorum, F. 6; (6) B. terrestris, L. ¢; (7)
B. rupestris, L. ¢,all very-freq., s., sometimes spending the night in the thistle-
heads ; various males of Halictus, the most frequent being (8) H. cylindricus,
F.g5 ‘and (9) H. quadricinctus, F. ¢. B. Coleoptera—Curculionide : (10)
Larinus senilis, F. For og visitors, see No. 609.

242, PiSesik VULGARIS, L. (Thuringia, end of August and
beginning of September 1869) :—

Visitors : A. Hymenoptera-——(a) Apide : (1) Bombus lapidarius, L. ¢ ; (2)
B. terrestris, L. ¢; (3) Halictus cylindricus, F. ¢, very freq. ; (4) H. pe
cinctus, F. ¢; (5) Megachile cireumcincta, K. 9; (6) M. lagopoda, K. g,
(only once !) ; (7) Celioxys quadridentata, L. 9; (8) C. acuminata, Nyl. 2;
(b) Sphegide: (9) Ceropales maculata, F. 9, all sucking. See also No.
590, IIL. |

243, Arctium (LAppA) Minus, D.C.—The throat of the corolla
is 3 mm. long, with erect, triangular teeth only 1 mm. long; it
becomes filled with honey often more than half way up. The —
branches of the style, which are little over 1 mm. long, are covered
over the whole inner surface with colourless stigmatic papille, and
on the violet outer surface with short, sharp hairs, directed obliquely
upwards ; these hairs are continued a short distance below the —
bifurcation of the style and terminate in a ring of longer hairs —
(cf. Hild. 357, p. 45, pl. v., fig. 32). The style emerges from the —
anther-cylinder as far as a point 1 to 2 mm. below the ring of —
longer hairs, and spreads its two stigmatic branches widely apa
Self-fertilisation can scarcely occur.

Visitors : (1) Bombus agrorum, L. §, s. ; (2) Halictus longulus, Sm. oe
See also No. 590, 111.

244, ArctTiuM (LAPPA) TOMENTOSUM, Lam.

Visitors : A. Hymenoptera—A pide : (1) Apis mellifica, L. $ , very ab., s. and
c.p.; (2) Bombus agrorum, F.§ ¢,s.; (3) B. campestris, Pz. ¢,s. ; (4) B. silvarum,
L. 9,8. ; (5) Megachile centuncularis, L. 9,8. B. Lepidoptera—Noctue :
Plusia gamma, L., s., ab.

_ 245, CARDUUS CRISPUS, L.—The expanded throat of the corolla
is 24 to 3 mm. long, and the linear, very slightly divergent segments:

* Siteungsber. der Akad, der Wissenschaft, Berlin, vol, 1xxxiii. May, 1881.

- PART III. | THE MECHANISMS OF FLOWERS. 339

are 4to 54} mm. long. About thirty-five to seventy-eight florets
unite in a capitulum, which inferiorly is scarcely 10 mm. in
diameter. The tubes of the florets point outwards more and more
the nearer they stand to the edge, and the whole capitulum when
seen from above appears as a red surface 25 to 30 mm. in diameter.
- It is also conspicuous when seen from the side. Otherwise the
structure of the flowers agrees with that of Cnicus arvensis ; but
_ the list of insect-visitors is limited by the greater depth of the
_ throat of the corolla.

Visitors : A. Hymenoptera—Apide: (1) Bombus agrorum, F. &% 2, s. ;
_ (2) B. lapidarius, L. § g,8., both ab. (the males as late as October 2) ; (3)
' Halictus cylindricus, F. ¢,s.; (4) Osmia fulviventris, Pz. ?, cp. ; (5) Stelis

_ aterrima, Pz. 2,8. B. Diptera—Syrphide ; (6) Eristalis tenax, L., s. and f.p., ab.
_ ©. Lepidoptera—(7) Pieris napi, L., s. ; (8) P. rape, L. See also No. 590, 11.

246, CARDUUS ACANTHOIDES, L.—The capitulum is even more
conspicuous than in C. crispus, since the narrow segments of the
- corolla are 7 to 8 mm. long (instead of 4 to 53). ‘The honey is
more easily accessible, for the throat of the corolla is wider than in
C. crispus and only 2 mm. long (instead of 23 to 3). Moreover
C. acanthoides (at Miihlberg, in Thuringia) grows associated in
much greater numbers than C. crispus (at Lippstadt). These three
circumstances account for the very much greater number and
variety of insect-visitors in the case of CO. acanthoides, whose flower
_ has otherwise the same structure as that of C. crispus.

A. Hymenoptera—(a) Apide: (1) Bombus lapidarius, L. § ; (2) B. silva-
rum, L. § 2; (3) B. muscorum, F. §; (4) B. pratorum, L. ¢; (5) Dasypoda
_hirtipes, F. 9; (6) Cilissa tricincta, K. (leporina, Pz.), 2; (7) Halictus inter-
' ruptus, Pz. ¢; (8) H. nitidiusculus, K. ¢ 9; (9) H. albipes, F. ¢, ab. ; (10)
| # quadricinctus, F. ¢ 9, very ab.; (11) H. rubicundus, Chr. ¢ 9, freq. ;
| e.?) H. longulus,Sm. ¢ 2; (13) H. cylindricus, F. ¢; (14) H. quadrinotatus,
. XK. dg, scarce; (15) H. maculatus, Sm. ¢ 9; (16) H. minutus, K. ¢; (17)
_H. lucidulus, Schenck, ? ; (18) H. Smeathmanellus, K. 9, all (1—18) s., only;
_ H. quadricinctus, , ¢.p. also ; (19) H. leucozonius, K. ¢ 9, s. and c.p. ; (20)
Osmia spinulosa, K. ?, very ab., s. and c.p. ; (21) O. enea, L. g, 8. 3 (22) O.
aurulenta, Pz. 9,s. and c.p.; (23) O. fulviventris, F. 9, s. and cp. ; (24)
I Megachile lagopoda, K. 2 ¢,s. and c.p.; (25) M. centuncularis, L. ¢,s. ; (26)
_ M. versicolor, Sm. 9, s. ; (27) Chelostoma campanularum, L. ? ¢, s.and cp. ;
| (28) Heriades truncorum, L. ? ¢, 8. and ¢. p.; (29) Stelis pheoptera, K. 9,
- not rare ; (30) St. aterrima, Pz. 9 ¢, freq. ; (31) St. breviuscula, Nyl. 9 ; (32)
Prosopis punctulatissima, Sm. 9. By far the most important visitors are the.
bees with abdominal collecting-brushes, I have found Osmia spinulosa on

Carduus acanthoides in the same abundance, and working with the same dili-
gence, as Megachile on Onopordon. (b) Vespide : (33) Cerceris variabilis,
Schrk. 9,s. B. Diptera—(a) Syrphide: (34) Eristalis arbustorum, L., s. ;

: : Z2

340 THE FERTILISATION OF FLOWERS. [PART LIL.

(b) Conopide : (35) Conops scutellatus, Mgn. ; (36) Physocephala rufipes, F., —
both s. C. Lepidoptera—(a) Rhopalocera : (37) Pieris brassice, L.; (38)
Argynnis Aglaia, L. ; (b) Sphinges : (39) Zygena carniolica, Scop. ; (¢) Noctuee :
(40) Plusia gamma, L., alls. D. Coleoptera—(a) Elateride : (41) Corymbites
holosericeus, L. ; (b) Lamellicornia: (42) Trichius fasciatus, L. ; (¢) Cureu-
lionide : (43) Larinus Jacee, F. ; (d) Chrysomelide : (44) Cryptocephalus seri- —
ceus, L. See also No. 590, Il.

247. CarDUUS NuUTANS, L. :—

Visitors : A. Hymenoptera—Apide : (1) Bombus hortorum, L. g; (2) B.
pratorum, L. % ¢ ; (3) B. vestalis, Fourc. ¢ ; (4) Halictus cylindricus, F. ¢;
(5) H. malachurus, K. 9, alls, B. Lepidoptera—Sphinges: (6) Zygena loni-
cere, Esp. See also No. 590, III.

Carduus defloratus, L.—I have seen this species visited by 103°
species of insects, of which fifty-four were Lepidoptera, mostly”
butterflies (609).

248. Cnicus (CIRSIUM) ARVENSIS, L.—Somewhat over a
hundred florets are united in one capitulum. The tube of each
floret is 8 to 12 mm. long, the wider throat 1 to 13 mm. long, —
and the five linear, slightly divergent segments are 4 to 5 mm.
long. The capitulum is scarcely 8 mm. in diameter in its lower —
bracteate portion, but when seen from above it forms a red surface —
20 mm. or more in diameter. Since the honey rises up into the
throats of the florets, numerous insects of various orders, attracted
by the conspicuous capitula, are able to enjoy it. A proboscis
need only be 1 to 1} mm. long to reach to the bottom of the —
throat of a floret, so that the rich store of honey is accessible not
only to bees and Lepidoptera, but also to wasps, flies, and beetlés, —
which seek it diligently. In the first stage of the flower, a large
quantity of pollen emerges at the upper end of the anther-
cylinder, pressed up by the lengthening style. Owing to their
slight stickiness and to the possession of sharp processes over —
their whole surface (Fig. 114, 2, 3) the pollen-grains adhere easily
to one another and to the hairs upon the insect. Gradually the _
style itself protrudes 2 to 2} mm. from the anther-cylinder. At —
its end it divides into two branches nearly 2 mm. long, which are |
thickly covered on their outer surface with small, sharp hairs
(Fig. 114, 5, ¢). Immediately below the division of the style,
this hairy surface ends in a ring of longer hairs (0). On emerging
from the anther-cylinder the tip of the style is thickly covered all
round with pollen; if sufficient insect-visits occur, (and in fine”

i
i

V4
‘e
| 4
D f
?
5
:
y

PART III. } THE MECHANISMS OF FLOWERS. 341

weather they never fail) the pollen is in a short time all removed.
But if insects do not visit the flower until the stigmatic edges of
the branches of the style have already bent outwards, then self-

fertilisation is possible, since in this case the hairs of the style
_ still remain covered with pollen. If insects do not visit the flower
at all, some of the pollen-grains, which hang in little clumps

Fie. 114,.—Cnicus arvensis, L.

1.—Flower, in first stage ; pollen issuing from the anther-eylinder.
2.—Pollen-grain (x 400).
3.—Ditto, in optical section.
4.—Flower, in second stage. The pollen has been removed by insects and only a few grains
remain upon the style; the style projects far beyond the anther-eylinder, and its stigmatic branches
are closely applied together.
__ 5.—Upper part of style with its ring of long hairs (bb), and lower part of its two stigmatic
¢ peeceee; the latter are covered outside with short hairs, and on the edges with stigmatic papille

a ).
_. 4, anther-cylinder; b, ring of long hairs; ¢, short hairs; d, stigmatic papil’e; e, pollen.~

~~

to the hairs, may easily fall of themselves upon the stigmatic
_ papillee. In fine weather, and in the open air, this can scarcely
_ ever take place, for Cnicus arvensis is one of the most abundantly
visited of all our native plants. ‘As the following list shows, very
_ few insects resort to it for the sake of its pollen, but very many for

its honey :—

342 THE FERTILISATION OF FLOWERS. | PART IIL,

Visitors: A. Hymenoptera—(a) Apide : (1) Apis mellifica, L. §, in great
abundance, some c.p., mostly sucking ; (2) Bombus lapidarius, L. 9, s. ; (3)
B. hortorum, L. ¢, s. ; (4) Dasypoda hirtipes, F. 9 ¢, ep. ands., the g
numerous ; (5) Cilissa leporina, Pz. ¢, s., freq. ; (6) Andrena fulvicrus, K. 9 ;
(7) A. dorsata, K. 2 ¢, ab. ; (8) A. Gwynana, K. ? @, freq. ; (9) A. nana, K.
& ; (10) A. pilipes, F. ¢ ; (11) A. vitrea, Sm. (= nitens, Schenck), ¢, Cassel ;
(12) Halictus flavipes, F. 2 ; (13) H. longulus, Sm. ¢; (14) H. tarsatus, Schenck,
2; (15) H. nitidiusculus, K. ¢; (16) H. minutus, K. 9 ; (17) H. maculatus,
Sm. 9; (18) H. cylindricus, F.? ¢, very ab. ; (19) H. albipes, F. ¢ ; (20)
H. rubicundus, Chr. ¢; all the species of Andrena and Halictus and all the
following bees only suck honey ; (21) Nomada Solidaginis, Pz. 9 ¢ ; (22) N.
Roberjeotiana, Pz. 9 ¢; (23) N. lineola, Pz. 2? ¢, ab.; (24) N. nigrita,
Schenck, ¢; (25) N. Jacobeee, Pz. 9 ¢, ab. ; (26) Epeolus variegatus, L. 2 ¢,

scarce ; (27) Sphecodes gibbus, L. 2 ¢, several varieties, including ephippia,

L. ; (28) Prosopis communis, Nyl. 9, ab. ; (29) P. confusa, Nyl. (hyalinata,
_$m.),? ¢; (30) P. sinuata, Schenck, ¢ ; (31) P. variegata, F. 2 ¢, ab.; (32)
Heriades truncorum, L. 2; (b) Sphegide: (33) Crabro cribrarius, L. 2 ; (34)
Cr. alatus, Pz. 2 ¢, very ab.; (35) Lindenius albilabris, F. 9 ¢ ; (36) Oxybelus

trispinosus, F. 2; (87) O. uniglumis, L. 9 ¢, ab.; (38) Cerceris arenaria, L. ©

2g, not rare; (39) C. nasuta, Kl. 9 ¢, ab. ; (40) C. variabilis, Schr. 9 ¢,
very ab. ; (41) Philanthus triangulum, F. ¢ ¢, freq. ; (42) Bembex rostrata,
L. 2 ; (43) Dinetus pictus, F. 2 ¢ ; (44) Ammophila sabulosa, L. ; (45) Salius
sanguinolentus, F., all s. ; (¢) Chryside: (46) Hedychrum lucidulum, Latr. 9,
s.; (d) Ichneumonide : (47) Various sp. ; (e) Tenthredinide: (48) Tenthredo
notha, K1. ; (49) Several undetermined sp., s. B. Diptera—(a) Stratiomyide :
(50) Odontomyia viridula, F., not rare, s.; (6) Tabanide : (51) Tabanus rusticus,
L., s., freq.; (¢) Bombylide: (52) Anthrax flava, Mgn. (Thuringia) ;
(d) Syrphide ; (53) Syrphus sp.; (54) Melithreptus teniatus, Mgn. ; (55)
Eristalis sepulcralis, L. ; (56) E. eneus, Scop.; (57) E. tenax, L.; (58) E.
arbustorum, L. ; (59) E. nemorum, L., all ab., s.; (60) E. intricarius, L. ; (61)
Syritta pipiens, L., ab. ; (e€) Conopide: (62) Conops flavipes, L. ; (63) Physo-
cephala rufipes, F., s., freq.; (f) Empide: (64) Empis livida, L., 8.3 (g)
Muscidae : (65) Ocyptera brassicaria, F. ; (66) O. cylindrica, F., both freq., s. ;
(67) Sarcophaga carnaria, L., s. ; (68) Onesia floralis, R. D. ; (69) Lucilia seri-
cata, Mgn. ; (70) L. cornicina, F., ab., s. ; (71) Musca corvina, F., s., ab. ; (72)
Oliviera lateralis, F., s. ; (73) Platystoma seminationis, F. OC. Lepidoptera—
(a) Rhopalocera: (74) Vanessa urtice, L.; (75) Pieris brassice, L., freq. ;
(76) Rhodocera rhamni, L. ; (77) Hesperia silvanus, Esp. ; (78) Satyrus Janira,
L, ; (79) Thecla rubi, L. ; (b) Sphinges: (80) Zygena carniolica, Scop. (Thu-
ringia), alls. ; D, Coleoptera—(a) Elateride : (81) Agriotes gallicus, Lap.
(Thur.) ; (82) A. ustulatus, Schaller (Thur.) ; (b) Lamellicornia: (83) Tri-
chius fasciatus, L.; (c) Mordellide : (84) Mordella fasciata, L.; (85) M.
aculeata, L., both freq. ; (d@) Malacodermata : (86) Telephorus melanurus, F.;
very abundant, thrusting their heads into the tube, and also pairing upon’ the
flowers ; (¢) Curculionide : (87) Bruchus, sp. ; (88) Larinus Jace, L, (Thur.).
See also No. 590, 111, for additional visitors in Low Germany. A list of

Alpine visitors (four Coleoptera, six Diptera, seven bees, one Sphegidee, and

fourteen Lepidoptera) is given in my Alpenblumen (No. 609).

ae

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a ee ee ee ee

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foe SCS elgg. IRE eet SR tg. id te ree

PART III. | THE MECHANISMS OF FLOWERS. 343

249, Cnicus (CIRSIUM) OLERACEUS, L,

: _ Visitors: A. Hymenoptera—Apide: (1) Apis mellifica, L. 8, 5. ; (2)
Bombus, s. B. Lepidoptera—Noctue : (3) Euclidia glyphica, L.,s. See also
i. No. 609.

.

I have not investigated the flowers closely.

250. CNICUS LANCEOLATUS, Scop.—The chief difference be-

- tween the flowers of this species and of C. arvensis is that here the
honey is much less accessible. For not only are the narrow tubes

of the florets, and accordingly the involucre also, much longer

(16 to 18 mm.), which has no effect on the accessibility of the

honey ; but the throat, in whose base the honey collects, is also

- much longer (4 to 6 mm. against 1 to 1} in C. arvensis), From

_ this cause the variety of insect-visitors is greatly limited ; but the

flowers are all the more diligently visited by long-proboscised bees,

especially humble-bees.

P Visitors : A. Hymenoptera—(a) Apidew: (1) Apis mellifica, L. % ;. (2)
Bombus terrestris, L. § ¢; (3) B. agrorum, F. § ¢ ; (4) B. lapidarius, L.
% g (as late as Oct. 9, 1869 !), all four ab.,s.; (5) B. campestris, Pz. ¢, s. ;

_ (6) Megachile maritima, K. 2, cp. ; (b) Vespide : (7) Polistes gallica, L., and

var. diadema, freq. (s.?). B. Diptera—Syrphide : (8) Eristalis tenax, L. ; (9)

E. arbustorum, L. ; (10) E. nemorum, L., all three f.p. and s., very ab. (as

late as Oct. 13, 1874). C.- Lepidoptera—Rhopalocera : (11) Pieris brassice, L.,
ab., s. ; (12) Hesperia sp.,s, See also No. 590, 111, and No. 609.

251. CNICUS ERIOPHORUS, Scop., is visited very abundantly in

Thuringia by Megachile lagopoda, K. 9 4,8. and c.p. On the Alps

I have found it visited by humble-bees and by various Fritillaries
- (Argynnis) (600).

252. CNICUS OCHROLEUCUS, All., has yellowish-white flowers,
and is also visited on the Alps by lambletheds and nich oe Sipe

__-:253. Cnicus PALustRIs, Scop., stands, in regard to the ac-
- cessibility. of its honey and the variety of its insect-visitors,
between ©. lanceolatus and C. arvensis. The throat is 24 mm.
i long (in C. arvensis 1 to 14, in C. lanceolatus 4 to 6); in all other
- points the flowers of these three species are alike in structure.

‘Visitors: A. Hymenoptera—(a) Apide: (1) Apis mellifica, L. o , very
| freq. s. ; (2) Bombus lapidarius, L. § a; c.p. and s. ; (3) B. pratorum, L. $,
) s.; (4) B. vestalis, Foure. @, s.; (5) B. Rajellus, Ill. 3, s.; (6) Andrena
| - Coitana, K, 9,s.; (7) A. Gwynana, K.g, s. ; (8) Halictus eylindricus, F.? ¢,

=

hi

344 THE FERTILISATION OF FLOWERS. [PART IL

cp. and s., very freq. ; (9) Megachile centuncularis, F.. ¢, s. ; (b) Sphegide :
(10) Lindenius albilabris, F.. B. Diptera—(a) Syrphide : (11) Eristalis tenax,
L., s and f.p.; (12) Volucella bombylans, L., do. ; (13) Syrphus tricinetu
Fallen, f.p.; (6) Conopide : (14) Sicus ferrugineus, L., s. C. Lepidoptera—
(a) Rhopalocera: (15) Pieris brassicae, L. ; (16) P. rape, L. ; (17) P. napi, L. ;
(18) Hesperius silvanus, Esp. ; (19) Satyrus Janira, L.; (5) Noctue : (20)
Plusia gamma, L., all rather freq.,s. D, Coleoptera—(a) Elateride: (21)
Agriotes ustulatus, Schaller (Sid.).; (6) Cerambycidw: (22) Strangalia
melanura, L, (Sld.), ab. See also No. 590, 111., and No. 609.

Cnicus palustris and C. arvensis are gynodicecious according to
Darwin (167). ‘a
Cnicus acaulis, All., is visited by humble-bees and by Lepi-
doptera (590, 609). |
Cnicus spinosissimus, Scop.—The tube of the corolla is 8
9 mm., the throat 4 to 5 mm. long. The insect-visitors are very
numerous and various (609). ) | a?

254. CNICUS HETEROPHYLLUS, All.—Several hundred florets
unite to form a capitulum (I have counted 259). The tube is
15 mm., the throat 8 mm. long. I have seen the flower visited by
Bombus mesomelas, 9 (18 to 20) (609).

255. ONOPoRDUM ACANTHIUM, L.—In each floret the honey
rises in the tube, which is 10 to 12 mm. long, up to the cylindrical
somewhat swollen throat, which is 3 to 4 mm. long, and which
divides above into five linear segments, 6 to 8 mm. long; these
segments do not diverge, but are continued straight upwards from
the throat of the corolla. The length of the tube of the corolla
in this plant, and in most other Cynarez, has no influence on the —
accessibility of the honey, since the latter rises up into the throat ;_
it is due only to the development of the involucre, which gives
effectual protection to the buds by completely surrounding them —
in the form of a deep cup; the long tubes also serve to increase —
the conspicuousness of the flower, as they bend more and more —
outwards the nearer they are to the margin. The branches of
the style are 3 to 4 mm. long; they seem never to diverge in —
Onopordum, but remain closely appressed. They bear on thei
outer edges rows of stigmatic papillae, which in the second (female) —
stage of the flower turn more outwards and expose themselves to
the touch of insect-visitors. One millimetre below its division
into two branches, the style bears a ring of short hairs, which
pomt obliquely upwards and are long enough to sweep the an-_
ther-cylinder (} mm. wide; 8 to 10 mm. long) clear of pollen.

PART III. | THE MECHANISMS OF FLOWERS. 345

_ Although in the first stage this cylinder, coated above with pollen,
and in the second the tip of the style, with its two rows of stigmatic
} - papille, projects 5 to 7 mm. above the segments of the corolla,
many florets are fertilised simultancously by the bees which
a visit the flowers, particularly by those with abdominal collecting
i brushes, which diligently sweep up the pollen upon the surface af
the capitulum.

Hl On the southern slopes of Miihlberg and Wandersleber
_ Schlossberg in Thuringia, where I observed Onopordum, the two
_ handsomest thistles, Onopordwin Acanthium and Cirsium ertophorum,
_ were fertilised chiefly by the handsomest of the tailor-bees, Megachile
| lagopoda, K. ‘The females fly boisterously on to a thistle-head
and brush hurriedly over it, holding the abdomen sometimes so
high that one can see from far off the red, hairy coat of its under
_ side, or the blue pollen adhering to it. The mid and hindlegs
are actively occupied meanwhile in a backward scratching move-
ment, and the head is sunk among the florets. As a rule the
female turns once round upon the capitulum in brushing off its
pollen. On leaving one capitulum it flies at once to another, ©
until, being laden with sufficient pollen, it flies off to its nest.
‘The males also sit occasionally sucking honey upon these thistle-
heads, but they are much more occupied in pursuing the females.
Delpino’s generalisation, based on insufficient observations, that
_ Composite whose florets are packed closely together to form a level
surface are fertilised by bees with abdominal collecting-brushes,
‘while those whose essential organs are long and widely separate
are fertilised by Halictus, is shown to be incorrect by this and by
many more of my observations.

i. Visitors (in Thuringia): A. Hymenoptera—(a) Apidae: (1) Megachile
lagopoda, K. ? ¢, cp. and s., in extreme abundance ; (2) Osmia fulviventris,
| Pz. 9 f, cp. ands. ; (3) O. spinulosa, K. 9, ep.: (4) Coelioxys conoidea, Ill.
9,s.; (5) Stelis aterrima, Pz. 9 3,s.; (6) Andrena Schrankella, N. 9; (7)
_ Halictus quadristrigatus, Latr. 2, s. ; (8) Saropoda bimaculata, Pz. 2, s. ; (9)
oe lapidarius, L., $,s. ; (10) B. terrestris, L. 9, s.; (11) B. rupestris,
om 9,8. ; (0) Sphagidin : (12) Psammophila affinis, K. 9,s. B. Lepidoptera

| (a) Rhopalocera : (13) Vanessa urtice, L., s.; (14) Satyrus Galathea, L., s. ;
_ (b) Sphinges : (15) Macroglossa stellatarum, e s. C, Coleoptera—(16) Cocci-
- nella mutabilis, Scriba, trying vainly to reach the honey. D. Hemiptera—
(17) Capsus, two species, s. See also No. 590, 11., and No. 609.

_ 256. SERRATULA TINCTORIA, Lae

_. Visitors (at Mithlberg in Thuringia, Sept. 1871): A. Hymenoptera—
. - Apide : (1) Bombus agrorum, F. ? ¢,s.,ab. B. Lepidoptera— Rhopalocera :
(2) Colias hyale, L., s., ab.

346. THE FERTILISATION OF FLOWERS. [PART 1 L

In this species there exist female and hermaphrodite plants
with a close series of intermediate forms. The seeds of the female
flowers are larger than those of the hermaphrodite."

257. CENTAUREA JACEA, L.—The capitulum contains as a rule
from sixty to over a hundred florets; in these the tubular part of

Fic, 115.

1—4,—Centaurea Jacea, L.

1.—Upper part of the flower, in first stage (x *).

2.—Ditto, in second stage.

3.—Section of anther-cylinder, before the pollen has been shed. : ;
; ‘ie oe of style, removed from the anther-cylinder, and divested of pollen, to show the fine
iairs,

5.—Centaurea Cyanus, L. End of style, more magnified.
a, anther-cylinder; b, valvular appendages of the anthers, which at first close the ee
anther-cylinder; ¢, pollen; d, style; e, ring of sweeping-hairs ; f, division of the style ; 9,8
surface ; h, hairs (teeth) upon the filaments, to guard the honey.

of the
granie

the corolla is 7 to 10 mm. long, the expanded bell-shaped part:
3 to 4 mm, long, and the long, linear segments about 5 mm. long.
The capitulum is only 8 to 10 mm. in diameter on a level with the

’ Sir J, Smith, Trans. Linn. Soe. xiii. p, 600, quoted by Darwin, No, 167.

vari] THE MECHANISMS OF FLOWERS. 347

t Seabular parts of the florets, but since these bend over at their upper
ends more and more the nearer they stand to the edge and diverge
- outwards around the capitulum, a capitulum in full ‘bloom ems a
red circular area 20 to 30 mm. in diameter. When a floret opens,
its style has the position represented in Fig. 115, 3 ; its two stigmatic
divisions are closely appressed and inclosed in the upper part of
“the cylinder formed by the coherent anthers ; a ring of hairs (Fig. 115,
3, 4, ¢), directed obliquely upwards and tiaching the inner wall of
the anther-cylinder all round, has swept all the pollen into this
“upper part of the cylinder, so that the branches of the style are
closely packed round with pollen. If the flowers in this stage are
left untouched for a day or two in a room, the terminal valves of
. ‘the anther-cylinder. separate, and a little pollen appears between
em atthe top. But if one now touches the filaments with a needle
‘or a sharp pencil (as in a natural condition the insect’s proboscis
loes), a great quantity of pollen is in a short time seen to emerge,
and the anther-cylinder is seen to be drawn down so far by the
contracting filaments that the branches of the style protrude
above. Since their whole outer surface is covered with small hairs
directed obliquely upwards, they remain, after emerging from the
anther-cylinder, so thickly coated with pollen, that they are not
Tecognisable as branches of the style until the pollen has been
brushed away.

Gradually the style grows up still further beyond the anther-
cylinder (Fig. 115, 2); the edges (set with stigmatic papillz) of the
inner surfaces of the two branches of the style bend outwards
, 2); and the ends of these branches also gape asunder, so that
‘here also stigmatic papille are exposed to the touch of insect-
“visitors. Spontaneous self-fertilisation can under these circum-
/ stances not occur, and self-fertilisation can only be brought about
| by insects, if, at the time when the stigmatic papille become
: ‘exposed, the outer surfaces of the branches of the style or the ring
| of hairs are still dusted with pollen ; on the other hand, if sufficient
insect-visits occur, cross-fertilisation is fully insured. Although
‘the expanded portion of the corolla is longer than in most of our
other native Composite, and many short-lipped insects (sand-wasps
sand the majority of flies) are therefore excluded from the honey,
yet, in consequence of the great amount of its honey, it is one
of the most frequented forms. Various species of bees come in
numbers and pay lengthy visits to its capitula, and in creeping
between the anther-cylinders and styles protruding from the florets,
they bring not only their under-sides, but the greater part of their

|

|

348 - THE FERTILISATION OF FLOWERS. [PART HII.

hairy bodies in contact at one time with pone and at another
with stigmatic surfaces.
The following insects effect fertilisation :—

A. Hymenoptera—(a) Apidae: (1) Apis mellifica, L. 9, ab.,s. ; (2) Bom-
bus silvarum, L. 9 $,s.; (3) B. agrorum, F. $,s. ; (4) B. pratorum, L. 4,
s.; (5) B. rupestris, F., 9 ¢,s.; (6) B. lapidarius, L. $,s. ; (7) B. campestris,
Pz. ¢, s.; all the humble-bees dust chiefly their head, belly, and legs ; (8)
Saropoda bimaculata, Pz. 9 ¢, very ab.; (9) Dasypoda hirtipes, F. g,s.,
freq. ; (10) Andrena pilipes, F. 9, ¢.p.; (11) Halictus maculatus, Sm., 2 ¢,
ep.and s.; (12) H. quadricinctus, F, 9 g,cp. and s., ab. ; (18) H. rubi-
cundus, Chr. 9 ¢, ¢.p. and s.; (14) H. leucozonius, K. 9 3,¢-p. and s. ; (15)
H. interruptus, Pz. g,s.; (16) H. cylindricus, F. ‘ dg, ¢.p. and s., very ab.
(17) H. nitidiusculus, K. ¢ 9,8. and ep. ; (18) H. albipes, F. $e ; (19)
H. longulus, Sm. 9 ¢; (20) H. zonulus, Sm. 3,8. ; (21) H. minutus, K. ¢,
s.; (22) H. lucidulus, Schenck, ? ; (23) H. Smeathmanellus, K. 9°, both s.
and c.p.; (24) Nomada succincta, Pz. 3,8. ; (25) Osmia spinulosa, K. Q,
ep. (Thur.) ; (26) Megachile centuncularis, L. 9 ¢,s. ; (27) M. lagopoda, K.
2, cep. (Thur.); (28) Anthidium strigatum, Latr. ?, ¢.p. (Thur.) ; Oy
Vespide : (29) Polistes gallica, F. (Thur.). B. Diptera—(a) Empide : (30)
Empis rustica, F., s.; (b) Syrphide : (31) Helophilus pendulus, L., s. ; (32)
Eristalis tenax, L., sometimes c.p., sometimes trying to thrust its yather thi
proboscis into the narrow florets ; (33) Rhingia rostrata, L., s. ; (@) Conopicta
(34) Physocephala vittata, F., s. ; (35) si flavipes, L., s. et Lepidoptera
—(a) Rhopalocera: (36) Pieris Heche .; (87) P. napi, L. ; . (38) Colias. 7
hyale, L. ; (39) Polyommatus Phlceas, L ; (40) are sp.; (41) Satyrus |
Galathea, L. ; (42) S. Megeera, L. ; (43) S. J anira, L.; (44) S: pamphilus, L. ;
(45) Hesperia thaumas, Hfn.; (6) Sphinges: (46) Zygeena loniceree, Esp. 5
(47) Z. carniolica, Scop. (Thur.); (c) Noctuw: (48) Plusia gamma, L. Se
also No, 590, 111., and No, 609.

I became aware in August, 1881, that the capitula of Centawrec
Jacea tend to vary along two lines from the commonest and appa
rently most primitive form which I have just described. The res
is, on the one hand, very conspicuous male capitula 50 to 55 mm
in diameter, and on the other hand less conspicuous female eapitula
30 to 35 mm, in diameter. In both of these extreme forms the
marginal florets have the corolla greatly enlarged, but the repre
ductive organs functionless. In the male capitula, the florets «
the disk possess a style as well as anthers, but its stigmas neve
separate, but coalesce in their lower part. In the female capit
the anthers of the disk-florets are brownish, shrunken, and devoid
of pollen. 4

‘

* eS all lO ary. ec lt ll a Satay woicdind

Bs

These extreme forms are connected by an unbroken series
transition-stages with the primitive form. As the primitive form
began to vary in one direction, the marginal florets became gradually

parti} | THE MECHANISMS OF FLOWERS. 349

longer and more radiating, and their reproductive organs diminished

eapitula were complete.

_ Varying in the opposite direction, the corolla in some of the
_ marginal florets got smaller, and gradually the anthers became
_ brown and devoid of pollen; the same changes proceeded step by
step towards the centre of the flower, until now we find the whole
_capitulum consisting only of female florets, and measuring only
15to18mm.indiameter, When this state was reached, the corollz
of the marginal florets began again to increase in size and to radiate
outwards, their anthers vanished completely, and their stigmas ceased
to unfold.

_. The capitula on the same plant are always much of the same
form. In any locality where capitula of the primitive form occur
along with female capitula, Centaurea Jacea may be said to be
& mnodicecious. But since in the outset of the last described series
of changes the outer florets become purely female, before the
conspicuousness of the head is visibly diminished, it is clear that
my explanation of the origin of gynodicecism suggested in the
eases of Thymus and Glechoma cannot hold in this instance.
It seems much more likely here that the reduced size of the
: corolla in the female flowers is the result of a tendency to
abortion, spreading from the stamens to the corolla. This is
_ Darwin’s explanation of all cases of gynodicecism (No, 167,
| chap vii.; 611).

| ’ _ 258. CENTAUREA Scapiosa, L., agrees in the whole structure
| of its flower with the previous species, but differs only in its honey
' being more easily accessible. For while the tubular parts of the
_ disk-florets are longer than in the previous species (11 to 12 mm.),
_ the expanded part above, which becomes filled with honey, is
“shorter (32 to 4 mm.), and while in the primitive form of C. Jacea
_ the marginal florets and the disk-florets were alike, I have always
- found in C. Scabiosa the marginal florets devoid of stamens and
| style, devoid of a wide superior portion (or throat), but notably
larger (16 to 22 mm. long), with their tubes entirely directed out-
| wards and dividing into five linear segments, differing little from one
p another and about 2 mm: longer than those of the disk-florets.

| __ The less variety of visitors that I have observed is simply due
to the fact that I have only watched this species on a few occasions

1 4

350 THE FERTILISATION OF FLOWERS. [parr 11,

(in Thuringia), while I have met with C. Jacea in most of my
excursions in summer. a

Visitors (in Thuringia): A. Hymenoptera—Apide : (1) Apis mellifica, L,
%,s., ab.; (2) Bombus lapidarius, L. ¢; (3) B. terrestris, L. g; (4) B. mus.
corum, F. $ ¢, cp. and s.; (5) B. agrorum, F. 4; (6) B. silvarum, L. ¢;
(7) B. confusus, Schenck, ¢; (8) B. rupestris, F. 9; (9) Halictus quadri-
cinctus, F. 2 ¢, very ab., alls. ; (10) H. maculatus, Sm. ¢, e.p. ; (11) Mega-
chile ligniseca, K. ¢ ; (12) Osmia enea, L. 3, s. ; (13) O. spinulosa, K. 2, CP. 5
(14) Anthidium manicatum, L. ¢, s. B. Diptera—(a) Syrphide : (15
Eristalis nemorum, L. ; (6) Muscide: (16) Trypeta cornuta, F.C. Lepi-
doptera—(a) Rhopalocera: (17) Satyrus Janira, L. ; (18) Meliteea Athalia,
Esp. ; (0) Sphinges: (19) Zygeena carniolica, Scop. D. Coleoptera— Chryso-
melide : (20) Cryptocephalus sericeus, L. E. Hemiptera—(21) Capsus sp., s.
See also No. 590, m1. Thirty-eight Alpine visitors (two Coleoptera, two Diptera,
twelve Apide, twenty-two Lepidoptera) are given in my Alpenblumer
(No. 609). |

259. CeNTAUREA CyaNnus, L. (Fig. 115, 5)—In this species
also, the marginal florets serve only to attract insects, but they de
so in a more effectual way than in C. Scabiosa, for they are la
and infundibuliform and radiate outwards, extending the blue
surface of the capitulum from 20 to 50 mm. in diameter, and_
making it also conspicuous in side view. The honey is more easily
accessible, for above the narrow tubular part of the floret, which is
5 to 6 mm. long, the wider part is only 3 mm. long to the place —
where it divides into linear segments. In this species the simul-
taneous fertilisation of numerous florets goes on to a very sligh
extent ; for the florets of the disk are not numerous, and their anther
cylinders project at wide intervals. I have never seen the
irritability of the stamens more distinctly shown in any other
Composite. In flowers which I had allowed to develop in my room —
until the superior valvular appendages of the anthers hac
separated of themselves, the filaments contracted when I touched
them so much that the anther-cylinder was drawn down to an _
extent of 2 to 3 mm. very quickly, and then more slowly to an ex-_
tent of 5 to 6 mm.; in a few seconds a mass of pollen emerged
from the superior orifice of the anther-cylinder, and then graduall
the style protruded 3 to 4 mm. above the same orifice. In th
natural condition, I never succeeded in obtaining such distine
action on touching the filaments, doubtless because the filament
had almost always been touched by insects before they had reached
the full amount of tension. |

3
;
‘
}
’

Visitors ; A. Hymenoptera—(a) Apidw: (1) Apis mellifica, L. $, ab., s 3

PART III. | THE MECHANISMS OF FLOWERS. 351

() Sphegide : (4) Psammophila affinis, K., s. (proboscis 5 mm. long). B.
. D iptera—(a) Empide: (5) Empis livida, L., s., ab.; (6) Syrphide: (6)
Eristalis arbustorum, L., f.p. ; (7) Rhingia rostrata, L., s. C. Lepidoptera—
Noctue: (8) Plusia gamma, L.,s. See also No 590, 11.

Tribe Mutisiacee.

Chuquiraga insignis, R. Br.—The long, tubular florets of this
“Composite, which grows on the summits of the Andes (Pichincha),
are visited, according to Professor Jameson, by a humming-bird
ie Be sotrochilus Perk eakany. (Delpino, No. 185.)

Ve ene cleistogamic flowers of Anandria were known to Linneus

. von Mohl, No. 531).

Tribe Cichoriacee.

260. CicHoriuM IntTysBus, L.—The capitula are closed in
rainy weather, but expand in sunshine to form blue disks 30. mm.
and upwards in diameter. Each floret has a tube 3 mm. long and
a limb 13 mm. long, and this immense development of the limb
compensates for the small number of florets in each capitulum.
‘The structure of the florets agrees with that in Leontodon and
Hieracium, except that the branches of the style are much more
Erved, each making one to two spiral turns; self-fertilisation in
ence of insects is thus much more easily effected:

Visitors: A. Hymenoptera—Apide: (1) Apis mellifica, L. $,s., ab. ; (2)
Andrena fulvicrus, K. 9, c.p. ; (3) Halictus quadricinctus, F. ¢; (4) Nitidi-
sculus, K. ¢; (5) H. rubicundus, Chr. ¢; (6) H. longulus, Sm. 9; (7) H.
Ibipes, F. ¢, all s. ; (8) Osmia spinulosa, K. 9,8. and e.p. (Thur.), not rare.
iB Diptera—(a) Syrphide: (9) Syritta pipiens, L. ; (10) Eristalis tenax, L.,
be h species s. and c.p.; (b) Conopide: (11) Sicus ferrugineus, L.,s. C.
' ue pidoptera—Rhopalocera : (12) Colias hyale, L.,s. (Thur.). D. Coleoptera—
Malacodermata : (13) Malachius bipustulatus, F., fp., ab. An additional list
of nine bees is given in No. 590, II.

3 Hyoseris radiata, L., is visited by MMegachile centuncularis
(Delpino, No. 178, p. 125).

_ 261. LApsANA communis, L.—The capitulum consists of eight

'to seventeen florets, and expands to a yellow disk 8 to 10 mm. in

) diameter. In each floret the tube is 14 to 2} mm. long, and the
‘limb 4to 6 mm.long. The capitula are solitary and comparatively

| small; they are therefore not very conspicuous, and insect-visits —
are very few. In absence of insects, self-fertilisation takes place

larly, and it is doubtless effective, since the capitula are without

352 THE FERTILISATION OF FLOWERS. [PART III,

exception fertile. The anther- cylinder protrudes 2 to 3 mm,
from the tube, and the style 1} to 2 mm. beyond the anther-eylinder, :
The outer surface of the projecting portion of the style is covered
with pany hairs at wide intervals. The stigmatic branches are
only + mm. long, and are closely set with papillz on their inner
surfaces; they separate widely, and bring their papille vooulell ,
in contact with the pollen if insect-visitors have not removed it

from the hairs.

ape Scheie wee, (1) Eristalis arbustorum, L. ; 2) E. nemo-
rum, L. ; (3) E. sepulcralis, L., all three species f.p., not abundant. See also

No. 590, III.

262. PIcRIS HIERACIOIDES, L.—The capitulum is composed of
forty-four to seventy-five florets, which increase in size from the cen-
tre towards the circumference; itexpands insunshine to form a yelloy
disk 24 to 36 mm. in diameter, in dull weather it closes up till it
diameter is scarcely 7 mm. In each floret the tube is 4 to 6 mm. long
and the limb 8 to 12 mm. long. The stem is branched, and nearly
three feet high ; it bears numerous capitula, so that the whole plant
is very conspicuous. The honey rises into the upper and wider part
of the tube, and is therefore accessible to very short-lipped insects.
The anther-cylinder projects 5 mm. beyond the tube, and the style:
2} to 3} mm. beyond the anther-cylinder ; so that most insect-visitors
creep rather among than over the styles, and convey the pollen
rather with the hairs on their sides than with those on their under
surfaces; but bees with’ abdominal collecting apparatus are é
found upon the flowers.

The sweeping-hairs and the stigmatic papille are distribute a d
as in the other Cichoriacese (cf. Figs. 116, 117). The stigmati
branches usually spread apart as in other cases, but in several in=
stances I have seen the left bent over towards the right, and th
right towards the left, so close together that the stigmatic papillé
of the one were brushed by the pollen-holding hainas of the other.

Visitors : A. Hymenoptera—(a) Apide: (1) Panurgus calearatus, Sco |
?4,¢p. ands. ab. ; (2) Rhophites (Dufourea) vulgaris, Schenck, 9, ab., ¢
scarce, 8. and c.p. (Thur. Wald); (3) Halictus zonulus, Sm. 2; (4) H. leuec ;
zonius, Schr. 9; (5) H. sexnotatus, K. 9 ¢; (6) H. maculatus, Sm. 9; ( )
H. cylindricus, F., ¢; (8) H. quadricinctus, F. ¢; (9) H. rubicundus, Chr,
¢; (10) H. nitidinamiine i, d; (11) H. albipes, F. ¢; (12) H. longulus,
Sm. 94; (13) H. minutus, K. 9 ¢; (14) H. Smeathmanellus, K. 9, most
of these species in great numibers, the gs, the 9 cp. and s.; (15) Heriads
truncorum, L, 9, ¢.p. ; (16) Osmia spinuload K. 9,¢.p. (Thur.); (0) Sphegide
(17) Crabro sexcinetus, vy. d. L. 9. B. Diptera—(a) Empide : (18) Empi 1

parr] THE MECHANISMS OF FLOWERS. —_353

A livida, a very ab., 8. 5 (d) Syrphide : (19) Eristalis tenax, L. ; (20) E. arbu-
ig hyhe .3 (21) E. nemorum, L. ; (22) E. sepulcralis, L., all four uecice very
; (23) Syrphus balteatus, Deg. ; (24) Melithreptus scriptus, Ty .3 (25) M
ie Mgn.; (26) Chrysogaster viduata, L., all both f.p. and s. ©. Lepi-

doptera—Rhopalocera : (27) Pieris brassice, L, ; (28) P. rapa, L., both species
_ very ab. ; (29) Satyrus Janira, L., all three species s. See also No. 590, m1.

| Visitors : A. Hymenoptera—Apide: (1) Apis mellitica, L., $, s.; (2)
i os ealcaratus, Scop., 2 ¢, ¢p., 8, very ab. ; (3) P. Banksianus, Ko 4;
@~p., 8. scarcer ; (4) Dasypoda hirtipes, F. g,ab., even in the evening ; (5)
ae hophites (Dufourea) vulgaris, Schenck, 9 ¢, very freq. (Thur., Wald.) ; (6)
Andrena dorsata, K. 9, ¢.p.; (7) A. denticulaia, K. 9 g,¢p.and s. (Tekl.,
Borgst. ; Thur.) ; (8) A. fulvago, Chr. 9, ¢.p. (Thur.); (9) A. fulvescens, Sm.
9,cp. (Thur.) ; (10) A. parvula, K. ¢,s.; (11) Halictus longulus, Sm. 9 ;
pes?) H. maculatus, Sm. 9; (13) H. leucozonius, Schr. 2 ¢, freq. ; (14) H
ee naricns, F. 9 g, ab. ; (15) H. albipes, F. 9; (16) H. lugubris, K. ¢; (17)
. flavipes, K. ¢; (18) H. nitidus, Schenck, 9 ; (19) H. rubicundus, Chr. ¢ ;
6 0) iH. quadricinctus, F. ¢, ab. ; the ¢ of Halictus s., the 9 e.p. ands. ; (21)
Osmia spinulosa, K. 2, s. and c.p., very ab. (Thur.) ; (22) Chelostoma cam-
panularum, K. 9 g,s. and e.p., very ab. ; (23) Heriades truncorum, L. ? ¢,
gs, andc.p., very ab. B. Diptera—Syrphide: (24) Eristalis tenax, L. ; (25) E
“nemorum, L.; (26) E. arbustorum, L. ; (27) E. sepulcralis, L. ; (28) Syritta
pipiens, L., all five species s. and fip., very ab. ; (29) Syrphus sp., fp. ; (30)
Cheilosia chrysocoma, Mgn., f.p. C. Coleoptera—Nitidulide : (31) Meligethes,
ab. See also No. 590, m1.

E
hh

263. CREPIS BIENNIS, L. :—

264. CREPIS TECTORUM, L. :—

_ Visitors: A. Hymenoptera—(a) Apide : (1) Rhophites (Dufourea) vulgaris,
' Schenck, ? ¢, c.p. ands. ; (2) Andrena denticulata, K. 2 ¢ (Tekl., Borgst.) ;
(8) A. fulvicrus, K. 9, ¢.p. ; (4) Halictus villosulus, K. 9, ¢.p.; (5) H. rubi-
| ecundus, Chr. ¢,s.; (6) H. quadricinctus, F. ¢, ab. ; (7) Osmia spinulosa, K.
i. ,cp.,ab. (Thur.); (8) Heriades truncorum, L. ¢,s.; (b) Sphegide: (9)
a viaticus, L. 9,8. B. Diptera—Syrphide: (10) Cheilosia chryso-
soma, Megn., f.p. (Teklenburg, Herr Borgstette). See also No. 590, 11.

265. CREPIS VIRENS, Vill. :—

Visitors : A. Hymenoptera—Apide : (1) Panurgus calcaratus, Scop. ¢ dg,
‘ep. and s., ab. ; (2) P. Banksianus, 9'¢, scarcer ; (3) Rhophites (Dufourea)
vulgaris, Schenck, 2 ¢, c.p. and s., ab. ; (4) Dasypoda hirtipes, F. ¢, s. ; (5)
_ Andrena denticulata, K. 2, ¢.p. (Thur. ; Tekl., Borgst.) ; (6) A. dorsata, K. é
_ 8.3 (7) Halictus villosulus, K. 2, ¢.p. ; (8) H. cylindricus, F. 9, cp. ; (9) H

' minutus, K. 9, ¢p. B. Diptera—(a) Syrphidw: (10) Eristalis tenax, L., fip.;
' (11) Melithreptus scriptus, L., fp. ; (12) M. teniatus, Mgn., fp. ; (18) Syr-
_ phus balteatus, Deg. ; (14) S. ribesii, L. ; (15) S. arcuatus, Fallen, all three
= (16) Cheilosia chrysocoma, Mgn., fp. (Tekl. B.) ; (b) Conopide : (17)
| Sicus ferrugineus, L.,s. C. Coleoptera—Mordellide : (18) Mordella fasciata,
_ F. See also No. 590, 11. GK tit . u Rete

. AA

354 THE FERTILISATION OF FLOWERS. [parr 5

266. Hizractum UMBELLATUM, L.—The florets have a 7 e
3 to 5 mm., and an outer limb 8 to 16 mm. long, both increasing it
length gradually from the centre to the periphery of the capitulum, mM.
The whole capitulum, when fully expanded, forms a yellow disk
about 25 mm. in diameter. q

Honey is secreted by a ring round the base of the style, <
rises several millimetres in the tube: ; a proboscis 2 to 3 mm. itil a

'
rs

i
5

Fic, 116.
1—8 —Hieracium umbellatum, L.

1.—Floret, in second stage (x 7).
2.—The stigmas, still more revolute, so that self-fertilisation takes place if the pouens has not —
all been removed from the hairs. . J
H

8.—The portion a—b, of 1 (x 60).
4. H. pilosella, L. Floret in the act of self-fertilisation (x 7).
c, stigmatic papilla; d, sweeping hairs; e, pollen-grains; f, anther-cylinder; g, stamens
h, style; i, tube of corolla ; k, limb of corolla ; 1, pappus ; m, ovary.

suffices to reach it. Not only the two branches of the style (which |
are 2} mm. long) protrude from the anther-cylinder, but also
about 33 mm. of the style below its bifurcation; pollen rem ain
adhering to the sharp, bristly hairs (3, d@) with which the whole o:
the projecting part of the style is clothed. After emerging from
the anther-cylinder, the two branches of the style, which

partrun] § THE MECHANISMS OF FLOWERS. 355

_ covered all over their inner surface with stigmatic papille, spread
apart, and gradually bend so far backwards that part of their
_ stigmatic surface comes in contact with the hairs (Fig. 116, 2). Soif
the pollen has not been removed by insects, self-fertilisation takes
i pplace. If insect-visitors come in proper time self-fertilisation is
not impossible, but the chances are immensely in favour of cross-
F fertilisation, and of cross- -fertilisation with pollen from other capitula,
as the insect on alighting comes at once in contact with the upper

surface of the stigmas.

~

Visitors: A. Hymenoptera—(a) Apidw: (1) Apis mellifica, L. $, s. and
¢@p., ab. ; (2) Bombus lapidarius, L. §, s.; (3) Dasypoda hirtipes, F. 9, s.
and c.p. ; (4) Panurgus calearatus, Scop. 2 ¢,s. and c.p., very ab. ; (5) Halictus
- leucozonius, Schr. 9? ¢,'s. and «p.; (6) H. villosulus, K. 9 g, s. and cp. ;
; (7) Megachile argentata, F. yy 8. ; (8) M. Willughbiella, K. ¢,s. ; (9) Celioxys
Seiden, Ill. 2, s.; (10) C. simplex, Nyl. 9,8. ; (6) Chryside: (11) Hedy-
m lucidulum, Latr. ¢. B. Diptera—(a) Syrphide : (12) Eristalis tenax, L.
(as late as Oct. 13); (13) E. arbustorum, L. ; (14) Syrphus balteatus, Deg.,
all three species f.p. and s., very ab. ; (6) Conopide: (15) Sicus ferrugineus,
. L., ee Occemyia atra, F, eg es oe : (17) Pieris
-napi, L., ab. ; (18) Satyrus Megera, L. ; (19) Vanessa urtice, L., not rare ;
_ (20) Hesperia sp., alls. See also No. 590, II.

~~

_ 267. HIgRACIUM PILOSELLA, L.—Forty-two to sixty-four florets
unite to form a capitulum, and increase in size from its centre to its
circumference. In each the tube is 3 to 6 mm. long, and the limb 4
to 8mm. long. In sunny weather the capitulum expands to form
_ayellow surface 20 mm. in diameter, but in dull weather it closes up.
“4 n the bare slopes where the plant grows abundantly, its capitula are
conspicuous enough to attract numerous insects in spite of the small
size of the plant.

But on the whole, insect-visits are less abundant, though not
less various, than in the previous species, and accordingly, while
the flowers are in other respects similar, self-fertilisation is better
provided for by the greater involution of the stigmas (Fig. 116, 4).

Visitors : A. Hymenoptera—(a) Apide : (1) Panurgus calcaratus, Scop. ? ¢,
ep. and s., ab. ; (2) Andrena fulvescens, Sm. ?; (3) A. fulvago, Chr. ? ; (4)
Halictus leucozonius, Schr. 9; (5) H. villosulus, K. 2; (6) H. nitidus,
Schenck, 9, all c.p., the two Andrenez also s. ; (7) Ceratina ccerulea, Villa, ¢,
8, scarce ; (8) Diphysis serratule, Pz. ¢,s., scarce ; (9) Nomada Fabriciana, L.
-9,8.; (b) Tenthredinide : (10) Cephus, a small sp. B. Diptera—(a) Bombylide :
(1) Rombylivs canescens, Mik. (Sld.), s.; (0) Syrphide: (12) Helophilus
floreus, L., fp. C. Lepidoptera—(a) Rhopalocera: (13) Pieris brassice, L. ;
(14) Acetia argiolus, L. ; (b) Noctuew: (15) Euclidia Mi, L., all s. D. Cole-
eee) Cerambycide : (16) Leptura livida, L. ; (8) Chuunin aA

“A A 2

356 THE FERTILISATION OF FLOWERS. [PART

Cryptocephalus Mori, L., ab. ; (18) C. sericeus, L., ab. See also No. 590, UL,
for a further list of visitors in ‘Low Germany. A list of Alpine visitors (fo a
beetles, five flies, five bees, twenty-seven Lepidoptera) is given in my Alpen-
blumen (690).

268. HieRACIUM VULGATUM, L. :—

Visitors : A. Hymenoptera—Apide : (1) Bombus Rajellus, Ill. 9, s. ; (2)
B. terrestris, L. 9, s. ; (3) B. silvarum, L. 9,8. ; (4) Andrena Coitana, K. ¢@,s.
(5) A. fulvescens, Sm. 9, c.p.; (6) A. denticulata, K. g¢, s.; (7) Halictus
cylindricus, F. 9? ¢, cp. and s., ab. ; (8) Panurgus calcaratus, Scop. 9 ¢,
cp. and s, ab. B. Lepidoptera—Rhopalocera ; (9) Lycena icarus, Rott., s.
See also No. 590, III.

269. HyPpocHa@RIS GLABRA, L, :—

Visitors: Hymenoptera—Apide: (1) Rhophites (Dufourea) vulgaris
Schenck, 2, ¢.p. and s.; (2) Andrena fulvescens, Sm. 9, ¢. P. 3; (3) Hali 1s
nitidiusculus, K. 9 (Tekl., Borgst.); (4) H. cylindricus, F. 9, cp.; (5)
Sphecodes gibbus, L. ? ¢, s.

270. HypocH@RIs RADICATA, L.:—

Visitors: A. Hymenoptera—Apide: (1) Apis mellifica, L. 9, ep.; (2)
Bombus lapidarius, L. $, s. ; (3) Dasypoda hirtipes, F. 9, e.p., ab.; (4) Pan-—
urgus calcaratus, Scop. 2 ¢, s. and cp., ab.; (5) P. Banksianus, K. od, am
and ¢.p., scarcer ; (6) Colletes Davieseana, K. 2 ¢, cp. and s., ab.; (7) Rho-
phites (Dufourea) vulgaris, Schenck, ?, ¢.p. and s.; (8) Andrena xanthura,
K. 9,s.; (9) A. denticulata, K. 2 ¢, ep. and s, (Tekl., Borgst. ; Thur.) ; (10)
A. fulvescens,Sm. 9, ¢.p. (Thur.) ; (11) A. fulvago, Chr. 2, ¢.p. (Thur.); (12) _
Halictus villosulus, K. 2, ¢.p.; (13) H. malachurus, K. 2, e¢p.; (14) H.
lugubris, K. ¢ ; (15) H. flavipes, F. ¢; (16) H. leucozonius, Schr. 9 ¢,c¢.p.and
s.; (17) H. cylindricus, F.? ¢, ¢.p.ands. ; (18) H. rubicundus, Chr. ?, ¢.p.;(19)
H. sexstrigatus, Schenck, 9, ¢.p. ; (20) H. brevicornis, Schenck, ¢, s.; 2 j
Sphecodes gibbus, L. 9 ¢; (22) Diphysis ere Pz. g, s. B. Dipter
—(a) Syrphide : (23) Eristalis arbustorum, L. ; (24) E. nemorum, L, ; (25) |
E. sepulcralis, L., > ; (26) Pipiza funebris, Mgn., f.p.; (0) Conophdlae (27
Sicus ferrugineus, 1 .» 8 3 (c) Muscide : (28) Demoticus plebeius, Fallen, ¢,
See also No. 590, 111. and No. 609.

271, LEONTODON AUTUMNALIS, L.—The capitulum consists
forty to seventy florets ; it expands in sunshine to a diameter of 20 t
30 mim.,and closes up in rainy weather till its diameter is scarcely {
min; Tn each floret the tube is 2} to 5 mm. long, and the limb 7
to 12 mm, long. The honey rises up into the wider part of the
tube. The anther-cylinder projects 4 to 5 mm. from the tube, th
style 38 to 4 mm. beyond the anther-cylinder. The style is cove
on its outer surface with pointed sweeping-hairs, and is closely se

= is ae

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ui
Oy Am
Aig

--

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i

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———

ee

RT ILI. | THE MECHANISMS OF FLOWERS. | 357

mith stigmatic papilla on the inner surface of its branches, which
r the most part do not become entirely separated (Fig. 117, 2).

Here, as in Pieris hieracioides, insect-visitors come in contact with
the pollen and stigmas more with their sides than with their under
surfaces. Simultaneous fertilisation of numerous florets takes place

ae
r4
‘Tc
:
'
}
H
{
hy

| ta Fic. 117.—Leontodon auiwmnalis, L.
1.—Flore ee in second (female) stage, after removal of ory, and pappus (x 7).
it 2.—End o

the style in preceding figure (x 35). a, hairs; 6, stigmatic Pail: ¢, pollen-grains.
here, as in most Cichoriace, to a less extent than in those Seneci-
_ onides and Asteroidex in which the out-pressed pollen and after-
wards the stigmas lie in one plane. In this species, on the other
| hand, the florets are able at one and the same time to receive
| pollen from insects upon their stigmas, and to contre: their

eee the insect im turn.) i kn ae (SS

358 | THE FERTILISATION OF FLOWERS. [PART

If sufficient insects visit the flower in time to remove the pollen
from the sweeping-hairs before the stigmatic surfaces appear,
fertilisation is alone possible. If insect-visitors only come when
the branches of the style have begun to separate, then the possibility
of self-fertilisation by insect agency is not excluded. Even in absence
of insects, self-fertilisation seems to be not impossible, since when
the stigmas separate their edges curve outwards, and their papi
may easily come in contact with pollen still upon the hairs.

Visitors: A. Hymenoptera—(a) Apide : (1) Apis mellifica, L. §,s.; (2) Bom-
bus lapidarius, L. $, s. ; (3) Dasypoda hirtipes, F. 2, scrambling very rapidly
over the capitulum, sucking a few florets, and then flying away to another (the
enormously long hairs of the hindlegs carry huge balls of yellow pollen) ; (4
Panurgus calcaratus, Scop., s. and c.p. ; (5) Andrena fulvicrus, K. ?, ep. ; (6
Halictus leucozonius, Schr. 9, s. and c.p. ; (7) H. leucopus, K. 2 ; (8) H. longulus
Sm. 2, both species c.p. and s.; (9) H. Smeathmanellus, K. ¢ ; (10) H
morio, F. ¢; (11) H. maculatus, Sm. ¢ ;. (12) H. cylindricus, F. ¢, 9—12s.
(13) Diphysis serratulee, Pz. 2 ¢, scarce, s. ; (14) Prosopis armillata, Nyl. ¢,s.
(b) Sphegide : (15) Pompilus viaticus, L.,s. B. Diptera—(a) Syrphide: (16)
Syrphus pyrastri, L., ab. ; (17) 8. balteatus, Deg. ; (18) 8. nitidicollis, Mgn.
(19) Melithreptus teeniatus, Mgn. ; (20) Volucella bombylans, L. ; (21) Eriste
sepulcralis, L., ab. ; (22) E. arbustorum, L., very ab. (as late as Oct. 13) ; (23)
E. tenax, L., ab., all both f.p. and s. ; (6) Conopide : (24) Sicus ferrugineus, L., 8.
(c) Bombylide : (25) Systeechus sulfureus, F., s. ; (d) Muscide: (26) Sa
phaga carnaria, L., s. only. C. Lepidoptera— (a) Rhopalocera: (27) Co
hyale, L. (Thur.) s. ; (b) Noctuew ; (28) Plusia gamma, L. (as late as Oct. 14),8
See also No. 590, III. z

272. LEONTODON HASTILIS, L. (Koch) :—

Visitors: A. Hymenoptera—(a) Apide: (1) Bombus Barbutellus, K. 2
8.; (2) B. pratorum, L. 9, s. and c.p.; (3) Andrena fulvescens, Sm. 9, s. ¢ n¢
¢.p., dusting itself very thickly with pollen (Méhnethal) ; (4) A. Coitana, K
2,8. and c.p. (Sauerland) ; (5) Halictus villosulus, K. 9, ¢.p., ab.; (6) He
leucozonius, Schr. 9, c.p.; (7) H. cylindricus, F. 2, c.p., ab. ; (8) H. albipes
F. 2 (obovatus, K.), cp. ; (9) H. Smeathmanellus, K. 9, cp.; (0) Yen
thredinide : (10) Tenthredo sp., s, B. Diptera—(a) Bombylide: (11) Sys
teechus sulfureus, Mikan, s. (Sld.); (6) Syrphide: (12) Cheilosia sp. ; (13
Melithreptus teniatus, Meig., f.p. and s. (its stomach was quite full of a yelloy
mass of honey mixed with poets (14) Volucella pellucens, L., s., freq. (Sld.) 5
(15) Sericomyia lappona, L., s. (Sld.) ; (16) Eristalis horticola, Deg., fp. ant
8, (Sld.), ab. ; (17) E. arbustorum, L., f.p. and s., very ab. ; (c) Conopide : (18)
aie ierrugineus, L., s. C. Lepidoptera—Rhopalocera : (19) Hesperia silvanu:

sp., 8.

278. LEoNTODON (THRINCIA) HIRTUS, L.:—

Visitors : A. Hymenoptera—A pide : (1) Bombus confusus, Schenck, 3» &
(2) Panurgus calcaratus, Seop. 9 g, op. ands, ab. ; (8) Rhophites vuls

PART III. | . THE MECHANISMS OF FLOWERS. 359

Schenck, 2, c.p. and s. ; (4) Cilissa melanura, Nyl. ?; (5) Andrena denticu-
lata, K. 2, s. and ep. (Sid. Thur.); (6) A. fulvicrus, K. 2, ¢.p.; (7) A.
_fulvescens, Sm. 9, ¢.p. (Thur.) ; (8) A. fulvago, Chr. ?, cp. (Thur.); (9)
_ Halictus villosulus, K. ¢, c.p.; (10) H. leucozonius, Schr. 2 ¢, ep. and-s.,
_ very ab. (Thiringer Wald, August 30, 1869) ; (11) H. cylindricus, F. 2 ¢, cp.
- ands. ; (12) H. maculatus, Sm. ¢, s. ; (13) H.Smeathmanellus, K. 9, c.p. ; (14)
Hz. flavipes, F. ¢, s.; (15) H. lugubris, K. ¢,s. B. Diptera—Syrphide : (16)
Eristalis arbustorum, L., s. and f.p. ; (17) E. tenax, L., do., both species ab. ;
_ (18) Syrphus balteatus, Deg., do. C. Lepidoptera—Noctue: (19) Plusia
gamma, L., s. (as late as Oct. 14). See also No. 590, 111.

274. TARAXACUM OFFICINALE, L.—The capitulum consists of
_ about 100 to over 200 florets inserted on a receptacle only 5 to 7
“mm. in diameter. «In each floret the tube is 3 to 7 mm. long and
> the limb 7 to 15 mm. long, and in sunny weather the bapiéulum
_ expands to form a bright yellow surface 30 to over 50 mm. in
diameter. At night and in dull weather the capitulum closes up
_ so completely that only the green involucral bracts and the dark
_ outer surfaces of the limbs of the outermost florets remain visible.
_ The honey rises into the upper part of the tube (which is nearly
- filled by the style), and is therefore accessible to insects with very
_ short proboscides. From each tube an anther-cylinder 23 to 5
mm. long protrudes, and the style grows to a height of 3 to 5 mm.
_ above the anther-cylinder. The projecting portion of the style is
clothed with pointed hairs over its whole outer surface, which
retain entangled among them the pollen that they have swept out
of the anther-cylinder. The two branches of the style, which are
_ closely covered over their whole inner surfaces with stigmatic
_papiller, are 1} to over 2 mm. long; they bend outwards and
curve so far back that the tip of each makes 1 spiral turns, and
: accordingly, if insect-visits have not taken place and the sweeping-
hairs are still covered with pollen, self-fertilisation must take place -
‘to a great extent.
Thus in the Dandelion we have a plant which, by the great
conspicuousness of its flowers and the great abundance and ac-
cessibility of its pollen and honey, attracts an immense variety of
insects in sunny spring weather; but which has fully retained, or
has again acquired, the possibility of self-fertilisation, since it
_ begins to bloom so early that as a rule its first flowers receive no
insect-visits, while its latest flowers are also liable to be left
unvisited.
Visitors : A. Hymenoptera—(a) Apide : (1) Apis mellifica L. §,s.ande.p.,

very ab, ; (2) Bombus silvarum, L. ? ; (3) B. terrestris, L. 9 ; (4). B. muscorum,
oo; (5) B, lapidarius, L. ¢ ; (6) B. confusus, Schenck, ? ; (7) B, Barbutellus,

360 THE FERTILISATION OF FLOWERS. [PART II, .

K. 2; (8) B. vestalis, Fourc. 9, all s.; (9) Andrena cingulata, K. ¢; (10)
A. cineraria, L. 2? ¢; (11) A. pratensis, Nyl. 9; (12) A. nitida, K. 9 ¢; (18)
A. albicans, K. 9 ¢, very ab. ; (14) A. fulva, Schr. 9; (15) A. Gwynana,
K. 2 @, very ab. ; (16) A. helvola, L.? ¢, not rare ; (17) A. mixta, Schenck,
2 (var. of the former) ; (18) A. varians, Rossi, 2, not rare; (19) A. atriceps,
K. 94; (20) A. nigrownea, K. 9; (21) A. Trimmerana, K. 9; (22) A.
Smithella, K. 9 ¢, ab. ; (23) A. fulvicrus, K. 9 ¢, very ab. ; (24) A. fasciata, —
Wesm. 2 ¢; (25) A. albicrus, K. ? ¢; (26) A. parvula, K. 2 Sg, very ab. ;
(27) A. argentata, Sm. (gracilis, Schenck), ¢, ab. ; (28) A. dorsata, K.? ¢, ab. ;
(29) A. fulvescens, Sm. 2 ; (80) A. connectens, K. 2; (31) A. convexiuscula,
K. ?, all Andrene ? c.p. and s., the g s.; (382) Halictus rubicundus, Chr. 9 ;
(33) H. zonulus, Sm. 9; (34) H. sexnotatus, K. 9, ab. ; (35) H. sexsignatus,
Schenck, ?, ab. (as late as Oct. 13) ; (36) H. maculatus, Sm. 9 ; (37) H. albipes, —
F. ?, ab. ; (38) H. cylindricus, F. ?, ab. ; (89) H. flavipes, F. 9; (40) H.
morio, F. 9 ; (41) H. leucopus, K. 2; (42) H. longulus, Sm. @ ; (43) H. niti- —
diusculus, K. ?, ab. ; (44) H. villosulus, K. ? ; (45) H. Incidulus, Schenck, 9 ;
(46) H. nitidus, Schenck, 9 ; (47) H. minutissimus, K. 9, all c.p. and s. ; (48)
Sphecodes gibbus, L. 9, s. ; (49) Nomada ruficornis, L. 9 ¢, very ab. ; (50) —
N. varia, Pz. 2 g, ab.; (51) N. Lathburiana, K. 9; (52) N. flavoguttata,
K. ¢; (53) N. lineola, Pz. 9; (54) N. alternata, K. 9; (55) N. succincta, Pz. —
2 go; (56) N. signata, Jur. 2 g, all s.; (57) Osmia rufa, L. g, s.; (58) O.
fusca, Chr. (bicolor, Schr.) 2, s. and c.p. ; (b) Formicide : (59) Formica con-
gerens, Nyl. §, ab. s.; (c) Tenthredinide: (60) Cephus, a small sp., ab.
B. Diptera—(a) Empide : (61) Empis livida, L., ab. ; (62) E. punctata, F., ab. ;
(63) E. opaca, F., all three s. ; (b) Sead (64) Eristalis ceneus, Scop. ; (65) 7
E. arbustorum, L. ; (66) E. nemorum, L. ; (67) E. tenax, L. (as late as Oct. 13) ; t
(68) E. pertinax, Scop. : (69) E. sepulcralis, L. ; (70) E. intricarius, L., all 8. i
and f.p., ab. ; (71) Rhingia rostrata, L. ; (72) Ascia lanceolata, Mgn., s. ; (73)
A. podagrica, F., ab., fp. ; (74) Syrphus nitidicollis, Mgn., f.p. ; (75) S. pyrastri,
L., fip.; (76) Melithreptus teniatus, Mgn., f.p.; (77) Cheilosia vernalis, —
Fallen, f.p.; (78) Ch. chloris, Mgn., f.p.; (c) Muscide: (79) Scatophaga ster-
coraria, L.; (80) Sc. merdaria, F., both species s. and f.p., ab. ; (81) Onesia®
floralis, R. D., freq. C. ee ae (82) Vanessa phates ab. ;
(83) V. Io, L., ab. ; (84) Rhodocera pr oe .3 (85) Pieris brassicae, L ; (86)
P. napi, L.; (87) Satyrus Megeera, L.; (88) ‘Hesperia alveolus, Hb., all Ss.
D. Coleoptera—(a) Nitidulide : (89) Meligethes, ab. ; (0) Buposctliles § (90) s
Anthaxia nitidula, L. ; (c) Malacodermata : (91) Malachius bipustulatus, F., f.p.; .
(d) Coccinellide : (92) Coccinella septempunctata, L., tries in vain to reach the ~
honey. E. Hemiptera ; (93) Pyrocoris aptera, L., s., ab. See also No. 590, MII.
for a further list of visitors in Low Germany ; and No. 609 for a list of Alpine
visitors, /

pg Recap a

Altogether I have observed upon the Dandelion—

Apide “Lepidoptera Diptera. Other Insects {

In Low Germany... 67 i 7 25 ie

—
lo

| On the Alps ... ide 25 | 35 26

—$$ $$

parrut)] THE MECHANISMS OF FLOWERS. 361

In each 100 visitors there are therefore—

Apide \sgediigkings Diptera. {Other Insects

—

rt ne corres
:

| In Low Germany _... 58°2 6°1 21°7 13 9

On the Alps ... ii 25°5 35°7 26 °5 12°2

icine

Se ae Se
i
a

au

275. SONCHUS OLERACEUS, L. :—

nT > ag, i
SP, a oie >

Visitors: A. Diptera—Syrphide: (1) Syrphus balteatus, Deg., fp. ; (2)
§. arcuatus, Fall. ; (3) Eristalis arbustorum, L. ; all three species s. and f.p.
_ B. Lepidoptera—Rhopalocera : (4) Pieris brassice, L., s.

|

276. SoNCHUS ARVENSIS, L. :—

Visitors : A. Hymenoptera—Apide : (1) Apis mellifica, L. §, s. and c.p., very
_ ab., it dusts itself over and over with pollen ; (2) Bombussp., s. ; (3) Panurgus
_ calearatus, Scop. 2? gd, s. and cp., very ab.; (4) P. Banksianus, K. ? ¢,
searcer ; (5) Halictus quadricinctus, F. ?, cp. ; (6) H. rubicundus, Chr. ?,

c.p. and s. ; (7) H. flavipes, F. 2, c.p.; (8) H. lugubris, K. ¢,s.; (9) Nomada
varia, Pz. 2,8. ; (10) Megachile centuncularis, L. 9, ¢.p. and s.; (11) Osmia
‘spinulosa, K. 2, ¢.p. ands. (Thur.) B. Diptera—(a) Syrphide : (12) Eristalis
tenax, L.; (13) E. arbustorum, L., both species s, and f.p., ab. ; (14) Cheilosia
&8p., fp. ; (b) Conopide : (15) Sicus ferrugineus, L., s. C. Lepidoptera—Rhopa-
locera : (16) Hesperia sp.,s. D. Coleoptera—(a) Curculionidae : (17) Spermo-
_ phagus cardui, Schh., very numerous ; (b) Malacodermata: (18) Malachius
Di sp.; f.p. 1 .

___} The following additional Composites are discussed in my Alpenblumen (609) :—
_ Achillea atrata, L., A. macrophylla, 1.., A. moschata, Wlf., A. nana, L., Adeno-
pyle albifrons, Rehb., A. alpina, Bl. et Fing., A. hybrida, D.C., Aronicum Clusii,
All., Aster alpinus, L., Bellidiastrum Michelii, Cass., Carduus Personata, Jacq.,
— Centaurea Mureti, Jord., C. nervosa, Willd., C. phrygia, L., Chrysanthemum alpinum,
_ L., C. coronopifolium, Vill., Cnicus heterophyllus, All., C. spinosissimus, Scop.,
_ Crepis aurea, Cass., Gnaphalium dioicum, L., G. Leontopodiwm, Scop., Hieraciwm
| albidum, L., H. aurantiacum, L., H. Auricula, L., H. glanduliferum, Vill., H.
| staticifolium, Vill., H. villosum, L., Hypocheris uniflora, .Vill., Lactuca perennis,
__L., Lappa major, Gartn., Mulgedium alpinum, Cass., Saussurea alpina, D.C.,
_ Senecio abrotanifolius, L., S. carniolicus, Willd., S. cordatus, Koch., S. Doronicum,
L., S. nebrodensis, L.

In addition to these, the following are treated in my Weitere Beobachtungen, pt.
ul. :—Bidens cernua, L., Inula britannica, L., I. Heleniuwm, L., 1. hirta, L., Petasites
officinalis, Ménch., Prenanthes muralis, L., P. purpurea, L., Senecio silvaticus, L.,
S. viscosus, L., Silybum Marianum, L., Sonchus asper, Vill.

Besides all these, Hildebrand in his Geschlechtsverhdltnisse bei den Compositen (357)

_ treats of the following :—Agathea, <Arctotis, Cacalia, Calendula, Cryptostemma,
_ Dahlia, Doronicum, Gazania, Jurinea alata, Liatris, Melampodium divaricatum,
_ Senecio populifolius. Silphium doronicifolium, Telekia, Vernonia, Xeranthemum, -

~€

Se ee

>

362 THE FERTILISATION OF FLOWERS. [PART III,

REVIEW OF COMPOSIT#.

A review of the Composites which I have more particularly
described shows that the. special characters of the family for the
most part secure such abundant insect-visits that the power of
self-fertilisation may be dispensed with ; and to a great extent it
has been dispensed with, though in this respect all gradations are
found between such conspicuous and abundantly-visited forms as
Taraxacum, Cnicus arvensis, and Achillea, and those which, like
Senecio vulgaris, are only visited exceptionally, and regularly

fertilise themselves.
Species in this last soutien explain how it could be of

advantage to one offshoot of the Senecionidz with still less

éoueeaioas flowers, viz. the Artemisiaceze, to adapt themselves

for wind-fertilisation, and to renounce entirely the insect-visits

whose occurrence had become so rare. Delpino has shown in a
masterly way in his work on the Artemisiacez, the small steps by
which this change took place.

A comparison of species in the same genus (e.g. Senecio JSacobeea
and S. vulgaris, Cardwus crispus and C. acanthoides, Cnicus arvensis,
C. palustris, and C. nutans), or of closely allied genera, shows clearly

that in the Compositz, as in other cases, the abundance of insect- —

visitors increases with the conspicuousness of the flowers, and the
variety of insects with the accessibility of the honey. It is only
in a few forms with solitary, inconspicuous capitula, devoid of
ligulate marginal florets (Gnaphalium uliginosum, Senecio vulgaris),
that insect-visits, and consequently cross-fertilisation, are rare.

If we compare in regard to the variety of insect-visitors, not

isolated genera (Salix, Scabiosa, Jasione), but whole families, with

the Composite, we find that the Umbelliferee alone rank with —

them; indeed they in some cases surpass in this respect the most
favoured Composites. But corresponding to the different con-
ditions of the honey in these two orders, there is this remarkable

distinction, that the Umbellifere: are visited and fertilised mainly —

by those insects which are least specialised for floral nutriment,
while most Composite are to a greater extent. or even principally,
visited by the most specialised orders of insects. To make this
distinction quite evident, I have arranged in the following table
ten of the commonest forms of each order with their visitors,
choosing plants with whose insect-visitors I was best acquainted.

Od es a ee,

PART III. ] THE MECHANISMS OF FLOWERS. 363

INsECT- VISITORS OF CoMMON COMPOSITES AND UMBELLIFERS.

; 5 Percentages.
co)

fr ; oi : *

Ss | § B ] & 3

3 2 : DR 2 net 4

i=) =| i= - ro]

A ic} & Meo So s =

aS og 8 a i s 8 5 he

es a | = a] 4 ae | = B |i

° 8 f=") ) we) o a — =

a 4 a ° 4 4 A °

ComposiT&

| Taraxacum officinale eis «. | 98 7 58 21 7 75 | 62:5 | 22°6 74
Cirsium arvense ... ae oa 88 7 82 24 25 79 | 8674 | 27°38 | 28°4
Achillea Millefolium Rae 87 6 80 21 80 || 69 34°5 | 24°1 | 34d
Chrysanthemum ideaithacoties 72 5 12 28 27 || 69 16°6 | 38°9 | 37°5

Centaurea Jacea ... ee aul | ae 13 28 6 1 27 58°7 | 12°5 2
Cardius acanthoides ai wists OM 4 82 3 5 |, 91 72°7 6°8 | 11:3
Senecio Jacobuwa ... aie bel 40 8 16 18 3 75 | 40 | 45 75
Picris hieracioides ... eae ate 29 8 16 9 1 10°38 | 65°2 31 3°4
Tanacetum vulgare ane see | OF 5 7 7 8 || 185 | 25°9 | 25°9 | 29°6
Eupatorium cannabinum... .. | 18 9 2 6 } 1 || 50 111 | 833 | 5°5

UMBELLIFER.

Heracleum Sphondylium... —... | 118 0 13 49 56 0 lle | 415 | 4774
Agopodium Podagraria ... «xd, 1 08 0 15 84 55 6 14°4 | 826] 52:9
Anthriseus silvestris sae so | 28 0 5 26 42 0 68 | 35°6 | 57°5
Daucus Carota ue wee ee |G 2 8 19 32 3°38 | 1381 | 811) 525
Carum Carni sis tie wnat, 20D 1 9 21 24 1°8 | 16°4 | 882] 48°6
Anethum graveolens 2 nea 46 0 6 15 25 0 13 82°6 | 54°3
Sium latifolium ... oa ae 82 0 0 20 12 0 0 625 | 87°56
Angelica silvestris .. eas seo | 80 1 2 11 16 33 66 | 866 | 53°83
Cherophyllum temulum ... owe | 28 0 1 10 12 0 4°38 | 48:5 | 62°2
Pimpinella Saxifraga whe ae 1228 0 8 8 12 0 13 84°8 | 52°2

This table shows clearly :—

1. That many Umbelliferz are not visited at all by Lepidoptera,
and the others to a small extent only; while the Composites are
regularly visited by Lepidoptera, and in some cases (Lupatorium)
depend mainly upon them. .Of the ten Umbelliferz, three only

are shown to be visited by Lepidoptera, which in no case exceed

3°5 per cent. of the insect-visitors; and I can testify that even
these few species are not regular but only exceptional guests. Of
the ten Composite, all are visited by some Lepidoptera (7 to 50
per cent.), and these are among their regular visitors. Hupatoriwm
I have found to be visited ‘by very numerous Lepidopters be-
longing to nine species.

2. Bees are among the visitors of almost all Umbelliferze ; but
they only amount to a small number of species (under 16 per cent.),
and to a still smaller percentage of individuals. They belong
almost entirely to those genera which are either the least or the
most adapted for obtaining honey (cf. p. 287). On the other
hand, the flowers of Composite, richer in honey and in pollen,
attract far more species of bees of the most various genera; so
that in these ten Composite of my table, bees form 11 to 72 per

364 THE FERTILISATION OF FLOWERS. [PART IIL. |

cent. of the whole number of species, and a still larger proportion
of the individual visitors, and owing to their diligence they are of
even greater importance in the work of fertilisation than this
percentage directly indicates.

3. Diptera, and short-lipped insects of other orders (especially -
Hymenoptera and Coleoptera), form a considerable percentaze of
the species of visitors in both families, but more so in the case of
Umbelliferee than of Composite. In the ten Composites the
number of Dipterous visitors varies from 6 to 45, in the ten Um-
bellifers from 31 to 62, per cent. Similarly, the percentage of
short-lipped visitors of other orders varies in these Composites
from 2 to 37, in the Umbellifers from 37 to 57, per cent. Diptera
and short-lipped insects of other orders taken together make in
the Composite 14 to 76, in the Umbelliferze 83 to 100 per cent.

In the face of this evidence, it is unnecessary to discuss
Delpino’s statement (178, 180) that the Composite are fertilised
almost exclusively by bees.

Orv. STYLIDIE LZ.

The plants of this order, according to Delpino (who examined —
only dried specimens), are markedly proterandrous and are evidently
fertilised by insects (178).

Orv. GOODENOVIEZ.

In the plants of this order the style ends in a collecting-cup,
which receives the pollen while still in the bud and then closes up, —
leaving only a narrow opening for the most part covered by hairs.
At the same time it bends down to stand in the mouth of the
almost horizontal flower, so that insect-visitors come in contact
with the hairs and dust themselves with a little of the powdery
pollen. As the stigmatic lobes grow up in the cup they keep forcing
fresh pollen into the narrow slit, and finally emerge by it themselves,
and then receive the pollen of younger flowers from insect-visitors —
(178, 360, 550). The structure of the stigma in the different —
genera (Goodenia, Scwvola, Velleia, Calogyne, Dampiera, Lesche-
naultia) is very variable, as Bentham shows in an interesting
paper (84). In Leschenaultia formosa, R. Br., the insect’s proboscis
comes in contact with the lower lip of the pollen-cup, thus opening —
it and dusting itself with pollen; in the next flower it places this —

pollen on the stigmatic surface which. lies outside. the cart :
(Darwin, No. 162),

a EY sien

varriitj] THE MECHANISMS OF FLOWERS. 365

Orv. CAMPANULACE ZZ.

Tribe Lobeliew.

Siphocampylus bicolor, G. Don.—The five anthers cohere to form
a hollow cylinder which becomes filled with pollen, and whose
anterior opening bends downwards into the mouth of the flower.
In the first stage the style, with its two stigmatic lobes closely
applied to one another, extends to the base of the anther-cylinder,
but gradually grows up through it, brushing the pollen before it

out of the cylinder by means of a ring of hairs placed behind the
_ stigmas. When the stigmas issue at the anterior opening of the

cylinder the two lobes separate and expose their papillar surfaces

_ to contact with insect-visitors in the upper part of the mouth of
_ the flower. So insects come in contact in younger flowers with
_ pollen at the anterior opening of the anther-cylinder, and in older
_ flowers with the stigmas, and regularly fertilise older flowers with
_ the pollen of younger (Hildebrand, Nos. 346 and 351).

Other species of Siphocampylus are believed by Delpino to be

fertilised by honey-sucking birds (178).

Isotoma axillaris, R. Br.—The mechanism is for the most part
similar, but there is a lancet-like appendage to each of the lower
anthers which extends downwards into the upper part of the
flower, and which causes shedding of the pollen when touched by

an insect (Hildebrand, No. 356).

Lobelia Erinus, L. (2) (Common Blue Lobelia).—The flower,

" which has been thoroughly described by Mr. T. H. Farrer, agrees
in all essential points with Siphocampylus bicolor, and is visited by
_ bees (240). |

Delpino saw Lobelia Erinus visited by Halictus (178). Hilde-
brand observed in the same species that the style is frequently not
able to force its way through the closed end of the anther-tube,
and that in such a case the stigmatic lobes unfold within the
anther-tube and are self-fertilised (360). |

Lobelia syphilitica, L., is abundantly visited by Bombus ttalicus

and B. terrestris (Delpino, 172, 176).

Lobelia fulgens, Willd.—Delpino suggested that this plant is
fertilised by humming-birds (172, 176), and Trelease afterwards saw
the flowers visited by the Ruby-throated Humming-bird (727, 751).

Heterotoma ditfers from Siphocampylus in having all the lobes of
the corolla bent«downwards, in the lower portion of the corolla: being

366 THE FERTILISATION OF FLOWERS. [PART IT.

produced into a long spur, and in the stamens only cohering for a
short distance below the anthers (360).

Tribe Cyphiee.

The stigma is crowned with a tuft of hairs and only reaches to
the base of the anthers, which are closely aggregated together
and contain the pollen in a single large mass between them. The
anthers stand on the lower side of the horizontal flowers, and
separate when the insect-visitor enters, so that the ventral surface —
of the insect comes in contact with the pollen and with the stigma.
Bees are probably the fertilising agents (178, 360).

Tribe Campanulee.

The structure of the flower in our species of Campanula has
been admirably described and explained by Sprengel. Delpino
makes general remarks upon this ‘and several other genera of
Campannulec, and names Cetonie as the fertilisers of Campanula
Medium, and Apis and Halictus as fertilisers of the other species of
Campanula ; and he gives in addition to his own observations a full
account of the erroneous views of Wahlbom, Cassini, Du Petit-
Thouars, Alph. de Candolle, Treviranus, Gartner, and Vaucher
concerning the fertilisation of Campanula (178, 360). :

In Campanula the honey is secreted and borne by a yellow,
fleshy, epigynous disk (m), surrounding the base of the style;
it is covered by the bases of the five stamens which expand in
triangular lamine (sd). Hairs close over the interspaces between
the bases of the stamens, and protect the honey rather from
unbidden guests than, as Sprengel supposes, from rain, which —
is sudiciently guarded against in most species by the pendulows t
position of the flowers.

In the bud, and often for a time in the open flower, the three
stigmas lie closely applied together, forming a cylinder whose outer
surface is thickly covered with long, erect hairs; in the bud the
anthers are placed close around this cylindrical brush (grb), so
that they form a hollow cylinder inclosing the style, and as -they
dehisce introrsely they shed their pollen upon the hairs of the —
brush. When this has taken place the stamens wither and with- —
draw into the base of the flower. Now the flower opens and dis- —
plays in the first stage of its development a cylindrical brush ~
standing in the centre and covered thickly all round with pollen,

PART III. | THE MECHANISMS OF FLOWERS. 367

which is rubbed off by the hairy bodies of insect-visitors until it is
_ exhausted ; meanwhile the hairs of the brush gradually shrivel. - In
: the pnd. stage the three divisions of the style separate and curve
_ backwards, exposing their inner surfaces covered with stigmatic
: - papillze (st) to be touched by insect-visitors. In case of sufficient
insect-visits, cross-fertilisation, and, as in every case of marked
_ proterandzy, fertilisation of older flowers with the pollen of younger,
_ is inevitable.

+ In Campanula, when insects have not visited the flower to
- sufficient extent, the stigmas usually bend further backwards

Fic. 118.—Campanula pusilla, L.

ie hi eal

A.—Section of young bud.

B.—Essential organs of a bud about to open.

C.— Essential organs of a flower, in first (male) stage.

D.—Ditto, in second (female) stage. (x 4.

sd, expanded bases of the filaments, fringed with hairs, which guard the honey ; grb, brush upon
ete sty le ; grb’, ditto, after its hairs have shrivelled up.

oh NG

until self-fertilisation is effected. The papillose end of the stigma
either comes in immediate contact with the pollen still adhering
to the upper end of the styles, or pollen falls of itself upon the
‘papillee of the recurved portion. It is clear from its wide, bell-
shaped corolla, that Campanula is specially adapted for humble-
bees, but the flowers in the various species are visited by many
other insects, chiefly bees. Many insects find shelter from rain
and also spend the night within the flowers ; and some confine their
visits mainly (Cilissa hemorrhoidalis, species of Chelostoma) or
almost exclusively (Halictoides dentiventris) to species of Campanula.

368 THE FERTILISATION OF FLOWERS. [PART IIT,

277. CAMPANULA ROTUNDIFOLIA, L. :—

Visitors : A. Hymenoptera—Apide: (1) Apis mellifica, L.§, 8.5; (2)
Bombus pratorum, L. $, s.; (3) B. lapidarius, L. %, cp. ; (4) Cilissa heemar-
rhoidalis, F. 9 ¢, s. and cp. ; (5) Andrena Coitana, K. g (Sld.), ab. ; (6)
A. Gwynana, K. ¢; (7) Halictus Smeathmanellus, K. ¢; (8) Halictoides
dentiventris, Nyl. ¢ 2, the g abundant, sometimes passing the night within
the flowers ; (9) Chelostoma nigricorne, Nyl. 9 g,s. and cp. ; (10) Ch. Cam-
panularum, L., do. B. Diptera—(a) Bombylide : (11) Systeechus sulfureus,
Mik.,s. (Sld.) ; (b) Empide : (12) Rhamphomyia plumipes, Fallen, ab. C. Lepi-
doptera—(13) Ino statices, L.,s. (Sld.). D. Coleoptera— (a) Staphylinide : (14)
Anthobium ; (b) Curculionide : (15) Gymnetron Campanula, L. ; (16) Otio-
rhynchus ovatus. On the Alps also this species is chiefly visited by bees
(609). See also No. 590, Ill.

278. CAMPANULA TRACHELIUM, L.:—

Visitors: A. Hymenoptera—Apide : (1) Apis mellifica, L., 9, s., ab. ; (2)
Cilissa hemarrhoidalis, F. 9 ¢, s. and c.p., the ¢ very ab., sometimes three in
one flower ; (3) Andrena Coitana, K. 2 ¢,here also the ¢ is much the more
abundant ; (4) A. Gwynana, K. 2 g, ab.; (5) A. fulvicrus, K. ¢, taking
shelter during rain; (6) Halictus cylindricus, F. 9, ¢.p.; (7) Halictoides
dentiventris, Nyl. 9 ¢, g very ab. ; (8) Prosopis hyalinata, Sm. ? ¢, ab. ;
(9) Chelostoma Campanularum, L. B. Diptera—Syrphide: (10) Chryso-
chlamys ruficornis, F. (Lippstadt, Sld.), fp. ; (11) Syrphus balteatus, Deg.,
fp. C. Coleoptera—(a) Nitidulide : (12) Meligethes, very ab. ; (b) Crypto-—
phagide : (13) Antherophagus, sp. See also No. 590, 111.

279. CAMPANULA RAPUNCULOIDES, L. :—

Visitors: A. Hymenoptera—Apide: (1) Apis mellifica, L. §, s.; (2)
Bombus lapidarius, L. $, s.and¢.p.; (8) Cilissa hemarrhoidalis, F. 2 ¢; “) 4
Andrena Gwynana, K. 3 ?; (5) Halictus maculatus, Sm. ¢; (6) H. albipes,
K. 9; (7) Chelostoma nigricorne, Nyl. ¢ 2 ; (8) Ch. Campanularum, K. ¢ 2;
(9) Prosopis hyalinata, Sm. ¢ ?, the last three ab. B. Diptera—Syrphide :
(10) Rhingia rostrata, L., s., it issues from the flower with its back covere ed
with pollen. See also No. so: III.

280. CAMPANULA BONONIENSIS, L. (Wandersleber Gleiche in —
Thuringia).

Visitors: A. Hymenoptera—Apide : (1) Chelostoma florisomne, i 2
freq. ; (2) Ch. nigricorne, Nyl. 2 ¢; (3) Ch. Campanularum, K. 9 ¢, ab.
(4) Halictus flavipes, F. 9. B. Coleoptera—Nétidulide : (5) Meligethes,
freq. See also No. 590, m1. :

281. CAMPANULA PATULA, Le:

Bh ose Hymenoptera—Apide : (1) Andrena Gwynana, K. 9, s. and
; (2) Chelostoma nigricorne, Nyl. ¢ 9,5. and ep. See also No. 590, TT. |

THE MECHANISMS OF FLOWERS. 369

282. CAMPANULA PERSICIFOLIA, L, :—

Visitors: A. Hymenoptera—Apide: (1) Prosopis hyalinata, Sm. ? ¢.
B. Orthoptera—(2) Forficula auricularia, L., hiding in the flowers. See also
No. 590, Il.

Campanula canescens, Wall., and C. colorata, Wall. two East
‘Indian species, have cleistogamic flowers (531).
_ Specularia perfoliata, Dec.—The cleistogamic flowers, which
were known to Linnzus, are described by H. von Mohl (531).
Trachelium.—When the flower expands the pollen adheres to
the hairs of the stigma, which in the bud grows up between the
thers; these hairs then wither and readily give up the pollen to
a an insect-visitor. Afterwards the stigma unfolds and its papille
“develop. Delpino observed a cabbage-white butterfly (Pieris)
“sucking, and a bee (Halictus) collecting pollen, on the flowers
(178, 360).
—~-Phytewna—The structure of the flower of Phytewma resembles
‘on the whole that of Campanula, but the pollen, as in Composite,
‘is pushed up out of a tube by the growing style, and comes to lie
outside the flower exactly in the spot where the stigmas after-
wards unfold. The tube is formed by the long strap-shaped lobes
of the corolla which cohere for a time and afterwards separate.
- This arrangement allows of diminution in size and aggregation of the
flowers without interfering with the certainty of cross-fertilisation.
' I have found the blue Alpine species of Phytewma (P. hemi-
| sphericum, L., hwmile, Schleich., orbiculare, L., Scheuchzeri, All.,
Michelii, All., Halleri, All.) to be visited for the most part by
umerous bees and butterflies. For instance, on P. Micheli I
_ observed seventeen Apide (including twelve humble-bees), forty-
two Lepidoptera, eight Diptera, one beetle (No. 609, pp. 406-413).

a

— -Phytewma pauerflorum, L., was found by Ricca to be visited by

%

| _ humble-bees on the Alps at a height of nearly 10,000 feet (665).

283. JASIONE MONTANA, L.—The structure of the flower was
described thoroughly and accurately by Sprengel. The flower, to
a greater extent even than Phytcwma, has two advantages over
Campanula, for (1) it attracts much more numerous and more
varied insects for the sake of its honey and pollen, and (2) it
allows the larger visitors to fertilise a greater number of stigmas
simultaneously with pollen from other flowers, while in Campanula
the fertilisation of each flower requires a separate visit.

1 The following additional species of Campanula are discussed in my Alpenblumen :
, C. pusilla, Heenk., CO. Schewchzeri, Vill., C. barbata, L., and C. thyrsoidea, L.

BB

370 THE FERTILISATION OF FLOWERS. [partir

The visits of a more miscellaneous lot of insects are attaine
by the honey being very easily accessible, though protected frox
rain. It is secreted, as in Campanula, by the upper surface of th
ovary, where it lies fully exposed and surrounded by the flat lim
of the calyx. The corolla is cleft to its base into narrow linea
lobes, and permits the most short-lipped insects to have free acces:
to the honey; the stamens, by cohering at the base of the anther

Fic. 119.—Phyteuma Michelii, L.
A.—Young bud, after removal “f the corolla and of one stamen.
B.— Flower, in first (male) stag
C.—Ditto, in second (female) yeas. (x 7.)
(Franzenshoh, July 20, 1874).

to form a ring round the style, shelter the honey from rain, thoug!
not from insects, which can insert their heads or tongues betwee!
the filaments which are quite thin and widely separate to their base:
Drops of rain are excluded from the base of the flower partly b
the shrivelled anthers which point obliquely upwards, and
by the filaments. That the larger insects fertilise numerou
flowers at each visit with pollen from other flowers is effected by
three other characters conjointly. In the first place, the flowers:

PART 111. | THE MECHANISMS OF FLOWERS. 371

a e so small and so closely aggregated that the larger insects come
In contact with many at once in their visits; secondly, the styles
elongate until they overtop the lobes of the corolla; and thirdly,
here as in Campanula the flowers are markedly proterandrous,
_ the style bearing first a cylindrical brush covered with pollen
(Fig. 120, 3), and afterwards, when both pollen and hairs have

Sat, a ++
- —_ “a

EE ERM TES 1

Fic. 120.—Jasione montana, L.

1.—Essential organs, from a young bud. The still closed anthers have been separated slightly,”
to show the style with its brush lying between them.
__ 2.—Essential organs, of am older bud. The anthers have shed their pollen upon the styie, and
_have shrivelled up into narrow lobes which remain coherent at their base.
_ 8,—Flower, in first (male) stage.
_ 4,—Ditto, in second (female) stage, after removal of the calyx and corolla.

flowers is fully compensated for by the union of a large number in
acapitulum. Sprengel states the number of florets in a capitulum
to be about seventy; in the specimens that I have examined,
I have found the number to be considerably over 100, even
reaching 180.

> BB 2

disappeared, displaying a two-lobed stigma. The small size of the

372 THE FERTILISATION OF FLOWERS. [rar m1

Jasione is rendered especially conspicuous by growing chiefly;
on dry, sandy soil, where it is usually one of the most prominer ni
flowers, and where many bees and sand-wasps which visit it havi
their nests. ‘

On two such spots, behind the Tannenbaum at Lippotade|
on the Lippstadt Heath, I found the following insects visiting h
flowers in July and August, 1868 and 1869 :—

A. Hymenoptera—(a) Apide: (1) Bombus hortorum, L. ? §, s.; ¢
B. silvarum, L. $,s. ; (3) B. rupestris, L. ¢,s. ; (4) Sarapoda bimaculata, P
2 &, very ab., s. and c.p.; (5) Dasypoda hirtipes, F. ¢, freq. ; (6)
leporina, Pz. 2 ; (7) Rhophites halictula, Nyl. 9,8. ; (8) Andrena Hattorfian:
F. ¢, once; (9) A. dorsata, K. 2 g, ab. ; (10) A. pubescens, K. ¢ (= fu
cipes, K.), 8. ; (11) A. fulvago, Chr. 9; (12) A. helvola, L. 9; (13) A. fulvi
crus, K. ? ;-(14) A. argentata, Sm. g; (15) A. pilipes, F. ¢; (16) A. Coite
K. ¢ 2; (17) Colletes marginata, L. ¢; (18) Halictus fasciatus, Nyl. 9 ; fa
H. flavipes, F. ¢; (20) H. leucozonius, Schr. 9 ; (21) H. albipes, F. 2; (22
H. cylindricus, F. 2 ¢ ; (28) H. villosulus, K. ? ; (24) H. lucidulus, Schenck, 9
(25) Sphecodes gibbus, L. ? (var. rafescens, Fourc.) ; in the last three gener:
the ¢ s., the 2 s. and cp. ; (26) Ceratina czerulea, Vill. 2 ¢, freq., s. and ¢.p.
(27)° Nomada ruficornis, L. 2 ¢; (28) N. Roberjeotiana, Pz. ? ¢; (29) }
nigrita, Schenck, ¢; (30) N. lineola, Pz. $; (31) N. Jacobee, Pz. ; (82) N
varia, Pz. ; (33) N. Fabriciana, L. ; (34) Ceelioxys quadridentata, L. 2 ¢, ab.
(35) C. conoidea, Ill. (punctata, Lep. 9) ; (86) C. simplex, Nyl. 9 ¢, 8.3 (37
Epeolus variegatus, L. ¢ 2, freq. ; the cuckoo-bees of course only suck
(38) Anthidium strigatum, Latr. ¢; (39) Diphysis serratule, Pz. 2 ; (40)
gachile maritima, K. ¢; (41) M. argentata, F. ¢ 9, 8 and cp. ab.; (42
Chelostoma campanularum, L. ? ; (48) Prosopis variegata, F. 2 ¢, very ab.
(44) P. dilatata, K. ¢; (45) P. communis, Nyl. 9 ¢, ab. ; (46) P. hyalinata
Sm. 9, ab. ; (47) P. pictipes, Nyl. 9, scarce; (b) Sphegide, s.; (48) Ammo
phila sabniona, L. g, freq. ; (49) Psammophila affinis, K. ¢ 9, very freq.
(50) Pompilus rufipes, L. ¢; (51) P. viaticus, L. ¢; (52) Ceropales macule
F., freq. ; (53) Cerceris arenaria, L. 9 ¢, ab. ; (54) C. labiata, F. g¢; (55
C. nasuta, Kl. ¢; (56) Mellinus sabulosus, F., freq. ; (57) Miscus campestri
Latr. 9 ; (58) Philanthus triangulum, F.; (59) Tachytes pectinipes, L. ; (6(
Lindenius albilabris, F. ; (61) Oxybelus uniglumis, L., ab. ; (62) O. bellicos
Ol. ; (63) O. mandibularis, Dhlb. ; (64) Crabro alatus, Pz. 2 ¢, very ab. ; (6
Cr. patellatus, v. d. L. 2; (66) Cr. pterotus, F. 9 ¢, both not rare; (¢) Ch
side: (67) Hedychrum lucidulum, Latr., s. B. Diptera—(a) Bombylide
(68) Exoprosopa capucina, F., not rare ; (0) sige : (69) Empis livida, L
very ab. ; (c) Syrphide : (70) Melithreptus scriptus, L. ; (71) M. nents re
(72) Volucella bombylans, L. ; (73) Helophilus reer .; (74) Eristal
tenax, L. ; (75) E. eeneus, Scop. ; (76) E. arbustorum, L. ; Ae Syritta pipien
L, ; (78) Melanostoma mellina, L.; (79) Syrphus pyrastri, L. ; (80) Eumert

sabulonum, Fall. ; (81) Pipizella, sp. ; (d) Conopide : ” Sicus ferrugineus, L.;
(83) Physocephala rufipes, F., freq. ; (84) Ph. vittata, F. ; (e) Muscide : ee )
Ocyptera brassicaria, F, ; (86) O. cylindrica, F., both very freq. ; (87) E
nomyia tesselata, F., very ab. ; (88) E. ferox, Px ; ; (89) Oliviera lateralis, Pz
ab. The Syrphide both s, and ¢.p., the others only s, C. Lepidoptera, s. ; ¢ )

ee tie!

parrut] THE MECHANISMS OF FLOWERS. 373

Rhopalocera : (90) Polyommatus Phleas, L., s., ab.; (91) P. Dorilis, Hfn., freq. ;

92) Lyceena egon, W. V. ¢ ; (93) Satyrus Janira, L., ab. ; (94) S. pamphilus, L.;

5) Hesperia thaumas, Hfn. ; (b) Sphingidee : (90) Tn statices, L.- D. Solas

optera—(a) (demeride : (97) CEdemera virescens, L. ; (b) Cerambycide : (98)

eptura livida, L., freq., lh. ; (c) Chrysomelide : (99) Cryptocephalus sericeus,
A list of ingtéeti additional visitors is given in No. 590, III.

a
¢
F
7 Jasione montana stands in the front rank of our native plants
in regard to the number and variety of its insect-visitors ; it is only
ig x atched by some Umbelliferee and Compositz, which es with it
the advantages of fully-exposed honey, and the union of numerous
. owers with freely-projecting reproductive stigmas and anthersin a
‘conspicuous inflorescence. In all such plants, cross-fertilisation is
completely insured, and accordingly the possibility of self-fertilisa-
tion has been lost.

Orv, VACCINIACE ZL.

284, Vaccinium Myrrtiuvus, L.; 285, V. uLiainosum, L.— Both
species are slightly proterandrous, and resemble Hrica tetralix in
their mode of fertilisation.

_ In PV. Myrtilius, according to Sprengel, honey is secreted and
borne by the white annular ridge or disk which rests upon the
ovary and surrounds the style ; I have never found this disk moist,
even when the wide part of the corolla is quite wet with honey ;
it is moreover not so smooth as honey-glands usually are. On the
other hand, I have very frequently found in both species a drop of
| per at the outer side of the base of each stamen; and as the
base of the corolla immediately above its insertion is all round
} Bach thicker and fleshier than the upper portion, I at first did not
4 d oubt that it secreted the honey. But I have since convinced
nyself that Sprengel was right, and that the drops of honey secreted
by the epigynous disk pass between the filaments to the wall of
the corolla.

So far, both species agree with one another : but in other respects
each has certain advantages over the other. V. Myrtillus secretes
_ More honey, which is lodged in a much more globular corolla; the
opening is narrowed so that only insects with a proboscis long
enough to reach from the exterior to the base of the corolla can
obtain the honey. On the other hand, V. uliginoswm forms taller
bushes bearing much more numerous flowers, which are red on
| the side turned towards the light and therefore much more con-
- Spicuous while the mouth of the corolla is 3 mm. wide, permitting

374 THE FERTILISATION OF FLOWERS. [parr nr

the smaller insects to insert their heads or the whole forepart o
the body. V. Myrtillus has thus adapted itself exclusively for the
long-proboscised bees (hive-bees, humble-bees), which are con:
spicuous for their skill and diligence; they know that within
the inconspicuous corolla they will find a rich store of honey, and
seek it so assiduously that hundreds of the flowers are visited anc
fertilised by a single insect. V. uliginosum has adapted itself by
its more conspicuous flowers and more accessible honey to much
more various insects; it is much less frequently and less
assiduously visited by the long-tongued bees than V. Myrtillus,
for the greater part of the honey is carried away by the short:
lipped insects.

Fig, 121.

1.—Flower of Vacciniwm Myrtillus, slightiy magnified, from the side.
2,—Flower of V. wliginoswm, after removal of half the corolla (x 7).

The difference in size of the mouths of the corolla causes als
another difference, illustrated in Fig. 121. In V. Myrtillus th
stigma projects a little beyond the corolla, and, as every insec
visitor inserts only its proboscis into the flower, the stigma is certail
to be touched by the insect’s head before the latter receives th
pollen shed upon it. In V. uliginoswm, if the stigma occupied th
same position, the smaller bees (Halictus and small Andrene
Nomad) might enter the flower without ever touching the stigma
whereas, placed as it is, immediately within the entrance, it must
be touched by even the smallest insects entering the flower. If
have verified by direct observation this marked distinction between
the insect-visitors of the two species, | |

anriu.] | THE MECHANISMS OF FLOWERS. 375°

284. V. Myrrituus, L. :—

_ Visitors: (1) Apis mellifica, L. §, very ab., s.; (2) Bombusagrorum, F. ?,
; (3) B. lapidarius, L. 9; (4) B. terete, L. 9; (5) B. Scrimshiranus,
. 2 9, all sucking only. They hung, head downwards, from the corolla. All
he humble-bees that I observed were females, for the workers scarcely occur
when the plant is in flower (middle of April to beginning of May). (6) An-
lrena nigrownea, K. ¢, 1 once found this species, whose proboscis is only 34
mm. long, endeavouring vainly to reach the honey.

:
.
ah
ae
| ig
ty

___—«-.285._‘V. uLicinosuM, L.—I found all the following insects upon
- this plant on one sunny afternoon (May 19, 1870) :—

A. Hymenoptera—(a) Apide: (1) Apis mellifica, L. $, ab. ; (2) Bombus
terrestris, L. 9, freq. ; (3) B. hortorum, L. § ; (4) B. pratorum, L. ? ; (5)
_ B. agrorum, F. 9; (6) B. confusus, Schenck, ?; (7) B. (Apathus) vestalis,
Foure. ?, freq.; (8) B. (A.) campestris, Pz. 2; (9) B. silvarum, L. 9; (10)
Andrena nigrownea, K. 2 ¢; (11) A. pilipes, F. ¢; (12) A. fulva, Schrank,
@; (18) A. Gwynana, K. 9; (14) A. atriceps, K. ¢; (15) Halictus rubi-
eundus, Chr. 9; (16) H. flavipes, F. 9; (17) H. sexnotatus, K. 2; (18) H.
eylindricus, F. 2 ; (19) H. sexstrigatus, Schenck, ?; (20) Colletes cunicularia,
L. 2; (21) Nomada ruficornis, L. 9 ; (22) N. ferruginata, K. 2; (23) Osmia
rufa, L. 9, all sucking ; (b) Vespidw: (24) Vespa rufa, L.,s. B. Diptera—
Syrphide : (25) Eristalis arbustorum, L., very ab. ; (26) E. horticola, Mgn.,
arce ; (27) E. intricarius, L., do. ; (28) Rhingia rostrata, L., not unfreq.; all
four sucking. C. Lepidoptera—Rhopalocera : (29) Lyczna argiolus, L. ; (30)
Theela rubi, L., both sucking. See also No. 590, 111.

—s«- Vaccinium oxycoceus, L.—The structure of the flower was care-
fully described by Sprengel. It is adapted for bees, but is very
ingly visited. The flowers last a very long time, according to
Sprengel, eighteen days, and Sprengel was probably justified in
i onsidering this fact to be explained by the scanty insect-visits
je (590, III. ).

Vaceinium Vitis-idea, L.—The mouth of the corolla is still
vider than in V. wliginoswm, and the flower is more nearly erect.
The plant is fertilised by hive-bees and humble-bees (589, 609).

ia

.
Da.

&.: Orv. ERICACEZ.

Tribe Arbutew.

Arctostaphylos Uva-ursi, Spr. (Arbutus uva-ursi, L.).—The
flower resembles that of Hrica tetralix in structure, and is likewise
ees chiefly by humble-bees (609).

a

376 . THE FERTILISATION OF FLOWERS. [PART IIT.

Tribe Andromedee.

Epigea is tetramorphic, possessing four kinds of flowers, which
differ partly in the length of the style, partly in the conan of
the stigma and anthers (ase Gray, No. 285). a

Tribe Fricec.

286. ERICA TETRALIX, L.—The pendulous, urceolate flower i
7 mm. long, 4 mm. wide in the middle, and 2 mm. wide at the

Fr@. 122.—Erica tetralix, L.

Flower, after removal of half the calyx and corolla.
a, sepal; b, corolla; c, its recurved limb ; d, anthers, partly displaced ; e, their orifices; /, thei
appendages ; 9: nectaries ; h, ovary; i, style ; k, stigma.

mouth. The base of the ovary is surrounded by a dark, glandular —
ring which secretes honey. The style (2) stands in the axis of the —
flower, extending to the mouth of the corolla; it bears at the —
end a blackish, moist, sticky stigma (%), which protrudes slightly _
from the mouth of the flower, so that an insect, hanging beneath

the flower and thrusting its proboscis towards the honey at the —
base, must bring the forepart of its head in contact with the
stigma and be smeared with the sticky secretion. The eight
anthers lie in a circle close around the style, a little way above the —
stigma (in the inverted position of the flower); each possesses two —
long, sharp, divergent processes, which reach to the sides of the

ie ART 11. THE MECHANISMS OF FLOWERS. 377
ie sorolla. A honey-seeking insect, immediately after touching the

ia ‘stigma, brings its proboscis in contact with some of these append-

es, whereupon a shower of dry, dusty pollen is shed from, the

Picks i in the anthers on to the forepart of the insect’s head.

iP. In absence of insects, self-fertilisation may take place, as part of

_ the pollen always falls upon the edge of the stigma and remains
adherent there. Humble-bees are the chief fertilising agents.

_ This species was described by Dr. Ogle in No. 633.

_ <A, Hymenoptera—Apide: (1) Bombus senilis, Sm. 2? § ¢ (14—15) ; (2)
|B. silvarum, L. 9 $ (10—14) ; (3) B. agrorum, F. 2 § (10—15); (4) B.
Rajellus, Ill. § (10—11) ; (5) B. terrestris, L. 9 (7—9), all very ab., hanging
- to the corolla back downwards ; (6) Nomada Solidaginis, Pz. ¢, I saw this
_ insect once, apparently trying in vain to reach the honey ; (7) Apis mellifica,
_L. $,is scarcely able to reach the base of the flower legitimately, as its
_ proboscis is only 6 mm. long. It is a very abundant visitor of Erica tetralix,
but usually bites through the corolla, about midway. On Oct, 15, 1871,
_ J saw numerous honey-bees sucking normally. I omitted to observe whether
these late flowers were a little smaller than those of summer ; if so they would
exactly suit the honey-bee. B. Diptera—Syrphide: (8) Volucella bombylans,
L. (7—8), ab., s.; (9) V. plumata, L. freq., s. ; (10) V. hemarrhoidalis, Zett.,
scarce, s. C. Lepidoptera—Noctue : (11) Plusia gamma, L., s.

Erica cinerea, L., the fine-leaved heath, agrees in the structure
of its flower with JL. tetralix, according to Dr. Ogle (633).

Erica carnea, L.—This species is adapted by the colour and
size of its flowers to butterflies, which alone (e.g. V. carduz) visit
it in abundance, and effect cross-fertilisation, The sepals and
petals vary from bright pink to crimson, and the peduncles are
still more intensely coloured. The flower narrows so much towards
its mouth that the entrance is blocked by the anthers, and just
admits the thin proboscis of a butterfly, which cannot avoid touching
first the stigma and then the anthers, and so performing cross-
_ fertilisation. I have seen Bombus terrestris making great but
ineffectual efforts to insert its proboscis into the flower. The
- inverted position of the flower is somewhat inconvenient for butter-

flies, and causes them delay. We may suppose that the ancestors

of Erica carnea grew where bees were more plentiful and butter-

flies less so, and that the flowers were first adapted for bees,
as almost all other inverted, bell-shaped flowers are; and that
_ they acquired their present colour and form under the influence
| of Lepidoptera, which preponderate so conspicuously in the Alps
(609).

287. CALLUNA VULGARIS, L—The bell- -shaped corolla is 2 to

ee

378 THE FERTILISATION OF FLOWERS. [PART I

3 mm. long, and cleft into four lobes to near its base. Honey
is secreted by eight blackish glands in the base of the flowe:
alternating with the stamens, and is easily accessible to short-
lipped insects. What the plant loses in attractiveness by the s

Fig. 123.—Erica earnea, L.

A.—Bud for next year, inclosed in the calyx (x 7).
B.—Ditto, after removal of two sepals. pe
C.—Ditto, after removal of the whole calyx and half the corolla. Three of the eight stamens
have been drawn out (x 7).

D. — Pollen-tetrads from a bud, greatly magnified. (Bergiin, September 5, 1878.)
‘ E.— spelen ga in side view (x 7). The flowers usually do not hang vertically, t but only inclined

ownwards

F.—Ditto, after removal of half of the stamens and corolla.

G.—Mouth of flower.

H.—Essential organs, in their natural position ; the stamens have sprung slightly outwards on
removal of the corolla.

J Ae ; inner, outer, and lateral view.

(E, F, G, Lenz, June 1; H, J, Bergiin, June 2, 1879).

size of its corolla, it makes up by the red colour and large size
of the sepals, and by association of the flowers in long, almost
uninterrupted groups. Calluaa vulgaris is visited by at least as
many insects as Hrica tetralix, and by a greater variety owing to

parru] | THE MECHANISMS OF FLOWERS. 379

the accessible position of the honey. While in the flowers of Hrica
_ tetralix, which hang vertically, great regularity prevails in the
arrangement of the parts, the style occupying the axis of the
- flower, and the anthers forming a circle symmetrically round it with
ie heir orifices directed downwards, in the flowers of Calluna, which
are almost horizontal, insects are liable to be dusted with pollen
_ from above, as the style and stamens curve upwards and permit the
insect to reach the honey only by way of the lower half of the
flower.

_ The larger bees, such as hive-bees and humble-bees, clinging
_ with forelegs and midlegs to the outer side of the flower, weigh
- it down into the vertical position ; then, hanging on below, they
suck the honey and dust themselves with pollen, which would be
_ sprinkled on them just as well and just in the same manner if the

{
i
| =
19

Fig, 124.—Calluna vulgaris, L.

1.—O!d flower, seen from almost straight in front.
2.—Younger flower, after removal of half of the calyx and corolla.
8.—A stamen. ,
. be ones b, corolla; ¢c, appendages of anthers; d, nectaries; e, anther-orifice; f, filament
g, style.

| style and stamens were central as in JL. tetraliz. But the smaller
bees and flies thrust head or proboscis from the front into the
flower, and the upward curvature of the style and stamens causes
the insect to enter by the lower half of the flower, and so to get
dusted with pollen from above.

As the bud opens, the anthers dehisce, and their appendages,
which are set with squarrose hairs, diverge so far outwards that
they cannot fail to be touched by the proboscis of any insect-visitor,
and then, as the shock is communicated to the anthers, the pollen
is shaken out. The style, which even in the bud overtops the
_ stamens, grows very markedly after the flower opens, as the flower
itself does (cf. 1 and 2, Fig. 124). Asa rule, it attains its full length
- only after the anthers have completely shed their pollen, at which.
time also the four-lobed stigma reaches its full development; but

ae > day “Sorat E, =

aoe eaten

380 THE FERTILISATION OF FLOWERS. [parr im.

the stigma, even when the flower first opens, is capable of causing
pollen-grains to adhere to it, and is not rarely found dusted with |
pollen at that period. Thus cross-fertilisation is insured rather —
by the position of the stigma in advance of the anthers than,
as Severin Axell supposes, by proterandrous dichogamy. Self-
fertilisation does not occur. 4

A. Hymenoptera—(a) Apide: (1) Apis mellifica, L. §, very ab., sucking -
only ; (2) Bombus terrestris, L. 2 § ¢,s. (as late as Oct. 14) ; (3) Diphysis —
serratule, Pz. 2, s.; (4) Saropoda bimaculata, Pz. 9, s., with pollen of
Calluna among its collecting-hairs ; (5) Andrena fulvicrus, K. 9,s.; (6) A.
fuscipes, K. 9 ¢, s.; (7) A. dorsata, K. 9; (8) A. parvula, K. 9; (9) As
simillima, Sm. ? ¢, the last three s. and c.p.; (b) Vespide: (10) Vespa
holsatica, F. $,s. B. Diptera—Syrphidew : (11) Chrysotoxum octomaculatum,
Curt. ; (12) Melithreptus scriptus, L. ; (13) Syritta pipiens, L.; (14) Seri- —
comyia borealis, Fallen (Thuringia) ; (15) Cheilosia scutellata, Fallen; (16)
Syrphus sp., all sucking. C. Thysanoptera—(17) Numerous species of Thrips.
See also No. 590, III. ‘

Treviranus’ general assertion (742) that Ericacez fertilise them-
selves before the flower opens needs no further contradiction after
the foregoing examples.

Tribe Rhodorew.

Loiseleuria (Azalea) procumbens, L.—While the higher passes of —
the Alps are still covered with snow under the hot June sun, the —
projecting hillocks are carpeted with the red or crimson flowers of
Loiseleuria. Numerous flies, humble-bees, and Lepidoptera fly
from one tuft to another over the snow in search of honey, and as the
flowers are proterogynous, cross-fertilisation takes place regularly —
(609). | |

Kalmia.—The striking peculiarity of this genus,—viz. that —
the anthers are held fast in pouches of the corolla, until an insect-
visitor touches the elastic, outwardly-bent filaments, setting them
free and letting them return to their erect position,—was described
in the case of K. latifolia, L., (K. polifolia, Wngnham.) by Sprengel,
but was explained by him as a contrivance for self-fertilisation. —
Dr. Hasskarl seems even to suppose that this beautiful mechanism —
simply serves for spontaneous self-fertilisation ; for he says nothing
about the action of insects, and declares that the stamens release —
themselves spontaneously and effect self-fertilisation (313).

ss In Die Alpenblumen the figure of this flower has been accidentally assigned to
Empetrum nigrum (fig. 67).

a

ae

PART 111.] THE MECHANISMS OF FLOWERS. 381

_ Delpino and Hildebrand on the contrary, point out rightly that
i t he floral mechanism of Kalmia leads to cross-fertilisation in case
of insect-visits ; they both maintain, in opposition to Hasskarl, that
in K. latifolia the anthers cannot spontaneously release themselves
from their pouches. According to Delpino, the filaments are sticky
_ at the base in this species, so that they cling to an insect which
We has inserted its head into the flower, and are ‘pulled up by it when
it leaves (178, 360).

The fertilisation of K. angustifolia and K. latifolia by the hive-bee
a: and other Hymenoptera, had been observed and described two years

Fig. 125.—Loiseleuria procumbens, L.

A.—Young flower, viewed obliquely from above. The stigma is mature, the anthers still closed.
B.—Ditto, in section.

C.—A slightly older flower, in section. The stigma is mature, the anthers have dehisced.

Stles pe older flower, from above. The stigma is withered, the anthers are still covered with

Pe eaiiels, Alpenrose, June 22, 23, er

Before by Professor W. J. Beal. The insect alights on the style, and
turning round upon it, applies its proboscis successively to the
outer sides of the filaments to obtain the honey which is secreted
_ there abundantly. In doing so, it sets free the stamens with its
legs, and generally receives the charge of pollen upon its body.
If insects are excluded from the plant by means of a net, the
flowers wither and fall off without the stamens being set free.

382 THE FERTILISATION OF FLOWERS. [PART III.

Only here and there are anthers found to have escaped from their
pouches (Professor W. J. Beal, No. 41, and J. T. Rothrock, No.
676).
Rhododendron ferrugineum, L., was found by Ricca to be
proterandrous, and visited by humble-bees at a height of over
7,000 feet (665). The position of the honey causes an insect-
visitor to pass towards it by way of the upper half of the horizontal
flower, and as the stamens and style curve upwards, they come in
contact with the ventral surface of the insect. In the first stage
the style is shorter than the stamens and the stigma is immature ;
the anthers dehisce apically by means of two orifices. Afterwards
when the pollen has usually been all carried away, the style elongates
to its full length and the stigma attains its full development; but
the latter is still slightly overtopped and almost touched by the
tallest anthers, and in absence of insects it must frequently come
in contact with the pollen. Whether such self-fertilisation is effective
is unknown (6090).
Rhododendron Rhodore, Don. (Rhodora canadensis, L.)—The
floral mechanism is described by Hildebrand (367).

Tribe Pyrolee.

Pyrola uniflora, L., and P. rotundifolia, L.—These species are
probably cross-fertilised by short-lipped insects, which may be seen’
applying their mouths to the moist stigma and the orifices of the
anthers. I have directly observed cross-fertilisation performed in
this way in the case of Pyrola minor, L. (No. 609, figs. 149, 150).

Eugene Warming found flowers of different forms and sizes on
P. minor. He observed a plentiful secretion of honey in the case ©
of P. secunda (762). ae .

Orv. EPACRIDEA. |
Lpacris.—Delpino found one species to be proterogynous (178).

Orv. PLUMBAGINE &.

Some Brazilian species of Plwmbago and Statice are dimorphic,
according to Fritz Miiller (550).

Armeria, according to Treviranus, is self-fertilising. As the
anthers dehisce, the filaments curve inwards, bringing the anthers
immediately above the depressed centre of the stigma on which —
they shed their pollen (742), |

TU. | THE MECHANISMS OF FLOWERS. 383

Orv. PRIMULACEZ.

The species of Primula have been the subject of a series of
_ interesting researches since Darwin first led the way. In his paper
“On the two forms or dimorphic condition in the species of Primula,
and on their remarkable sexual relations” (No. 154), he showed
that in P. veris the stigmain the long-styled form possesses papilla
_ three times as long as those of the short-styled form ; and that the
jollen-grains of the long stamens are half as large again as those
_ of the short ; that the same holds good of P. Awricula and P. sinensis ;
j tl at these Primulas are very unproductive in absence of-insects,!
but fully productive when artificially fertilised or when insects
have access to them; and that in artificial fertilisation legitimate ®
"crossings gave a yield half as great again as illegitimate.
Hildebrand repeated Darwin’s experiments on P. sinensis, and
ybtained almost identical results. He performed the additional
experiment of fertilising flowers of each kind with their own pollen,
nd found that this was the least productive of all ways. Also
Hildebrand sowed the seeds which resulted from the various modes
| f fertilisation, and showed that the union of two long-styled
flowers produced mainly long-styled plants, and the union of two
short-styled flowers produced mainly short-styled plants; while
legitimate crossing of the two kinds of flowers produced offspring
consisting of both forms in tolerably equal numbers (No. 340,
1864). -
_ Treviranus had already (No. 742, 1863), added P. farinosa, P.
villosa, and P. minima to Darwin’s list of dimorphic species. Mr.
John Scott (No. 692, 1864) enumerated altogether thirty-six
‘species of Primula as dimorphic, and six as homomorphic, and
showed that P. mollis was homomorphic and regularly self-fertilised,
P. scotica homomorphic, but rarely self-fertilised, though fruit-
ful to its own pollen, P. verticillata homomorphic, and usually
unproductive when fertilised with its own pollen.
| _ Axell figures the homomorphice and proterandrous flowers of
P. stricta, and states that they fertilise themselves (17).
_ Ricca describes P. longiflora, All., as homomorphic and proter-

1 Darwin found that, in absence of insects, the long- styled form of P. sinensis
twenty-four times as productive as the short-styled. Hildebrand found both

je barren.
i.e. the fertilisation of either —_ with pollen from the other form.

384 THE FERTILISATION OF FLOWERS. [PART my

androus, the style being long and exserted, and the anthers standing
in the mouth of the long tube (665). ;

Darwin compared the productiveness of legitimate and illegi-
timate crossings in Primula veris, P. elatior, Jacq., P. vulgaris, J
sinensis; Hildebrand in P. sinensis and P. Auricula; Scott in P.
sikkimensis, P. cortusioides, P. involucrata, and P. farinosa (167).

According to Darwin, the common Oxlip is a natural hybrid
between the primrose and cowslip, while the Bardfield Oxlig
(P. elatior, Jacq.) is a good (heterostyled) species (161, 167). —

288. PRIMULA ELATIOR, Jacq.—Honey is secreted by the base
of the ovary. In the short-styled flowers the tube is 15 to 17 mm
long, and begins to widen at a height of 12 to 13 mm.; the stig
stands in the middle of the tube and the anthers in the wid
entrance. In the long-styled form the tube is 12 to 14 mm. long.
and begins to widen out at a height of 4 to 5 mm.; in the middle
of the tube, at the base of the expanded portion stand the
anthers, and the stigma stands at or a little above the mouth o!
the tube. Humble-bees can insert their heads (5 mm. long)
wholly into the tube, and so require a proboscis at least 12 mm.
long to extract the honey from the longest flowers, and one at
least 7 mm. long to do so in the shortest. As in Pulmonaria
the bee, if it gains the honey in the ordinary manner and not bh
biting a hole through the tube, must touch the organs whicl
stand in the mouth of the flower with its head, and those in the
middle of the tube with its maxille; and so, passing from flower te
flower, it effects legitimate cross-fertilisation. Pollen-collecting bee:
are only able to secure their pollen in the short-styled flowers;
they learn to recognise the long-styled plants at a distance anc
to avoid them, and then never perform cross-fertilisation but very)
often self-fertilisation.

Visitors : A. Hymenoptera—A pide : (1) Bombus hortorum, L. 2 § (18—21),
sucking normally, s. and c¢.p., very ab. ; (2) B. silvarum, L. 9 (12—14), sucking
normally ; (3) B. lapidarius, L. 9 (12—14), do. ; (4) B. confusus, Schenck, 9
(12—14), do. ; (5) B. terrestris, L. (7—9), makes a hole in the corolla-tube,
little above the calyx, sometimes biting it with its mandibles, sometimes
piercing it with its maxille, and so reaching the honey with its tongue (I have -
sometimes seen this bee, before boring the flower, make several attempts t
reach the honey in the legitimate way,—-this observation is of interest, ¢
proving that the bee is not guided by instinct to the plant adapted for it, but
that it makes experiments, and gets its honey where and how it can) ; (6) Osmia
rufa, L. ¢@ (7—8); (7) Apis mellifica, L. $, I saw both of these species
thrust their tongues into several flowers, and then abandon the plant ; (8)

:
‘
‘
|
oe |
x

sk

partim.] | THE MECHANISMS OF FLOWERS. 385

~ Anthophora pilipes, F. 9? ¢ (19—21), sucking normally and c.p., very ab. ; (9)
Andrena Gwynana, K. 2 (2%), c.p. on the short-styled form, ab. It holds the
_ anthers in the mouth of the flower with its forefeet, bites the pollen loose with
_ its mandibles and sweeps it with the tarsal brushes of the midlegs into the
eollecting-hairs of the hindlegs. It visits the long-styled form also, but flies
_ away immediately ; not, however, without performing cross-fertilisation in the
momentary visit. I have never seen a pollen-collecting humble-bee alight on
a long-styled flower ; it seems to recognise them at some distance and to avoid
them, B. Diptera—Bombylide: (10) Bombylius discolor, Mgn. (11--12),
s,, ab. ; (11) B, major, L. (10), much less freq., probably in most cases unable
fo reach the honey. C. Coleoptera—Staphylinide : (12) Omalium florale, Pk.,
ab., creeping about in the flowers. See also No. 590, III.

Fig. 126.—I rimula integrifolia, L,

A.—Short-styled, B.—Long-styled plant (nat. size).

C.—Short-styled, D.—Long-styled flower in section (nat. size).
E.—Stigmatic papille of short-styled flower.

F. G.— Ditto of long-styled flower.

H.—Stigma of short-styled flower, I.—Ditto of long-styled flower (x 7).
K.—Moistened pollen of short-styled flower, L.—Dittv of long-styled flower.

_ Primula officinalis, Jacq, (P. veris, L.), the Cowslip.—The

tructure of the flower resembles that of P. elatior ; the visitors

include humble-bees and Anthophora pilipes (509, I11.).

The handsome red Alpine species, Primula integrifolia, L.,

, Jacq., farinosa, L., viscosa, All., minima, L., longiflora, All.,
cc

386 THE FERTILISATION OF FLOWERS. [PART II.

are alladapted for Lepidoptera by their colour and by the narrowin,
of the mouth of the tube. 4

All these species, with the exception of P. longiflora, are helena
styled (609). :

Primula farinosa occurs both on the Alps and in North
Germany, and probably owes this wide distribution to the mild
climate succeeding the Glacial period. On the Alps, where it is
visited by Lepidoptera in great numbers (I have noted forty-eight
species), the entrance of the flower is distinctly narrower than in -
North Germany, where Lepidoptera are less plentiful and where
the plant has probably to depend on the visits of bees (609).

Primula longiflora is homostylic, and adapted by its long narrow
tube for Lepidoptera. The tube is 16 to 24 mm. long, and the
honey is, therefore, accessible only to Macroglossa stellatarum (25 to
28) and to Deilephila euphorbie (25 mm.) pics t 3 all the Alpine
Lepidoptera.

289. Horrontia PALUSTRIS, L.—The flowers are dimorphic.
Honey is secreted by the ovary. In both kinds of flowers, the tube

NIB NS

Fic. 127.— Hottonia palustris, Vu.

1.—Long-styled flower.
2.—Its stigmatic panies:
8.—Short-styled flower
4.—Its stigmatic papille, on the same scale-as 2.

is 4 to 5 mm. long, the organs of one sex standing in its entrance —
and those of the other projecting 8 to 4 mm. beyond. In the —
damp state the pollen-grains of the long-styled form (which i
legitimate crossing have to traverse a style 4 to 5 mm. long) are —
spherules ‘011 to ‘014 mm. in diameter; those of the hoe ee

PART IIT. | THE MECHANISMS OF FLOWERS. 387

_ form (which in legitimate fertilisation traverse a style 7 to 9 mm.

long) are spherules ‘018 to ‘023 mm. in diameter.
The stigma in the long-styled form, which has to receive the

larger pollen-grains, may be seen with a simple lens to be rough

and velvety ; its papillz are very much larger than those on the
stigma in the short-styled form, which appears fairly smooth under

a lens (cf. Fig. 127, 1, 2).

Insects in sucking the honey touch organs of equal height with

the same parts of their bodies, and so effect legitimate cross-
fertilisation regularly. Pollen-seeking insects have no need to

thrust their heads into the flower in the short-styled form, and

hence do not come in contact with its stigma ; they come in contact
with the stigma in long-styled flowers, into which they have to
thrust their heads to reach the pollen. In visiting several long-

styled flowers consecutively they must as a rule bring about

illegitimate crossing. Probably the much greater productiveness
of illegitimate crossings in the case of long-styled than in short-
_ styled flowers (vide next table) is due to the fact that the former
kind of illegitimate crossings occur frequently in nature while the
latter do not, and that the former alone, therefore, are of use in
_ reproducing the plant.

Visitors: A. Hymenoptera—Sphegide: (1) Pompilus viaticus, L., s.,
thrusting its head into the tube. B. Diptera—(a) Empida : (2) Empis livida,
L.; (3) E. leucoptera, Mgn.; (4) E. pennipes, L., all three ab., s.; (0)

i. Syrphide: (5) Eristalis arbustorum, L.; (6) E. nemorum, L., both freq., s. or
be ip. ; (7) Rhingia rostrata, L., s., ab. Five additional visitors (Diptera) are
- enumerated in No. 590, 11. ae

|
|
|

iz
i.
[

Sprengel was aware of the dimorphism. of this plant, and
suspected that it had some unknown purpose. Hottonia palustris
occurs with cleistogamic flowers (167).

‘Mr. John Scott performed on Hottonia palustris the same

fs _ experiments. that Darwin had first instituted on Primula, and

‘obtained likewise the result that legitimate or heteromorphic

crossings are the most productive (692). 128
In the summer of 1867, I repeated Scott’s experiments’ o on

_ specimens which I kept in a large vessel of water in my room, with

the following results :—

“SOY eee

388 THE FERTILISATION OF FLOWERS. [PART III.

; E Sn . | 2a 8
ee | og le fla
=f
Flowers which. | Flowers, by the) 3 | % eo ,| 32 |S 2] 20}
: pollen of which| ¢ s » 2a oe Oa eo =
were artificially Es 5 ays oy 528 E
fertilised theflowers | 33 | 25 | g42| 22 |522| gee
ertilised, were fertilised. E 2 Eg Be 3 a | B32 s =e .
> =o =
Zz | 22 |\43a| ze |e88 | doe
A.—LEGITIMATE CROSSINGS.
la.* | Long-styled ... | Short-styled ... 14 1323 948 | 1323 104 0-078
b.* _ _ 20 17-6 89°3
2a. Short-styled... | Long-styled ... 14 861 615 861 34-7 | 0°:040
b. -- = 6 632 1053 632 27°38 | 0043
c. _ _ 10 495 49°5 ‘

B.—ILLEGITIMATE CROSSINGS OF SEPARATE PLANTS.

8a, Long-styled ... | Long-styled ... 11 764 69°4 764 58°7 0-076
b. ~ — 7 632 90°3 532 33°7 0-063
4a, Short-styled ... | Short-styled... ee ee 17°8 118 1511 0117
b, — _ 12 238 19°8 138 179 | 0129

C.—CROSSINUS BETWEEN FLOWERS OF THE SAME PLANT,

5. | Long-styled ... | Long-styled ... | An unfortunate accident spoilt the results.
oa. Short-styled ... | Short-styled ... 15 134 9
db. _ —_ a hy 5 03

) D.—SticmMaA FERTINISED WITH POLLEN OF THE SAME FLOWER.
| 7a. Long-styled ... Long-styled ... | 11 226 205
b. — —

|; 16 199 12
(33 very
small.)
fa. Short-styled... | Short-styled ... 13 68 5-2 68 9°6 0-141
b. _ _ 17 128 75

* a, b, c, indicate different individual plants.

Although these observations are in some places defective, they
illustrate well on the whole Darwin’s law that in heterostyled
plants legitimate crossings are the most fruitful. hd

Also the preceding table shows clearly that self-fertilisation
and the crossing of flowers on the same plant are much less
productive even than illegitimate crossings of flowers on different
plants. And of very special interest is the fact, brought out by my
experiments, that in Hottonia palustris illegitimate crossing between
different plants of the long-styled form is just as productive as the
legitimate crossings are.)

I have shown above that this kind of illegitimate crossing is to
a great extent performed by pollen-feeding flies. If we suppose
that the superior effect of legitimate crossing in other dimorphic
and trimorphic plants results from their being exclusively or almost
exclusively fertilised legitimately in a state of nature, and that
other ways of fertilisation from long disuse may and do become

* This result is arrived at by comparing 10 and 20 in the foregoing table ; if, on
the other hand, as Darwin rightly insists (No. 167, chap. i.), we add the number of

seeds from all the capsules produced by the two modes of fertilisation, we obtain as

the mean number in the long-styled capsules, after legitimate fertilisation, 91°4,
after illegitimate, 77°5, or in the proportion of 190 to 85. .

- PART IIL. | THE MECHANISMS OF FLOWERS. 389

ia inoperative, we can easily comprehend how in Hottonia palustris

tha application of pollen from a long-styled flower to a long-styled

stigma on another plant has retained its full efficiency.
4 Androsace Vitaliana, K.S., is dimorphic (Treviranus, No. 742;
- Darwin, No. 167).

The Alpine species of Androsace (A. septentrionalis, L., A.
Chamejasme, Host., A. obtusifolia, All., etc.) are homogamic, and

_ visited chiefly by Diptera, but to some extent by Lepidoptera and
- small bees; in absence of insects they are self-fertilised (No. 600,

figs. 140, 141).

___-* Species of Cortusa fertilise themselves, according to Treviranus,

by the style bending back towards the anthers (742).

. Dionysia, Fenzl., is dimorphic according to Kuhn (399).

4 The Alpine species of Soldanella are adapted for bees by the
pendulous or inclined bell-shaped flower, the lilac or violet colour,

the position of the anthers close around the style, and the more

or less complete protection of the honey from small insects by

_ means of the anthers and appendages of the corolla (609,° figs.

_ 146-148),

290. LysIMACHIA VULGARIS, L.—The following varieties of
this plant occur near Lippstadt: (@) on sunny embankments, a
conspicuous form which is never or only rarely self-fertilised ; (0) in
shady hollows, a less conspicuous form which fertilises itself
regularly ; (c) transition forms in spots intermediate in character,
¢g.on the banks of ditches exposed to the sun. In the form (a)
the petals are dark-yellow, red at the base, recurved, expanding
_ widely, about 12 mm. long and 6 mm. broad on an average, and
_ the filaments are red near the end; the style projects. several
millimetres ‘beyond the tallest anthers, so that in case of insect-

' visits, cross-fertilisation takes place regularly, but in absence of

insects, self-fertilisation cannot easily occur. In (0) the petals are

light-yellow and of one colour throughout, 10 mm. long and 5 mm.
_ broad on an average, not spreading out so widely, but for the most

part diverging obliquely upwards; the filaments are greenish-yellow;
the style is of the same length as the two inferior and longer
stamens, so that in absence of insects self-fertilisation always
occurs. (c) The intermediate forms differ from (0) either (1) by the

1 This reasoning, however, is directly opposed to other cases, such as that of —

| _ Linum grandiflorum, in which the long-styled form is quite unproductive with

pollen from another long-styled flower, although from the position of the anthers it
is regularly conveyed to the stigma (No. 167, chap. vi.). ; ‘

- 390 THE FERTILISATION OF FLOWERS. [parr ur.

red colour of the filaments, or (2) by the larger size of the petals,
or (3) in both characters together, or in addition (4) by a slight
red colouring in the base of the corolla, or still further (5) by a
slight extension of the style beyond the longer stamens. All such
intermediate stages between the extreme forms occur in the same
localities, and not unfrequently even on the same plant.

These forms of Lysimachia vulgaris form another illustration
of the law, exemplified in so many previous cases, that while it is
of advantage to the plant when sure of insect-visits to be capable
of cross-fertilisation only, it is above all important that, where
insect-visits are rare, the plant shall be capable of reproducing
itself by self-fertilisation. As

I have not discovered honey in any of the forms of this plant.
The flowers are visited regularly and persistently by pollen-seeking
insects, and sometimes by honey-seeking insects which fly away
after a few vain attempts to find honey.

A. Hymenoptera—(a) Apidw: (1) Macropis labiata, Pz. 2 ¢, rather ab., —
especially the females, on the sunshine-loving form of the plant. I found the
females as a rule only on flowers of this plant, diligently sweeping the flowers
and piling large masses of moistened pollen on their hind legs. I am still
unable to decide where they got the material to moisten the pollen with. I
should suppose that they bored into the succulent tissue of the flower, were it —
not that the mandibles are blunt and fringed at the end : perhaps the sharp
points at the end of the short blunt tongue do this work, which usually belongs
to the mandibles. (2) Halictus zonulus, Sm. ¢, scarce ; (83) Andrena denticu-
lata, K. 3, scarce; (b) Vespide : (4) Odynerus parietum, L. 3, scarce (the last
three had obviously visited the flower in the vain hope of honey). B. Diptera
—Syrphide : (5) Syritta pipiens, L., fp. on the self-fertilised shade-loving
form ; (6) Syrphus balteatus, Deg., f.p.

Lysimachia nummularia, L., is almost always sterile (Darwin,
No. 158), perhaps because all the examples in the same neighbour-
hood come from the same stock (cf. Eug. Warming, No. 762). |

Lysimachia thyrsiflora, L., is proterogynous (762).

Centunculus minimus, L., is regularly self-fertilised, according
to Ascherson (10); it could hardly be otherwise, to judge from the —
inconspicuousness of the flowers,

Anagallis arvensis, L., and A. cerulea, Schreb.—Delpino.
is of opinion that A. cwrulea and arvensis were originally
two forms of a single dimorphic species, which became in- —
dependent (“divorzio di due forme reunite originariamente sovra

una pianta dimorpha;” No, 172, p. 45); but as yet this view is
without proof.

PART 11. ] THE MECHANISMS OF FLOWERS, 391

_ The flowers of both species are adapted for insects in a simple -
and effective way, so that cross-fertilisation in case of insect-visits
and self-fertilisation in absence of insects are equally well insured.
During the sunniest hours of the day, from about 9 A.m. to 3. P.M.,
_the petals (scarlet in A. arvensis, blue in A. cerulea), which cohere
only by a ring at the base, spread out almost to a vertical plane,

which has a diameter of 10 to 12 mm. in A. arvensis and rather
less in A. cerulea ; the five stamens protrude from the centre of the
flower, and the style projects between the stamens and curves
downwards, so that an insect alighting on the lower part of the
_ corolla and going towards the anthers comes first in contact with
_ the stigma. Stigma and anthers ripen simultaneously; the pollen,

Fia. 128.

i, 2.—Anagallis arvensis, L,
1.—Fully expanded,
2.—Half closed.

3, 4.—A. cerulea, Schreb.+

3.—Fully expanded.
4—In section, (x 3}.)
st, stigma.

which coats the anthers all round, is all that the flowers offer to
insect-visitors, unless perhaps the delicate red, jointed, knobbed
_ hairs which clothe the filaments are manipulated by flies with their
- labellze, as I have observed in the case of the hairs upon the
filaments of Verbascum.1 In either case it is to the stamens that
_ insects come, and if they alight on the interior part of the flower as
, _ the most convenient place for them, the downward curvature of the

stigma suffices to insure cross-fertilisation. About 3 P.M. the
_ sepals and petals begin to close up, so that the coloured surface
_ formed by the corolla is reduced to less than a fourth of its former

2 PES

? According to: Delpino, . Anagallis.and also. Verbascwm-are adapted for pollen-
| collecting ‘bees, “which oes to the staminal hairs; but as to Anagallis direct
_ observation i is yet wanting (No. 178, 11. p. 290).

reer e's

392 THE FERTILISATION OF FLOWERS. [PART IIT,

size (ef. Fig. 128, 1 and 2). The plant, therefore, no longer attracts
insects, but by the closure of the flower the stigma is drawn
inwards and brought in contact with the three inferior anthers; so
that self-fertilisation results, unless insects have been attracted
during the warm hours of the day and have removed the pdllen
from the anthers, at the same time cross-fertilising the stigma.
I have not yet observed insects visiting either species. —
Trientalis europea, L., is proterogynous and devoid of honey
(590, III).

Orv. HBENACEZ.

Dospyros virginiana, L., according to Asa Gray, is probab ,
androdicecious (167, 2nd ed.).

OrD. OLEACE 2.

Species of Jasminum are self-fertilised, according to Treviranus
(742), the style curving back towards the anthers. Kuhn mentions
Jasminum as containing dimorphic species (399). ¥

Horsythia is heterostyled (Darwin, No. 167), but not invariably
SO (590, III.). “oa

291. SyRINGA VULGARIS, L.—Honey is secreted by the ovary,
and occupies 2 to 4 mm, of the tube, which is 8 to 10 mm. long;

Fic. 129,—Syringa vulgaris, L.
1,—Flower, from the side, after removal of half the corolla.
2.—Ditto, from above.

8.—Mouth of the flower, immediately after its expansion.
4.—Ditto, somewhat later.

8, sepal; p, petal ; fi, filament; a, anther; po, pollen ; ov, ovary ; st, stigma.

it is sheltered from rain by the two stamens, which to a great t
extent fill up the mouth of the tube, and the length of the tube

parr] © THE MECHANISMS OF FLOWERS. 393

_ protects it from short-lipped insects: it is all the more diligently
sought therefore by insects whose proboscis is sufficiently long.
i An insect in inserting its proboscis brings it in contact first with
_ the anthers, which stand in the mouth of the tube, and then with
_ the stigma, which is lower down: stigma and anthers are matured
simultaneously. If a smooth, dry needle be thrust into the flower,
it may readily be seen that as it enters no pollen sticks to it, and
as it is withdrawn pollen only adheres to it for 2 to 4 mm. at the
end, where it is moist with honey. The same thing doubtless
takes place in the case of honey-sucking insects, which must
therefore perform cross-fertilisation regularly ; while pollen-feeding
insects can scarcely ever effect cross-fertilisation, but must often
‘cause the loosened pollen to fall upon the stigma and lead to self-
fertilisation. In absence of insects, self-fertilisation always occurs
ultimately.

_ According to Batalin (38), there are two cultivated varieties—
one proterandrous, the other proterogynous. I have only once
‘seen the proterandrous variety ; all the plants on which I made my
_ observations were homogamic.

_ Sprengel never observed insects on this plant.

-
I
i
‘
’

———

~ TO TER 0, i TAS ome

Visitors : A. Hymenoptera—(a) Apide: (1) Bombus lapidarius, L. § 9
(10—14), ab. ; (2) B. terrestris, L. § 2? (7—9); (3) B. hortorum, L.? §
(18—21), very ab. ; (4) Apis mellifica, L. $ (6), ab. ; all sucking. (To judge
from the length of its proboscis, the honey-bee can obtain only part of the
honey) ; (5) Eucera longicornis, L. ¢ (10—12) ; (6) Anthophora pilipes, F.
~ 2 ¢ (19-21), ab. ; (7) Osmia rufa, L. 9 (7—9), ab., the three last sucking ;
(8) Halictus albipes, F. 9 ; (b)Vespide: (9) Odynerus sp. ; the two last seek
in vain for honey. B. Diptera—(a) Bombylidw: (10) Bombylius major, L.
(10), s. ; (6) Syrphide : (11) Rhingia rostrata, L. (11—12), very ab., s. and fp. ;
(12) Xylota segnis, L., f.p., after seeking in vain for honey; (13) Syritta
" pipiens, L. (3), f.p. ; (14) Eristalis sepulcralis, L., fp. ; (15) E. arbustorum, L.
_ (4-5), f.p. ©. Lepidoptera—(a) Rhopalocera : (16) Papilio Machaon, L. (18) ;
(17) P. Podalirius, L.; both ab. (Stromberg) ; (18) Vanessa urticz, L. (12), ab. ;

(19) Pieris cardamines, L. (11) ; (20) P. brassicae, L. (15) ; (21) P. napi, L. ;
7 (22) P. rape, L.; all three ab. ; (b) Sphinges: (23) Macroglossa fuciformis, L.,
_ freq. (Stromberg) ; (24) M. stellatarum, L., do.

i

Syringa persica, L., is gynomoncecious (605). _

+e

292, LIGUSTRUM VULGARE, L.—Honey is secreted by the ovary,
and lies at the base of the tube, which is scarcely 3 mm. long
and expands above into a four-lobed, rarely five-lobed, limb. The
- more or less distinctly bilobed stigma is situated at the mouth of
the tube, The two (rarely three) stamens are matured simul-

wae

.
hg

p
!
4
}
’

-

BO4 THE FERTILISATION OF FLOWERS. [PART 11]

taneously with the stigma, and project from the tube ; the anther
dehisce laterally, but so widely, that the whole of their inne
faces are covered with pollen. The two anthers stand sometime
wide apart (Fig. 130, 4), at other times they bend inwards ove
the stigma (1, 2); in the former case, an insect’s proboscis ir
entering the flower first touches with one side an anther, anc
immediately afterwards the stigma with the opposite side, and s¢
passing from flower. to flower. leads to. eross-fertilisation ;-in -the
latter case self-fertilisation and. cross-fertilisation may result- ir
differently. Insect-visits are very scarce by day; perhaps tl

/ LA mt

a = fins
CY,
Sa

Fic. 130.—Ligustrum vulgare, Li.
1.—Flower, seen obliquely from above.

2. —Ditto, not so far advanced, seen directly from above.
3, 4.—Flowers, seen from the side, after removal of half the corolla (x 33).

white, sweet-scented flowers attract nocturnal Lepidoptera ‘in
greater numbers. Flowers whose anthers are inclined inwards
above the stigma always fertilise themselves in absence of insects

7

A. Hymenoptera—Apide : (1) Heriades truncorum, L., s. (June 27, 1869).
B, Diptera—Syrphide : (2) Eristalis nemorum, L., s. (June 21, 1868). A furthe:
list of visitors (four beetles, two flies, two bees, seven Lepidoptera) is given in
No. 590, 111. SA VE

Orv, APOCYNACEZ.

293. Vinca minor, L.—The structure of the flower was
correctly described by Sprengel, but incorrectly explained, since
he overlooked here, as elsewhere, the advantage of cross-fertilisa-
tion, Sprengel had. found Thrips, but no other insect, in the —
flower, and he supposed that in creeping in and out of the flower —
it transferred pollen to the stigma of the same flower, and-that in —
this way alone fertilisation was effected, ie’ a

Darwin (153) gave the first correct account of the mechan-
ism of Vinca, for he recognised that a long thin proboscis in
passing into the flower gets smeared with adhesive matter, and t

> oh

5
-
-

111. | THE MECHANISMS OF FLOWERS. 395

in being drawn out carries with it pollen, which in the next
flower is left attached to the stigmatic edge of the disk which
terminates the style. And in the case of Vinca major, which
Darwin had never seen visited by insects in England nor bearing
fruit, he obtained good seed by repeatedly passing a fine bristle
down among the stamens in six flowers on two plants, and thus
effecting both cross- and self-fertilisation. Another English ob-
server (122A) was led by Darwin's account to perform the same
k xperiment on Vinea rosea, L.; he obtained good seed, though he
had before found the plant always unproductive. A third English
‘observer (636A) maintained that he had got good seed from
Vinca rosea when left to itself, But Darwin showed that this last

Fic, 131.—Vinea minor, L,

Flower, after removal of the anterior part of the corolla.

_ @, ovary; bb, two yellow honey-glands at the base of the ovary; ¢, style; d, point where the

aments separate from the corolla, marked externally by depressions; d,-e, filament with its

ward bend ; e, f, anther, dehiscing introrsely ; g, thickening of the style; h, disk-shaped end of
veg surrounded with viscid matter and functioning as a stigma on two sides of its lower

e; k, hairs upon the stigma-disk which receive the pollen as it issues from the anthers.

‘result was faulty, as the plant stood in a greenhouse with open
windows, by which moths might enter (153, p. 831).

_ JDelpino, unaware of these observations, gave later a full
wccount, agreeing with Darwin’s, of the mechanism of the flower
of Vinca; his description was taken from V. rosea, in which the
lower border of the stigmatic disk extends downwards in the form
. inverted cup (173, pp. 15-17). Hildebrand afterwards gave
his res of the flowers, which illustrated Delpino’s account (352).

~ None of the foregoing observers seem to have seen any insects
except Thrips on any species of Vinca, which is remarkable, as
V. minor in its season (beginning of April until May) is most
conspicuous and rich in honey, and in my experience is in sunny
weather visited abundantly by insects. The tube of the corolla is

11 mm. long in V. minor, but insects can easily insert their heads
:

-

_..

396 THE FERTILISATION OF FLOWERS. [PART I

into the upper part until the way is barred immediately above th
anthers by hairs ; the two yellow nectaries lying beside the ova
are distant only 8 mm. from this point.

Visitors: A. Hymenoptera—Apide: (1) Bombus hortorum, L. ? (21
(2) B. lapidarius, L. 9 (12—14); (8) B. agrorum, F. 9 (12—15) ; all thre
very ab. (4) B. terrestris, L. 2 (7—9), lessab. ; (5) B. vestalis, Foure. ? (12
scarce ; (6) Anthophora pilipes, F. ? ¢ (19—21), very ab. ; (7) Osmia ruf
L. ¢ (7—8). B. Diptera—Bombylide : (8) Bombylius major, L. (10) ; (9) I
discolor, Mik. (11—12), very ab., the latter species (April 18, 1869) as early ¢
7.45 a.m. All the visitors sucking normally. C. Thysanoptera—(10) Thrip
ab. See also No. 590, II.

294, Vinca MAJor, L.—I have once seen Bombus agrorum,
F. 9 (12—15 mm.), visiting this plant; it sucked numerous flowers,
thrusting its head completely into the mouth of the tube. ?
Tabernemontana echinata, Aubl., is barren when fertilised with
pollen of the same flower or of other flowers on the same plant, an
is productive only when fertilised with pollen from another plant

(Fritz Miiller, No. 359). |
Apocynum androsemifolium, L., is fertilised by butterflies, aul
cements its pollen to the insect’s tongue (Ludwig, No. 432). Fi

— Apocynum hypericifolium, Ait., has the same arrangement

(Ludwig, No. 443). ri

Nerium Oleander, L., and N. odorwm, Ait., are adapted for long-
tongued Lepidoptera (443).

In Rhynchodia (Rhynchospermum) jasminoides, according
Hildebrand, as in Vinca, the insect’s proboscis is smeared with
adhesive matter as it enters, and cemented to the pollen as it is
withdrawn (No. 356, p. 509).

Orv. ASCLEPIADEZ.

295. ASCLEPIAS CoRNUTI, Dec. (A. syriaca, L.).—The Asclepia-
dee rival the Orchids, if not in the variety of their forms, at least
in their complexity and in their perfect adaptation to insect-visit-
ors. Hildebrand has so thoroughly described the way in which A,
Cornutt is fertilised by insects (347), that I have scarcely any-
thing new to add to his description; yet it may be well that
should illustrate the complex mechanism by figures, and catalogue
the insects that effect fertilisation. |

The two ovaries (g, 14) are surrounded by a fleshy column
(m, 14, 2, 8, 4) and covered by a thick, fleshy disk (p, 14), and

III. | THE MECHANISMS OF FLOWERS. 397

ii i iy Utre) tv, /
Wate NI! Ai IH HI i (\
a: Fic. 132.—Asclepias Cornuti, Dec.
_ 1.—Flower, after removal of sepals and petals, viewed from above (x 33).
— 2.—Ditto, from thé side.

2.
_ $,—Ditto, after removal of the euculli (x 7).
4.—Ditto, after removal of one anther

5.—The anther removed from Fig. 4, outer view.
| _ 6.—Ditto, inner view.
7.—A cucullus, from the side (x 34).
| _-8,— Ditto, in section.
_ _9,.—Pollinia, immediately after extraction, outer view (x 7).
_ 10.—Ditto, when the twisting of the retinacula is half completed.
al er peed twisting complete. 3
_ 12,.—Corpuseculum and retinacula more magnified, outer view.
13.—Ditto, inner view. i
_ 14.—Section of flower, after removal of sepals, petals, and cuculli. :
4a, cucullus; b, its conical process; ¢, upper membranous process of anther; d, outside of
ither-loculus ; e, anther-wing; f, slit between two adjacent anther-wings; g, corpusculum ;
, Tetinaculum ; é, pollinium; k, k, empty loculi of anther; J, connective ; m, column ;-n, place of
schment of a cucullus; o, stigmatic chamber ; p, fleshy stigma-disk ; q, ovary.

398 THE FERTILISATION OF FLOWERS. [PARY TIT,

they are only capable of fecundation at five stigmatic spots close
beneath the lower border of the disk (0, 14,4). The column, which:
really consists of the united staminal filaments, bears at its upper
end five anthers. The anthers lie close around the stigma-disk ;
each of them lodges two flattened pollefi-masses (7, 4, 9, 10,11) in
two pouches (%, 6), which are open internally, and are indicated
externally by slight swellings (d, d, 3, 4,5). A thin membranous
process of the anther (¢, 5, 14) rests upon the top of the stigma-disk,
and on each side the anther is produced into a triangular mem-
branous expansion (ala or anther-wing) (¢, 3, 5, 14), which stands
out perpendicular to the column close to the corresponding process
of the adjacent anther. Between the two adjacent processe
of each pair of anthers, there is left only a very narrow slit which
is distinctly wider at its lower end (f, 3, 4). The slit leads into an
elongated space which we may call the stigmatic chamber (0, 4, 14);
for about the middle of its vertical height the stigma is exposed
At the upper end of the slit, visible from the outside, is a bright,
black body (corpusculum) of regular shape (g, 1 to 14), which is
seen on closer examination to be a thin, hard, horny lamina. Its
sides are bent forward for its whole length so that their edges lie
close together, and in the middle of its lower border is a wedge
shaped shit. To this corpusculum the two adjacent pollinia of two
neighbouring anthers are attached by bands (retinacula)! which
lie hidden beneath the anthers (h, 4, 9, 13). «
The upper end of the column carries, besides the five anthers,
five hollow, fleshy, foliar organs (eweulli), which secrete a large
quantity of honey; they stand opposite to the anthers, and from
each an incurved pointed process proceeds, the upper extremity of
which rests upon the top of the stigma-disk, and lying on the
superior membranous process of the anthers (c) keeps the whol 7
firmly in place. |
This singular apparatus acts in the following way :— ;
Insects (bees, wasps, flies) which creep about the umbels in
search of honey, attracted by the sweet scent of the flowers, slip
upon the smooth parts of the flower until a foot enters the wid
inferior part of a slit, in which at last it gets a firm hold. Whe
the insect tries to draw its foot out in order to proceed furthe
the diverging claws are caught by the apposed edges of the anther-
wings, and guided upwards in the slit, so that one or other of the
two claws is brought without fail into the notch in the lower
border of the corpusculum and there held fast. Ifthe insect now
* These structures are not in any sense homologous with the retinaewla of Orchids.

eri] THE MECHANISMS OF FLOWERS. 399

draws its foot forcibly out, it brings with it the corpusculum (g) and
e two pollinia (7) attached to it by their retinacula (kh). The
Pp nia stand wide apart when they are extracted (9); but the
retinacula twist inwards as they dry (cf. 9, 10, 11) bringing the
pollinia so close together that they may easily be introduced into
t mother slit. As the insect moves on over the umbel, its foot bearing
the ae pollinia slips into the lower part of aslit of another flower ; and
this time as the leg is drawn up the pollinia are left in the pigs
m E tic chamber opposite to the stigma, since the slit is too narrow to
admit of their further passage upwards ; and the insect, freeing its
b oot by a violent pull snaps the retinacula and so. extricates itself.
‘The pollinia are left behind in the stigmatic chamber, while the
, r pusculum and its broken retinacula are carried off still firmly
ached to the insect’s foot. The insect continues its visits, and
he retinacula attached to its feet now get fixed in corpuscula as
he claws did before, and an insect’s foot after repeated visits may
“$01 metimes be seen bearing many corpuscula with their retinacula,
often dichotomously arranged. :
_ Delpino saw A. Cornuti in F lorence fertilised in the manner
yhich I have described by Scolia hortorwm, NS. bicincta, Apis mellifica,
and Bombus italicus (172, 352).
__ Ihave observed many bees, wasps, ants, and flies, on the flowers
of A. Cornuti in Thuringia. Dr. Hildebrand sent me a still larger
number of insects with corpuscula on their claws, which he had
‘caught on this plant at Freiburg in the first hot days of July,
1870. .
_ The following list comprises the insects observed by Delpino,
idebrand, and myself :— |
“Gl Florence, Delpino; F. = Freiburg, Hildebrand ; Th. =
Whuringia, H. Miller ; | = with corpuscula on -their afters

A. Pegg ea Apide: (1) Apis mellifica, L. 9! (Fl, Th.) ; (2)
Bombus italicus, L.! (FL); (3) B. terrestris, L. 8 ¢! (F.) ; (4) B. hypnorum,
. 1 (F.) ; (5) Halictns Scabiosee, Ill. 9 ! (F.) ; (6) H. cylindricus, id BY
H. quadricinctus, F. 2! (F.) 5 (8) Several: small species of Halictus (Th.),
which I never saw caught in the slits ; (9) Ceelioxys sp. 9 ¢! (F.) ; (10)
Stelis aterrima, Pz. 9 ! (FE); (b) Sphegide : (11) Scolia hortorum, L.! (F1.) ;
2) Se. bicincta! (Fl.); (13) Sc. quadripunctata, F. 9! (F.); (14) Ammo-
phila sabulosa, L. 9! (F.) ; (15) Psammophila affinis, K. 9 ! (F.) ; (¢) Vespide :
16) Polistes gallica, L. 9 ! (F., Th.), and var. diadema ! (Th.) ; (d) Formicide :
17) Various species (Th.); they got caught in the slits and were not able to set
emselves free. I‘have never seen an ant tear its leg off in order to escape. B.
Jiptera—(a) Syrphide : (18) Teens tenax, L.! (F., Th:) ; (19) E. seek
1! (Th.) ; (20) E. nemorum, L.! (Th.) ; (21) ‘Melithreptus scriptus, L. (Th.) ;

400 THE FERTILISATION OF FLOWERS. [PART I I

(22). M. teniatus, Mgn. (Th.); both of these obtained the honey withot
getting caught in the slits. (b) Muscide: (23) Ocyptera brassicaria, F, (F.)
(24) Lucilia (Th.) In several flowers which I dissected, the corpuscula an¢
pollen masses were still in their places, though pollinia, which must hay
come from other flowers, had been inserted into the stigmatic chambers.

The following additional list is taken from my Weiter
Beobachtungen, i. p. 61. The insects were for the most par
observed in my garden in July. ;

A. Diptera—Empide : Empis livida, L., s.! B. Hymenoptera—A pide.
Bombus muscorum, L. (B. agrorum, F.) g¢, s.! ab., Wurzburg; Ceelioxys
conoidea, Ill, 9 ¢! ab. C. Lepidoptera—Noctuide : Hypena proboscidalis
L., s., not extracting the pollinia; Plusia gamma, L., do., in the evening
Sphingide : Sesia formiciformis, Esp. g (teste Speyer), do. D. Neuroptera:
Panorpa communis, L., s. and extracting the pollinia. |

Asclepias curassavica, L., according to Fritz Miiller’s observation:
in South Brazil, is sometimes visited by wasps, but infinitely mo:
frequently by a great variety of butterflies, on whose legs the
corpuscula and pollinia of this plant may often be found. One

”
vl Ly
XQ] Dx
ai & ! i Jf
a wy
i g A pa es «a a
gee eon

Fic. 133,
Butterfly’s foot, bearing eleven corpuscula (k) and eight pollinia (st) of Asclepias curassavica, L. &

butterfly, like a Vanessa, bore on one leg no less than eleven cor-—
puscula of this Asclepias. Eight only of the twenty-two pollinia
remained, the others had been employed in the fertilisation of
other flowers. i
Asclepias tenwifolia (?) was seen by Hildebrand to be fertilised
by a cabbage-white butterfly (361). |
Gomphocarpus (Asclepias) fruticosa, R, Br.—The structure of
the flower and the way in which insects visit it have been described —
by Sprengel (No. 702, pp. 139-150): he fell into the error of
considering the upper surface of the stigma-disk to be the stigma.
Araujia albens, Brot. (Physianthus, Mart.), is fertilised by
humble-bees, to whose tongues the corpuscula become attached

as

PART III. } THE MECHANISMS OF FLOWERS. 401
Vincetomrcum officinale, L., is fertilised by the proboscides of small
flies, Stapelia hirsuta, L., and S. grandiflora, Mass., by Musca
6 vtoria and Sarcophaga carnaria, which are attracted by the
‘putrid odour of the flowers. As a rule, in those Asclepiadez in
which fertilisation is effected by an insect’s proboscis (Araujia,
Cynanchum, Vincetoxicum, Stapelia, Boucerosia), the five nectaries
alternate with the stamens; in those in which fertilisation is
: effected by the legs of insects (Asclepias, Gomphocarpus, Centro-
_stemma, Hoya), the: reverse holds ; in Stephanotis, which is fertilised
y the proboscides of nocturnal Liidoptera, the base of the tube
of the corolla forms a large honey-receptacle (172, 352).
: In Ceropejia elegans, Wall., the flower forms a temporary prison
f for its visitors, very much like that of Aristolochia COlematitis, L.
Small flies (Gymnopa opaca) creep through the tube of the flower,
which is at first erect, into the expanded portion which surrounds
the reproductive organs; in this expanded portion, or cage, whose
entrance is surrounded by stiff hairs pointing inwards, they are
imprisoned for a whole day. On the second day these hairs wither,
the flower bends over, the flies creep out with the pollinia attached
to their proboscides, and seek new flowers, in whose cages they
introduce the pollinia into the slits leading to the stigma, and get
~ new pollinia attached to their proboscides (178, 360).
— Cynanchum Vincetoxicum, R. Br.—The flower agrees in most
points with that of Asclepias Cornutt.
_ The dirty-white flowers of Cynanchum, devoid of the pleasant
_ perfume of Asclepias, are adapted for fertilisation by carrion-loving
_ flies, which convey the exceedingly minute pollinia, not with their
_ claws, but with the bristles on their proboscides. Further, while
- in Asclepias Cornuti the foliar appendages of the anthers form five
fleshy cups filled with honey alternating with the corpuscula, here
_ the same appendages of the anthers form high vaulted fieshy bodies
coherent into a ring; and alternating with them are five deep
BP ctariferous pits immediately below the five corpuscula. Into
these pits, insects thrust their proboscides, to suck the nectar.
When Muscide (in which the proboscis is set with erect bristles)
“do this, it is almost inevitable that when the proboscis is being
drawn back, one or other of its bristles gets caught in the slit,
“which i is placed over the nectary and is Rider below than above ;
after entering the slit, it glides upwards between the lateral anthers
"wings of the two neighbouring anthers, straight into the inferior
wedge-shaped notch of the corpusculum, and is there held fast.
When the fly now gives a slight pull backwards in order to free
DD

4
f
‘
¥
We

402 THE FERTILISATION OF FLOWERS. [PART III.

its proboscis, held fast thus by a bristle, it tears away the corpuscu-
lum and its two pollinia; and the pollinia and the processes which
carry them, both of which were hitherto kept moist beneath the
anthers, are now brought for the first time into the open air, and
begin to be dried up. In consequence of this, the processes, which
previously stood out in opposite directions, now bend so that the
pollinia come close together, face to face. If the fly now inserts
its proboscis into another nectary on the same flower, it will be in
a slightly different position with regard to the slit in the case of
each different nectary, and for this reason alone the same bristle
will not be caught. Besides, it is a considerable time before
the processes are so far dried that both pollinia of the same
corpusculum can be inserted into the slit along with the bristle
that they are attached to, so that, as a rule, the fly has mean-
while flown away to another plant. Here, if a proboscis-bristle
bearing pollinia (which has.now become closely approximated) gets —
again caught in the slit, one (or both) of the pollinia slides into
the stigmatic chamber which lies behind the slit, and remaims —
sticking in it, torn away from the process that attached it to the
corpusculum. So crossing of separate flowers, and for the most
part of separate plants, is rogulanby effected. Other visitors besides
carrion-loving flies (¢.g. Hmpis, Polistes), occasionally attach one or
more corpuscula to the tips of their proboscides, but can scarcely
ever effect cross-fertilisation (609).
Hoya globulosa.—Myr. Worthington Smith has recently given a
minute description of the fertilisation of this flower (699). He states
that the corpuscular processes (retinacula) are elastic! When in~
the flower they are like an extended spring, but the instant the
pollinia are withdrawn the spring closes, and the two pollinia quickly —
cross each other and hold tightly on to the insect’s foot. The flower
is distinctly proterandrous,
Darwin describes a very remarkable instance of Hoya carnosa
bearing cleistogamic flowers in cultivation (167). |
Stapelia also has cleistogamic flowers, according to Kuhn (399).
Periploca greca, L.—The mode of fertilisation has been described
by Delpino (172, 352).

Orv. GENTIANEL.

Gentiana lutea, L.—The honey is freely exposed, and I have
found the plant visited by twenty-seven species of mostly short-
lipped insects. The flower is homogamous, and self-fertilisation is
not impossible (570, vol. xv. ; 609). .

ART 1IT.] THE MECHANISMS OF FLOWERS. 403

_ Gentiana punctata, L., is proterogynous; @. acaulis, L., and
—G. aselepiadea, L., are proterandrous. All three are adapted for
a Beeble-bees (570, vol. xv.; 609, figs. 128-130).

_ 296. GENTIANA PNEUMONANTHE, L. (Sprengel, No. 702, pp.
150- 152). —Honey is secreted by the base of the ovary. The
corolla i is 25 to 30 mm. long, and 8 to 10 mm. wide at the mouth,
and it closes in dull weather, so that the honey is protected from
1 The tube suddenly narrows below its middle, and the
stamens, which from this point downwards are attached to the
corolla, lie close to the ovary. A humble-bee can therefore creep
lown as far as the middle of the tube; but in order to reach the

f
i
4

.
ALT

ii
i
ff
H
iy
:
.
.
hi:

Fic. 134.—Gentiana lutea, L.

A.—Flower, slightly magnified. s, sepal; p, petal.
B.—Base of the ovary. n, annular swelling which secretes honey ; ji, Hiiamnenit:

honey, it must insert its proboscis between two stamens and the

corolla, and for this purpose a proboscis 12 to 14 mm. long is
necessary. In creeping into a young flower, the bee comes in
contact with the anthers, which closely surround the still unripe
stigmas and display the pollen on their outer surfaces; in creeping
_ into an older flower it touches, with the same part that in a young
| flower got dusted with pollen, the papillar side of the two stigmas,
| which now stand above the anthers and are recurved so that their

__ 1 Sprengel thought that the honey was sheltered from rain by the closeness of
filaments to the ovary; but if one lets a few drops of’ water fall into an open

er, they reach the honey easily. Here, as in many other cases, the structure
ich Sprengel believed to be designed to shelter the honey from rain has rather
object of excluding short- lipped and useless insects.

DD2

404 THE FERTILISATION OF FLOWERS. [parr m1.

papillar inner surfaces are exposed to contact with the bee. So if
bees visit the flower, cross-fertilisation seems to be insured; in
absence of insects, self-fertilisation seems to be rendered impossiblal
by the well-marked proterandry, and by the position of the anthers
in regard to the ripe stigmas. I have only noticed humble-bees
visiting the plant: viz. (1) Bombus agrorum, F. ¢ (12—15); (2) B.
senilis, Sm. 9 (1415), both very frequent, sucking honey only.

Gentiana ciliata, L., is proterandrous, and adapted for humble-
bees. Honey is secreted by yellow fleshy areas of the base of the
corolla between each pair of stamens (No. 6009, fig. 132). |

Gentiana bavarica, l., and G. verna, L., are adapted for cross-
fertilisation by Lepidoptera. The most important visitor seems to
be Macroglossa stellatarum (No. 570, vol. xv. ; No. 609, fig. 131).

G. nivalis, L.—The flower resembles the ine preceding species
in structure, but is less conspicuous and less visited by insects ;
case of need it fertilises itself (570, 609).

297. GENTIANA AMARELLA, L.—Honey is secreted by five
green fleshy spots at the base of the corolla, alternating with the
stamens; it is sheltered from rain by the closing of the flower dur-_
ing dull weather, and is protected from flies by long, erect hai
developed on the interior of the corolla at the junction of its tube
and limb. The plant grows among grass, and accordingly the
lobes of the erect corolla spread out to be mainly conspicuous from
above.

The tube is 16 to 18 mm. long, but as it is 6 mm, wide at th
mouth a humble-bee can insert the whole of its head and reack
the honey with a proboscis 10 to 12 mm. long. Unlike G. Pneu=
monanthe, the flowers are homogamous. When the flower opens
the anthers dehisce, after turning their dehiscent sides, which in the
young bud were turned outwards, upwards so as to be touched the
more certainly by the bee’s head. The two terminal lobes of the
style are already expanded and provided with stigmatic papilla.
In case of insect-visits, self-fertilisation is not impossible; but
since the stigma stands above the anthers, the insect as a rule
comes in contact with it first, and effects cross-fertilisation. After
the pollen is shed the anthers again come to lie in a line with the
filaments and place themselves close round the style. Ihave not

observed whether self-fertilisation occurs in absence of insects. I
have seen Bombus silvarum, L. ? (12—14), visiting the pam
and sucking numerous flowers (Sept. 30, 1869).

Gentiana tenella, Rotth. (@. glacialis, Thom. ), G. nana, 7

P. RT III. | THE MECHANISMS OF FLOWERS. 405

|G. campestris, L., and G. obtusifolia, Willd., are adapted for fertili-
1 sation by humble-bees and Lepidoptera in the same way as
G. Amarelia, L. (No. 570, vol. xv.; No. 609, figs. 133-135).
4

bb
A
h

Hil
D
Fic 135.—Gentiana campestris, L.

A.—An old flower. The calyx and nearly half of the corolla have been removed.
_ 8B.—Essential organs from a flower in the act of opening. The stigma is mature, the anth¢

@ still closed ; but they dehisced while I was drawing them (B’).
C,—Upper part of the pistil and of two opposite stamens, in their natural position: from a
somewhat older flower.
um Sm whose branches have closed up after being dusted with pollen (x 7). (Madulein
: @ un e ; 1879.
H.-A flower viewed directly from above (natural size).
had part of the pistil and of two stamens in their natural position: from still older
wer (xX 7).
(Albula, August 20, 1878).

ay
to
>

¢ . obtusifolia is proterandrous, G. tenella and G. nana homo-
gamous, G. campestris sometimes homogamous, sometimes slightly
_ proterogynous.

ye

REVIEW OF THE GENUS GENTIANA.

_ A comparison of the very numerous Alpine Gentians suggests
the following theory of their evolution.
ia The genus Gentiana splits into two main divisions, in one of
| which honey is secreted by the base of the ovary, in the other by
| _ the base of the corolla.
| We have an offshoot of the first main division in G. lutea,
_ which stands on a much lower grade than the other species and
hearer to the primitive form. The ancestors of the genus un-

| doubtedly had, like G. Jutem, fully open flowers with almost free

406 THE FERTILISATION OF FLOWERS. [PART IIT

petals, and offered their insect-visitors either honey lying fully
exposed in the angle between ovary and corolla, or pollen only.
In either case the most various insects were admitted, and they
performed cross-fertilisation (as in G. /wtew) casually and irregularly,
so that the power of spontaneous self-fertilisation could no more
be dispensed with than in G. lutea.

In both main divisions, as the nectaries became more perfect,
bees and especially humble-bees proved themselves the most
efficient cross-fertilisers; and in relation to their visits the cam-
panulate form of flower was evolved. Unbidden guests were.
excluded from the honey in the first division by the development
of deep honey-passages, cross-fertilisation in case of bees’ visits
being insured by the position of the anthers in a ring close round
the style (sub-genus Cwlanthe; species purpurea, pannonica,
punctata, eruciata, asclepiadea, Pneumonanthe, Frelichu, frigida,
acaulis). Later, as Lepidoptera made their influence felt, the corolla
in Celanthe got longer and narrower, the folds which narrow it
became more perfect, and the bilobed stigma became developed
into a disk closing the mouth of the tube. Thus resulted the
Alpine sub-genus Cyclostigma, adapted for long-tongued Lepidop- —
tera (species bavarica, verna, estiva, umbricata, pumila, utriculosa,
nivalis). 3

In the second division, hairs on the corolla afforded imperfect
protection against unbidden guests, and narrowing of the corolla
made it more certain that both stigma and anthers should be
touched by the bee (sub-genus Crossopetalum ,; species ciliata, L.).
And finally, in a special offshoot of this division, as Lepidoptera here —
also came to have a decided influence as cross-fertilisers, the fringe
of hairs at the mouth of the corolla became more developed,
excluding all visitors except humble-bees and Lepidoptera from the ~
honey, and the corolla became so narrow that Lepidoptera as well
as humble-bees must perform cross-fertilisation in inserting their —
proboscides (sub-genus Endotricha ; species campestris, germantca,
Amarella, obtusifolia, tenella, nana). :

The primitive yellow colour, retained in G. lutea, was gradually
exchanged for blue by the influence of the humble-bees, and
instructive transition-stages in this process are preserved among”
the species of Celanthe.1 But after the blue colour was once |
firmly established it was retained throughout the changes by whichy
Celanthe passed into Cyclostigma (609). ;

' CO. pwnetata has only blue spots on the pale-yellow ground of the corolla ; and in ‘
C. purpwrea, the outside of the corolla is bluish-purple, but the inside is still yellow.

parti] § THE MECHANISMS OF FLOWERS. 407

_ 298. EryTHra#aA CrnTAURIUM, L.—I, like Sprengel, have
failed to find any honey in this flower, though I have seen it
repeatedly visited by Lepidoptera, and though the spiral twisting
of the stamens (like the twisting of the stigma in several Silenew
fertilised by Lepidoptera) seems to be an adaptation to insure their
_ being touched by the thin proboscis of these insects. Probably
_ the insect pierces some soft tissue with the sharp points at the tip
_ of its proboscis.

Visitors : Lepidoptera—(a) Sphinges: On July 10, 1868, in Thuringia, I
saw Macroglossa stellatarum, L., sucking first on Dianthus Carthusianorum
and then on Z. Centaurium ; (b) Noctue: On Sept. 1, 1871, at Lippstadt, my
_ son Hermann saw (2) Plusia gamma, L., and (3) Agrotis pronuba, L., freq.
_ sucking persistently on flowers of this plant. An additional list, including five
_ Lepidoptera, three bees, and one Empis, is given in No. 599, r11.

Mr. A. 8. Wilson found this plant heterostyled and with
_ dimorphic pollen-grains (780).

= Limnanthemum (Kuhn, No. 399) and Villarsia (=Limnanthemum
_ Humboldtianum, Fritz Miiller, No. 550) are dimorphic (Darwin,

No. 167, p. 116).

Menyanthes trifoliata, L., is well known to be dimorphic. In
a small marsh near Lippstadt, sometimes flooded by the Lippe,
which probably brought the seeds, I have found the long-styled
4 form only ; and I have never observed ripe fruit there.

Orv. POLEMONIACEZ.

Cobea pendulitora is fertilised by Sphingide: (226), C. scandens,
Cav., by humble-bees (52).
Collomia grandiflora (Dougl.), Lindl., has cleistogamic flowers

(423, 424, 685).

s
s
-

ro

i
;

299. PHLOX PANICULATA, L.—Sprengel recognised the pro-
_ terandrous condition of this flower, and found it to be visited by
_ butterflies. I have seen Conops flavipes, L., sucking honey, and
Hristalis tenax, L., very frequently eating pollen on the flowers.
Polemonium carulewm, L., is likewise proterandrous. - Sprengel
overlooked the dichogamous panded 4 in this plant, but Axell (17)
_ figures the proterandrons flowers.?
The honey is secreted in this species and i in Phlox paniculata by
_ the lower fleshy part of the ovary.

=, 2 eee also my Alpenblumen, pp. 257-259, fig. 97, and | Weitere Beobachtungen, 11.
pp. 8

408 THE FERTILISATION OF FLOWERS. [parr m1.

Treviranus supposed that Polemoniacee fertilise themselves

before the flowers open (742).

Gilia pulchella, Dougl., and G. (Leptosiphon) micrantha, Steud.,

are believed by Darwin (167) to be heterostyled.

Professor Asa Gray considers Paloz subulata, L., to be hetero-

styled, but Darwin (167) shows that the great variability of the

stigmas and pollen-grains makes this a perplexing case. He says,

Possibly this species was once heterostyled, but is now becoming
sub-dicecious, the short-styled plants having been rendered more
feminine in nature.” (Forms of Flowers, p. 121.)

Orv. BORAGINE ZL.
Tribe Cordiece.

Cordia, L., is heterostyled, but the stamens are of almost the
same length and the pollen-grains are of the same size in the
flowers of both forms (Darwin, 167).

Tribe Boragee.

300. SYMPHYTUM OFFICINALE, L.—A white, annular ridge at

the base of the ovary secretes honey, which is lodged in the upper
part of the inverted corolla. The whole corolla is 14 mm., its
upper narrower portion 8 mm.,long. The long, trihedral invagina-

tions of the corolla, which pass from the boundary between the

wide and narrow parts into the wide part of the bell, closing in the
spaces between the stamens, were thought by Sprengel to guard

the nectar from rain; but as in the preceding species, this service”
is performed by the inverted position of the corolla. Their use is”

probably to cause an insect to thrust its proboscis between the

closely approximated anthers, and not into the wide intervals be-—
tween the stamens. The sharp teeth which these appendages of —
the corolla bear aid in this object; they certainly do not act as —
“pathfinders,” as Sprengel thought, for to an insect inserting its —

head into the flower from below, they appear not bright and

shining, as Sprengel describes them, but as dark points, guarding ~

all but the legitimate access to the honey. This view is confirmed

by a comparison of the lengths of the proboscides of insects which ~
reach the honey of this flower in the normal way, and of those —
which do so by biting a hole in the narrow part of the corolla. To

?

reach the honey by passing between the anthers an insect requires —

a proboscis at least 11 mm. long; to reach it by passing between

i
J

ie ART III. | THE MECHANISMS OF FLOWERS. 409

the filaments from the interior of the corolla would require a
‘proboscis only 8 mm. long. Now I have found the following

mr. ° (183—15); B. Rajellus, Ill. 2 ¥ (11—13); Anthophora
| pilipes, F. 2 (20—21); the following, on the other hand, only
/ Beach the honey from outside by boring a hole in the narrow

Balaments remained unguarded, the ginée last-named insects might
all have made use of it, without resorting to the slower process of
‘piercing the corolla, and there can be ,no doubt that they are
_ deterred by the sharp teeth of the corolline appendages.
' The anthers, which, as in Borago, combine to form an inverted:
cone, dehisce before the flower opens; the pollen remains partly
_ within the anthers, partly in the apex of the cone, until a humble-
_ bee or Rhingia thrusts its proboscis between the anthers and lets
_ the pollen fall out. Each pollen-grain is 0°02 mm. long, about
-0°013 mm. broad, and is shaped like two spheres joined together
and flattened at the junction ; on being moistened with water, each
pollen-grain swells into a sphere of 0°02 mm. diameter. The pollen
asit falls out resolves itself for the most part into single grains, only
a few of which remain adhering in groups; a considerable amount
remains attached to the anther-walls until the flower withers.

The stigma ripens as soon as the flower opens, and hangs down
_ beyond the anther-cone; an insect-visitor therefore touches the
_ stigma before it displaces the anthers and dusts itself with pollen.
In absence of insects, self-fertilisation probably takes place.

}
5)
é
€

}
*
4 Visitors: A. Hymenoptera—Apide : (1) Anthophora pilipes, F. 9! (2)
' Bombus agrorum, F. 9!; (3) B. silvarum, L. ? $!; (4) B. Rajellus, Il.
| ©9%!; (5) B. terrestris, L. 9; (6) B. pratorum, L. §; (7) B. lapidarius, L.
_ %, the last three gnaw through the narrow part of the tube ; (8) Eucera longi-
—cornis, L. ¢, creeps bodily into the flower ; (9) Halictus sexnotatus, K. 9 ;
(10) Apis mellifica, L. %, both suck through the holes made by humble-bees.
B. Diptera—Sy pephiddee 3 (11) Rhingia rostrata, L., s.! Only those insects
marked with (!) suck normally and effect cross-fertilisation. C. Coleoptera—
Nitidulide : (12) Meligethes. See also No. 590, 11.

| 301. BoRAGo OFFICINALIS, L.—The mechanism of this flower
was minutely described by Sprengel, with great but not absolute
accuracy. Honey i is secreted by the pale-yellow, fleshy base of the
ovary, and is lodged in a short tube formed by the bases of the

410 THE FERTILISATION OF FLOWERS. [PART III.

stamens ; it is protected from rain by the inverted position of the
flower. The anthers meet to forma cone; each dehisces on its inner
surface, slowly from apex to base, letting the smooth pulverulent
pollen run into the apex of the cone. The style with still imma-
ture stigmas is inclosed within the cone of anthers. An insect, to
reach the honey,must hang suspended below the flower, and thrust its
proboscis between two stamens ; two anthers are thus slightly dis-
placed, the point of the cone opens, and a little pollen falls out.

i)

Fie. 186.—Borago officinalis, L.

1.—Flower, from below ; the stamens have been cut away.

2.—A stamen in its natural position, viewed from the side.

a, pouch in the corolla; b, cut end of stamen; c, ovary; d, fleshily thickened filament; e, pro-
cess of ditto; f, orifice of the anther.

The pollen in each anther ripens very gradually from the apex
towards the base, and hence the little shower of pollen may be
emitted repeatedly. The style only grows out beyond the cone
of anthers and develops its stigma, after the anthers have been
emptied of their pollen. Even after repeated insect-visits a per-
manent displacement of the anthers cannot take place, for the
short, broad form and fleshy nature of the filaments (d, 2), their
stiff external appendages (ec, 2),! and the invaginated processes of
the corolla that surround the base of the anther-cone, insure the
return of each anther to its place after every disturbance. I have
neglected to observe whether finally, in absence of insects,
self-fertilisation may take place.

1 Sprengel thought that these appendnay were for the purpose of sheltering the

honey, but the inverted position of the flower renders this unnecessary. Delpino
(No. 178, pp. 172-174) takes the view that I have adopted.

—————

PART III. | THE MECHANISMS OF FLOWERS. 411

(1) Apis mellifica, L. $, very ab., s. and c.p.; (2) Bombus pratorum, L. ?,
s. and c.p. ; (3) Halictus zonulus, Sm. ?, s.; (4) H. sexnotatus, K. 9, s., ab. ;
(5) Megachile centuncularis, L. ¢,s. See also No. 590, 111.

302. ANCHUSA OFFICINALIS, L. (Sprengel, Pl. 111., 10,11, 16,17).
—Honey is secreted by the green fleshy base of the ovary and
accumulates in the lower part of the corolla, which forms a tube
7 mm. long. The corolla is smooth within, but its entrance is
guarded from rain and from unbidden guests (flies) by five closely
approximated, hairy, invaginated processes. At its upper end the
tube expands into a limb 10 mm. in diameter, at first concave and
violet in colour, then flat and deep-blue; and further, the flowers,
which are conspicuous in themselves, are rendered more so by
aggregation, The invaginated appendages, which are indicated
on the outside of the corolla by transverse slits, serve by their
white colour as honey-guides. The anthers, which dehisce in-
trorsely, and the stigma which overtops them, are matured simul-
taneously. Cross-fertilisation is insured, in case of insect-visits, by
the position of the stigma; in absence of insects, self-fertilisation
must finally occur, for the corolla in falling off brings the anthers
in contact with the stigma.

Eug. Warming has found A. officinalis heterostyled, with
transition-forms between the long- and short-styled flowers (762).

Insect-visits are plentiful, and in fine weather cross-fertilisation
always occurs. On September 13, 1871, I observed the following
insects visiting this plant on the Wandersleber Schlossberg in
Thuringia :—

A. Hymenoptera—A pide : (1) Apis mellifica, L. $,s. and c.p., ab.; (2)
Bombus pratorum, L. §, 8. and c.p. ; (3) B. agrorum, F. ¢ 9 ; (4) B. silvarum,
L. ¢; (5) B. lapidarius, L. ¢ §; (6) B. muscorum, F. § ; the last four only
sucking. B. Lepidoptera—Nociue: (7) Plusia gamma, L., very ab., s. See
also No. 590, 111., and No. 609.

303. Lycopsis ARVENSIS, L.—The same parts of the flower as
in Anchusa serve to secrete, contain, shelter, and point out the
honey. The flowers are doubtless visited and fertilised in like
manner, chiefly by bees, and to some extent also by Lepidoptera.
I have only observed (September 8, 1871, in Thuringia) Hesperia
thaumas, Hufn., once sucking honey on this plant.

Pulmonaria angustifolia, L. (P. azwrea, Besser).1—This plant is
dimorphic ; and the two forms of flowers, besides differences in the
reproductive organs, show an unusual number of other minor

1 Darwin (No. 167) has taken P. angustifolia, L., and P. azurea, Besser, to be
distinct species.

412 THE FERTILISATION OF FLOWERS. [PART III.

differences. In the short-styled flowers, the calyx is longer and
narrower, the corolla is longer and has a much larger and more con-
spicuous limb; the ovary is smaller; the nectaries larger and more
rich in honey than in the long-styled flower. In the Alps humble-
bees and Rhingia and Bombylius act as cross-fertilising agents
for this species, as they do for P. officinalis in the Lowlands (609).
Hildebrand denies that this plant is heterostyled: it is possible
that he made his observations on cultivated examples, and that

Fic. 137.—Pulmonaria angustifolia, L .

A.—Long-styled flower.

B.—Ditto, in section.

C.—Ditto. ov, ovary; n, nectary; gr, style (x 43).

D.—Short-styled flower.

E.—Ditto, in section (x 14).

F.—Ditto (x 43).

.—Limb of the corolla of a short-styled flower, cut off close above the anthers, to show the
protecting hairs (x 49).

Q

there is in them, as Darwin has shown in the case of Primula
sinensis, a return to the homostylic condition (609).

Darwin found the long-styled though not the short-styled
flowers of this species absolutely barren when illegitimately fer-
tilised ; he gives several reasons for considering that this dimorphic
plant is in a transition-stage, tending to become dicecious (167).

304. PULMONARIA OFFICINALIS, L.—This species also is di-
morphic. Honey is secreted by the white, basal part of the ovary,
lodged in the lower portion of the tubular corolla, and sheltered
from rain by a ring of hairs placed in the tube at the place where
it widens out. In the short-styled flowers, the anthers stand at
the mouth of the corolla (whose tube is 10 to 12 mm. long); the
stigma stands half-way up the tube, on astyle 5 to 6 mm. long: in
the long-styled flowers these positions are reversed, the style being
10 mm. long, and the anthers, being attached by very short fila-
ments to the corolla, 5 mm. from the base of the flower. Since the
corolla widens slightly at its mouth, insects with a proboscis 8 mm,

PART III. | THE MECHANISMS OF FLOWERS. 413

long are able to reach the honey. Bees touch the longer reproduc-
tive organs with their heads or with the base of their proboscides,
and the shorter with the maxillz, which serve to sheath the pro-
boscis ; thus they regularly perform ‘legitimate cross-fertilisation,’
The flowers are very conspicuous and very rich in honey, and
appear at a season when they have few rivals; they are therefore
very much visited by insects, and have become sterile when
fertilised with their own pollen or with pollen from another flower
of the same form. Hildebrand (342) found by experiment that
when he fertilised a flower of either form with its own pollen, or
with pollen from another similar flower, it was completely sterile ;
but when fertilised with pollen from a flower of the other form, it
was as productive as in the wild state. He found on investigating
wild plants in fruit, that in some cases the oldest flowers on the
plant, and almost constantly the terminal flowers of each shoot, bore
no seed; the former fact he explains by the absence of the proper
insects early in the season, the latter by imperfect nourishment of
the terminal parts of the shoots.

Darwin’s experiments (No. 164, p. 103) on this plant led to a
result: different from Hildebrand’s. He found that illegitimately
fertilised long-styled plants were highly fertile, producing three
times as much seed as Hildebrand’s wild specimens bore; and that
even when self-fertilised, a few seeds were produced. Hildebrand
endeavoured to explain this great discordance by the fact that the
plants which he experimented on were kept in pots in the house,
while Darwin’s were grown out of doors.

Visitors: A. Hymenoptera—Apide: (1) Anthophora pilipes, F. ¢ 9
(19—21), very ab., s. andc.p., sucking now on Primula elatior, now on Cory-
dalis, now on Pulmonaria, without restricting itself long to the same species ;

- (2) Bombus hortorum, L. ? (21), very ab., s., and keeping to the same species

of flower ; (3) B. lapidarius, L. 9 (12—14), s. ; (4) B. senilis, Sm. 9 (14—15),s. ;
(5) B. agrorum, F. 9 (12—15), ab., s. ; (6) B. silvarum, L. 9 (12—14), s.; (7)
B. Rajellus, Ill. 9 (12—13), s. ; (8) B. terrestris, L. 9 (7—9), s.; (9) B. pra-
torum, L, 2 (11—12), s., distinctly prefers Pulmonaria, leaving the flowers of
Primula elatior untouched ; (10) Osmia fusca, Christ. (bicolor, Schrank) ? ¢
(8), c.p. and s.,ab. This species feeds itself and its young almost entirely on
the honey and pollen of Pulmonaria. I have never found its nests (which
are made in snail-shells, those of Helix nemoralis at Lippstadt) except where
Pulmonaria was growing plentifully. (11) O. pilicornis,Sm. ¢ 9,s.andep. I
was the first to find this bee on the continent of Europe. I have found it ex-
clusively on flowers of Pulmonaria, at Rixbeck near Lippstadt ; it occurs singly
among numerous examples of the foregoing species, with which it agrees in the
manner of tending its young. (12) O. rufa, L. ¢ (7—8),s. In most of these
bees I have directly observed pollen upon the maxilla. B. Diptera—(a)

414 THE FERTILISATION OF FLOWERS. [PART III.

Bombylide : (13) Andrena Gwynana, K. 9, «ep. ; (14) Anthophora retusa,
K. 9, cp. and s.; (15) Halictus cylindricus, F. 9, cp. ; (16) Bombylius
discolor, Mgn. (11—12), hovers over the flower and inserts its proboscis with-
out settling, ab., but only in warm sunshine; (17) B. major, L. (10), do.;
(6) Syrphide : (18) Rhingia rostrata, L. (11—12), very ab., s., but only towards
the end of the flowering period (May 18, 1870). C. Lepidoptera—Rhopalocera :
(19) Rhodocera rhamni, L., s.,ab. D. Coleoptera—Staphylinide : (20) Omalium
florale, Pk., ab., creeping about in the flowers.

305. MyosoTis sItvaticA (Hoffm.) Lehm.—As soon as the
flower opens, the anthers, which are attached to the corolla above
the level of the stigma and are inclined slightly inwards, dehisce

Fic, 138.—Myosotis silvatica, Hoffm,

1.—Flower, from above.

2.—-Ditto, in section (x 7).

83.—Pollen grains.

a, light-blue limb of corolla ; b, white radiating bands ; c, yellow centre of the corolla; d, stamen ;
é, stigma; f, nectary.

longitudinally, and become covered on their inner surfaces with
small, white pollen-grains; each of the latter is shaped like two
attached spheres, and measures ‘005 mm. by ‘003mm. The stigma
ripens simultaneously with the anthers. In sunny weather nume-
rous flies frequent the flowers, which are rendered conspicuous by
colour and by aggregation. The fly thrusts its proboscis rapidly
into the flower, spending at most two to three seconds upon it,
and probably, therefore, sucking honey in each case, not gathering
pollen.

The honey is secreted by the fleshy base of the ovary, and is
lodged in the lower part of the tube of the corolla, which is 2 to
3 mm. long. An insect must dip its proboscis down between
the stigma and anthers, and touch them with opposite sides of the

PART III. | THE MECHANISMS OF FLOWERS. 415

proboscis, Since the proboscis may be inserted on any side of the
stigma, the part of the proboscis dusted with pollen in one flower
will very probably come in contact with the stigma in the next.
Since flies often dip their proboscis repeatedly into one flower, self-
fertilisation also must frequently result. In absence of insects,
self-fertilisation always occurs by pollen falling directly upon the
stigma. In plants which I kept in my room, guarded from insects,
I always found the stigma in the older flowers thickly covered with
pollen. Axell found on experiment that the plant is completely
fertile when self-fertilised (17).

Delpino describes Myosotis as dichogamous and exclusively
fertilised by bees.

M. silvatica in my garden is visited by the following insects :—

A. Hymenoptera—Apide@ ; (1) Andrena albicans, K. 9, s. B. Diptera—
(a) Syrphide : (2) Eristalis arbustorum, L., ab. ; (3) E. sepulcralis, L., ab. ;
(4) Syritta pipiens, L., very ab. ; (5) Rhingia rostrata, L. ; (6) Muscide : (6)
Scatophaga merdaria, F. ; (7) Species of Echinomyia ; (8) Onesia floralis, R. D. ;
(9) O. sepulcralis, Mgn. ; (10) Pollenia vespillo, F. ; (11) Musca corvina, F. ;
(12) Colobata cothurnata, Pz. ; all acting in the manner described above. A
list of nineteen additional visitors is given in No. 590, 111.

Myposotis alpestris, Schmidt.—I have observed this plant visited
on the Alps by thirty-three Lepidoptera, nineteen Diptera, and
one bee—a strikingly different list from the preceding one (609).

306. Myosoris INTERMEDIA, Link. ap. Schl.—The flowers of
this plant differ from those of 1. silvatica in their smaller size, and

Fic. 139.—Myosotis intermedia, Link.

1.—Longitudinal section (x 7).
2.—Anther viewed from the side to show the broad prolongation of the connective.

in two points which make cross-fertilisation still more sure : (1) The
_ stigma stands on a level with the anthers, so that an insect’s

| proboscis is more certain than in M. silvatica to touch anthers and

_ stigma with opposite sides, unless it be repeatedly inserted as is not

416 THE FERTILISATION OF FLOWERS. [PART III.

rarely the case. (2) The connective terminates above in a broad
expansion, which is slightly curved outwards, but stands immediately
above the anther since the latter is inclined towards the centre of
the flower ; this arrangement hinders the proboscis from coming in
contact with the anther while being inserted. The same character
is present but much less marked in ©. silvatica.

Self-fertilisation always occurs in absence of insects.

The invaginated processes of the corolla which surround the
-mouth of the tube in all species of Myosotis serve to shelter the
honey from rain, and by their yellow colour serve as “path-
finders”; they also cause insects to insert their tongues in the
centre of the flower and so to come more directly in contact with
the stigma.

Visitors : A. Hymenoptera—Apide : (1) Apis mellifica, L. $, ab., s. ; (2)
Andrena fasciata, Wesm. ¢, s.; (8) A. albicans, K. 9,8. B. Diptera—(a)
Bombylide: (4) Bombylius major, L. s.; (b) Syrphide: (5) Chrysogaster
viduata, L.,s. See also No. 590,111.

307. MyosorTis PALUSTRIS, Rth., agrees in all points with JZ,
intermedia, except in the length of its tube, which is 3 mm. long.

Visitors: A. Lepidoptera—Rhopalocera: (1) Lycena icarus, Rott., s. B.
Diptera—Empide : (2) Empis opaca, F., very ab., s.

308. MyYosoris HISPIDA, Schlecht.—The flower is described in
No. 590, Ill. :

Visitors: <A. Hymenoptera—A pide: (1) Halictus zonulus, Sm. 9, s.
(Tekl. B.). B. Diptera—Muscide: (2) Anthomyia sp., s.

Myposotis versicolor, Lehm.—When the flower opens, the corolla
is colourless or pale yellow, and imperfectly developed ; the anthers
and stigma are however ripe, and the latter protrudes a little from
the flower. If insect-visits now occur, cross-fertilisation results;
afterwards the corolla in elongating rubs the anthers against the
knobbed stigma and the flower is self-fertilised.

I have observed bees and flies visiting the flower (570, vol. x.)

Echinospermum Lappula, Lehm.—The mechanism of fertilisation
resembles that of Myosotis silvatica, but the honey is not so acces-
sible, as the limb of the corolla does not spread out flat, but remains
bell-shaped. The corolla is white while in the bud, pale red while
just emerging beyond the calyx, and afterwards bright blue, The
flower is visited by Diptera, Apidew, and Sphegide (590, IL. ; 609).

Omphalodes verna, Meench.—The tube is 3 mm, long, and the

PART IIL] THE MECHANISMS OF FLOWERS. | 417.

bright blue limb of the corolla expands to a diameter of 15 to 18
mm. The connective has no terminal appendage ; otherwise the
flower resembles that of Myosotis, and self-fertilisation is likewise a
regular occurrence.

Visitors : Hymenoptera—Apide: (1) Bombus terrestris, L. 9, s. ; (2)
Osmia rufa, L. ¢, s.°

309. LITHOSPERMUM ARVENSE, L.—The smooth ovary secretes
a small amount of honey, which lies in the base of the corolla; the
latter forms a tube 4 to 5 mm, long, and only 1 mm. wide in its
lowest part.. The five short stamens are inserted upon the corolla
below its middle, and their anthers dehisce inwards longitudinally

Fic. 140.—Lithospermum arvense, L.

1.—Tip of style, from a bud (x 36). st, stigma,
2.—Position of essential organs in the flower.

and let their pollen escape, before the opening of the flower. The
_ style, which is 2 mm. long, ends in two smooth, rounded lobes, and
_ bears immediately below these an annular ridge covered with stig-
| matic papille ; this stands on a level with the anthers, completely

filling up the narrow passage to the base of the flower. The upper
_ ends of the stamens curve slightly outwards, thus guiding an insect’s
_ proboscis to the centre of the flower and causing e to pass between
_ the anthers and stigma. Ifin the young flower an insect thrusts in
_ its proboscis, already dusted with pollen, cross-fertilisation takes
place, and the proboscis gets dusted at the same time with fresh
pollen. But as the pollen issues more and more from the anthers,
e -cross-fertilisation is soon rendered more difficult, and ultimately
_ self-fertilisation becomes unavoidable.

418 THE FERTILISATION OF FLOWERS. [PART III.

The regular occurrence of self-fertilisation is accounted for by
the small, solitary, white flowers, and the scantiness of insect-visits
that this want of conspicuousness leads to. I, like Sprengel also,
have observed Pieris brassice, L., and P. rape, L., visiting the
flowers ; after once resorting to the plant they came frequently.
Bees and Syrphide also visit the plant (590, IT.).

Lithospermum canescens, Lehm.—The flowers either are
heterostyled or are very variable (167),

Batschia (Iithospermum) longifiorum, Pursh., has cleistogamic
flowers (167).

310. EcHIUM VULGARE, L.—The flowers ‘of this plant are
very conspicuous, and are peculiar in causing insects of very

Fic. 141.—Echium vulgare, L

1.—Older flower, from the side. The flower should be represented horizontal.
2.—Transverse section through the base of a flower, niore magnified.
k, sepal; bl, corolla; st, stamen; g, style; n, stigma; h, entrance to the honey.

various sizes to perform cross-fertilisation, both in reaching the
honey and in carrying off the pollen.

The honey, which attracts most visitors, is secreted by the fleshy
base of the ovary, and lies in the base of the five-toothed, funnel-
shaped corolla. The narrow end of the tube is inclined obliquely
upwards, and the expanded bases of the five stamens adhere
to its inner wall for a distance of 4 mm. When the stamens
become free from the expanded corolla, the latter suddenly widens
out, and its superior wall extends obliquely upwards for about
12 mm. farther; the sides, slightly diverging, extend for 9 mm. ;
and the inferior wall extends for 6 mm., lying horizontally and
curving slightly downwards near the mouth. The corolla is large

PART ILI. | THE MECHANISMS OF FLOWERS. 419

enough for large humble-bees to insert easily the head and part of
the thorax, and smaller humble-bees more than half of their body ;
while still smaller bees can enter the tube bodily. The insect
passes straight on to the base of the flower, the downward curva-
_ ture of whose terminal portion corresponds to that of the insect’s
proboscis, To alight on the flower and suck the honey is the work
of a moment; so completely is the shape of the flower adapted,
not for one only, but for many species of bees, But none of the
various visitors can reach the honey without getting dusted ven-
trally with pollen in young flowers, or leaving some of that pollen
upon the stigma in older flowers, From the point where the
filaments become free from the corolla, they pass on horizontally’
near the inferior wall of the corolla; and the four lowest stamens
project some 7 mm. beyond the corolla, forming a convenient
_ alighting-place for insects. The uppermost stamen, on leaving its
_ attachment to-the corolla, also bends downwards, and in so doing
it divides the entrance to the honey-containing part of the tube
_ into two passages ; it then proceeds horizontally, but only so far as
the mouth of the corolla. The free ends of all the stamens curve
slightly upwards; and the anthers, which dehisce as the flower
. opens, turn their pollen-covered sides upwards ; no bee, therefore,
can alight without dusting its ventral surface with pollen. Large
' humble-bees bring their thorax, smaller ones their abdomen, in
contact with the long stamens, while the smallest bees, which fly
| right into the flower, must at least come in contact ventrally with —
| the short fifth stamen. The style lies in the midst of the stamens,
and divides terminally into two short branches, which bear the
stigmas at their ends. When the flower opens, the style scarcely
' reaches the mouth of the corolla; its distal end is straight, its two
branches lie close together, and their stigmas are apparently in-
capable of fertilisation. In course of time the style lengthens till
| it projects 10 mm. beyond the mouth of the corolla; it curves
' gently upwards at its outer end, and its two branches, now
| bearing ripe stigmas, separate. The stigmas now lie above
} and in front of all the anthers, and no bee, large or small, can
/ enter the flower without bringing its ventral surface in contact
: with them.
| It is evident from the position of the stigmas that cross-
| fertilisation will be performed, even if pollen remains upon the
| anthers when the stigmas are mature.
i Echium attracts very numerous and various insects, as the
| following long list shows :-—
| EE 2

420 THE FERTILISATION OF FLOWERS. [PART III,

A. Hymenoptera—(a) Apide: (1) Apis mellifica, L. 9, very ab., s. ; (2)
Bombus silvarum, L. ? %,s. and sometimes also c.p. ; (3) B. lapidarius, L.
286; (4) B. agrorum, F. 9 $; (5) B. hortorum, L. 9 $ ¢; (6) B. terrestris,
L. 2 ¢; (7) B. muscorum, F. §; (8) B. pratorum, L. 9; (9) B. Rajellus, Il.
®; (10) B. hypnorum, L. $; (11) B. (Apathus) rupestris, F. 9; (12) B. ves-
talis, Fourc. 2; (13) B. campestris, Pz. 9 ¢; (14) B. Barbutellus, K. 9; all
these thirteen species of humble-bees are more or less abundant, especially the
first five, all only suck, except B. silvarum ; (15) Anthophora quadrimaculata,
F. 9 ¢ (Thur.),s. and c.p., ab. ; (16) A. furcata, Pz. 2 ¢ (Thur.), s. and cp. ;
(17) Saropoda bimaculata, Pz. 2 ¢, very ab., s.; (18) Melecta luctuosa, Scop.
? (Thur.) ; (19) Eucera longicornis, L. ¢; (20) Andrena fulvicrus, K. ¢;
(21) A. albicrus, K. ¢; (22) <A. labialis, K. ¢5; (23) Halictus nitidus,
Schenck, 2; (24) H. albipes, F. ¢; (25) H. cylindricus, F. 9 ¢; (6) H

‘sexnotatus, K. 2 ; Nos. 18—25 alls. ; (27) H. nitidiusculus, K. 9, c.p. ;. (28)

Nomada sexfasciata, Pz. 9, s.; (29) Ceratina coerulea, Vill. 2, s.; (30)
Megachile Willughbiella, K. ¢,s. ; (81) M. circumcincta, K. 9,8. and cp. ;
(32) Diphysis serratule, Pz. 9 ¢, s. and e.p., very ab.; (33) Osmia fusca,
Christ. (bicolor, Schrank) 9, s. and c.p. ; (34) O. enea, L. 9 6 ,s.and ep. ; (35)
O. ceementaria, Gerst. 9 ¢,¢.p. and s., very abundant in Thuringia and Sena
land, building its nests in the cavities of stones, and feeding the young exclusively
on honey and pollen of Echium ; (36) O. adunca, Latr. 2 ¢, very ab., also
feeding its young exclusively on honey and pollen of Echium ; (37) O. leu-
comelena, K. 9, cp. ; (38) O. rufa, L. 9, 8.; (89) Coelioxys quadridentata,
L. ot conica, L.) 9 ¢,8., ab. ; (40) C. conoidea, Ill. (punctata, Lep.), 2, s. ;
(41) C. simplex, Nyl. 9, s.; (42) C. umbrina, Sm. 9,5s., (43) Chelostoma
nigricorne, Nyl. ¢ 2,8. ; (44) Stelis pheoptera, K. 2, 8. ; (45) St. breviuscula,
N. ¢, s.; (46) Prosopis hyalinata, Sm. 9, s.; (b) Sphegide: (47) Crabro
patellatus, v. d. L. 9 ¢; (48) Ammophila sabulosa, L. 2; (49) Psammophila
affinis, K. 9, all three s.; (c) Vespidw: (50) Odynerus parietum, L. ¢, s. ;
(d) Chryside: (51) Cleptes semiaurata, F., s. ; all the short-lipped Hymeno-
ptera creep bodily into the flower to reach the honey. B. Diptera—(a) Syrphide :
(52) Rhingia rostrata, L., s.; (53) Helophilus trivittatus, F., fp. ; (64) Syrphus__
pyrastri, L., fip.; (55) S. arcuatus, Fall., fp. ; (56) Melanostoma ambigua,
Fall., fp. ; (b) Conopide : (57) Physocephala vittata, F.,s. C. Lepidoptera— —
(a) Rhopalocera: (58) Satyrus Janira, L.; (59) Pieris brassice, L.; (60).
Lyczena sp.; (61) Hesperia sylvanus, Esp. ; (62) Colias hyale, L. (Thur.) ;—
(63) Meliteea cinxia, L.; (b) Sphinges: (64) Zygena lonicere, Esp. (Thur.) 5
(65) Macroglossa stellatarum, L. ; (c) Noctue: (66) Plusia gamma, L., ab., all
sucking. D, Coleoptera—(67) Cidemera virescens, L., crept far into the flower,
and seemed to reach the honey. A further list of visitors in Low Germany is
given in No. 590, 1. A list of Alpine visitors (seventeen bees, five Lepido-
ptera) is given in No. 609, p. 262.

A review of this long list of insects, many of which frequent the —
flowers of Echium in great numbers, shows that the great majority _
come seeking honey, and only use the stamens. as a landing-place. —
The females of bees with abdominal collecting-brushes, without
any special effort, sweep up pollen with their abdominal brushes,
filling them after a few visits. The flower is thus so convenient

PART III. | THE MECHANISMS OF FLOWERS. 421

for them that several of these bees (Osmia adunca and O. cemen-
taria) resort to it exclusively, both for their own food and for that
of their larvae. Syrphide also make frequent use of the pollen,
while bees with tibial or femoral collecting-baskets seldom gather
it, and all other insects come solely for the sake of honey. The
power of self-fertilisation has been completely lost.

This plant is gynodicecious. The female flowers differ from the
hermaphrodite in having a much smaller corolla and shorter pistil ;
their stamens are short, and the anthers contain no sound pollen-
grains (Darwin, 167).

Cerinthe glabra, Mill. (C. alpina, Kit.)—This flower is adapted
for humble-bees. Only humble-bees or other large bees can cling

Fic. 142.—Cerinthe glabra, Mill.

A.—Flower that has recently expanded.

B.—Ditto, in section (x 4).

C.—Older, fully expanded flower (x 7).

8. Sepal; co, corolla; n, nectary; ov ovary; gr, style; ji, filament.
(Falo Alp, July 28, 1877).:

| to the recurved teeth of the corolla, and hanging beneath the
flower, suck the honey from its base. In doing this the insect
_ first brings its head in contact with the stigma, and then, touching
_ the anthers with its proboscis, it dusts its head with new pollen.
| LT have only found humble-bees (Bombus alticola, ? 9), but those in

422 THE FERTILISATION OF FLOWERS. [PART III.

great numbers, on this flower (Alpenblumen, p. 264; named there
by mistake C. major).

Cerinthe minor, L., has a somewhat different structure, and is
visited and fertilised by the honey-bee as well as by humble-bees
(590, IIL.)

According to Kuhn, Lritrichium, Amsinckia, Lithospermum,
Pulmonaria, Arnebia, and Hockinia, contain dimorphic species
(399). Darwin considers that Amsinckia and Arnebia are not
dimorphic, but merely show extreme variability in the length of
their stamens and style (167).

Mertensia, Roth., is dimorphic according to Darwin (167).

REVIEW OF THE BORAGINE.

The Boraginez have inherited from common ancestors a short
tube which, to a certain degree, conceals their honey.

The lower forms (Asperugo, Echinospermum, Omphalodes,
Myosotis) are visited and cross-fertilised by flies (especially Syr-
phide), bees, and Lepidoptera, and are adorned with red, violet, and
blue colours through the selective taste of their guests. Many species,
in the course of individual development, seem to recapitulate to us
the evolution of their colours—white, rosy, blue in several species
of Myosotis; yellow, bluish, violet in JZ. versicolor ; and red, violet,
blue in Pulmonaria, Echium, etc. Here, white and yellow seem
to have been the primitive colours; and, at least in many cases,
violet and blue seem to have been preceded by red—an assump-
tion which is strengthened by the fact that many blue and violet
species (Myosotis, Anchusa, Symphytum) give us white and rose-
red varieties, apparently by reversion to more primitive characters.

Starting from these simpler forms, we meet with many ad-
vancing adaptations for fertilisation by bees. Pulmonaria, simply
by the length of its tube, protects its honey from the great majority
of insects, excepting humble-bees, and insures cross-fertilisation, in
the event of humble-bees visiting it, by the distinct heterostylic
condition, Anchusa reserves its honey for bees still more effectually
by the narrow entrance to its tube ; and according to Warming, it
shows locally a tendency (never completely attained) to become
heterostyled. Echium, without excluding other guests, has so
adapted the form of its flowers for the convenience of bees, that
many species visit it in great numbers; and it insures cross-
fertilisation by proterandry and by the prominent position of the

PART III. | THE MECHANISMS OF FLOWERS. 423

mature stigma, The drooping flowers of Borago, and the position
of their anthers, exclude all insects which cannot hang, as bees
can, below the flower and insert their proboscides into the narrow
opening. Symphytum and Cerinthe, finally, besides offering the
same difficulties as Borago, have a tube which requires so long a
proboscis to reach its base, that only humble-bees and other bees
with a proboscis equally long can reach the honey.

Orv. CONVOLVULACE ZZ.

311. CONVOLVULUS ARVENSIS, L.—Sprengel has described the
chief characters of this flower very clearly, contrasting them with
those of C. sepiwm.

The funnel-shaped corolla is yellow at the base internally,
elsewhere either white or red, and marked in the latter case with

Fic. 143.—Convolvulus arvensis, L.

1.—Transverse section, through the base of the flower (x 7).
2.—Essential organs, from an expanded flower (x 33).
a, style; b, filament; ¢, entrance to nectary; d, corolla; e, calyx.

five radiating white streaks. These “pathfinders,’ and the habit
of closing, both in the evening and in rainy weather, mark out the
flower as adapted for the visits of diurnal insects. The orange-red
under surface of the ovary secretes honey, which is lodged in the
lowest, narrowest part of the corolla, and sheltered by tbe broad
bases of the stamens, which leave five narrow openings leading to
it. The stamens arising thus with broad bases from the corolla,
adhere to it for a short distance, and then curve inwards, coming
close together around the style; the filaments, where they are in
contact with one another, are closely beset with small, stiff pro-
jections, which prevent an insect from thrusting its proboscis

424 THE FERTILISATION OF FLOWERS. [PART ITI.

between them. The five narrow slits between the stamens, near
their base, are thus the only means of access to the honey, and the
insect must make its way into the funnel between the corolla and
the stamens, and then insert its proboscis into one of the slits.
Since the stamens dehisce extrorsely, an insect acting in this way,
unless it be too small, must be dusted with pollen; and the two |
branches of the stigma, standing well above the anthers, and
stretching outwards over them, are touched before the anthers by
the insect. In absence of insects, self-fertilisation can easily occur ;
for if the flower hangs down, or if the corolla withers and falls off,
the pollen readily falls upon the stigma, and even in erect and
fresh flowers, one of the stamens is not. unfrequently seen, still
covered with pollen, in contact with the stigmatic papille. The
flowers have a peculiar aromatic smell, which seems the only reason
for their being visited so much more plentifully than the larger
flowers of C. sepiwm. ,
Visitors : A. Hymenoptera—Apide : (1) Apis mellifica, L. $, very ab., s.
and ¢.p.,—to suck, it creeps down into the base of the flower, dusting its head
and back with pollen, which parts come first in contact with the stigma in each
flower ; (2) Halictus morio, F. ¢, s., touching neither stigma nor anthers ; (3)
H. villosulus, K. 2; (4) H. longulus,Sm. 9; (5) H. nitidiusculus, K. 9, all
three c.p. ; they usually alight on the stigma and then proceed to the anthers,
thus effecting cross-fertilisation ; (6) Chelostoma campanularum, K. ¢, s., like
No. 2. B. Diptera—(a) Empide : (7) Empis livida, L., very ab., s., thrusting
its proboscis into each of the five nectaries one after another ; (6) Syrphide :
(8) Helophilus floreus, L., s. and fp.; (9) Eristalis arbustorum, L., s. and f.p.,
takes shelter from rain in the flowers ; (10) Syrphus nitidicollis, Mgn. ; (11)
S. balteatus, Deg. ; (12) Melithreptus scriptus, L. ; (13) M. teeniatus, Mgn., all
four f.p.,—the large honey-sucking flies effect cross-fertilisation in the same way
as No. 1, the smaller pollen-feeding flies do so after the manner of Nos. 3—5 ; (ce)
Muscide : (14) Sepsis, abundant in the passages leading to the honey. ©. Coleo-
ptera—(a) Nitidulide : (15) Meligethes, do. ; (b) Gidemeride : (16) Gidemera
virescens, L., fp.; (¢) Cerambycide: (17) Leptura livida, L., feeding on
pollen, and on the anthers. D. Hemiptera—(18) Nabis, s. Eighteen
additional visitors are enumerated in No. 590, II.

Calystegia sepium, R. Br. (Convolvulus sepiwm, L.)—The flowers
are scentless and without “pathfinders.’ In spite of their large
size and conspicuous white colour, they are only scantily visited
by insects. They remain open in rain. On dark evenings (be-
tween 8 and 10) I have found all the flowers closed, but all open
on moonlight nights. In other respects the flowers are similar
to those of Convolvulus arvensis. I have never observed crepus-
‘cular or nocturnal insects on the flowers, but several of my pupils
have caught numbers of Sphinw convolvuli upon them in the

PART IIT. | THE MECHANISMS OF FLOWERS. 425

evening. In the daytime I have sometimes seen Halictus cylind-
ricus, K. 3, and Megachile centuncularis, L. g, and Hmpis and
_ Rhingia in special numbers, all creeping into the base of the
flower, and inserting their proboscides through the slits between
- the filaments. Rhingia rostrata, L., applies its labelle fre-
_ quently to the anthers, stigma, and inner wall of the corolla,
apparently picking up scattered pollen. Meligethes, Thrips, and
minute Podure also frequent the flowers during the day.

Delpino mentions Sphinx convolvuli as a fertiliser of C. sepium
(172, 352); he tells me by letter that one of his friends catches
this insect in numbers, standing by a hedge overgrown with the
plant, holding thumb and forefinger over a flower and closing its
orifice when the insect has entered !

In England, where Sphinx convolvuli is rare, C. sepiwm seldom
produces seed ; in Scotland, where S. convolvuli seems not to occur,
C. sepium is rarely found wild (773). In the north of Ireland,
according to Mr. T. H. Corry, C. sepiwm is far commoner than
C. arvensis, and Sphinx convolvuli is comparatively frequent.

| Cuscuta Epithymum, L., is homogamous. Honey is secreted
_ by the lower part of the ovary, and is sheltered by scale-like
appendages of the corolla. The flowers are visited by Sphegide,
and in absence of insects fertilise themselves (590, III.).

Cuscuta, according to Kuhn, has cleistogamic flowers (399).

Ipomea pestigridis, L., has cleistogamic flowers, which were
known to Dillenius.

Calonyction, Chois.—The flowers are sterile to their own pollen.

Orv. SOLANACEZ.

312. SOLANUM TUBEROSUM, L.—The peduncles stand almost
horizontal at the time of flowering, and the five-pointed rotate
limb of the corolla becomes nearly vertical. Five anthers meeting
to form a cone project from the flower and surround the style,
which protrudes beyond them and curves more or less downwards
at its stigmatic end. All the stamens bend very slightly down-
wards, and the lower anthers project somewhat in advance of the
others. The anthers begin to dehisce at their apex, and when
touched allow a little pollen to fall out; in some which I ex-
amined a large quantity of pollen-grains (from ‘013 to ‘(021 mm,
in diameter) remained in a shrivelled condition.

i Since the flower secretes no honey and affords little pollen, it
i is very scantily visited by insects, In spite of repeated watching,

426 THE FERTILISATION OF FLOWERS. [PART IIT.

I have only occasionally seen two common Syrphide, Zristalis
tenax, L., and Syritta pipiens, L., feeding on the pollen. Darwin
observed the flower visited by humble-bees.

The stigma, from its position, must be touched by an insect-
visitor before the anthers. In many flowers the end of the style
curves backwards so much as to stand beneath the anthers, in the
line of fall of the pollen, so that self-fertilisation may in such cases
occur. Treviranus was therefore not wholly wrong when he
described the genus Solanum as fertilised by the style curving
backwards to meet the anthers (742).

313. Sotanum DutcaMARA, L., is likewise devoid of honey,
and is at least as scantily visited by insects as S. tuberosum. I
have seen Rhingia rostrata, L., examining the greenish spots which
glitter like drops of fluid in the middle of the violet corolla, and
afterwards stroking the tips of the anthers with its labelle. Here
S. Dulcamara seems to delude the fly as Parnassia and Lopezia do
(590, IL, pp. 20-22). 8. Duleamara is also visited by pollen-
collecting Bombi, and pollen-feeding Syrphidz (609).

314. SoLANUM NIGRUM, L.—The flowers are devoid of honey,
but I have repeatedly seen two common Syrphide, Melithreptus
scriptus, L., and Syritta pipiens, L., feeding on the pollen. Both
stroked the outer side of the anthers with their labellz from the
apex downwards as far as the middle of the corolla. Sprengel
observed bees and humble-bees upon the flowers, I have given a
further account of the flower in No. 590, III.

Fic. 144.—Lycium barbarum, L.

1.—Flower, viewed from the front.
2.—Ditto, in section.
a, protecting hairs; st, stigma,

315. Lycrum BaRBARUM, L. (L. vulgare, Dun.)—Honey is
secreted in large quantity by the naked ovary, and accumulates in
the base of the tube, which is 7 to 10 mm. long, The corolla

PART 111. | THE MECHANISMS OF FLOWERS. 427

widens out above, and is smooth within, except that a ring of close
woolly hairs surrounds it at the base of the funnel-shaped, ex-
panded portion ; on a level with this ring, five similar rings of bairs
surround the five stamens, and effectually exclude rain. The
corolla divides above into five violet lobes, which spread out to
a diameter of 16 to 22 mm, The funnel-shaped mouth is light-
coloured, and marked with dark-violet lines (pafhfinders) coursing
towards the base of the flower. Stigma and anthers ripen to-
gether, and stand at the same height. The style is sometimes
bent upwards above the anthers, as in the figure, but as a rule it
is in immediate contact with them. Insect-visits, therefore, may
lead equally well to cross- and self-fertilisation ; and in absence of
insects self-fertilisation in most cases takes place,

Visitors: Hymenoptera—Apide; (1) Apis mellifica, L. $, s., ab.; (2)

Bombus agrorum, F, 9, s.; (8) B. lapidarius, L. 9, s., both very frequent.
See also No. 590, Ill.

Atropa Belladonna, L., is likewise adapted for humble-bees.
I have seen it visited by nine species of bees and by Thrips
(590, IIL.),

Mandragora vernalis, Bert., is proterogynous, according to
Hildebrand (351).

LIochroma tubulosum, Benth., is proterogynous with persistent
stigmas, The deep-blue, pendulous flowers are tubular, widening
out at the mouth, and are supposed by Delpino to be fertilised by
humming-birds (177).

Scopolia carniolica, Jacq. (S. atropoides, Schult), is protero-
gynous (351).

316. HyoscyAMUS NIGER, L.—Cross-fertilisation is insured,
or at least favoured, by the prominent position of the stigma.
Sprengel found the plant visited by humble-bees, and the dimen-
sions of the flower seem well suited to these insects. I have seen
only Halictus cylindricus, F. 2, collecting pollen on the flower.

Browallia elata, L.—The corolla is hypocrateriform, and its
mouth is blocked by the much expanded filaments of the two
superior stamens, which are inserted in the throat of the corolla ;
these leave only two very narrow openings through which a thin
proboscis may pass. The proboscis entering in this way touches
the anthers (the inferior pair of which is inclosed in the tube), and
also the stigma which stands between the two pairs of anthers ; the
stigma smears the entering proboscis with viscid matter in the

428 THE FERTILISATION OF FLOWERS, [PART III,

young flower, and receives pollen from it in the old. Delpino
considers that the brown colour of the broad superior stamens is a
device to guide insects that have alighted on the flower towards the
pollen. His view that the flower is fertilised by Sphingide and
Bombylidee is opposed to this, for these insects seek honey only.
Species of Anthophora, which Delpino thinks may possibly be also
fertilisers, are likewise scarcely fitted to reach the pollen of
Browallia (178, 360).

My brother Fritz Miiller tells me, in a letter dated November
10, 1869, that he finds in the allied genus Franziscea (Brunfelsia)

Fig, 145.

Syste? of ape pete from oe Half of the corolla and two stamens have been removed.
a, anthers; st, s
The dotted line i sMionien the the. aK which the insect’s proboscis must take to reach the honey.

a structure similar to that described by Delpino for Browallia. A —

handsome species of Franziscea, occurs at Itajahy. In this there

are two lateral entrances to the tube, but between them the
throat of the corolla is blocked, not by a valve formed by the

stamens (valvola staminale, Delpino), but by the style which bends
forward to apply itself to the anterior wall of the corolla.

Schizanthus, Rz. and P.—The two stamens are inclosed by the |

lower lip, and spring up when an insect settles on the latter: the
stigma is at first shorter than the stamens, but after they have
burst free it lengthens and projects beyond them, so as to be now
the first part touched by an insect-visitor (346).

Se a ee ee a ee

PART III. | THE MECHANISMS OF FLOWERS. 429

Orv. SCROPHULARINE.

317. VERBASCUM NIGRUM, L.—The long yellow racemes are
very striking, and the flowers are made still more conspicuous by
the orange-red anthers and violet hairs upon the filaments. The
plant is visited by very various species of insects.

I sought repeatedly for honey without success, and had come to
the conclusion that the flower contained none. On July 28, 1871,
however, towards evening, [ saw a small moth, Ephestia elutella,
Hiibn.,) busy sucking very assiduously on the flowers of a plant of
this species in my room. Standing on a petal, it thrust its
proboscis down between two stamens? into the short tube, and
applied it to various parts of the inner wall of the corolla. After
spending a considerable time on one flower, it rolled up its proboscis
and flew off to another. It continued these operations for some
minutes, and therefore certainly found honey; and the next
morning I found in many flowers, but not in all, minute drops
of honey adhering to the smooth inner surface of the tube. The
flowers afford a large quantity of orange-red pollen, accessible to
all insects; and I observed that in the case of Syrphus balteatus
the violet clavate hairs form a third attraction.

The position of the parts of the flower makes cross-fertilisation
in case of insect-visits not inevitable but exceedingly likely, while
in absence of insects self-fertilisation easily occurs. The short tube
widens out into a flat, five-lobed limb, which takes up an almost.
vertical position: the inferior lobe is the longest, and the two
superior are shorter than the lateral lobes, so that an insect settles
most conveniently upon the inferior.. The stamens project almost
horizontally, but curve slightly upwards from the tube, and diverge
slightly from one another ; they alternate with the petals, and again
the superior is the shortest and the two inferior longer than the
lateral. The anthers, which stand close together, dehisce along

_ their outer edge, covering themselves almost completely with

orange-red pollen. The style is shorter than the inferior stamens,
and bent down slightly below them. An insect standing on the
inferior petal generally touches the knobbed stigma first, on its way

1 Named for me by my friend Dr. Speyer, of Rhoden.

2 Just between each pair of stamens, the central part of the corolla bears a
chestnut-brown spot. Sprengel (702, p. 122) considered these spots to be honey-
guides, though he could find no honey in the flowers, My discovery of honey
confirms his view.

430 THE FERTILISATION OF FLOWERS. [PART III.

to the anthers ; and thus cross-fertilisation is favoured, though stigma
and anthers ripen together. In absence of insects, self-fertilisation
is possible, as the stigma frequently stands in the line of fall of
the pollen.

Visitors: A. Hymenoptera—Apide : (1) Bombus agrorum, F. §, s. ; (2)
B. terrestris, L. 2,8. and c.p.; (3) Andrena pilipes, F. ?, ¢.p.; (4) Prosopis
signata, Pz. 9, fp.; (5) P. communis, Nyl. 9,fp. B. Diptera—(a) Bomby-
lide : (6) Systcechus sulfureus, Mik., s. ; (b) Syrphide: (7) Syrphus balteatus,
Deg., f.p. and licking the staminal hairs: (8) Eristalis arbustorum, L., do. 3
(9) Syritta pipiens, L., do. C. Lepidoptera—Microlepidoptera : (10) Ephestia
elutella, Hiibn., s. D. Coleoptera—Nitidulide: (11) Meligethes, ab. 'E.
Thysanoptera ; (12) Thrips, ab. F. Neuroptera ; (13) Panorpa communis, L.,
licking various parts of the flower.

318. VERBASCUM PH@NICEUM, L.—The structure of the flower
agrees with that of the preceding species, but I have hitherto failed,
as Sprengel also did, to discover any honey; I have never seen any
insect sucking on this flower. I once saw Andrena fulva, Schrank,
@, insert its proboscis into three or four flowers and then immedi-
ately withdraw it; it then flew away, having doubtless failed to
find anything.

Visitors : A. Hymenoptera—Apidw: (1) Apis mellifica, L. §, c.p.; (2)
Bombus muscorum, L. §, ¢.p. ; (3) Andrena dorsata, K. 2, ¢.p. ; (4) A. fulva,
Schrank, 9, vainly seeking honey ; (5) Halictus sexnotatus, K. 2, ¢.p.,—-I
could see clearly how this bee loosened the pollen with its mandibles, and
swept it with the tarsal brushes on its fore and midlegs into the collecting
hairs on its hindlegs, B. Diptera—Syrphide : (6) Rhingia rostrata, L., very
ab., f.p.,—I have often seen a specimen of this fly on almost every flower, eating
pollen, and also licking the staminal hairs,

319. VerBascum TuHapsus, L. :—

Visitors : A. Hymenoptera—(a) Apide : (1) Apis mellifica, L. § ; (2) Bom-
bus Scrimshiranus, K. ? ; (3) B. hortorum, L.'% ; (4) Halictus smeathmanellus,
K. 9, all cp. ; (5) H. cylindricus, F. ¢; (6) Andrena parvula, K. ¢, both of
these seemed to be sucking ; (b) Sphegide : (7) Polistes gallica, F. 2 (Thur.),
seemed also to be sucking. B. Diptera—Syrphide@ : (8) Helophilus floreus, L. ;
(9) Syritta pipiens, L. ; (10) Ascia podagrica, F., all three fp.

Verbascum Lychnitis, L.—I saw this species in Thuringia, visited
by species of Halictus collecting pollen, and by Diptera and
Coleoptera (590, III.).

Darwin, in Forms of Flowers, shows that V. Thapsus and
V. Lychnitis readily produce hybrids in a state of nature ; and that,
since these hybrids are absolutely barren and the self-fertilised

PART III. | THE MECHANISMS OF FLOWERS. 431

plants fairly fertile, in this case insects-visits by promoting

_ hybridisation do harm.

; According to Delpino, the Verbascums are adapted for pollen-
collecting bees, which, clinging to the hairs on the stamens, clear

i the pollen off the anthers and fly rapidly to another flower. I

agree with this view, and look upon it as the most plausible
_ explanation of the hairy stamens. But from my own observations

_ it isclear that the small pollen-feeding bees (Prosopis) and Syrphide
| are very frequently the fertilisers of this genus. Delpino goes too

far in saying that the flowers of Verbascum are adapted solely for
bees (esclusivamente melittofili), and that the visits of all other insects
are accidental and without significance (178, IL, pp. 296-298).
Calceolaria pinnata, L.— Each of the two anthers is modified, as
in Salvia pratensis, into a lever, of which one arm bears a_ pollen-
less anther-lobe and stands in the mouth of the corolla. When this
- arm is touched by an insect, it causes the other, the pollen-bearing
lobe, to shed its pollen. Self-fertilisation may take place in the
falling off of the corolla (352).

i’ 320. LINARIA VULGARIS, Mill—The flowers which I have
examined do not agree in all points with Sprengel’s description.

_ Honey is secreted by the base of the ovary, which is especially

prominent anteriorly, opposite the lower lip. As a rule the honey
does not, as Sprengel thought, leave the tip of the spur empty,
_ flowing down at intervals in large drops which cannot reach the
' bottom for the air contained there ; but it glides ina smooth, narrow
groove, bordered by short, stiff hairs, which passes from the nectary
between the two anterior stamens, and thence to the tip of the spur,
which it fills to a depth of 5 or 6 mm, or even more. In several
- hundred flowers which I examined, I found two which corresponded
in this point with Sprengel’s description, so it seems probable that
_ he based his account upon an abnormal specimen.
The adjacent sides of the two inferior stamens are closely beset
with pointed processes at their base, which protect the honey from
Sshort-lipped insects, when such succeed, as ants frequently do, in
_ entering the flower. The hairs bordering the groove protect the
_ honey in like manner from insects, and also help to keep it in its
course ; the length of the spur would be of no advantage unless
the honey were strictly confined to it.

The length of the spur (10 to 13 mm.) excludes short-lipped
__ bees from the honey, and flies and beetles are prevented from
_ entering the flower by the tumid lower lip, which completely

432 THE FERTILISATION OF FLOWERS. [PART III.

closes the tube ; by these characters the flower becomes exclusively
adapted for those most diligent of fertilising-agents, the long-
proboscised bees. The palate of the lower lip is of a bright orange
colour, forming a “ pathfinder”-; guided by this, the bee presses
down the lower lip, and creeps so far into the tube as to be able to
thrust its head into the wide part of the spur and then reach the
honey. In doing this, the back of the bee comes in contact with
the anthers and stigma ; these are matured simultaneously, and the
stigma lies between the shorter and longer pairs of stamens, so that
the bee can bring about both cross- and self-fertilisation. Probably,
if pollen from another and from the same flower are applied to the
stigma, the former outstrips the latter. In absence of insects, self-
fertilisation is possible. The visitors consist exclusively of bees.

Visitors : Hymenoptera—(a) Apide: (1) Apis mellifica, L. $, very ab.
To suck, it creeps almost entirely into the flower and thrusts its head into the
wide entrance of the spur, which it empties down to a depth of 2—3 mm. It
creeps out again with its back covered with pollen, and proceeds more fre-
quently to flowers at the same height on neighbouring plants than to higher
flowers on the same. In other cases I have seen the honey-bee bite a hole in
the spur, and empty it, as Sprengel describes. Sprengel has correctly described
its behaviour while collecting pollen : “It slightly separates the lower lip of the
corolla from the upper, and thrusts its head so far in as to reach the anthers
and obtain their pollen.” (2) Bombus terrestris, L. 2, sucking normally. It
inserts its head, thorax, and forelegs, into the flower, then thrusts its proboscis
(7—9 mm.) almost to the tip of the spur, and emerges with the upper surface
of its head, pro- and meso-thorax thickly covered with pollen. Sometimes it
sweeps off part of this pollen with the brushes on its fore and midlegs, and
places it on the hindlegs, Sprengel’s idea that the large humble-bees do not
enter the mouth of the flower is accordingly erroneous. (3) Bombus hortorum,

L. 9 9 and ¢. I have very frequently seen this bee empty the flowers of their — |

honey, which ‘it can do more quickly owing to the length of its proboscis
(17—21 mm.) than the preceding species. Even the males sometimes swept the _
pollen off their heads with their forelegs, and always had a number of pollen-
grains on all their tarsal brushes ; (4) Megachile maritima, K. ¢ (8—9), s. ;
(5) Osmia nea, L. 9 (9—10), repeatedly, s. and ¢.p.; (6) O. leucomeleena, K,
(parvula, Duf.), 2 (24), ¢.p.; (7) Anthidium manicatum, L. 9 ¢ (9—10), ab.
both s. and (?) ep. ; (8) Andrena Gwynana, L. ? (24), e.p.; (6) Formicide: —
(9) Various species, ab., s.

Delpino observed Linaria vulgaris fertilised by the hive-bee and
by Bombus ttalicus (172).
Linaria alpina, Mill. is likewise adapted for humblachaae but is
visited by Lepidoptera also (609).
Linaria minor, Desf., is very rarely visited by insects, and
fertilises itself regularly (590, IT).

part ut.) | THE MECHANISMS OF FLOWERS. _ 433

Linaria Cymbalaria, Mill. is visited chiefly by bees (590, tt.).
Cleistogamic flowers occur in Linaria according to Michalet (524)

and Kuhn (399).

321. ANTIRRHINUM MAJUS, L.—This plant differs from Zinaria
vulgaris (1) in the much greater size of its flowers, into which our
largest humble-bees can enter bodily, (2) by its more firmly closed
entrance, which excludes the smaller bees, (3) in its nectaries and
honey receptacles.

The honey is secreted, as Sprengel suggested, by the smooth,
green, fleshy base of the ovary, whose upper part is paler in colour
and covered with fine hairs; but it does not flow, as Sprengel
thought, down into the short spur—which is hairy within, and for
that reason unfitted to be a honey-receptacle, but it remains ad-
herent to the nectary and to the base of the anterior stamens. The
short wide spur permits the insect’s proboscis to reach the honey
from below ; above and in front it is protected by a thick fringe of
stiff, knobbed hairs on the angles of the anterior stamens. -

The flowers are fertilised chiefly by humble-bees, of which I
have observed the following species: (1) Bombus hortorum, L.;
(2) B. terrestris, L.; (3) B. agrorum, F.; (4) B. silvarum, L.;
(5) B. lapidarius, L. The females and workers, and in late summer
the males also, creep bodily into the flower, and creep out backwards
dusted on their backs with pollen. From time to time they brush
off the adhering pollen from their thorax with the tarsal brushes
of the fore and midlegs, and from the abdomen with the tarsal brushes
of the hindlegs. Not only the females and workers, but the males
also, perform this action, which seems, therefore, to be done more for
cleanliness than to collect the pollen, though the females and workers
naturally make use of it, placing it in the pollen-baskets on their
hindlegs. I have also seen Anthidium manicatum, L. 2, Megachile

| fasciata, Sm. 3, and Osmia rufa, L. 2, creep into the flower and

emerge with their backs covered over with pollen. Smaller bees
only exceptionally creep into still fresh flowers, and are useless to
the plant: I have only once seen Megachile centuncularis, L. ?,
succeed in entering; on the other hand I have repeatedly seen
- small species of Halictus (H. zonulus,Sm. °, H. morio, F. 2, H.
Smeathmanellus, K. 3) flying from flower to flower until they
reached an old flower, which in withering had opened slightly and
permitted them to enter. This showed clearly how far the fast
closure of the mouth is useful to the plant; if the small bees
could enter from the first, they would use up much of the honey,
FF

434 THE FERTILISATION OF FLOWERS. [parr Lil,

and the flowers would be less diligently visited by the humble-
bees.

Dr. Ogle found that Antirrhinum produced no seed when
protected from insects by a tent of gauze (632).

Maurandia, Ort., Chelone, L., and Pentstemon, L’ Her., are, ac-
cording to Delpino, proterandrous, the style coming to occupy the
place of the stamens. In the two last genera, the stamens are
broad, fleshy, and hollowed out at the base to secrete and lodge the
honey. Pentstemon is fertilised by Bombus, Anthidiwm, and Apis.
(178, 360). The position of the fifth stamen in Pentstemon and
its frequent partial or complete abortion has been discussed by
Dr. Ogle (632). A very thorough account of the floral mechanism
of Pentstemon is given by Errera (230).

322. SCROPHULARIA NODOSA, L.—In most Lamiales and Per-
sonales the anthers lie in two pairs, one behind the other, and

Fria. 146.—Scrophularia nodosa, L.

t.—Flower, in first stage, from the front (x 7).

2.—Ditto, from below (x 34).

8.—Older flower, fertilising itself, viewed from the side.

a, calyx; b, corolla; ¢c, stamen; c’, fifth metamorphosed stamen; d, ovary; e, style; f, stigma
g, nectary ; h, drop of honey.

: 4—7.—Fifth stamen in various stages of reversion towards its original form (x 12). °

i, black membranous lobe ; k, anther-lobe.

touch an insect-visitor on the dorsal surface ; the stigma then, to in-
sure cross-fertilisation, must also touch the insect on the back, and
the style can scarcely lie elsewhere than between the two pairs of
stamens, along the upper part of the corolla. The superior stamen
comes in the way, and accordingly disappears ;! it has no chance of
reappearing permanently, for it is directly injurious, and is weeded
out by natural selection. I have only once found a flower of

Cf. Dr. Ogle, No. 632, p. 51.

PART III. | THE MECHANISMS OF FLOWERS. 435

Lamnium album with five stamens; the upper lip was absent, and
the fifth stamen, which stood behind the other four, was well
formed, but shorter than the others.

In Scrophularia, on the other hand, the anthers come in contact
with the ventral surface of the insect. The fifth stamen is thus
useless, but not injurious; whether it be present or absent is of no
importance, and it is therefore beyond the influence of natural
selection. Accordingly, the small black scale-like appendage on the
upper wall of the corolla in Scrophularva (¢, 1, 2, 3), which repre-
sents the fifth stamen, shows not unfrequently more or less com-
plete reversion to its primitive form (4-7, Fig. 146). The more
completely it approaches its typical form, the more perfect also are
the pollen-grains which it bears; thus in the anther &, 4, not half of
the pollen-grains attained the normal size ($$ mm. in diameter) ;
most of them were much smaller ($¢§ mm.) and shrunken; in the
anther k, 7, only a few pollen-grains fell short of the normal size.
In exceptional cases the anther even dehisces, and lets part of its
pollen escape.

The flowers of Scrophularia are remarkable for being speci-
ally visited by wasps. The wide globular corolla is about
5 mm, in diameter, and in its base, near the superior side, two
large drops of honey may be seen, which are secreted by the
yellowish base of the ovary. Wasps visit the flowers in great
numbers; clinging with all six legs to the outside of the flower,
with the abdomen applied to it below, they easily insert their
heads between the upper and lateral lobes of the corolla and reach
the honey with very little loss of time.t In young flowers they
- touch the stigma, and in old flowers the anthers with the under-

side of the head and of the pro- and meso-thorax, and thus
_ regularly fertilise younger flowers with the pollen of old, as
_ Sprengel showed. Severin Axell's doubts regarding the possibility
of proterogynous dichogamy in entomophilous flowers may be
easily refuted by observing Scrophularia in flower in the open air.
_ For, as Sprengel showed and as I have repeatedly observed, flowers
aie constantly to be seen whose stigmas are covered with pollen,
but whose anthers are still unripe and hidden within the corolla.
Sprengel is wrong in saying that fertilisation can only be effected
by insects. The stigma, when supplied with pollen by insects,
bends down over the lower lip and withers, while the anthers ripen
- and project beyond the lower border of the corolla ; but in absence
of insects, as I have frequently seen in plants flowering in my

1 See Sprengel (702), Title-page, fig. xxv.
FF 2

436 THE FERTILISATION OF FLOWERS. [PART III.

room, the stigma remains fresh and outstretched, while the anthers
dehisce immediately above, letting part of their pollen fall upon it.
I have likewise observed on plants in my room that such self-fertili-
sation regularly produces capsules filled with well-formed seeds.
In long-continued cold and wet weather, when neither wasps nor
bees are about, all the capsules of Scrophularia are well filled.

In sunny weather cross-fertilisation never fails, for all our wasps,
except V. Crabro, are frequent visitors.

According to Mr. A. 8. Wilson, wasps on Serophularia begin at
the top of the inflorescence and proceed downwards; so that here
the crossing of separate plants is insured just as it is in proterand-
rous plants with elongated inflorescences (e.g. Labiate), where the
fertilising-agents (bees) proceed from below upwards (778).

Hymenoptera—(a) Vespide: (1) Vespa vulgaris, L.; (2) V. rufa, L. ; (3)
V. germanica, F.; (4) V. media, Deg.; (5) V. holsatica, F., all s., very ab;
(b) Apide: (6) Bombus agrorum, F. 2? %,8., scarce ; (7) Halictus sexnotatus,

K. 9,8. and «p.; (8) H. zonulus, Sm. ¢,s.; (9) H. flavipes, F. g,s. See
also No. 590, III.

Scrophularia aquatica, L.—The floral mechanism and the insect-
visitors are similar to those of S. nodosa (590, IIL.).

Scrophularia occurs with cleistogamic flowers (Kuhn, No. 399).
The most thorough account of the fertilisation of Scrophularia is
given by Mr. W. Trelease, who also gives a réswmé of the special
literature (737).

Collinsia bicolor, Bth., and C. verna, Nutt.—In these flowers the
stamens and style lie near the lower side of the flower; the fifth
stamen, modified into a honey-gland, and the honey-receptacle,
which consists of a pouch near the base of the corolla, are on the
upper wall. The flower imitates very closely the Papilionaceous
type, even to the production of als, vexillum, and carina.
(Delpino, No. 178). In absence of insects, the flowers fertilise
themselves, and are fertile to their own pollen (360).

Mimulus luteus, L. (M. guttatus, D.C.)—Bees entering the flower
touch first the inferior lobes of the stigma, which cover up the
anthers. Immediately afterwards the stigmatic lobes fold wp and
expose the anthers to be touched by the bee, which thus becomes
dusted with fresh pollen (Batalin, No. 38).

The case of J. Tillingti is quite similar (Behrens, No. 49).

Glossostigma elatinoides, according to Cheeseman, has a similarly
irritable stigma (132).

Mimulus (Diplacus) glutinosus, Wendl. var. B (D. puniceus,
Nutt.), behaves in the same manner (Hildebrand, No. 352).

part mt.] © .THE MECHANISMS OF FLOWERS. 437
Vandellia, L., has cleistogamic flowers (399).

323. DIGITALITIS PURPUREA, L.—Honey is secreted by an
annular ridge surrounding the base of the ovary (a, 1, 2, Fig. 147).
This ridge is not ‘covered thickly with short hairs’ as Sprengel
described it, but is perfectly smooth ; the ovary only becomes hairy
above the ridge.

The anthers and stigma lie pointing downwards near the upper
wall of the corolla. The longer stamens are ripe before the shorter
ones, and these before the stigma, The dimensions of the flower

Fic. 147.— Digitalis purpurea, L.

1.—Young flower after removal of the right half of the calyx and corolla. The taller anthers -
eS he on the point of dehiscing. This figure should be turned round horizontally in the direction of
e arrow.

2.—Tip of style of the same flower, enlarged.

3.—A-somewhat older flower. ‘The taller anthers are now empty, the shorter pair are dehiscing
and ate covered with pollen. Viewed from below, after removal of the lower half of the calyx and
corolla,

4.—Tip of style of the same flower.

5.—Empty anthers and stigma of an old flower, from below.

——— x

suggest that it is adapted for humble-bees, for no other native
insects are large enough to touch the stigma and anthers with
their backs when creeping into the tube; and, as a matter of fact,
humble-bees are the only fertilisers of the Foxglove. Sprengel, on
_ the title-page of his work, represents B. terrestris, ? , creeping into
__ this flower. When bees frequent the plant abundantly, all the four
_ anthers are emptied of their pollen before the stigmatic lobes
i. (, 1, Fig. 147) separate. In absence of humble-bees, the anthers
remain covered with pollen until the stigmatic lobes have
_ spread apart; and then when the corolla falls off this pollen is

438 THE FERTILISATION OF FLOWERS. [PART III.

brought in contact with the stigma, or some may even have fallen
on the stigma previously. The flowers almost always bear seed,
even in long-continued rainy weather, and therefore it is probable
that self-fertilisation is effective; Hildebrand’s experiments are no
evidence of the contrary, for he only showed that the stigma before
opening is incapable of fertilisation (342). The large, widely-open
flowers, naturally receive many unbidden and useless guests. If the
plant is thus at a disadvantage in comparison with Antirrhinum,
it has at least the advantage of letting its fertilising agents do their
work more quickly, visiting more flowers in a given time.

Visitors: A. Hymenoptera—Apide: (1) Bombus terrestris, L. 2; (2)
B. hortorum, L. 9 ; (3) B. agrorum, F. 9, all three ab.,s. ; (4) Andrena coitana,
K. 2 (Sld.), ab., c.p.; (5) Halictus cylindricus, F. 9, ab., ep. B. Coleoptera
—(a) Nitidulide : (6) Meligethes, very ab. ; (6) Cryptophagide : (7) Anthero-
phagus pallens, Ol., scarce; (c) Malacodermata: (8) Dasytes. The last five
are quite useless visitors.

Digitalis lutea, L., is fertilised by Bombus hortorum, L., which
can only insert its head into the corolla (609).

Digitalis ambigua, Murr. (D. grandiflora, Lam.), is fertilised by
humble-bees, which creep bodily into the corolla. The flower is
proterandrous, and bees begin at the base of the raceme and pro-
ceed upwards (590, Ill.; 609).

324, VERONICA CHAMaiDRYS, L.—Honey is secreted by a
yellowish fleshy disk below the ovary, and lies in the base of the
tube sheltered from rain by hairs on the corolla. The flowers are
rendered conspicuous by their bright blue colour, and by associa-
tion in racemes; dark blue radiating lines and a central white spot
on the limb of the corolla guide insects towards the honey. The
anthers and stigma ripen together; the style points obliquely
downwards in front of the anterior (inferior) petal, the two stamens
diverge on either side, and stand opposite to the lateral petals;
fertilisation can therefore only be effected by the aid of insects.
The anterior petal forms the most convenient landing-place, and
the stigma is usually touched before the anthers by the ventral
surface of the insect. The insect next tries to cling to the en-
trance of the short tube with its forelegs, and in doing so it
catches hold of the thin, flexible bases of the stamens: quite
unintentionally it draws the stamens inwards beneath it, and dusts
its ventral surface with pollen. The thinning of the style at its
base is another adaptation towards this plan of cross-fertilisation,
for it insures that the stigma shall be touched by the ventral

parti] . THE MECHANISMS OF FLOWERS. 439

surface of the insect, and allows of the style being so slightly in-
clined that its presence does not interfere with the insect when
alighting. An insect alighting on one of the lateral petals some-
times draws the stamen opposite to this petal against its body, but
with far less certainty. The chief visitors are Syrphide.

Visitors: A. Diptera—Syrphide : (1) Rhingia rostrata, L., s., freq. ; (2)
Melanostoma mellina, L. ; (3) Ascia podagrica, F., both very abundant. I
repeatedly saw both effecting cross-fertilisation in the manner described. B.
Hymenoptera—Apide : (4) Apis mellifica, L. $,¢.p.; (5) Andrena Gwynana,
K. 9; (6) A. fulvicrus, K. 9; (7) Halictus longulus, Sm. ?, the last three
both s. andc.p. C. Coleoptera—Cistelida : (8) Cistela rufipes, F., devouring
the anthers. See also No. 590, m11., and No. 609.

Fia. 148.— Veronica Chamedrys, 1.

1,—Flower, viewed from the front.

2.—Small fly (Ascia podagrica, Syrphide) hovering in front of the flower, attracted by its colour.

8.—Flower at the moment when the fly, ea, aaeig on the inferior petal, grasps the bases of the
filaments, and strikes the anthers tegether against the under surface of its body.

4.—Ceutre of the flower, twice as much enlarged.

5.—Pistil and nectary.

6.— Calyx, with pistil and nectary.

7.—Tube in longitudinal section.

sd, protecting hairs; gr, style.

Veronica urticifolia, L., has a similar floral mechanism to that of
V. Chamedrys, and is likewise fertilised by Syrphidw. The honey
is quite exposed without any contrivance to shelter it. The flowers
are rose-pink, which is probably a more primitive colour than
blue both in Veronica and in Myosotis (589, 609).

Veronica montana, L., is more conspicuous and more abundantly
_ visited by insects than V. Chameedrys (590, 609).

325. VERONICA BeccaBuNnGA, L.—This species agrees with V.
Chamedrys in regard to its nectaries and also in the means adopted

440 THE FERTILISATION OF FLOW ERS. [PART III.

for sheltering and pointing out the honey. It differs from it only
in certain apparently trivial points, viz. in the development and
position of the style and stamens:—yet these apparently trifling
differences greatly influence the mode of fertilisation and the
possibility of self-fertilisation in the absence of insects.

When the flower opens, the stigma is already well-developed ;
it is provided with long papille, and capable of holding fast pollen
applied to it. The anthers still remain closed. The stamens and
style project forwards in a straight line from the flower and afford a
standing-place for insects. In cold, windy, or rainy weather the
flowers only open partially, and the anthers remain in contact with
the stigma, leading to regular self-fertilisation. In warm sunshine
the petals expand widely, coming to lie almost in one plane; the
stamens are caused thereby to diverge more and more, and the’
anthers are thus removed to a distance from the stigma before

Fic. 149.—Veronica Beccabunga, L.-

-1.—Flower, viewed obliquely from above, so that the upper petal is foreshortened (x 8).
2.—Corolla, after removal of the stamens, viewed from the front (x 3),
3.—Flower, after removal of corolla and stamens, seen from the side (x 7).

i a, calyx; b, corolla; c, stamen; d, ovary; e, style; f, stigma; g, nectary (green); h, protecting
airs.

dehiscing. Insects frequent the plant in considerable numbers.
The most abundant visitor is a small species of Syrphidee, Syrztta
pipiens, L.; hovering backwards and forwards in its jerky flight
before the flowers, it suddenly alights on one; sometimes it
settles on the projecting style and stamens, which bend beneath its
weight, and creeps forward a step or two in order to thrust its
proboscis (3 mm. long) into the tube (1 mm.) ; sometimes it alights
on the anterior or on one of the lateral petals, and pulls down one of
the stamens with its forefeet, until it can reach the pollen with its
proboscis. It thus brings various parts of its body in contact with the
anthers and stigma, and performs sometimes cross-fertilisation, some-
times self-fertilisation. Most usually cross-fertilisation results, for the
nsect alighting on the projecting style and stamens usually touches
the stigma with the ventral surface of its body, already dusted with
pollen. A smaller species of Syrphidee, Ascia podagrica, F., visits

PART III. | THE MECHANISMS OF FLOWERS. 44]

the flowers very abundantly and in a similar way. All other
visitors come as stragglers.

A. Diptera—(a) Syrphide: (1) Syritta pipiens, L.; (2) Ascia podagrica,
F. ; (8) Eristalis sepulcralis, L., s. and f.p.; (0) Muscide: (4) Scatophaga
stercoraria, L., s. and f.p., also several small Muscide. B. Hymenoptera—
Apide: (5) Apis mellifica, L. $,s.; (6) Andrena parvula, K. 2, s. and e.p. ;
(7) Halictus sexstrigatus, Schenck, 9, s. and c.p.

326. VERONICA OFFICINALIS, L.—The flowers do not open so
widely even in warm sunshine as do those of V. Chamedrys. In
fully expanded flowers the upper and lower petals only diverge at
an angle of 70° to 80°, and the two lateral petals at 90° to 100°.
The two stamens, which are very thin at the base, project from the
flower at an angle of 30° to 40° from one another, and from the
style which stands below them. Insect-visitors touch the stamens
and stigma with various parts of their bodies, and lead to cross-
and self-fertilisation indiscriminately. In flowers kept in the house
and protected from insects, the stamens bend inwards and down-
wards as they begin to wither until they touch each other and the
stigma, producing self-fertilisation. The thinning at the base of
the stamens, which in V, Chamedrys was shown to assist insects to
perform cross-fertilisation, is here seen to aid self-fertilisation only.

A. Diptera—(a) Empide : (1) Empis livida, L., s., ab. ; (b) Syrphide:
(2) Helophilus floreus, L.,s. ; (3) Syritta pipiens, L., ab.,s. B. Hymenoptera
—Apide: (4) Halictus albipes, F., e.p.; (5) Bombus (Apathus) vestalis,
Foure. ?,s.; (6) B. Barbutellus, K. 2, s,—this large bee seemed dissatisfied

with the small amount of honey, for after visiting a few flowers it went off to
Glechoma hederacea. See also No. 609.

327. VERONICA spicaTA, L. (Thuringia).—V. spicata shows a
remarkable tendency to vary between proterandrous and _pro-
terogynous dichogamy. On many plants, the style protrudes
before the flower is fully opened (6, 4), and curves downwards
and ripens its stigma before the anthers dehisce (0, 5). On other
plants, when the flower opens, the style is much shorter than
the stamens (b, 1; 2), and only reaches its full length and
ripens its stigma when the anthers have been emptied of their
pollen (0, 3).

On plants of both sorts, flowers not unfrequently occur whose
styles ‘never reach their full development, but remain concealed in
the tube ; and on some plants this is the case throughout all the
flowers. These aborted styles are often double (6, 8). Honey is
secreted by the fleshy base of the ovary (h, 6, 7); it lies in the

442 - THE FERTILISATION OF FLOWERS. [PART ITI.

tube of the corolla, which is about 2 to 3 mm. long, and is sheltered
from rain by a ring of long stiff hairs at the mouth of the tube.
In case of insect-visits, cross-fertilisation is insured by the proter-
androus or proterogynous condition, and by the situation of the
stigma which projects beyond the anthers. I have never observed

Fia. 150.—Veronica spicata, L.

1.—Flower, shortly before dehiscence of the anthers (a), viewed from the front. The stigma (b)

is still immature, and stands far below the anthers.
o, superior petal; ss, lateral, wu, inferior, petals.

2.—Ditto, somewhat more expanded, from the side. .

8.—Ditto, from the side. The anthers have withered; the stigma is mature, and stands below
and in front of the anthers (x 34).

4.—Young flower, from another individual. The style already protrudes from the flower, and
the stigma is so far developed that pollen readily adheres to it. The anthers are still closed and
concealed within the tube.

5.—Another somewhat older flower, from the same individual, viewed from the front. The stigma
is fully ripe, the anthers are in the act of dehiscing (x 34).

6.—Ovary and nectary (hk) from the side.

7.—Nectary, after removal of the ovary, from above.

§8.—An ovary, with two imperfect styles (x 7).

self-fertilisation, though it may now and then take place by pollen
falling on the stigma.

Visitors : Hymenoptera—(a) Apide : (1) Apis mellifica, L. %, ¢.p., ors. ;
it even thrusts its proboscis into the lowest, oldest flowers whose corolle
have fallen off; (2) Prosopis communis, Nyl. 9 g, s.; (0) Sphegide:
(3) Psammophila viatica, L. ¢, s.; (4) Cerceris labiata, F. 2 ¢, ab., s.; (5)
C. nasuta, K1. s.

Near Bozen according to Gerstiicker, V. spicata is visited chiefly
by species of Xylocopa (X. violacea, L., X. cyanescens, Brullé, X.
valga, Gerst.).

328. VERONICA HEDERAFOLIA, L.—The small, solitary, pale
flowers are less conspicuous than those of any other species described
here; they are very seldom visited by insects, but almost without
exception bear good seed, and the species is one of the commonest of

PART III. | THE MECHANISMS OF FLOWERS. ; 443

its genus. The presumption that this results from self-fertilisation
is increased by watching the plant when protected froin insects.
When the flower opens, the anthers are seen to have already de-
hisced, and to have their pollen-covered surfaces applied to the
stigma. Ihave myself observed that when insects are excluded
the plant regularly bears good seed.

The honey is secreted and sheltered as in V. Chamedrys; the
stamens are however not thinned at their bases. Even in case of
insect-visits, cross-fertilisation is not rendered more probable than
self-fertilisation; but when it does occur, its action probably has
the mastery.

I have only seen this flower visited by insects occasionally in
the first sunny days of spring; later in the season, the competition
of other flowers causes it to be neglected.

Visitors : Hymenoptera—A pide : (1) Andrenaparvula, K. 9,8. ; (2) Ha-
lictus nitidiusculus, K. 2? ; (3) H. leucopus, K. 2; (4) H. albipes, F. 9, all
three rather abundant, sucking on a small slope where few other plants were
in flower (April 11, 1869).

Veronica agrestis, L., possesses the same floral mechanism as
V. Chamedrys, but in an imperfect or rather in a retrograde
condition (590, IIL).

329. VERONICA SERPYLLIFOLIA, L.—The flowers are rendered
more conspicuous than those of V. hederm@folia, by dark violet lines

Fie. 151.—Veronica serpyllifolia, L.

1 —Flower, front view.
2.—Diagram of ditto :
a, Stigma; b, stamen; ¢, petal; d, sepal.

on the superior and lateral petals. They are doubtless more
visited by insects, and more frequently cross-fertilised ; and accord-

} _ ingly self-fertilisation does not take place at so early a stage.

In many flowers, the anthers are at first closed, while the stigma
is fully ripe; in this condition, insect-visits naturally lead at
once to cross-fertilisation. -In most flowers, on the other hand,
the stigma and anthers ripen together; the anthers stand more

444 THE FERTILISATION OF FLOWERS. [PART III.

or less close above and at the sides of the stigma, turning their
pollen-covered faces towards it; in many cases they stand so
close that the pollen in being teea out is directly applied to
the stigma.

ee platits which I kept in my room, I have seen Calliphora
erythrocephala, Mgn. (Muscidze), sucking honey and fertilising the
flowers. It thrust its proboscis several times into each, and there-
fore where anthers and stigma had ripened together, it performed
cross- and self-fertilisation indifferently.

V. saxatilis, Sep. (V. fruticans, Jacq.).—The small, but brightly

coloured flowers of this plant are fairly conspicuous, and secrete
abundant honey. ‘The visitors are numerous, and the mechanism
of fertilisation is the same as that of V. Chamedrys.

V. bellidioides, L., has no trace of the special adaptations for
cross-fertilisation that V. Chamedrys shows. Insect-visitors are
scarce, and cross-fertilisation can only take place if they happen to
touch the stigma and anthers with different parts of their bodies.

V. alpina, L.—The tiny flowers are very rarely visited by
insects, and in dull weather they remain closed and fertilise
themselves."

REVIEW OF THE GENUS VERONICA.

In this genus, as in Polygonum, Geranium, and others, the cer-
tainty of cross-fertilisation in case of insect-visits, and the abandon-
ment of the power of self-fertilisation even in absence of insects,
run parallel with the conspicuousness of the flowers and the con-
sequent certainty of their being visited. The chief species that
we have discussed may be arranged in the following order of
conspicuousness, taking into account the appearance of the whole
inflorescence :—(1) V. spicata, (2) V. Chamedrys, (3) V. officinalis,
(4) V. Beecabunga, (5) V. serpyllifolia, (6) V. hedereefolia. In
case of insect-visits, cross-fertilisation is rendered absolutely certain
in the first, and extremely probable in the second of these, but in
all the rest self-fertilisation is just as likely. In absence of insects,
on the other hand, self-fertilisation never or very rarely takes place
in the first and second; in the third it occurs regularly, but only
when the flower withers; in the fourth, it regularly takes place in

1 Lists of visitors to the following additional species of Veronica are given in my
Weitere Beobachtungen, Pt. 111.: V. Anagallis, L., V. triphyllos, L., V. arvensis, L. ;
and the following are discussed and figured in my Alpendlumen : V. alpina, L.,
V. aphylla, L., V. bellidioides, L., V. saxatilis, Sep.

PART III. | THE MECHANISMS OF FLOWERS. 445

dull weather while the flower is still fresh; in the fifth it occurs in
many flowers, and in the sixth in all, at the very outset. The
honey is secreted and guarded in much the same manner in all six
species, and so the likelihood of insect-visits can only depend upon
the conspicuousness of the flowers.
Wulfenia carinthiaca, Jacq., is proterogynous (Hildebrand,
No. 351).
Bartsia alpina, L., is proterogynous, and is fertilised by humble-
bees. The stigma and anthers have the same relative positions as in
Rhinanthus mayor (Fig. 156). Self-fertilisation is impossible (609).

330. ODONTITES SEROTINA, Rchb. (0. rubra, Pers., Huphrasia
Odontites, L.).—Honey is secreted by the lower parts of the ovary,
which is smooth, and swollen anteriorly (4, 6), while the upper part

Fig. 152.—Odontites serotina, Rchb.
1.—Bud, with exserted stigma (x 34).
2.—Flower, with the stigma lying between the anthers.@
3.—Flower, whose style projects far beyond the anthers.
4.—Flower, in which the style lies to one side.
5.

“ae two stamens of the left half of the flower, seen from the inside (x 7).
6.—Ovary.

a, base of the corolla; b, nectary; ¢, upper hairy part of the ovary; d, style; e, hairs which
unite the anthers ; f, hairs which prevent pollen from being scattered at the sides; g, sharp teeth
which prevent the bee from thrusting its proboscis between the bases of the filaments; h, path
taken by the bee’s proboscis.

(The flowers 2 and 4 should slant more forwards than they are here figured.)

is hairy : it is lodged in the base of the corolla, whose tube is 4 to
5 mm. long, and smooth within; the broad stamens, which almost
block the entrance of the tube, guard it from rain, and two to four
purple spots at the base of the lower lip serve as guides towards it.
The stamens almost touch each other below, where they are
covered on their inner sides with sharp points; close under the
anthers they are smooth and lie more widely apart. <A bee, after
alighting on the three-lobed under-lip, which affords a convenient
landing-place, can only thrust its proboscis into the flower close

446 THE FERTILISATION OF FLOWERS. [PART III.

below the anthers, in the position h, 2, and in doing so it cannot fail
to touch the downward-pointing ends of some of the anthers. The
four anthers are held together posteriorly by matted hairs (e, 5),
and anteriorly dehisce from the apex inwards (5, Fig. 152) by a
wide fissure ; so that a single touch on the part of the bee is com-
municated to all the anthers, and causes them all to shed a part of
their dry, dusty pollen. Hairs directed downwards at the edges
of the anthers (7, 5) prevent the pollen being scattered at the sides,
so that great part falls on the bee’s proboscis, and is carried to the
stigma of another flower.

The development of the flower of Odontites serotina varies in a
peculiar manner, and seems to depend upon the more or less
sunny nature of the spot. The style bearing the fully-developed
stigma usually projects far out of the bud shortly before it expands
(1, Fig. 152), and the flower can therefore be cross-fertilised when
it is scarcely open. In shady places, for instance among corn, the
style lags behind while the corolla and stamens continue to grow,
so that the stigma stands between the taller anthers and gets self-
fertilised (2, Fig. 152). From the great productiveness of all the
capsules in shady places where insect-visits are rare, we may con-
clude that such self-fertilisation is efficient. In sunny spots the
style continues to grow along with the corolla and stamens, and
overtops the anthers to the last; it may either lie above the latter
(3,. Fig. 152) or project at the side (4, Fig. 152). In this case, the
stigma can only receive pollen by the aid of insects, and from other
(either older or younger) flowers. Although this difference seems
in general to depend upon the sunny or shady character of the
spot, other unknown conditions (perhaps heredity) must co-operate ;
for I have sometimes observed in the same spot, and even on the
same plant, flowers which fertilised themselves, and others incapable
of doing so.

An imperfection in the flowers deserves special mention. The
upper lip, as the figure shows, projects so slightly that the anthers
in great part protrude beyond it and are unprotected. This is
sometimes the case to such a degree that bees thrust their tongues
into the flower above the stamens, and thus suck honey and shake
out the pollen without leading to fertilisation.

I have only seen bees visiting this plant.

(1) Apis mellifica, L. 9, very ab., thrusting its proboscis into the flower
usually below the stamens, but sometimes above them,—it inserts its proboscis
even into young unexpanded flowers, with long exserted styles ; (2) Bombus
lapidarius, L. 9 9, s.; (3) B. silvarum, L. 2 9, s.

PART IIL. | THE MECHANISMS OF FLOWERS. 447

331. ODONTITES LUTEA, Rchb. (Rehmberg, near Miihlberg,
Thuringia).—Honey is secreted by the smooth lower half of the
ovary, which is hairy above; it lies in the base of the corolla-
tube, which is 2} mm. long, and is smooth within, but provided with
reflexed hairs at its mouth. The stamens stand apart, but from
the small size of the flower they are all easily touched at the same
time by an insect ; there is no provision of hairs to prevent scatter-
ing of the pollen; the slits by which the anther-lobes dehisce are
narrower than in Luphrasia officinalis. The style often protrudes
from the bud (3, Fig. 153), and Hildebrand describes the flower as
proterogynous; in other cases it is bent backwards in the bud,
under the lower lip, and emerges together with the stamens on
the opening of the flower. The stigma comes to maturity at the

Fic. 153.—Odontites lutea, Rehb.

1,—F lower, from the side (x 8}.
2.—Ditto, from the front.

‘ 3.—Bud, from the side.
4.—Anther.

same time as the anthers, and stands below and in front of them;
it is, therefore, usually touched first by insect-visitors. In ab-
' sence of insects, some pollen generally falls upon the stigma. I
have only once (August 28, 1869) seen a bee, Bombus muscorwm,
| IL. 8, sucking honey on the flower.
Luphrasia minima, Schleich., is sparingly visited by insects, and
in their absence it fertilises itself regularly. The flower resembles
. in structure the small-flowered form of Z. officinalis (t.e. E. gracilis,
} Jord.) (609).
332. EUPHRASIA OFFICINALIS (L.), Schk.—Honey is secreted
i. and sheltered as in Odontites serotina. The tube of the corolla is
_ 4 to 6 mm. long, but widens considerably at the outer end ; so that

iT
Ps

448 THE FERTILISATION OF FLOWERS. [PART III.

an insect with a proboscis less than 4 mm. long can reach the
honey by thrusting its head into the wide part of the tube.

The upper lip forms a vaulted roof over the stamens; it shelters
the honey at the base of the tube from rain, and prevents an in-
sect's proboscis from being thrust in above the stamens, as was
possible in Odontites serotina. The three-lobed under-lip forms a
convenient landing-place for the smaller visitors, and affords foot-
hold for the forelegs of larger ones. An orange spot on the under
lip, another at the entrance of the tube, and dark violet lines con-
verging towards the mouth on both upper and lower lips, serve as

Fic. 154.—Euphrasia officinalis, L.

1.—Flower of the small-flowered form, seen from the front (x 7). .

2.—The two stamens of the right half of the flower, from the outer side.

3.—Ditto, more magnified, from the inner side. ; .

4.—Flower of the large-flowered form, just after ima from the side (x 34). A

a, stigma; b, upper half of the upper anther ; c, lower half of the upper anther connected with
the upper half of the lower; d, lower half of the lower anther ; e, style.

pathfinders. As in Odontites serotina, the pollen is smooth and
powdery, and falls on the head or proboscis of the visitor; but the
details of the process by which the pollen is scattered are unlike
those of the former species. While in Odentites serotina the
anthers are only held together posteriorly by matted hairs, in 4.
officinalis the lower anther-lobe of the upper stamen on each side
coheres with the upper anther-lobe of the lower; and the two
superior anthers further cohere firmly together. Another peculi-
arity is directly connected with this. While in Odontites serotina

PART III. | THE MECHANISMS OF FLOWERS. 449

all the anther-lobes end alike in short points, in Z. officinalis the
upper lobe of each anther is blunt, but the lower is provided with
a thin, stiff spine (3, Fig. 154). Of these four spines it is almost
exclusively the two lower ones that come in contact with insects;
for not only are they much longer than the upper ones, but the
stamens which bear them are inclined at an angle of about 60°
from the upper pair, and their anthers bend downwards so much
that the spines stand well down in the mouth of the flower (1,
Fig. 154). In Odontites serotina the pointed anther-lobes must
themselves be touched for the pollen to be shaken out, and the
broad filaments, placed close together and set with sharp points on
their inner side, insure this, In JZ. officinalis, on the other hand,
it is sufficient if one of the long spines on the lower anthers be
touched, and accordingly the filaments curve widely apart, standing
close to the wall of the corolla; and they are smooth and narrow,
so that an insect can insert its head into the tube without hindrance.
In doing so it touches the lower anther-spines, and shakes the whole
system of anthers, causing the pollen to fall out. Rows of hairs
on the upper anther-lobes prevent the pollen from being scattered
at the sides, and insure its falling on the head of the insect.

In the points described hitherto all my specimens of L. officinalis
agree with one another. But in regard to the size and conspicu-
ousness of the flowers, and the possibility of self-fertilisation, I
have found two different forms of this plant—one large-flowered,
which never fertilises itself, and one small-flowered, which in
absence of insects fertilises itself regularly. Intermediate forms
may probably occur, but were not present among my specimens.

In the large-flowered form (4, Fig. 154), probably £. montana,
Jord., the stigma protrudes from the flower before the anthers are

| ripe, and even after the anthers are ripe it is the first part to be

touched by insect-visitors, and is, therefore, regularly cross-fertilised ;

' in absence of insects, it is incapable of self-fertilisation.

In the small-flowered form, probably #. gracilis, Jord. (1,
_ Fig. 154), when the flower opens, the stigma stands so far above
and behind the anthers that it escapes being touched by insccts ;
__.the style gradually elongates and carries the stigma downwards
and forwards into a position where it will be touched before the

anthers by an insect’s head, and where, in absence of insects,

_ pollen can fall from the upper anthers upon it.

i, Thus in case of insect-visits cross-fertilisation is insured m both
forms, but in absence of insects self-fertilisation is only possible in
_ the small-flowered plants.
Ge

450 THE FERTILISATION OF FLOWERS. [PART III.

Delpino (178) seems to have examined the large-flowered form
only, and Axell (17) the small-flowered ; for the former describes
E. officinalis as proterogynous, and the latter as proterandrous.

Visitors: A. Hymenoptera—Apide: (1) Bombus agrorum, F. $; (2) B.
pratorum, L. %; (3) Apis mellifica, L. $ ; (4) Nomada lateralis, Pz. 9, all s.
B. Diptera—(a) Bombylide : (5) Systcechus sulfureus, Mik. (Sld.) ; (6) Syr-
phide: (6) Syrphus sp.; (7) Melithreptus teniatus, Mgn., all s. Additional
lists of visitors to the large-flowered form are given in No. 590, IL, and
No. 609.

Huphrasia salisburgensis, Funck.—The flowers resemble in size
the small-flowered form of £. officinalis, and their arrangements
for cross-fertilisation resemble the large-flowered form of that
species. The corolla continues to grow, carrying forward the
stamens after the style has stopped growing, and in absence of
insects self-fertilisation takes place in the end. The visitors are
bees and Lepidoptera (609).

333. PEDICULARIS SILVATICA, L.—In this plant, as in Rhinan-
thus and Melampyrum, the opposite pairs of anthers lie with their
edges close together,—and all four unite to form a quadrangular
pollen-receptacle (3, Fig. 155) which is inclosed in the hooded upper
lip. The mechanism by which pollen is shed upon the insect-
visitor is here more complex and more rich in adaptations than
ever, and more difficult to understand in its details without direct
observation of its action. Sprengel (702) and Hildebrand (346),
neither of whom observed insects in the act of fertilising the
flower, have very naturally overlooked many of its most interesting
adaptations. Dr. Ogle (632), who watched the flowers in the open
air and saw them visited by humble-bees, gives an accurate
account of the process of cross-fertilisation ; but many adaptations
have escaped even his notice, and some he has interpreted
wrongly. It is therefore still worth while to describe the whole
structure of the flower minutely.

Honey is secreted by the green, fleshy base of the ovary, and
lies at the bottom of the tube, which is 10 to 14 mm. long, laterally
compressed, and so narrow that a humble-bee can only insert the
forepart of its head. At the height of 10 to 14 mm. the tube
divides into an upper lip, which both in form and in direction is
simply a continuation of the tube, slightly wider and open in
front, and an under lip, whose base (8 to 5 mm. long) is applied
to thie upper lip so as to close up the lower 3 to 5 mm, of the

PART III. | THE MECHANISMS OF FLOWERS. 451

_ mouth of the flower. The hooded end of the upper lip incloses
_ the stamens, and the end of the style with the stigma protrudes
obliquely downwards from it; the free portion of the under lip
_ with its three lobes serves as a standing-place for insects, and is
_ Set very obliquely, so that the right lobe stands 2 to 8 mm. higher

Fig, 155.—Pedicularis silvatica, L.

1.—Corolla, from the front.

2.—Flower, from behind,

_ 8.—Upper part of the corolla, from the left side. The left half of the corolla has been cut
away, and the anthers have been pushed asunder.

_ 4,—Transverse section of the corolla atc, 1,2. (1—8, x 3}; 4, x 7.)

a, point of insertion of the anterior stamens ; b, point of origin of the lower lip; bc, lower part
__ of the mouth of the flower, closed by the apposition of the lower lip ; d, revolute edge of the upper
lip, set with teeth; e, widest part of the mouth into which the bee inserts its head and proboscis ;
Ff, the hood which surrounds the anthers; g, pendulous tip of the hood; h; ridge upon the side of
the corolla, meeting the revolute border at e; k, shorter, 1, longer stamens.

_ than the left (1, Fig. 155). If the under lip is pulled down as far
as the place of its attachment, the mouth of the flower is seen to
form a fissure 8 to 10 mm. long, which in the greater part of its
length is only 1 to 2 mm. broad, but which 3 mm. below its upper
end widens out suddenly to a breadth of 4 mm, (¢, ¢, 1); it then
. GG 2

452 ‘THE FERTILISATION OF FLOWERS. [PART III,

again narrows suddenly, and a little more than 1 mm. from its
upper end two sharp processes of the hood (g, 1, 2) almost meet
in the middle and divide the entrance into a very small upper and
a long lower part. Through the upper opening protrudes the —
style, which springing from the bilocular ovary lies close to the
posterior wall of the corolla, and curves sharply downwards near —
its anterior end to bear the capitate stigma; the long, lower
opening admits the bee’s head. So long as this slit is only 1 to 2
mm. broad, viz., from the insertion of the under lip to the wider
part above, its edges are very markedly rolled outwards, and that
part of the inner wall of the corolla which is brought by this
evolution of the edge to form the margin of the narrow slit is
closely set with sharp points (d, 1, 2, 4), while the wider portion
(ce, 1) has smooth edges. There is also on each side of the upper
lip a reddish thickened band (h, 2), which begins on a level with
the wide part of the slit at the upper end of the evoluted edges
(e), and forming a sharp angle with the ridge runs backwards and ©
downwards to disappear on a level with the base of the under lip.
What have all these characters, the compressed base of the
under lip, the oblique position of its three-lobed lamina, the
evoluted edge of the narrow entrance, its rough edges, the sudden
enlargement with its smooth edges, the red stripes at the sides —
of the upper lip, to do with fertilisation by humble-bees? Are
they accidents to be neglected, as is done by Hildebrand in his —
figures in the Botanische Zeitung (1866, pl. iv.) and by Dr. Ogle
in the Popular Science Review (Jan. 1870)? Careful observation
of an insect visiting the flower makes me think otherwise. The
bee comes flying along with outstretched proboscis, and avoiding
the toothed edges of the slit, thrusts its proboscis at once in
alighting into the widest part of the opening (e, 1); the upper part
of its head then touches the stigma, which stands scarcely 2 mm.
above the wide part of the opening, and the oblique position
of the lower lip causes the bee’s head also to be placed obliquely ;
its forefeet grasp the basal part of the lower lip, its middle pair
of feet grasp the tube of the flower on a level with the lower lip,
and the hindfeet rest upon leaves or other flowers below. Standing
in this position, the bee applies its head, which is 24 to 3 mm.
thick and 5 mm. broad, to the (4 mm.) wide part of the entrance,
with just so much obliquity as gives it the best chance of entering.
And now the edges of the slit, rolled outwards and thereby stiffened
(d, 1,2), and the bands on the upper lip (A, 2), play their part. -
Joining above at a sharp angle, they bound, on each side of the—

PART I11. | THE MECHANISMS OF FLOWERS. 453

upper lip, a triangular surface, which does not bend, but gets
pushed outwards by the bee’s head. But the points where the
evolute edges and the thickened bands meet are on each side of
the-wide part of the opening, and as they separate more and more
from one another, the superior angle (¢, g, e, 1) of the small part
of the entrance above this will be very greatly enlarged, for the
sides bounding it are very short, and are forced apart as much
as the long sides of the lower opening. The small processes (g, 1, 2)
which before nearly met, and which held together the two halves
of the pollen-receptacle, are forced apart; the anthers, which have
a tension outwards in consequence of the peculiar curvature of
their filaments (4, 7, 3),1 are freed from the force that held them
together below, while they remain fastened together above ; they
therefore flap apart, and let a little pollen fall on the bee’s head,
exactly on the spot which came in contact with the stigma scarce
a second before. The pollen is saved from being scattered at the
sides by vertical hairs on the longer stamens (/, 3),? which cover
the space between the upper and lower anthers on each’ side, and
project slightly beyond the lower edges.

Bombus hortorum, L. 2 (20 to 21 mm.), needs to thrust its head
a very little way down after inserting it into the wide entrance ;
but the shorter a bee’s proboscis is the more must it force its
head down in the upper lip, and if there is not space enough above
the platform of the lower lip, the latter can be pressed down
3 to 4 mm., as far as b, 2; so that bees with a proboscis only
10 mm. long may reach the honey. When the bee flies away, the
lower lip springs back into its former position, and the whole
mouth of the flower resumes its original state.

The flower is in this way adapted for all our native species
of Bombus and Anthophora, except B. terrestris and small workers
of a few other species; but the length of the tube excludes all
smaller bees, which if the tube were shorter might carry off the
honey without touching the stigma; the hooded upper lip guards
the pollen from flies and other insects; but the tube is liable
to be bitten through and robbed of its honey by some humble-
bees. Such robbery does little or no harm, for bees still visit

1 T have never noticed the anthers adhering at all to the inner surface of the
cain as Dr. Ogle describes. Such an adhesion, if it exists, must be very slight
indeed.

* According to Dr. Ogle (No. 632, p. 46), the lower anthers are held together by
the pressure of these hairs upon the wall of the corolla. To act in this way the
hairs would have to be directed obliquely outwards, They are not so, but lie parallel
to the median vertical plane of the flower. .

8 Dr. Ogle is mistaken in thinking (No. 632, p. 180) that the wide calyx is suffi-
cient to protect Pedicularis silvatica from robbery on the part of short-tongued bees.

454 THE FERTILISATION OF FLOWERS. [parr m1.

in a legitimate manner flowers which have been bitten through

and robbed.
The power of self-fertilisation has been completely lost.

Visitors: Hymenoptera—Apide: (1) Anthophora retusa, L. ¢ (16—17) ;
(2) Bombus hortorum, L. 2 (20—21) ; (3) B. agrorum, F. (12—15) ; (4) B.
lapidarius, L. 9 (12—14); (5) B. silvarum, L. ?( 12—14) ; (6) B. Scrim-
shiranus, L. 9 (10), all sucking normally, very ab.,—B. Scrimshiranus, L. §
(9), bites through the corolla close above the calyx, and so reaches the honey ;
(7) B. terrestris, L. 2 (7—9), very ab., only reaching the honey by biting,—
once I saw it gnawing the upper lip, above the anthers,

Pedicularis rostrata, L., P. verticillata, L., P. tuberosa, L., were
seen by Ricca to be visited by humble bees (665). On the Alps,
I have observed in addition to these three species, P. palustris, L.,
P. recutita, L., P. asplenifolia, Floerke, and P. foliosa, L. (609). In
P. verticillata, the calyx is swollen, and the lower part of the
corolla-tube is bent at right angles within the calyx; the honey
is thus guarded from Bombus mastrucatus, which tries in vain to
reach it, and which frequently bites through the tubes of P. tuberosa
and P. foliosa, ete.

The six species of Pedicularis which grow in Nova Zembla are
all fertilised, in Delpino’s opinion, by Bombus terrestris, and so also
is P. Kanei, which is found in lat. 79°, on the west coast of Green-
land (172, 352). If this is really the case, all these species must
have a shorter tube than P. szlvatica.

334. RHINANTHUS CRISTA-GALLI, L.—lIn this plant, as in the
foregoing, the dry smooth pollen is shed on the insect’s head, but
the details of the mechanism are very different. Hach anther lies so
close to its opposite neighbour, and they dehisce so widely on their
opposed faces, that both together form one pollen-reservoir, closed
in by matted hairs with which the contiguous edges of the anthers
are provided (1, 2, Fig. 156). These pollen-reservoirs are borne
on stiff filaments, of which the anterior pair are close together at
their bases, and are beset with sharp points on their inner sides (1)
so that a bee cannot insert its proboscis there; higher up, for the
space of a few millimetres below the anthers, they are smooth and
wide enough apart to admit the point of a bee’s proboscis easily.
As soon, however, as the bee pushes its proboscis farther in, it
forces the filaments apart, and tears asunder the two halves of the
pollen-reservoir. The pollen falls out on to the bee’s proboscis,
and is prevented from being scattered at the sides by the fringe of
hairs on the lower edge of the anthers, This pollen-mechanism is

PART III. | THE MECHANISMS OF FLOWERS. 455

better protected than in the foregoing species, for the helmet-
shaped, laterally compressed upper lip covers it both above and at
the sides, and at first leaves only a narrow slit, which is slightly
more dilated just below the anthers to admit the bee’s proboscis.
Honey is not secreted by the ovary itself, but by a development of
the receptacle, which is prolonged downwards and forwards into a
long, fleshy lobe, turned up at the edges (w, 4). As in Huphrasia
officinalis, so also inthis plant, two different forms exist,’ one incon-
spicuous and regularly self-fertilising, the other more conspicuous

Fic. 156.—Rhinanthus erista-galli, 1.

1.—Anthers, from the front.
2.—Ditto, with the style, from the side.
8.—An anther, from the inner side.
4.—Ovary, with the base of the style, nectary (n), and base of the corolla (co).
5.—Flower, of the variety minor, after removal of the right half of the calyx, from the side.
6 —Upper part of ditto, at the beginning of the flowering period, from the front.
7.—Ditto, at the end of the flowering period.
8.—Style of the variety minor.
9.—Style of the variety major.
(i—3, x 7; 4—9, x 3h)

and incapable of self-fertilisation. Delpino, who has thoroughly
described the mechanism of this flower, has only had the larger
form (major) under examination ; for he calls Vaucher’s fairly
accurate account (752) of the occurrence of self-fertilisation,
_ merely a product of the imagination.”

. R. minor, Ehrh.—In the small-flowered form, the tube, whose
base contains the honey, is 7 to 8 mm, long, so that the honey is

ie 1 Linneus distinguished these as varieties (a and B). Later authors have advanced .
| them to the rank of species, R. major, Ehrh., and R. minor, Ehrh.
2 No. 178, p. 183, ‘‘ Ora tutto cid non é che un parto della imaginazione.”

456 THE FERTILISATION OF FLOWERS. [PART III.

accessible to all our humble-bees, the shortest proboscis among
which, that of B. terrestris, is 7 to 9 mm. long. The mouth of the
corolla is a slit 6 to 7 mm. long, which, however, is reduced to 4
mm. by the position of the upper lip. The remaining posterior part
of the slit is blocked by the stamens in the manner already described,
so that the bee can only insert its proboscis beneath the anthers.
The stigma curves down so far over the anthers (6, Fig. 156)
that an insect’s proboscis must touch it before entering further and
being dusted with pollen. In general, however, bees’ visits are
scarce ; for the corolla is almost inclosed in the vesicular calyx,
and is therefore inconspicuous. In absence of insects, self-fertilisa-
tion always takes place; for the mouth of the corolla gradually
opens more widely, the under lip bending downwards, and the sides
of the upper lip spreading further apart (7, Fig. 156); at the
same time the style elongates and curves downwards and inwards
(7, 8), so that the stigma comes to stand under the anthers, or
even between them if they have separated in withering.

f, major, Ehrh.—In the large-flowered form, the tube is about
2 mm. longer than in the small-flowered ; but this small difference
suffices to exclude many of our humble-bees from the honey, or to
cause them to bite a hole in order to gain access to it. Sprengel
observed these holes, but they are not made, as he said, by “a
large humble-bee, for whom the natural entrance is too small,” for
all humble-bees insert only their proboscis into the flower ; but by
those with the shortest proboscides, namely, as I have repentant
observed, by B. terrestris, L. 9 and §, and Bb. pratorum, L. %,
whose proboscides measure respectively 7 to 9 mm. and 8 mm.

The size of the parts projecting beyond the calyx, viz. the
upper and lower lips, differs more than the length of the tubes in
the two varieties or sub-species. The upper lip is in &. minor 7
to 8 mm., in &. major 10 to 11 mm. long. The flowers of 2. major
are therefore more conspicuous, and their conspicuousness is in-
creased by the pale colour of the bracts and by the violet colour
of the tip of the upper lip, which is usually white in &. minor.
As both species grow together in the same spots and flower at the
same time, they give a good opportunity of proving that the large-
flowered form is really much more plentifully visited than the
other. In point of fact, insect-visits are so plentiful in the case of
R. major, that it has been able to dispense with the power of self-
fertilisation, and the style, instead of bending downwards, projects
more and more from the mouth of the flower.

We have thus in Rhinanthus major and minor two forms

PART III. | THE MECHANISMS OF FLOWERS. 457

engaged in the struggle for existence ;+ the one excels in conspi-
cuousness and the abundance of its insect-visitors, the other in its
power of self-fertilisation, The former seems to have the advan-
tage, for both in Westphalia and, according to Ascherson’s Flora, in
Brandenburg it is much more plentiful than the smaller form; it
is also more plentiful both in England and Ireland according to
Mr. T. H. Corry.
The following list includes the visitors to both forms :—

(1) Bombus (Apathus) Barbutellus, K. 9 (12); (2) B. Rajellus, Ill. 9
(12—13) ; (3) B. hortorum, L. 9 9 (19—21) ; (4) B. silvarum, L. 2 $ (10O—
14) ; (5) B. senilis, Sm. 9 $ (14—15) ; (6) B. Scrimshiranus, K. § (10) ; (7)
B. hypnorum, L. § (10—12), all only sucking normally ; (8) B. terrestris, L.
2% (7—9), (9) B. pratorum, L. § (8), both sucking normally on R. minor,
but obtaining the honey of &. major by biting a hole in the spur.

Several of the above-named humble-bees were caught carry-
ing Rhinanthus pollen in their collecting-baskets,—viz. B. terrestris,
? §%, and in especial numbers (in the Hoppekethal, July 11, 1869),
B. hypnorum, %, and B. pratorum, 3. Sprengel mentions the
honey-bee as a frequent visitor, but I have never observed it; its
proboscis (6 mm. long) is at any rate too short to reach the honey
in the legitimate manner.

I have seen one of the Noctuids, Huclidia glyphica, L.,
repeatedly sucking the honey of this flower; but the tongues of
Lepidoptera are so thin that they can reach the honey without
pushing the anthers apart, and Lepidoptera therefore are quite
useless to the plant. :

In Rhinanthus Alectorolophus, Poll.,? we have an intermediate
stage between R. crista-galli and R. alpinus. The corolla is produced
into a beak-like prolongation close under the projecting stigma,
and above the entrance made use of by bees; this process of the
corolla bears a small opening, bounded by two blue lobes. This
small opening permits Lepidoptera to insert their thin tongues, which
touch first the stigma and then the anthers; and as a matter of
fact this species is visited and cross-fertilised both by Lepidoptera
and by humble-bees (570, 609).

In Rhinanthus alpinus, Brng., the lower or bees’ entrance is
closed, its edges coming close together without uniting, and only
the small upper opening remains; and this species is therefore

1 Compare Malva rotundifolia and M. silvestris, p. 142.
2 Included by Nyman, Conspectus Flore Europe, under R. major.

458 _ THE FERTILISATION OF FLOWERS. [part 111.

adapted solely for Lepidoptera; but it is much visited by humble-
bees, who force open the flower to steal the pollen, and sometimes,
but less frequently, the honey (570, 609).

Tozzia alpina, L.—The bright yellow flowers are visited by
numerous flies. Stigma and anthers ripen simultaneously. At
first the stigma stands far in front of the anthers, but afterwards
the growth of the corolla carries forward the stamens until the
anthers lie well in front of the stigma (609).

Fig. 157.—Rhinanthus Alectorolophus, Poll.

A.—Flower, in longitudinal section, after removal of the calyx.

B.—Upper part of a flower, from which the right half of the corolla has been removed.
C.—Ditto, viewed from the front.

D.—Ditto, after removal of the lower lip. (x 34.)

hth, aperture for humble-bee’s proboscis ; fth, aperture for butterfly’s tongue.

nN, nectary ; ov, ovary ; st, stigma.

(St. Gertrud, July 22, 1875).

335. MELAMPYRUM PRATENSE, L.—The contrivance by which
the pollen is shed in Melampyrum is again different from all the
foregoing ; for here all the four anthers lie close together and form
a single pollen-reservoir, which is opened by touching the pointed
appendage borne by each anther-lobe. The flower exhibits several
other remarkable peculiarities. Honey is secreted by the base of
the ovary, which expands opposite the under lip into a white, round,
fleshy body, on each side of which runs a honey-secreting groove.
The abundant honey fills 2 to 3 mm. of the tube, which is 14
to 15 mm. long, and stands horizontally ; it is protected from rain
by a ring of hairs, pointing forwards and placed immediately in
front of it. In order to suck the honey in the normal way, and
without thrusting its head into the tube, an insect must have a
proboscis 14 to 15 mm. long; so that the greater number of our
humble-bees are excluded. But at its anterior end, for 4 to

PART IIL. | THE MECHANISMS OF FLOWERS. 459

5 mm., the tube is so wide that a humble-bee’s head enters it
easily; a proboscis 10 to 11 mm. long therefore suffices, and
only B. terrestris and small workers of some other species are
excluded.

In its narrower part the tube is three-sided, the lower wall
standing horizontal, the sides first bending sharply inwards then
rising almost perpendicularly, and holding the style in their upper
angle. All three sides widen out gradually for a space of 8 to 10
mm. from the base of the tube, then, on a sudden, more rapidly,
the sides rising up into a hood for the pollen-reservoir, and the
floor increasing from 3 mm. to 5 mm. in breadth. In this wide
part of the tube the lower part of the side walls is doubled down
upon the floor by a re-entrant fold (a, 2, 3), so that the breadth
of the entrance is reduced to scarcely 3 mm.; and this is further
reduced in height to 1 to 2 mm. by two dark-yellow pouches in the
under lip (pathfinders, b, 3), and by a fold close behind the free
edge of the hood-like upper lip; if, however, the folds in the side
walls and in the upper lip are opened out by a bee thrusting in its
head, there is plenty of room in the broad part of the tube for the
bee’s head, which is about 5 mm. broad, and 3 mm. high. So by
this peculiar conformation of the mouth, weak, short-lipped insects
are excluded, and at the same time humble-bees are permitted
to insert their heads. There are yet other peculiarities in the
mouth of the flower which complete this result. The filaments
which, in the narrow part of the tube, are thin and adhere to the
corolla, become free from it in the wide part, and rise obliquely
upwards as stiff, broad rods beset with teeth on their inner sides,
towards the hooded upper lip, which incloses the stamens. The
two anterior stamens lie, in their ascending portions, so close
behind the entrance of the flower that they block it for a further
space of } mm. on either side. So in looking from the front into
the mouth of the flower we see an opening only 2 mm. broad and
scarcely so high, bounded on the right and left by the prickly
margins of the filaments, above by the soft. tufts of hairs on the
upper lip, and by the weak hairs projecting downwards from the
pollen-receptacle (d, 3). The bee in inserting the delicate tip of
its proboscis carefully avoids any rough contact ; therefore, in this
flower, it directs it neither to the right or left, where it would
meet the sharp points upon the stamens, but upwards where it
rubs against the soft hairs of the upper lip and the pollen-
receptacle in passing into the tube. This course is essential for

| eross-fertilisation,

460 THE FERTILISATION OF FLOWERS. [PART III.

The style traverses the upper angle of the tube in its whole
length, and bends down with it over the pollen-receptacle, so that
its stigmatic end hangs down in the upper part of the mouth of
the flower between the tufts on the upper lip, and is thus in-
evitably touched by the bee’s proboscis as it enters. The four

Fic. 158.—Melampyrum pratense, L.

1.—Flower, from the side (x 8).
2.—Ditto, from above.
8.—Ditto, from the front (x 7).

4.—The pollen-receptacle formed by the anthers, viewed from behind.
5.—Ditto, after it has opened, from before.

6.—The two anthers of the right half of the flower, seen from the left.
7.— Relative positions of pollen-receptacle and stigma.

a, side-fold in the forepart of the corolla; b, pathfinder; c, stigma; d, hairs of the pollen
receptacle ; e, teeth upon the filaments ; 7, appendages of the anthers.

pairs of anther-lobes, which have stiff walls and are in firm
connection with the stiff filaments, cohere closely by their upper
and posterior edges, but admit of some motion at their lower
and anterior edges, which are fringed with hairs. Each anther-
lobe is prolonged downwards into a stiff, sharp process, so that
four pairs of these sharp processes point downwards; of these

PART III. | THE MECHANISMS OF FLOWERS. 461

the hindmost are the longest, as they might easily escape being
touched if of the same length with the others. The bee’s pro-
boscis, entering the flower in the way described above, comes in
contact immediately afterwards with the sharp processes of the
anthers; the anther-lobes at once separate slightly at their lower
and anterior edges, and the fine, dusty pollen is shed upon the
insect’s proboscis.

In spite of these manifold adaptations, the plant, from growing
in shady spots, is, as a rule, sparingly visited by bees ; but in their
absence self-fertilisation takes place regularly. As in Rhinanthus
minor, the end of the style curves more and more downwards, and
at last inwards, so that the stigma comes to lie below the pollen-
receptacle (5, Fig. 158), which in the old flower opens of itself.
In flowers whose colour has changed to reddish the stigma is
always found in this position.

Visitors : Hymenoptera—A pide : (1) Bombus agrorum, F. § ? ! (10—15),
sucking normally. Its weight bends down the flowers to which it hangs, It
first inserts the tip of its proboscis into the upper part of the flower, then
thrusts the whole proboscis and its head into the tube. After visiting a flower,
which takes only a few seconds, it almost always flies away to a neighbouring
plant. (2) B. hortorum, L. % ! (18—20), sucking normally, just as the former
species (Siebengebirge, July 8, 1871); (3) B. terrestris, L. 2 (7—9), bites
through the corolla close above the calyx, so that one mandible makes a hole
on each side of the sharp edge of the corolla, and through one of these two holes
the bee inserts its proboscis ; (4) B. pratorum, L. § ¢ (8—9), acts similarly
(Siebengebirge, July 8, 1871) ; (5) Apis mellifica, L. § (6), do., very ab. ; (6)
Megachile circumcincta, K. 9! (11), sucking normally, only one specimen.
B. Diptera—Stratiomyide : (7) Oxycera pulchella, Mgn., I saw this species on
the flowers at Warstein,—it probably could not reach either the honey or
the pollen. See also No. 590, 11.

Melampyrum arvense, L., is visited by various insects, but only
fertilised by very long-tongued humble-bees (590, II).

Melampyrum nemorosum, L.—The honey is stolen by various
humble-bees, but the flower is fertilised only by Bombus hortorum,
L. 8 (590, III.).

Melampyrum silvaticum, L.—The flower is of small size and its
mechanism is much simplified (590, II.).

The six forms above described in which dry pollen is shed on
the insect-visitor, viz. Odontites lutea, O. serotina, Kuphrasia offi-
cinalis, Melampyrum, Rhinanthus, and Pedicularis, show remarkable
gradations in the way in which the anthers are protected and the

462 THE FERTILISATION OF FLOWERS. [PART III.

pollen lodged, and in the mechanism for scattering the pollen and
for guiding the insect’s proboscis.

a. The protection of the anthers. In Odontites lutea the
anthers protrude from the flower, as in Veronica; in Odontites
serotina they are only slightly covered by the upper lip, while they
are entirely covered by it in #. officinalis ; in the three others they
are completely inclosed in the hood of the upper lip.

b. The pollen-receptacles. In the two species of Odontites
and in Huphrasia officinalis each anther-lobe forms a separate
receptacle opening at the apex; in O. lutea all the anthers are
separate ; in O. serotima they are connected posteriorly by matted
hairs; in &. officinalis their edges cohere. In Melampyrum,
Rhinanthus, and Pedicularis, their edges are closely united so as to
form a single, more or less distinctly four-chambered receptacle.

c. The shedding of the pollen.. In QO. lutea and O. serotina
the anthers must be touched in order to shed their pollen; in
O. lutea each must be touched separately, but in O. serotina
one touch is communicated to all. In LZ. officinalis the lower
anthers, in Melampyrum all of them, bear sharp appendages which
point downwards, and which, when touched, cause the pollen to
fall out. In Rhinanthus, the pollen-receptacle is opened by
pushing apart the filaments. In Pedicularis, the edges of the
hood which incloses the pollen-receptacle are separated by a
complex system of levers, and the pollen-receptacle then opens.
In all, except O. lutea, hairs directed downwards (either from the
edges of the anthers or from the filaments) prevent the pollen
being scattered at the sides,

d. The path of the bee’s proboscis. In 0. lutea and L. officinalis
the path is only marked out by the entrance of the tube ; but in
O. lutea the bee’s proboscis cannot fail to come in contact with one
or other of the anthers, and in J. officinalis with their appendages.
In the other four species sharp points on the filaments or on the
edges of the upper lip cause the bee to insert the tip of its
proboscis just in such a position that it may first touch the stigma
and then dust itself with pollen.

In regard to all four characters Odontites lutea stands lowest,
and Pedicularis silvatica highest.

Cross-fertilisation in case of insect-visits is insured in all the
six species by the stigma being touched in all or most flowers
by the same part of the insect which is immediately afterwards
dusted with pollen. In three species out of the six, two forms of
flowers occur, of which one is sparingly visited by insects and in

PART III. | THE MECHANISMS OF FLOWERS. 463

their absence fertilises itself regularly, and the other is abundantly
visited by insects and is incapable of self-fertilisation. In Huphrasia
officinalis and Rhinanthus crista-galli it is the small-flowered form,
in Odontites serotina it is the plants inhabiting shady places, which
receive so few insect-visits that self-fertilisation becomes necessary ;
in Melampyrum and Odontites lutea self-fertilisation occurs in
absence of insects, but in all flowers without distinction; in
Pedicularis silvatica alone, the conspicuousness of the flowers and
the perfection of the pollen-apparatus insures cross-fertilisation so
well that self-fertilisation never takes place.

The section of the Scrophularineze characterised by a pollen-
distributing mechanism is remarkable also for the gradations in the
development of its -nectaries. Usually part of an organ already
present secretes honey, especially the lower part of the outer wall of
the ovary, which sometimes secretes its honey all round (Zozzia),
sometimes mainly or solely in front (Huphrasia and Odontites).
With the growth of this new function the secreting tissue
thickens and forms a protuberance scarcely noticeable in Huphrasia
minima, but evident in #. salisburgensis and Pedicularis aspleni-
folia, Fl.; it becomes a strongly marked swelling in P. verticillata,
L., and P. recutita, L., which in P. palustris, L., is more sharply
marked off from the ovary, and in Rhinanthus becomes a cup
extending forwards from the base of the ovary, which contains
the nectar, and is most perfectly developed in &. alpinus. We
thus have a complete series of transitions, from secretion of honey
by an organ whose proper function is quite different, to the
development of a special nectary.

REVIEW OF THE SCROPHULARINE,

The Scrophularinez described above may be arranged in four
groups according to their pollen-distributing mechanism and the
insects which fertilise them.

1. Verbascum and Veronica have open flowers, with short tubes
and freely exposed reproductive organs which insect-visitors may
come in contact with at any part, though they as a rule touch the
stigma before the anthers. Only in some Veronicas, especially in
V. Chameedrys, the filaments by spreading apart and thinning away

464 THE FERTILISATION OF FLOWERS. [PART III.

at the base form a delicate pollen-distributing apparatus. The
fertilisers are flies and bees.

2. Scrophularia has short, round, brownish flowers, with a
widely open mouth and easily visible honey. The stigma ripens
before the anthers, and both come in contact inferiorly with the
insects. Wasps are the chief fertilisers.

3. Digitalis, Antirrhinum, and Linaria have long and wide
tubes, open in Digitalis and closed in the other two. The insect-
visitor creeps entirely or almost entirely into the tube, and touches
anthers and stigma with its back. The fertilising-agents are large
bees.

4. Euphrasia, Odontites, Rhinanthus, Melampyrum, and Pedicu-
laris have narrow tubes which divide into an upper lip protecting
the anthers, and a lower lip serving as a platform for imsects to
alight on. They dust their insect-visitors with smooth, powdery
pollen. The forms with shorter tubes are fertilised by bees and
flies, those with longer tubes almost exclusively by humble-bees.

On the Alps we have in addition TYozzia, fertilised by flies,
Rhinanthus Alectorolophus by humble-bees and Lepidoptera, and
R. alpinus by Lepidoptera (609).

In almost all the Scrophularinez that we have considered,
cross-fertilisation is effected by the stigma being touched before
the stamens or pollen-apparatus by insect-visitors; but in some
cases dichogamy also occurs. In default of insect-visits, self-fertili-
sation takes place in most forms; and only in a few are insect-
visits, and consequently cross-fertilisation, so far insured that self-
fertilisation is never required and has become impossible.

This family affords another instance of the association of certain
colours with fertilisation by certain insects. In the section charac-
terised by loose dry pollen, the lowest forms (Zozzta, Odontites
lutea, and Euphrasia minima) are all yellow, while in the highest
(Melampyrum, Pedicularis) red and purple colours appear. The
uncommon colour of Serophularia must be referred to the peculiar
taste of its visitors, the wasps. The colours of the genus Veronica,
which is fertilised by flies, remain to be explained. Most species
have light or dark blue flowers; those of V. urticifolia, and V.
peregrina, L., are pink. In spite of its apparently simple flower,
Veronica is by no means a primitive form among the Scrophu-
larinee : the symmetrical flower, the specially differentiated
nectary, the reduction of the sepals and petals to four, and of the
stamens to two, are all characters widely removed from the
primitive type. The short-tubed species of Veronica must be

structure and development of the flower. Hildebrand has ex-
_ plained the mechanism of fertilisation (356). An insect, thrusting
| its proboscis beneath the upper lip to reach the honey contained in
| thespur, first touches with its back one of the stigmatic lobes; which

project beyond the anthers and have their papillar surfaces directed

parvum.) THE MECHANISMS OF FLOWERS. 465

looked upon as the more primitive, from which the long-tubed type
of V. spicata has been evolved by the agency of bees and sand-

_ wasps. ‘Two different hypotheses suggest themselves for the origin

of the genus Veronica. In the first place, the reduction of the
stamens to two may be due to the development of the delicate

_ pollen-shedding mechanism adapted for Syrphide, which we
_ found to be best developed in V. Chamadrys and V. urticifolia ;

just as in Salvia two stamens have certainly become aborted
owing to the development of the special lever-apparatus in the
others. According to this view, the oldest Veronicas are those
which are adapted for Syrphide, the others, with short tube and
flat limb, being developed from them by degeneration of the
pollen-mechanism; and several species (¢.g., V. Beccabunga and
V. aphylia) do seem to show such a degeneration. But it is con-
ceivable that the ancestors of Veronica suffered reduction in the
number of their stamens simply in consequence of gradual dimi-
nution in size, as in Lycopus among Labiates, several Saginee
among Alsines, small-flowered species of Ranunculus, Chasalea,
and the small-flowered form of Stellaria media, L.; and that the

| pollen-mechanism was subsequently developed in one section of
the genus, In this case we must ascribe to a miscellaneous lot of

Syrphidz and small bees the blue colour of the simpler Veronicas
which are not provided with any special adaptations for Syrphide ;

| for the Muscide and other Diptera, which also visit and fertilise
| these simpler Veronicas, show no signs of favouring the production

of a blue colour in any other instance. I see as yet no grounds

_ for preferring either of these hypotheses to the other.

Orv. LENTIBULARIE £.

Utricularia, L.—Buchenau has investigated thoroughly the

downwards ; immediately afterwards it comes in contact with the

| anthers and gets dusted with fresh pollen. The stigma is irritable,
folding upwards at once on being touched, so that pollen cannot be
applied to the stigma of the same flower as the insect draws back.

1 Botan. Zeitung, 1865, p. 63.

466 THE FERTILISATION OF FLOWERS. [PART III.

Pinguicula alpina, L.—The structure of the flower is similar, but
the stigma, instead of folding up by its own irritability, is pushed
upwards by the retreating insect (Hildebrand, 356). <A fly, forcing
its way into the pale yellow flower, rubs against the stigma with
its back and dusts it with pollen from another flower. It now tries
to move upwards, as far as possible, to free itself from certain stiff
hairs directed obliquely backwards on the inferior wall of the
corolla, and in doing so it dusts its back with fresh pollen (589,
p. 334; 609). Some flies, which are large enough to get caught
firmly but not strong enough to make their escape, are held fast
and perish.

Pingwicula lusitanica, L., is self-fertilismg (Henslow).

Pinguicula vulgaris, L.—Axell gives a figure and description
of the flower, which agree with Hildebrand’s account (17). This
species is adapted for bees (609). 3

Orv. GESNERACE Z£.
The flowers are markedly proterandrous (172, 178, 632).

Orv. BIGNONIACE ZL.

Bignonia, L.—The flowers are proterandrous. The lobes of
the stigma are touched first by an insect-visitor, and therefore get
dusted with pollen from a previously-visited flower; they then
close up immediately, before pollen from their own flower can
reach them (178).

Martynia, L. (Pedalinez), has a similar arrangement (172, 352).

My brother Fritz Miiller fertilised a species of Bignonia (Cipo
alho of the Brazilians) in South Brazil as follows :—

(1) Twenty-nine flowers on two stocks with pollen of their own
stock ; all fell off in a short time.

(2) Thirty flowers on the same two stocks with pollen from
others growing near by; only two flowers developed fully, but
most remained longer upon the stem than in the previous case,
and many showed a commencing enlargement of the ovary.

(3) Five flowers on one stock with pollen from another growing
at a distance ; all five were fruitful (551).

Tecoma capensis, Lind., is visited and fertilised in Natal by
honey-suckers and by small bees (233). -. .

li PART III. | THE MECHANISMS OF FLOWERS. 467

Orv. ACANTHACE LZ.

Thunbergia alata, Boj.—The insect entering the tube of the

_ flower to reach the honey at the base first touches the stigma with

its back, and then the anthers, which are provided inferiorly with
pointed processes (352).

. Cryphiacanthus barbadensis, Nees. (Ruellia clandestina, L.).—

The cleistogamic flowers were known to Dillenius (531).

EHranthemum, L., Dedalacanthus, Anders., Dipteracanthus,

_ Nees." Aichmanthera, Nees., and Ruellia, L., also possess cleis-
| togamic flowers (167).
; Meyenia erecta, Benth—The mechanism of the flower of this
_ West African shrub has been described by Mr. Irwin Lynch (444).
The flowers stand nearly horizontal. The style lies in a groove
on the dorsal side of the tubular curved corolla. The stigma,
_ which stands at the mouth of the tube, is two-lipped ; its upper lip,
which is alone receptive, is rolled into a tube.

The anthers stand midway in the corolla tube, and are furnished

with hairs which catch the pollen as it is being shed. The broad
lower lip of the stigma projects downwards, obstructing the en-
trance ; it first acts as a lever to bring the upper lip down upon
_ the back of an insect entering the flower; but afterwards, as the
Insect emerges with its back dusted with fresh pollen, the lower
lip of the stigma protects the upper one from contact.
Strobilanthes ( Goldfussia) anisophylla, Nees.—This flower was
| carefully described and beautifully figured by Charles Morren in
| 1839 (541A). Morren saw that insects were needed to effect fertilis-
' ation, but he thought only of self-fertilisation, and accordingly he
' misinterpreted the mechanism of the flower.
The flowers stand nearly horizontal. The tip of the style only
bears stigmatic papillz on its lower (anterior) surface ; it is curved
1 upwards so that an insect in entering the flower comes at once in
: “contact with the stigma. When thestigmais touched (or even if it
be breathed upon) it at once becomes straightened out and gener-
i ‘ally curves at the same time to the right, and it becomes closely
' appressed to the inferior wall of the corolla. The insect passes
| further into the flower, and becomes dusted with fresh pollen : this
is carried out of the flower without coming in contact with the
| stigma. According to Morren the irritability of the style is never
_ manifested until after dehiscence of the anthers.

1 Bentham and Hooker place this genus under Ruellia.
HH 2

468 THE FERTILISATION OF FLOWERS. [PART III,

Morren supposed that the pollen fell of itself from the anthers,
and either came directly, or was carried by small insects, to the
hairs upon the inferior wall of the corolla in the neighbourhood of
the stigma; and that thus, when by any cause the style was
irritated, the stigma curved over and applied itself to the pollen.

Acanthus mollis, L., and A. spinosus, L.—The four unilocular
anthers lie close together and hold between them the loose pollen.
The inferior filaments pass below and in front of the anthers, and
are suddenly bent back towards them immediately below their
attachment. The bee-visitors (Bombus italicus and B. terrestris)
have to pass between these inferior filaments, and in doing so force
both them and their anthers apart, and cause the pollen to fall out.
The proterandrous condition lasts for several days, and then the
end of the style, which was straight before, bends downwards and
forwards, so that the lobes of the stigma come in contact with the
bee (172, 178, 360).

Aphelandra pectinata, Willd. (A. cristata, H. B. and Kth).—The
two lobes of the corolla which form the upper lip are rolled round, —
the anthers; the two lateral lobes are approximated, forming
folding doors which close the entrance of the tube. When these ©
doors are opened they cause the lobes of the upper lip also to ©
separate, and the anthers are set free and shed their pollen on the ©
visitor. The fertilising-agents are probably humming-birds (178). |

Rhinacanthus communis, Nees., is markedly proterandrous. In
the first stage, the two anthers are bent down into the entrance of
the flower, and the still immature stigma is bent upwards; in the
second stage the anthers are bent apart to the sides, and the ripe
stigma is placed exactly in the path of the insect’s proboscis, The
visitors are probably Lepidoptera (177).

Orv. SELAGINEA (GLOBULARIACE).

Globularia vulgaris, L., is proterandrous; G. cordifolia, L., and
G¢. nudicaulis, L., are proterogynous with persistent stigmas. The
flowers of all three are light-blue and adapted for fertilisation by
butterflies. This is the only instance in the German and Swiss
flora of a blue colour being produced by the selective agency of
Lepidoptera (609).

parti] = THE MECHANISMS OF FLOWERS. 469

Orv. VERBENACEZ.

; Aigiphila elata, Sw., and 4%. mollis, H. B. and Kth., are con-
_ spicuously heterostyled. 42. obdwrata “ probably was once hetero-
_ styled, and has since been rendered dicecious by the pistil in the
one form and the stamens in the other having become functionless
and reduced in size” (Darwin, 167, p. 124).

Verbena officinalis, L.,is adapted for fertilisation by bees (590,
111., and 609).

The flowers of a Lantana in South Brazil are, according to Fritz
Miiller, yellow on the first day, orange on the second, and purple
- on the third. Some butterflies visit the yellow and orange flowers,
- some exclusively the yellow, none the purple. So this change of
colour increases the conspicuousness of the plant, and at the same
time saves many useless visits (560).

Ocimum, L.—In this genus the Labiate type of flower is reversed,
| the stamens and style lying upon the under lip, while the upper
_ side of the tube lodges the honey, which is protected by hairs on
_ the superior stamens. Therefore the stamens first curve upwards,
the style downwards, and afterwards in the contrary direction;
which is the reverse of what occurs in Teucrium, forinstance. The
fertilisers are bees of the genera Anthidium, Apis, Bombus, and
| Halictus (178, 360).

Orv. LABIAT A.

Plectranthus fruticosus, LiHér.—The reproductive organs lie

below the entrance into the honey-receptacle, which is a spur-like

_ development of the base of the corolla. In the first stage the
style lies with unripe stigmas between the stamens; in the

second the stamens have spread apart, and the style with

outspread stigmas stands alone in the way of insect-visitors (360).

: 336. LAVANDULA VERA (L.), D. C.—The spikes of small blue
_ flowers attract many insects, especially bees, by their strong scent,
and supply abundant honey. The tube is 6 mm. long, and the
nectary resembles that of Thymus in size and position. The
stamens, which lie in the inferior side of the tube, overtop
the stigmas, but the well-marked proterandry insures cross-
fertilisation.

(1) Anthophora quadrimaculata, Pz. 9 ¢, ab.; (2) Osmia nea, L. g,
freq. ; (3) O. rufa, L. 9, s.; (4) Megachile pyrina, Lep. (fasciata, Sm.), ¢,

470 THE FERTILISATION OF FLOWERS. [PART TIT.)

freq. ; (5) M. Willughbiella, K. ¢; (6) M. centuncularis, L. ¢ ; (7) Anthidium
manicatum, L. 9 ¢, ab. ; (8) Crocisa scutellaris, Pz. 9 ¢, ab. ; (9) Ceelioxys
conoidea, Il. 2, freq. ; (10) C. umbrina, Sm. 2; (11) Cheloatomes nigricorne,
Nyl. ¢, all only sucking. See also No. 590, 11.

337. MENTHA ARVENSIS, L.—The base of the ovary, which
secretes the honey, is several times as large as the ovary itself,
(n, 4, Fig. 159). The corolla forms a bell, which in the pistillate
flowers is about 2 mm., in the hermaphrodite about 3 mm. long,
and in both is fully half as wide! at the mouth as it is long. The
honey is accessible to very short-lipped insects, and it is completely
sheltered from rain by hairs which extend from the sides of the
bell to its centre. The flowers make themselves perceptible at a,

Fra. 159.
1—4.— Mentha arvensis.

‘A —Female flower.

2.—Hermaphrodite flower, in first Ganado stage.
83.—Ditto, in second (female) stage.

4.—Ovary and nectary.

5.—M. aquatica, Female flower, seen obliquely from the front, to show the rudimentary stamens.”
Figs. 1 and 5 should be horizontal,

distance by their scent, and their close whorled arrangement renders
them conspicuous to the eye, still more in the case of the large-
flowered hermaphrodite than the smaller female plants. I have
verified by direct observation in the case of Mentha the opinion
to which I shall recur in describing Nepeta and Thymus, that
insects visit the more conspicuous flowers before those that are
less so; in the case of Nepeta and Thymus I have neglected to
study this point sufficiently,

Visitors: A. Diptera—(a) Stratiomyide: (1) Odontomyia viridula, F. ;
@ A pte (2) Eristalis — L., very ab. ; (3) Syritta pipiens, L.,
; (4) Melithreptus scriptus, L. ; (5) M. teeniatus, Mgn., both not rare, s. ;
ie Huselda: (6) Onesia floralis,. R. D.; (7) O. pepaloralia, Mgn., both ab. ;
(8) Luciliasilvarum, Mgn. ; (9) L. cornicina, F. ; (10) Pyrellia cadaverina, L. ;

PART III. | THE MECHANISMS OF FLOWERS. 471

(11). L. albiceps, Mgn., the last four species not rare. B. Lepidoptera—Rho-
palocera: (12) Satyrus Janira, L. All these insects sucked honey only,
though I expected to see the Syrphide at least eating pollen.

338. MENTHA AQUATICA, L. (IZ. hirsuta, Sm.).—W hile in Mentha
arvensis small-flowered female and large-flowered hermaphrodite
flowers occur in nearly equal numbers, in JZ. aquatica the former
are much rarer than the latter. In the hermaphrodite flowers the
tube is 4 to 5 mm. long, and about 2 mm. wide at the mouth;
otherwise the flower resembles that of JZ. arvensis. Although,
owing to the greater length of the tube, the honey is slightly less
accessible than in JZ. arvensis, insect-visits are more numerous,
owing to the taller stalks and the larger, denser heads of flowers.

Visitors : A. Hymenoptera—(a) Apide : (1) Halictus cylindricus, F. ¢ ; (2)
H. maculatus, Sm. ¢, both ab. ; (3) H. longulus,Sm. ¢; (4) H. nitidiusculus,
K. g, all s. ; (b) Ichnewmonide : (5) Various sp., some creeping bodily into
the flowers. B. Diptera—(a) Empide: (6) Empis rustica, Fallen; (7) E
livida, L., both ab., s. ; (8) E. tesselata, F., do. ; (b) Syrphide: (9) Ascia
podagrica, F., s. ; (10) Eristalis nemorum, L. ; (11) E. arbustorum, L. ; (12)
E. eneus, Scop. ; (13) E. sepuleralis, L., all four very ab., sometimes s., some-
times f.p. ; (14) Syritta pipiens, L., ab. ; (15) Helophilus pendulus, L., ab. ;
(16) H. trivittatus, F.; (17) Syrphus pyrastri, L., ab. ; (18) Melanostoma
mellina, L., ab., these also both s. and f.p. ; (¢) Muscide : (19) Onesia floralis,
R. D. ; (20) O. sepulcralis; Mgn. ; (21) Sarcophaga carnaria, L. ; (22) Musca
corvina, F’,, all four very ab. ; (d) Tabanide : (23) Chrysops cecutiens, L., s.

Delpino considers Mentha and Coleus, Lour., degraded forms of
the Labiate type (No. 178, p. 143; 360, p. 656); he, however,
gives no reason for thinking them to be such, and not rather less
specialised forms, differing less from the common ancestors of
the Labiates.

The flower of Coleus oe Benth. ?) is figured and described
in No. 560, It.

339. Lycopus EUROP&US, L.—The corolla forms a bell 3 to 4
mm. long, 24 mm. wide at the mouth, but scarcely 1 mm. wide at
the base. Honey is secreted by the yellow fleshy base of the
ovary ; it is accessible to very short-lipped insects, and is sheltered
from rain by long hairs which project from the sides of the bell
towards its centre. Some purple spots on the under lip serve
as guides,

The flowers are markedly proterandrous. When the two
anthers which project from the tube come to maturity, the two
stigmas still lie folded together (Fig. 160, 1). When the stigmas

472 THE FERTILISATION OF FLOWERS. [PART 111.

separate, the anthers are already withered and bent downwards.
The wide space between the anthers and stigmas seems sufficient
to prevent self-fertilisation even without the help of proterandry.

In spite of the small, inconspicuous flowers, insect~-visitors are
numerous and varied.

While in Salvia the abortion of two stamens may be explained
by the development of the lever-mechanism which they would
have interfered with, in Lycopus their disappearance is due simply
to the small size of the flower; and though only two are present,
the small size of the flower causes every insect to come in contact
with them. The same explanation holds good for Veronica, whose

Fic. 160.—Lycopus europeeus, L.

1.—F lower, in first (male) stage, from below.
_ 2,—Ditto, in second (female) stage, from the side. This figure should be horizontal.

3.—Ditto, in first stage, after removal of the under lip, from below.

a, abortive stamens; n, nectary; a’, perfect anthers, before dehiscence; a, ditto, dehiscing ;
a3, ditto, withered ; st’, stigma, still immature; st, ditto, ripe.

flowers are the smallest among Scrophularinez as those of Lycopus
are among Labiates.

Visitors : A. Hymenoptera—Vespide : (1) Polistes gallica, L., and var.
diadema, s., freq. (Thur.). B. Diptera—(a) Syrphide: (2) Melithreptus
scriptus, L., s. and f.p. ; (3) Syritta pipiens, L., very ab., s. and f.p. ; (6) Mu-
scide : (4) Lucilia silvarum, Mgn. ; (5) L. cornicina, F., both s., freq. ; (6)
Sarcophaga albiceps, Mgn., ab., s. ; (7) Pollenia Vespillo, F.,s, Also many small
gnats 14 mm. long. C. Hemiptera—(8) Some undetermined species of bugs.
D. Lepidoptera—(9) Adela sp.,s. E, Thysanoptera—(10) Thrips, very ab,

340. THymus SERPYLLUM (L.), Fr—Our two species of Thymus
have, like Nepeta, stocks of two kinds, one with large herma-
phrodite, the other with small pistillate flowers.

Hildebrand (351) has sought to ascribe the origin of the small-
flowered female plants to the proterandrous condition of the

PART III. | THE MECHANISMS OF FLOWERS. 473

hermaphrodite ones; his theory rests, if I understand it rightly,
upon the two following arguments. Since no stigmas are mature
at the time when in the first flowers of a proterandrous plant the
stamens dehisce, these stamens are of no use to the plant, and since
all economy of useless organs is advantageous to the plant, the
stamens of the first flowers of proterandrous plants can be abolished
by Natural Selection. This reasoning is undeniably correct, but it
applies only to the first flowers of proterandrous plants, and not to

Fig. 161,

1—3.—Thymus Serpyllum, Fr.

1.—Hermaphrodite flower, in first{(male) stage.
| 2.—Ditto, in second (female) stage.
3.—Female flower.

4—6.—T. vulgaris, L.
4.—Female flower. ;
5.—Pistil of hermaphrodite flower in first stage.
6.—Ditto, in second stage. ov, ovary; n, nectary. (xX 7.)

the female stocks of Thymus which bloom all summer beside the
hermaphrodite ones. This in my opinion is only to be explained in
the way that I have suggested in the case of Nepeta (p. 484). The
variability in size, which my theory presupposes, is present in our
two species of Thymus, as in Nepeta, to such a degree that, while
the largest hermaphrodite flowers (Fig. 161, 1, 2) are several times as
large as the smallest female (Fig. 161, 3), the smallest hermaphrodite
and the largest female flowers are nearly equal in size. The flowers

474 THE FERTILISATION OF FLOWERS. [PART III.

on the same stock, on the contrary, are all much of the same size,
as my explanation requires, but the hermaphrodite flowers enlarge
in passing from the first (male) to the second (female) stage. The
certainty of cross-fertilisation, which is also necessary for my theory,
is in a high degree a character of Thymus; for the honey is ex-
ceedingly abundant and has an aromatic taste, the base of the
ovary by which the honey is secreted (n, 5,6) is many times as
large as the ovary itself, the aggregation of the flowers and their
strong scent reveal them to insects and permit insects to visit
many with. little loss of time, and from the reproductive organs
protruding beyond the corolla many flowers may be fertilised at
once as the insect clambers over the inflorescence. The tube is
smooth at the base where the honey lies, and lined with hairs above
to exclude rain; it is only a few millimetres long (25 to 4 mm. in
T. Serpyllum), so that the honey is accessible to a great variety of
insects. Self-fertilisation was impossible in all the flowers that I
have examined, for the style, which in the first stage is short and
overtopped by the anthers (Fig. 161, 1, 5), elongates and grows
out beyond the anthers before its two divisions with the stigmatic
papille at their tips spread apart."

Darwin found the female form very much more productive than
the hermaphrodite, both in 7. Serpyllum and T. culgaris.

While Darwin in England, Hildebrand in the Rhine Provinces,
Ascherson, according to his /ora, in Brandenburg, and I in
Westphalia and Thuringia, have only observed the two forms, female
and hermaphrodite, of this plant, Delpino, near Florence, has
found the plant trimorphic: he states that it consists there of
hermaphrodites with both stamens and pistil equally developed ;
of others with greatly developed stamens and the pistil in every
stage of abortion, or even absent; and finally, others with greatly
developed pistil and more or less aborted stamens (No. 173, p. 7).
In England also there seems to be a passage towards purely male
flowers, for, according to Dr. Ogle (No. 632, p. 54), in many of the
liermaphrodite flowers the stigma never reaches maturity. With-
out accurate information concerning the size of the flowers, the
time of their development, the frequency of insect-visits, and the
relative distribution of the two forms, all attempts at explanation
must be unsatisfactory.

Visitors: A. Hymenoptera—(a) Apidw: (1) Apis mellifica, L. §,s. and
c.p.,ab. ; (2) Bombus pratorum, L. 2, do. ; (3) Saropoda bimaculata, Pz. 2 ¢>

' Compare my account of Nepeta Glechoma, yp. 484, and Darwin’s account of
Thymus, No, 167, p. 800.

PART IIT. | THE MECHANISMS OF FLOWERS. 475

ab.; (4) Andrena nigrozwnea, K. ?, s.; (5) Megachile cireumcincta, K. ¢, s. ;
(6) Nomada germanica, Pz. 2, s.; (7) Celioxys sp. g, s.; (b) Sphegida :
(8) Ammophila sabulosa, L. 9 ¢, s., ab. ; (9) Cerceris variabilis, Schr. 2 g, -
s. ; (10) Lindenius albilabris, F., s. B. Diptera—(a) Bombylide : (11) Sys-
teechus sulfureus, Mik., s.; (b) Syrphidw: (12) Eristalis arbustorum, L., very
ab., s. ; (13) E. sepulcralis, L., s. ; (14) Syritta pipiens, L., s., ab. ; (15) Volu-
cella bombylans, L., s. ; (¢) Conopide : (16) Conops flavipes, L., s. ; (17) Sicus
ferrugineus, L., s.; (18) Myopa testacea, L., s.; (d) Muscide: (19) Lucilia
cornicina, F. ; (20) Echinomyia tesselata, F. ; (21) Gymnosoma rotundata, L. ;
(22) Ocyptera brassicaria, F., ab. ; (23) Sarcophaga carnaria, L., very ab. ; (24)
S. albiceps, Mgn., very ab., all only sucking. C. Lepidoptera—(a) Rhopalo-
cera: (25) Satyrus pamphilus, L. ; (26) 8. Janira, L. ; (27) Argynnis Aglaia,
L. ; (28) Lyceena icarus, Rott. ; (b) Sphinges: (29) Sesia empiformis, Esp
(Almethal) ; (30)_S. tipuliformis, L.,—all sucking. See also No. 590, 111., and
No. 609.

I have observed altogether on 7’ ishli —

|
Apidx. aeons Diptera. fot ches Total.
= foal

In the Alps...

|
In the Lowlands: 7 17 20 on 30
ie

25 65 30 | 2 | 122

In every 100 insect-visitors there are, therefore :—

Apide. Lepidoptera.| Diptera, {Other Insects.) Total.

In the Lowlands

23°6 27°7 41°6 6°9 99°9

|
:

In the Alps... .. | 20°5 53°2 24°6 1°6 99°9

341. THYMUS VULGARIS, L.—I have observed the following
visitors in my garden :—

A. Hymenoptera—(a) Apide: (1) Apis mellifica, L. $,s. ; (2) Halictus,
small species, s. and ¢.p. ; (b) Sphegide: (3) Ammophila sabulosa, L. 9 ¢, s.
B. Diptera—(a) Empide: (4) Empis livida, L.,s:; (b) Syrphide : (5) Syritta
pipiens, L., s. and f.p., ab.; (c) Muscide : (6) Sarcophaga albiceps, Mgn., s.,
ab. C. Lapidoplora-—Rohinges ; (7) Sesia tipuliformis, L., s.

342, ORIGANUM VULGARE, L.—This plant agrees with Thymus
in consisting of large-flowered proterandrous hermaphrodite, and
small-flowered female individuals, and in the whole mechanism of
the flowers; and if it is inferior to Thymus in perfume and in the

476 THE FERTILISATION OF FLOWERS. [PART III,

taste of its honey, it has a compensating advantage in its large
flowers crowded more closely together on higher stalks. The
plant has lost the power of self-fertilisation. Though the flower
is larger than that of Thymus, the tube is short enough (in the
hermaphrodite flowers 4 to 5 mm., in the pistillate 3 to 4 mm.,
long) to permit a great variety of insects to reach the honey. My
shorter list of visitors is due to my having had much less opportunity
of watching the plant.

Visitors: A. Hymenoptera—Apide: (1) Bombus terrestris, L. 2; (2)
Apis mellifica, L. §, freq. ; (3) Halictus cylindricus, F. ¢; (4) H. albipes,
F. $, both species very ab. ; (5) H. nitidus, Schenck, ¢, all sucking. B.
Diptera—(a) Empide : (6) Empis livida, L. ; (7) -E. rustica, Fallen, both very
ab., s.; (b) Syrphide : (8) Ascia podagrica, F., f-p., ab. ; (9) Eristalis arbu-
storum, L., s. and f.p., ab. ; (10) E. nemorum, L., do. ; (11) Helophilus pen-
dulus, L.,s. ; (c) Conopide : (12) Sicus ferrugineus, L. ; (13) Myopa polystigma,
Rondani; (14) M. variegata, Mgn., all three sucking; (d) Muscide: (15)
Ocyptera brassicaria, F. ; (16) O. cylindrica, F., both very ab. ; (17) Prosena
siberita, F., ab., all three s. C. Lepidoptera—Rhopalocera : (18) Satyrus
Janira, L., s.; (19) S. hyperanthus, L., s. See also No. 590, UL, and
No. 609.

Satureia hortensis, L., is gynodicecious, and the female flowers
are much more productive than the hermaphrodite (Darwin, No.
167 ; for list of visitors see No. 590, III).

343. CALAMINTHA CLINOPODIUM, Spenner (C. vulgare, L.).—
The nectaries and honey-receptacle are formed on the ordinary
Labiate type. The corolla-tube is 10 to 13 mm. long, and is often
filled for a space of 3 mm. with honey.

The inferior division of the style forms a broad, lanceolate
lamina, which is bent downwards and bears no distinct stigmatic
papillz ; the upper is much narrower and shorter, and of very
varying size. There is still more striking variability in the
‘development of the stamens, some or all of them being partially
or completely aborted in many flowers. This isremarkable because
it shows us how Natural Selection could have operated, and must
have operated if, together with the proterandrous condition, there
came into existence small-flowered plants which were visited as a
rule after the others.

Visitors : Lepidoptera—Rhopalocera : (1) Pieris brassice, L. (15), not rare ;
(2) Satyrus hyperanthus, L.,—both species s. See also No, 609.

Calamintha Nepeta, Sav., is gynodicecious, and visited by bees
and butterflies (609, 734).

}
s

PART ILI. | THE MECHANISMS OF FLOWERS. 477

344, CALAMINTHA AcINos, L. :—

Visitors : A. Hymenoptera—Apide: (1) Apis mellifica, L. $, s. and c.p.,
ab, (Thur.). B. Diptera—Bombylide : (2) Systceechus sulfureus, Mik., s.
(Thur.).

Calamintha alpina, Lam.—Both large-flowered and _ small-
flowered plants occur, the flowers of both being hermaphrodite
and proterandrous, but only the small flowers being capable of
spontaneous self-fertilisation.

The plant is visited by Syrphide and by a great number of
bees and Lepidoptera (584, 609).

Horminum pyrenaicum, L.—The dark-blue colour, the odour,
and the very abundant honey attract numerous insects, while the
marked proterandry renders self-fertilisation impossible (No. 609,
fig. 125).

345. MONARDA DIDYMA, L.—I have’seen this plant visited by
Plusia gamma, L.

Monarda ciliata (?) is adapted for fertilisation by Sphingide
(228),

Rosmarinus, L., according to Delpino, is proterandrous, and the
stigma comes to take the place of the anthers (178).

346. SALVIA PRATENSIS, L.—The remarkable mechanism of
this flower, and the way in which it is fertilised by humble-bees,
was so thoroughly explained and figured by Sprengel! that
Hildebrand, in his work on Salvia (345), has described nothing
new, except the proterandrous condition, which Sprengel had
overlooked,

Honey is secreted by the yellow, fleshy base of the ovary. The
corolla is horizontal; the under lip forms a convenient platform
for insects, and the erect, helmet-shaped upper lip incloses the
anthers. In the first stage, the style, with its stigmatic branches
still folded together, protrudes almost horizontally from the upper
lip, in the second it points downwards with divergent and recuryed
stigmas. The entrance to the tube is guarded by two lamelle
which converge and coalesce with one another anteriorly ; these
lamellz are attached to the inferior limbs of the enormously long
connectives of the two stamens, and are produced by meta-
morphosis of the inferior anther-lobes; the other and much
longer limb of each of the two connectives rises up under cover of

1 702, pl. 1. figs. 18, 24-83, 39, 42.

478 THE FERTILISATION OF FLOWERS. [PART III.

the upper lip, and there bears the other, pollen-producing anther-
lobe. Since the connectives are easily movable about their
fulcrums on the short, outwardly-directed filaments, the two
lamine are rotated backwards and upwards, the anther-lobes
(hitherto concealed within the upper lip and coated on their lower
surfaces with pollen) forwards and downwards, when a bee’s head
enters the tube. The movement of the laminz leaves the path to
the honey free, that of the longer limbs of the connectives brings
the anther-lobes down upon the bee’s back. When the bee with-
draws its head, the connectives with their laminz resume their
former position. In old flowers the bee first touches the papillar

Fic. 162.—Salvia pratensis, L.

1.—Flower, from the right side.

2.—Stamens, seen obliquely (x 2). 1 .

a, filament ; b, upper arm of the connective; c, lower arm of ditto; d, superior anther-lobes ;
é, inferior ditto, transformed into a lamina closing up the tube; f, point of cohesion of the two
inferior aither-lobes; g, style in first stage ; g’, style in second stage. The dotted line b’d’ indicates
the position of the anthers when rotated forwards.

sides of the recurved branches of the now downward-pointing style.
The superior pair of anthers in this and in all the other species
of Salvia is present in the form of small and quite useless
rudiments, easily intelligible as an inheritance from didynamous
ancestors.

Humble-bees were stated to be the fertilising agents by
Sprengel and Hildebrand, but the species were not determined,
The plant does not occur at Lippstadt, and I only possess in my
garden a single plant, of a pink variety, found by my father at
Miihlberg, Erfurt, so I have had little opportunity of observing’ its
insect-visitors. As-normal-visitors which proceed in the manner

PART III. | THE MECHANISMS OF FLOWERS. 479

described above, and effect cross-fertilisation regularly, I have
only noted the following :—

(1) Bombus silvarum, L. 9 and $; (2) Osmia rufa, L. 9 ; (3) Anthidium
manicatum, L. 9 (very freq.) ; (4) Megachile pyrina, Lep. (fasciata, Sm.), ¢,
all sucking normally.

Among useless visitors Sprengel mentions (p. 61) cabbage-white butterflies,
which insert their proboscis in the small space between the lower anther-lobes
and the corolla, and obtain the honey without effecting fertilisation. I have
seen Plusia gamma, L., acting in the same way, I have also seen small bees in
abundance (Prosopis communis, Nyl. ¢ 9, Halictus sexstriatus, Schck. 9, H
nitidus, Schck. 9, H. nitidiusculus, K. 9, H. morio, F. 2) creeping into the
flowers and reaching the honey without causing more than a slight and ineffectual
movement of the levers. The position of the anthers quite prevents flies from
stealing the pollen of this flower, and I have never observed a bee sweeping
the anthers with its tarsal brushes. Delpino (No. 567, pp. 9, 10) unjustly
questions my statement “that in Salvia the anthers are more or less protected
from insects, which are restricted mainly or exclusively to the honey.” A
further list of visitors in Low Germany (twelve Apidae, two Bombylide) is
given in No. 590, mt. On the Alps I have seen the flowers visited by the
hive-bee, by six humble-bees, eleven Lepidoptera, and Rhingia (609).

This species is gynodiecious. In addition to the large-flowered
hermaphrodite plauts, small-flowered female plants occur, in whose
flowers the now functionless lever-apparatus shows all degrees of
abortion.

This species is remarkable above all other cases of gynodicecism,
because it shows us the gradual abortion of all the stamens of a
flower in four distinct stages: (1) The first of the five stamens,
which must have been placed in the median line of the corolla
superiorly, and is still present, more or less altered, in many Scro-
pbularinez (Scrophularia, Pentstemon), had already disappeared in
the common ancestors of the Labiates. (2) The two upper stamens
of the remaining four were reduced to tiny stalked knobs in the
ancestors of the genus Salvia. (3) The inferior anther-lobes of
the two remaining stamens produce pollen to a greater or less
extent in S. officinalis, S. porphyrantha, and S. triangularis, but in
S. pratensis they are transformed into two hollow laminze which
coalesce anteriorly. (4) In the small-flowered female form of 8.
pratensis, the superior anther-lobes also have become useless, and
subject to degeneration in common with the whole of the lever-
apparatus (570, vol. xvi.; 609).

Salvia Sclarea, L., ‘s athiopica, S. argentea, L., S. ieee
Ait., 8. pendula, Vahl., and. S. rubra, Spr., have the same.mechan-
ism according to ‘Hildebaad as, S._ pratensis... In. 8. -natans, Le
(Hild. figs. 4-7), on the other hand, the rotation of the connectives

480 THE FERTILISATION OF FLOWERS. [PART III.

is much less, and therefore the anther-lobes emerge much less from
the upper lip; but the flowers form pendulous racemes and are
therefore inverted, and accordingly the insects settle on the upper
lip and are dusted with pollen ventrally by the slightly protruding
anthers. In S. splendens (345, figs. 8 and 9) the inferior anther-
lobes form simple lamellae (not bent inwards anteriorly), which
coalesce with one another for almost their entire length. All
these species agree in other respects in their floral mechanisms,
and are all alike proterandrous.

On the other hand, S. Grahami, Benth. (345, figs. 10-12), has
homogamous flowers with a short style scarcely overtopping the an-
thers ; in S. lanceolata (345, figs. 13-14), which is also homogamous,
the inferior stigmatic lobe lies between the anthers, and exposed to
self-fertilisation. In S. hirsuta (345, figs. 15-17), the inferior stigma
is very broad, and recurved backwards so as to press against both
anthers and regularly to effect self-fertilisation, which, according
to Hildebrand’s experiments, is fully productive.

347, SALVIA OFFICINALIS, L.—Sprengel described and figured
the mechanism of this species also, noting its proterandrous con-
dition, and he saw it visited by bees; but Hildebrand’s description
(345) is much more thorough. The chief points in which this

Fic. 163.—Salvia officinalis, L.

Flower, after removal of the right half of the calyx and corolla.
a—g, as in Fig. 162; h, nectary ; i, ovary ; k, abortive anther ; 1, hairs to guard the honey.

species differs from S. pratensis are as follows: the two arms of
each connective are much shorter, and the lower one is not
metamorphosed into a lamella, blocking the entrance of the flower,
but is formed like the upper, though smaller; it usually bears an
anther-lobe filled with pollen, but always much smaller, and con-
taining only a quarter, or at most half as much as the upper
lobe: sometimes it is altogether abortive. In correspondence
with the shortness of the upper arm of the connective, the upper
lip is also short, but broad enough to protect the wide entrance of
the flower from rain. Both anther-lobes of both stamens stand in
the mouth of the flower, the superior slightly above and in front

parti.) THE MECHANISMS OF FLOWERS. 481

of the inferior, and the two connectives le so close together that
- one moves with the other. A bee in entering first thrusts its head

against the two inferior anther-lobes, and thus causing the connec-
tives to rotate, it is immediately afterwards struck on the back
by the two superior anther-lobes. The pollen thus placed on the
bee’s head and back is rubbed off in older flowers upon the two
stigmas, which are divergent and much bent downwards,

Dr. Ogle gives a very detailed description of this species of
Salvia (631), and rightly lays stress upon the following additional
points as special adaptations: (1) the convexity of the upper lip,
which causes the growing style to take such a direction that after-
wards its outspread stigmas must come in contact with the bee’s
back; (2) the bulging of the upper wall of the anterior part of the
tube, which gives the inferior anther-lobes free play when the
connectives rotate ; (3) the shortness and stiffness of the filaments,
which give a steady fulcrum for the connectives ; (4) the divergence
of the filaments, which leaves a free entrance for the bee.

Besides the hive-bee, which Sprengel and Hildebrand also saw,
I have observed Bombus silvarum, L. 9, Anthophora cestivalis,
Pz. 2, Anthidium manicatum, L. 2, Osinia rufa, L. 9, as regular
fertilisers ; all were sucking honey exclusively. Of useless guests,
Hildebrand observed a butterfly, which could easily reach the
honey with its proboscis without dusting itself with pollen. I
have seen a small species of bee with abdominal collecting-
brushes, Chelostoma campanularum, 2 3, repeatedly creeping in and
out of the flowers without being dusted with pollen; and Herr
Borgstette sent me, from Teklenburg, Prosopis communis, Nyl. 9,
which he had caught on the flowers. A further list of visiters is
given in No. 590, III.

According to Delpino, the anthers ob S. officinalis, like those
of Sideritis, are provided with sticky glands (178).

Salvia porphyrantha resembles S. officinalis in the arrangement
of its connectives, and in the inferior anther-lobes being filled
with pollen, though with a smaller quantity than that presenke in
the superior lobes.! |

Salvia glutinosa, L., according to Dr, Ogle (631), differs from
S. officinalis in that the inferior anther-lobes are quite barren and
are withdrawn within the tube, and that the inferior, not the

| superior, side of the anterior part of the tube bulges out. It is

_ fertilised by large humble-bees; small humble-bees, and hive-
_ bees whose proboscis is too short to reach the honey legitimately,
1 According to Mr. T. H. Corry.

EI

482 THE FERTILISATION OF FLOWERS. [PART III.

bite a hole in the superior side of the tube immediately over the
nectary and steal the honey. Dr. Ogle found 90 per cent. of the
flowers bitten through, and I have always found the flowers bitten
through and robbed of their honey by an Alpine robber-bee, Bombus
mastrucatus, Gerst. % (609).

Salvia nilotica, Vahl. (345, figs. 24, 25)—The main point in
which the flowers differ from those of S. officinalis is that the two
inferior anther-lobes lie freely side by side, and the connectives
can be caused to revolve separately. Hildebrand saw them visited
by bees.

S. verticillata, L. (345, figs. 26-30; 172), has immovable con-
nectives, but an upper lip which folds back when touched by an
insect-visitor, and exposes the two superior anther-lobes to contact
with it. The style, which would hinder this movement if in its
usual place, is lower down. Hildebrand saw this species also
_visited by bees. According to Delpino, the anthers, like those of
Sideritis and of S. officinalis, are provided with sticky glands (178,
p. 145). S. verticiilata is visited by numerous species of bees and
humble-bees (590, III. ; 609).

In S. patens, Cov. (172, 345, fig. 31), the anthers project partly ©

or entirely beyond the upper lip. The connectives are versatile,
and the lower anther-lobes are metamorphosed into lamellw; the
style is so fixed between the upper arms of the connectives that
when the connectives revolve it is carried forwards and downwards
with them, and its stigma, which projects beyond the anthers, is
thus brought first in contact with the insect’s back. Ogle’s account
(631) agrees with Hildebrand’s. But while Hildebrand considers
self-fertilisation and cross-fertilisation as alike possible, Ogle shows
that cross-fertilisation is insured. When an insect-visitor strikes
the lower arm of the connective, its back is touched by the anthers
and a little farther back by the stigma, and the space between the
two points is increased by the lower stigma being very short in
comparison with the upper. As the insect passes further in,
anthers and stigma rub along its back, but no pollen from the
anthers reaches the stigma of the same flower. As the insect
draws back anthers and stigma return to their places below the
upper lip; in the next flower the stigma comes in contact with
a part of its back already dusted with pollen. In several flowers
Dr. Ogle found the style shorter than the anthers; in such
flowers insects might lead to self-fertilisation as well as cross-

fertilisation. Ogle states the very surprising fact that the honey —

in S. patens is not secreted by the base of the ovary as is usually

——

PART III. | THE MECHANISMS OF FLOWERS. 483

aN Pee

the case in Labiates, but by a thick tuft of glandular hairs on
the corolla, immediately above a constriction which completely
_ shuts off the lower part of the tube that usually serves as a honey-
_ receptacle.

In S. austriaca, Jacq. (345, figs. 32-35), the anther-lobes
stand far apart and project beyond the upper lip. If the lower
arms of the two connectives are thrust inwards the upper arms
- converge, and the anther-lobes (moving downwards and forwards)
strike against each other in front of the mouth of the flower.

S. triangularis, Thunb. (345, figs. 36-39), has immovable
connectives, almost straight, and lying parallel to the long axis of
the flower; they have a fully-formed anther-lobe at eachend. The
two anterior anther-lobes project from the mouth of the flower, and
are the first to touch the insect’s back ; the two posterior, which
stand in the entrance, touch its sides immediately afterwards.
In the second stage the stigma stands in front of the anterior
_ anther-lobes, and is touched first of all by the insect.
| S. tubiflora, Sm. (345, figs. 40, 41).—The mechanism of this
_ flower resembles that of the last-named species in all important
_ points, except that the inferior arm of each connective bears, in-
stead of an anther-lobe, an elongated lamina which lies in contact
with the upper lip.

re

348, SALVIA SILVESTRIS, L., agrees on the whole in its floral
mechanism and in its proterandrous condition with S. pratensis, but
its flowers are so much smaller that a proboscis only 4 mm. long
suffices to reach the honey. I observed as its natural fertilisers in
Thuringia: (1) Apis mellifica, L. 8 (6), sucking honey, and dust-
ing the top of its head with pollen and afterwards applying it to
the stigma in older flowers; (2) a wasp, Psammophila afjinis,
K. ¢ (4), in abundance, sucking honey; and as useless visitors,
(3) Pieris rape, and (4) P. napi.

Salvia cleistogama, de Bary and Paul, when transplanted to
Halle from Africa, bore only cleistogamic flowers for five years
(Ascherson, 10). Ascherson considered that the plant afforded an
example of continuous self-fertilisation ; but he himself afterwards
observed ordinary open flowers (11).

Scarlet species of Salvia in South Brazil are visited very abund-
antly by humming-birds (Fritz Miiller, No. 359); so likewise are
‘species of Salvia in the Cordilleras (Darwin, No. 164, p. 371).

Salvia splendens, Sellow (distinct from the plant described

under this name by Hildebrand).—According to Mr. W. Trelease
II 2

4.84 THE FERTILISATION OF FLOWERS. [PART IIT.

this plant is very abundantly visited by humming-birds, and is
adapted for them in the following characters : the small under lip,
scarcely fit for a standing-place, the very large amount of honey,
and the bright scarlet colour of the calyx and corolla (735).

349. NEPETA GLECHOMA, Benth. (Glechoma hederacea, L.)—
In the small-flowered female form, the tube is 64 to 8 mm. long,
widening in the anterior half to a diameter of only 14 to 23 mm.
laterally, and rather less antero-posteriorly : in the large-flowered
hermaphrodite plants the tube is 9 to 16, usually 14 to 16 mm.
long, and, for the greater part of the anterior half, 25 to 4¢
mm. broad, being slightly less in the antero-posterior diameter.
The honey in the small female flowers is accessible to all our
humble-bees, while the large, hermaphrodite flowers, by widening
anteriorly to admit the bee’s head, render their honey accessible to
all except B. terrestris, L.

The existence of plants bearing only small female flowers in
Nepeta and also in Origanum, Thymus, Mentha, and others, is not
to be explained merely by the necessity of insuring cross-fertilisa-
tion ; for in all these genera cross-fertilisation is completely pro-
vided for by the hermaphrodite forms alone. But the following —
view of the small-flowered female plants is intelligible :— |

Of the flowers of the same species growing together, the most —
conspicuous are first visited by insects, and if the flowers on some ©
plants are smaller than on others, perhaps owing to scanty nourish- —
ment, they will generally be visited last. If the plant is so much |
visited by insects that cross-fertilisation is fully insured by means —
of proterandrous dichogamy, and self-fertilisation is thus rendered
quite needless, then the stamens of the last-visited small-flowered
plants are useless, and Natural Selection will tend to make
them disappear because the loss of useless organs is manifestly
advantageous for every organism.

This explanation rests upon the hypotheses, (1) that the flowers
of those species in which small-flowered female plants occur together
with large-flowered hermaphrodite plants are plentifully visited
by insects and are markedly proterandrous ; (2) that variation
in size of the flowers has always taken place, not among the
flowers on a single plant, but between the flowers on different —
individuals, 7 ‘

Both hypotheses are well founded. For (1) the flowers of
Nepeta, Thymus, Origanum, and Mentha are plentifully visited —
by insects and are markedly proterandrous, while proterandry has_

PART III. | THE MECHANISMS OF FLOWERS. 485

been quite wrongly ascribed to many other Labiates. The styles
in these four genera are still applied closely together after the
anthers have dehisced, and though when the styles separate the
_ anthers may be still coated with pollen, self-fertilisation is pre-
vented by the style projecting far beyond the anthers. In species
where cross-fertilisation is less perfectly insured, and which pro-
duce seed frequently by self-fertilisation, the smaller hermaphrodite
_ flowers can never become transformed into purely female flowers,
| since their anthers are always of real service, and cannot be
_ removed by natural selection. And (2) it cannot be doubted that,
in Nepeta, Thymus, Origanum, and Mentha, the size of the flowers
has been subject to great variations, since the same condition
occurs even now, at least in Nepeta and Thymus. While flowers
of the same age on a single plant differ little in size, we find on
_ different plants all intermediate grades in size, between the smallest
_ female and the largest hermaphrodite flowers ; and the largest female
flowers are quite as large as the smallest hermaphrodite.

Darwin’ adduces several weighty objections to this view, and
my own observations on Centaurea Jacea also militate against it.
Darwin prefers to ascribe the gynodicecious condition to increased
fertility. He supposes that either some individuals tended to pro-
duce more seed, and consequently less and less pollen, until finally
_ their stamens disappeared; or else that the stamens of certain
| individuals began to show a tendency to abort, and that these
individuals consequently produced more seed.

‘ Visitors: A. Hymenoptera—Apide : (1) Bombus agrorim, F. § 2 (10—
_ 15); (2) B. confusus, Schenck, 2 (12—14) ; (8) B. lapidarius, L. § Oe :
(4) B. hortorum, L. § 2 (18—21); (5) B. pratorum, L. 2 (11—12) ; (6) B

_ Rajellus, Ill. 9 (12—13) ; (7) B. silvarum, L. 9 (12—14) ; (8) B. (Apaths)
i ~ Barbutellus, K. 9 (12); (9) B. (A,) vestalis, Foure. 9 (12); (10) B. (A.)
il rupestris, F. 9 (11—14) ; most of these species very ab., sucking both (nine
_ and hermaphrodite flowers in the normal way ; (11) B. terrestris, L. 9 (7—9),
_ always bores through the corolla of the hermaphrodite flowers, and sometimes
of the small female flowers, though its proboscis is long enough to suck the
latter normally ;—sometimes it must at least attempt to suck the hermaphrodite
flowers normally, for once (May 7, 1871) I saw a specimen sucking female
flowers with pollen of Nepeta on its head ; (12) Apis mellifica, L. $, sucking
the female flowers normally ; once (May 3, 1871) I saw it insert its head into
' several hermaphrodite flowers, but afterwards take to piercing the corolla with
| its maxille ; (13) Anthophora pilipes, F. 9 ¢ (19—21), very ab. ; (14) Osmia
| wnea, L. 2 (9—10) scarce ; (15) O. rufa, L. 2 $ (7—9), sucking both kinds
of flowers normally ; (16) O. fusca, Christ. 2 (8) ; (17) Nomada varia, Pz. ¢

1 Forms of Flowers, p. 304, ete.

486 THE FERTILISATION OF FLOWERS. [PART III.

(54—6), sucking the female flowers in the normal way ; (18) Andrena fulvi-
crus, K. ? (33), cp.; (19) A. fulva, K. 9 (3), trying in vain to reach the
honey ; (20) A. albicans, K. ¢, do. ; (21) Halictus lucidulus, Schenck. 9, do.
B. Diptera—(a) Bombylide: (22) Bombylius discolor, Mgn. (12); (23) B.
major, L. (10), ab. ; both species suck, but only occasionally effect fertilisation ;
(6) Syrphide : (24) Rhingia rostrata, L. (LI—12), s.; (25) Eristalis intricarius,
L., fp. C. Lepidoptera—(a) Rhopalocera : (26) Pieris brassice, L. (15) ; (6)
Sphinges : (27) Macroglossa fuciformis, L. (Stromberg) ; (28) M. stellatarum,
L.; all three species suck, but rarely effect fertilisation. .

350. SCUTELLARIA GALERICULATA, L.—I have seen no insects
visit this flower except a butterfly, Rhodocera rhamni, L.

351. MELITTIS MELISSOPHYLLUM, L., is visited by Bombus
hortorum, L.

352. STACHYS SILVATICA, L.—The tube is 10 to 11 mm. long.
The very thick, fleshy base of the ovary secretes honey, which
fills 2 to 3 mm. of the tube, and is sheltered from rain by a ring of ©
stiff hairs which stand almost perpendicular to the wall of the
corolla. The vaulted upper lip is rather small, but, owing to the
almost horizontal position of the flower, it completely covers the
anthers and stigmas; the under lip is very large and trilobed, and
serves as a platform for the bees. The flowers, as Sprengel per-
ceived, are distinctly proterandrous; in the young flower the —
anthers are found to have dehisced on their inferior aspect while
the end of the style lies behind them, with its stigmatic branches —
very slightly divergent; in old flowers the end of the style is
curved down below the anthers and its stigmatic divisions are —
widely separated. If insect-visits occur, the fertilisation of old
flowers with pollen from young is thus rendered inevitable; in
absence of insects, self-fertilisation is frequent, as may be easily
demonstrated on plants kept in the house, for the stigmas gradually
bend down between, and come in contact with, the anthers, whose
lower surfaces are still covered with pollen. The visitors for which
the flower is especially suited are bees with a proboscis not less
than 8 mm. long; and the tube is long enough to secure the
honey against most flies. :

g

Visitors : A. Hymenoptera-—Apide : (1) Anthidium manicatum, L. ? Se
(9—10), as abundant as on Ballota nigra ; (2) Anthophora quadrimacula ¥
Pz. 2 g (9—10), do. (Thur., Sld.) ; (3) A. furcata, Pz. 9? ¢ (11—12), less freq.
(Thur.) ; (4) Bombus agrorum, F. $ 9 (10—15), ab.; (5) B. pratorum, L.
% d (8-10) ; (6) B. hortorum, L. ¢ (17—18), all sucking normally. B.
Diptera—Syrphide : (7) Rhingia rostrata, L. (11—12), s. ; (8) Xylota silyarum
L. (Warstein), trying vainly to reach the honey.

PART III. | THE MECHANISMS OF FLOWERS. 487

353. STACHYS PALUSTRIS, L. (178, 702).—The flowers differ
from those of the foregoing species in the following points: the
tube is only 8 to 9 mm. long, the outer (lateral) pair of stamens
are of equal length with the inner (median), the anthers of the
lateral pair lie, when the flower opens, in front of the median pair,
and have already dehisced while the latter are still closed; in
course of time they bend outwards and are detached by the median
ones which now come to maturity. Finally, the end of the style,
whose stigmatic branches now diverge, curves down between the
median anthers; and the stigmas, if insect-visits have failed,
come in contact with the pollen even more frequently than
in S. silvatica. |

Visitors: A. Hymenoptera—Apide: (1) Bombus silvarum, L. % (10) ;
(2) B. agrorum, F. § (10—12) ; (3) B. terrestris, L. $, (7—9); all three
sucking normally, not excepting B. terrestris, whose proboscis is too short for
Stachys silvatica! B. Diptera—Syrphide: (4) Rhingia rostrata, L., s., now
and then effecting fertilisation ; (5) Melithreptus teniatus, Mgn., fp. C.
Lepidoptera—(a) Rhopalocera : (6) Pieris brassicae, L. (15) ; (7) P. rape, L. ;
(b) Noctue : (8) Plusia gamma, L., all three ab., s.

Stachys germanica, L., according to Mr. T. Whitelegge, is
gynodicecious (774).

354. StacHys BrETonica, Benth.—The corolla-tube is 7 mm.
long, smooth internally in its lower honey-containing part, but
lined above with erect hairs. The part of the corolla within the
calyx is narrow and directed obliquely upwards; beyond the calyx
it becomes almost horizontal, remaining of the same width (about
2 mm.), and it divides into a trilobed under lip, and a flattened
“upper lip almost vertical towards its extremity. There is no need
here for a wide entrance to receive the bee’s head, on account of
the shortness of the tube. The curvature of the tube corresponds
to the natural curvature of the bee’s proboscis.

The flowers are distinctly proterandrous, but the possibility of
spontaneous self-fertilisation is not excluded. Shortly after the
flower opens, the anthers, which bear a row of white beads on their
upper surface, dehisce, while the stigmas lie between and slightly
behind the shorter anthers. Although the style has not nearly
attained its full length, yet its stigmatic divisions diverge almost
as much and are almost as well provided with papille at this
stage as they are subsequently, and pollen placed on the papille

1 Jn Sideritis romana, L., according to Delpino, these white beads apply a sticky
substance to the insect’s proboscis (178, pp. 144-146).

-

488 THE FERTILISATION OF FLOWERS. [parr 111.

adheres readily to them. As the anthers dehisce more widely and
permit the pollen to escape, the style elongates and extends be-
yond the shorter anthers, often bringing the stigmas in contact
with the pollen; finally it protrudes far beyond the anthers, and
in this position is always touched before the anthers by an insect-
visitor ; probably the pollen brought from another flower and thus

Fic. 164.—Stachys Betonica, Benth.

1.—Flower, in first (male) stage, from the side (x 23).
2.—Forepart of ditto (x 7).

3.—Flower in second (feinale) stage (x 24).
4.—Forepart of ditto (x 7).

5.—Ovary and nectary (x 7).

applied outstrips in its action that which is so often applied in the
previous stage when the stigma is making its way past the anthers.

A. Hymenoptera—Apide: (1) Bombus agrorum, F. § ? (10—15), ab., s.
B. Diptera—Syrphide: (2) Volucella bombylans, L. (7—8), ep. (Sld.) ; (3)
Eristalis horticola, Mgn. (Sld.), c.p. C. Lepidoptera—Sphinges : (4) Zygeena
loniceree, Esp., s., freq. (Thur. July 12, 1868). Additional visitors (five bees
and four Lepidoptera) are enumerated in No. 590, III.

Sideritis romana, L.—The reproductive organs are inclosed
within the tubular flower; the style is very short; the longer
stamens are of the usual form; each of the shorter stamens bears
a semicircular connective which has at one end a perfect, and at
the other a rudimentary, anther-lobe. The two connectives form
together a complete circle, through which an insect must thrust its

part ur] © THE MECHANISMS OF FLOWERS. 489

proboscis to reach the honey; adhesive matter secreted by the
outer surface of the perfect anther-lobe (which is turned towards
the centre of the ring) is thus applied to the proboscis and pollen
is then cemented to it. In the flower next visited, the hollow
cup-shaped stigma scrapes off the adherent pollen from the
proboscis (178, 360).

Marrubium, L., like Sideritis, has adhesive glands upon its
anthers. An account of the structure of its flower and a list of
its visitors are given in my Weitere Beobachtungen, U1. pp. 50, 51.

Physostegia, Benth., according to Delpino, is proterandrous, and
the stigma comes to occupy the place of the anthers. In P. virgini-
ana, teeth at the edges of the valves of the outer pair of anthers
aid the complete removal of the pollen by insects (178, 360).

355. PRUNELLA VULGARIS, L.—This species, like so many other
Labiates, includes two forms, one with large hermaphrodite, the

ho

Fic, 165.—Prunella vulgaris, L.

1.—Hermaphrodite flower, from the front.
2.—Upper part of a long stamen.
3.—Upper part of a short ditto.

other with smaller female flowers in which only rudimentary
functionless remains of the stamens persist. In Prunella vulgaris
the female form is much rarer than the hermaphrodite.

In the small-flowered form the tube is only 4 to 5 mm. long;
the style projects beyond and above the upper lip, and its two
stigmas diverge widely. I have found not only the stigmatic
papille, but the whole inner surface of the entrance of the flower
in this form, thickly covered with pollen, proving that insect-visits
were plentiful in both forms of the flower.

490 THE FERTILISATION OF FLOWERS. [PART III.

In the large-flowered form the tube is 7 to 8 mm. long; the
longer stamens divide above into two very divergent branches, of
which one, slightly shorter than the other, is turned towards the
middle line of the flower and bears the two anther-lobes ; the other
branch is turned outwards, and its pointed end rests upon the con-
cave surface of the upper lip, and insures the anthers (which dehisce
inferiorly) being in the position on either side of the stigmas where
they are most certain to be touched by a bee-visitor. Dr. Ogle
explains these processes of the filaments in a similar way (632).
The shorter stamens also divide into two branches (Fig. 165),
which are much shorter, but serve the same purpose.

Owing to the position of the anthers, the dorsal surface of the
bee comes first in contact with the stigmatic papille of the inferior
stigma, and is afterwards dusted with new pollen. In the event
of insect-visits cross-fertilisation is thus fully insured. I have
never observed spontaneous self-fertilisation in absence of insects
in any of the plants which I have kept in my room. According
to Axell, however, this plant produces seed by self-fertilisation

when insects are excluded (17).

Visitors: A, Hymenoptera—Apide: (1) Apis mellifica, L. $ (6); (2)
Bombus silvarum, L. § (10) ; (3) B. lapidarius, L. ¢ (8—10) ; (4) B. pratorum,
L. % (8); (5) B. terrestris, L. § (7—8) ; (6) Megachile Willughbiella, K. ¢;
(7) Anthophora furcata, Pz. ¢ (11—12), all sucking normally ; the females
sometimes have pollen in their baskets; (8) Cilissa hemarrhoidalis, Pz. ¢,
tried in vain to suck the large-flowered form,—it dusted itself with pollen on
the large flowers, and so in passing to the small ones, which it can suck easily, it
effected cross-fertilisation. B. Lepidoptera—Rhopalocera : (9) Lyceena argiolus,
L. ; (10) Hesperia silvanus, Esp. ; (11) Melitzea Athalia, Esp., all three sucking ;
their thin tongues enter the flower without touching the essential organs. See
also No. 590, 111., for a further list of visitorsin Low Germany. A list of Alpine
visitors (one fly, five humble-bees, ten Lepidoptera) is given in No. 609.

Prunella grandiflora, Jacq.—The four anthers lie parallel with
one another on the same level, and the two outer stamens are bent
downwards by a special mechanism as soon as a bee thrusts its
proboscis down into the flower. The unusually wide corolla-tube
- shows two shallow invaginations on each side. One pair are placed
about the middle of the corolla, in its anterior (inferior) half, and
are prolonged directly into the outer stamens which then pass
backwards and course upwards close beneath the upper lip. At
one point they are grasped by the posterior invaginations, and are
thus divided into two parts, and form levers of which the upper
arm is four times as long as the lower, the fulcrum being furnished
by the posterior invaginations of the corolla. The bee, in inserting

oe a gy eS

PART IIL. | THE MECHANISMS OF FLOWERS, 491

its proboscis through the narrow passage between the lower ends
of the outer filaments, cannot avoid touching the lower and shorter
arms of the levers; and the long arms at once bend down, bringing
the anthers in contact with the bee’s back. The median pair of
stamens only become free a little below the hood of the upper lip,
and their anthers are only touched by large humble-bees. The
flower is distinctly proterandrous.
The fertilisers are almost exclusively humble-bees (609).

356. GALEOPSIS TETRAHIT, L.—The tissue below the ovary
expands into a nectary which surrounds the two anterior divisions

Fic. 166,

1—3.—Galeopsis Tetrahit.
1.—Flower, from the front.
2.—Its essential organs, from the front (x 7).
3.—Ovary and nectary (x 7).

4—6.—G. ochroleuca.
4.—Position of the reproductive organs when the flower expands.

5.—Ditto, when it withers.

6.—Ovary and nectary.
of the ovary. The honey is lodged in the lower, smooth portion of
the tube, which ascends obliquely and is of very variable length in
different plants. In the cases which I examined it varied from 11
to1l7 mm. Fora space of 4 to 6 mm. at its upper part, this tube
is wide enough to admit the whole head of a small humble-bee, or
at least the front half of that of a large one ; so that large humble-
bees with a proboscis not less than 14 to 15 mm, long, and small
ones with a proboscis 12 mm. long, can reach the base of the tube in
the largest varieties of G. Tetrahit. The corolla divides above into a
vaulted upper lip which covers the anthers, and a trilobed under lip

which serves as a landing-place ; the under lip bears guiding-marks,

and is modified to facilitate the imtroduction of the bee’s head.

492 THE FERTILISATION OF FLOWERS. [PART LIT.

The guiding-marks or pathfinders consist of a yellow spot inter-
woven with a net of red lines at the base of the middle lobe of
the under lip. The entry of the bee’s head is aided by two convex
pouches at the base of the lateral lobes of the under lip, which rise
up on either side of the base of the middle lobe, and cause the
shape of the entrance to conform to the inferior curvature of the
bee’s head. The anthers dehisce shortly before the corolla expands,
and have their pollen-covered surfaces turned downwards like all
the other Labiatz described here. The two divisions of the style
lie at first above and behind the anthers; the upper and shorter
one, which continues the direction of the style, bears very feebly
developed stigmatic papille, while those upon the longer division,
which is bent downwards, are very conspicuous. A bee sucking
honey in a young flower touches with its dorsal surface, first the
anthers, and immediately afterwards (pushing up the anthers) the
papillar tip of the lower stigma. Usually the small part of the
bee’s back which comes in contact with the stigma lies just between
the spots that have been dusted with pollen in the same flower,
and thus cross-fertilisation is carried on.

Gradually the end of the style curves downwards, and its
lower division projects between the upper anthers, so that, if the
pollen has not already been carried away, self-fertilisation ulti-
mately occurs.

Visitors : A. Hymenoptera—Apide : (1) Bombusagrorum, F. 2 (12—15) ;
(2) B. silvarum, L. Q (12—14) ; (8) B. Scrimshiranus, K. ¢ (10), all three
sucking normally; (4) B. terrestris, L. 2, reaching the honey through holes
bitten in the lower part of the tube; (5) Andrena Coitana, K. 2 (Tekl. B.).
B. Diptera—Syrphide : (6) Melanostoma mellina, L., fp. See also No. 590,
111, and No, 609.

357. GALEOPSIS OCHROLEUCA, Lam. (Fig. 166).—The nectary
has the same position as in G. Tetrahit, but it embraces the lower
part of the two posterior divisions also of the ovary, and (while
the flower is in full bloom) it distinctly overtops the two anterior.
The tube is 18 to 20 mm. long, and wide enough in its upper 6 or
7 mm, to admit any humble-bee’s head, so that a proboscis 11 to
14 mm. long suffices to reach the honey. The corolla is yellowish-
white, with yellow guiding-marks at the base of the under lip, and
in other respects it agrees with that of G. Tetrahit.

In the relative positions of the essential organs, this species
differs from G. Tetrahit, for the stigmas extend forwards beyond
the longer stamens. The lower stigma is in consequence of this
touched before the anthers by the bee, and in course of time its

PART III. | THE MECHANISMS OF FLOWERS. 493

tip curls round under the superior lobes of the taller anthers;
so that cross-fertilisation in case of insect-visits and self-fertilisation
in their absence are insured here also, but not in the same way as
in G@, Tetrahit.

I have frequently observed Bombus agrorum, F. ¢ (12—15),
sucking the honey and fertilising the flower. Some other visitors
are enumerated in No. 590, III.

Galeopsis versicolor, Curt.—The tube is 18 to 22 mm. long, and
wide enough for a space of 6 to 8 mm. at its upper end to admit
a humble-bee’s head. <A bee, if it thrusts its whole head, 5 to 6
mm..long, into the tube, requires a proboscis 12 to 16 mm. long
to exhaust the honey, and one at least 10 mm. long even to taste
it, as the honey does not fill more than 2 or 3 mm. of the tube.
Of all our humble-bees, only B. hortorwm, L, (19—21), and the
females of B. agrorum, F. (15), B. senilis, Sm. (15), and B. fragrans,
K. (15), can drain or nearly drain G. versicolor of its honey.
Otherwise the flower resembles that of G. Tetrahit, save that the
guiding-marks are much more conspicuous ; for while the flower is
mainly yellowish-white, the under lip is dark violet anteriorly, and
yellow at its base. I have not yet observed bees visiting the
flower. Axell (17) found that when insects were excluded the
plant produced seed by self-fertilisation.

358. GALEoPsIS LADANUM, L.—The tube is 11 to 16 mm.
long, and its wide part 5 to 6 mm. ; so that in the shortest examples
a bee with a proboscis only 6 mm. long can drain all the honey
if it forces its way for a distance of 5 mm. into the tube. In
the relative positions of stigma and anthers this species exactly
resembles G. ochroleuca. In regard to the nectary and the way
in which the bee’s proboscis is guided towards the entrance of the
tube, the flower agrees with that of G. Tetrahit. I have seen the
following bees effecting fertilisation :—

(1) Bombus agrorum, F. 9 (12—15) ; (2) B. lapidarius, L. ¢ (8—10) ; (3)
B. silvarum, L. 2 (12—14); (4) Nomada Jacobeee, Pz. ? (6), all sucking
normally. See also No. 590, 111., and No. 609.

359. LAMIuM ALBUM, L.—The base of the ovary expands
anteriorly into a fleshy lobe, which secretes honey and invests the
two anterior divisions of the ovary for half their height (Fig. 167,
3, a). The base of the corolla-tube, for a space of 3 to 3} mm., is
narrow and serves to contain the honey ; it points obliquely upwards
from the stem, and is closed above by a ring of hairs. Immediately

494 THE FERTILISATION OF FLOWERS. [PART II].

above this, the tube suddenly widens, forming a pouch anteriorly,
and its direction changes, becoming parallel to the stem.
Very many short-lipped insects, especially flies and small bees,
which are too small to effect cross-fertilisation, are thus excluded ;
for Lamiwm album, like so many of our native flowers with tubes
10 to 20 mm. long, is specially adapted for humble-bees and other
large bees. The following characters of the corolla exemplify this.
The erect part of the tube, which is 7 mm. long, is followed by the
division of the tube into a bilobed lower lip (6, 1) which serves as
a landing-place, two erect lateral lobes (¢, 1) which admit the bee’s
head between them and are continued directly upwards from: the
side-walls of the tube, and the horizontal vaulted upper lip (e, 1)
which serves to shelter the anthers (f, 1) and the stigmas (g, 1)
immediately-below it. The small appendages of the lateral lobes

Fic. 167.—Lamium album, L.

1.—Flower. from the side.

2.—Ditto, after removal of the calyx.

3.—Ovary and nectary (xX 7).

4.—Tip of the style (x 7). , : :

a, nectary ; b, under lip; ¢, side-lobes which receive the bee’s head between them;
d, functionless appendages ; e, upper lip; f, anthers; g, lower division of the style.

(c, 1) are functionless rudiments of the primitive five-lobed corolla.
One of the divisions of the style which lies above or between the
anthers lies in the same straight line with the style; while the
other, a little shorter, bends downwards almost at right angles, so
that its stigmatic tip projects below the anthers (4, Fig. 167).
Cross-fertilisation is therefore induced, not by dichogamy, but by
the position of the stigma. In absence of insects, self-fertilisa-
tion may take place, but it is doubtless rare, for the flowers are
plentifully visited by bees.

We can estimate by direct observation how perfect the
adaptation of this flower is to bees’ visits. The bee alights on
the under lip, and in doing so thrusts its head between the broad
lateral lobes of the mouth, clings with its forefeet to the base

PART III. | THE MECHANISMS OF FLOWERS. 495

of the under lip, and with its mid and hindfeet to the two lobes
of the under lip; then, if its proboscis is not less then 10 mm,
long, it can at once reach the base of the flower. While sucking,
the thorax, and in the case of small workers the base of the
abdomen also, fills up the space between the upper and lower lips,
and the vaulted upper lip fits the bee’s back, which is pressed
against the stigma and the open face of the anthers. These
organs are often rubbed also by the bee’s head as it enters the
flower. In either case, the lower stigma gets touched before the
anthers, and as the bees fly diligently from flower to flower, cross-
fertilisation proceeds regularly.

The following observation shows how much this plant is visited
by humble-bees in fine weather. One fine spring morning (May
17, 1868), while I was watching Bombus agrorwm feeding on
Lamium album, I observed that by the expansion and contraction
of the bee’s abdomen each separate act of sucking could be
distinguished ; and that it was possible to tell, when a bee began
to suck, whether the flower was already exhausted of its honey.
I found that between 9 and 10 A.M.a bee of the species Bombus
agrorum abandoned four to five flowers on an average after a
single taste before it found a flower on which it performed the act
of sucking several (four to six or even eight to ten) times. By
that early hour of the day four-fifths of all the flowers of this
plant had been emptied of their honey.

Visitors : Hymenoptera—A pide : (1) Bombus agrorum, F. $ 2 (10—15) ;
(2) B. hortorum, L. § 2 (18—21); (3) B. silvarum, L. 9 (12—14) ; (4) B.
senilis, Sm. 9 (14—15); (5) B. lapidarius, § 9 (10—14); (6) B. Scrim-
shiranus, K. 2 § (10), creeping far into the flower; (7) B. Rajellus, Ill. @
(12—13) ; (8) B. pratorum, L. 9 (11—12), all sucking normally, and sometimes
brushing pollen off their backs into the pollen-baskets ; (9) B. terrestris, L.
2 (7—9), bites through the tube close above the calyx in open flowers and in
nearly mature buds; (10) Apis mellifica, L. 8 (6), only reaches the honey
through holes bitten by B. terrestris; (11) Anthophora pilipes, F. 9 ¢;
(12) Eucera longicornis, L. ¢ (10—12); (13) Melecta armata, Pz. 2 (124),
the last three sucking normally; (14) Andrena nitida, K. ? (33), s.,
through the holes bitten by B. terrestris ; (15) Andrena albicans, K. 9 ; (16)
Halictus levigatus, K. 2. I saw these last two collecting pollen ; they seemed
as likely to effect self-fertilisation as cross-fertilisation. B. Diptera—Syrphide :
(17) Rhingia rostrata, L., creeps a little way into the flower and inserts its

tongue, without touching either stigma or anthers. See also No. 590, IIL.,
and No. 609.

t Leonurus Cardiaca, ., is visited by the hive-bee and by
| humble-bees (590, 11. ; 6009). :

496 THE FERTILISATION OF FLOWERS, [PART IIT.

Lamium amplexicaule, L. (see Fig. 2, p. 19).—The tube is 14 to
16 mm. long, narrow for the lower 10 to 11 mm., and above that wide
enough to admit a humble-bee’s head. I have never seen the
flowers visited by insects, though they are no doubt cross-fertilised
by humble-bees; but I have often found, immediately after the
opening of the flower, the tip of the lower stigma standing not
above but below and between the anthers, and dusted with pollen,
—no doubt, from the same flower. Besides these normal self-
fertilising flowers, the plant reproduces itself by means of cleis-
togamic flowers, These have been described minutely by Walz
(759) and Hildebrand (351).

360. LAMIUM GALEOBDOLON, Crantz—The tube is 8 mm.
Jong, smooth in its lower, honey-holding part, but lined with hairs
above ; the entrance is expanded, and the hive-bee can reach the
base of the flower though its proboscis is only 6 mm. long. The two
branches of the style are beset with very short, flat papillae which
do not increase in size, and they diverge almost to their full extent
soon after the flower opens. Cross-fertilisation is favoured not by
dichogamy but by the position of the parts. At first the tip of the
lower division of the style lies somewhat above the lower surface
of the anthers, and hence if the bee's back presses lightly against
the anthers it escapes being touched; if the bee is large and
presses forcibly against the anthers, the stigma at least comes in
contact with a different part of the bee, and is more likely to re-
ceive pollen from another flower than its own. Afterwards the tip
of the lower stigma comes to project below the anthers, and is
now regularly touched first by the bees. I have observed,
on plants kept in the house, that, in the absence of insects,
pollen usually falls in the course of time upon the lower
stigma.

The visitors are exclusively bees.

(1) Bombus hortorum, L. 9 (21), ab. ; (2) B. silvarum, L. 9 (12—14) ;
(3) B. Rajellus, Il. 9 (12—13); (4) B. agrorum, F. 9 (13—15), very freq. :
(5) B. pratorum, L. § 9 (8—12), ab., all sucking normally, and sometimes

brushing the pollen from their backs into their pollen-baskets ; (6) B. terres-
tris, L. 9 (7—9), boring holes to suck, though its proboscis is long enough to

reach the honey in a legitimate manner ; (7) Apis mellifica, L. 8, usually 4

takes advantage of the holes bored by B. terrestris,—once I found it sucking

in the normal way, with its back thickly covered with pollen. See also No, |

590, 111., and No, 609,

361. LAMIUM MACULATUM, L., agrees in the main features of
its flower with Z. album; but its tube is 15 to 17 mm, long, so

4
=|
i
4

PART III. | THE MECHANISMS OF FLOWERS. 497

that supposing that a bee thrusts its head 5 mm. into the wide upper
part, a proboscis 10 to 12 mm. long is needed to reach the honey.

Visitors : A. Hymenoptera— Apide: (1) Bombus hortorum, L. 8 ? (18—
21), very ab., sucking normally ; (2) B. agrorum, F. 9 (12—15), do.; (3)
B. terrestris, L. 9 (7—9), bores through the corolla close above its bend, either
piercing it with its maxillz or biting a hole with its mandibles ; (4) B. Rajcllas:
Ill. § (10—11), steals the honey through holes bitten by B. terrestris, B.
Diptera—Syrphide : (5) Rhingia rostrata, L. (11—12), fp., after trying i in vain
to reach the honey. See also No. 590, I11,

362. LAMIUM PURPUREUM, L.—The tube is only 10 to 11 mm.
long, and for the upper 4 to 5 mm. it is wide enough to admit the
head of a small humble-bee. The hive-bee, though its pro-
boscis is only 6 mm. long, is thus enabled to suck the honey.
Sprengel calls the plant proterandrous ; but in all the flowers
which I have examined the stigmas and anthers developed
simultaneously, though at first the angle between the two stigmas
was less than it afterwards became, and the lower stigma stood at
first above or between the anthers, but afterwards bent down
below them. To decide whether the stigma is already capable of
fertilisation when the flower opens, I set a plant of L. purpwreum
in a pot (April 26, 1871), and removed all the flowers and capsules
already present on it. Next morning five flowers had just opened ;
in each I bent back the upper lip and the four anthers, and cut the
latter off ; I then placed upon the two stigmas (the lower of which
received in this process some pollen of its own flower) pollen from
freshly opened flowers of another plant, and I then marked my
flowers with a spot of ink upon the calyx. The rest of the flowers
I kept in my room, untouched and protected from insects. All the
flowers were perfectly fertile. On May 21 the twenty nutlets of
the five flowers which I had fertilised on April 27 had all fallen
out, and I succeeded in finding them all. On June 8 I collected
on the surface of the pot seventy-eight nutlets which had fallen
from the self-fertilised flowers. Lamiwm purpureum is, there-

} fore, certainly homogamous, and in default of insect-visits fertilises

) itself regularly.

Visitors: A. Hymenoptera—Apidw: (1) Apis mellifica, L. § (6); (2)
Anthophora pilipes, F. 9 § (19—21); (3) Bombus hortorum, L. ? (21); (4)
_ B. pratorum, L. 2 (114) ; (5) B. agrorum, F. 9 (12—15) ; (6) Melecta armata,
Pz. 2 (124), all sucking in the normal way, and sometimes brushing off the
pollen from their heads into their collecting-baskets ; (7) Halictus sexnotatus,
_K. 9 (4); (8) H. cylindricus, K. 2 (3); (9) H. leucopus, K. 92; these three
_ try in vain to reach the honey, and abandon the plant after a few attempts. B.
Diptera—Bombylide : (10) Bombylius major, L. (10), s. See also No. 590, m1.

K K

498 THE FERTILISATION OF FLOWERS. [PART I1I.

363. LAMIUM INCISUM, Willd. :—

Visitors: Hymenoptera—Apide; (1) Anthophora pilipes, F. 9 ¢ (19—
21), ab. ; (2) Bombus pratorum, L. 2 (114); (3) B. Rajellus, Ill. 9 (12—138) ;
(4) heute mellifica, L. % (6), all sucking normally ; (5) Halictus cylindricus,
K. 9. (3), trying in vain to reach the honey.

364, BALLoTA NIGRA, L.—The corolla-tube is only 7 mm.
long ; above, it widens so little that a hive-bee can only insert
the anterior part of its head, and can just reach the base of
the flower with its proboscis, which is 6 mm. long. Two milli-
metres from its base the tube is blocked by a ring of stiff
hairs, which permit the bee’s proboscis to pass easily. They
would suffice to exclude rain-drops, and are described by Sprengel

Fic. 168.—Ballota nigra, L.

i.—Essential organs of a young flower, viewed obliquely from the front (x 7).
2.—Ditto, of an older flower.
3.—Ovary (ov) and nectary (7).

as serving that purpose; but as the horizontal position of the
flower and its vaulted upper lip are sufficient protection against
rain, their true use seems to be to exclude flies. Since flies pro-
ceed irregularly for the most part in visiting flowers, those species
whose proboscis is long enough to reach the honey of Ballota
(Rhingia, Hristalis, etc.) might rob many flowers of their honey
without fertilismg them; but the ring of hairs is sufficient to
prevent the expanded end of a fly’s proboscis from entering.

The under lip is marked with white guiding-lines which point

towards the mouth of the tube; its broad central lobe serves as a

landing-place, the clefts between it and the lateral lobes afford

firm foothold for the forelegs and midlegs of the bee, and the

lateral lobes with the groove between them, bounded by two
longitudinal ridges, guide the bee’s proboscis.

Decale, a v |

———s

PART III. | THE MECHANISMS OF FLOWERS. 499

Cross-fertilisation is favoured by the feebly-marked proteran-
drous dichogamy, and by the relative positions of stigma and
anthers. At first, the divisions of the style lie close together
behind the anthers (1, Fig. 168) ; afterwards, when the pollen is
removed, they diverge more and bend down in front of and below
the anthers (2, Fig. 168). In sunny weather bees’ visits are so
plentiful that all the pollen is removed before the stigmas diverge
and bend downwards. During rainy weather, and in plants kept
in the house, great part of the pollen as it escapes from the anthers
remains adhering to the long woolly hairs which cover the under
surface of the upper lip, and the inferior stigma curving down-
wards among these hairs becomes covered with the pollen of its
own flower.

Visitors: A. Hymenoptera—Apide: (1) Apis mellifica, L. $,s. (6) ; (2)
Bombus Rajellus, Ill. 9 (12—13), s. ande.p. ; (3) B. silvarum, L. (10—12), s. ;
(4) B. lapidarius, L. § (10—12), s.; (5) B. hypnorum, L. § (10—11), s.; (6)
B. muscorum, F. 9 (13—14), s. ; (7) B. (Apathus) rupestris, F. 9 (11—14),
s.; (8) Anthophora quadrimaculata, Pz. 9 ¢ (9—10), s. and ¢.p., very ab. ;
(9) A. furcata, Pz. 9 g, 8. ande.p., scarcer (Thur.) ; (10) Osmia aurulenta, Pz.
Q (8—9),s. (Thur., Sld.) ; (11) O. enea, L. 2 (9—10),s. ; (12) O. fulviventris,
Pz. 9, s. (Thur.); (13) Anthidium manicatum, L. 9 ¢, wherever Ballota
grows, very ab, in sunny weather, the females diligently collect pollen and
suck honey, while the males buzz about and occasionally descend to suck honey
on a flower ; (14) Megachile pyrina, Lep. (fasciata, Sm.) 2, s. B. Lepidoptera
—(a) Rhopalocera: (15) Argynnis Paphia, L.; (16) Vanessa urticee, L. (12) ;
(17) V. cardui, L. ; (18) Pieris brassice, L. (15) ; (19) P. rapee, L. ; (20) Colias
hyale, L. ; (b) Sphinges : (21) Macroglossa stellatarum, L. ; all these Lepidoptera
were sucking ; the specimens I caught had their tongues dusted with pollen
and were probably effecting fertilisation. See also No. 590, m1.

In Prostanthera, Labill., long two- or three-toothed appendages
of the connectives come in contact with the insect and cause

shedding of the pollen (178, 360).

365. TEucRIUM ScoroponiA, L., is markedly proterandrous.!

_ When the flower opens, the stamens protrude from it, lying close
_ to the superior wall of the tube, and continuing in a line with it,

or bending slightly forwards. The two divisions of the style are
already separate but stand behind the stamens so that they escape

_ being touched by the head of a bee visiting the flower; the
anthers, which dehisce inferiorly by a longitudinal slit, shed their

1 The proterandry of Teweriwm and the movements of its reproductive organs

' ~ aebe ay described’ by Delpino, No. 178, Hildebrand, No. 360, pl. x., and Ogle,
No. 632.

Rk 3

500 , THE FERTILISATION OF FLOWERS. [PART III.

pollen on the bee’s head. Gradually the filaments bend backwards
(2, 1, Fig. 169) out of the bee’s way, while the two stigmas spread
more and more apart, bending slightly forwards into the place
where the anthers were before. In absence of insects, self-fertili-
sation rarely takes place, for the stamens as a rule do not touch
the stigmas; yet in a good many flowers the anthers come in
contact with the stigmas in oncom. backwards, and dust them
with pollen.

Honey is secreted by the tissue below the ovary, as in all the
Labiates that I have examined (cf. Fig. 168, 3), and so plentifully
that the corolla-tube (which is 9 to 10 mm. long) is often filled
to a depth of 4mm. The flowers are rendered conspicuous by

Fic. 169.—Teucriwm Scorodonia, L.

1.—Flower, in first (male) stage (x 33).
2.—Ditto, at the beginning of the second (female) stage.
3.—Ditto, at the end of the second stage.

aggregation, and in spite of their dull colour they are so abundantly

visited by insects as to. be able to dispense with the power of self- _

fertilisation.

Visitors : A. Hymenoptera—Apide: (1) Bombus pratorum, L. § 9 (8—
114), s., very ab. ; (2) B. agrorum, F. $ 9 (10—15), do. ; (3) B. hypnorum,
L. ¢ (10), s.; (4) Anthophora quadrimaculata, Pz. 9 (9—10), s.; (5) Saro-
poda bimaculata, Pz. 9 ¢ (9), very ab., s. B. Diptera—Syrphide : (6) Eri-

stalis nemorum, L., f.p., and thus only able to effect fertilisation occasionally. —

It is noteworthy that the honey-bee (whose proboscis is 6 mm. long), was not
observed on this abundantly nectariferous flower. It would be just able to
taste the honey. See also No, 590, 111.

According to Dr. Buchanan White, Zeucriwm Scorodonia is

visited by many nocturnal Lepidoptera (773).

PART III. | THE MECHANISMS OF FLOWERS. 501

Teucrium Chamedrys, L., is proterandrous; the movements of
the reproductive organs are similar to, but feebler than, those of
T. Scorodonia, 'The visitors are bees, and a proboscis 7 to 10 mm.
long is requisite to reach the honey (609).

Teucrium Botrys, L., is visited by species of Anthidium

(590, II).

366. AJUGA REPTANS, L.—The tube is 9 mm. long, and is
expanded for 24 mm. at the base; the lower expanded part is
white, and full of honey, which is secreted by a thick, yellow,
fleshy gland below the ovary on the side turned towards the under
lip. The upper lip is absent, but the protruding anthers of each
flower are sheltered by the bract of the flower above. When
the flower opens, the two stigmas diverge to their full extent
and their papillae are already mature. Cross-fertilisation is
favoured not by dichogamy but by the position of the organs.
For in young flowers the lower division of the style, provided at
its tip with stigmatic papille, rests upon the shorter stamens
which lie close together, and is protected by them from contact
with the bee visitors, at least in the case of the smaller bees which
do not force the stamens much apart; while all the anthers turn
their pollen-covered faces forwards and downwards so as to touch
all insect-visitors. Afterwards the inferior stamens separate, the
style loses their support, and its lower division, with the stigmatic
tip turned downwards and forwards, projects between the anthers,
and is touched before them by the bee.

In absence of insects, the pollen remains adhering to the
lower surface of the anthers in large masses, which readily come
in contact with the stigma and effect self-fertilisation.

Visitors : A. Hymenoptera—Apide: (1) Apis mellifica, L. 9 (6), thrusts
the greater part of its head into the tube; (2) Bombus lapidarius, L, 9?
— (12—14) ; (8) B. agrorum, F. 2 (12—15) ; (4) B. confusus, Schenck, ? (12—14);
_ (5) B. muscorum, F. 9 (13—14) ; (6) B. pratorum, L. § (8) ; (7) B. silvarum,
iL. 2 (12—14); (8) B. hortorum, L. 9 $8 (18—21) ; (9) Anthophora pilipes, ‘F.
2 S$ (19—21) ; (10) Osmia rufa, L. ¢ (7—8) ; (11) O. enea, L. 2 (9—10) ;
_ (12) O. fusca, Christ. (=bicolor, Schrk.), all sucking normally and dusting
their heads with pollen ; (13) Andrena nitida, Foure. 2 (34) ; (14) A. labialis,
K. &; (15) Halictus zonulus, Sm, 2 (4); these three are unable to reach the
honey, and abandon the plant after visiting a few flowers. B. Diptera—Syr-

_ phide : (16) Rhingia rostrata, L. (11—12), usually s. and f.p. on the same flower,

while sucking it dusts its head with pollen. C. Lepidoptera—(a) Rhopalocera :
(17) Pieris brassicee, L. (15) ; (18) P. napi, L.; (19) P. rape, L. ; (20) Rho-
docera rhamni, L. (15—16); (21) Papilio Podalirius, L.; (22) Hesperia

502 THE FERTILISATION OF FLOWERS. [PART III.

alveolus, H ; (b) Sphinges : (23) Macroglossa fuciformis, L. (Stromberg), all
sucking. See also No. 590, III.

Ajuga pyramidalis, L., is said by Ricca to be homogamous
(665); I have found it slightly proterandrous, and visited by
humble-bees (609).

Ajuga genevensis, L.—The flowers are larger than those of A.
pyramidalis, and the nectary is very large. The plant is visited
by humble-bees and by Lepidoptera. A proboscis 7 to 8 mm. long
is requisite to reach the honey (609). 3

REVIEW OF THE LABIATAE.

Delpino mentions the following six points as characteristic of
the flower in Labiatz (178).

(1) The horizontal position of the axis of the flower. (2)
Division of the corolla into upper and lower lips. (8) Union of
two petals in the upper lip, three in the lower. (4) Position of
anthers and stigma below the vaulted upper lip, which shelters
them. (5) Position of the nectary at the base of the flower below
the lower lip, whose anterior part forms a platform for insects.
(6) Well-marked dichogamy (“ deciso asineronismo nello sviluppo
degli organi sessuali”) (Delpino, No. 178, p. 128; Hildebrand,
No. 360).

But this summary is only correct if we call only those Labiates

typical to which it directly applies; it requires most important —

modifications if it is to hold good for the majority of Labiates.
For (1) the axis of the flower is never or hardly ever truly
horizontal, but, as a rule, is rather bent into the curve most
convenient for long-tongued bees (Lamium, Galeobdolon, Gale-
opsis, Betonica, etc.). (2) The upper lip is entirely absent in
many cases (Ajuga, Teucrium), bracts belonging to the flowers

above taking its place in sheltering the stamens from rain. (3) |

The under lip is by no means always formed of three petals, but
in Lamium, for instance, consists of one only; the two lateral

petals have here assumed a special function, forming two erect 4
lobes which receive the bee’s head between them. (4) The ©

stamens project beyond the corolla not only in Ajuga and
Teucrium, where the upper lip is absent, but also in Thymus,
Lycopus, Mentha, etc., and the stigma also projects beyond the

a ee

corolla in Salvia. (5) The fifth statement is correct for the great —

parr ut,] THE MECHANISMS OF FLOWERS. 503

majority, Plectranthus, Ocymum, Salvia patens, etc., being - ex-
ceptions to it. (6) Dichogamy has been shown above to be far
from universal : Ajuga, Lamium, Galeopsis, and others are homo-
gamous, and even in the majority of the others dichogamy is
not so complete as to prevent self-fertilisation. Self-fertilisation
seems to be rendered impossible only in the species, of Nepeta,
Thymus, Mentha, and Salvia described above.

In regard to the imsects which the Labiatz have adapted
themselves to, the forms which I have described show a re-
markable series of gradations, the visitors being more and more
restricted as the length of the corolla-tube increases.

The short-tubed flowers of Mentha and Lycopus are visited
chiefly by flies and also by insects of various other orders. In
Thymus and Origanum, in addition to flies, bees come more and
more to the front, though insects of other orders take a certain share ;
in Betonica bees and flies are of about equal importance as fer-
tilisers; in Stachys palustris and S. silvatica bees are very much
the most important visitors, and in Lavendula, Salvia, Galeobdolon,
Lamium, Galeopsis, Ballota, Teucrium, and Ajuga bees perform
almost all the work of fertilisation, though Lepidoptera and
long-tongued flies are not excluded.

Orv. PLANTAGINEZ.

367. PLANTAGO LANCEOLATA, L.—Delpino (567) distinguishes
three forms of this species :—

“One form,” he says, “with a strong and very tall scape, and very broad,
white anthers which quiver in the wind, grows in meadows and is exclusively
anemophilous, for I have never seen it visited by insects. The second form
grows on the hills, and has a much shorter scape ; it also is essentially anemo-
philous ; I once saw a species of Halictus on a spike, trying to gather pollen ;
but the structure of the flower is so unfitted for pollen-collecting, that great
part of the pollen fell to the ground without benefiting either the plant or the
insect. Finally, the third form is dwarfish and confined to the mountains ;
it has the shortest spikes and filaments ; on meadows in the Apennines at
Chiavari I have seen bees in numbers flying from one flower to another of this
variety, collecting the pollen and performing cross-fertilisation.

‘This therefore is a form of Plantago which hangs between the anemo-
philous and entomophilous conditions, and is capable of being fertilised equally
well by the wind and by bees. If the filaments became stiff and coloured and
the pollen-grains adhesive while the anthers lost their peculiar quivering,
we should have before us the passage from anemophilous to entomophilous
characters, the evolution of an entomophilous from an anemophilous species. _

“This hypothetical transition has actually occurred. Plantago media is a

504 THE FERTILISATION OF FLOWERS. [PART 111.

form that has become entomophilous ; the filaments have become pink, the
anthers are motionless, the pollen-grains have become more aggregated, and it
is visited regularly by Bombus terrestris, as I have observed at the same spot
(Chiavari) in the Apennines.”

I have transcribed this passage in order to induce botanists in
as many places as possible to observe the forms of this species
with reference to its adaption for insect-visits. .

In the neighbourhood of Lippstadt I have caught pollen-
collecting bees and pollen-feeding flies both on plants with tall

Fia. 170.—Plantago lanceolata, I.

1.—Flower, in first (female) stage. The petals and stamens are still within the bud.
2.—Ditto, after removal of the calyx.

8,—An anther from this flower.

4.—F lower, in second (male) stage.

5.—The two inferior coherent sepals,

6.—A lateral sepal.

scapes and long spikes and on those with short scapes and spikes ;
and in neither form have I found the least trace of adaptation to
insect-visits. Delpino’s account is not minute enough to permit
a correlation of his plants with those of other localities, and it is
quite possible that the varieties which he has observed do not
occur at Lippstadt.

It is just possible that Delpino has been led into imagining
adaptations which have no real existence by the success which the
honey-bee attains in gathering pollen, chiefly owing to its plan of
smearing the pollen with honey. The two extreme forms of P.

— eile

part ut] THE MECHANISMS OF FLOWERS. 505

lanceolata which I have gathered at Lippstadt, and on which as
well as on the intermediate forms I have observed pollen-collecting
insects, are: (1) a short form with short spike from the sunny
caleareous slopes of the Rixbecker Hill; (2) a tall, long-spiked
form from the rich alluvial meadows of the Lippe.

(1) In the most stunted specimens from the hill the scape
is scarcely four inches long, the spike is spherical, about 5 mm. in
diameter, and the individual flowers are convex anteriorly, and
flat or slightly concave on the side turned towards the axis; of the
four sepals the two inferior are coherent almost to the tips (Fig.
170, 5). While the lobes of the corolla are still erect, contiguous
(Fig. 170, 2), and covered by the sepals (1), and while the stamens are
still inclosed in the bud, with their anthers not nearly ripe and their
filaments scarcely beginning to develop (3), already the stigma is
tully mature, and protrudes for more than 1 mm. beyond the bud
(Fig. 170, 1, 2). As the stigma becomes withered and brown,
the filaments begin to grow rapidly, and the other parts of the
flower more slowly. At length the lobes of the corolla fold back,
and the stamens with the now ripe anthers protrude 5 to 6 mm.
from the flower, which is itself now 3 (in the female period only 2)
mm. long (Fig. 170, 4). The filaments are quite straight, but thin
and flexible enough to be swayed backwards and forwards by the
slightest breeze, scattering a cloud of dry pollen. Nevertheless,
this pollen is collected by the honey-bee. The pollen-grains are
smooth, ‘016 to ‘(020 mm. in diameter when dry, and swelling to
a diameter of ‘021 to ‘026 mm. when moistened.

(2) The tall form from the manured alluvial meadows has
a scape a foot to eighteen inches long, a spike 15 to 30 mm. long,
and stamens projecting 6 to 7 mm. from the flower. In the com-
plete proterogynous dichogamy, in the cohesion of the two lower
sepals, in short in all other characters, it agrees perfectly with the
dwarf form from the Rixbecker Hill. I have observed pollen-
seeking insects indifferently on both extreme and intermediate
forms.

A. Hymenoptera—Apide : (1) Apis mellifica, L. $, very ab.,c.p. I wrote
the following account of the honey-bee’s actions in the summer of 1868, and
assured myself of its accuracy in the three following summers: ‘‘ The honey-
bee flies buzzing to a spike, and while it hovers in the air it spits a little honey
on the exserted anthers. Then, still hovering and buzzing, it brushes pollen with
the tarsal brushes of its forefeet off the anther, the tone of its hum becoming
suddenly higher ; in the same instant one sees a)cloud of pollen rise from the
shaken anthers. After placing the pollen on ith hindlegs the bee repeats the
operation on the same or other spikes, or if it is tired it alights on the spike

506 THE FERTILISATION OF FLOWERS. [PART III.

and creeps upwards, Since the scattered pollen in part reaches the stigmas of
the same or neighbouring plants, we have here anemophilous flowers fertilised
also by insects.” (2) Bombus pratorum, L. §, c.p. ; (3) Small sp. of Halictus, busy
about the anthers. B, Diptera—Syrphide : (4) ‘Melanostomns mellina, L., very
ab., f.p.; (5) Syrphus ribesii, L., f.p., freq. ; (6) Volucella pellucens, Li: f.p.
Whonevar I have examined bees acide on P. lanceolata I have always fotki
numerous pollen-grains among the feathered hairs, See also No. 590, 111.

Darwin found P. lanceolata to be gynodiccious in England

(167).

Plantago alpina, L.—The stigma does not wither until after
the ripening of the anthers, so that the plant retains the power
of self-fertilisation. The limb of the corolla, and sometimes the
borders of the sepals, are red, which is perhaps an adaptation
favouring insect-visits. The tendency towards homogamy is
probably also brought about by insect-visits, as the insects come
only for the sake of pollen, and therefore seek only flowers with
ripe anthers (No. 6009, fig. 139).

368. PLANTAGO MEDIA, L.—While I have been unable to find
any trace of adaptation to insect-visits in the various forms of
P. lanceolata, specimens of P, media which I have examined seem
to show such traces in the reddish colouring of the filaments and
the pleasant perfume of the plant. Nevertheless, in all the forms
of this species the filaments are so long, thin, and freely motile,
the anthers so broad, and the pollen-grains so smooth and dry,
that wind-fertilisation can be effected very readily. P. media,
therefore, is truly intermediate between the anemophilous and
entomophilous conditions.

In the neighbourhood of Lippstadt P. media exhibits variability
such as Delpino describes in the case of P. lanceolata. It seems
remarkable that the form A, which I have observed on dry sunny
road-sides, is adapted in a less degree for insect-visits than the
form 2B, which grows in more shady spots; but I must add that
a form agreeing essentially with B, but much taller, grows on the
sunny slopes of the canal-enbankment at Lippstadt, and is much
visited by insects there.

The form A has a scape 8 to 12 inches in length, and a spike
about 40 mm. long, increasing during the flowering period to
70 or 80 mm. The filaments, which are bent down slightly by the
weight of the anthers, are white, and protrude for 7 to 9 mm. from
the flower; the lobes of the corolla are acute and outspread ; the

part] § THE MECHANISMS OF FLOWERS. 507.

stigmas protrude far beyond the flower. The form Bon the other
hand has a scape about 6 inches long, and shorter reddish filaments
which do not bend under the weight of the anthers; the lobes of
the corolla are rounded, and do not spread apart but only point
obliquely upwards, and the stigmas protrude little from the flower.
The pollen in both forms is powdery, but is slightly more adhesive
in the second form (B), as may be seen by the filaments in this
form being usually covered thickly with pollen-grains.

Fig. 171.—Plantago media, L.

A, 1—5.—A form of P. media from dry sunny slopes on Rixbecker Hill, near Lippstadt.

1, bud; 2, developing flower ; 3, fully developed flower; 4, corolla; 5, pistil.

8, Sepal; p, petal; a, anther; st, stigma.

B. 6—8.—Another form of P. media, growing in damp shady spots on the same hill, often within
a few paces of the other. ,

6, fully developed flower ; 7, corolla; 8, pistil.

The form growing on the slopes of the canal-embankment,
from which I have chiefly compiled my list of insect-visitors, has
a scape 10 to 14 inches long, a spike 35 to 90 mm. long, and
stamens which project only 4°5 to 7 mm. beyond the flower; in the
form and development of the corolla and style and in the nature

of the pollen it agrees well with the form B from the Rixbecker
Hill. )

508 THE FERTILISATION OF FLOWERS. [PART IIT.

All the specimens of P. media that I have examined were less
markedly proterogynous than P. lanceolata, for the stigmas are
always still fresh after the anthers have shed their pollen; but
various forms of P. media differ greatly in this respect, as may be
seen by comparing 3 and 4, Fig. 171.

The foregoing remarks are simply intended to call the attention
of botanists to forms of P. media intermediate between the
anemophilous and entomophilous conditions, and so to lead to more
thorough investigation ; I do not by any means suppose that they
exhaust the subject.

Visitors: A. Hymenoptera—A pide’: (1) Bombus terrestris, L. 2, ¢p.,
ab. ; (2) Eucera longicornis, L. ¢, seeking vainly for honey (attracted by the
scent?) ; (3) Halictus albipes, F. 9; (4) H. cylindricus, F. 2, both freq. ;
(5) Andrena, 2 (moderate size), do.; (6) Megachile circumcincta, K. 9.
B. Diptera—(a) Syrphide : (7) Melanostoma mellina, L., I once saw this fly
hovering for a long time over many flowers, until it came to P. media, on
which it settled at once, and began to stroke the anthers with its labelle (f.p.) ;
(8) Ascia podagrica, F., f.p.; (9) Syrphus balteatus, Deg., f.p.; (10) Eristalis
arbustorum, L., very ab., f.p. ; (11) Rhingia rostrata, L., fp. ; (6) Muscide :
(12) Spilogaster semicinerea, Wied., very ab., f.p.; (c) Stratiomyide: (13)
Chrysomyia formosa, Scop. C. Coleoptera—(a) Nitidulide : (14) Meligethes,
freq. ; (b) Malacodermata: (15) Anthocomus fasciatus, L.; (16) Malachius
eneus, L., both freq., gnawing the anthers; (c) Cerambycide : (17) Strangalia
nigra, L., do. See also No. 590, 111., and No. 609.

Ludwig has found P. media to be gynodicecious in Germany.

Some species of Plantago have cleistogamic flowers according
to Kuhn (399).

Ludwig has discussed in several papers the occurrence of
cleistogamy, gynodicecism, and heteranthery (.¢. the existence of
different forms bearing anthers of different lengths) (425, 429,
430, 431).

Orv. NYCTAGINEZ.

Pisonia hirtella is proterogynous, according to Delpino. The
stigmas in the first stage, and the anthers in the second, protrude
some millimetres beyond the tubular corolla (177).

. Oxybaphus and Nyctaginea have cleistogamic flowers (Asa Gray,
No. 167).

Neea theifera, Oer.—The diclinous flowers have been desorihad
by Warming (762) and Oersted.1

Mirabilis Jalapa, l., is eagerly visited by Sphina convolvuli
(590, II.).

1 Bot. Zeit, xxvii. pp. 217-222, 1869.

PART III. | THE MECHANISMS OF FLOWERS. 509

Orv. ILLECEBRACEL,

Lllecebrum verticillatum, L., has submerged cleistogamic
flowers (351).

Herniaria glabra, L.—The flowers are very inconspicuous, and
are visited by minute insects (590, II.).

Scleranthus perennis, L.—The small inconspicuous flowers have
no petals; the sepals, which are white at the edges, take the place
of a corolla; the honey, which is secreted in the lower half of
the calyx, is accessible to short-lipped insects. Anthers and
stigmas ripen together, and the widely outspread position of the
stamens favours cross-fertilisation. I have found Hedychrum
coriacewm, Dhlb. (Chryside), sucking honey in the flowers.

Orv. AMARANTACE LZ.

Chamissoa affords an example of the passage from a dimorphic
to a diclinous condition (555).

Orv. CHENOPODIACEZ.

Chenopodium ambrosioides is figured by Hildebrand as an
example of a self-fertilised plant (351).

Chenopodium album, L., is anemophilous, but is visited by
pollen-eating Syrphide (Melanostoma mellina, L.) (590, 11.).

Chenopodium bonus-Henricus is proterogynous according to
Warming (762).

Orv. POLYGONACE LZ.

369. PoLyGoNuM FAGoPyRUM, L.—The flowers are made con-
spicuous by their white or red perianth, by aggregation, and by
their perfume. Eight rounded yellow glands at the base of the
stamens secrete honey, which lies at the bottom of the shallow
outspread perianth ; it is accessible to short-lipped insects, and
attracts great numbers of insects of different orders.

Three stamens, with their pollen-covered sides turned outwards,
stand close round the styles in the middle of the flower; five, with
their pollen-covered sides directed inwards, stand round the cir-
cumference. The eight nectaries lie at the bottom of the flower
between the inner and outer stamens, so that insects must come
between these to reach the honey, and hence get dusted with

510 THE FERTILISATION OF FLOWERS. [PART III.

pollen on both sides. This species is dimorphic, and in this respect
it stands alone in its genus. The anthers stand in the one form
on a level with the stigmas in the other, and there is the usual
difference in the size of the pollen-grains. In long-styled flowers
(Fig. 172, 1), most visitors touch the anthers with their heads, and
the stigmas with the sides or ventral surfaces of thorax and abdo-
men. ‘The converse takes place in the short-styled forms, so that
legitimate fertilisation for the most part takes place, though neither
illegitimate crossing nor fertilisation of a flower with its own pollen
are quite prevented.

The smaller visitors, ¢.g. Andrena nana, which creep about
irregularly in the flower, may lead to self-fertilisation and legiti-
mate or illegitimate crossing indifferently.

Fic. 172.—Polygonum fagopyrum, L.
1.—Long-styled, 2.—Short-styled flower, after removal of two segments of the perianth.

Occasionally flowers occur on long-styled plants, in which the
style is so much shorter than usual that the stigmas lie between
the three inner stamens and get dusted by their pollen.

Self-fertilisation is probably inoperative under ordinary circum-
stances in the Buckwheat, but under altered conditions, if insect-
visits decreased, it might easily come into play (cf. Darwin, 167,
p. 113).

The following insects were almost all collected by me on
Buckwheat, one sunny day, in a large field near Salzkotten (June
21, 1868),

A. Hymenoptera—-(a) Apide: (1) Apis mellifica, L. $, very ab., s. and
c.p., making fully nine-tenths of all the visitors ; (2) Bombus lapidarius, L.
2%, s.; (3) Andrena fulvicrus, K. ¢ 2, ab., s. and c.p.; (4) A. dorsata, K.
2; (5) A. pilipes, F. 9; (6) A. helvola, L. 9; (7) A. varians, Rossi, 9 ; (8)
A. albicrus, K. 9; (9) A. Gwynana, K. 9; (10) A. nana, K. 9; (11) A.
bicolor, F. (estiva, Sm.), ¢; (12) Sphecodes gibbus, L., Nos. 4—12, sucking
only ; (b) Sphegide : (13) Pompilus trivialis, K1. ; (14) Cerceris labiata, F. 9 ;
(15) C. nasuta, Dib. (C. quinquefasciata, Ross.), ¢, all s.; (c) Tenthredinide :

part u1.] THE MECHANISMS OF FLOWERS. 511

(16) Athalia spinarum, F.,s. B. Diptera—(a) Syrphide: (17) Eristalis tenax,
L. ; (18) E. pertinax, Scop. ; (19) E. nemorum, L. ; (20) E. arbustorun, L. ;
(21) E. sepulcralis, L. ; (22) E. intricarius, L. ; all ab., s. or fp. ; (23) Helo-
philus floreus, L. ; (24) Syritta pipiens, L. ; (25) Chrysotoxum festivum, L. ;
(26) Melithreptus scriptus, L. ; (27) M. teniatus, Mgn. ; (28) Syrphus py-
rastri, L. ; (29) Pipiza funebris, Mgn. ; (30) Cheilosia scutellata, Fallen ; (6)
Muscide : aH) Pollenia Vespillo, F. ; (82) Musca corvina, F. ; (33) Lucilia
cornicina, F. ; (34) Sarcophaga carnaria, L. ; (c) Stratiomyide : (35) Odon-
tomia viridula, F. ; (36) Stratiomys Chameleon, Deg., ab. ; (37) Str. riparia,
Mgn. ; most of these flies sucking, the Syrphidee also eating pollen. C. Lepido-
ptera—(38) Vanessa urtice, L.; (39) Pieris brassice, L. ; (40) P. napi, L. ;
(41) Polyommatus Phlceas, L., all s.

370. Potyconum Bistorta, L.—As in P. jfagopyrum, the
flowers are made conspicuous by aggregation and by their coloured

Fic. 178.—Polygonum Bistorta, L.

1.—Flower, in first (male) stage.
2.—Ditto, in second (female) stage.

perianth; eight red swellings at the base of the stamens. secrete
honey, which lies freely open at the bottom of the flower. The
power of self-fertilisation has been lost; but while in P. fagopyrum
crossing has been insured by the development of long-styled and
short-styled stocks, in P. Bistorta the same end has been gained by
complete proterandrous dichogamy. In the first stage, the anthers
protrude freely from the flower, which never expands very widely ;
afterwards, when the anthers are withered and mostly fallen off,
the ends of the styles with their stigmas protrude. |

On the meadows at Brilon, I saw the flowers plentifully visited
by flies, but I was busy with other observations and can name
only the following easily recognised forms: Rhingia rostrata, L.,

512 THE FERTILISATION OF FLOWERS. [PART III.

Volucella bombylans, L., and Syrphus ribesii, L. All three settled
upon the spikes, thrusting their tongues into one flower after
another, and so dusting their ventral surfaces with pollen.

In my garden I have often seen Sarcophaga carnaria trying to
insert its proboscis into the flowers, and generally failing in the
attempt. Syritta pipiens, L., always failed in the same attempt ;
if the flower happened to be in the second stage, it flew away
after a few failures, but stayed to eat pollen if the flower was in its
first or male stage.

I have often seen Andrena albicans, L. ¢, climbing up the
spikes. Now and then I have watched an individual first failing
continually on several spikes to insert its proboscis into the flowers,
and then gradually acquiring the knack, and ending by performing
the operation regularly.

The honey-bee visits the plant in considerable numbers, and
never fails to insert its proboscis successfully.

Visitors in Low Germany: A. Hymenoptera—Apide : (1) Apis mellifica,
L. %; (2) Andrena albicans, lL. 9. B. Diptera—(a) Syrphide : (3) Volucella
bombylans, L. ; (4) Syrphus ribesii, L. ; (5) Syritta pipiens, L. ; (6) Rhingia
rostrata, L. ; (6) Muscide: (7) Sarcophaga carnaria, L. See also No. 590, m1.

A list of Alpine visitors (one beetle, ten flies, five Hymenoptera, twenty-one -
Lepidoptera, and Panorpa communis) is given in No. 609.

Polygonum viviparum, L., is remarkable for the polymorphism
of its flowers. In Sweden, Axell found it occurring in two forms,
some plants being hermaphrodite and proterandrous, others female
only (17). I have also found hermaphrodite and female forms at
Franzenshoh, but the former were homogamous. At Madulein I
found hermaphrodite stocks showing all stages of suppression of
the pistil down to purely male flowers and plants (609, fig. 169).

371. Potyconum Perrsicaria, L.—Like the two foregoing
species, the flowers have white or red perianths; they are
aggregated in a spike 20 to 30 mm. long and 6 to 10 mm. broad.
The smaller size of the flower and of the spike, the want of
odour and much smaller supply of honey, render insect-visits very
much rarer. It is, therefore, of more importance for self-fertilis-
ation to be possible in default of insect-visits, than for cross-
fertilisation to be absolutely insured when insect-visits do take
place. Accordingly, the structure of the flower differs considerably
from that of the two preceding species.

Of the eight stamens three at most are much reduced or have
entirely disappeared, though flowers often occur with six, seven, or

PART III. | THE MECHANISMS OF FLOWERS. 513

eight stamens. The five which are constantly present alternate
with the parts of the perianth ; the other three stand opposite to
the parts of the perianth. At the base of each perianth-segment
is a nectary, secreting very scanty honey, which remains in a
moist adhesive layer. The ovary is generally bilateral, bearing
a style which divides into two branches, each bearing a stigmatic
knob; but three stigmatic branches often occur. Anthers and
stigmas ripen together and stand at the same level. The flower
expands until the perianth forms an almost hemispherical cup,
and the five stamens alternating with the perianth-segments
spread out as far as the perianth allows. The stigmas are, there-
fore, seldom or never touched by these stamens, but the other
three stamens, when present, bend towards the middle of the
flower and come in contact with the stigmas. Now although, as in

Fic. 174.—Polygonum Persicaria, L.

1..—Flower with five stamens.

2.—Pistil.

8.—Flower with seven stamens.

a, five outer anthers; a’, inner anthers; a*, rudimentary filament;
ov, ovary ; st, stigma; mn, nectary.

P. fagopyrum, the five outer anthers shed their pollen inwards and
the three others outwards, self-fertilisation takes place regularly
in all flowers with more than five stamens, since the anthers
dehisce so widely as to be covered with pollen all round. Whether
flowers with only five stamens fertilise themselves in absence of
insects I cannot say from direct observation; but they probably
do so, as almost all the flowers of P. Persicaria develop seed, in
spite of the scanty insect-visits. The flowers, as I have often
seen, remain expanded even in rain, and self-fertilisation in flowers
with five stamens can only take place at the end of the flowering
period, when the perianth closes up and brings stigmas and
stamens into contact.

The small size of the flower causes every insect that inserts
its head to touch one or two stamens and a stigma. If the insect
thrusts its proboscis once into each flower, cross-fertilisation. must

LL

514 THE FERTILISATION OF FLOWERS, [PART III.

generally be effected, but if it dces so more than once self-fertilisa-
tion is just as likely to take place.

A. Diptera—Syrphide : (1) Eristalis a L., freq. ; (2) E. sepulcralis,
L., comparatively ab. ; (3) E. arbustorum, L. ; (4) Syritta pipiens, L., the
most ab. visitor; (5) eee podagrica, F., almost as ab.; (6) Melithreptus
scriptus, L.; (7) M. teniatus, Mgn. ; all s., the species of Eristalis and Meli-
threptus also eating pollen. B. Hymenoptera—Apide@ : (8) Andrena dorsata,
K. 2; (9) Halictus albipes, F. 2; (10) Prosopis armillata, Nyl. ¢; all three
scarce, 8. C, Lepidoptera—(1 1) Pieris rapee, L., one specimen inserted its
proboscis but flew away again at once.

372. POLYGONUM LAPATHIFOLIUM, L., has usually five stamens,
of which one or more are generally bent inwards and come in
contact with the stigmas.

Visitors: Diptera—Syrphide: (1) Eristalis sepulcralis, L., s. ; (2) Syritta
pipiens, L., s. ; (8) Ascia podagrica, F., s.

373. PoLYGONUM MINUS, Huds.—The flowers of this species
are about as large as those of P. Persicaria, but form much looser
spikes, and are therefore less conspicuous and less visited by
insects.

Fic. 175.—Polygonwm minus, Huds.

1.—Flower, viewed obliquely from above. f
2.—Ditto, in side view, after removal of the two anterior segments of the perianth.

On a patch of P. minus and P. Persicaria in hot sunshine
(August 16, 1871) I saw six different species of flies and two of bees
visit P. Persicaria, while only two species of flies visited P. minus.

As the prospect of insect-visits is smaller, those stamens which
stand opposite to the perianth segments and which curve inwards
persist more frequently ; ; so that flowers with only five stamens
are rarer in P. minus than in P. Persicaria, and the flowers have
generally six to eight stamens around a trifid style. Otherwise
the flowers agree with those of P. Persicaria.

Diptera—Syrphide: (1) Ascia podagrica, F., s.; (2) Syritta pipiens,
L., s.; (3) Melithreptus pictus, Mgn., and (4) M. menthastri, L., s, and f.p,

PART III. | THE MECHANISMS OF FLOWERS. 515

374, POLYGONUM AVICULARE, L.—The tiny flowers, scarcely
2} mm, in diameter, are solitary, and therefore very inconspicuous ;
they are odourless and show no honey, and are very rarely visited
by insects. They always fertilise themselves, and every flower
produces seed. .

The number and arrangement of the floral organs is as in P.
Jagopyrum. ‘The five segments of the perianth, which have the
function of a corolla in P. fagopyrum, serve chiefly as a calyx (ie.
a protective covering for the reproductive organs) in P. aviculare ;
their lower parts are green, and only their extremities, which are
white or red, play the part of a corolla in rendering the flower
conspicuous. ‘The five stamens alternating with the parts of the
perianth, which bend outwards, and the other three which curve in
to the centre till their anthers stand immediately over the three

Fic. 176.—Polygonum aviculare, 1.

1.—Flower, from above. I

2.—Ditto, in side-view, after removal of the two anterior parts of the perianth and of half the
stamens.

a, the five outer, a’, the three inner anthers ; ov, ovary; st, stigma,

stigmas, have fleshy thickenings at their bases; but I have never
succeeded in finding drops of honey. If the flower really secretes
no honey, it can only have attractions for pollen-eating flies and
pollen-collecting bees. In any case, from the simultaneous
development of the male and female organs, and from the situ-
ation of the three inner anthers over the stigmas, an insect-visitor
must lead to self-fertilisation as easily as to cross-fertilisation. I
had often watched this plant in vain, but at length on a very hot
sunny day in August, 1871, I saw several insects visit it. They
were several specimens of three small Syrphide, viz. Ascia poda-
grica, F., Syritta pipiens, L., and Melithreptus menthastri, L. I
came to the conclusion, by close observation, that Syritta pipiens
was not only feeding on pollen, but was thrusting its proboscis
into the base of the flower, as if to suck honey; it was therefore
either sucking in vain, or licking a very thin layer of honey.

LL 2

516 THE FERTILISATION OF FLOWERS. [PART III.

REVIEW OF THE SPECIES OF POLYGONUM.

The species of Polygonum, like those of Geranium, show clearly
how with conspicuousness and abundance of honey the number
and variety of visitors increase, and how, as the likelihood of cross-
fertilisation is thus increased, the possibility of self-fertilisation
becomes less important; the converse is also clear. But they
show at the same time that the abundance of a plant is in no
way determined alone by the certainty of cross-fertilisation.

P. fagopyrum and P. Bistorta have the most conspicuous
flowers, the most abundant honey, and the most numerous visitors ;
in both, cross-fertilisation is insured and self-fertilisation rendered
difficult or impossible-—in the former species by dimorphism, in
the latter by well-marked proterandrous dichogamy. P. Persicaria
and P. lapathifoliwum have much smaller flowers and scantier
honey ; but, by union of their flowers in a spike, they become fairly
conspicuous and attract fairly numerous visitors; both waver
between insuring cross-fertilisation and insuring self-fertilisation,
and seem to make use, toa great extent, of both processes. In
P. minus the flowers are about as large and rich in honey as those
of P. Persicaria, but are united in much looser, thinner spikes;
they are therefore less conspicuous, less visited by insects, and
more subject to self-fertilisation. Finally, in P. aviculare, whose
flowers are not only much smaller, but are solitary and devoid or
almost devoid of honey, insect-visits and consequent cross-fertilisa-
tion are only the exception ; yet this species is with us the most
abundant of its genus, and one of the commonest of our native
plants.

The species of Rumex are anemophilous, and Axell figures the
flowers of Rumex crispus to compare them with the entomophi-
lous flowers of Rhewm Rhaponticum ; I have however found a bee,
Halictus cylindricus, F. 2, busily engaged upon the anthers of
Rumex obtusifolius, L.; and in the Alps I have often seen red butter-
flies seated on Rumex when in seed and like them in colour (590,
II. ; 609).

Orv. CYTINACEZ.

Brugmansia Zippelii, Blume, is fertilised, in Delpino’s opinion,
by carrion-flies which are detained for a time in the flowers (178).

PART III. | THE MECHANISMS OF FLOWERS. 517

Darwin supposes that the flowers of Brugmansia are visited
legitimately by long-billed humming-birds, but that short-billed
humming-birds bore through the corolla and steal the honey (164).

Rafflesia Arnoldi, R. Br., Horsfieldi, R. Br., and Patma, Bl., are
probably fertilised by carrion-flies (178).

Orv. ARISTOLOCHIAC EL.

Asarum europeum, L., and A. canadense, L., are proterogynous
with short-lived stigmas. In the first stage the stigma is mature,
and the twelve anthers are still at the base of the flower. In the
second stage the stamens grow up, arch over the stigma, and
dehisce outwards. The fertilisers, in Delpino’s opinion, are small
flies (177).

Asarum may be looked upon as an incomplete stage in the
development of the prison of Aristolochia (589).

Heterotropa asaroides, Mor. and Dene.—The flowers are interme-
diate in structure and in the mechanism of pollination between
Asarum and Aristolochia. According to Delpino, the involute
edge of the ventricose corolla forms a temporary prison for the
insect-visitors, which are probably flies (178, 360).

375. ARISTOLOCHIA CLEMATITIS, L.—The remarkable structure
of this flower, which was long the only example known of a tem-
porary prison for insects, was so far unravelled by Sprengel’s acute
and patient observations, that Hildebrand’s investigations have
brought nothing new to light, except the fact of proterogyny and
consequent cross-fertilisation (349).

The erect tube of the corolla is in the first stage lined with
reflexed hairs, which permit small midges to creep down into the
~ lower wider part which affords them shelter, but prevents them from
creeping up again. In this cage the insect-visitors find the stig-
mas mature, and fertilise them with pollen brought from flowers
visited before, the anthers meanwhile remaining closed. On the
withering of the stigmas, the anthers open; the tube of the flower
bends downwards; the hairs wither and release the prisoners,
laden with pollen, to fertilise other flowers which are still in their
first (female) stage.

Among numerous small species of gnats which I took in
hundreds from the flowers of Aristolochia Clematitis, Herr Win-
nertz identified the following :

(a) Chironomide : (1) Ceratopogon sp. ; (2) Chironomus sp. ; (0) Bibionide :

3) Scatopse soluta, Loew.

518 THE FERTILISATION OF FLOWERS. [PART III.

376. ARIsTOLOCHIA SrpHo, L. (178, 349, 360).-—In this species
the corolla maintains the same position during the whole period of
flowering. Its lower part is directed straight downwards, and then
with a sudden bend turns directly upwards; it is moderately wide,
and the mouth is provided with a three-lobed lip. In this species,
as in the previous one, we find flies imprisoned during the first
stage, while the stigmas alone are ripe; they fertilise the stigmas
with pollen brought from other flowers, and remain caged until
the stigmas wither and the anthers shed their pollen.

The reason why they stay imprisoned so long seems to me still
insufficiently explained. In Delpino’s opinion, to which Hilde-
brand assents, the smooth sides of the tube prevent the flies
creeping up, until the withering of the flowers affords them foot-
hold. This explanation. can only be correct if that part of the
tube which slopes downwards from the entrance is distinctly
smoother than the other portion which leads up from the lowest
part of the tube to the expanded terminal chamber; for if both
are equally smooth the flies will have as much difficulty in
climbing up into the stigmatic chamber as in climbing back out
of the flower. In Arum I have repeatedly noticed that the small
midges try to escape from their prison, not by creeping, but by
flying towards the light, and get knocked down by the grating at
the mouth of the flower. So if in Aristolochia Sipho the inside
of the tube is all so smooth that flies can climb neither one way
or the other from the lowest part, the reason of their imprisonment
must be sought only in the curvature of the two ends of the tube,
the one rising straight from the lowest part to the cage, while the
other part which rises up towards the entrance of the flower is so
bent outwards at its upper end that the insects flying towards the
light knock against the bend and fall back again. They are set
free by the shrivelling up of the corolla, which enables them to
creep out.

Delpino found in the cage: (a) Muscidw : (1) Lonchea tarsata, Fallen ;
(b) Phoride: (2) Phora pumila, Mgn. I found: Muscide: (1) Sapromyza
apicalis, Loew, very ab. ; (2) Myodina fibrans, L., scarce ; also a small black |
gnat, very ab., which I was unable to identify.

Aristolochia altissima, Dsf., A. rotunda, L., and A. pallida, W.,
show only slight variations from A. Clematitis, according to Delpino
(178).

A. Bonplandi, Ten., unites the form of corolla of A. Sipho with
the transitory hairs of 4, Clematitis (360).

q
}
-

PART II. | THE MECHANISMS OF FLOWERS. 519

From the dark-red colour and putrid smell of A. grandiflora,
Sw., in Jamaica, Delpino conjectured that it was visited by carrion-
flies ; and also that the tendril which passes from the upper margin
of a flower to curl round a neighbouring twig held the flower, even
during the visits of heavier insects, in the position which it must
occupy to act as a temporary prison (178, 360). ,

Orv. PROTEACEZ.

The Proteacez are proterandrous according to Delpino. On
a superficial examination they seem to fertilise themselves, for the
anthers open in the bud and shed their pollen on the knobbed
style. Even Treviranus fell into this error. But the stigmas
themselves only come to maturity much later, when probably the
pollen has been mostly carried away. According to Delpino
honey-sucking birds are the visitors for several species (178, 360).
See also Bentham’s very interesting essay “On the Styles of
Australian Proteacez ” (85).

Orv. THYMELAACE Z&.

Daphne Mezxereum, L.—The corolla-tube is 6 mm. long, and 2
mm. wide at the mouth. The flower is fitted for a miscellaneous
lot of bees, long-tongued flies, and butterflies, by which it is found
to be visited (Apide : Apis, Anthophora, Osmia, Halictus ; Diptera,
Syrphide : Hristalis ; Lepidoptera: Vanessa wrticw). ‘The proboscis
of such insects in entering the tube first rubs against the anthers
(which form two whorls of four each in the upper part of the tube)
without getting dusted by their pollen, which is only very slightly
sticky ; it then comes in contact at a lower level with the stigma,
before reaching the honey, which is secreted by the base of the
ovary and fills the lower part of the tube. The insect’s proboscis
only gets dusted with pollen as it is being drawn out of the flower.
In absence of insects pollen falls of itself upon the stigma.

Daphne striata, Tratinnick.—This plant is a striking feature in
the higher Alps, with its hemispherical, close-set trusses of white
or red strong-scented flowers. By these characters, and by the
narrow mouth of its corolla (whose tube is 10 mm. long, and whose
mouth is only 1 mm. wide), it is specially adapted for Lepidoptera,
which visit it in great numbers (578, vol. xi.; 589, 590, II. ; 609).
The flowers emit their scent chiefly in the evening, and are visited
especially by Sphingide and moths.

Leucosmia is dimorphic (167, 351).

520 THE FERTILISATION OF FLOWERS. [PART Ill.

Orv. HLHAGNE LL.

Lleagnus angustifolia, L., is visited by Apis mellifica, L. %,
and Syritta pipiens (Syrphidz) (590, IL).

Orv. SANTALACEH.

Thesium alpinum, L., is homogamous (609, fig. 154).
Thesium pratense, Ehrh., is visited by the hive-bee (590, IL.).:

Orv. HUPHORBIACEL.

The regular branching and the order of succession of the
flowers in Luphorbia helioscopia has been thoroughly described by
Delpino. He states that Euphorbiacez are fertilised by Diptera
(178, 360).

This, however, is not altogether correct. Very many short-
lipped insects (flies, beetles, Hymenoptera) resort to the freely
exposed honey and aid in the work of cross-fertilisation. Where
Euphorbia is growing in abundance even bees resort to it. I
have found upon £#. Cyparissias in Low Germany :—Diptera, 4;
Coleoptera, 8; Hemiptera, 3; Hymenoptera, 10 (Apide, 4) ; Lepi-
doptera, 1 (590, 11.). On the same plant I have found on the
Alps :—21 flies; 1 beetle; 4 Hymenoptera, of which none were
bees; and 3 Lepidoptera (609).

Euphorbia (Poinsettia) pulcherrima has scarlet bracts, and a
large nectary in each (726).

A Brazilian species of Dalechampia, according to-Fritz Miiller,
attracts the insects which cross-fertilise it by means of a colourless
resin secreted in special glands. This is collected by the insects
(bees), and used in nest-building (597).

Orv. URTICACE 2.

Tribe Urticec.

The plants of this tribe are anemophilous ; the stamens explode
when the flower opens, scattering the pollen (178).

Parietaria has proterogynous flowers (351).

1 Lists of visitors to the following Euphorbiacee are given in No. 590, II. :—

Euphorbia Esula, L., E. Gerardiana, Jacq., Z. peplus, L., £. helioscopia, L., Buus
sempervirens, Li.

PART III. | THE MECHANISMS OF FLOWERS. 521

Urtica wrens, L., owes it great abundance to the early period of
the year at which it flowers, its regular cross-fertilisation, and the
quick ripening of its fruit (590, 597).

Tribe Artocarpee.

377. Ficus Carica, L.—The latest researches confirm the fact,
which Linneus (416A) was aware of, that the so-called Caprificus,
which bears inedible fruit, and the fig-tree, cultivated for the sake
of its fruit from time immemorial, stand in the relation of male and
female to one another. Fertilisation is effected by a wasp, Blasto-
phaga grossorum, Grav. (Cynips Psenes, L., Chalcidide). The hollow
inflorescence which we call a fig is very markedly proterogynous
in both the fig-tree and the Caprificus. The greater part of its
inner wall is covered with female flowers, which are mature when
the “eye” (ostiolwm) of the young fig opens. Male flowers line
a limited zone near the orifice, and are not mature until the fig
is ripe. The Caprificus produces three crops of figs annually, one
crop beginning to flower as the previous one is ripe. Many
varieties of the fig-tree ripen two crops, some three, annually,
In most cases each crop of figs, whether of the fig-tree or the
Caprificus, brings only flowers of one sex to full maturity.

At Naples, the Caprificus ripens its three crops of inedible figs
in April, June, and August. The first crop are called mamme,
the second profichi, and the third mammoni. Each of these hatches
a new generation of fig-wasps, but it is only the second which
produces the pollen with which the fig-tree is cross-fertilised. Each
crop produces female flowers in which the wasps undergo their
development, but male flowers are usually quite wanting in the
mamme, few in number in the mammoni, and only plentiful in the
proficit. The fig-tree also produces three crops in the season,
called fiort di fico, pedagnuolt, and cimarwolt.

The reproduction of the fig-wasp takes place in the following
way. The female wasps force their way with the loss of their
wings into young figs of the Caprificus, through the narrow
ostiolum. They lay their eggs in the ovaries of the female flowers,
between the nucleus and the integuments, placing one egg only
in each. The wasp dies within the fig to which it has intrusted
its offspring. In consequence of the puncture which the wasp has
made, the female flower enlarges after the manner of a gall, and
in its ovary instead of its own embryo, the wasp-embryo develops.
While the figs themselves are proterogynous, the wasps on the
other hand are proterandrous. The wingless males are the first to

522 THE FERTILISATION OF FLOWERS. [parr ut.

emerge ; they gnaw their way into the ovaries in which the females
lie, and impregnate them, and afterwards perish within the same
fig in which they were born. The winged females then escape
by widening the passage made by the males. They leave the ripe
fig by way of the ostiolum, and enter a young fig either of the
same Caprificus or of a neighbouring fig-tree, to lay their eggs in

its female flowers. 'The wasps which enter the young Caprificus-

figs (either passing from mamime to profichi, or from profichi to
mammont, or from manmont to mamme) produce a new progeny ;
those on the other hand which enter young figs upon a fig-tree
(passing from mamme to fiori di fico, or from profichi to pedagnuoli,
or from mammoni to cimaruoli) leave no offspring, since in the
cultivated figs the female flowers are so constituted that the
wasps are not able to lay their eggs in the right spot.

Of the three generations of wasps only those which have
developed within profichi act as fertilising-agents. In the profichi,
at the time when the wasps escape from the ovaries, the zone
of male flowers near the ostiolum is covered with pollen; so the
wasps leave these figs laden with pollen. They carry this pollen
partly to the stigmas of young mammoni of Caprificus, which,
however, rarely set a seed capable of germinating, and partly to
the pedagnuoli of the fig-tree, which after this cross-fertilisation
bear good seed plentifully.

While the fruit of the Caprificus, whose only use is to supply
pollen, remains hard and withers on the tree or falls off without
becoming sweet, the fruit of the fig-tree, when the seeds ripen,
becomes sweet and juicy, and so attracts birds which disseminate
the seeds.

From the most ancient times, as long as the fig-tree has been
cultivated, its artificial fertilisation by means of the Caprificus,
or so-called Caprification, has been practised. This process consists
in hanging ripe fruit of the Caprificus (proficht) to the branches of
fig-trees, whose figs (pedagnuolt) are then in their female stage,
with open ostiola. The wasps, issuing from the former, enter the
latter, bringing the pollen of the projfichi with them.!

Sycomorus antiquorum, Miq.—The Egyptian Sycamore has for
its fertilising agent a small wasp, Sycophaga sycomori, Hasselquist,
which is closely related to the fig-wasp, and has a similar mode
of life. The females do not leave the ripe fruit through the
ostiolum, but through several holes which they make near it.

? See Bibliographical Index for a list of papers relating to Caprification,

ow

————<—

parr ut] THE MECHANISMS OF FLOWERS. — 523

Both females and males are wingless, and the males are dis-
tinguished by having a pair of long appendages at the side of the
abdomen, which are attached to the stigmata, and probably protect
them from the brown sticky pulp within the fruit (460).

Paul Mayer has investigated the wasps of numerous other old-
world species of figs, mostly from herbarium specimens. In some
species of Ficus and Sycomorus he has found Blastophaga and
Sycophaga together, but the whole number of species of wasps
was very small. On the other hand, the Brazilian figs, of which
Fritz Miiller examined ten species in his own neighbourhood
(Blumenau, province of St. Catharina), possess an astonishing
variety of wasps belonging to the same family of the Agaonide ;
some of these belong to the genus Blastophaga, some to a genus
like Jchneumon. Many are adorned with metallic colours, which
fact suggests a longer stay in the open air. In point of fact, most
of the figs which Fritz Miller studied, flower only once a year,
so that many of these wasps must, in order to lay their eggs, seek
another tree of the same species which is just beginning to flower
at the time when the figs are ripe upon the tree where they them-
selves were developed, In the case of many species of these wasps,
at least four migrations are necessary in the course of the year.

In these figs, the old inflorescence from which the wasps issue
bears only male flowers, and the young inflorescence which they
enter bears only female flowers. Self-fertilisation is thus rendered
impossible, and separate individuals are regularly crossed. The
fruit becomes sweet and in many cases gaily coloured when the
seeds ripen, and parrots which feed on it help to disseminate
the seeds (460).

Orv. JUGLANDACE &.

Juglans cinerea, L., in the United States is moneecious, and, like
J. regia, L., in Europe, is sometimes proterandrous and sometimes
proterogynous (Darwin, 167, 2nd ed.).

Orv. CUPULIFERZ.

The plants of this order also are anemophilous, but not quite
excluded from insect-visits, On February 29, 1868, in fine
weather, I saw numerous honey-bees busy collecting pollen on the
male catkins of the hazel, but none settled on the female catkins.
In many places proterandrous and proterogynous plants of the
hazel (Corylus Avellana, L.) occur. together.

524 THE FERTILISATION OF FLOWERS. [PART IIT.

Orv. SALICINEZ.

378 a. SALIX CINEREA, L.; 3780. S. cApREA, L.; 378c. S.
AuRITA, L., etc.—In spite of the simplicity of their flowers, which
differ little from the anemophilous flowers of the poplar, willows
possess special modifications which bring them greater variety of
insect-visitors in the first sunny days of spring, and insure them
abundant cross-fertilisation. These are: 1, the union of many
flowers on one inflorescence, which is not only more conspicuous,
but more easily and quickly sucked than so many single flowers ; as
in all other diclinous entomophilous plants, the male flowers are
more conspicuous than the female ones, owing in this case to the
bright yellow colour of the anthers; 2, the development of the
flowers in many Salices before the leaves, which renders the flowers
conspicuous among the bare twigs in spite of their want of coloured
envelopes ; 3, the large store of honey and pollen; and 4, above all,
the early period of flowering, which leads many bees, especially
many species of Andrena, to resort almost exclusively to willows in
search of food for their young. These characters, of which the
only one probably that has been developed in direct reference to
insect-visits is the secretion of honey, have so far insured cross-
fertilisation that the plants can well afford to dispense with the
power of self-fertilisation. Most diclinic entomophilous flowers
(Asparagus, Ribes nigrum, Lychnis vespertina, etc.) seem to have
become diclinic by degeneration of their formerly hermaphrodite
flowers, but Salix seems to inherit its diclinic condition from the
oldest phanerogams, which were diclinic and anemophilous.

Visitors: A. Hymenoptera—(a) Apide: (1) Apis mellifica, L. $,s. and
c.p., very ab. ; (2) Bombus fragrans (Pall.), K. 2; (3) B. hortorum, L. 9; (4)
B. lapidarius, L. 9; (5) B. pratorum, L. 9; (6) B. Scrimshiranus, K. 9; (7)
B. terrestris, L. 9, Nos. 2—7 s.; (8) Osmia rufa, L. ¢, s.; (9) Nomada
succincta, Pz. 9 ¢, very ab. ; (10) N. lineola, Pz. ¢; (11) N. varia, Pz. ¢,
ab. ; (12) N. Lathburiana, K. 9 ¢, ab. ; (13) N. ruficornis, L. 9 ¢, very ab. ;
(14) N. signata, Jur. ; all the species of Nomadas. ; (15) Colletes cunicularia, L,
? d, cp. and s., in hundreds ; (16) Andrena albicans, K. ? ¢, very ab. ; (17)
A. albicrus, K. 9 g; (18) A. apicata, Sm. 9 ; (19) A. argentata, Sm. (= gracilis,
Schenck) ?, scarce, ab. ; (20) A. atriceps, K. (= tibialis, K.) 9 ¢; (21) A.
chrysosceles, K. ¢; (22) A. cineraria, L. 9 ¢, ab. ; (23) A. Collinsonana, K.
?; (24) A. connectens, K. 9, scarce ; (25) A. dorsata, K. 9 ¢, ab. ; (26) A.
eximia, Sm. ¢; (27) A. Flesse, Pz. 9, rare ; (28) A. fulvicrus, K. ? g, ab. ;
(29) A. Gwynana, K. 9 g, ab.; (80) A. helvola, L. 9 ¢; (31) A. nana, K.
2 d; (32) A. nigroenea, K. 9 ¢; (83) A. nitida, Fourc. ¢; (34) A. parvula,
K. ¢; (85) A. pilipes, F. ¢; (36) A. pratensis, Nyl. (= ovina, Kl.) ? g, ab. ;

PART III. | THE MECHANISMS OF FLOWERS. 525

(37) A. punctulata, Schenk, ? g ; (38) A. rose, Pz. 2 ; (39) A. Schrankella, Nyl.
9; (40) A. Smithella, K., g, very ab., 2, scarcer; (41) A. Trimmerana, K.
2; (42)'A. varians, Rossi, 9 ; (43) A. ventralis, Imh., ¢, very ab., 2 scarce ; the
& of all the Andrenx s., the 2 s. and c.p. ; (44) Halictus cylindricus, F. 9;
(45) H. albipes, F. 9, both s. ; (46) Sphecodes gibbus, L. ?, and its varieties,
s.; (b) Vespide: (47) Vespa germanica, L. 9, s.; (48) Odynerus parietum,
L. 9, 8.3 (c) Ichneumonidae: (49) Various sp. ; (d) Pteromalide : (50) Peri-
lampus sp., freq. ; (¢) Tenthredinide: (51) Dolerus madidus, K1., s. ; (52) D.
eglanteriz, F., s.; (53) D. gonager, KL, s. ; (54) Nematusrufescens, H.,s. B.
Diptera—(a) Empide : (55) Rhamphomyia sulcata, Fallen, s. ; (56) Empis
sp., ab., s.; (b) Bombylide: (57) Bombylius major, L., s.; (c) Syrphide:
(58) Eristalis tenax, L.; (59) E. arbustorum, L. ; (60) E. intricarius, L. ; (61)

Fic. 177.—Salix herbacea, L.

A.—Part of a male plant (nat. size).
B.—Male catkin, with five flowers.
C.—Male flower, after removal of the bract, seen from without.
D.—Male flower, from within.
E.—Female catkin. with six flowers.
F.—Single female flower, from within.
.—Ditto, after removal of the bract, seen obliquely from without, so that the
large nectary (n) is visible. m’, small nectary.
(B—G, x 7; Albula, 21, 22, July, 1878).

Q

E. pertinax, Scop. ; (62) Brachypalpus valgus, Pz. ; (63) Syrpbus pyrastri, L. ;
(64) S. ribesii, L. ; (65) S. balteatus, Deg. ; (66) Cheilosia chloris, Mgn. ; (67)
Ch. brachysoma, Egg. ; (68) Ch. modesta, Egg. ; (69) Ch. pictipennis, Egg. ;
(70) Ch. preecox, Zett. ; (71) Syritta pipiens, L.; all these Syrphide both s.
and f.p.: (d) Muscide : (72) Pollenia rudis, F., fp. ; (78) Calliphora erythro-
cephala, Mgn., s.; (74) Scatophaga stercoraria, L. ; (75) Sc. merdaria, L.,
both ab., s.; (e) Conopide: (76) Sicus ferrugineus, L. ; (77) Myopa buccata,
L. ; (78) M. testacea, L., all three rather freq., s.; (/) Bibionide: (79) Bibio
Marci, L. ; (80) B. Johannis, L., both species s. C. Coleoptera—(a) Niti-
dulide : (81) Meligethes, ab., lh. ; (5) Elateride: (82) Limonius parvulus,
Pz. D. Lepidoptera—(a) Rhopalocera : (83) Vanessa urtice, L., ab., s. ; (84)
Lyceena argiolus, L., s. ; (0) Microlepidoptera: (85) Adela sp., ab. E. Hemi-
ptera—(86) Anthocoris sp.,s. See also No. 590, 11.

7

526 THE FERTILISATION OF FLOWERS. [PART IIT.

379. SALIX REPENS, L.—On the much less conspicuous flowers
of this small species, 1 found only—

A. Hymenoptera—(a) Apide: (1) Apis mellifica, L. $, s.,ab.; (2) Bombus
terrestris, L. 9, ¢.p.; (3) Andrena ventralis, Imh., 9, c.p., 48 .; (4) A. pra-
tensis, Nyl. 9, cp. ; (5) A. albicans, K. 2, ep. ; 6) A. Gwynana, K. 9,c¢.p.;
(b) Tenthredinide: (7) Dolerus eglanterie, F.,s. B. Diptera—(8) Bombylius
major, L., s.; (9) Myopa buccata, L., 8 C. Lepidoptera—(10) Vanessa
Io, L., s.

Salix herbacea, L.—Even this, the smallest of our Salices, which
straggles over the bare rock of the highest Alps, attracts sufficient
insect-visits to be able to dispense with the possibility of spontaneous
self-fertilisation ; the latter is rendered impossible by the dicecism
of the flowers. This fact is strikingly opposed to the common
statement that on the Alps (owing to the great scarcity of insects)
only those plants which possess the largest and brightest flowers
succeed in being fertilised by the aid of insects. The flowers are
inconspicuous, but the honey is very abundant. The only visitors
that I have found on the flowers of S. herbacea are a small moth
(Tineide) and a fly (Cenosia sp.), both sucking honey (609).*

Orv. HUMPETRACEZ.

Empetrum nigrum, L., is anemophilous (762).

Gymnospermee.

These lowest and oldest Phanerogams have diclinic anemo-
philous flowers ; the female flowers are devoid of a stigma, and possess
a cavity in the ovule between the micropyle and the nucleus. In
the flowering period, a drop of fluid rests upon the micropyle ; the
pollen-grains brought by the wind are caught by it, and are drawn
within the micropyle as the fluid evaporates or is absorbed (178 I. ;
712).

Delpino has given a fuller account of the process of pollination in
Pinus pinaster, Ait., and P. halepensis, Ait., (178) and in Larix (177).

Monocotyledons.
Orv. HYDROCHARIDEZ.

Vallisneria spiralis, L.—The male flowers are set free from the
plant and float on the surface of the water. The pollen, which had

1 Insect-visitors of Salix fragilis, L., and S. amygdalina, L., are enumerated in
No. 590, 1. ; and those of 8. reticulata, L., and S. retusa, L., in No. 609.

PART III. | THE MECHANISMS OF FLOWERS. 527

hitherto been protected from contact with the water, is now carried
by currents to the stigmas of female flowers. Va/llisneria is, in a
certain sense, a transition from the water-fertilised to the insect-
fertilised flowers ; Hydrocharis is distinctly entomophilous (178, I1.).

Orv. ORCHIDEL.

This family is remarkable for the following characters, due to
its wide distribution and to its enormous number of species: first,
for great variety of habit and diversity of station; secondly, for its
immense variety of peculiar and highly-specialised flowers; and
thirdly, for the unusually large number of seeds produced in each
capsule. The diversity of habit and place of growth must be ex-
plained by supposing all the parts of the plant concerned in nutri-
tion to have been very variable. I have discussed at full length
their variability in our recent species, in a paper upon the genetic
relations of Hpipactis viridifolia, EB. microphylla, and £. latifolia
(565).

The multiplicity of forms of flowers is not difficult to under-
stand if we only suppose the ancestors of the family to have been
as liable to variation in their flowers as our recent species are. Dr.
Rossbach has discussed the variability of the flower in Orchis fusca,
and I myself in the genus Habenaria.?

I do not doubt that Orchids owe their extraordinarily perfect

, adaptations to particular insects not only to the tendency of the

parts of their flowers to variation, but also to the separation in
time of the two stages in the act of impregnation. At the time
of flowering the ovule is, as a rule, not yet developed; pollen is
applied to the stigma, and the pollen-tubes grow out, but the ovule
is only developed and impregnated weeks or months, sometimes six
months, later. The extremely complete adaptations to cross-fertil-
isation have in their turn resulted, in many cases, in the flowers
becoming absolutely sterile to their own pollen.

In regard to capacity for fertilisation by their own pollen,
Orchids show the greatest possible differences, all of which, however,
are linked together by intermediate conditions. We find in this
order, cleistogamic flowers* and open flowers; flowers regularly 4

1 Verhdl. des naturh. Vereins fur pr. Rheinl. und Westfal. p. 166, 1857.

2 Tbid., pp. 36-47, 1868.

3 Schomburgkia, Cattleya, and Epidendrwm (Criger, 149) ; Dendrobiwm (Ander-
son, 5); Zhelymitra (Darwin, 167). ;

4 Ophrys apifera (Darwin, 155); Neotinea intacta (Darwin, 159) ; Gymnadenia
tridentata and Platanthera hyperborea (Asa Gray, 274); Epipactis viridifolia (H.
Miiller, 565) ; Epidendrwm (Fritz Miiller, 553).

528 THE FERTILISATION OF FLOWERS. [PART TI.

or occasionally! self-fertilised ; others never self-fertilised, though
quite fertile to their own pollen if it be applied artificially (565) ;
flowers absolutely sterile to their own pollen, though fertile not
only to the pollen of their own species but even to that of other
species of their own genus (158A, 693); finally species in which
pollinia and stigma of the same individual act as fatal poisons to
one another.”

In regard to the immense number of seeds sometimes produced,
it may suffice to record an observation of my brother’s, who
estimated over 1,750,000 seeds in a single capsule of a Mazillaria
(159).

Dissemination by wind is favoured by the lightness of the seeds
and by the peculiar dehiscence of the capsule, which opens by
three longitudinal slits, the parts remaining connected above or
below.

The subject of the cross- and self-fertilisation of Orchids has
been so fully treated in Darwin’s classical book and elsewhere that
I may confine myself to notes on those of our native species whose
visitors have been actually observed, and to some recent additions
to our knowledge.

Tribes Lpidendree ? and Vandee.

Angrecum sesquipedale, Pet. Th.—This plant is a native of
Madagascar. The spur is longer than that of any other Orchid,
perhaps than that of any other plant, and according to Darwin
(155A, p. 198) an insect must have a tongue 10 or 11 inches long
to reach the honey. Mr. W. A. Forbes has given evidence of the
existence of such an insect (256). My brother caught a hawkmoth
(Macrosilia Cluentius) in Brazil which actually had a proboscis 10
or 11 inches long. I have figured this proboscis in No. 571.

In Notylia, some species of Oncidiwm, and others, honey is
secreted by the outer surface of the ovary and by the bracts. Ina
Cattleya it is secreted for a long period by the young fruit; this
honey is diligently sought by ants, but of course has no relation
to the process of fertilisation (Fritz Miiller).

Gomeza.—My brother observed this orchid fertilised by a bee,
and saw the fertilised flower produce its capsule.

Polystachya.—In a small Brazilian species of this genus, the

1 Neottia nidus-avis frequently, Listera ovata exceptionally (Darwin, 159).
2 Species of Oncidiwm, Notylia, Gomeza, Stigmatostalix, and Burlingtonia (Fritz
Miiller, 550; Darwin, 158A, 11. chap. xvii.)

3 See also No. 34 (Liparis Bowkeri), and No. 609, p. 77, fig. 21 (Corallorhiza
innata.

AD eI Pa ag yelp el

= «

tn i.e _

7%
“—_

“a

PART III. | THE MECHANISMS OF FLOWERS. 529

labellum becomes full of loose cells, like flour, which probably
attract insect-visitors (Fritz Miiller).

Epidendrum.—tIn South Brazil there are several plain green
species of this genus, quite without perceptible perfume, which
secrete abundant honey, and must be fertilised by insects. This is
an illustration of how flowers need not make themselves perceptible
at a distance to their visitors by means which affect our senses.

An observation of my brother’s in the island of St. Catharina
in South Brazil shows how a plant may propagate itself by self-
fertilisation when deprived of the insects for which its flowers were
adapted. On this island an Epidendrum occurs, whose flower con-
tains three perfect anthers; the two lateral anthers effect self-
fertilisation regularly, while the pollen of the third can only be
removed by insects, an event which seems to be exceedingly rare.
The flower is almost scentless, At Itajahy an Epidendrum occurs
which resembles the triandrous Epidendrum of St. Catharina almost
exactly, save that it is monandrous and has a strong, aromatic
scent. The triandrous variety can only be looked upon as descended
from specimens of the monandrous form which got transported to
St. Catharina. There the insects adapted for the flower must have
been absent or very scarce, so that the power to reproduce by self-
fertilisation became desirable. Accordingly, whenever the two
lateral stamens appeared as an abnormality (as often happens
in other Orchids) they had the greatest possible chance of being
perpetuated by Natural Selection; the perfume of the flowers, on
the other hand, being useless and therefore removed from the
influence of Natural Selection, was lost (533).

Tribe Neottiew.

Spiranthes autwmnalis, Rich., has been observed by Darwin to
be fertilised by humble-bees (155A, p. 127).

380. ListerA ovaTa, R. Br—Sprengel has described the
fertilisation of this flower as he observed it in his garden, but he
-was not acquainted with the insect-visitors. Darwin has given an
admirable description of the flower, and mentions two Hymenoptera
(Hemitiles and Cryptus) which he saw attaching the pollinia to their
foreheads ; as he caught the insects, he did not witness the placing
of the pollinia on the stigma. My own observations may help to
confirm and complete the accounts given by Sprengel and Darwin.

‘On a sunny afternoon in May, 1867, I watched the insect-visitors

M M

-~

530 THE FERTILISATION OF FLOWERS. [rarr IL.

of this plant for more than an hour. I was able to watch about
twenty plants simultaneously, and on each three or more insects
were often busy sucking honey together. I concentrated my atten-
tion in every case on a single insect, and did not catch it until it had
accomplished at least one act of fertilisation ; most of them I only
caught after they had fertilised three, four, or more flowers. The
specimen of Grammoptera levis which I have figured (4, Fig. 178)
was already laden with pollinia when I first noticed it; it visited
‘six flowers in my presence, carrying off the pollinia from four, and
applying pollen to the stigmas of the other two, which had been

Fic, 178.—Listera ovata, R. Bz.

1.—Portion of an unfertilised flower, from the side.

2.—Front view of flower, after the pollen masses (po) have been removed from the anther. The
flat rostellum (r) is bent forwards, and partly conceals the stigma (st). (Magnified one half as much
asl.) mn, nectary.

8.—Pollen-masses adhering to a needle (x 20). k, cement; po, pollen-masses.

4.—Grammoptera levis, with a number of pollen-masses on its head.

previously visited and deprived of their pollinia. To judge from
the number of hardened cement-disks which this insect carried
upon its head, it must have fertilised very many flowers before I
began to watch it. Although a great many insects flew away
before I tried to catch them, and others escaped me, I secured a
considerable number, all of which I had seen effecting cross-fertil-
isation, and all of which still bore pollinia on their heads. Except
Grammoptera levis* they were all Ichneumonide. They have been
identified for me by Dr. Kaltenbach of Aachen as follows: (1)
Ichneumon uniguttatus (one specimen); (2) Alysia (one); (3)

1 Sprengel seems to have caught this insect bearing pollinia of Zistera ovata.
At least he mentions a small beetle with black head and scutellum,and brown elytar.

PART III. | THE MECHANISMS OF FLOWERS. 531

Cryptus (eight specimens belonging to three species) ; (4) Phagedon
(two); (5) Zryphon (two); (6) Campoplex (one); (7) Microgaster
rufipes, F. (three). I saw Bombus agrorum, F., licking the honey
in several flowers without removing the pollinia.

Sprengel has correctly described how small insects (all of the
above, except Bombus) regularly alight on the lower end of the
labellum (p’, 2) and slowly creep upwards licking the honey in the
groove (v); when they have finished and raise their heads, they
come in contact without fail with the slightly prominent edge of
the thin rostellum (7, 1). On the slightest touch, this exudes
a small white drop of fluid, which reaches the apex of the pollinia
(po, 1) and hardening instantly, cements them to the object whose
touch caused the exudation ; and so in every flower which has not
previously been visited, the insect-visitor receives a new pair of
pollinia. The insect flies away startled, and soon afterwards alights
on the labellum of another flower, usually on another plant. The
rostellum, on first being touched and while it exudes its drop of
fluid, curves downwards so as partly to protect the stigma (2,
Fig. 178); but afterwards, while the groove of the labellum is
secreting a fresh supply of honey, the rostellum gradually rises,
leaving the way free to the stigma.

Thus to previous accounts of this flower we may add two
statements: 1, that when an insect has once attached pollinia
to its head, it must either acquire a new pair of pollinia or apply
-some pollen to the stigma in every flower that it visits sub-
sequently; 2, that not only does cross-fertilisation always occur,
but that the pollen of one plant is usually carried to a flower
upon another.

381. NEOTTIA NIDUS-AVIS, Rich.—The flower resembles that
of Listera ovata in regard to the function of the rostellum and its
position in relation to the anther and stigma. It differs, however,
by concealing its honey from view though leaving it easily
accessible, by cementing its pollinia to the insect-visitors in a more
irregular and less effective way, and by being frequently self-
fertilised owing to the dry pollen falling bit by bit upon the
stigma. All such insect-visitors as are attracted only by exposed
honey are absent, and the dull yellow flowers deter all those which
are only allured by bright colours.

This tendency to self-fertilisation seems to me to be due athe?
to the mechanism of the flower being as yet incomplete than to
scarcity of insect-visits.. I have only once watched this plant at

MM 2

532 THE FERTILISATION OF FLOWERS. [PART ILI.

the proper season, but on that occasion I found it visited by flies
in considerable abundance, and several of the spikes were covered
with spiders’ webs. I saw several specimens of Spilogaster cinerea,
Wied., and a small species of Muscide alight on the labellum and
suck the honey; but I did not see any of them touch the rostellum
and remove the pollinia. After watching for a long time, I saw
a larger yellow fly (Helomyza affinis, Mgn.) visit a flower; when
it crawled up the labellum to its base, licking the honey on its
way, it came in contact with the rostellum and cemented the
pollinia to the anterior part of its thorax. It flew away, startled ;
but it was caught in a spider’s web, and my chance of observing
the fertilisation of Neottia was lost.

Fig. 179.—Neottia nidus-avis, Rich.

1.—Lateral view of flower.

2.—Ditto, of labellum.

8.—Labellum, from above. The small rings indicate honey-drops.
4.— Essential organs, in side-view.

br, bract; co, column. Other letters as in Fig. 180.

Goodyera repens, R. Br—Mr. R. B. Thomson saw this plant
fertilised in the north of Scotland by Bombus pratorum (Darwin,
159, 165); I have seen it on the Alps fertilised by B. mastrucatus,
% (609).

The Alpine Chameorchis is probably adapted, like Listera, for
fertilisation by Jchnewmonide (609).

Epipactis latifolia, Swartz.—Charles Darwin observed this plant
to be fertilised by wasps (Vespa silvestris). Self-fertilisation seems
scarcely possible.

Epipactis microphylla, Ehrh., fertilises itself regularly; but
part of the pollen can be removed by insects by the aid of the
sticky secretion of the rostellum, as the whole pollinia are in
L. latifolia,

Epipactis viridiflora, Rehb., has quite lost its rostellum, Small

PART III. ] THE MECHANISMS OF FLOWERS. 533

portions of pollen may be accidentally carried away by minute
insects, but the flower is self-fertilised in a still more conspicuous
degree than #. microphylla. I have described elsewhere (565)
the changes in the relative position of anther and stigma which
render self-fertilisation possible, and the intermediate nee
between the above-mentioned species of Hpipactis.

Epipactis palustris, Crantz.—Mr. W. E. Darwin saw this species
visited and fertilised abundantly in the Isle of Wight by Apis
mellifica, % ; also by flies (Sarcophaga carnosa and Celopa frigida)
and by Crabro brevis.

Epipogon Gmelini, Rich—Paul Rohrbach! has described the
structure and fertilisation of this flower very admirably (675). :
He observed Bombus lucorwm, L., visiting the flowers.

Tribe Ophrydee.

Serapias longipetala, Pollin., is visited by bees in the west of
Liguria (Delpino, 567).

Herminium Monorchis, R. Br—George Darwin observed the
flowers visited by twenty-seven species of small insects, of which
the largest were one-twentieth of an inch long. They consisted
of Hymenoptera (especially Tetrastichus diaphanthus and
Pteromalini), Diptera, and Coleoptera (e.g. Malthodes brevicollis).
I have found the flowers visited on the Alps by small Braconidz
and Pteromalidz (609).

Platanthera—I have elsewhere (565) proved at very consider-
able length that the varieties distinguished as P. bifolia and
P. chlorantha by German botanists are connected with one another
by numerous intermediate forms; but that the plant referred to
by Darwin as P. bifolia corresponds to P. solstitialis, Bonningh.,
and is a well-defined species. The spur of P. solstitialis is from
12°to 21 mm. long, that of P. chlorantha from 23 to 43 mm.; in
both species the spur is too narrow to admit a bee’s proboscis.
The honey is therefore accessible only to Lepidoptera, and in. the
extreme forms of P. chlorantha only to Sphingidw. The colour
of the flowers suggests that they are adapted for nocturnal and .
crepuscular insects. Darwin caught a specimen of Hadena dentina
to one of whose eyes a sticky disk of P. chloran'ha was attached,
and a Plusia with one attached to the margin of its eye. The
sticky disks stand much closer together in P. solstitialis, and

1 This able and brilliant naturalist died at an early age.

534 THE FERTILISATION OF FLOWERS. [parr ut.

become attached to the base of the proboscis, as Darwin observed
in the case of Agrotis segetum and Anaitis plagiata+

Professor Asa Gray has published most interesting observations
on the structure and mode of fertilisation of certain American
species of Platanthera (273, 274, 277).

Himantoglossum hircinwm, Rich—Hildebrand saw this species
visited by a bee (361).

Gymnadenia conopsea, R. Br—The spur is so narrow that the
honey is only accessible to Lepidoptera. George Darwin observed
the flower to be visited by nocturnal Lepidoptera (Plusia chrysitis,
P. gamma, Anaitis plagiata, Triphana pronuba). On the Alps,
T have seen this species visited by twenty-seven different species
of Lepidoptera, mostly butterflies (600, fig. 13).

Gymnadenia odoratissima, Rich., has a much shorter spur
(4 or 5 mm., against 13 or 14 mm. in G. conopsea), paler colour,
and stronger and more aromatic perfume. I have only found it
visited by three species of nocturnal Lepidoptera (609, fig. 13).

Nigritella angustifolia, Rich.—The ovary is not twisted, and the
position of the parts of the flower is, therefore, the reverse of that
in Gymnadenia. Its strong odour of vanilla attracts very numerous
Lepidoptera (I observed forty-eight species), to the under side of
whose proboscis the pollinia get cemented (609, fig. 15).

Nigritella suaveolens, Koch., seems to be a hybrid between JN.
angustifolia and Gymnadenia odoratissima; but as G. odoratissima
cements its pollinia to the upper side of the insect’s proboscis, and
NV. angustifolia to the lower, it is difficult to see how this hybrid
can be produced, except from flowers of the species which are already
abnormally inclined. Such abnormally placed flowers, are, however,
to be met with now and then in both species, (609, fig. 16).

Anacamptis pyramidalis, Rich—The flower agrees in most
points with the species of Orchis to be described immediately, and
like them secretes no free honey. The spur is very narrow, only
admitting the tongues of Lepidoptera, and the mode of attachment
of the pollinia by means of a saddle-shaped band instead of two
round disks is also specially fitted for the proboscis of Lepidoptera.
Darwin observed twenty-three different species of butterflies and
moths carrying pollinia of A. pyramidalis on their tongues.

Ophrys muscifera, Huds.—This species seems to be adapted
for carrion-loving Diptera. The flies are probably attracted by
the dark purple under lip, which bears a pale blue smooth spot,

T have given an account of the flower of Platanthera bifolia, Rich., with figures,
in No. 589 and No, 609,

—

—————

PART 111. | THE MECHANISMS OF FLOWERS. 535

and under favourable conditions is covered with a number of
minute drops. A Sarcophaga which I saw seated on the under
lip, licking these drops, flew away on my approach. But it had
its head pointing towards the base of the lip, and if I had not
disturbed it, it would probably not have failed to lick also the two
black shining bodies at the base of the lip; in doing so it would
have touched the rostellum and caused a pollinium to be cemented
to its head. The two bodies at the base of the under lip look like
drops of fluid, though in reality they are quite dry. They may
be called pseudo-nectaries, and probably deceive the insect-visitors

(5 89, 599, I.).

382-385. ORCHIS MASCULA, O. MORIO, O. LATIFOLIA, and O.
MACULATA.—In all these Orchids the three sepals and the two
superior petals arch over the essential organs of the flower, while
the inferior petal or labeilum forms a convenient alighting-place
for insect-visitors. The labellum is prolonged backwards into a
hollow spur, which secretes no free honey, but whose walls are
composed of very delicate and succulent tissue. Immediately above
the entrance to this spur stands the trilobed stigma, whose two
inferior lobes form the true stigmatic surfaces, while the third
superior lobe forms the rostellum. This organ, the bursicula of
German authors, consists of a little pouch full of viscid matter,
which projects into the mouth of the spur. The two lateral
anthers are just visible as useless rudiments (staminodes); the
third, and only perfect one, stands immediately above the rostellum.
Its two loculi are separated by a broad connective, and are split
anteriorly for their whole length by a longitudinal slit. The two
pollinia lie within the loculi, quite unattached except at the ends
of their caudicles, which adhere to the upper surface of the ros-
tellum. When an insect thrusts its head into the spur, it imevit-
ably comes in contact with the rostellum ; the membrane covering
the latter instantly splits into an inferior portion, which curls
backwards, and two small round disks, connected with the caudicles
and coated abundantly with viscid matter on their lower surfaces ;
these attach themselves to the insect’s head. The cement of the
sticky disks quickly hardens, and when, after a short time, the
insect withdraws its head, it takes with it the disks and the pollinia
attached to them by their caudicles. At first the pollinia stand
almost perpendicular to the disks, but soon, as the disks dry, the
pollinia bend gradually forwards through an angle of nearly 90°,
and so come into such a position that in subsequently-visited

536 THE FERTILISATION OF FLOWERS. [PART III.

flowers, they are applied directly to the stigma. Each pollinium
consists of a great number of packets of coherent pollen-grains ;

the packets are bound together by delicate elastic filaments to -

form an oval pollen-mass. When this is pressed against the very
adhesive stigma and again withdrawn, all the packets that have
come in immediate contact with the stigmatic surface remain ad-
hering to it, for the elastic filaments break before the attachment
of the packets to the stigma gives way. By this means, an insect
flying from flower to flower effects cross-fertilisation regularly.

This view of the flower of Orchis was propounded by Darwin
before he or any one else had succeeded in observing insects en-
gaged in the work. Every detail in the structure of the flower
seemed to be satisfactorily explained, but the absence of honey in
the spur remained without explanation. Sprengel, who supposed
that the pollinia were applied by insects to the stigma of the same
flower (702, p. 401), suggested that the insect-visitor came in
search of honey, and on finding none, passed on to some other
kind of flower. But it was essential for Darwin’s theory that
each insect-visitor should visit a number of the flowers in succes-
sion; and Darwin suggested that possibly the insects pierced the
delicate tissue of the spur and sucked the included fluid. My own
direct observations have confirmed this view, as well as every
detail of the rest of Darwin’s account. The following description
of the action of insects on Orchis was published many years ago
(565) — |

On May 6, 1869, I and my son Hermann at length succeeded in
observing humble-bees fertilismg the flowers of Orchis upon
Stromberg Hill. As we lay upon the turf, which was overgrown
with Orchis mascula, we saw a humble-bee (apparently Bombus
terrestris) alight, close beside us, on the base of a spike of that
plant. It thrust its head into a flower, and drew it out after about
four seconds with the two pollinia attached to it. It repeated the
same operation on two more flowers. After withdrawing its head
from the third, it paused, and tried without success to free itself
from the pollinia, which were cemented firmly to the front of its
head. Climbing a little further up the spike it thrust its head
into a fourth flower. At that moment I tried to catch it in my
net, but it escaped and flew away. We next saw a Bombus
hortorum suck three or four flowers on a _ spike of Orchis
mascula (beginning at the base of the spike), and then proceed
to another spike, near by. We examined this latter spike, and
found several of its stigmas smeared with pollen and the loculi of

A, ha lh Ai: IO ia l=
why, ea

Py ep
ee i a a a eg eT a ee ee

ee

a

,

PART III. | THE MECHANISMS OF FLOWERS. | 537

the anthers empty. In the space of two hours we had three more
opportunities of watching the fertilisation of Orchis mascula ; the
fertilising agent on two of these occasions was Bombus lapidarius,
on the third, Psithyrus campestris. B. lapidarius spent a shorter
time on each flower (about two to three seconds), but otherwise the
various bees behaved precisely alike. We caught the Psithyrus
and a B. lapidarius, and found a number of pollinia on the head of
each. Some of the pollinia had already bent forwards, so that
they were ready to come in contact with the stigma of the next
flower; others were still erect. Of ninety-seven humble-bees
which we caught that day on Stromberg Hill, thirty-two bore
pollen-masses of Orchis. We frequently observed on our captured
bees, that when the pollen-masses bent forwards the bee was able
to tear them off with its mandibles. Some bees which we caught
with pollinia on their heads had them attached to their forelegs
when examined shortly afterwards. These frequently successful
efforts on the part of the bees to free themselves from the pol-
linia explain why we often find whole pollinia or pairs of pollinia
attached to the flowers, generally in the neighbourhood of the
stigma.

On this one day, which was especially favourable, as it was warm
and calm, and came after a long spell of cold weather, probably
more than a third of all the humble-bees on Stromberg Hill had
been engaged in fertilising Orchids. The following numbers give
a rough idea of the scale on which the work was performed. At
seven o'clock on the morning of the same day I gathered ten
specimens of Orchis morio on a meadow covered with the plant.
These ten spikes contained 107 expanded flowers; of these, one only.
had its anther-loculi empty and its stigma smeared with pollen;
two had their stigmas smeared with pollen, but their pollinia had
not been removed. At five o’clock in the afternoon I gathered in
the same place ten spikes containing ninety-seven flowers ; fourteen
had their stigmas smeared with pollen, and of these two only had
their pollinia still within the anther-loculi; three other flowers
had their pollinia removed, but their stigmas showed no trace
of pollen. Thus at seven o'clock in the morning 2°5 per cent.,
and at five o’clock in the afternoon over 14 per cent. of the flowers
had been fertilised.

I need hardly add that this observation fully confirmed Darwin’s
suggestion. The bees must have found something within the
spurs, or they would not have continued to visit the flowers. Since
the spur contains no free honey, but abundant fluid within its

~

538 THE FERTILISATION OF FLOWERS. [PART ITI.

wall, it is certain that the bees pierced the delicate inner membrane
and sucked the included fluid. They doubtless pierced the tissue
quickly and easily with the points of their maxille.

My direct observations have shown that the three or four
seconds spent by the bee on each flower is enough to permit
the cement to harden and attach the pollinia firmly to the bee’s
head; and by thrusting a pencil into the spur of O. mascula we can
see that two to three seconds is enough to fasten the pollinia
firmly. The bee always thrusts its proboscis once only into each
flower, and accordingly each flower receives pollen from another.
In O. mascula, the bending forwards of the pollinium occupies
about forty seconds; it is rarely completed in twenty-five seconds.
A bee which visits three or four flowers on a spike, spends three
to four seconds upon each, and about two seconds in passing from
from one flower to another ; so that at most it spends about twenty
to twenty-two seconds on each spike. It has therefore passed to
another spike before any of the pollinia belonging to the first have
finished bending downwards. It seems therefore that not only
is cross-fertilisation of separate flowers ensured, but even of
separate plants. |

I repeated these observations many times subsequently. I
was wrong at first in supposing that the bee only pierced the
tissue of the spur once, and I neglected to look for the punctures
that the bee made. On June 13th, 1870, a hive-bee flew before
my eyes into a flower of O. latifolia: it pierced the inner wall of
the spur several times with the points of its maxille, and then flew
away, bearing the two pollinia on its head, to a flower of Lychnis
Jlos-cuculi. I gathered the flower immediately after the bee left
it, and found the punctures visible from the outside as small,
bright, elongated specks. Darwin observed Hmpis livida piercing
the inner wall of the spur of O. maculata, and also found the
punctures that it made. The question as to what insects seek
in the flowers is now finally settled, and Delpino’s doubts (567,
p. 16) concerning the accuracy of Darwin’s views are shown to be
unfounded.

382. ORCHIS MASCULA, L. :—

Visitors : Hymenoptera—A pide : (1) Bombus hortorum, L.; (2) B. lapi-
darius, L.; (3) B, confusus, Schenck.; (4) B. terrestris, L. ; (5) B. agrorum,
F. ; (6) B. pratorum, L.; (7) B. (Psithyrus) campestris, Pz. ; (8) B. muscorum
1.7 Nos, 1—7, observed by me, No, 8 by a friend of Darwin’s (Ann. and Mag.
of Nat, Hist. Sept. 1869),

PART III, | THE MECHANISMS OF FLOWERS. 539

383. OrcHIS MoRIO, L. :—

Visitors : Hymenoptera—Apide: (1) Apis mellifica, L. $; (2) Bombus
muscorum, L. ; (3) B. lapidarius, L. ; (4) B. confusus, Schenck ; (5) B. pra-
torum, L. ; (6) B. hortorum, L. ; (7) B. silvarum, L. ; (8) Eucera longicornis,

L. ; (9) Osmia rufa, L. Nos. 1, 2,8 from Darwin ; Nos. 1, 3—7, 9 observed
by me.

384. ORCHIS LATIFOLIA, L. :—

Visitors : Hymenoptera—Apide: (1) Apis mellifica, L. $; (2) Bombus
senilis, Sm. ; (3) B. fragrans, Pall. (K.); (4) B. confusus, Schenck ; (5) B.
hortorum, L. ; (6) B. lapidarius, L. ; (7) B. terrestris, L.; (8) B. muscorum,
L. ; (9) Eucera longicornis, L. ¢; (10) Halictus leucozonius, K. 9; (11) No-
mada sexfasciata, Pz. 9; (12) Osmia fusca, Chr. (= bicolor, Schr.) 9, all
from my own observations. According to Darwin, O. latifolia is also visited
by Diptera. I have found it visited by humble-bees on the Alps (609).

385. O. MACULATA, L., seems to be visited chiefly by Diptera.

Visitors: A. Hymenoptera—-Apid@ : (1) Bombus pratorum, L. % (once).
B. Diptera—(a) Empide: (2) Empis livida, L.; (3) E. pennipes, both
oberved by George Darwin, the former abundantly, the latter more rarely ;—
in thrusting their tongues into the flower they cemented the pollinia to their
eyes. (b) Syrphide: (4) Volucella bombylans, .L., very ab.; (5) Eristalis
horticola, Mgn. (Sld.) freq. ; both got the pollinia attached to the fore-part of
their heads. Nos. 1, 4, 5 were observed by me.

Orchis maculata is visited by Cerambycide (Darwin, 165),
and also by humble-bees (509).

Orchis ustulata, L. and O, globosa, Li. are adapted for Lepidoptera
by the very narrow entrances to their spurs; the latter species I
found to be visited abundantly and exclusively by Lepidoptera
upon the Alps (609).

Orchis tridentata, Scop. is visited by humble-bees (590, 1).

Tribe Cypripedine.

386. CyPpRIPEDIUM CALCEOLUS, L.—The observations of Darwin
(153 A.), Asa Gray (276), and Delpino (172, 178, 567), all refer to
other and in some cases very different species of this genus. My
own observations on C. Calceolus were published many years ago
(565, 566), and have been repeatedly verified and extended since.

I have observed five species of Andrena fertilising the flower ;
viz. A. nigroenea, K. 9, A. fulvicrus, K. 9, A. albicans, K. 9,
A. atriceps, K. 9 (= A. tebialis, K.), and A. pratensis, Nyl. 9.
These bees, attracted by the colour and perfume of the flower, fly
into the slipper-shaped lip and lick and bite the hairs lining its

540 THE FERTILISATION OF FLOWERS. [PART III.

floor, which are sometimes covered with small drops of honey.
They try for some time to escape by climbing up the vaulted sides
of their prison towards the orifice that they entered by; at last
after creeping beneath the stigma (st, 2, Fig. 180), they manage
with a great effort to escape by one of two’small lateral openings
(ex, 2) at the base of the lip; in doing so they smear one shoulder
with a sticky pollen from the anther immediately above. In the

Fia. 180.—Cypripedium Caleceolus, L.

de —Flower, with its parts in their natural position, seen from in front and above.
2.—Ditto, in longitudinal section, after removal of the sepals and the two superior petals. (The lip
is bent slightly downwards, to show the opening ew clearly).
3.—The essential organs from below.

ov, Ovary ; 8, sepal ; Pe petal ; p’, labellum ; a, anther; a’, metamorphosed stamen ; st, stigma
#, ‘entrance ’’; ew, ** exit.’

next flower, the bee, as it creeps under the stigma, leaves some pollen
on its papille, which are long and point obliquely forwards ; then,
squeezing itself again through one of the small orifices, it acquires
another load of pollen: cross-fertilisation is thus effected regularly.
The third anther (a’) is metamorphosed into a broad, purple-spotted
lobe, which stands in the posterior half of the cavity of the lip and
leaves only the small lateral orifices described above. The hairs,
which are arranged in a broad band on the floor-of the labellum,
seem to help the Andrene to climb up towards the orifices, besides

PART IIL. | THE MECHANISMS OF FLOWERS. 541

attaching them by their secretion. Smaller bees and flies which
are too large to pass freely through the orifice and too weak to
force their sides apart, must as a rule perish of hunger within the
labellum. I have repeatedly found Andrena parvula, K. 9, dead
within the labellum, and also the following flies: Hmpis punctata,
F., a Cheilosia (Syrphide), an Anthomyia (Muscidae), and considerable
numbers of Spilogaster semicinera, Wied. (Muscidew). Small
beetles (Meligethes) are often able to creep freely out of the
labellum, but sometimes they are held fast by the sticky pollen and
remain to perish.

Cypripedium barbatum is believed by Delpino to be fertilised by
flies. Delpino found flies within the labellum of some cultivated
plants, which afterwards set seed (178, 567).

Cypripedium caudatum is believed by Delpino to be fertilised by
snails (178),

THE ADAPTIVE MODIFICATIONS OF ALPINE ORCHIDS COMPARED
WITH THOSE OF THE LOWLANDS.

A review of the Orchids that I have observed upon the Alps
shows that, above the limit of trees, almost the only species which
occur are those adapted for Lepidoptera, while in the lower regions
forms adapted for all kinds of visitors occur. The following
species occur in greater abundance above the level of trees, or are
restricted entirely to that region: (1) Orchis ustulata, (2) O. globosa,
(3) Gymnadenia conopsea, (4) G. odoratissima, (5) G. albida, (6)
Peristylus viridis, (7) Nigritella angustifolia (N. suaveolens, as being
probably a hybrid, cannot be included), (8) Platanthera solstitialis,
(9) Chameorchis alpina. Of these, six (1, 2, 3, 4, 7, 8) are un-
doubtedly, and two (5, 6) (from the narrow.entrance to the spur)
in all probability, are fertilised by Lepidoptera. While we thus
find that of the loftier Alpine Orchids at least two-thirds, but
probably eight-ninths, are adapted for Lepidoptera, in Westphalia

we find that, of thirty-five species,! at most six? are adapted for
Lepidoptera, and most of these are very sparingly visited by
them (609).

1 Orchis pyramidalis, O. morio, O. mascula, O. laxiflora, O. coriphora, O. militaris,
O. tridentata, O. sambucina, O. latifolia, O. maculata, Gymnadenia conopsea, G.
albida, Platanthera bifolia (solstitialis), P. chlorantha, Peristylus viridis, Herminium
Monorchis, Ophrys muscifera, O. apifera, O. aranifera, Epipogon Gmelini, Cephal-
anthera pallens, C. ensifolia, C. rubra, Epipactis latifolia, E. microphylla, E. viridi-
flora, E. atrorubens, E. palustris, Listera ovata, Goodyera repens, Spiranthes autum-
nalis, Malaxis paludosa, Liparis Loeselii, Cypripedium Calceolus. -

? Orchis pyramidalis, Gymnadenia conopsea, G, albida, Platanthera bifolia (solsti-
tialis), P. chlorantha, Peristylus viridis. Aw

542 THE FERTILISATION OF FLOWERS. [parr in.

Orv. SCITAMINE LZ.
Tribe Zingiberee.

Hedychium and Alpinia are adapted for cross-fertilisation by
insects. The visitors must come in contact first with the stigma
and afterwards with the anthers (172, 352). Delpino conjectured
that Hedychium must be fertilised by Lepidoptera, and long after-
wards found scales of ‘Lepidoptera on the stigma of the plant
(177). Fritz Miller has shown that the flowers of Hedychium
are arranged so that the pollen may be transported by the wings
of long-tongued butterflies. .

Zingiber officinarum.—Cross-fertilisation is ensured in case of
insect-visits by the prominent position of the stigma (351).

The cultivated plant in South Brazil is only reproduced by
vegetative means, and is quite barren, though pollen, stigma, and
ovule seem to reach normal development. ‘This sterility is
perhaps due to the plants being all portions of one original

stock (359).

Tribe Marantee.

Calathea (Maranta) zebrina, Meyer, and C. discolor, Lindl.,
have, according to Hildebrand, an explosive arrangement, com-

parable to that of several Papilionaceze. A hood-shaped petal, on

the under side of the almost horizontal flower, surrounds the style,
which carries at its extremity the funnel-shaped stigma, and above
the stigma the pollen which is shed upon it in the bud. The
weight of an insect-visitor alighting on the petal itself or on a
hooked process of it, sets the style free. The style then curves
backwards and inwards, so that the ventral surface of the insect
is first swept by the stigma and then dusted with fresh pollen.
The style in curving backwards closes the path to the honey,
so that each flower is only visited once (360, p. 617). Delpino
investigated Maranta bicolor and M. cannefolia, and found their
flower almost identical in structure with the species described by
Hildebrand. He, however, found that part of the style between
the stigma and the pollen secretes a sticky fluid, which is applied
to the insect’s proboscis and causes the pollen to adhere.

Thalia dealbata, Fras., has similar flowers, which are visited
and fertilised abundantly at Florence by the hive-bee.

Delpino has tried, by comparing the flowers of Marantacew
with those of Musacew, Zingiberacee, Cannacee, Orchidee and
Graminew, to trace out the genetic relations of these orders (175).

Sp) ene cae atm. a i I e

~_

nn

oe

ae

PART III. | THE MECHANISMS OF FLOWERS. 543

Maranta arundinacea, L., is sterile in South Brazil, where it is
only propagated asexually. The flowers have ceased to produce
pollen, but retain the elastic style (359).

Tribe Cannee.

Canna.—At an early period the anthers shed all their pollen
upon the expanded style, from which it is removed by insects and
conveyed to other flowers (Delpino, 172). According to Hilde-
brand, spontaneous self-fertilisation very often takes place, and
leads to the production of good fruit (351, 352).

Tribe Musee.

Strelitzia regine, Ait.—The two inner and inferior perianth-
segments, which inclose the five anthers, separate when a visitor
presses upon them in trying to enter the flower; the anthers then
emerge and come in contact with the under surface of the visitor.
The stigma is exserted, and is accordingly always touched before
the anthers. Delpino supposed, and Darwin showed by direct
observation, that the fertilisers are honey-sucking birds (356, p.
508 ; 360, p. 673 ; 178, p. 232; 567, p. 4). At the Cape of Good
Hope, it is fertilised by Nectarinidee (164, p. 371).

Musa.—The Bananas which are cultivated in South Brazil and
propagated only by asexual means, are barren; their anthers
produce very little pollen and wither without dehiscing (359,
p- 275). The flowers of Musa attract insects by an abundant
secretion of sweetish jelly. Zrigona ruficrus, Latr., is attracted in
swarms (590, I. p. 14).

Orv. JRIDEZ.

387. Irn1s Pseup-Acorus, L.—The honey is secreted by the
lower portion of the perianth (d d’ 1, Fig. 181), and is collected in
the space (>) between it and the pistil (a). Access to it is only
possible at three points, between the lower portion of each outer
lobe of the perianth and that of the petaloid style above it. The
filament, adhering as a longitudinal ridge to this portion of each
perianth-segment, divides the passage to the honey into two separate
openings (0b); thus altogether six somewhat narrow passages, two
at the base of each stigmatic lobe, bounded laterally by the pro-
jections from the outer perianth-segments, form the only approaches
to the honey. An insect must have a proboscis at least 7 mm.

544 THE FERTILISATION OF FLOWERS. [PART III.

in length to be able to reach the honey through these passages,
and one of at least double that length to drain one of these spaces
of its honey. Each foliar division of the style bears on its under
surface near its apex a scale-like process, whose upper surface is
the true stigma. Hence insects touch the stigma with their backs
only when creeping in under the petaloid style; for as they creep
out again they push the papillar surface upwards. Close under
the petaloid styles lie the three anthers, whose pollen-covered
surfaces are directed downwards. Self-fertilisation is thus rendered
impossible.

Fig. 181.—Iris Pseud-acorus, L.

1.—Transverse section through the tubular part of the perianth.

2.—Transverse section through the petianth, at the point where its six segments become free.

3.—Transverse section somewhat higher than 2, to show the relation of the three pairs of nectaries
to the divisions of the style and the outer segments of the perianth.

a, style ; a’ a’ a’, the three foliaceous divisions of the style ; b, honey receptacle ; ¢ ec, lower part
of filaments, adherent to the outer segments of the | pigs ddd; ddd, inner segments of the
perianth ; ee, the tworidges on each outer segment of the perianth, which, together with the bases of
the filaments, bound the entrance to the nectary.

Sprengel,! has given a very full account, with figures, of the
flowers of Jris Pseudacorus and J. Xiphium. His observations of
insect-visitors were, however, not nearly sufficient, and his
conception of the mode of fertilisation must be modified.

In Sprengel’s opinion, both species of Iris are fertilised exclusively
by humble-bees. A bee alights on one of the large outer segments of
the perianth, toward the base of which it pushes its way under the
over-hanging petaloid style, until it reaches the entrances to the two
nectaries. After it has sucked the honey it crawls backwards to its
starting-point, and then flies to the second outer perianth-segment,
where it performs the same operation ; thence to the third, thence to
another flower, and so on. On entering the flower, the back of
the bee rubs the upper surface of the scale projecting from the

d Sprengel, No, 702, pp. 69-78, Plate II.

PART III. | THE MECHANISMS OF FLOWERS. 545

petaloid style, which is the functional stigma; a little further on
it rubs against the pollen-covered surface of the anther, which lies
close to the petaloid style. In this way, Sprengel declared that
two stigmas in each flower were regularly fertilised by means of
pollen from the previously-visited anthers of the same flower, and
that the stigma first visited in each flower was always cross-
fertilised by means of pollen from the preceding flower: thus self-
fertilisation took place twice as frequently as cross-fertilisation.
Though Sprengel was not aware of the advantage of cross-fertilisa-
tion, he was repeatedly led by his observations to the conclusion
“that nature is unwilling that any hermaphrodite flower be
fertilised by means of its own pollen.” In order to adhere to this
theory in the ease of Iris, which he abandoned again and again in
other cases, Sprengel chose to Jook upon each third of the flower
in Iris as a separate hermaphrodite flower, which thus was
regularly cross-fertilised.

My frequent observations of insect-visits differ materially from
Sprengel’s view of the case. It is true that humble-bees visit
the flower of Jris pseudacorus, but they, as a rule, act in a way
very different from that which Sprengel described; and a very
much more frequent visitor is, in my experience, the long-tongued
hover-fly, Rhingia rostrata.

In many flowers of Jris pseudacorus the petaloid styles stand
6 to 10 mm. above the corresponding outer perianth-segments. In
others each petaloid style lies so close to the perianth-segments
that only a very small passage is left, which, owing to the con-
vexity ofthe style, lies immediately below the stigma. These two
forms of flowers have adapted themselves to different fertilising
agents.

In flowers of the first variety the fly (Ahingia) crawls along
the outer perianth-segment to the nectaries without touching
either stigma or anther; it inserts its proboscis (11 mm. long)
into one nectary after the other, and then moves a few steps
backwards to feed on the pollen. When under the anther it
raises its head, stretches out its tongue, and so reaches the pollen.
Then it flies to another perianth-segment of the same flower, or to
another flower. Its visits to this variety are thus not only useless
but hurtful, leading to waste of pollen.

In flowers of the other form this fly creeps through the small
passage beneath the true stigma, and touches with its back first the
stigma and then the anther before reaching the nectaries. After

sucking, it creeps backwards without staying to eat pollen, until it
NWN

546 THE FERTILISATION OF FLOWERS. [PART III.

has passed from beneath the petaloid style, when it flies away to
another flower or another perianth-segment of the same. If the fly
be caught as it is creeping backwards from the nectary, many pollen-
grains may always be found among the hairs on its back ; some of
these are without fail applied to the stigmatic surface next visited.
Thus the flowers in which the petaloid-styles stand close to the peri-
anth-segments are better adapted for fertilisation by Rhingia in two
respects than the flowers of the other form: (1) the fly is compelled
to carry pollen to the stigmatic surface, often to that of another
flower, and (2) it is hindered from eating pollen; whereas, in
the flowers of the other form, Rhingia passes in and out without
accomplishing fertilisation, and moreover uses up pollen as well
as honey.

In relation to bees’ visits the conditions are exactly reversed.
When the petaloid style lies close upon the outer perianth-
segment, the opening, which is sufficient for Rhingia, is much
too small to admit a humble-bee. On May 25th, 1868, I watched
a large parasitic humble-bee (Psithyrus vestalis, Foure. 2, 25 mm.
long, and 10 mm. broad) creeping in various directions over the
flowers; finally, placing its head above the base of the free part of
an outer perianth-segment, it inserted its tongue sideways into one
of the nectaries, and so reached the honey without touching either
the stigma or anther.

In flowers of the other form, I have observed frequently in the
case of Bombus agrorum, B. hortorum, and B. Rajellus, that humble-
bees alight on one of the outer perianth-segments, and creep under
the petaloid style to the honey-passages, touching on their way
both stigma and anther with their backs. Instead of crawling
backwards along the path they came by, they climb sideways on
to one of the other outer perianth-segments, and then crawl up it
to enter beneath the stigma, as before. After completing the
circuit of the flower and exhausting all its honey, the bee flies to
another, and so effects cross-fertilisation regularly,

Occasionally, but only in those few flowers where the position
of the petaloid styles was intermediate between the forms that I
have described as typical, I have seen humble-bees creeping back-
wards from under cover of the style, as Sprengel describes them.

The flowers of Iris pseudacorus thus present the interesting
peculiarity that although originally, as their dimensions show, they
were adapted simply for bees, they have since to a great extent
become adapted for fertilisation by flies (Rhingia). Each of the
two extreme forms has its own advantages and disadvantages.

part ui.}| §= THE MECHANISMS OF FLOWERS. 547

Those flowers fitted for fertilisation by bees are at an advantage
in that the bees always cause cross-fertilisation of separate plants ;
but at a disadvantage from having their pollen exposed to robbery
by Rhingia. The flowers adapted for fertilisation by Rhingia have
the disadvantage that self-fertilisation is as frequently or even
more frequently caused than cross-fertilisation; but possess the
advantage that their pollen is not liable to be wasted, and that
they receive more numerous visits. Advantages and disadvantages
must be about equally balanced in the two varieties, since natural
selection has not enabled either to outstrip the other. The rarity
of intermediate forms is explained by the fact that such forms
combine the disadvantages of both extremes; cross-fertilisation
is not secured, and the pollen is not protected from robbery.

Besides the visitors already mentioned one or two useless
guests frequent the flowers. On the variety in which the perianth
and styles stand wide apart, J once saw Osmia rufa, 9, engaged in
sucking honey. This bee was enabled, by the length of its
proboscis (8 mm.), to enjoy the honey without touching either
stigma or anther. I once saw a hive-bee trying to obtain honey.
It crept beneath a style without touching the stigma or anther,
as far as the honey-passages, and then stretched out its
proboscis (6 mm.), which, however, was too short to reach the
honey. After several unsuccessful attempts the bee deserted the
plant and settled on flowers of Ranunculus acris.

Visitors : A. Hymenoptera--Apide : (1) Bombus vestalis, Fource. @ ; (2)
B. agrorum, F. 2 $; (3) B. hortorum, L. 9 §; (4) B. Rajellus, Ill. 2, all four
sucking ; (5) Osmia rufa, L. 9, sucking without effecting fertilisation ; (6) Apis
mellifica, L. $, vainly sucking honey. B. Diptera—Syrphide: (7) Rhingia
rostrata, L.; s. and f.p.

A species of Cypella, in S. Brazil, according to Fritz Miiller,
increases its conspicuousness very effectually by not expanding
its flowers regularly day by day but by concentrating them upon
certain days (597).

Crocus vernus, All_—Honey is secreted by the ovary, and rises
in the narrow tube (almost filled by the style) nearly to the upper,
somewhat expanded end. It can only be completely extracted by
long-tongued Lepidoptera, while humble-bees as a rule can only
skim the surface. By the violet or more frequently white colour
the flowers seem to be adapted for crepuscular and nocturnal
Lepidoptera. Ihave found them visited by Plusia gamma, less

often by Vanessa cardui, and occasionally by humble-bees. At first,
| NN 2

548 THE FERTILISATION OF FLOWERS. [PART III.

only the anthers, which dehisce extrorsely, are exposed to contact
with the insects; afterwards the stigmas unfold between them.
Cross-fertilisation is thus insured in case of insect-visits; in absence
of insects, the cup-shaped or rather grooved stigmas, passing out
between the anthers, are dusted with their pollen (609, fig. 10).

In Crocus sativus, All., the ovary secretes honey, according
to Sprengel (742, p. 68).

Gladiolus, Treviranus states that flowers of this genus are
self-fertilised, the style curving back towards the anthers (742).

Gladiolus segetwm has proterandrous flowers formed on the
Labiate type according to Delpino. In addition to the her-
maphrodite flowers others occur containing a pistil only (178,
p. 184, 360, p. 670).

Gladiolus palustris, Gand., and G. communis, L., are visited
by bees and humble-bees (590, 1).

Orv. LILIACEZ.

388. ASPARAGUS OFFICINALIS, L.—This plant supplies an
undoubted instance of a transition stage between monecism and

Fic. 182.—Asparagus officinalis, L.

1.—Male flower, from below.

2.—Ditto, after removal of half the perianth.
3.—Female flower, from below,

4,—Ditto, after removal of half the perianth.
a, rudimentary stamen; b, rudimentary ovary.

diecism. The flowers of the male individuals show distinctly

a rudiment of a pistil (b, 2, fig. 182), and those of the female
individuals show functionless but still conspicuous rudiments of

PART III. | THE MECHANISMS OF FLOWERS, 549

anthers (a, 3). Occasionally reversion to the hermaphrodite
condition takes place, and then in the hermaphrodite flowers the
pistil may sometimes be seen in various degrees of abortion.1
The pendulous bell-shaped flowers have a pleasant scent; in spite
of their inconspicuous colour they are easily visible at a distance,
the male flowers, which are 6 mm. long, being much more so than
the females (8 mm.). This instance confirms Sprengel’s oft-
repeated rule that the male flowers of diclinic plants are more
conspicuous than the female, whence insects are likely to visit the
two kinds of flowers in the proper sequence. Honey is secreted
and lodged in the base of the corolla.

Visitors : Hymenoptera—A pide: (1) Apis mellifica, L. $, s. and c.p., very
ab. ; (2) Osmia rufa, L. 9, s.; (3) Megachile centuncularis, L. 9, s. ; (4)
Prosopis annularis, K. (Sm.) 9, s.; (5) Halictus sexnotatus, K. 9, c¢.p., here

and there looking for pollen in the female flowers and effecting fertilisation
occasionally,

389. CONVALLARIA MAJALIS, L.—When the flower opens, and
before the anthers ripen, the stigma is already covered with long

Fic. 183.—Convallaria majalis, L.

1.—Flower, from below.
2.—Ditto, after removing half the corolla, with three of the stamens.
st, filaments; a, anthers ; fr, ovary; n, stigma.

papiile ; yet if a ripe anther be passed over its surface scarcely
any pollen adheres. Afterwards, when the anthers have dehisced,
the stigma becomes covered with a sticky fluid, to which pollen
adheres readily. I have not found honey in the flowers, though
I have frequently seen hive-bees visiting them. The bees collected
pollen hanging to the pendulous flowers and inserting their heads
and forelegs. They thus brought their heads in contact with
the stigma before the anthers, and performed cross-fertilisation
regularly. Then as the bee swept the pollen from the anthers
with the tarsal brushes of its forelegs, it dusted its head anew
1 Breitenbach, Bot. Zeitung, Nov. 11, 1878.

550 THE FERTILISATION OF FLOWERS. [PART ILI.

with pollen. In absence of insects, self-fertilisation takes place
regularly, as Hildebrand has shown (351); for the anthers stand
close round the style and apply their pollen to the marginal
papille of the trilobed stigma.

390. CONVALLARIA MULTIFLORA, L.—The honey lies at the
base of the flower between: the perianth and the ovary. The
length of the perianth tube, which is 11 to 15 mm. long (or even
18 mm. in cultivated plants) protects the honey from short-lipped
insects, and the pendulous position of the flower protects it from
rain. Humble-bees visit the flowers; they thrust their heads into
the wide part of the tube, and touch the stigma which stands
in the mouth of the flower, and the anthers which ripen simul-

taneously with it, with opposite sides of their heads or tongues.

They thus effect cross-fertilisation regularly. In each flower the
bee in touching one side of the stigma thrusts the opposite
side against the anthers. In absence of insects, spontaneous
self-fertilisation occurs.

Visitors: A. Hymenoptera—A pide : (1) Bombusagrorum, F. 9 (12—15) ;
(2) B. hortorum, L. 2 (19—21), s., hanging, back downwards, on the flowers.
B. Diptera—Syrphide : (3) Rhingia rostrata, L. (11—12), very ab., often two
at the mouth of the same flower,—sucking in vain for honey, which its tongue
is too short to reach, then collecting pollen and occasionally effecting fertilisa-
tion by stroking the stigmas.

Convallaria verticillata, L., is adapted for fertilisation by bees ;
C.. polygonatum, L., for fertilisation by humble-bees. The anthers
and stigma are matured simultaneously, and, in C. verticillata at
least, some pollen as it emerges from the anthers always reaches
the stigma. It is probable that it is outstripped in its action by
pollen brought from other flowers (609).

| Asprdistra elatior, Blume.——Buchenau described the structure
of the flower thoroughly, but was unable to elucidate its
mechanism fully. Delpino, however, has endeavoured, with
apparent success, to explain the mechanism of the flower, though
he failed to find it visited by insects (118, 178, 360).

The capitate stigma closes the flower, leaving only four small
openings through which Delpino supposes small flies to enter;
the pollen falls out of the anthers and lies in the cavity of the
flower. The flies emerge all dusted with pollen, and alighting on
the stigma of another flower place some pollen there before they
find the small entrance.

en ee aes

PART III. | THE MECHANISMS OF FLOWERS. 551

Rohdea juponica, Kunth.—This plant is, according to Delpino,
a link between the Asparaginee and the Aroidew. It possesses
a kind of spadix, on which the flowers are arranged in a close,
uninterrupted spiral. The fact that the limb of the perianth is
spread out exactly on a level with the points of the anthers and
stigma led Delpino to think that fertilisation was effected by small
animals crawling over the flowers. He observed snails (Helix
aspersa, H. vermicularis) greedily eating the perianth, which is
yellow and fleshy; after devouring about ten flowers they crawled
to another spadix. Only those flowers on which the snails had
crawled proved fertile; the flowers were found to be barren to
their own pollen. These observations leave no doubt that snails
are really efficient fertilising agents.

Tritoma Uvaria is adapted for fertilisation by diurnal
Lepidoptera (228).

Yueca,— According to Riley (108) the species of Yucca which
are provided with a dehiscent capsular fruit, and the moth which

Fic. 184.—Yucca and the Yucea-moth.

1.— Flower of Yueca recurvata, Salisb., from Georgia. Two Care of the
perianth have been removed to show the ovary (ov) and stamens (a). §
2.—Stigma, from above, x 44.
3.—End of astamen, x 4}. ji, filament; po, pollen.
4.—The Yucca-moth, Pronuba yuccasella, Riley.
5.—Ditto, with outspread wings. se ‘
6.—Head. m, mandibular palp; m’, first joint of ditto; po, pollen.
7.— Mandibular palp of female.
8.—Ditto, of male.
9.— Ovipositor.
10.—A bristle from 7,
(4—10, after Riley).

effects their cross-fertilisation (Pronuba yuccasella, Riley) stand in
close interdependence. In the female of this moth the first joint
of each of the two maxillary palps is transformed into a long
prehensile organ, which can be rolled up, and which serves to seize
the pollen with. After the female has bored the ovary in several

552, THE FERTILISATION OF FLOWERS. [PART III,

places and deposited an egg in each hole, it repeatedly collects
pollen from the anthers with these peculiar organs, places it on
the stigma, and thrusts it into the cavity, the moisture in which it
at the same time sucks. The larve now develop in the ovary, and
along with them the seeds, which serve as their food, develop also,
and in such numbers that the propagation of the plant remains
ensured. When full-grown the larva boresa hole through the
capsule, lowers itself to the ground by a thread, bores some inches
deep into the ground and spins a cocoon in which it passes autumn,
winter, and spring ; it passes into the pupa stage about fourteen
days before the Yuccas begin to flower and emerges at the time
when they do so (667—671, &c.).

Paradisia Liliastrum, Bertolon, is adapted for fertilisation by
nocturnal Lepidoptera. The honey is very abundant, and is
secreted, as in Convallaria, by the deep longitudinal slits in the
ovary, between the carpels. The flower is white, and the stigma
and anthers are placed as in Lilium Martagon, Lonicera Pericely-
menum, and many other nocturnal flowers (600, fig. 7).

Eremurus spectabilis—The flowers lose their conspicuousness
before the stigma and anthers are mature (367). Asin the case of
Weigelia, Lantana, and many other flowers whose colours change,
the gain hereby is that the less intelligent and useless guests are
attracted away to the more conspicuous flowers which contain no
treasure for them (612).

391. ANTHERICUM RAMOSUM, L.—The flowers are regular, and
open widely, exposing their honey so much that the most short-
lipped insects can see and reach it. The honey is secreted by the
upper part of the ovary, on which it lies in three drops (Sprengel,
pl. xxii. fig. 8).

On the Rehmberg near Mihlberg in July, 1868, I had an
opportunity of observing this plant in sunny weather under its
natural surroundings. The flowers were assiduously visited by
bees, sucking honey and collecting pollen. Each time they alighted
they first touched the projecting stigma and then the anthers, thus
causing cross-fertilisation regularly. A handsome black and green
fly (Merodon eneus, Men.) hovered round the flowers in even greater
numbers than the honey-bee, sucking the honey and eating pollen ;
it was in fact the principal fertiliser. Two butterflies, the Swallow-
tail (Papilio Machaon) and a Fritillary (Melitea Athalia, Esp.),
sucked the honey. Their long thin tongues did not touch or only
touched by accident the stigmas and anthers; but as they usually

PART ITI. | THE MECHANISMS OF FLOWERS. 553

sat upon one flower while sucking another, cross-fertilisation
(owing to the prominent situation of the stigma) was often effected
by pollen adhering to the under surface of their bodies. In absence
of insects, self-fertilisation can only take place in flowers directed
more or less downwards.

Visitors : A. Hymenoptera—Apide : (1) Apis mellifica, L. $,s. and f.p.
B. Diptera—Syrphide : (2) Merodon eneus, Mgn.,s. andf.p. C. Lepidoptera
—Rhopalocera: (3) Papilio Machaon, L., s.; (4) Meliteea Athalia, Esp., s.
Visited also by many other insects. See No. 590, 1.

Anthericum Liliago, L.—The flower resembles that of the
former species (590, I).

392. ALLIUM uRSINUM, L.—When the flower first opens the
style is only from one-third to one-half of its ultimate length ;
the papille are not yet developed on the stigma, and the
anthers are still allimmature. First of all the three inner anthers
dehisce at slow intervals, one after the other; at this stage
the style has reached three-quarters or more of its full length
(43 to 5 mm.). Then the three outer anthers dehisce one after
another; the style has now reached its full length (6. mm.), and
the papille on the stigma become developed. The flowers are thus
imperfectly proterandrous. The anthers dehisce introrsely, and
then turn that side which is covered with pollen more or less
upwards. In specimens flowering in my reom I found some flowers
in which the style was so bent during the last stage that the stigma
touched one of the anthers which still retained some of its pollen.
In this way self-fertilisation was effected to a limited extent when
no insect visited the flower. In a wood at Stromberg Schloss-
berg on the 16th May, 1868, I saw Bombus pratorum, 9, flying
quickly from flower to flower of A. w7sinum ; she thrust her proboscis
into each flower in search of honey, and after scarcely two seconds
hurried on. The honey is secreted by the ovary, in the three
notches between the carpels, and fills the space between these
notches and the bases of the three inner stamens, Hence the bee
when sucking must touch the stigma with one side of its head and
the anthers with the opposite side, and, in old flowers, can only
lead to cross-fertilisation.

393. ALLIUM CEPA, L.—The honey in this species is placed in
the same position as in the preceding one; the anthers and stigma
are also similarly situated.

554 THE FERTILISATION OF FLOWERS. [PART IIT.

Visitors: A. Hymenoptera—(a) Apidae: (1) Bombus terrestris, L. ¢; (2)
Halictus cylindricus, F. ¢; (3) Prosopis punctulatissima, Sm.; (b) Sphegide :
(4) Miscus campestris, Latr. B. Diptera—(5) Empis livida, L., all sucking.

Allium carinatum and A. fistulosum.—Sprengel found these
species to be proterandrous. He has observed honey-bees in
numbers sucking honey on the flowers of the latter.

Allium spherocephalum, L., is visited by bees, flies, and
Lepidoptera (609).

Allium Schenoprasum, 8. alpinum, is proterandrous and very rich
in honey. It is much visited by small moths (Crambus), even at
2,000 m. above the sea-level (665).

Allium rotundum, L., is adapted for fertilisation by sand-wasps
and bees. The three nectaries are concealed by the expanded

bases of three of the stamens; the long filamentous processes of |

the stamens protrude from the flower, and probably serve to guide
the bee towards the honey (590, 1).

Allium victoriale, L., is markedly proterandrous. The honey is
displayed openly, and the yellowish-white flowers, which are ex-
ceedingly conspicuous on their tall stalks, are visited by numerous
flies, bees, and Lepidoptera (609).

Allium sibiricwm has proterandrous flowers, which have been
figured by Axell (17).

The flowers of Hemerocallis fulva are sterile to their own
pollen according to Sprengel (p. 43).

Muscari botryoides, Mill., and M. racemosum, Mill., are visited
by bees and adapted for fertilisation by them (590, 1).

Scilla maritima, L., is visited by bees (590, 1).

394. HYACINTHUS ORIENTALIS, L.—The perianth forms a
tube, 12 to 14mm. or more in length, produced into six outspread
and recurved teeth. In its lower third is the ovary, with a short
style and tripartite stigma; in the middle third are the anthers,
which dehisce introrsely and ripen at the same time as the stigmas.
No free honey is secreted, but the wall of the perianth is fleshy
and succulent, and is probably bored by long-tongued insect-
visitors. When an insect’s: proboscis is thrust into a flower it
touches the anthers and stigmas with opposite sides, and so cross-
fertilisation is favoured. Spontaneous self-fertilisation can only
occur in flowers which happen to be inclined sideways.

Honey is said by Linnzus and by Sprengel to be secreted in

ee

—ee

PART III. | THE MECHANISMS OF FLOWERS. 555

three glands in the angles of the ovary, but I have not been able
to detect it (cf. W. J. Behrens, No. 51).

Visitors : A. Hymenoptera—A pide : (1) Bombus terrestris, L. 2 ; (2) An-
thophora pilipes, F. 2? ¢, ab. ; (3) Andrena fulva, Schrk. 9; (4) Osmia rufa,
L. g, very ab., all sucking. B. Diptera—Syrphide : (5) Cheilosia sp. sucking
in vain forhoney. C. Coleoptera—WNitidulide : (6) Meligethes, on the anthers
in large numbers, apparently feeding on the pollen. See also No. 590, 1.

Lloydia serotina, Rchb.—This plant shows an advance on the
foregoing Liliacese in the possession of special nectaries, consisting
of a thick ridge at the base and in the middle line of each segment
of the perianth. The flower is proterandrous, but the stigma
ripens simultaneously with the inner whorl of stamens; in some
cases it stands on a level with their anthers, in others above them,
so that self-fertilisation is possible or not respectively (609).

Fic. 185.—Lilium Martagon, L.

A.—Flower, in its natural position, seen from the side (natural size),
B.—A petal (x 2).
e, entrance into the nectary (n).

Lilium Martagon, L., is adapted for cross-fertilisation by Sphin-
gide ; Noctuide also assist in the work. The anthers and stigma
ripen simultaneously, and are touched by the feet and under surface
of theinsect. Self-fertilisation also occurs, as Sprengel found. The
perfume of the flower begins to be emitted strongly at night
(570, 590, I, 609). |

Lilium bulbiferum, L., is adapted for fertilisation by diurnal
Lepidoptera. A nectary in this species and in L. Martagon is
situated in the middle line at the base of each segment of the
perianth ; but it is not a ridge merely, as in Lloydia, but a deep
groove, whose edges, bordered by stiff hairs, rise up and arch over

556 THE FERTILISATION OF FLOWERS. [PART IIT,

to form a tube, through which the honey has to be sucked. All
but long-tongued insects are thus excluded (570, 609).

Lilium croceum, Chaix., is sterile to its own pollen (248).

Gagea lutea, Schult., and G. arvensis, Schult.—The former is
proterogynous, but the anthers dehisce soon after the stigma is
mature. Bees visit both species (590, 1.).

Gagea Liottardi, Schult.—Anthers and stigma ripen simul-
taneously, but the golden colour of the flowers and the abundant
honey attract numerous insect-visitors, chiefly Diptera, so that
cross-fertilisation must generally occurs (609).

Fritillaria imperialis, L., is visited by the hive-bee (590, 1).

395. CoLCHICUM AUTUMNALE, L.—In most cases, the use
of a long, tubular corolla is to exclude short-lipped insects
from the honey when they are useless for the work of ferti-
lisation. But Sprengel has rightly insisted (702, p. 208) that
in this plant the length of the corolla-tube (which rises directly
from the bulb) is merely of use in permitting the fruit to lie
buried in the earth, and indeed hidden within the bulb, and so
to be sheltered from cold during the winter. The honey does not
lie in the corolla-tube, but is secreted by the yellow outer surface
of the lower part of the free portion of the filaments; and it lies
within grooves of the corolla, covered over by protective hairs.
The stigmas mature before the anthers (a fact which Sprengel
overlooked), but remain fresh and capable of fecundation until the
anthers ripen. If insects’ visits occur in time, cross-fertilisation
is inevitable, owing to the proterogynous dichogamy of the flower ;
if they do not occur till late, self-fertilisation also is possible, but
it is rendered unlikely by the circumstance that the anthers turn
their pollen-covered surfaces outwards ; if no insects visit the flower
this movement of the anthers probably prevents spontaneous self-
fertilisation.

On the morning of Sept. 19, 1869, at Driburg, I found several
flowers still closed in their night's sleep, which when opened
displayed anthers not yet ripe, but stigmas richly coated with
pollen. Rather later, when the sun came out, I found several
males of Bombus hortorum busy creeping or flying from flower to
flower, and sucking honey from the angles between the filaments
and petals. As they crept into the flowers they touched both
stigmas and anthers with their forelegs, head, or the anterior part
of their bodies, dusting these parts plentifully with pollen in flowers
whose anthers were mature.

ee

PART III. | THE MECHANISMS OF FLOWERS. 557

Tofieldia calyculata, Wahlenb., is proterogynous; 7. borealis,
Wahlenb., is homogamous. The flowers in both species are
yellow, and the visitors are chiefly, but not exclusively, flies and
beetles. The much smaller flowers of 7. borealis are less visited
than the more conspicuous flowers of 7’. calyculata, but the former
species makes up in part by an increased secretion of honey. Its
flowers, being homogamous, have a better chance of self-fertilisation
in default of insect-visits (609).

Methonica (Gloriosa) superba has a pendulous flower, whose
stamens and style are directed horizontally outwards, and serve,
according to Delpino, as a platform for insects (172). Hildebrand
states that in young flowers the style serves as an alighting-place,
while the stamens lie deeper; and that in older flowers the
stamens assume this function, so that cross-fertilisation of young
flowers with pollen from older proceeds regularly (352).

Paris quadrifolia.—1 was long puzzled to discover how this
flower is fertilised.

The stigmas are already mature when the flowers open; the
anthers dehisce several days later, the stigmas still remaining
fresh. The pollen-grains are about ‘04 mm. long by ‘(016 mm.
broad; they remain adhering in great quantity to the ripe
anthers, but fly off on the slightest touch in a cloud of separate
grains. The nature of the pollen and the complete absence of
honey and of a coloured perianth point to the flowers as being
anemophilous, The stiff filaments and the long connectives, which
are produced into awn-like prolongations, do not support this view,
unless they assist the transport of the pollen by the wind when
they are shaken by pollen-feeding flies alighting on them.

I wrote the above in 1872, and I did not discover till six years
later that the flower of Paris becomes intelligible in all its parts
when one looks upon it as adapted for Diptera; and I observed
then that in fact it is visited by Diptera. The dark purple ovary,
crowned by four stigmas of the same colour, glitters as if it were
covered with moisture ; and by this appearance and by its dis-
agreeable smell it attracts Scatophaga merdaria and other carrion-
feeding Diptera. These visitors often alight upon the stigma
and lick the ovary with their labelle, and then climbing up the
anthers, dust the soles of their feet or the whole under-surface
of their bodies with pollen. So, flying away to other flowers, they
accomplish cross-fertilisation (589).

Veratrum albwm, L., is proterandrous. Some plants possess, in
addition to the hermaphrodite flowers, male flowers also; others

558 THE FERTILISATION OF FLOWERS. [PART III.

bear male flowers only. That is to say, the species exhibits a
passage through andromonescism to androdiccism. The flowers
are dirty-yellow, and the visitors are principally flies (609).

REVIEW OF LILIACEZ.

In regard to the genetic relations of Liliacez, the following
conclusions may be drawn from the floral characters that have
just been described.

The Liliaceze must have once possessed open, regular flowers
devoid of honey, visited and cross-fertilised by pollen-seeking
insects only. They attained, after dividing into several groups,
to the secretion of open, freely accessible, honey, partly secreted
by the segments of the perianth, partly by the carpels; and
in part they still remain honeyless, and are still crossed only by
insects which collect or feed on pollen (Tulipa), or else have
become developed into deceptive flowers which attract stupid carrion-
loving flies (Paris). Those Liliacez in which honey is secreted by
the carpels have in part open flowers with generally accessible
honey (Tofieldia, Anthericum); but in part they have become
adapted, by approximation of the perianth-segments, for a limited
but still very miscellaneous lot of visitors (Allium), or even to a
special long-proboscised form (Paradisia), or by cohesion of the
perianth-segments into a longer or shorter pendulous bell, to bees
in general (Convallaria verticillata) or to humble-bees and other
long-proboscised bees only (C. Polygonatwm). Similarly those
Liliaceze in which the honey is secreted by the segments of the
perianth have in part remained with fully or moderately open
flowers, destined for cross-fertilisation chiefly by short-lipped in-
sects (Diptera), (Veratrum, Gagea, Lloydia) ; in others the perianth-
segments have become approximated without cohesion to form a
pendulous bell, fertilised by bees (Fritillaria); in others the
nectaries have become modified into narrow covered grooves,
which are only accessible to Lepidoptera (Lilium); and, finally,
in this last genus adaptation has passed from diurnal Lepidoptera
to Sphingidz in the case of Lilium Martagon. |

These various adaptations have all taken place with complete
or almost complete retention of the regular symmetry of the flower ;
only the adaptation to Lepidoptera (in Paradisia and Lilium) and
the oblique position of the flower in Anthericum have caused an

PART III. | THE MECHANISMS OF FLOWERS. 559

unsymmetrical curvature of the reproductive organs especially of
the style.

The colour of the perianth in Liliaceze must originally have
been greenish, as it still is in Paris, while the flowers at first
made themselves conspicuous to insects by the colour of: the
reproductive organs. By the selective agency of short-lipped
insects, those flowers which had freely-visible honey, and then
such as had their honey partially concealed, developed greenish-
yellow colours (Veratrum), yellow (Tofieldia, Gagea), greenish-
white and white (Lloydia, Anthericum), and their perianth-
segments became devoted to purposes of display. It was only
when sand-wasps, bees, long-tongued flies and Lepidoptera began
to play a leading part as the fertilising agents, and led to the
development of flowers that were no longer accessible to the
great host of short-lipped visitors, that red, violet, and blue
colours began to be developed through the higher colour-sense of
these insects. In the genus Allium, for instance, the species with more
accessible honey (A. wrsinum, A. victoriale) have a white perianth ;
those with less accessible honey, which are visited chiefly by
sand-wasps and bees, and also by-Lepidoptera and long-proboscised
flies (eg. A. rotunduwm), have the perianth red. In Liliacex,
as in other cases, the flowers which are fertilised by bees have by
far the greatest variety of colour, as we see by a glance at Tulipa,
Fritillaria, Scilla, Muscari, Hyacinthus, Asparagus, and Conval-
laria. The colours of those which are fertilised by Lepidoptera
are far less various. JLiliwm bulbiferwm, which is fertilised by
diurnal Lepidoptera, is clothed in fiery red; Paradisia, which is
adapted for nocturnal species, is white; LZ. Martagon, which
only became modified for Sphingidze supplementarily, has ex-
changed its bright colours for dull ones since it ceased to be
fertilised by diurnal Lepidoptera (609, pp. 55, 56).

Orv, AMARYLLIDEZ.

396. GALANTHUS NIVALIS, All.—Sprengel has given a full,
and on the whole accurate, account of this flower; he was, however,
inaccurate in regard to the structures which he supposed to
shelter the honey, and his account is incomplete in regard to the
circuinstances which favour cross-fertilisation.

The green parts of the grooves on the inner surface of the
inner petals secrete and lodge the honey, which is sufficiently
sheltered from rain by the pendulous position of the flower. As

560 THE FERTILISATION OF FLOWERS. [PART III.

Sprengel has correctly stated, the six anthers, which lie close
round the style, dehisce by apical slits, and when touched permit
a little pollen to fall out; each anther sends a process outwards
towards the perianth, but this is not at all a contrivance to guard
the honey from rain, but a very important arrangement favouring
cross-fertilisation. For when an insect tries to reach the honey, it
cannot avoid touching one or more of these anther-processes, and
so causes the pollen to be shaken out upon its head. The style
projects beyond the anthers, and the insect therefore touches the
stigma before it gets dusted with the pollen of the flower. In case
of insect-visits, cross-fertilisation is thus ensured; but in absence
of insects self-fertilisation is apt to take place by dled oe on
the stigma.

The hive-bee visits the flowers diligently in sunny weather,
as Sprengel observed; alighting on one of the outer perianth-
segments. If in search of pollen, it thrusts its head, forelegs, and
midlegs into the flower, clinging by means of its hindlegs to the
outer surface of an inner perianth-segment. With the tarsal
brushes of its fore and mid-legs it sweeps pollen from the anthers,
and places it in the baskets on its hindlegs. If it wishes to suck
honey, it usually finds it more convenient to use its fore and mid-
legs for clinging to the perianth. In either case the bee’s head
may always be found covered plentifully with pollen.

Narcissus Tazetta.—Delpino thinks that this species is chiefly
fertilised, like many other Amaryllidez, by nocturnal or crepuscular
Lepidoptera. However, he has directly observed it to be visited
by Anthophora pilipes (177, p. 59).

Crinum.—A. species with white, sweet-scented flowers, about
seven inches long, is believed by Delpino to be fertilised by
butterflies and by honey-sucking birds in its native country, and
by butterflies in Florence. He found butterflies’ scales upon the
stigma, and saw good seed repeatedly borne by the flowers. The
essential organs are exserted, and the stigmatic surface is not
exposed until the anthers have withered (177, p. 56).

Pancratium maritimum.—-The honey is very deeply situated,
and the flower seems to be adapted for Sphinx Convolvuli by which
it is very frequently visited (172, p. 17; 352, p. 794).

Orv. TACCACE@.

Tacca (Ataccia) cristata.—The flower, in Delpino’s opinion, has a
similar mechanism to that of Aspidistra elatior (178, 360).

oh igi

PART III. | THE MECHANISMS OF FLOWERS. 561

Orv. DIOSCOREACEZ,

Dioscorea.—The species which are cultivated in South Brazil
and propagated there asexually, never, with one exception, produce
flowers (359).

Orv. PONTEDERIACE 2.

Pontederia is remarkable as a trimorphic monocotyledon. My
brother Fritz Miiller found only long-styled and _ short-styled
individuals of an apparently trimorphic species of Pontederia, on
the banks of the Itajahy-mirim in South Brazil; while another
species, P. (Hichornia) crassipes, which has been introduced as an
ornamental plant into the colony of Blumenau, exists there in
long-, mid-, and short-styled individuals (556).

Monochoria, L, has cleistogamic flowers, according to Kuhn

(399).

Orv. COMMELINACEZ.

Weinmann has observed subterranean cleistogamic flowers in

Commelina bengalensis (531).
Tradescantia erecta produces cleistogamic flowers in Kew

(330).
| Orv. JUNCACE.

Juncus and Luzula have anemophilous flowers in which self-
fertilisation is for the most part rendered impossible by proterogyny.
The proterogynous flowers of Zuzula pilosa have been figured
by Hildebrand (351, fig. 4), those of Juncus filiformis by Axell
(17, p. 38). So far as their proterogynous condition is concerned,
the flowers of Luzula campestris agree perfectly with those of
L, pilosa.

Juncus bufonius, according to Batalin (39), is exclusively self-
fertilised in Russia, the flowers, which are triandrous, remaining
closed. According to Ascherson (10), the same species at Halle has
ordinary open, lateral, hexandrous flowers, in addition to terminal
cleistogamic, triandrous ones. This statement is confirmed by
Haussknecht,! who found hybrids between J. lufonius and
J. spherocarpus, whose flowers always expand fully.

Luzula lutea and L. nivea attract insects by their conspicuous

1 Botanische Zeitung, p. 802, 1871.
OO

562 THE FERTILISATION OF FLOWERS. [PART III.

colour; the former shows in other respects also remarkable
approximations to the condition of an entomophilous flower.
Indeed, if the pollen-grains of Z. /utea, instead of being smooth and
powdery, became adhesive, the plant might be supposed to have
attained the rank of an entomophilous species (609, fig. 1).

Orv. PALM.

Sabal Adamsoni has a white perianth which contains honey ;
it is proterogynous and is fertilised by insects (Halictus, Polistes
gallica). Chamedorea is also entomophilous ; Cocos and Syagrus,
on the other hand, are anemophilous (177, -p. 61).

Orv. AROIDEZ.

397. ARUM MACULATUM, L.—The arrangement of the flowers
in this species agrees so completely with Delpino’s excellent
account of Arum italicum (178, 360) that I have little new to add,
The upper part of the spathe (d,1, Fig. 185) serves as a wide,
conspicuous entrance, guiding small Diptera (Psychoda) into the
lower chamber (ce) which forms a temporary prison. The insects
creep down the dark-red spadix (¢) or sometimes the sides of
the spathe until they reach the upper part of the chamber (at the
level of a, b, 1, Fig. 185). At this point several rows of hairs
(metamorphosed stamens) radiate outwards, pointing slightly down-
wards, from the spadix, and form ‘a palisade which does not
prevent the small visitors from creeping down into the chamber
(c), but afterwards prevents them from escaping when they try
to fly towards the light. Even when they try to escape by
crawling up the spadix, the sharp downturned points bar their
way.

In the first stage of flowering the stigmas only, which are
borne by the base of the spadix, are mature; a foul ammoniacal
smell attracts the Psychodz into the prison, where they cross-
fertilise the stigmas if they have come from other plants. In the
second stage the stigmatic papillae wither, and a drop of. honey
appears in the middle of each stigma, to reward the little visitors
for their pains. In the third stage the anthers dehisce, and the
greater part of their pollen falls upon the floor of the chamber;
the insects dust themselves over and over with it, and finally,
when the palisade of hairs withers in the fourth period, they pass
out, and enter another flower in its first stage.

PART IIL. | THE MECHANISMS OF FLOWERS. 563

Delpino has observed Arum italicum to be fertilised by six
different flies, of the genera Ceratopogon, Chironomus, Sciara,
LPsychoda, Limosina, and Drosophila (178,-p. 243). In Arum
maculatum I have only found Psychoda, but it occurs almost
constantly, and sometimes by hundreds in a single spathe. I
could often see, on looking down through the grating, that many
of the prisoners were trying to fly upwards to the light, and
falling backwards, or trying to crawl out and being repulsed by
the sharp points. Whenever I broke open a spathe in the third

Fig. 185.—Arum maculaium, L.

1.—The whole inflorescence, x 4.

2.—Transverse section at the level of ab (1), seen from above, on a somewhat larger scale.

ab, point at which the cage c is closed by stiff hairs, radiating from the spadix; c, cage inclosing
the spadix with its reproductive organs; d, attractive portion of spathe; e, barren portion of
spadix, serving as a guide-post; f, cross-section of spathe; g, ditto of spadix; h, stamens trans-
formed into stiff filaments,

stage of flowering, I always found a multitude of inmates groping
about in the thick layer of pollen on the floor of the chamber.
The Psychodz which I collected were so various in size and colour
that I supposed I had obtained at least three species; but Herr
Winnertz of Crefeld tells me that they all belong to the very
variable species Psychoda phalenoides, L., which is probably the
same species found by Delpino in Arwim ttalicwm, and identified
by Rondani as Psychoda nervosa, Schr."

1 According to Schiner, Psychoda phalenoides, 1.., is identical with P. nervoca,

Mgn,, and perhaps also with Tipula nervosa, Schrank.
00 2

564 THE FERTILISATION OF FLOWERS. [PART III.

Arum dracunculus (Dracunculus vulgaris) is visited accord-
ing to Delpino by flesh-eating flies, as is also Amorphophallus
campanulatus (178, p. 238). According to Arcangeli it is fertilised
almost exclusively by carrion-loving beetles (Saprinus, Dermestes,
Oxytelus (7).

Arisarum is distinguished from Arum by the following
features. The edges of the spathe do not meet, the aborted
stamens are absent, and so the spathe surrounds a cavity which
insect-visitors can enter or leave at will. The stigmas are still
capable of impregnation when the anthers, which stand above
them, dehisce, so that self-fertilisation may occur (178, p. 21;
360, p. 591).

Alocasia odora is supposed by Delpino to be fertilised by
snails. The spadix is covered in its whole length with normal and
abortive stamens and pistils; only female flowers occur in the
lower, wider part of the spathe, and they only are mature in the
first period. From this chamber an attractive odour issues, and
the snails are admitted by a narrow entrance. In the second
stage this entrance closes, and the anthers dehisce. Snails which
creep on to flowers in this stage seek vainly for the entrance, and
dust themselves with pollen, which they afterwards carry to the
stigmas of younger plants. Delpino supposes that the snails, after
effecting cross-fertilisation, are poisoned by an irritant secretion
within the chamber of the spathe, and are so prevented from >
devouring the flowers (178, 360).

In Delpino’s opinion, Zyphonium cuspidatum, Arisema fili-
forme, Amorphophallus variabilis, Atherurus tripartitus, and
species of Anthurium are also fertilised by snails (178, p. 238).

Arum ternatum, Thnbg., is proterogynous. There is an upper
male chamber, and immediately below it a female chamber into
which the pollen falls wpon the imprisoned insects (probably small
flies), which are afterwards allowed to escape by a small door
(107, 596).

Arum crinitum, Ait., resembles A. maculatum, but attracts
carrion-flies by means of its strong odour of putrid flesh. The
smaller visitors are held fast by sticky hairs in the floral chamber
and digested (688, 689).

The gigantic Amorphophallus (Conophallus) Titanwm, whose
spathe is 33 inches in diameter, and the bare part of whose floral
axis attains a length of 6 feet, is adapted, by its dirty-yellow and
dark-purple colours, for dung- and carrion-flies (48).

Stylochiton hypogeus, Lepr., and St. lancifolius, Kotschy and

PART III. | THE MECHANTSMS OF FLOWERS. 565

Peyritsch, from Central Africa, remain with their inflorescence,
which consists of male and female flowers, and is inclosed within
a spathe (like our Arwm), beneath the ground; the tip only pro-
trudes, and by it the fertilismg agents creep into the floral
chamber. A similar condition exists in Liarwm and Cryptocoryne
(222).

Calla palustris, L—This plant exhibits a first step towards
the condition of things which is perfected in Arum maculatum.
Its disgusting smell protects it from injurious animals, and attracts
carrion-loving flies. The white spathe is very conspicuous, and the
proterogynous condition is very distinctly marked (590, 1.). . Eug.
Warming (762) attributes a share in the work of fertilisation to
pond-snails,

Symplocarpus fatidus—This shows an intermediate stage
between the open spathe of Calla palustris and the closed
prison of Arwm maculatum (728).

In Ambrosinia Bassii the anthers are within the spathe, the
stigmas outside, at the end of the spadix. The fertilising agents
(flies) creep down the spadix, and so in each plant come in contact
with the stigmas before the anthers (178, p. 230).

Anthurium Pothos is proterogynous with short-lived stigmas,
like most other Aroidez (177, p. 62).

Orv. LEMNACEZ.

Lemna minor, L., according to Ludwig, is adapted for fertilisation
by insects which live upon the surface of the water; so also,
apparently, are L. trisulea, L. gibba, and L. polyrrhiza (435).

Orv. ALISMAC EZ.

398. AtismA PLANTAGO, L.—The three white or reddish petals
are yellow at the base, and expand to form a disk about 10 mm.
in diameter.

The chief visitors are Syrphidz. They alight sometimes in
the middle of a flower, in which case the insect’s belly comes in
contact with the stigmas and immediately afterwards with the
anthers; or they alight on one of the petals and creep towards the
pollen or honey, in which case various parts of the insect’s body
come in contact with the anthers, and sometimes also with the
stigmas.

566 THE FERTILISATION OF FLOWERS. [PART III.

Although the possibility of self-fertilisation being effected by
the insect-visitors is by no means excluded, cross-fertilisation is
very much more probable, for when the insect alights in the
middle of the flower cross-fertilisation is inevitable, and even if it
alights on a petal cross-fertilisation is more likely to occur than
self-fertilisation owing to the relative position of the anthers and
the drops of honey.

Fic, 186,—1lisma Plantago, lL.

1.—Flower, seen from above.
2.—Ditto, in side view, after removal of the petals,
a, honey-drops; }, stigma,

The six anthers are directed obliquely upwards and outwards,
and dehisce extrorsely. They stand at a considerable distance
from the stigmas, which project in the middle of the flower and
ripen simultaneously with them, Honey is secreted in twelve
drops by the inner surface of a fleshy ring formed by the coherent

bases of the filaments; one drop is placed opposite to each —

filament, and one in the interspace between each pair (a, 1, 2,

PART III. | THE MECHANISMS OF FLOWERS. 567

Fig. 186). <A fly, starting from a petal, usually applies its
tongue to the honey-drops one by one, and after each it strokes
an anther with its labelle; in so doing it may bring various
parts of its body in contact with the anthers; but, as a rule,
the parts which come in contact with the anthers are not those
which come in contact with the stigmas in the same flower. |

I have not determined whether self-fertilisation takes place in
absence of insects.

Visitors: Diptera—Syrphide: (1) Eristalis sepuleralis, L. ; (2) Syritta
pipiens, L., both ab. ; (3) Ascia podagrica, F., very freq. ; (4) Melanostoma
mellina, L. ; (5) Melithreptus scriptus, L.; all sometimes sucking, sometimes
eating pollen.

Alisma natans, L.—In floods, the flowers remain closed below
the surface of the water, and fertilise themselves (351).

Orv. VAIADACE 2.

The plants of this order are anemophilous or hydrophilous.

The proterogynous flowers of Zriglochin palustre, L., have been
figured by Axell (17).

The species of Potamogeton are distinctly anemophilous. The
proterogynous flowers of P. perfoliatus, L., have been figured by
Axell (17, p. 38).

Posidonia is supposed by Delpino to be a grass adapted for a
submerged life (178).

Zostera is considered by Delpino to be an Aroid modified for a
submarine existence (178, 11.). The mode of fertilisation of Zostera
marina, L., is described by Clavaud (138) and Engler (223).

Orv. CYPERACEAE.

The plants of this order are throughout anemophilous, but,
like the grasses, they are by no means without occasional insect-
visits. I have very often seen Melanostoma mellina, L., busy on
the anthers of Scirpus palustris; my son Hermann has seen
several specimens of the hive-bee collecting pollen on Carex
hirta, L., and I have watched the same insect doing so on
Carex montana, L.

568 THE FERTILISATION OF FLOWERS. [PART ILI.

‘Orv. GRAMINEL.

This whole order consists of plants with well-marked anemo-
philous flowers. . I have, however, often observed a small fly
(Melanostoma mellina, L.) busy upon the anthers of various grasses
(Anthoxanthum odoratum, Poa annua, Festuca pratensis, Agrostis
alba). Bromus mollis and Brachypodium pinnatun are visited by
beetles (590, I:). Many grasses are proterogynous, ¢.g. Anthoxan-
thum odoratum, Alopecurus pratensis, Nardus stricta (351, p. 19).
Oryza clandestina is PORE ENC for possessing cleistogamie flowers
(759).

Secale cereale-—Anthers and stigmas mature simultaneously.
The flowers expand widely, and the essential organs protrude
freely ; cross-fertilisation can consequently be effected on a very
large scale by the wind (180).?

Triticum vulgare, L._—Anthers and stigmas mature simulta-
neously, but the flowers only expand partially and for about a quarter
of an hour; they then close up permanently. The flower opens
suddenly, scattering all its pollen, about one-third of which remains
within the flower while the other two-thirds are shaken out.
Cross-fertilisation can only be effected by the wind to a much less
extent than in the preceding species, and Delpino has found by
experiment that self-fertilisation leads to the. production of good
seed. The flowering period lasts four days, and since each flower
only expands for a quarter of an hour, a very small fraction of the
flowers are expanded at any one time (180).

Hordeum vulgare.-—The flowers in the two intermediate rows
never expand ; those in the four outer rows behave like the flowers
of wheat (180).

Hordeum distichum.—While in H. vulgare all the flowers are
hermaphiodite, only those in the two central rows are so in
HT. distichum. They also remain closed and fertilise themselves;
but occasionally normal open flowers occur among them, which may
then be cross-fertilised by pollen from the male flowers in the
four outer rows (180).

Hordewm and Cryptostachys have cleistogamic flowers ( 167)

1 Ascherson, Botanische Zeitung, p. 350, 1864.
* Kornicke, in Regel’s Gartenflora, p. 20, 1866.

PART IV.

GENERAL RETROSPECT.

In this section I propose to review the various structural
features of flowers that have already been described in detail, and
to trace their general effect on the life of the plant. If we cannot
discover the causes, we may determine accurately the effects, of any
modification in structure of a flower.

The various characters of entomophilous flowers which affect
the life of the plant may be grouped as follows :—

1. Characters which influence the visits of insects—

a, General attractions for anthophilous insects.
-a. Colour or scent.
8. Honey, pollen, shelter, or other substantial benefit.

b. Increased attractions for certain insects, gained by the
exclusion of others.
a. By colour or scent.
8. By concealment of the honey or pollen.
y. By the time of flowering or the place of growth.

2. Characters which influence fertilisation—

a. Mutual adaptations of pollen and stigma.
b. The insuring of cross-fertilisation in case of insect-
visits, and of self-fertilisation in absence of insects.

1.—a. CHARACTERS INDUCING INSECTS’ VISITS.

a. Effect of Conspicuousness and of Odour,

In the third section of this book, I have discussed so many
cases of closely allied flowers differing in conspicuousness, and
at the same time in abundance of insect-visits and in the chances

570 THE FERTILISATION OF FLOWERS. [PART Ly.

of cross- or self-fertilisation, that it will suffice to refer here to a
few instances only. We have instituted comparisons between
similar genera of Umbellifer, between species of the genera
Ranunculus, Geranium, Malva, Polygonum, Cerastium, Epilobium,
Rubus, Veronica, Carduus, and Hieracium, between different forms
of Huphrasia officinalis, Rhinanthus crista-galli, Lysimachia vulgaris,
etc., and in all cases the same result has been obtained ; that, cewteris
paribus, a species of flower is the more visited by insects the
more conspicuous it is; and that when closely allied flowers, alike
in other respects, differ in conspicuousness and also in the degree
to which cross-fertilisation is insured in case of insect-visits and
self-fertilisation prevented in their absence, it is always found that
cross-fertilisation is the more perfectly insured in the more con-
spicuous and therefore more abundantly visited flowers. And on
the other hand, under the same conditions, self-fertilisation is best
insured in those flowers which are least conspicuous, and which
therefore are least visited by insects and least likely to be cross-
fertilised. These three statements are fully proved in the case of
many plants by observations recorded in the foregoing section ;
the proof rests upon sound facts and direct observations and not
in any way on speculation or conjecture.

Let us proceed to examine the last two of these three state-
ments, which deal more closely with the act of fertilisation. The
most important deduction to be drawn from them is, that in
general anthophilous insects are not limited by hereditary instinct
to certain flowers, but that they wander about getting their food
on whatever flowers they find it. For if each insect had its own
species of flower as most caterpillars have their own particular
food plant, the abundance of insect-visits to the plant would not
depend at all upon its conspicuousness.

In isolated cases we may find a particular insect confining its
visits exclusively or almost exclusively to a particular flower. I
give the following instances from my own observations. I have
found Andrena florea only on Bryonia dioica, and A. halictoides
only in flowers of Campanula: Andrena Hattorfiana confines its
visits almost entirely to Scabiosa arvensis, Cilissa melanura to
Lythrum Salicaria, Macropis labiata to Lysimachia vulgaris, Osmia
adunca and O, cementaria to Echium. But these insects do not form
1 per cent. of all the species that I have observed, and even
of these cases the restriction is only complete in two.

I have already cited numerous instances of insects seeking
honey in flowers which contain none or which conceal it beyond

PART IY. | GENERAL RETROSPECT. 571

their reach. For instance, butterflies may be seen on the honey-
less flowers of Hypericum perforatum, applying their tongues
to the base of the flower without either finding honey or piercing
succulent tissue; the hive-bee tries in vain to reach the honey
of Iris Pseudacorus, and Rhingia to reach the honey of Dianthus
deltoides and Lamium maculatum. Bombus terrestris tries vainly
to reach the honey of Aquwilegia vulgaris, Primula elatior, Vicia
Faba, ete., in the legitimate way, but finally bites a hole and steals
the honey; various small insects (Meligethes, Andrena parvula,
Spilogaster semicinerea) visit the flowers of Cypripedium, but find
no food and, being unable to escape, are starved to death. I
think I have given enough similar instances in foregoing pages
to prove beyond doubt that anthophilous insects are not guided
by hereditary instinct to particular flowers.

Another class of facts shows clearly that those insects whose
bodily organisation is least adapted for a floral diet, are also least
ingenious and skilful in seeking and obtaining their food; so that

anthophilous insects intelligence seems to advance pari passu
with structural adaptation. This statement is fully proved by the
insect lists given in the sequel. The following examples may serve
to illustrate the point at present. Coccinella septempunctata, which
is not adapted at all for a floral diet, behaves so awkwardly on
flowers of Lrodiwm cicutarium that it generally loses its hold and
often falls to the ground ; and many attempts fail to make it more
skilful. Sarcophaga carnaria seeks honey diligently on flowers of
Polygonum Bistorta, but it usually misses its aim in trying to in-
sert its proboscis into the flowers; Andrena albicans at first is
equally awkward, but gradually becomes more skilful and learns
to insert its proboscis with greater accuracy. The hive-bee never

fails in any case to insert its proboscis accurately.
_ Since we have found that structural adaptation and intelligence
advance together, it is easy to understand the fact that short-
lipped insects, little or not at all specialised for a floral diet, can
usually only find fully exposed honey, such as Listera, Parnassia,
Cornus, and Umbelliferze afford; honey still easily accessible but
not directly visible to them is passed by. It is also quite in-
telligible that the more specialised visitors visit those flowers most
diligently which supply them with most booty; for instance, bees
furnished with abdominal collecting-brushes visit chiefly flowers
fitted to apply pollen to their ventral surfaces ; long-tongued bees
visit chiefly flowers with deep honey-receptacles, whose honey is
inaccessible to the great mass of insects; and hawk-moths, which

572 THE FERTILISATLON OF FLOWERS. [PART 1Y,

surpass all other insects in length of tongue, visit flowers whose
honey is accessible to them alone.

We find that the above-mentioned insects often resort, to a
certain small extent, to flowers less productive than those that
they usually frequent. It is rare for a plant which produces
numerous flowers and much honey or pollen to continue so
abundant for the whole period that an insect is on the wing that
that insect can confine its visits to it alone. In such cases it is
probable that the acquired habit is transmitted instinctively from
one generation to another.

The study of particular species of insects confirms the con-
clusion based on observation of the more conspicuous flowers,
that in general anthophilous insects are not confined by hereditary
instinct to certain flowers, but fly about seeking their food on
whatever flowers they can find it. And hence the circumstance,
already insisted on, that a flower receives the more visits the more
conspicuous it is, becomes readily intelligible. It is also clear how
natural selection must have seized upon and perpetuated all
characters tending to greater conspicuousness. And thus we may
explain all such phenomena as the development of various colours
in flowers, the enlargement and increased prominence of the
coloured surfaces, the association of many flowers together, the
division of labour in such associations between reproductive and
merely attractive members of the community, the appearance of
the flowers before the leaves in Salix, Cornus mascula, ete., and
many other similar phenomena.

Effect of Odour.

The effect of various perfumes in attracting insects is as manifest
as the effect of conspicuousness ; and observation shows that strong
scent is an even more powerful lure than bright colours. The
richly scented flowers of Convolvulus arvensis are far more
abundantly visited than the larger and more conspicuous but
scentless flowers of C. sepiwm; the sweet-scented Violet is much
more visited than the large, brightly coloured, but scentless
Pansy; the small, insignificant, but strongly perfumed flowers of
Lepidium sativum surpass in the abundance of their visitors the
other more conspicuous but scentless Crucifers,

B.—The Effect of Food Supply.

Every plant supplies in its pollen a nitrogenous food which is
readily made use of by many insects, and when once found leads

PART IY. | GENERAL RETROSPECT. 573

to repeated visits. Hence even well-marked anemophilous flowers
are often visited by insects.*

This fact is of special importance in explaining the origin of
entomophilous flowers. For the fact that the lowest and most
primitive Phanerogams are anemophilous forces us to suppose
that all entomophilous plants have sprung originally from anemo-
philous ; that the first adaptations to insect-visits were attained in

. flowers adapted for wind-fertilisation; and that wind-fertilised

flowers, then as now, received visits from insects. In comparatively
few entomophilous flowers is the amount of pollen required by the
plant itself the sole attraction for insects. The great majority
either produce a large excess of pollen or else secrete honey. The
fact that many plants? secrete honey even outside their flowers,
in which case it does not influence fertilisation, renders it probable
that the mere excretion of honey is beneficial, and may have begun
before all adaptations to insect-visits. Whether the excretion
of honey began before or after the first adaptations to insect-
visits, honey is now the most powerful attraction for insects. If
we compare the insect-visits of Genista and Lotus, of Helianthemum
vulgare and Ranunculus acris, R. repens, or R. bulbosus, of Spircea
jfilipendula or S. Ulmaria with 8S. salieifolia, S. ulmifolia, or
S. sorbifolia, we perceive how much more abundant visits (ceteris
paribus) a flower which contains honey receives than a similar
flower which does not, and how much more various are the
insect-visitors if the honey is-easily accessible.

A third food material which leads insects to repeated visits
is sap included within succulent tissues, Darwin’s observations
and my own have shown beyond the possibility of doubt that the
inner membrane of the spur of our native Orchises is pierced by
insect-visitors. I have shown that the same is probably true
of Cytisus Laburnum, and Erythrea Centaurium. The circum-
stance that many flies (Hmpidw, Conopidw, Bombylide), as well as
the more specialised bees and Lepidoptera, are provided with a
boring apparatus at the tip of their proboscides, indicates, that

_ this boring for sap is much more usual among insects than was

formerly supposed. From the comparatively few visits which our
Orchises receive it would appear that sap included within a tissue
is less attractive to insects than free honey.
Anthers, filaments, petals, carpels, in short all the more delicate
1 See Poteriwm, p. 236; Artemisia, p. 333; Cupulifere, p. 523; Cyperaceer,

Graminee, p. 567.
Cf. Vandine and Fpidendrine, p. 528.

574 THE FERTILISATION OF FLOWERS. [PART LY.

tissues of the flower are devoured by some insects, especially
beetles. But this cannot be considered of advantage to the plant.

In many Orchids fleshy processes of the labellum are devoured
by insects ; in Polystachya (Malaxidee) the labellum becomes filled
with loose cells on which insects feed ; but we have no accurate
observations as to the value of these attractions.

The shelter which many flowers afford from rain and-wind is
in many cases a powerful attraction. For instance, the males of
many bees pass the night within flowers of Campanula or take
shelter there from rain; and many small Diptera resort for shelter
to the flowers of Arwm ‘and Aristolochia,

b.—THE EXCLUSION OF CERTAIN INSECTS, AND CONSEQUENT
INCREASED ATTRACTION OF OTHERS.

While, on the one hand, it is of advantage for flowers to be
visited by the utmost possible variety of insects, since the like-
lihood of cross-fertilisation increases with the number of visitors,
yet, on the other hand, the attraction of all kinds of insects has
several disadvantages. For many visitors are positively hurtful,
as, for instance, voracious beetles, which may devour the repro-
ductive elements of the flower; and each class of insects will be
the less attracted the more the store of food is removed by others ;
easily accessible honey is therefore the least likely to attract the
most diligent, long-tongued insects. Besides, easily accessible
honey and pollen are also the most liable to be spoilt by rain. So
exclusion of certain insects may be advantageous to the plant,
if thereby injurious insects are excluded, if certain other insects
are stimulated to more diligent visits, or, lastly, if the honey and
pollen are sheltered from rain. The great majority of flowers
possess contrivances for more or less restricting insect-visits.

a.—Limitation of Insect-Visits by Colour and Odour.

The plants that we have discussed furnish only one class of
instances of colour directly limiting insect-visits.

All dull yellow (dirty-yellow, brownish-yellow, yellowish-white)
flowers (Buplewrum, Anethum, Pastinaca, Rhus Cotinus, Galiwm
Mollugo, Ruta, Neottia, Euonymus, Euphorbia, Adoxa, Alchemilla)
are entirely or almost entirely avoided by beetles; closely allied
white flowers (Umbelliferw, Rubus, Rosa, Galiwm verwm) are visited
by beetles, more or less to their injury; and brightly coloured

PART LY. | GENERAL RETROSPECT. 575

flowers, even though they are scentless and offer no honey, or none
that is accessible (Ranunculus, Helianthemum, Papaver, Genista),
attract beetles in numbers. The only apparent explanation of
these facts is that beetles are only or mainly attracted to flowers
by bright colours. If this explanation is correct, dull-yellow must
be an advantageous colour for plants with freely exposed honey,
protecting them from these injurious guests. And the fact that
dull-yellow colours only occur in flowers with exposed honey lends
support to this view.

Delpino goes much further in regard to the exclusion of insect-
visitors by colour, for he supposes that dull-yellow and purple-
spotted flowers are visited only by Diptera. But my lists show
that almost all the dull-yellow flowers mentioned above are visited
by Hymenoptera, sometimes in great abundance and variety. I
have only investigated two purple-spotted flowers, namely,
Cypripedium Calceolus, whose staminode is speckled with purple,
and Lycopus ewropeus, whose lower lip bears reddish-purple
spots; but both of these are visited chiefly by insects of other
orders.

Indirect limitation of insect-visitors by colour is instanced in
several other cases; but such limitation is of very subsidiary im-
portance, since it is always combined with other more powerful
restrictions. Several bright and pretty flowers, e.g. the species of
Dianthus, attract butterflies in great numbers; even if the
honey was accessible to other insects their visits would be greatly
reduced by the fact of the honey being in great part used up
by the butterflies; but in these cases the honey is placed at
the bottom of a tube so narrow that it is only accessible to the
proboscis of a butterfly.

Many light-coloured flowers, which often grow in shady places,
are inconspicuous by day but conspicuous by night (e.g. Platan-
thera). These are chiefly visited by crepuscular Lepidoptera, but
insects are excluded not so much by the colour as by the
situation of the honey at the base of long, narrow tubes.

Limitation of insect-visits by peculiar odour is probably a more
common phenomenon; but our present knowledge is not suffi-
cient to admit of perfectly definite conclusions. It is obvious that
flowers with a putrid odour are mainly fitted to attract carrion-
flies and meat-flies, but how far their odour repels other insects
has not yet been decided by observation. None of our native
flowers possess odours of this kind. In like manner it is scarcely
possible to doubt that the foul ammoniacal smell of Arum is

576 THE FERTILISATION OF FLOWERS. [PART Iy.

specially attractive to Psychode, which are attracted by other sub-
stances of similar smell; but since the grating of hairs in Arwm
excludes larger insects we cannot be certain that the smell alone
would repel them. Delpino supposed that strong perfumes such
as those of Auta and Anethum are very attractive to flies and are
avoided by other insects, especially by bees. But according to my
observations the same flies which visit Anethum and Ruta also
visit a great variety of other plants, some sweet-scented, others
scentless, in the same abundance and with the same assiduity.
Moreover I have observed the flowers of Anethum visited by six
species of bees and twenty-five other Hymenoptera as well as by
fifteen species of flies, and Ruta visited by three species of bees
and eleven other Hymenoptera in addition to nineteen species of
flies. Delpino’s statement may be more accurate in the case of
Sambucus, but the flowers of that plant are so little visited that
we must not yet conclude that they are not sometimes visited by
pollen-collecting bees. Bees of the genus Prosopis, which them-
selves emit a strong odour, are chiefly found on strong-scented
flowers (Reseda, Lepidium, Ruta, Anethum, Achillea, Matricaria),
and here, as in other cases, the concentration of one class of
visitors may tend to restrict the visits of others.

Sweet, aromatic perfumes, pleasant to our own senses, such as
the scents of Asclepias Cornutr, Rosa Centifolia, Thymus, Lavendula,
are, as Delpino has shown, specially attractive to bees, but in a
less degree to other insects also; and here again we find that

deep situation of the honey is the chief means of restricting -

insect-visits.

B.—Lxclusion of Certain Classes of Insect-Visitors by Paucity or
‘ Concealment of Food Material.

Absence of honey and inaccessibility of the honey or pollen
restrict insect-visits much more effectually than peculiarities in
colour or odour. Honeyless flowers with exserted anthers are
scarcely visited except by pollen-feeding flies (especially Syrphide)
and pollen-collecting bees. Lepidoptera and purely suctorial flies,
(Empide, Conopide, Bombylide) linger at most for a short time on
honeyless flowers to bore succulent tissues for included sap, but
usually fly away after a few seconds to other flowers. Beetles and
sand-wasps devour the pollen of honeyless flowers, but resort far
more abundantly to flowers which furnish them with both pollen
and honey; a few voracious Lamellicorns (Cetonia T'richius)

ae —

ae

partiv.} . GENERAL RETROSPECT. 517

devour the anthers, carpels, or petals of honeyless and honey-
yielding flowers indifferently."

Since honeyless flowers are usually soon abandoned by honey-
seeking insects without being secured from the visits of destructive
beetles and without being visited the more diligently by pollen-
collecting insects, such flowers are cateris paribus at a disad-
vantage compared with those which contain honey. But in most
cases this disadvantage is in some way counteracted, generally by
superabundant production of pollen, in many cases also (Papaver,
Hypericum perforatum) by extreme conspicuousness ; in this latter
case, even such insects as find little or nothing of use to them,
yet search through a few flowers and effect cross-pollination to
a certain extent. But when in honeyless flowers with exposed
anthers, the production of pollen and the conspicuousness of the
flowers remain low, as in Solanum, Hypericum hirsutum, H. quad-
rangulum, H. humifusum, Agrimonia Eupatoria, Anagallis, insect-
visits are so rare that the species is only preserved by the regular
occurrence of self-fertilisation.

Honeyless flowers with concealed anthers will be more
readily understood when we have studied the effects of deeply
placed honey.

The concealment of the honey in a nectary protected by other
parts of the flower, processes, hairs, ete., is of advantage to the
plant in two ways: it protects the honey from rain, and it permits
a larger supply to be accumulated, thus attracting visitors in an
increased degree. With these advantages are connected two
disadvantages: the honey is the less easily discovered the more
it is protected from rain, so that a great host of the less acute
visitors are excluded from it; and the more intelligent visitors,
which are able to detect it, cannot obtain it so quickly as if
it were more exposed, so that the work of fertilisation goes on
more slowly. Both of these disadvantages can be diminished by
special contrivances, and even turned into advantages. For ex-
clusion of the multitude of less intelligent, short-lipped visitors is

1 The honeyless flowers with freely exposed anthers which I have most carefully
examined are Clematis recta, Thalictrum aquilegifolium, T. flavum, Anemone
nemorosa, Papaver Rheas, Chelidonium majus, Helianthemum vulgare, Hypericum
perforatum, Agrimonia Eupatoria, Spirea Ulmaria, S. Filipendula, and S. Aruncus.
On these twelve plants I noted 145 distinct insect-visitors. I saw 40 bees collecting
pollen, 6 feeding on pollen, and 4 boring the tissues of the flower for sap ; 2 other
Hymenoptera feeding on pollen, 2 intent on capturing flies, and 4 apparently seeking
in yain for honey ; 57 Syrphide feeding on pollen ; 5 Muscide feeding on pollen ;
2 Bombylii boring for sap ; 3 Diptera apparently seeking vainly for honey ; 18 beetles

devouring pollen and anthers, and sometimes carpels and petals; 2 Lepidoptera
seeking in vain for honey.

| ae

578 THE FERTILISATION OF FLOWERS. [PART lv.

only injurious so long as more specialised visitors are not abundant.
enough to accomplish all the work of fertilisation ; but as soon as
the development of special structures, to contain and to protect
the honey, permits a larger accumulation thereof, the number of
long-tongued visitors increases so much as to more than com-
pensate for :the falling off in short-lpped visitors. Delay in
the work of fertilisation, owing to concealment of the honey, is
diminished by a great variety of contrivances, and sometimes
entirely removed; the disadvantage that honey sheltered from
rain is not directly visible, is alleviated by pathfinders (coloured
spots or lines), which point towards the honey and enable the
more intelligent visitors to find it in a moment; delay in obtain-
ing deeply placed honey is lessened by the development of
convenient standing-places, of apertures specially fitted for the
insect’s head or proboscis (Labiates, Echiwm, etc.), and by the
grouping of many flowers in close association, so as to permit
rapid passage from flower to flower (Thymus, Mentha, Jasione).
Finally, in Scabiose and Composite, we see how, by means of
exserted reproductive organs and dichogamy, fertilisation en masse
is rendered not incompatible with concealment of the honey.

In the account that I have just given of the evolution of
flowers with more or less deeply placed honey, I have stated that,
in the first place, the advantages which led to such development
were the protection of the honey from ‘rain, and the possibility of
accumulating a large store; and that the exclusion of short-lipped
insects was an advantage obtained indirectly. It may be sug-
gested that possibly this statement should be reversed. But since
the long proboscides of anthophilous insects and the long tubes of
entomophilous flowers have been developed in mutual adaptation,
and have advanced together to greater and greater perfection, we
must suppose that the first honey-yielding flowers exposed their
honey on flat surfaces, and that the first flower-visiting insects
were only furnished with organs capable of licking up fully ex-
posed honey. Under these circumstances elongation of the
proboscis would be of no advantage to any insect so long as
there was only freely exposed honey to lick; but shelter from rain
and increased room for accumulating honey would be beneficial
to the plant even before insects became divided into short-tongued
and long-tongued. Therefore it is certain that the commencing
evolution of structures to store and protect honey preceded the
elongation of insects’ tongues. It was not until honey-receptacles
and a more copious secretion of honey had been attained in certain

"os ae

PART Iv. | GENERAL RETROSPECT. : 579

flowers, that it became possible for long-proboscised varieties of
entomophilous insects to vanquish their short-lipped relatives in
the struggle for existence. This tendency of natural selection
must have taken effect the more certainly, in each class of insects,
the more the insects were dependent on a floral diet.

To give a clear view of the effect of simple concealment of the honey in
flowers with exposed anthers, I have tabulated the visitors of certain groups of
flowers in which the honey is fully exposed, others in which it is more deeply
situated but still visible, and others again, in which it is quite concealed. The
following is a summary of the result :—

(a) On the twenty-five Umbellifere treated in detail in Part III., whose
flowers contain honey freely exposed in a smooth, adherent layer, I have
observed 757 distinct insect-visits ; that is to say, an average of 30 to each
species.

(6) On thirty-eight species of flowers whose honey is still visible, but is
placed more or less deeply at the base of a regular flower, and accumulates in
somewhat greater quantity (Crucifere, Nos. 27—41; Polygonum, Nos. 369—
374; Alsinea, Nos. 60—67; Rosacew, Nos. 128, 133, 135, 150--153), I
have observed 582 distinct insect-visits, or on an average 15 to 16 to each
species.

(c) On twenty-seven species of flowers whose honey is not directly visible
but is yet accessible to the most short-lipped insects (Geraniacew, Nos. 76—83 ;
(Malva, Nos. 69—72; Epilobium, No. 166; Campanula, Nos. 277—282 ;
Jasione, No, 283; Ranunculus, Nos. 6—10) I have observed 384 distinct
insect-visits, or an average of 13 to 14 to each species.

If we classify these visits according to the classes to which the insects belong,
and subdivide these classes, when necessary, according to the lengths of the
insects’ proboscides, we find the following number per thousand visits, for each
of the above-mentioned group of flowers :—

(1) Orthoptera, Neuroptera, and Hemiptera: (a) 12; (b) 3; (ec) 3.
(2) Coleoptera: (a) 84; (b) 168; (c) 76.
(3) Long-tongued Diptera: (a) 84; (b) 167 ; (ec) 78.
Bombylius, Empis, and Conopide: (a) 15; (b) 40; (c) 26.
Eristalis, Helophilus, and Volucella: (a) 69; (b) 105; (c) 36.
Rhingia: (a) 0; (6) 22; (c) 16.
(4) Short-tongued Diptera: (a) 289 ; (b) 250; (c) 180.
(5) Apide: (a) 127; (b) 292; (c) 524.

Prosopis : (a) 25; (b) 143 (ce) 42.
Sphecodes, Andrena, and Halictus : (a) 86; (b) 175; (ce) 250.
Other bees with moderately long tongues: (a) 15; (b) 70; (ec) 180.
Bombus and Anthophora: (a) 1; (0) 33; (c) 52.

(6) Other Hymenoptera : (a) 332; (b) 69; (c) 91.
(7) Lepidoptera: (a) 8; (b) 41; (e) 44.
(8) Thrips: (a) 0; (b) 10; (ce) 5.

However imperfect my lists may be, and however small the value that we
can give to particular numbers, this table shows clearly that with increased

PP 2

580 THE FERTILISATION OF FLOWERS. [PART LY.

concealment of the honey the number of short-lipped visitors diminishes and
the number of long-tongued visitors increases ; and that, in the end, bees far
outnumber beetles, wasps, and short-lipped flies.

The tubes in which various flowers conceal their honey vary in
length between very wide limits—from scarcely 1 mm. to about
30 mm. in our native flowers. In the shortest forms, ¢.g. species of
Veronica, the tube with its interior circle of hairs acts just like
the structures which shelter the honey in Malva and Geranium.
The further increase of length in such tubes depends entirely
upon the advantage to the flower of excluding certain groups
of insects in order to induce more diligent visits on the part
of others.

If increase in length of the proboscis proceeded pari passu with
increased need of food and increased diligence, and therefore also
with increased usefulness in the work of fertilisation, the various
adaptations connected with it would be comparatively easy to
understand. But this is by no means the case. The entomophilous
insects which require most food and are most diligent, and there-
fore the most efficient fertilisers, are unquestionably the Bees,
since they feed not only themselves but their young solely on
substances derived from flowers; but the circumstance that they
have to use their mouth-parts to build the cells for their young
has set definite limits to the adaptation of these parts for obtaining
deeply placed honey, while such limits do not exist for Lepidoptera.
Accordingly, though bees have far surpassed flies in the length
of their tongue (our longest-tongued Diptera, Bombylius and
fthingia, have proboscides 10 to 12 mm. long, while Anthophora
prlipes and Bombus hortorum have proboscides over 20 mm. long),
they are far outstripped by many Lepidoptera (Sphinx ligustri,
37 to 42 mm., S. Convolvuli, 65 to 80 mm.).

Though, owing to the special diligence of bees, most tubular
flowers have elongated their tubes so as to exclude the more
short-lipped insects and to admit a wider or narrower circle of
the more specialised bees, and though many of these flowers
are shown by other structural adaptations to be specially fitted
for bees, yet butterflies have access to the honey of all these
flowers, and sometimes act as subsidiary fertilising agents though
often they are quite useless to the plant.

Most of our native flowers with hidden honey have at the same time their
pollen more or less deeply situated, or else differ in other important relations,
and are therefore not fitted to show clearly the effect of increased concealment

8. +? => eae

PART IV. | GENERAL RETROSPECT. 581

of the honey, The Composite, however, furnish several series of forms well
fitted to demonstrate this point. Omitting some aberrant forms, the honey is
on the whole least deeply situated in the Senecionida, more deeply placed in the
Cichoriacew, and most deeply in the Cynaree, On (a) ten Seneciunide (Nos.
216, 222, 224, 226, 227, 228, 232, 233, 236, 237), I have observed 335 different
insect-visits, or an average of 33°5 to each species ; on (b) fifteen Cichoriacee
(Nos. 259, 261—273, 275), 356 distinct visits, or an average of 23 to 24 ;
and on (c) ten Cynarew (Nos. 240, 241, 244, 245, 249, 252, 254, 256, 257, 258),
189, or an average of 18 to 19. The following table is similar to the preceding
one, and shows the proportionate number of visits paid by each group of
insects, reckoning the total number of visits observed at 1,000.

(1) Specially long-tongued bees, Bombus and Anthophora : (a) 15 ; (b) 48;
(c) 211.
_ (2) Bees with abdominal collecting-brushes (and long proboscides) : (a) 27 ;
(b) 48; (c) 181.

(3) Other bees with long or moderately long proboscides : (a) 42 ; (b) 126;
(c) 85.

(4) Sphecodes, Andrena, and Halictus (proboscides moderately long) : (a)
167 ; (b) 399; (ec) 196.

(5) Prosopis and Oolletes (short-tongued) : (a) 30; (b) 8; (c) 5.

(6) Other Hymenoptera (mostly short-lipped) : (a) 137 ; (b) 17; (c) 35.

(7) Long-tongued, purely suctorial Diptera (Bombylius, Empis, Conopide) ;
(a) 42; (b) 42; (c) 35.

(8) Rhingia: (a) 3; (b) 3; (ce) 10.

(9) Syrphide with shorter tongues than Rhingia (Eristalis, Helophilus,
Volucella) : (a) 92; (b) 84; (e) 55. :

(10) Short-tongued Diptera: (a) 242; (b) 121; (ce) 10.

(11) Lepidoptera: (a) 80; (b) 67; (c) 171.

(12) Coleoptera : (a) 116; (b) 34; (c) 465.

(13) Hemiptera and Panorpa: (a) 9; (b) 3; 10.

This table proves clearly that in Composite as the honey becomes more
deeply placed the visits of the more highly specialised bees increase, while, in
spite of the exposed situation of the pollen, the visits of flies fall off. This is
true of the number of species of visitors ; but if it were possible to record the
number of visits paid by each species, the preponderating influence of bees
would be still more apparent. From these first stages in elongation of the
corolla-tube and increase of bees’ visits by exclusion of short-lipped insects, we
pass by the most gradual steps to the exceedingly long tubes whose honey is
monopolised by a smaller and smaller number of bees, At the top of the
series stand flowers whose tubes are 16 to 20 mm. long, and whose honey is only
accessible to a few species of Bombus and Anthophora (Aquilegia, Delyhinium,
Pedicularis, Lamium maculatum, etc.).

It would not be possible without many more observations to classify our
flowers in a long series of groups, each one restricted toa smaller circle of bees,
The length of the tube is not of itself a measure of the proboscis necessary to
reach the honey ; for often the mouth of the flower is widened to admit the
insect’s head or even part of its body, and further the honey often accumulates
to a considerable depth in the tube. Such conditions are illustrated in many
Silenee, Boraginee, Scrophulariacee, Ericacee, etc.

582 THE FERTILISATION OF FLOWERS. [PART Iv.

Although, from the peculiar industry of bees, elongation of the
corolla-tube is to be ascribed to their influence in the great
majority of cases, this is not the case always. The flowers of
Scrophularia and Symphoricarpus are just of the right size to admit
a wasp’s head ; and wasps are attracted in such numbers to these
flowers by the abundant honey that the visits of other insects to
which the honey is equally accessible are greatly diminished.

Other flowers conceal their honey in tubes so long and narrow
that it is only accessible to Lepidoptera. Owing to the small
supply of food needed by Lepidoptera and their inferior industry,
such a condition could only prove advantageous to a comparatively
small number of plants. The following native flowers are adapted
for Lepidoptera :—DiuRNAL FLOWERS: Anacamptis pyramidalis,
species of Dianthus, Lychnis Githago; NocruRNAL FLOWERS:
Gymnadenia conopsea, species of Platanthera, Saponaria officinalis,
Lychnis vespertina, Lonicera Caprifolium and L. Perielymenum.
Of these, the diurnal flowers exclude bees (and still more, other
insects) by the narrowness of their tubes, and the nocturnal species
by their length also.

In many flowers the mouth of the corolla closes, and can be
forced open by bees but not by flies; the visits of the former are
therefore increased and of the latter diminished. I may merely
refer to the closed mouth of the corolla in Antirrhinum and
Linaria, to the closed entrance to the nectary in Borago, Symphytum
and Salvia, and to the close-shut flowers of Lathyrus pratensis,
Vicia sepium, Pisum sativum, and many other Papilionaceze. In
many cases such conditions fail to exclude the thin tongues of
Lepidoptera.

Effect of Concealment of the Pollen.

Freely exposed pollen is liable to be spoilt by rain, devoured by
flies and beetles, or carried away by pollen-collecting bees. Of
these contingencies the first is wholly an evil, the second becomes
advantageous if any considerable amount of pollen is conveyed to
the stigma, and the third almost always results in fertilisation and
is therefore altogether advantageous. Concealment of the pollen,
as of the honey, must have been brought about in the first place as
a protection from rain. Since with this advantage comes the
disadvantage that the sheltered pollen is less likely to be touched
and placed on the stigma by insect-visitors, concealment of the.
stamens has not become general. Many, even of those flowers
whose honey is deeply placed and attainable by a limited group

PART LY. | GENERAL RETROSPECT, 583

of visitors, expose their pollen (but in that case their stigmas also)
to short-lipped insects, which then act as subsidiary fertilising
agents (cf. Composite, Silenee, A’sculus, Echiwm, Gnothera, Lonicera,
etc.). And all flowers with hidden anthers have only been able to
shelter their pollen from rain in so far as they have developed
other adaptations for particular visitors, which compensate for the
less general access of pollen-carrying insects. For this reason,
flowers with hidden pollen afford us the most conspicuous ex-
amples of adaptation in form and in dimensions to a more or
less narrow circle of visitors (cf. Orchidew, Iris, Papilionacee, some
Boraginee, Labiate, Scrophulariacee, Apocynee, Ericacew, etc.).
These adaptations are always directly concerned in insuring self-
fertilisation, and therefore fall to be considered in a future section.
But the more perfectly flowers are adapted for cross-fertilisation
by particular insects, the more unlikely does it become that other
insects visiting the flowers will effect cross-fertilisation, and the more
will such visits of other insects be useless or injurious to the plant.
So concealment of the pollen is useful (to a subsidiary degree) in
limiting insect-visits, and this effect has now to be considered.

Concealment of the pollen in a cone of apposed anthers
(Viola, Borago, Symphytum) hinders it from being devoured by
flies and beetles, and renders it more difficult for bees to collect it;
while honey-seeking bees cannot reach the honey without causing
the cone to open and shed its pollen on them.

Concealment of the anthers within open tubes (I/yosctis, Vinca,
Syringa, etc.) renders it more difficult for beetles to devour the
pollen, and for bees to collect it; but if the tube is wide enough
-(Syringa), the more highly developed proboscides of certain Syrphide
can enter and obtain the pollen, while narrower tubes (J/yosotis,
Vinca) prevent all Diptera from feeding on the pollen, and only
permit their visitors to obtain honey. When the tube containing
the stamens is closed (Anchusa, Linaria, Antirrhinum), all insects
except bees, Lepidoptera, and some very minute intruders are shut
out both from the honey and from the pollen. Pendulous flowers
with included stamens and not too wide tubes protect their honey
from removal by flies (Asparagus, Convallaria) or by other insects
also (Erica, Vaccinium) ; such flowers are therefore visited mainly
or exclusively by honey-seeking insects. A vaulted structure
sheltering the anthers from rain (/ris, most Labiates), does not
“prevent, but to a great extent restricts, the theft of pollen by
insects ; beetles are quite unable to obtain pollen so concealed,
only a few of the more intelligent flies, especially Rhingia, and

584 THE FERTILISATION OF FLOWERS. [PART IY.

rather more numerous bees can do so. The pollen is most com-
pletely protected in those flowers whose stamens are completely
shut up within the corolla (Fumariaceew, Papilionacee, Rhinanthus,
Melampyrum, Pedicularis, Salwia), or whose pollen is united in
masses and enclosed in pouches (Asclepiadew, Orchidew). These
plants are no longer able to have their pollen transported by
miscellaneous insects, but they have developed adaptations of the
most perfect kind for cross-fertilisation by certain special insects.

The mechanism is so perfect and so effectual in these flowers
that cross-fertilisation is thoroughly insured, though some of them
offer only pollen to their visitors (Genista, Sairothanwinns) others
pollen and sap (Cytisus), others sap only (Orchis).

The contrivances that we have just reviewed give to two
divisions of anthophilous insects exclusive or almost exclusive
access to the food materials contained in certain flowers ; namely,
in most cases to bees, which, however, must usually share their
honey with the Lepidoptera; and in relatively few cases to
Lepidoptera, when, if the pollen lies exposed, flies may devour
it and bees collect it, playing a subsidiary part in the work of
fertilisation. But certain small Diptera which resort to small dark
cavities have a much more complete monopoly of those flowers
which furnish them with such temporary abodes, and which have
become adapted for cross-fertilisation by them (Aristolochia
Clematitis, Arum maculatum); for the narrow entrance usually
excludes all other insects.

Limitation of Insect-visits by Time of Flowering and by Place
of Growth.

It is obvious that every species of flower can only be visited and
fertilised by those insects which occur at the time when the plant
is in flower, and in the stations where it grows. The insect-
visitors of a plant are therefore limited by the season and by the
time of day when it flowers, by its geographical distribution, and
by the nature of its habitat.

We may assume, furthermore, with Delpino (175 A), that the
geographical range of many flowers finds its limit where insects
suitable for their fertilisation begin to fail. But the particular
cases which Delpino adduces to support this view are, in part,
based on insufficient observations.' Our stock of observations is

1 Thus Delpino supposes that the geographical range of Roses is determined by
the occurrence of Cetonie and Glaphyride (175 A, p. 18), and that Lpilobiwm and

Mvyosotis are exclusively fertilised by bees (p. 19). My lists contradict both of these
assumptions,

PART IY. | GENERAL RETROSPECT. ‘585

as yet also insufficient to show us how the circle of visitors to
any particular plant is determined by the time of flowering, the
nature of the locality, the competition of other flowers, and the
peculiarities of structure in the flower itself.

It is obvious that flowers which only expand at night are
thereby protected from the visits of all merely diurnal insects,
but among our native flowers we have scarcely a distinct example
of this condition. Of the flowers mentioned above as adapted for
hawk-moths and nocturnal Lepidoptera, Lychnis vespertina expands
in the evening, without, however, being completely closed by day ;
while the others exclude diurnal insects from their honey only by
their long, narrow tubes, and specially attract hawk-moths and
night-flying Lepidoptera by their colour, and by exhaling their
odour most powerfully at night.

2. STRUCTURAL CHARACTERS WHICH AID IN FERTILISATION.

Adaptive Modifications of the Pollen and Stigma.

All the characters of flowers so far discussed can only be of
advantage to the plant in so much as they contribute indirectly to
the conveyance of pollen by insect-visitors to the stigmas of other
flowers. But this result is only possible if the pollen is of such a
nature as to adhere to the insect, and if the stigma is fitted to
remove it from the insect in turn.

While in anemophilous plants the pollen consists very generally
of loose, smooth, and easily scattered grains, in entomophilous
flowers it presents a great variety of characters, all such as to enable
it to adhere to the bodies of insect-visitors; and in all cases the
nature of the stigma stands in the closest relation to the nature
of the pollen, and the stigma is always fitted for attaching the
pollen to itself by a viscid surface or by projecting papille.
In flowers furnished with a contrivance fur scattering their pollen
(several Scrophulariacee, Hvricacew, etc.) the pollen is usually
smooth and loose as in anemophilous plants; but it is inclosed in
receptacles from which it is dislodged by a touch of the. insect,
and it is often directed in its fall by special hairs. In Syringa
and Symphoricarpus the insect’s head or proboscis is first moistened
with honey, to which the pollen then adheres; in Vinca and
Polygala viscid matter is secreted by the stigma, and in Bryonia,
Marrubiwm, Sideritis, etc., by spherical cells of the anthers, and
fulfils the same function. In the great majority of cases, that is to

586 THE FERTILISATION OF FLOWERS. [PART IY.

say in all generally accessible flowers, the pollen is rough or viscid,
so that it adheres readily to the usually hairy surfaces of insect-
visitors. In Cypripedium it forms a sticky mass, which adheres to
the insect as it forces its way underneath, and which is afterwards
removed by the rough stigmatic surface of the next flower. In
Orchis it coheres in little packets which are united into “ pollinia ”
or “pollen-masses” by elastic threads, and the whole pollen-
mass attaches itself by a special cement to the insect-visitor;
the stigma is sticky enough to cause the little packets of pollen
which come in contact with it to adhere firmly, so that as the
insect moves away the elastic threads are broken through. In
Asclepias all the pollen-grains in an anther-lobe cohere to form
a flattened mass, which becomes attached by its “corpusculum ”
to an insect’s claw, and is inserted through a narrow slit into
the stigmatic chamber of another flower, and is torn away and
left there.

The size of the pollen-grains also varies in relation to the
length of the style which the po!len-tubes must traverse, as is seen
in the varying size of pollen-grains from the different whorls of
anthers in dimorphic and trimorphic plants (cf. Lythrum),.

Characters which insure Cross-Fertilisation in case of Insect- Visits
and Self-Fertilisation in Absence of Insects.

If the adaptations of flowers to insect-visits are really due to
the cross-fertilisation induced by the visitors, all characters which
render cross-fertilisation inevitable in case of insect-visits, and
which render self-fertilisation impossible, must be of special advan-
tage to the plant ; but only so far as insect-visits occur in sufficient
abundance to insure cross-fertilisation. If this condition is not
regularly fulfilled, it is obviously much better for the plant
to have the power of reproducing itself by self-fertilisation
while leaving only a possibility of cross-fertilisation in case of
insect-visits than to be cross-fertilised with absolute certainty when
insect-visits occur, but to be not fertilised at all in absence of
insects. This is the simple explanation of the law already laid
down, that “When closely-allied flowers, alike in other respects
in structure, differ in the abundance of their insect-visits, and at
the same time in the degree to which cross-fertilisation is insured
in case of insect-visits and self-fertilisation in absence of insects,
then under otherwise similar conditions those flowers which are
most visited are those in which cross-fertilisation is best insured, and

EEE Ee —s

PART IV. | GENERAL RETROSPECT. 587

those which are least visited are those in which self-fertilisation
is best insured.!

The comparative merits of cross-fertilisation and self-fertilisation
can only be rightly considered when the actual insect-visits that the
plant receives are taken into account ; and only the utter neglect
of this precaution can explain how Hildebrand and Axell came
to directly opposite estimates of the value of the two modes of
fertilisation. For Hildebrand in his Geschlechtervertheilung ar-
ranges the mechanisms of flowers according as they hinder self-
fertilisation, and seems to consider those the most perfect in which
self-fertilisation is least possible; while Axell tries to show that
the highest and most perfect Phanerogams are those which
regularly fertilise themselves.”

Both views are only partially correct ; the truth lies between
them. The law, proved by general considerations in the Introduc-
tion and by many detailed facts in the third section of this book,
that cross-fertilisation is better for a plant than self-fertilisation,
but that self-fertilisation is infinitely better than no fertilisation at
all and consequent sterility, must modify essentially Hildebrand’s
conception of a law of the avoidance of self-fertilisation. And it is
evident at once that Axell’s idea of a single path towards perfection
in the evolution of Phanerogamic flowers is altogether untenable
when we review the insurance of cross- and self-fertilisation in
connection with the insurance of insect-visits.

The oldest Phanerogamic flowers which adapted themselves
for the transport of their pollen by insect-agency certainly pos-
sessed those characters by which insects are mainly attracted—
namely, conspicuousness, perfume, and honey—to so small an
extent that as a rule their insect-visitors were not numerous
enough to insure cross-fertilisation. Under these conditions it
must have been advantageous for the organs of both sexes to be
united within one flower so as to admit the possibility of self-
fertilisation. In accordance with this is the fact that while the
Gymnosperms have diclinic anemophilous flowers, the great
majority of entomophilous Phanerogams are monoclinic.

But as soon as in any entomophilous plant increased conspicu-
ousness, or perfume, or food-supply had so far multiplied insect-
visits that cross-fertilisation took place regularly and the possibility
of self-fertilisation became quite useless, then the possibility of

1 Compare Rhinanthus, Lysimachia, Euphrasia officinalis, Rosa, Rubus, Epilobium,

Geranium, Malva, Polygonum, Stellaria, Cerastium, Veronica, Hieraciwm, Senecio, ete.
2 Cf. ‘Historical Introduction,” pp. 12, 20.

588 THE FERTILISATION OF FLOWERS. [PART IV.

self-fertilisation could be dispensed with, and has actually in very
many cases been lost. Such a result has taken place in the most
diverse ways, sometimes by dichogamy, sometimes by the position
of the parts in the flower, sometimes by reversion to the diclinic
condition. Asparagus officinalis, Ribes alpinum, Rhus Cotinus,
Lychnis vespertina, &c., are undoubted instances of plants which
have reverted or are reverting from the hermaphrodite to the
diclinic condition.

So when insect-visits were comparatively few it was a step
towards perfection for entomophilous diclinic plants to become
monoclinic ; but when cross-fertilisation was insured by sufficient
insect-visits the reverse transition was advantageous. So is it
with all other characters which insure cross-fertilisation or self-
fertilisation. Dichogamy is so general a feature throughout
whole genera and orders, that it is scarcely possible to doubt that
it has been inherited as an advantageous character from the
common ancestors of these genera or orders; but the least con-
spicuous and least visited species in these groups have reverted to
self-fertilisation, and in their case this reversed progress has been
a step towards perfection (cf. Senecio vulgaris, Malva rotundifolia,
the smaller species of Geranium, Stellaria media, etc.). In
Rhinanthus crista-galli_ cross-fertilisation in the event of sufficient
insect-visits 1s insured by the distance of the stigma and anthers
from one another, and the style is elongated so that its stigma
must be touched by insect-visitors; but in the less conspicuous
variety the tip of the style curves backwards so far that self-
fertilisation ensues without fail. It is needless to cite more of
the instances already discussed, in which little-visited varieties,
species, or genera fertilise themselves regularly, while closely-allied
forms, more abundantly visited, have been able to dispense with
the possibility of spontaneous self-fertilisation.

_ In my opinion, if we must describe in general terms the grades
of perfection in floral mechanisms, we can only call those specially
perfect which fulfil their purpose in the life of the plant specially
well; that is to say, which under existing conditions insure the
sexual reproduction of the species with particular success. We
cannot admit that either the insurance of cross-fertilisation in case
of insect-visits, or the unfailing occurrence of self-pollination, is in
itself a measure of perfection in the mechanism of a flower; for
both among plants which regularly pollinate themselves and
among those in which spontaneous self-pollination is impossible
we find numerous species which prove by their great abundance

ee

PART IV. | GENERAL RETROSPECT, “ 589

how perfect is their structure. Senecio vulgaris, Veronica
hederefolia, Stellaria media, Lamium purpureum are examples of
the one condition, and Pedicularis silvatica, Malva silvestris, and
Echium vulgare of the other. It must by no means be supposed
that all floral mechanisms are equal; in many flowers distinct
imperfections have already been pointed out (Posoqueria fragrans,
Faramea, Malva silvestris, Euphrasia Odontites, Geum rivale,
etc.). There are also species which, after abandoning the power of
self-fertilisation, have suffered so from the competition of other
flowers that they obtain very few insect-visits (¢.9., Ophrys
muscifera). Such instances prove still more forcibly that the
uniform perfection which Axell supposes to exist in Nature has
no real existence,

It may be urged that Axell proceeds from a totally different
conception of perfection; for he looks upon every economy of
space, time, and material as a step towards perfection ; and he
must therefore look upon the reversion of monoclinic flowers to
diclhny, or the passage of homogamic flowers to dichogamy, as
retrograde even when those changes are of distinct advantage for
the sexual propagation of the plant. But such a definition of
perfection is unnatural.

But even apart from any definition of perfection in a floral
mechanism, nothing can be more unnatural than to assert that
there is only one course of evolution or only one path towards
perfection in the structure of flowers.

As in regard to conspicuousness, odour, or production and
concealment of food material, so also in favouring or insuring
cross-fertilisation, there is an infinite variety of means to the
end.. In flowers which receive abundant insect-visits cross-fertilisa-
tion has been insured sometimes by reversion to dicliny, sometimes
by dichogamy, sometimes by distant separation of the stigma and
pollen in the flower, sometimes by a special mechanism causing
the pollen to adhere to the insect and afterwards to the stigma of
the next flower. Dichogamy, though usually proterandrous,, is
proterogynous even in many entomophilous flowers (Aristolochia, —
Hwonymus, many Rosacece), in spite of Axell’s statement to the
contrary. ‘The separation in space of the essential organs may
be of the same kind in all the flowers of a species, or the relations
of the parts may be different in different flowers; but in all cases
the relative positions of the parts are closely connected with in-
sects visits. In the former case, when all the flowers are alike,
eross-fertilisation is insured either if the same part of the insect

590 THE FERTILISATION OF FLOWERS. [PART IV.

visitor always comes in contact first with the stigma and after-
wards with the anthers (Anthericum, Convallaria majalis, Lonicera
Caprifolium, many Labiatze, etc.), or if in each flower any part
of the proboscis, body, or head of the insect touches the stigma
while at the same time the opposite side touches the anthers
(Myosotis, Omphalodes, Ribes nigrum, Berberis, Cruciferae, etc.).
When the flowers are not all alike, that is to say in dimorphic
(Primula, Hottonia, Pulmonaria, Polygonum fagopyrum) or tri-
morphic (Lythrwm) plants, cross-fertilisation is insured if the insects
touch the anthers and stigma with different parts of their bodies,
but touch the stigma with that part which touched the anthers in
a previous flower.

The mechanisms for applying pollen to a particular part of the
insect are astonishingly various; from the nature of the case they
can be the more easily attained the more the circle of visitors is
restricted to a few definite forms by concealment of the honey.
As examples of these multitudinous arrangements we may recall
the flowers of Ericaceze, Scrophulariacee, Boraginee, and Galanthus,
in which pollen is sifted on to the insect; the infinite number of
devices in Orchidew ; and the somewhat similar mechanism of
Asclepiadaceze ; the flowers of Papilionaceze, Fumariaces, and
of Lopezia, in all of which the insect involuntarily opens the
pollen-receptacle and dusts itself ventrally with pollen; Salvia,
in which the mechanism is reversed and the insect’s back receives
the pollen; lastly, the simple device of the flexible stamens in
Veronica Chamedrys and Circa.

The mechanisms which have been discussed in this book are
only an infinitesimal fraction of the vast variety that exists. They
arose quite independently and at various times in the various
divisions of those Phanerogams which had become entomophilous
and monoclinic. They have in general become developed only
where increasing conspicuousness and a large supply of food material
attracted so many insects that the capability for self-fertilisation be-
came unnecessary ; on the other hand, where insect-visits remained
few, the power of self-fertilisation (which began with the appearance
of hermaphroditism) was retained. Where cross-fertilisation that

1 The mechanisms for insuring cross-fertilisation in Umbellifere and in Com-
posite have been inherited from the ancestors of the order; those in the various
species of Aquilegia, Delphinium, Linaria, and Pedicularis, from the ancestor of the
genus ; those in Polygonwm fagopyrum, P. Bistorta, and Lonicera Caprifolium, from
the ancestor of the species ; while the different forms of flowers in Rhinanthus erista-
galli, Veronica spicata, Odontites serotina, -Euphrasia officinalis, and Lysimachia
vulgaris, give us examples of various floral characters being evolved within the bounds
of one and the same species,

PART IY. | GENERAL RETROSPECT. 591

had once been insured becomes uncertain owing to the competition
of other flowers (¢.g. Malva rotundifolia, species of Geranium), or
owing to the unfavourable locality (cf. Lysimaehia nemorum) or
unfavourable weather (cf. Veronica Beccabunga), the mechanisms of
the flowers have in many cases undergone a change such as to
render self-fertilisation again possible ; in a few cases reversion to
anemophily has taken place (Artemisiacer, Zhalictrum). As
examples of the countless ways in which plants revert to self-
fertilisation in default of sufficient insect-visits, I may mention the
following :—In some dichogamic flowers the stigmas curl back upon
the anthers or other parts which still retain some pollen (Stellaria
graminea, Malva rotundifolia, species of Geraniwm, Composite) ;
the stigmas sometimes curl back till they come in the line of fall of
the pollen (Melampyrum pratense) or even place themselves between
the anthers (thinanthus minor); anthers which stand in a ring
round the stigma may, in default of sufficient insect-visits, con-
verge above the stigma, applying their pollen to it (Myosotis,
Lithospermum, Cruciferze); even mechanisms which effect cross-
fertilisation with astonishing precision in case of insect-visits are
not unfrequently transformed so as to render self-fertilisation
inevitable when insect-visits are few (certain Orchidez, Fuma-
riacee, Salvia); or the production of cleistogamic, self-fertilised
flowers may compensate for the loss of the power of self-fertilisation
in the ordinary flowers ( Viola).

Unlike Axell, who brings his book to a conclusion by saying
“ We see thus that the development of mechanisms for fertilisation
in Phanerogams has gone on and still goes on in the same
direction,” + I should say : The dependence of entomophilous flowers
on guests so infinitely various in habits, tastes, and numbers, in
their food and in the means of obtaining it, must have rendered
possible not one but countless paths towards perfection, paths
leading not always forwards but sometimes backwards; and only in
such a way could the infinite variety of existing flowers have
come into existence.

My brother Fritz Miiller has sent me the following instances
of the general principle that whenever in a variable species
selection occurs in a definite way, then that selection, apart from
other relations, will lead to a continued increase of the variation
in the same direction from generation to generation :—

1 *¢ Vi ansa saledes, att utvecklingen i anordningarna for kénens forening hos de
fanerogama vixterna fortgatt och fortgar i nimmda riktning.”—No. 17, p. 95.

592 THE FERTILISATION OF FLOWERS. [PART Iv.

(1) In maize cultivated at Itajahy, the grains stand for the most part in
twelve or fourteen rows, not unfrequently in ten, rarely in eight or sixteen, and
very rarely in eighteen rows. In more than 100 ears which I bought for
sowing in 1867 I found only one of eighteen rows. This ear produced next year
205 ears, among which were twenty-two with eighteen rows, besides one which
had eighteen rows in the upper part and twenty in the lower, and one which
had eighteen at the top, twenty in the middle, and twenty-two at the bottom.
Next year, 1868-69, I had 460 ears obtained from seeds out of ears with eighteen
rows ; and of these 460, 18°2 per cent. bore eighteen rows, 4'4 per cent. bore
twenty, and ‘2 per cent. bore twenty-two. In the following year, among ears
obtained from seed out of ears bearing twenty-two rows, one ear occurred
which bore twenty-six rows.

(2) In an Abutilon from Capivary the normal number of styles isten. A
seedling obtained from a flower with nine styles had, among 100 flowers, two
with seven styles, and twenty-seven with eight ; while in 100 flowers upon the
mother-plant there were only three with eight, and none with seven styles.

“ (3) In Abutilon there occur sometimes, but very rarely in most species,
flowers with six petals.

“ From seed obtained from an hexamerous flower of the hybrid EF’, fertilised
with pollen from a pentamerous flower of the variety /’, a plant was reared
(EFF) which I watched for three weeks (August 17 to September 6, 1869)
counting the petals upon all the flowers that appeared on it. It bore in the
three weeks :—

Flowers with 5 petals. A ; ‘ 145
Ditto MLL lala : : ; . 103
Ditto ee Sith ee : : pies 13

“At the same time I watched another plant descended from pentamerous
parents of the same varieties as those of the former (but obtained by pollen of
the hybrid EF applied to the stigma of the pure species /), It bore in the
three weeks :—

Flowers with 5 petals : : : ; 454
Ditto A MS ; : ’ é 6
Ditto eee i P : , : 0

“The simplest explanation of these facts seems to be, that each species has
the property of varying within a certain amount: crossing of different in-
dividuals so long as no selection is made in a definite direction, suffices to keep
the middle point fairly constant, about which the variations oscillate ; and so
the extremes also remain constant. But if the tendency to vary in either
direction is aided by natural or artificial selection, then our middle point is as
it were shifted to that side and the extremes of oscillation are also shifted
towards the same side.”

Since the first appearance of this work (1873) I have discussed
in a series of essays the question of the Origin of Flowers and the

1 # indicates the Abutilon called Hmbira branca by the Brazilians; F, an
Abutilon from Pocinho (see No. 557); ZF implies the hybrid produced by pollen of
F applied to the stigma of Z.

PART LY. | 3 GENERAL RETROSPECT. 593

gradual attamment of their special. characters. I may now close
this book with a summary of my chief conclusions. The good effect
of cross-fertilisation may be recognised not only in the structure of
insect-fertilised flowers, but also in the water-fertilised and wind-
fertilised plants which preceded them. Even in the lowest aloze we
find cross-fertilisation, to effect which two individuals move towards
each other in the water by means of a cilium. Ina higher grade we
find the two individuals differentiated, one losing its motility, and
increasing in size to form an ovwm, while the other (sperm-cell
or antherozooid) retaining its primitive motile form swims about in
quest of the ovum. - This mode of cross-fertilisation is retained not
only: by all cellular cryptogams (except the Floridee or red sea-
weeds, whose tailless antherozooids are moved passively in the
current) but also by all vascular cryptogams. With the change to
dry localities, where even occasional moisture sufficient for the
migration of the antherozooids is not attainable, the vascular
cryptogams seem to haye developed wind-fertilised _ unisexual
flowers; thus, first the Gymnosperms, and from these afterwards
the Angiosperms have arisen.

Finally from the wind-fertilised Angiosperms, entomophilous
flowers arose, as insects came first accidentally and afterwards
regularly to seek their food on flowers, and as natural selection
fostered and perfected every change which favoured insect-visits
and thereby aided cross-fertilisation. With the transition to
insect-fertilisation caine, on the one hand, great economy of pollen,
but, on the other hand, the uncertainty of insect-visits made it as
a rule necessary that self-fertilisation should remain possible.
Thus, though descended from unisexual (anemophilous) ancestors,
entomophilous flowers are usually hermaphrodite, and are capable
to a great extent of fertilising themselves when insect-visits fail.
But in the course of further development, many of them have so
increased their means of attracting insects (by colour, perfume,
honey, etc.), that the power of spontaneous self-fertilisation has
become superfluous and finally has been lost.

Insects in cross-fertilising flowers endow them with offspring
which in the struggle for existence vanquish those individuals of
the same species which are the offspring of self-fertilisation. The
insects must therefore operate by selection in the same way as do
unscientific cultivators among men, who preserve the most pleasing
or most useful specimens, and reject or neglect the others. In
both cases, selection in course of time brings those variations to
perfection which Serrespond t to the taste or to the needs of the

Q Q

594 THE FERTILISATION OF FLOWERS. [PART Ly,

selective agent. Different groups of insects, according to their
sense of taste or colour, the length of their tongues, their way
of movement and their dexterity, have produced various odours,
colours, and forms of flowers; and insects and flowers have
progressed together towards perfection.

The transition from wind-fertilisation to insect-fertilisation and
the first traces of adaptation to insects, could only be due to
the influence of quite short-lipped insects with feebly developed
colour-sense. The most primitive flowers are therefore for the
most part (except, for instance, Salix) simple, widely open, regular,
devoid of honey or with their honey unconcealed and easily
accessible, and white or yellow in colour (e.g. most Umbellifere and
Alsinee, many Ranunculacece and Rosacec.

The carrion-loving Flies were from the first marked out by
their peculiar tastes to produce certain peculiar flowers. Preferring
those colours and odours which guided them to their primitive
food, they produced, wherever they got special influence, dull,
yellowish, or dark-purple colours, often accompanied with a putrid
smell. The stupidity of flies also favoured the production of cer-
tain contrivances to insure crossing, ¢.g. the prison-flowers of Arwim
and Aristolochia, the traps of Pinguicula alpina, Cynanchum, and
Stapelia, or the deceptions of Paris, Ophrys, and Parnassia.

Gradually, from the miscellaneous lot of flower-visiting insects,
all much alike in their tastes, there arose others more skilful and
intelligent, with longer tongues and acuter colour-sense ; and they
gradually caused the production of flowers with more varied
colours, honey invisible to or beyond the reach of the less intel-
ligent short-tongued guests, and various contrivances for lodging,
protecting, and pointing out the honey.

Lepidoptera, by the thinness, sometimes (Sphingide) by the
length of their tongues, were able to produce special modifications.
Through their agency were developed flowers with long and narrow
tubes, whose colours and time of opening were in relation to the
tastes and habits of their visitors. We may thus distinguish flowers
adapted for butterflies (Dianthus deltoides and many Silenee), or for
moths (Platanthera) ; for diurnal hawk-moths (Gentiana bavarica,
G, verna), for nocturnal hawk-moths (Lonicera Caprifolium) ; and
intermediate stages (e.g., Crocus vernus). The acute sense of smell
in Lepidoptera reveals itself in the aromatic scent of Pinks,
Nigritella, Daphne striata, ete., and the colour-sense of butterflies
is shown in the flowers, usually red and prettily marked, which
are due to them.

PART IV. | GENERAL RETROSPECT. 595

The Jchnewmonide at first surpassed all other visitors in obser-
vation and discernment, and they were thus able to produce
inconspicuous flowers which escaped the notice of other visitors.
On the appearance of sand-wasps and bees these inconspicuous
flowers were banished by competition to the less frequented
localities (¢.g., Listera to shady woods).

The Sand-wasps (Sphegidw) apparently took the place to a
great extent of the Ichneumons, and produced flowers where
organs had to be thrust apart (Papilionaceze), or where a narrow
cavity had to be entered (Labiate), or where some other action
similar to the act of digging had to be performed. Subsequently
bees seem to have entered on joint possession of most of these
flowers, and to have added special adaptations of their own.

The true Wasps (Vespidw) could establish themselves by the
fear of their sting (and of their jaws) in sole possession of certain
flowers with wide open mouths and abundant honey. These they
developed farther in relation to their wants (Serophularia, Sym-
phoricarpus, Epipactis latifolia, Lonicera alpigena); but where
wasps are scarce the flowers are utilised by other insects.

Bees (Apidae), as the most skilful and diligent visitors, have
played the chief part in the evolution of flowers; we owe to
them the most numerous, most varied, and most specialised forms.
Flowers adapted for bees probably surpass all others together in
variety of colour. The most specialised, and especially the gre-
garious bees, have produced great differentiations in colour, which
enable them, on their journeys, to keep to a single species of flower.
While those flowers which are fitted for a miscellaneous lot of
short-lipped insects usually exhibit similar colours (especially
white or yellow) over a range of several allied species, the most
closely allied species growing in the same locality, when adapted
for bees, are usually of different colours and can thereby be
recognised at a glance (¢g., Trifolium, Lamium, Teucrium,
Pedicularis),

Some Drone-flies (Syrphide) also, which admire bright colours
and are themselves brightly adorned (Ascia, Melanostoma,
Sphegina, etc.), have produced special flowers suited to their
tastes, which they mainly fertilise (Saxifraga rotundifolia, S.
umbrosa, etc.); sometimes we even find a special and simple
mechanism adapted for them (Veronica Chamedrys).

The power to distinguish red, violet, and blue colours must
have been acquired to a certain degree by flesh-flies and carrion-
flies in seeking their natural food; but in other flower-loving

Q@Q2

596 THE FERTILISATION OF FLOWERS. [PART IV.

insects this power seems only to have arisen with the habit of
visiting flowers, and to have increased pari passw with the taste
for flowers and with the length of the proboscis. On the whole
we find red, violet, and blue colours appearing for the first time
in flowers whose honey is quite concealed and which are visited
by more or less long-tongued insects (bees, long-tongued flies,
Lepidoptera), or else in flowers visited for the sake of their pollen
chiefly by bees and: drone-flies (Hepatica triloba, Verbascum
pheniweun).

The forms, colours, and odours of the flowers in a particular
region must depend in the closest manner upon the insect fauna
of the region, and especially upon the relative abundance in it of
the various classes of insects. This conclusion is in complete
accordance with the following comparison of my observations on
the Alps and in North Germany. On the Alps, Hymenoptera and
especially bees are relatively much less numerous and Lepidoptera
much more numerous than in Low Germany.

I have observed upon flowers :—

1. In Low Ganuany.| * Ohman, | OR TREES,

Gt Inooota.| obbaryed. [ot Ingocta | dbecrved. of Ineoets. | Sbabewed

Coleoptera. ... 129 469 83 337 33 134
Diptera 253 1,598 348 1,856 210 930
Hymenoptera 368 | 2,750 188 §| 1,382 88 519
(Apide) (205) | (2,191) | (120) | (1,141) | (49) | (402)
Lepidoptera 79 | 865 | 220 | 2,122 | 148 | 1,190
Other Insects 14 49 7 15 3 6
TOTAL... 843 5,231 841 5,712 482 2,779

PART IV. | GENERAL RETROSPECT. 597

Of each 1,000 different visits observed (differing either in the
species of flower visited or the species of insect visiting it) there
are therefore :—"

i Intow 2 on the atpe 3, APore te
Coleoptera 89°6 59°0 | 48°2
Diptera 805°5 324°9 | 334°6
|
Hymenoptera... 525°7 242-0 | 186°8
(Apide) (413°1) (200°0) | (144°6)
Lepidoptera... 69°8 871°5 | 428°3
Other Insects... 9°4 = 2°6 | 2°1
Toran 1,000°0 1,000°0 | 1,000°0

1 Cf. Nature, vol. xxi. p. 275, 1880.

“As Ca
“a, tik)
i) ie =:

ADDENDA.

Kee Baillon. Mowvements dans les organes sexuels des végétaux. Paris,
0. ‘

(209A) 8S. S. Dowson. ‘Ground Ivy.” Nature, Vol. xxvii. p. 126. 1883.

(229A) LéoErrera, ‘* Réponse & une note de M. Ed. Heckel, au sujet de la
fécondation dans le genre Geranium.” Bull. de la Soc. Roy. de Bot. de Belg.,
ler Mars, 1879, pp. 42-44.

(3158) Edwin Haviland. ‘Occasional Notes on Plants indigenous in the
neighbourhood of Sydney; III. Lobelia.” Proce. Linn. Soc. N. S.. Wales,
March 28, 1883.

(318A) Ed. Heckel, ‘‘ Réponse & une note de M. Léo Errera au sujet de la
fécondation dans le genre Geranium.” Bull, de la Soc. Roy. de Bot. de Belg.,
ler Mars, 1879, pp. 41, 42.

(397A) Ulr. K ramer. ‘‘Ja wohl unterscheidet die Biene die Farbe der Bliithen.”
Schweiz. Bienenzeitung, Vol. 11. pp. 179-183. 1880.

» (419A) Sir John Lubbock. Blwmen und Insecten in ihren Wechselbexiehungen ;
tibersetzt von A. Passow. Berlin. 8vo. 1876.

(422A) F. Ludwig. Die Befruchtung der Pflanzen durch Hiilfe der Insecten,
und die Theorie Darwin's von der Entstehwng der Arien. Gottingen. 1867.

(621A) Hermann Miller. ‘‘ The Effect of the Change of Colour in the
Flowers of Pulmonaria officinalis on its Fertilisers.” Natwre, Vol. xxvii. p. 81.
1883. .

(671A) ©. V. Riley. ‘‘The True and the Bogus Yucca-moth, with remarks on
the Pollination of Yucca.” Amer. Entomol. Vol. 1. pp. 141-145. June, 1880.

(697A*) S. J. Smith. ‘‘ Notes on the Fertilisation of Cypripediwm spectabile,
Swartz, and Platanthera psychodes, Gray.” Proc. Boston Soc. Nat. Hist. Vol. Ix.
pp. 328, 329. 1863 (1865). ty

June, 1883.

BIBLIOGRAPHY.

I HAVE inserted in this list all books, paper's, and notes, dealing with the
subject of the fertilisation of flowers, which I have been able to find. I have
made no very diligent search for obscure works of the pre-Darwinian period,
but I have inserted all such of the older works as are well known or important.
I have wholly avoided the vast literature on hybridisation, though much of it
trenches closely upon the proper subjects of the list ; I have inserted only the
more important reviews of books, and I have not catalogued references to
the subject in general text-books. I have done my best to make this list
complete, but I am well aware how far all such efforts must fall short of
success. Dr. Hermann Miller has revised the proofs, adding many entries to
the list.

The index to the list is a rough one; it refers only to notes and papers
dealing with one or a very few geneta: books and the more comprehensive
papers are not indexed.

D'Arcy W. Tompson.

® Dr. Alefeld. ‘‘ Ueber Linum.” Sot. Zeit, xxt. pp. 281, 282. 1863.
(2) Dr. Alefeld. ‘Ueber Tridcie und Trimorphie.” Bot. Zeit. xx1. p. 417.
1863.

(24) Grant Allen. ‘The Origin of Flowers.” Cornhill Mag. Vol. xxxvu.
p- 534. 1877. Pop. Sci. Rev. Vol. ur. p. 151. 1877.

(3) Grant Allen. The Colour-sense, its Origin and Development. Chap. tv.
** Insects and Flowers,” pp. 83-80. 8vo. London, 1879.

(4) Grant Allen. ‘‘ The Colours of Flowers, as Illustrated by the British Flora.”
Nature, Vol. xXvi. pp. 299-304, 323-326, 346-350, 371-374. 8vo. London, 1882.

(5) J. Anderson. ‘‘ Fertilisation of Orchids.” Jowrn. of Horticulture, p. 287.
April 21, 1863.

(6) J. Anderson. ‘Fertilisation of Orchids.” Gard. Chron. p.1137. 1869.

(7) G. Arcangeli. “ Osservazioni sul Dracunculus vulgaris, Schott.” Nuovo
Giorn. Bot, Ital, Vol. x1. pp. 24-41. 1879.

(7A) G. Arcangeli. ‘‘ Sulla Caprificazione, ete.” Processi Verbali della Soc.
Toscana di Sci. Nat. November, 1882.

(7B) G. Arcangeli. ‘‘Osservazioni still impollinazione in alcune Aracee.”
Nuovo Giorn. Bot. Ital. Vol. xv. pp. 72-97. 1883.

(8) J.B. Armstrong. ‘‘A Synopsis of the New Zealand Species of Veronica,
with Notes on a New Species.” Zrans. N. Z. Instit. Vol. x11. pp. 344-859. 1880.

(9) M. Arnaud. “Quelques observations sur le Gladiolus Guepini, Koch.”
Bull. de la Soc. Bot. de France, XX1v. pp. 266-271. 1877.

(10) P. Ascherson. “ Ueber die Bestaubting bei Juncus bufonins, Linn.” Bot,
Zett. XXIX. pp 551-555. 1871.

600 THE FERTILISATION OF FLOWERS.

(11) P. Ascherson. ‘‘Noch einige Bemerkungen iiber die Bestiubung bei
Juncus bufonius, L.” Bot. Zeit. xxx. pp. 697-699. 1872.

(12) P. Ascherson. ‘‘ Die Bestiéubung einiger Helianthemum-Arten.” Sit-
zungsber. der ges. Naturf. Frewnde zu Berlin, No. vit. pp. 97-108. 1880. Reviewed
by Dr. H. Muller. Bot. Zeit. pp. 50-52. 1881.

(13) P. Ascherson. ‘Die Zwangsbefruchtung einiger Cistineen.” Kosmos,
Vol. VIII. pp. 302-306. January, 1881.

P. Ascherson. Vide Delpino, No. 183.

(14) E. Askenasy. ‘*Ueber das Aufbliihen der Griser.” Verh. des Naturh.
Medic. Ver. zu Heidelberg, N.S., Bd. 11. pp. 261-273. 1879.

(15) E. Askenasy. ‘‘ Ueber explodirende Staubgefiisse.” Verh. des Naturh.
Medic. Ver. zu Heidelberg, N.S., Bd. 0. pp. 273-282. 1879. :

(16) Severin Axell. ‘‘Om det fargade hyllets betydelse fér vaxten.” Bot.
Notiser, Tredje haftet. 1868.

(17) Severin Axell. Om anordningarna for fanerogama vaxternas befrukt-
ning. Stockholm,1869.

(174) F. W. BB. ‘* Fertilisation of Leschenaultia formosa.” Gard. Chron.
p. 1103... 1871.

C. C. Babington. See No. 235.

(18) Th. Bail. ‘‘Ueber androgyne Bliithenstinde bei solchen Monécisten und
Didcisten bei denen Trennung der Bliithenstiinde Regel ist.” Schriften der Naturf.
Gesellsch. in Dantzig, Neue Folge, Bd. u. No. 3. 1869.

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C. Darwin. Vide Nos. 60, 113, 273, 286, 290, 324, 354, 453-

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606 THE FERTILISATION OF FLOWERS.

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a a Pe

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RR

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——
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”

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;
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(441) F. Ludwig. ‘‘ Weiteres iiber Alsineen.” Bot. Centralbl. Bd. vim. No.
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42 ‘
(442) F. Ludwig. ‘‘ Hyoscyamus niger, L.; C. agrestis, Veit.” Bot, Centralbl.
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(443) F. Ludwig. ‘‘ Zur Biologie der Apocyneen.” Bot. Centralbl. Bd. vu.
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(444) R. Irwin Lynch. ‘‘On the Mechanism for the Fertilisation of Meyenia
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(445) R. Irwin Lynch. ‘‘On a Contrivance for Cross-fertilisation in Roscoca
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(446) C. J. M. ‘Some Notes on Physostegia Virginiana.” Bot. Gaz. Vol. vit.

111. 1882.
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Jules Macleod. See No. 545.

(448) P. Magnus. ‘‘Ueber die Befruchtung von Yucca.” Sitzwngsber. des
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(449) P. Magnus. ‘‘ Uber den Gynodiécismus von Succisa pratensis M. and K.
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(450) Henri Marts. ‘De Ja fécondation des fleurs stériles de la vigne.”
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(451) H. Marés et J. Planchon. ‘Sur la floraison et la fructification de la

616 THE FERTILISATION OF FLOWERS,

vigne.” Compt. Rend. Vol. LXIv. pp. 254-259. 1867. Trausl. in Ann. and Mag.
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(452) A. F. M (arion).. Note sur la floraison du Dracena Goldicana observée
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Centralb. Bd. 1x. No. 6. 1882.

(453) Wm. Marshall. ° “ Fertilisation of British Orchids by Insect Agency.”
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(454) Wm. Marshall. “ Fertilisation by Moths (Habenaria chlorantha).”
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(455) IsaacC. Martindale. ‘‘Cleistogamous Flowers of Danthonia.” Amer.
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(456) Isaac C. Martindale. ‘‘Sexual Variation in Castanea Americana,
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(457) F. Masé. ‘‘ Atto di unione tra le piante maschili delle valli del Tartaro,
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(458) M. T. Masters, “ Sexuality in Plants.” Pop. Sei. Rev. Vol. xu. pp.
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(459) C.J. Maximowicz. ‘ Einfluss fremden Pollens auf die Form der erzeugten
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(460) Paul Mayer. ‘‘Zur Naturgeschichte des Feigeninsecten.” Mittheil. aus
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(460A) Friedrich Kasimir Medicus. Botanische Beobachtungen. 2 Vols.
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(4608) Friedrich Kasimir Medicus, Piatto Abhandlungen.
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(461) T. Meehan. ‘On the Structure of Lopezia.” Proc. Acad. Nat. Sez.
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(462) ‘T. Meehan. ‘On Diccious Forms of Vitis vinifera, L.”’ Proc. Acad.
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(463) T. Meehan. ‘“ Variations in Epigea repens,” Proc. Acad, Nat. Sei.
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(464) Meehan. ‘‘ Monecism in Luzula campestris.” Proc. Acad. Nat. Sci.
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(465) T. Meehan. ‘‘ Mitchella repens, L., a Dicecious Plant.” Proc. Acad. Nat.
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(466) T. Mechan. ‘On the Sexes of Plants.” Amer. Assoc. Proc. XVII.
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(468) T. Meehan. ‘‘Cross-fertilisation and the Law of Sex in Euphorbia.”
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(469) T. Meehan. “On Objections to Darwin’s Theory of Fertilisation
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(470) T. Meehan. ‘‘On Two Classes of Male Flowers in Castanea.” Proce.
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(471) T. Meehan. On the Flowers of Aralia spinosa, L., and Hedera helix,
L.” Proce. Acad. Nat. Sci. Philadelphia, pp. 107, 108. 1870. Abst, Ann. and
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(472) T. Meehan. ‘*The Agency of Bees in Obstructing Evolution.
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(473) T. Meehan. ‘‘On Hermaphroditism in Rhus cotinus (the Mist Tree), and
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4 T. Meehan. ‘‘ Influence of Pollen in Cross-fertilisation.” Proc. Acad.
Nat. Sci. Philadelphia, pp. 16,17. 1873.

(475) T. Meehan. ‘ Flowers of Viola and Impatiens.” Proc. Acad. Nat. Sei.
Philadelphia, p. 101. 1873.

(4754) Thomas Meehan. ‘‘Cleistogenous Flowers in Viola striata.” Amer,
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476) Thomas echent ‘* Fertilisation of Pedicularis Canadensis.” Acad. of
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and Mag, of Nat, Hist, Sevies tv. Vol. xu. p. 497. 1873,

”

Proce.

— ee

BIBLIOGRAPHY. > Sa

(477) T. Meehan. ‘Insects as Florists.” Gard. Chron. p. 949. 1873.
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(478) Thomas Meehan. ‘‘ Dimorphous Flowers in Passiflora.” Proc. Acad.

Nat. Sci. Philadelphia, p. 9. 1874.

479} T. Meehan. ‘‘ Fertilisation of Gentiana.” Ibid. p. 160. 1874.

480) Thomas Meehan. ‘‘ Are Insects any Material Aid to Plants in Ferti-
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(483) Thos. Meehan, ‘Are Insects a Material Aid in Fertilisation?” The
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(484) Thomas Meehan, ‘‘Self-fertilisation in Browallia elata.” Proc. Acad.
Nat. Sci. Philadelphia, p. 13. 1876. ,

(485) Thomas Meehan. ‘‘The ‘Sleep of Plants’ as an Agent in Self-ferti-
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(486) Thomas Meehan. © ‘Fertilisation of Flowers by Insect Agency.” Proc.
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(487) Thomas Meehan. ‘ Nocturnal Flowering of Mentzelia ornata.” | Proe.
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(488) Thomas Meehan. ‘‘Self-fertilisation in Mentzelia ornata.” Proc.
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(495) T. Meehan. ‘‘ Dimorphism in Atlantus glandulosa.” Ibid. pp. 287, 288.

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618 THE FERTILISATION OF FLOWERS.

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(507) Thos. Meehan. ‘‘Cleistogamy in Oxalis acctosella.” Ibid. p. 350.

(508) Thos. Meehan. ‘‘ Dicecism in Andromeda Catesbei.” Ibid. p. 356.

(509) Thos. Meehan. ‘‘ Changes of Flowers normally of one Sex to the other.”
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(511) Thos. Meehan. ‘‘ Flowering of the Chestnut.” Proce. Acad. Nat. Sei.
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(512) Thos. Meevan. ‘‘ Fertilisation of Aquilegia.” Amer. Naturalist, Vol.
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(513) Thos. Meehan. ‘‘Ohjects of Sex and Odour in Flowers.” (Read
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(516) Thos. Meehan. ‘‘ Fruiting of Ginkgo triloba.” Proc. Acad. Nat. Sei.
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(517) Thos. Meehan. ‘‘ The Relation of Heat to the Sexes of Flowers.” Proc.
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(518) Thos. Meehan. ‘‘ Protandryof Pastinaca.” Bot. Gazette, Vol. Vu. pp.
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(519) Thos. Meehan. ‘‘ Motility in the Flowers of Draba verna.” Amer.
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(520) Thos. Meehan. ‘‘Sexuality of Croton monanthogynum.” Amer,
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(521) Thos. Meehan. ‘‘Note on Yueca gloriosa.” Amer. Nalur. Vol. xvt.
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(522) Prosper Meniere. ‘‘ Note sur la fécondation des Orchidées.” Bull.
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(523) — Mézard. ‘‘ Considérations générales sur la fécondation artificielle.” Ann.
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(525) L. D. Mignault. ‘‘Quelques notes sur la fertilisation des plantes.”
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(526) Wm. Miller. ‘‘ Bees as Fertilising Agents (on Peaches).” Gard. Chron.
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(527) John Traherne Moggridge. ‘‘ Observations on some Orchids of the
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(528) J. Traherne Moggridge. Flora of Mentone. 1867. (Ophrys, ete.)

(529) J. Traherne Moggridge. ‘‘Ueber Ophrys insectifera, L.” Verh. der
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(530) J. Traherne Moggridge. ‘Fertilisation of the Fumariacee.” Nature,
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(531) H. v. Mohl. © ‘‘Finige Beobachtungen iiber dimorphe. Bliithen.”
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(532) Hugo v. Mohl. ‘‘ Observations sur les fleurs dimorphes.” Ann. des
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(533) Abbé Moigno. ‘‘La fécondation artificielle.” Les Mondes: Revue
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(534) — Monnier. ‘Note sur quelques especes du genre Viola.” Arch. de
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(535) David Moore. ‘*On the Morphology of Sexes in some Dicecious Plants.”
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ie oa > ~

a

BIBLIOGRAPHY, | 619

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(539) 8S. Moore. ‘‘ The Different Forms of Flowers in Plants of the same Specics,
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(540) S. Moore. ‘*Mr. Darwin’s Doctrine of Cleistogamy.” Jowrn. of Bot.
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(544) C. Ed. Morren. ‘‘ Anchusa sempervirens.” La Belgique Horticole,
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(547) H. N. Moseley. ‘‘Further Notes on the Plants of Kerguelen, with
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(548) F.T. Mott. ‘Colour in Flowers not due to Insects.” Natwre, Vol. x.
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(549) Fritz Miller. ‘‘Ueber die Befruchtung der Martha (Posoqueria)
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(550) Fritz Miiller. ‘‘ Notizen tiber die Geschlechtsverhiltnisse brasilianischer
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(551) Fritz Miller. ‘‘ Befruchtungsversuche iiber Cipé alho (Bignoniacea).”
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(552) Fritz Miiller. ‘* Ueber Befruchtungserscheinungen bei Orchideen.”’
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(553) Fritz Miller. ‘‘ Uebereinige Befruchtungserscheinungen.” Bot. Zeit.
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(554) Fritz Miiller. ‘‘ Ueber eine dimorphe Faramea.” Bot. Zeit. Xxvil.
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(555) Fritz Miller. ‘*Umwandlung von Staubgefissen in Stempel bei
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(555A) Fritz Miller. ‘‘On the Modification of the Stamens in a Species of
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(556) Fritz Miiller. ‘‘ Ueber den Trimorphismus der Pontederien.” Jenaische
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(557) Fritz Miiller. Bestéuhwngsversuche an Abutilon-Arten. Jenaische
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620 THE FERTILISATION OF FLOWERS.

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. (559) . Fritz Miller. ‘‘In Blumen gefangene Schwirmer.” Kosmos, Vol. 11.
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(560) Fritz Miiller. ‘‘ Flowers and Insects (Bunchosia, Lantana, Pontederia,
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(561) Fritz Miiller. ‘‘Cleistogamic Podostomacew.” Nature, Vol. x1x.
p. 463. 1879.

(562) “Fritz Miiller. ‘‘ Hesperiden-Blumen Brasiliens.” Kosmos, Vol. tv.
pp. 481, 482. March, 1879. |

(563) Fritz Miiller. ‘‘ Die Imbauba und ihre Beschiitzer.” Kosmos, Vol. v1tt.
pp. 109-115. 1880.

(564) Fritz Miller. ‘‘Caprificns und Feigenbaum.’’ Kosmos, Bd. xt. Heft
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(554A) Fritz Miller. ‘‘ Two kinds of Stamens with Different Function in the
Same Flower.” Nature, Vol. xxvu. pp. 364, 365. 1883. (Heteranthera, Lager-
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Fritz Miller. Vide Hildebrand, Nos. 353, 359.

(565) Hermann Miller. ‘‘Beobachtungen an westfilischen Orchideen.”
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(566) Hermann Miller. ‘‘ Ueber die Anwendung der Darwin’schen Theorie

auf Blumen und Blumen-besuchende Insekten.” Verh. des Naturf, Vereins der
pr. Rheinlande und Westfalens, Corr. Bl. 43-66. 1869.

(567) Hermann Miller. . ‘‘ Applicazione della teoria Darwiniana ai fiori ed agli
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(568) Hermann Miller. ‘‘ Application of the Darwinian Theory to Flowers
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(569) Hermann Miiller. ‘‘ Anwendung der Darwin’schen Lehre auf Bienen.”

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(571) Hermann Miiller. ‘‘ Proboscis capable of Sucking the Nectar of Angre-
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(572) Hermann Miiller. Die Befruchtung der Blumen durch Insekten. 8vo.
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(573) Hermann Miller. ‘*La fécondation des fleurs par les insectes.””.

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pp. 368-376. 1873.

(574) Hermann Miiller. ‘*Ground Ivy.” Nature, Vol. vu. p. 161.
1873.

”

(575) Hermann Miller. ‘‘ Fertilisation of the Fumariacez.” Natwre, Vol. tx.
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(575A) Hermann Miiller. ‘‘ Gegenseitige Abhingigkeit von Blumen und sie
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(577) Hermann Miiller. ‘* Flowering of the Hazel.” Nature, Vol. xu. p. 26.
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(577A) Hermann Miiller. ‘‘Gehen auch die deutschen Dompfaffen dem
Honige der Schliisselblumen nach?” Der Zool, Garten. xvi. pp. 168-170, May,
1875.

(578) Hermann Miller. ‘ Self-fertilisation of Plants.” Natwre, Vol. xtv.
p. 570. 1876. 3

(579) Hermann Miiller. ‘‘ Die Bedeutung der Honigbiene fiir unsere Blumen.”
Eichstidter Bienenzeitung, Nos. 7-14. 1875. Nos. 2, 10, 11, 14. 1876. Abst.
Nature, Vol. x1. p. 10, 1876, Vol. xv. pp.-178-180. 1877,

| a y
ae * o>

a

BIBLIOGRAPHY, 621

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(582) Hermann Miller. ‘‘ Geschichtliche Entwickelung der Gattung Gentiana.’
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1

(587) Hermann Miller. ‘Alpine Flowers.” Matwre, Vol. xvut. p. 519.
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(589) Hermann Miiller. ‘‘Die Insekten als unbewusste Blumenziichter.”
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(591) Hermann Miller. ‘‘ Die Befruchtung von Erica ecarnea.” Kosmos,
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(592) Hermann Miller. ‘‘ Fertilisation of Hrica carnea.” Nature, Vol. xx.
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(593) Hermann Miiller. ‘‘ Kolreuter und Sprengel.” Kosmos, Bd. v. pp.
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- (594) Hermann Miller. ‘‘ Bombus mastrucatus, ein Dysteleolog unter den
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(597A) Hermann Miller. “ Ein Kaefer mit Schmetterlingsriissel.” Kosmos,
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(598) Hermann Miiller. ‘Gaston Bonnier’s angebliche Widerlegung der
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622 THE FERTILISATION OF FLOWERS.

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(606) Hermann Miiller. ‘‘ Two Kinds of Stamens with Different Functions in
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' (607) Hermann Miller. ‘‘Gradations between Hermaphroditism and Gyno-
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(608) Hermann Miller. ‘‘Bemerkungen tber F. Hildebrand’s Vergl. Unter-
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(609) Hermann Miller. Die Alpenblumen, ihre Befruchtung durch Insekten,
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(611) Hermann Miller. ‘‘ Polymorphism of the Flower-heads of Centaurea
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. (612) Hermann Miller. ‘‘ Die biologische Bedeutung des eigenthiimlichen
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(614) Hermann Miiller. ‘‘ Ein Kaefer mit Schmetterlingsriissel.” Kosmos,
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(615) Hermann Miller. “ Die Stellung der Honigbiene in der Blumenwelt.”
Bienenzettung, Nos. ul. and x. 1882.

(616) Hermann Miller. ‘‘ Variability of Number of Sepals, Petals, and
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(617) Hermann Miller. “Two Kinds of Stamens with Different Functions in
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(618) Hermann Miller. ‘‘ Versuche tiber die Farbenliebhaberei der Honig-
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(620) Hermann Miiller. ‘‘Geschichte der Erklarungsversuche in Bezug auf
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Hermann Miiller. See also Nos. 12, 170, 432, 650, 661, 700, 738.

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(629) George Nicholson. ‘On the Fertilisation of the Flowers of some
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1 —— a

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626 THE FERTILISATION OF FLOWERS.

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a

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2

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(754) R. de Visiani. ‘ Metodo della fecondazione... . della Vaniglia.”
Venezia, 1844.

(754A) R. Vion. Bull. Soc. Linn. du Nord de la France, Amiens, p. 151, 1878.

(755) H. de Vries. . ‘‘ Bestuivingen van Bloemen door Insecten waargenommen
in 1874.” Nederl. Kruidk. Arch. pp. 64-76. 1875. :

(756) A. R. Wallace... ‘‘On some Relations of Living Things to their En-
vironment.” Brit... Assoc. Rep. pp. 101-110. 1876. Gard. Chron. Vol. v1. p. 390.
1876. Entomologist, Vol. 1x. pp. 221-229. 1876. AS oe

A. R. Wallace. “On the Peculiar Relations of Plants and Animals as
exhibited in Islands.” Nature, pp. 406-408. Sept. 1879 Ae

(758) Lord Walsingham. ‘‘ Fertilisation of Yucca.” Nature, Vol. xxiii.

462” 1880, >. Fs pat ‘s Ppa ta rt
“ (759) J. Walz. ‘Ueber die Befruchtung in den geschlossenen cia esa von
; So So

628 THE FERTILISATION OF FLOWERS.

Lamium amplexicaule, L., und Oryza clandestina, A. Br.” Bot. Zeit. xxtt. pp.
145, 146. 1864.

(760) Lester F. Ward. ‘‘ Cross-fertilisation in Sabbatea angularis.” Gar-
dener’s Monthly, p. 278. 1878.

(760A) Lester F. Ward. ‘‘Sexual Differentiations in Zpigea repens.’’ Amer.
Naturalist, Vol. xiv. pp. 198-200. 1880.

(7608) Lester F. Ward. ‘‘The Relation between Insects and Plants, and the
Consensus in Animal and Vegetable Life.” Amer, Entomol. Vol. 111. pp. 68-67,
87-91. 1880.

(760c) Lester F, Ward. ‘‘Incomplete Adaptation as illustrated by the
History of Sex in Plants.” Amer. Naturalist, Vol. xv. pp. 89-95. 1881.

(761) Lester F, Ward. ‘‘Proterogyny in Sparganiwm eurycarpum.” Bot.
Gazette, Vol. vil. No, 819, p.100. 1882.

(762) Eug. Warming. ‘‘Smaa biologiske og morfologiske bidrag.” Bot.
Tidsskrift, 3, 11. 1877, Nogle Blomsters Bygning og Biologi, pp. 108-130.

(763) Fred. I. Warner. “Fertilisation of Plants.” Journ. of Bot. N.S.
Vol. 1. pp. 110, 111. 1872.

(764) J. P. Mansel Weale. ‘‘ Notes on the Structure and Fertilisation of the
Genus Bonatea.” Journ. Linn. Soc., Bot. Vol. X. pp. 470-476, 1869.

. (765) J. P. Mansel Weale. ‘‘ Notes ona Species of Disparis found on the
Kugaberg, South Africa.” Jowrn. Linn. Soc., Bot. Vol. x11. pp. 42-45. 1873.

(766) J.P. Mansel Weale. ‘‘Some Observations on the Fertilisation of Disa
macrantha.” Journ. Linn, Soc., Bot. Vol. xii. pp. 45-47. 1873.

(767) J. P. Mansel Weale. ‘‘Notes on some Species of Habenaria found in
South Africa.” Journ. Linn. Soc., Bot. Vol. xu. pp. 47, 48. 1873.

(768) J. P. Mansel Weale. ‘‘ Observations on the Mode in which certain
Species of Asclepiadew are Fertilised.” Journ. Linn. Soc., Bot. Vol. xut. pp. 48-58.
1873.

(769) W. Mansel Weale. ‘“‘ Note on South African Orchids.” Jowrn. Linn.
Soc., Bot. Vol. XVI. p. 313. 1880.

H. Wendland. See No. 704,

(769A) J. O. Westwood, ‘‘On Caprification as practised upon Figs in the
South of Europe and the Levant.” Trans. Entom. Soc. Lond. Vol. 11. pp. 214-224.
1837.

(770) F. D. Wetterhan. ‘‘ Flowering of the Hazel.” Nature, Vol. xt.
p. 507. 1875.

(771) ©. F. White. ‘* Fertilisation of Flowers (Scabiosa).” Natwre, Vol.
XIv. p. 250. 1876. .

(772) F. Buchanan White. ‘‘ Winter Fertilisation by Agency of Insects.”
Journ. of Bot. N.S., Vol. 1. p, 48. 1872.

(773) F. Buchanan White. ‘‘ The Influence of Insect-Agency in the Dis-
tribution of Plants.” Jowrn. of Bot. N.S., Vol. 1. pp. 11-13. 1873. Amer. Nat.
Vol. vit. pp. 268-271. 1873.

(774) Thos. Whitelegge. ‘‘Gynodicecious Plants.” Nature, Vol. xvit.
p- 588. 1878. (Ranunculus, Stachys, Gewm.)

(775) — Williams. ‘‘ Artificial Fertilisation [of Victoria regia].” Gard. Chron.
Vol. xvi. p. 276. Aug. 1881. Dundee Hortic. Assoc. 1881.

(776) Moritz Willkomm, ‘‘Natiirliche Fliegenfallen.” Von Fels zw Meer.
Bd. 1. Heft 111. pp. 336-339. Dec, 1881.

(777) A. Stephen Wilson. (Kinmundy.) ‘‘On the Fertilisation of Cereals.”
Journ. of Bot. N.S., Vol. Iv. pp. 121, 122. April, 1875. Gard. Chron. Feb. 20,
1875. Trans. and Proc. Bot. Soc, Edin, Vol. xt. p. 506. 1873. Vol. xiz. pp.
84-95, 237. 1874. Abst. Nature, Vol. x1. p. 270. 1875.

(778) A. Stephen Wilson, ‘‘On the Association of an Inconspicuous Corolla
with Proterogynous Dichogamy in Insect-fertilised Flowers.” Brit. Ass, Rep. p
564-566. 1878. Journ. of Bot. N.S., Vol. vil. pp. 314, 315. 1878. Nature, Val
xIx. p. 508. 1878. (Serophularia, Gladiolus.)

(779) A. Stephen Wilson, ‘On the Nectar of Flowers.” Brit. Ass. Rep.
p. 567. 1878.

(780) A. Stephen Wilson. ‘‘ Notes on some Dimorphic Plants.” Brit. Ass.
Rep. p. 568. 1878. (Hrythrcea, Silene acaulis.)

(781) A. Stephen Wilson, ‘Some Mechanical Arrangements Subserving
Cross-fertilisation in Plants.” Brit. Ass. Rep. p. 568. 1878. (Pinguicula,
Vinea.)

- =

BIBLIOGRAPHY. 629

(782) N. P. Wilson. ‘‘On Cross-fertilisation.” Proc. Nat. Hist. Soc. of Boston.
Vol. xvi. p. 359. 1876.

(782A) . Wilson. ‘‘On the Hair-collectors of Campanula.” Hooker’s London
Journ. of Bot. Vol. 1. pp. 601-605, 1842,

(7828) W. Wilson. ‘‘ Further Remarks on the Pollen-collectors of Campanula,
and = the mode of Fecundation.” Hooker's London Journ. of Bot. Vol. v1. pp.
90-97. 1848.

(783) L. Wittmack. ‘*'The Nectar-cups of the Marcgraviaceer.” Gard. Chron.
Vol. xiv. p. 78, 1879,

(784) Ludw. Wittmack. ‘‘Die Marcgraviaceen und ihre Honiggefiisse.” Verh.
der Bot. Ver. der Provine Brandenburg, Sitzwngsber. pp. 41-50. 1879. Kosmos,
Vol. v. pp. 267-277. July, 1879.

(785) L. Wittmack, ‘‘Ueber eine Eigenthiimlichkeit der Bliithen von
Hordeum bulbosum, L.” Sitzwngber. Ges. naturf. Freunde, Berlin, pp. 96, 97.
1882.

(786) Alphonso Wood. ‘*‘Cleistogene Flowers.” Bull. Torrey Bot. Club,
Vol. VI. p. 174. 1877.

(787) Wood and Steele. Fourteen Weeks in Botany. New York, 1879.

(787A) F. X. Woérz. Ueber die Beziehung der Nectarien zur Befruchtung und
Saamenbildung der Gewiichse” Tiibingen. 1833.

(788) Charles Wright. ‘‘ Cross-fertilisation [of Posugueria].” Amer, Natur’.
Vol. 11. p. 437. 1868.

(788A) C[harles] W[right]. ‘‘ Neswa verticillata.” Amer. Naturalist, Vol.
VIL. pp. 739, 740. 1873.

(789) H. W. Young. ‘‘Fertilisation of Gerardia flava.” Buil. Torrey Bot.
Club, Vol. 1v. p. 41. 1873.

(790) Dr. Zimmermann. ‘‘ Ueber Einrichtungen der Bliithen zum Schutz
des Pollens.” Ber. naturw. Gesellsch. Chemnitz, vi. Sitzwnysber. 8. xxx.

(791) J. Zins. Einfluss der Insekten auf die Befruchtung der Pflanzen. Ham-
burg, 1880.

(792) ‘* Fertilisation of Orchids.” West of Scotland Hortic. Mag. p. 65. Sept.
1863.

(793) ‘‘On Orchid Cultivation, Cross-breeding, and Hybridising.” Journ. of
Hortic. p. 206. March 17, 1863.

(794) ‘‘Fertilising Figsin Smyrna.” Gard. Monthly, pp.174, 175. 1877.

(795) ‘*Cross-fertilisation of Plants and Consanguineous Marriages.” Westminster
Review, Vol. cvitt. p. 466. 1877.

(796) ‘‘Fructification des Bilbergia” (Artificial Fertilisation). La Belgique
Horticole, p.120. 1875.

(797) ‘‘Ueber die kunstliche Befruchtung der Rose.” Lebi’s Jllust. Garten-
zettung, Jahrg. 24, pp. 14-16. 1880. :

(798) ‘‘ Ueber die kunstliche Befruchtung der Pelargonien.” Leb/’s Iilust. Garten-
zeitung, Jahrg. 24, pp. 106-108. 1880. ay

(799) ‘* Ueber Bestiiubung, Befruchtung, und Hybridation.” Lebi’s Illust. Garten-
zeitung. Jahrg. 24, Pp. 197-209. 1880.

(800) ‘‘Dimorphic Flowers in Euryale ferox.” Gardener’s Chron. N.S., Vol.
XIV. p. 727. 1880. Revue Horticole, p. 411. 1880.

(801) ‘* Gazania splendens flowering in Autumn.” Gardener's Chron. N.S., Vol.

xiv. p. 759. 1880. Reh S
(802) ‘‘Fécondation du Tillandsia Lindeni.” Revwe Horticole, p. 103. 1881.

Belyique Horticole, p. 72. 1881. re
(803) ‘‘ Caprification.” rans. Entom. Soc. Lond. App. pp. XXXill.-xXxxv.
81

1881.
(804) ‘*Coryanthes macrantha.” Gardener's Chron. N.S., Vol. Xvi. pp. 592,

593. 1882
Additional Works on Caprification.'

Soc) Filippo Cavolini. ‘‘ Memoria per servire alla storia compiuta del fico,
e jet eesiantens.” Opuscoli scelti sulle scienze e sulle arte, Tomo v. Milano, 1782.
(806) Giorgio Gallesio. Pomona Italiana ossia trattato degli albert fruttiferi.
Pisa. Vol. 1.1817; Vol. 1. 1820.
1 From Dr. Paul Mayer’s paper (No. 460). Some minor references, chiefly of entomological interest
which Mayer gives are not copied here.

630 THE FERTILISATION OF FLOWERS.

(807) G. Gasparrini. ‘‘ Ricerche sulla natura del Caprifico e del Fico, e sulla

Caprificazione.” tendiconto, etc., della R, Accad. della Scienze di Napoli, Vol, rv.
1845. Seg .
(808) G.Gasparrini. ‘‘Nuove ricerche sopra alcuni punti di anatomia e

fisiologia spettanti alla dottrina del fico e caprifico,” Rendiconto, etc., debla R. Accad.

della Scienze di Napoli, Vol. vil. pp. 394-417. 1848.

(809) — Leclerc. ‘‘ De la caprification ou fécondation artificielle des figuiers.”
Comptes rendus, Acad. Sci. Paris, Vol. XLVI. pp. 330-334, - 1858.

(810) H. Low. ‘‘Ueberdie Caprification der Feigen.” Stettiner Entom. Zeitung,
Vol. Iv. pp. 66, 67. 1843.

(811) Godehen de Riville. ‘‘Mémoiresur la caprification.” J/ém. de Muth.

et de Physique présentés par divers Savants a? Académie de Paris, Vol. 11. p. 369. 1755.

(812) Vincenzo Semmola. ‘‘ Dellacapyrificazione, esperienze e ragionamenti.”
Rendiconto, etc., della R. Accad. della Scienze di Napoli, Vol. tv. pp. 480, 431. 1845.

(813) Joannon di St. Laurent. ‘‘ Della caprificazione.”” Memorie della
Societa colombaria Fiorentina, Vol. 11. p. 257. Livorno, 1752.

(814). W. Botting Hemsley. ‘‘On the Relations of the Fig and the Caprifig.”
Nature, vol. XXv1I. pp. 684-586, . 1883.

_

~_

. elie CO ™~w>

INDEX TO BIBLIOGRAPHY.!

ABIES, 95

Abutilon, 557, 558

Acer, 117, 140, 499

Achimenes, 390

Acianthus, 130

Achmanthera, 696

Agrimonia, 332

Ailanthus, 495

Alisma, 332

Alnus, 19

Aloinex, 32

Alsiner, 426, 427, 441

Amaryllidacer, 334, 746

Ambrosia, 252

Amygdalus, 525

Anagrecum, 91, 256, 537, sv

Anchusa, 544

Andromeda, 508

Anthurium, 177

Apocynum, 23, 45B, 292, 411, 432,

443

Aponogetum, 367

Aquilegia, 512, 732

Arachis, 81, 82

Aralia, 471

Arbutus, 533

Argemone, 358

Aristolochia, 349, 374, 407

Arnebia, 135

Aroide, 7A, 46, 107, 199, 200, 201, 381,
596, 688, 689

Artemisiacez, 185

Asarum, 177, 662 rig

Asclepias, 45B, 71, 90, 114, I15, 146,
I7I, 347, 361, 389A, 408, 410, 542,
651, 652, 741, 768

Asparagus, 106

Aspidistra, 118 —

Asteracer, 124

BAPTISIA, 26
Batatas, 653

Bats, 546

Begonia, 555A, 5558

Berberis, 241 .
Bignoniacee, 45A, 551, 701

Bilbergia, 796
Birds, 45A, 56, 234, 287, ee, 630, ee

ict 315A
Bromus, 371
Browallia, 289, 484
Bryonia, 698
Bryophyllum, 177
Bunchosia, 560
Butomus, 112

CHSALPINIA, 335

Caffea, 224, 232

Cajophora, 177

Calamintha, 734

Calanthe, 543

Calceolaria, 332

Calonyction, 359 ~

Calycanthus, 177, 498

Campanula, 312A, 491, 782A, 7828

Canna, 204, 237 : {

Capparis, 656

Caprification, 140, 416A,-439, 460, 564,
621, 677, 700, 760, 769A, 794, $03,
805-814

Capsella, 332, 497

Cardamine, 296

Carludovica, 239

Carya, 504

Caryophyllez, 40 —

Cassia, 413, 564A, 725 > -

Castanea, 456, 470, SII, ny

Catasetum, 29, 155 eo

Centaurea, 611, 619

Centrostema, 729

Cephaelis, 33

Cerastium, 40

Ceratozamia, 100

Cereus, 678

Chamissoa, 555, 5554 +

Chrysanthemum, ‘486: »

Circa, 332 .

Cistines, 12, 13

Claytonia, 485.

* See Prefatory Note to ‘‘ Bibliography,”’ p. 599.

632 THE FERTILISATION OF FLOWERS.

Cleistogamy, 40, 79, 99, 104, S17,- 222,
318, 373, 417, 423, 424, 429, 455,
ul 534, 540, 561, 623A, 659, 718,

Clethra, 36

Clitoria, 729

Cobxa, 27, 52, 226, 227

Collomia, 423, 424, 685

Colour, 3, 4, 15, 16, 102, 103, 105, 142,
205, 365, 422, 548, 583, 600, 618, 620,
682, 690, 710

Composite, 181, 357

Comptonia, 19

Conifers, 177, 184

Conophallus, 48, 191

Convolvulus, 319

Coronilla, 244

Coryanthes, 658, 804

Corydalis, 74, 310, 350

Corylus, 19, 62, 66, 211, 306, 312, 5775
77° .

Cratoxylon, 213

Crinum, 177

Crocus, 327

Croton, 520

Cruciferee, 366, 608

Cucurbita, 264

Cymbidium, 640

Cynare, 661

Cynorchis, 537

Cypripedium, 565

Cyrtostylis, 130

Cytisus, 323, 324

D&DALACANTHUS, 696

Danthonia, 455

Datisca, 541

Dianthus, 71, 607

Dictamnus, 315, 330

Digitalis, 56

Dimorphism, 24, 33, 83, 86, 89, 1 34,
154, 156, 157, 160, 167, 186, 203, 213,
224, 225, 282, 285, 296, 319, 336, 338,
339; 342, 342, 389, 393, 402, 426, 427,
447: 478, 495, 501, 504, 506, 531, 532,
545, 554, 605, 636, 640, 684, 692, 696,
724, 800

Disa, 744, 766

Disemma, 691, 694

Disparis, 765

Draba, 497, 519

Dracena, 452

Dracunculus, 7

Drosera, 71

Duvernoia, 35

EPIDENDRUM, 553, 555A
Epigzea, 285, 463, 760A
Epilobium, 458, 147
Epipactis, 565

Epipogium, 676
Kranthemum, 12, 402, 695
Eremurus, 367, 612

Erica, 591, 592, 633
Eriophorum, 203

Erodium, 433, 434, 438
Erythrea, 780

Erythrina, 56
Eschscholtzia, 358, 550, 553
Eucorida, 628

Euphorbia, 468, 697A, 726
Euryale, 800

FABA, 492

Faramea, 553, 554

Ficus, 140, 416A, 439, 460, 564, 621,
677, 700, 740, 769A, 794

Floridez, 205

Forsythia, 280A

Fragaria, 680

Fumariacer, 74, 141, 163, 214, 332, 350,
358, 530, 536, 575

GAZANIA, 801

Gelsemium, 282

Genista, 326

Gentiana, 42, 121, 479, 582, 753

Geonoma, 239

Geranium, 229, 295

Gerardia, 21, 22, 25, 789

Gesneria, 632

Geum, 774

Gingko, 516

Gladiolus, 9

Glaucium, 358

Glaux, 332

Glechoma, 308, 574, 636

Glossostigma, 132

Gloxinia, 235

Gnaphalium, 709

Goethea, 177

Goldfussia, 541A.

Goodeniacer, 162

Goodenovie, 84

Gossypium, 197, 730

Graminee, 14, 65, 67A, 98, 123, 180, 212,
269, 300, 301, 332, 363, 367, 371, 415,
416, 440, 627, 659, 672, 673, 674 706,
797, 759; 777, 785

Gymnadenia, 274, 277

Gymnosperms, 712

HABENARIA, 274, 277, 454, 767
Hedera, 471
Heeria, 606
Helianthemum, 12, 13, 531
Helleborus, 314.
Hemerocallis, 30
Hesperide, 562
Heteranthera, 564A
Himantoglossum, 361
Hordeum, 332, 371, 785
oustonia, 506
Hoya, 623A, 699, 715
Hyoscyamus, 442

— = + 7

dade

—_

INDEX TO BIBLIOGRAPHY.

IMBAUBA, 563

Impatiens, 45A, 72, 79, 332, 417, 475, 733

Indigofera, 323, 325

JOCROMA, 177
Juglans, 186, 504, 659A
Juncus, 10, 11, 39, 119
Justicia, 113A

KALMIA, 313

LAGERSTR@MIA, 564A
Lamium, 72A, 332, 759
Lantana, 560

Larix, 177

Leersia, 212, 696
Leschenaultia, 17A, 162
Lilium, 248, 482, 641
Limodorum, 258, 644
Linaria, 524

Linum, 1, 157, 332, 339, 340, 648, 750
Liparis, 34

Listrostachys, 537
Lithospermum, 89

Loasew, 628

Lobelia, 240, 304, 558, 727, 751
Lopezia, 461

Lotus, 243

Lupinus, 414

Luzula, 464

Lychnis, 698

Lythrum, 458, 158, 393, 394

MACROSTAMIA, 135
Malva, 71, 332
Malvastrum, 122
Marantacee, 175, 629
Maregravia, 56, 783, 784
Martha, 549

Matricaria, 633
Maxillaria, 663
Medicago, 322, 323, 332, 747
Melampyrum, 632
Melastoma, 255
Melochia, 225
Mentzelia, 487, 488
Meyenia, 444

Mimulus, 38, 45B, 105A
Mitchella, 465, 501
Molinia, - 440
Monochoria, 389

Musk, 390

Myosurus, 177, 616

NECTARIES, 51, 92, 92A, 125, 187, 190,
366, 401, 608, 653, 654, 655, 6554,
656, 730, 779, 783, 784, 787A

Nepeta, 458, 72A, 308, 594, 636

Neswa, 788A

Nicotiana, 250

Nomimum, 524

Nyctaginia, 281

ONcIDIUM, 558, 693
Ophrys, 60, 136, 265, 332, 529, 586, 684

633

Orchids, 5, 6, 29, 34, 35, 63, 77, 9I,
113, II4, 115, 129, 133, 136, 139, 144,
149, 155, 155A, 159, 165, 238, 247,
253, 265, 266, 267, 272, 273, 274, 276,
277, 332, 337, 344, 361, 453, 454, 522,
527, 529, 537, 538, 543, 5434, 552,
565, 571, 576, 586, 637, 647, 663, 675,
684, 691, 694, 697, 719, 743, 744, 745,
ns 765, 766, 767, 768, 769, 792,

93

Origanum, 632

Oryza, 759 .

Oxalis, 79; 332, 348, 362, 507, 524, 738

PALIURUS, 177

Palme, 47, 177

Papaver, 358, 369 :

Papilionace, I51, 152, 169, 242, 404,
492, 633, 6554

Parnassia, 64

Passiflora, 478, 558, 691, 694

Pastinaca, 251, 518, 737A

Pavonia, 318

Pedicularis, 263, 476, 632

Pelargonium, 198, 294, 297, 332, 798

Pentstemon, 230

Peplis, 394

Phaseolus, 57, 209, 240, 368, 633

Philotheca, 315A

Physianthus, 638, 700A

Physostegia, 446

Pingtiicula, 332, 781

Pisum, 404, 633

Plantago, 458, 148, 425, 429, 430, 43!

Platanthum, 274

Podostomacee, 561

Pogonia, 697

Poinsettia, 726

Polyearpon, 40

Polygala, 303

Polygonum, 233

Pontederia, 412, 556, 560

Portulaca, 87, 494

Posoqueria, 293, 549, 788

Primula, 97, 108, 110, I1I, 154, 161,
231, 336, 340, 378, 384, 393, 398,
447, 545, 585, 604A, 692

Pringlea, 216, 372, 547

Proteacee, 85

Prunella, 332

Pterostylis, 129

Pulmonaria, 338

Pyxidanthera, 44

RANUNCULACEA, 723
Ranunculus, 485, 774
Reinwardtia, 749
Rhexia, 413A
Rhinacanthus, 177
Rhinanthus, 332
Rhodora, 367

Rhus, 473

Ribes, 120

634 THE FERTILISATION OF FLOWERS.

Rosa, 797 Taraxacum, 486
Roscoea, 445 Tecoma, 233
Rubiacez, 134, 233 Teucrium, 632
Ruellia, 696 Thalia, 645
Ruscus, 58 Thelymitra, 133
Thymus, 632, 635
SABAL, 177 Tillandsia, 802
Sabbatea, 760 . Torrenia, 28
Sagina, 38 ; Tradescantia, 322
Salvia, 332, 341, 345, 359, 445, 497, 631, Trichosanthes, 31
650, 735 Trichostoma, 377.
Salvinia, 683 Trifolium, 55, 262, 299, 486
Sapotaceze, 311 Trigonella, 748
Saxifraga, 210, 221, 604, 630A, 722 Trimorphism, 2, 160, 343, 348, 362,
Scabiosa, 771 393, 556
Schizanthus, 346 Triecism, 2, 106, 158
Scorzonera, 553 Tulipa, 643
Scrophularia, 458, 280, 486, 632, 737, 778
Selliera, 131 ULEX, 633
Sherardia, 605 Utricularia, 44
Silene, 780
Siphocampylus, 346 VACCINIUM, 633
Solanum, 560, 725 Vandellia, 399
Smilacex, 193 Vanilla, 139, 543, 754, 541C, 543A
Snails, 437 Verbascum, 161, 695
Sparganium, 761 Veronica, 8, 660,: 708
Sparmannia, 541D Vicia, I51, 152, 492
Spergula, 332 Victoria, 775
Spiranthes, 144 Vinca, 147A, 153, 636A, 781
Stachys, 774 Viola, 70, 71, 79, 246, 307, 309, 332,
Stapelia, 375 391, 475, 524, 534, 622, 625, 718
Staphylea, 486 Vitis, 450, 451, 462 [=<
Stelis, 714 Voandzeia, 81
Stellaria, 497, 605
Stratiotes, 457 WISTARIA, 264, 511A, 679
Stylidium, 5418
Succisa, 449 YucCA, 32, 37, 218, 219, 220, 405, 448,
Symplocarpus, 728 503, 514, 515, 521, 664, 667, 668, 669,
Syringa, 38, 605 . 670, 671, 681, 758
TABERNEZEMONTANA, 359 - ZEA, 45B

Taesonia, 691, 694. Zostera, 138, 223

INDEX OF INSECTS,
WITH REFERENCES TO THE PLANTS VISITED BY THEM.

ABBREVIATIONS.—L. = Lippstadt ;

Sld. = Sauerland ; Th. = Thuringia.

T. = Teklenburg, Herr Borgstette ;

Numbers placed in brackets after an insect’s name, indicate the length ot

the insect’s proboscis in millimetres.

The plants visited are designated by the numbers which they bear in the
third section of this book. To facilitate reference, the first syllable of the

plant’s order or genus is also given,

Insects useless in the work of fertilisation are marked thus, ; those (equally
useless) which bite through or burst open the flower forcibly are marked thus,f.
Those cases in which the insect fails to obtain the honey or pollen which it

seeks are marked with an asterisk (*).

I, COLEOPTERA (129 species, 469
different visits).

_A. Buprestide (1 species, 4 visits).
Anthaxia nitidula, L., L., Ran, 7 ; Ros.
153; Comp. 225, 274.

B. Cerambycide (1 species, 80 visits).

Clytus arietis, L., L., Umb. 185, Ros, 152,
149, 135, 133.

—— mysticus, L., L., Ros. 153.

Grammoptera levis, F., L, List. 13;
Corn. 197.

— lurida, F., L. T., Corn. 197 ; Umb.
185,

—— ruficornis, Pe... bb, T.. Umb. 179,
187, 186 ; Ros. 153, 149, 138, 137.
Leptura livida, Fs ia T, List. 380 ;
Umb. 179, 188, 184; Ros. 135, 133 ;
Convoly. 311 ; Scab. 211; Jas. 283 ;
Comp. 225, 239, 233, 227, 217, 267.

testacea, je soe Comp. 225.

Pachyta collaris, L., Th., Umb. 185.

— octomaculata, F., ‘Sld. 7. Siebengeb.,
Umb. 179, 181, 194, 185, 184; Ros.
134, 135, 130 ; Scab. 211-; Comp. 229.

Rhagium inquisitor, L., Sld., Umb, 194 ;
Ros. 148.
Strangaliaarmata, Hbst. (S. calearata, F.),

L. Sld., Corn. 197; Ros. 148, 135,
133 ; Scab. 211 ; Comp. 229.
——atra, F., L. Sld. T.,, Corn. 197;

Ros. 149, 185 ; Scab. 211 ; Comp. 229.
—— attenuata, L., L., Corn. 197 ; Ros.
149, 130, 133 ; Scab. 211 ; Comp. 229,

233.
bifasciata, Mill., Th., Umb. 191,
195 ;
Sld., Umb. 185 ;

Comp. 253,

melanura, L., L.
‘Ros. 1385; Scab. 211;
229, 231.

-—— nigra, L., L. Sld., Umb. 194 ; Ran.
7, Cist. 45 ; Ros. 148, 135, 133 ; Plant.
368.

Toxotus meridianus, L., Siebengeb., Scab.
211

C, Ohrysomelide: (17 species, 32
visits).

Adimonia sanguinea, F., L., Ros. 152,
Cassida seeping see OS Comp. 223,
nebulosa, L,, Ls, Crue. 33.
Ceythra cyanea, F., L., Ros. 153,

636

Ceythrascopolina, L., Th., Umb. 181, 191.
Crioceris 12punctata, L., L., Umb. 177.
Cryptocephalus Morei, L., L., Papil.
108; Comp. 267.
sericeus, L., Sld. T. Th., Umb.
194, 185; Ran. 7; Hyperic. 68 ;
Papil. 108; Scab. 211, 212 ; Jas. 283 ;
Comp. 258, 246, 225, 237, 267.
vittatus, F., Sld., Papil. 108+.
Donacia dentata, Hoppe, L., Nuph. 19.
Galeruca calmeriensis, F,,T., Umb. 182.
Haltica fuscicornis, L., L., Malv. 69.
nemorum, L., L., Crucif. 32.
Helodes aucta, F., L., Ran. 7.
phellandrii, L., L., Umb. 188;
Ran. 5.
Luperus flavipes, L, L., Ros. 148.
Plectroscelis dentipes, E. H., L., Crucif.
33.

D. Cistelide (2 species, 9 visits).

Cistela murina, L., L. T., Umb. 179, 185 ;
Ran. 7; Geran. 78; Ros. 149, 133 ;
Comp. 267.

— rufipes, F., L., Scroph. 324t.

E. Cleride (1 species, 5 visits).

Trichodes apiarius, L., L. T. Th., All.
392 ; Umb. 179, 191, 194, 174 ; Comp.
229.

F. Coccinellide (6 species, 14 visits).

Coccinella bipunctata, L., L., Comp. 234.

— mutabilis, Scrib., Th., Comp. 255.

14punctata, L., L., Umb. 190;
Berberid. 18; Cruc. 40; Parn. 157;
Ros.. 151.

—— 5punctata, L., L., Comp. 234.
—— 7punetata, L., L., Umb. 190;
Parn. 157 ; Geran. 83 ; Comp. 274.
Exochomus auritus, Scrib., L., Umb. 194;

Comp. 225.

G. Cryptophagidce (1 species, 2 visits).

Antherophagus pallens, Ol., L., Sld.,
Digit. 256 ; Camp. 278.

H. Curculionide (18 species, 24 visits).

Apion columbinum, Grm., L., Adoxa 198,

—— onopordi, K., L., Chrysospl. 155.

-—— yaripes, Grm., L., Chrysospl. 155.

— spec., L., Ros. 152.

Bruchus sp., L., Umb. 177, 185 ; Comp.
248, 234.

Ceutorhynchus pumilio, Gylh., L., Crue.

—— sp., L., Crue. 35.

Gymnetron campanule, L,, Sld., Camp.
277.

—— graminis, Gylh., Th., Camp. 282.

Larinus Jace, L., Th., Comp. 248, 246.

senilis, F., Th., Comp. 240.

Nanophyes lythri, F., L., Lythr. 165,

THE FERTILISATION OF FLOWERS.

Otiorhynchus ovatus, L., L., Camp. 277.

— picipes, F., L., Corn. 197.

Phyllobius maculicornis, Grm., L., Ros.
152.

Ph. oblongus, L., L., Umb. 177.

Rhynchites equatus, L., L., Ros. 151.

Spermophagus cardui, Schh., Th., Umb.
179, 195 ; Comp. 276.

I. Dermestide (6 species, 44 visits).

Anthrenus claviger, Er., L., Ros. 153,
149, 132.

—— museorum, L., L., Ros. 152, 133.

—— pimpinelle, F., L., Umb. 173, 179,
190, 194, 195, 186, 184, 174; Crue.
38; Rhus 88; Ros. 153, 148, 149,
138, 130, 132, 133 ; Comp. 229.

scrophularie, L., L., Umb. 186,
184; Ros. 148, 149, 153, 138, 132,
133.

Attagenus pellio, L., L., Berber. 18, Ros.
152, 153, 133.

Byturus fumatus, F. (including B. to-
mentosus, F.) L., Corn. 197; Ran,
7, 8; Geran. 78; Ros. 152, 184, 185,
137, 133.

K. Elateride (16 species, 36 visits).

Adrastus pallens, Er., L., Umb. 188.

Agriotes aterrimus, L., L., Umb. 179,
Ros. 152.

gallicus, Lap., Th., Umb., 195,
183; Rubiac. 206 ; Comp. 248, 228.

—— sputator, L., Th., Umb. 195.

—— ustulatus, Schall., Th., Umb. 194,
195; Comp. 248, 153.

Athous niger, L., L., Corn. 197 ; Umb.
179, 185 ; Comp. 229, 234.

Cardiophorus cinereus, Hbst., L., Ros.
133.

Corymbites hematodes, F., Siebengeb.,
Umb. 194.

—— holosericeus, L., L., Umb. 194
Ros. 152 ; Comp. 246.

quercus, Ill., L., Umb. 185.

Diacanthus eneus, L., L., Ros. 135.

Dolopius marginatus, L., L., Corn. 197 ;
Ros. 152.

Lacon murinus, L., L., Umb. 179, 185 ;
Ros. 133.

Limonius cylindricus, Payk., L., Ros, 152,
135.

—— parvulus, Pz., L., Crue. 38; Salix
878; Ros. 152.

Synaptus filiformis, F., L., Umb. 185.

L. Hydrophilide.
Cercyon anale, Pk., L., Crue, 33.

M. Lagriide.
Lagria hirta, L., L., Ros. 153.

INDEX OF INSECTS.

N. Lathridii.
Corticaria gibbosa, Hbst., L., Chrysospl.
155.

O. Lamellicornia (6 species, 39 visits).

Cetonia aurata, L., Sld. Th., Umb. 179,
193; Cruc. 32; Ros. 152, 148, 149,
130; Rubiac. 206; Sambuc. 199;
Comp. 229.

Hoplia philanthus, Sulz., Sld., Umb.
194 ; Scab, 211.

Melolontha vulgaris, L., L., Ros. 152,
149,

Phyllopertha horticola, L.,L., Umb. 179 ;

os. 148, 149, 133 ; Caprif. 200.

Trichius fasciatus, L., L. Sld., Umb. 179,
178, 187, 194, 195, 174; Clem. 1;
‘Thal. 2; Ros. 135, 130, 131, 133 ;
Caprif. 199; Scab. 211; Comp. 248,
246, 229, 237; Valer. 208.

—— nobilis, L., L., Comp. 229,

P. Malacodermata (13 species, 51 visits).

Anthocomus fasciatus, L., L., Umb. 177,
186 ; Cruc. 34, 38; Ros. 148, 149;
Plant. 362.

‘Dasytes flavipes, F., L., Umb. 179, 181;
Cruc. 38; Umb. 82; Ros, 138, 142,
133 ; Comp. 229.

—— pallipes, Pz., Th., Umb. 195.

is kugeeeys lv 1t, 08. 149;
Seroph. 323¢.

Malachius eneus, F., L. T., Umb, 185,
186 ; Geran. 78 ; Ros. 152; Plant. 368 ;
Comp. 229.

——- bipustulatus, F., L. T. Sld., Umb.
179, 185; Crue. 38; Ros. 135, 138,
133 ; Papil. 119+, Comp. 274, 260.

sp., L., Comp. 276.

Telephorus fuscus, L., L., Umb. 179, 194,

185.
— lividus, L., L., Umb. 194, 185,
186.

— melanurus, L., L. Sld., Umb. 181,
178, 190, 194 ; Comp. 248.

—— pellucidus, F., L., Corn. 197.

— rusticus, F, L., Umb. 177, 185;
Ros. 135.

— testaceus, L., L., Ros. 153.

Q. Mordellide (9 species, 35 visits).

Anaspis frontalis, L., L., Umb. 179, 186 ;
Ros. 158, 148, 133.

— maculata, Fourc., L., Ros. 133.

— rufilabris, Gylh., T., Umb. 179; Ros.
152.

—— ruficollis, F., L., Ros. 149.

Mordella abdominalis, F., L., Ros. 153.

— aculeata, L., L., Umb. 179, 195;
Ran. 7 ; Ros. 148, 149, 138, 130, 133 ;
Rubiac. 206 ; Caprif. 200 ; Comp. 248,
229.

637

Mordella fasciata, F., L., Umb. 179, 178,
194; 195, 185; Rubiac. 206 ; Comp.
248, 229, 228, 265.

gh ri Gylh., L., Umb. 185 ; Ran.

—— pusilla, Dej., L., Ran. 7.

R. Nitidulidae (4 species, 65 visits).

Cychramus luteus, F., Sld. T., Umb. 179;
Ros. 130.

Epurea, sp., L., Umb. 185; Crue. 35 ;
Ros, 152.

Meligethes sp., L., Lil. 394 ; Cypriped.
386* ; Corn. 197 ; Umb. 190, 194, 185,
186, 184, 174; Nuph. 19; Ran. 4, 7,
8, 9, 11; Papav. 20; Cruc. 30, 35, 39;
Salix 378 ; Oxalis 75 ; Cary. 65, 63;
Lythr, 165 ; Onagr. 167 ; Ros. 151, 152,
158, 148, 149, 135, 188, 139, 142, 136,
132, 133, 127, 128; Papil. 111, 112:
Convoly. 311+; Bor. 300; Scroph. 323+;
Plant. 368 ; Caprif. 200; Scab. 211 ;
Camp. 278, 280 ; Comp. 229, 233, 217,
236, 263, 274; Valer. 209.

Thalycra sericea, Er., L., Corn. 197;
Umb. 194.

S. Bdemeride (3 species, 12 visits).
Asclera ccerulea, L., L., Ros. 153.
(Edemera flavescens, L., L. Th., Umb.

182.

—— virescens, L., L. T. Th., Umb. 183,
194; Ran.7; Cary. 65; Ros. 135;
Convolv. 311; Ech. 310; Jas. 283 ;
Comp. 238, 217.

T. Phalacride (3 species, 4 visits).
Olibrus eneus, F., L., Chrysospl. 155 ;
Ros. 151.
—— affinis, Sturm, L., Cary. 67.
—— bicolor, F., L., Scab. 211.

U. Staphylinide (2 species, 7 visits).

Anthobium spec., Sld., Papil. 112;
Camp. 277.

Omalium florale, Pk., L., Crue. 30;
Cerast. 60; Pulm. 304; Prim. 288.

V. Tenebrionide.
Microzoum tibiale, F., L., Ros. 152.

II. DIPTERA (253 species, 1598 different
visits).

BRACHYCERA (282 species, 1557 different
visits).
A, Asilide (3 species, 3 visits).

Dioctria atricapilla, Mgn., T., Ran. 7.
— Reinhardi, Wiedem., Sld., Umb.
194. ?

638 THE FERTILISATION OF FLOWERS.

Isopogon brevirostris, Fall., Sld., Umb.
_ 181,

_ B. Bombylide (9 species, 57 visits).

Anthrax flava, Mgn., Sld. Th., Umb.
179, 175, 198, 194, 195 ; Rubiac. 205 ;
Comp. 248.

hottentotta, L., Sld., Comp. 237.

maura, L., Th., Umb. 191, 192.

Argyromeeba sinuata, Fall., L. T., Cruc.
38 ; Hyper. 68*.

Bombylius canescens, Mik., Th., Hyper.

_ 68; Comp. 267.

discolor, Mgn. (11—12), L., Coryd.

23t, 24; Cruc. 30; Viol. 47, 48;

Bor. 304 ; Lab. 349; Vinea, 293; Prim.

288.

major, L. (10), L. T., Umb. 182;
Coryd. 23t, 24+; Cruc. 30; Viol. 49;
Salix 378, 379; Ros. 150; Bor. 304,
306 ; Lab. 362, 349; Vinca, 293 ; Syr.
291 ; Prim. 282 ; Comp. 236.

Exoprosopa capucina, F., L , Scab. 212 ;
Jas. 282 ; Comp. 225.

Systechus sulfureus, F., Sld. Th., Lin.
74; Malv. 72; Ros. 143 ;. Papil. 100*,
94+; Scroph. 317, 330; Lab. 344, 340 ;
Rubiac. 205, 207 ; Camp. 277 ; Comp.
229, 271, 272.

' -C. Conopide (13 species, 54 visits).

Conops flavipes, L. (4—5), L. Sld. T.,
Papil. 90+; Phlox, 299; Lab. 350;
Rubiac. 206; Comp. 257, 248, 229.

quadrifasciatus, Deg., L., Umb.

scutellatus, Mgn., Th., Comp. 246.

Myopa buccata, L. (45-5), L., Salix
377, 378 ; Papil. 987, 95.

polystigma, Rond., L., Ros. 133 ;

Lab. 342.

testacea, L. (33), L. Sld. Th., Salix

377 ; Ros. 152; Papil. 95+, 98, 108* ;

Lab. 340.

- variegata, Mgn., L., Lab. 342.

sp., Th., Comp. 255.

Occemyia atra, F., T., Comp. 266.
Physocephala rufipes, F., L. Th., Ros,
135, 133 ; Jas. 283 ; Comp. 248, 246.
—— vittata, F., L., Ech. 310 ; Jas, 283 ;

Comp. 257, 225.

Sicus ferrugineus, L., L. Sld. T., Ros.
142; Papil. 100*, 108* ; Lab. 340, 342;
Seab, 211, 213; Jas. 283 ; Comp. 253,
229, 237, 266, 265, 276, 271, 272, 270,
260; Valer. 208.

Zodion zinereum, F., Sld., Umb. 194.

D. Dolichopide (2 species, 2 visits).
Dolichopus eneus, Deg., L., Umb. 178.
Gymnopternus cherophylli, Mgn., L.,

Umb, 191.

E. Empide (13 species, 81 visits).

Empis leucoptera, Mgn , L., Hott. 289.

— livida, L. (24—3, dry), L., All. 393;
Orch, 386 ; Corn. 197.; Umb. 179, 187,
194; Ran. 8; Papav. 21; Cruc. 27,
28; Hyper. 68; Lin. 74; Cary. 61;
Onagr. 166; Ros. 150, 152, 153, 135,
138, 128; Papil. 117; Convolv. 311 ;
Scroph. 326; Lab. 342, 338; Hott.
289 ; Scab. 211, 212 ; Jas. 283 ; Comp.
259, 248, 249, 233, 238, 217, 274, 262 ;
Valer. 208.

opaca, F. (3—34, dry), L., Crue.

30 ; Cary. 65, 60 ; Ros. 133 ; Bor. 307 ;

Caprif. 204 ; Comp. 217, 274.

pennipes, L., L., Hottonia 289.

—— punctata, F., L., Cyprip. 386* ;
a 179, 185; Ros. 133; Comp.
274,

— rustica, Fall., L., Umb. 187;
Cary. 60; Onagr. 166; Ros. 152, 127,
128 ; Lab. 342, 338; Comp. 257, 229 ;
Valer. 208.

stercorea, L., L., Umb. 185,

tesselata, F. (3—33, dry), L.,

Umb. 182; Ran. 7; Cary. 65; Ros.

135, 133 ; Lab. 338 ; Scab. 211 ; Comp.

237.

sp.. L., Umb. 178; Salix 378;
Convolv. ;

Microphorus velutinus, Macq., L., Ros.
153

Rhamphomyiaplumipes Fall., L., Camp.
277.

suleata, Fall., L., Salix 378.
Tachydromia connexa, Mgn., L., Ros.
153.

F. Leptide (2 species, 2 visits).

Atherix ibis, F., L., Umb. 187.
Leptis strigosa, Mgn., L., Cary. 60. —

G. Muscide (85 species, 387 visits).

Alophora hemiptera, F., T., Umb. 190.
Anthomyia estiva, Mgn., L., Cary. 60.
—— obelisea, Mgen., L., Rut. 84.
pratensis, Mgn., L., Rut. 84.

— radicum, L., L., Umb. 186; Ran.
10 ; Rut. 84; Ros. 151.

—— sp., L., Cyprip. 386*; Umb. 172,
179 ; Ran. 6, 7, 8, 10, 11; Berb. 18;
Crue. 30, 37 ; Geran. 76 ; Cary. 63, 55;
Onagr. 170; Ros. 138, 142, 145, 130,
132, 138, 127: Plant. 96.

Aricia incana, Wiedem., L., Umb. 178 ;
Comp. 238.

—— obscurata, Mgn., L., Umb. 179.

—— serva, Mgn., L., Ros. 153.

—— vagans, Fall., L., Umb. 188.

Borborus niger, Mgn., Adoxa 198.

Calliphora erythrocephala, Mgn., L.,
Gross. 161; Umb. 194; Salix 378 ;

INDEX OF

Rhus. 88 ; Rut, 84; Ros. 151 ; Seroph,
_ 829; Valer. 208.
Calliphora vomitoria, L., L., Umb. 178,
194, 174; Euon. 85; Valer. 208.
Calobata cothurnata, Pz., L., Bor. 305.
Chlorops circumdata, Mgn., L., Cary.
66

—— sp., L., Ros, 153, 127.
Cyrtoneura ccerulescens, Macq., L., Ran.

—— curvipes, Macq., L., Umb. 188,
192.

—— simplex, Loew, L., Umb, 176, 178,
192, 186 ; Ros. 133.

—sp., L., Ros. 153.

Demoticus plebejus, Fall., L., Comp.
270.

Dexia canina, F., T., Comp. 214.

— rustica, F., Th., Umb. 193.

Echinomyia fera, L., L. T., Umb. -172,
179, 177, 190, 194, 185; Geran. 78 ;
Ros. 152, 153, 134; Caprif. 2C0 ; Comp.
214.

—— ferox, Pz., L., Jas. 283 ; Comp. 226.

— grossa, L., L., Umb. 194.

— magnicornis, Zett., L. T. Th., Sed.
164 ; Umb. 194 ; Ros. 133.

— tesselata, F., L., Bor, 305; Lab.
335 ; Scab. 317 ; Jas. 283 ; Comp. 245,
229, 227.

Exorista vulgaris, Fall., L., Umb. 194,
186.

Gonia capitata, Fall. (4—5), L., Comp.
225.

Graphomyia maculata, Seop., L., Umb.
194, 185 ; Ros. 154.

Gymnosoma rotundata, L., L. Th., Umb.
177, .191, 192, 196, 195, 186, 184;
Lab. 133 ; Comp. 225, 228.

Helomyza affinis, Mgn., L., Neottia 381.

Hydrotea dentipes, F., L., Cary. 65.

Lucilia albiceps, Mgn., L., Ros. 133 ;
Comp. 214.

— cesar, L, L, Umb. 172, 178,

. 194, .

— cornicina, F., L., Umb. 173, 176,
179, 178, 188, 192, 194, 174; Euon.
86; Rhus 88; Rut. 84; Til. 73;
Fagop. 369 ; Ros. 151, 142, 133 ; Lab.
340, 339, 337 ; Scab. 212 ; Comp. 248,
229, 233, 217 ; Valer. 208.

— sericata, Mgn., L., Umb. 194,
185 ; Comp. 248,

—— silvarum, Mgn., L., Umb. 179, i78,
190, 193, 194; Rut. 84; Cary. 55;
Ros. 142, 133 ; Lab. 339, 337 ; Comp.
229.

spec., L, Umb. 179, 185, 195;

Ascl. 295t ; Scab. 212; Comp. 222,
238. es

Macquartia prefica, Zett., L., Comp.
229.

Mesembrina meridiana, L., I.., Umb. 178,
190; Ros. 142, 133.

INSECTS. 639

Micropalpus fulgens, Mgn., L., Scab,
211.

Miltogramma punctata, Mgn., L., Umb.
173, 179.

Musca corvina, F., L., Umb. 178, 179,
185, 192, 194 ; Berb. 18 ; Fagop. 369 ;
Cary. 66; Ros, 151, 138, 133; Bor.
305; Lab. 338; Rubiac. 205; Comp.
248, 229, 217.

—— domestica, L., L., Ran. 12; Berb.
18; Euon. 85; Til. 73; Cary. 66;
Onagr. 170 ; Ros. 151; Valer. 208.

Myodina vibrans, L , L., Aristol. 376.

Nemorea sp., L., Umb. 194.

Ocyptera brassicaria, F., L., Umb. 178,
194; Lab. 340, 342; Ascl. 295; Jas.
283 ; Comp. 248.

—— cylindrica, F., L., Lab. 342; Scab.
211; Jas. 283 ; Comp. 248, 225, 221.
Oliviera lateralis, Pz., L., Jas. 283;

Comp. 248, 238.

Onesia cognata, Mgn., L., Berb. 18 ; Ros.

139, 133.

—~floralis, R. D., L., Umb. 194; Nuph.
19; Berb. 18; Cary. 55; Ros. +150,
152, 153, 135, 139, 1383; Bor. 305,
306, 307; Lab. 337, 338 ; Comp. 248,
238, 274; Valer. 207.

—— sepulcralis, Mgn., Th., Umb. 198,
194; Berb. 18; Ros. 153; Bor. 305;
Lab. 337, 338 ; Comp. 237.

Phasia analis, F., Th., Umb. 191.

—— crassipennis, F., Th., Umb, 191.

Phorocera assimilis, Fallen, L., Umb.
194.

Platystoma seminationis, F., Comp. 248.

Pollenia rudis, F., L., Umb. 179; Ran.
12; Rut. 84; Salix 378; Cary. 62;
Ros. 151; Comp. 222.

Vespillo, F., L., Thalict. 3; Parn.
157; Fagop. 369; Cary. 62; Ros.
151, 139; Bor. 305; Lab. 839 ; Comp.
229, 233, 238.

Prosena siberita, F., (6, dry) L., Clem. 1;
Lab. 342.

Psila fimetaria, L., L., Umb. 185.

Pyrellia enea, Zett., L., Sed. 162 ; Umb.
194; Comp. 229.

—— cadaverina, L., L., Cary. 55 ; Lab.
337.

Sapromyza apicalis, Loew, L., Arist. 376.

Sarcophaga albiceps, Mgn., L., Umb.
179, 177, 195; Rut. 84; Ros. 133;
Lab. 340, 339, 337.

earnaria, L., L. Th., Umb. 172,
176, 177, 193, 194 ; Parn. 157 ; Euon.
85; Rhus 88; Rut. 84; Til. 73;
Fagop. 369;. Polyg. 370; Cary. 55;
Ros. 153, 142, 183; Lab. 340, 338;
Comp. 248, 233, 223.

——- dissimilis, Mgn., L., Umb. 186.

— hemarrhoa, Mgn., L., Umb.. 186,
194; Rut. 84; Comp. 235.

——spec., L., Umb. 185, 190 ; Lab, 338.

640

Scatophaga merdaria, F., L., Gross. 158 ;
Umb. 172, 190, 194, 185 ; Ran. 4, 5, 6,
9, 10, 11; Salix 378 ; Ros. 151, 152,
142, 127; Bor. 305; Rubiac. 205;
Comp. 248, 227, 234, 217, 274.

stercoraria, L., L. T., Gross. 158,
161; Umb. 179, 190, 185, 174; Ran.
4; Salix 378; Euon. 85; Geran. 78,
80; Ros. 127 ; Scroph. 325; Comp.
248, 229, 227, 217, 274.

Sciomyza cinerella, Fallen, L., Chrysospl.
155.

Sepsis cynipsea, L., L., Umb. 194.

putris, L., L., Cruc. 33.

—— spec., L., Umb. 179, 178, 192, 195,
185, 186, 174; Ran. 9,12; Rut. 84;
Cary. 60; Ros. 151, 152, 142, 127 ;
Convolv. 311}; Comp. 229.

Siphona cristata, F., L., Cruc. 38.

Spilogaster nigrita, Fall., L., Comp. 233.

semicinerea, Wied., L., Cypr. 386* ;
Neott. 381+; Plant. 368.

Tachina erucarum, Rond., L., Umb. 194.

—— prepotens, Mgn., L., Umb., 190.

' Tetanocera ferruginea, Fall., L., Umb.
178.

Trypeta cornuta, F., Th., Comp. 258.

Ulidia erythrophthalma, Mgn., Th.,
Comp. 231, 228.

Zophomyia tremula, Scop., L., Umb. 177,
185.

H. Stratiomyide (11 species, 45 visits).

Chrysomyia formosa, Scop., L. T., Umb.
179, 177, 192, 184; Ros. 185; Plant.
368.

polita, L., Th., Samb. 199.

Nemotelus pantherinus, L., L. T., Umb.
185; Cruc. 34; Comp. 229, 233, 227,
268.

Odontomyia argentata, F. (2—3), L.,
Ran. 11; Fagop. 369 ; Cary. 60; Ros.
139.

-— viridula, F., L , Umb. 188 ; Fagop.
369 ; Lab. 337 ; Rubiac. 206 ; Comp.
248, 225, 229, 234, 238.

Oxycera pulchella, Mgn., Sld., Melamp.
335*.

Sargus cuprarius, L., L., Umb. 179, 154 ;
Rut. 84; Malv. 69; Ros. 135, 142;
Caprif. 199.

Stratiomys Chameleon, Deg., L. Th.,
Umb. 179, 187, 195, 185; Fagop.
369.

longicornis, F., L., Umb. 177.

Fagop. 369 ; Ros. 127.
spec., L., Cary. 60.

I. Syrphide (89 species, 916 visits).

Ascia lanceolata, Mgn., L., Ros, 127;
Comp. 274.

riparia, Mgn., L., Umb. 178, 195 ;

THE FERTILISATION OF FLOWERS.

Ascia podagrica, F., L. T., Alism. 398 ;
Umb. 194, 195, 185 ; Ran. 11 ; Chelid.
21; Cruc. 33, 37, 38; Cist. 45;
Hyper. 68; Rut. 84; Geran. 78, 79,
81; Polygon. 371, 372, 873, 374;
Cary. 63, 55; Onagr. 170; Ros. 151,
135, 142, 145, 133 ; Scroph. 319, 325,
326; Lab. 342, 338; Plant. 368;
Comp. 238, 274.

Bacha_ elongata,
Onagr. 170.

Brachypalpus valgus, Pz., L., Ran. 9:
Salix 8378 ; Ros. 149.

Cheilosia spec., L., Lil. 394 ; Cypr. 386*,
Umb. 184; Ran. 6, 8, 11 ; Papav. 20 ;
Ros. 143 ; Comp. 272, 275.

albitarsis, Mgn., L., Ran. 7.

—— barbata, Loew, L., Ros. 127.

brachysoma, Egg., L., Salix 378.

eae tes Mgn., L., Salix 878 ; Comp.

——chrysocoma, Mgn., L. T., Comp. 263,
264, 365, oh ‘

fraterna, Mgn., L., Comp. 229. -

— Egg., L., Salix 378; Ros.

pictipennis, Egg., L., Salix 378.

preecox, Zett., T., Salix 378; Ros.
139 ; Comp. 238.

—— pubera, Zett., L., Ran. 7.

F., L., Umb. 184;

—— scutellata, Fall., L. Sld. T., Umb.

Si 194, 184; Fagop. 369; Eric.
287.

—— soror, Zett., L., Umb. 195 ; Comp.
238.

—— vernalis, Fall., L., Ran. 10 ; Comp.
4

274.
Chrysochlamyscuprea, Scop., L., Papav.
20.

—— ruficornis, F., L. Sld., Camp. 278.

Chrysogaster enea, Mgn., T., Cruc. 34.

chalybeata, Mgn., T., Umb. 179.

—— ceemeteriornm, L., L. T., Umb. 179,
184.

<< Macquarti, Loew, L., Ran. 7 ; Crue.
2

—— viduata, L., L., Umb. 179, 194, 195;
Ran. 5,7: Ros. 149, 127; Bor. 306;
Comp. 262.

Chrysotoxum arcuatum, L., Sld., Ran. 7;
Ros. 135.

—— bicinctum, Pz., Sld. T., Umb. 198,
194 ; Geran. 79; Ros. 148 ; Pap. 108.

festivum, L., L. T., Umb. 192, 194 ;
nam 7 ; Fagop. 369 ; Ros. 127 ; Valer.

—— octomaculatum, Curt.,
287.

Eristalis eneus, Scop., L., Gross. 161;
Umb. 177, 178, 194; Crue. 40; Cary.
55; Ros. 149 ; Lab. 838; Jas. 283 ;
Comp. 251, 229, 238, 274.

—— arbustorum, L. (4—5), L. Sld. T,
Th., Umb, 178, 172, 176, 179, 177,

T., Eric.

INDEX OF INSECTS.

175, 187, 188, 192, 194, 195, 185, 186 ;
Clem. 1; Thal. 2, 3; Ran. 5, 7; Berb.
18; Cruc. 27, 28, 38, 40; Parn. 157 ;
Salix 378 ; Hyper. 68 ; Til. 73 ; Fagop.
369 ; Polygon. 371 ; Cary. 65, 60, 63,
55; Ros. 151, 152, 153, 142, 130, 131,
133, 127, 129 ; Convolv. 311; Bor. 305 ;
Scroph. 317; Lab. 340, 342, 338 ; Ascl.
295; Ol. 291; Plant. 368; Hott. 289;
Eric, 285 ; Caprif. 200, 199 ; Scab. 211,
212 ; Jas. 283; Comp. 259, 248, 250,
246, 225, 229, 233, 227, 228, 234, 237,
238, 223, 221, 215, 216, 217, 218, 219,
214, 266, 263, 275, 276, 262, 271, 272,
273, 270, 261; Valer. 208, 209 (alto-
gether 91 visits.)

Eristalisintricarius, L., L., Ran. 11; Salix
105; Fagop. 369; Ros. 151, 153, 133,
127 ; Lab. 349; Eric. 285 ; Scab. 211,
212; Comp. 248, 274.

— sesvtiachas Mgn., L. Sld., Orch. 18 ;
Umb. 177, 181, 194; Ros. 152, 130;
Eric, 285 ; Samb. 198 ; Comp. 229, 237,

* 271, 272; Valer. 208.

— nemorum, L., L. Sld. T. Th., Umb.
172, 178, 179, 187, 192, 194, 186, 184 ;
Thal. 2,3; Ran. 5, 7; Berb. 18 ; Cruc.
34, 37, 38; Parn. 157 ; Hyper. 68 ; Til.
73; Fagop. 369 ; Cary. 55, 60 ; Onagr.
169 ; Ros. 151, 152, 153, 148, 180, 131,
133, 127 ; Seroph. 317 ; Lab. 365, 340,
342, 338; Ascl. 295; Ol. 292; Hott.
289 ; Caprif. 199, 200 ; Scab. 211, 212,
213; Comp. 258, 248, 250, 225, 229,
283, 227, 234, 237, 238, 221, 205, 216,
218, 214, 268, 274, 262, 270, 261; Valer.
208 (altogether 65 visits).

pertinax, Scop., L., Umb. 190, 194,

185, 183; Salix 378; Fagopyr. 369 ;

Ros. 153, 183 ; Comp. 217, 274.

sepulcralis, L., LL. Sld. Th., Alism.

398 ; Umb. 176, 187, 192, 194, 195;

Clem, 1; Thal. 2,3 ; Ran. 7 ; Cruc. 38;

. Hyper. 68 ; Rut. 84; Til. 73 ; Polygon.

369, 371, 372 ; Cary. 60 ; Ros. 153, 135,

138, 142, 145, 130, 188; Bor. 305;

Scroph. 246 ; Lab. 340, 337, 338; Ol.

291 ; Caprif. 200 ; Scab. 212; Comp.

248, 225, 229, 233, 227, 288, 223, 217,

263, 274, 262, 271, 270, 261; Valer.

207 (altogether 48 visits).

tenax, L. (7—8), L. Sld. Th., Sed.
162, 163 ; Umb. 172, 192, 194; Thal.
2, 3; Ran. 7; Berb. 18 ; Cruc. 32, 35 ;
Sal. 378 ; Hyper. 68 ; Euon. 85 ; Geran.
76; Til. 73 ; Polygon. 369, 371 ; Onagr.
169 ; Ros. 151, 153, 135, 130, 133, 129 ;
Phlox. 299; Solan. 312; Ascl. 396 ;
Caprif. 200, 199; Scab, 211, 212, 213 ;
Jas. 283; Comp. 248, 250, 253, 245,
249, 227, 224, 238, 217, 236, 214, 266,
268, 265, 274, 276, 262, 271, 273, 260 ;
(altogether 55 visits).

Eumerus sabulonum, Fall., L., Jas. 283,
Comp. 225.

641

Helophilus floreus, L., L., Umb. 172, 176,
179, 177, 178, 190, 194, 195, 185, 184;
Clem. 1; Ran. 5; Berber. 18; Cruc,
32, 38; Parn. 157; Euon. 85; Rhus
88; Rut. 84; Geran. 78; Til. 369;
Fagop. 73; Ros. 152, 153, 148, 142,
130, 131, 138 ; Convolv. 311 ; Scroph.
319, 326; Caprif. 200; Scab. 212;
Comp. 229, 267 ; Valer. 208.

-— lineatus, F., L., Ran. 7 ; Cary. 63 ;
Lythr. 165,

pendulus, L., L., Umb. 177 ; Berb.
18 ; Cruc. 30; Cist. 45; Hyper. 68 ;
Rhus 88; Geran. 76, 80; Cary. 52;
Lythr. 165; Ros. 158, 185, 142; Lab.
282, 285 ; Caprif. 200 ; Scab. 212; Jas.
283 ; Comp. 257, 229; Valer. 208.

—— trivittatus, F. (6—7), L. Th.,
Hyperic. 68 ; Lythr. 165; Papil. 94 ;
Ech. 310; Lab. 338; Scab. 213.

Melanostoma ambigua, Fall., L., Ech.
310.

— mellina, L., L. T., Alism. 19 ; Umb.
177, 184; Ran. 7; Cruc. 32; Pain.
157 ; Hyperic. 68; Cary. 60; Onagr.
170 ; Ros, 145, 151 ; Papil. 90 ;Scroph.
324; Lab, 356, 338 ; Plant. 367, 368;
Jas. £83 ; Comp. 222. This species is
remarkable for its predilection for
anemophilous flowers ; I have seen it
visit not only the species of Plantago,
but also Scirpus palustris, Artemisia
Dracunculus, and many Graminez.

Melithreptus menthastri, L., L., Umb.
194; Parn. 157 ; Polygon. 373, 374;
Ros. 138 ; Jas. 283; Comp. 232.

—— pictus, Mgn., L. T., Umb. 185;
Ran. 7 ; Cruc. 37 ; Hyper. 68 ; Rut. 84 ;
Geran. 77, 78 ; Polygon. 373; Cary. 52,
55 ; Ros. 145.

—— scriptus, L., L. Sld., Alism. 398 ;
Umb. 195, 185, 184; Ran. 7; Cruc.
37 ; Parn. 157 ; Cist. 45 ; Hyperic. 68 ;
Geran. 76; Polygon. 369, 371; Cary.
52; Ros. 148, 145, 137 ; Convolv. 310 ;
Solan. 314 ; Lab. 339, 337 ; Ascl. 296+ ;
Eric. 287 ; Jas. 283; Comp. 225, 222,
223, 217, 265, 262.

—— strigatus, Steg., L., Ros. 133.

—— teniatus, Mgn., L. T. Th., Umb.
179, 177, 195; Ran. 6, 7; Cruc,, 37,
88; Parn. 157 ; Cist. 45; Geran. 78 ;
Polygon. 369, 371; Cary. 55, 165;
Ros. 142, 145 ; Convolv. 311; Scroph.
830; Lab. 358, 337 ; Ascl. 295+; Comp.
248, 225, 229, 228, 234, 265, 274, 262,
271, 272.

spec., L., Cruc. 33.

Merodon eneus, Mgn., Th., Antheric.
391.

Pelecocera bicincta, Mgn., T., Ger. 78.

Pipiza chalybeata, Mgn., L., Ran. 7;
Cruc. -38. ~: Ritak wk

-—— funebris, Mgn., L., Umb. 195; Ran.

¢ Ow

642

7; Fagopyr. 369; Ros. 133; Comp.
270, 261.

Pipiza lugubris, F., L., Comp. 229.

notata, Mgn., L., Ros. 153.

Pipizella annulata, Macq., L., Umb. 175,
194, 195.

virens, F., L. T., Umb. 179, 177,

190, 194; Ran. 10.

spec., L., Jas. 283.

Platycheirus albimanus, F., L. T., Ran.
7; Bor. 306.

manicatus, Mgn., L., Cary. 60.

peltatus, Mgn., L., Umb.177 ; Geran.
76; Cary. 65.

Pyrophena sp., L., Umb. 177.

Rhingiarostrata, L. (including campestris,
Mgn.)(11—12), L., Lil. 390* ; Ir. 387+ ;
Thal. 2; Ran. 11 ; Berb. 18 ; Papav. 21;
Crue, 28, 30, 34, 35, 40 ; Geran. 76, 78,
79, 80 ; Malv. 69; Polygon. 370 ; Cary.
65, 62, 52*, 57,59* ; Lythr. 165; Ros.
150, 152, 153, 148, 134, 135, 138, 139,
145, 136, 133, 129; Papil. 112; Bor.
310, 300, 304, 305 ; Solan. 313 ; Scroph.
318, 324; Lab. 366, 359+, 361*, 352,
353, 349; Ol. 291; Plant. 368; Hott.
289 ; Eric. 285 ; Caprif. 202, 203, 204 ;
Scab. 211, 212; Camp. 279; Comp. 257,
259, 217, 274; Valer. 209 (67 visits).

rie borealis, Fall., T. Th., Eric.
287.

lappona, L., Sld., Comp. 272.

Syritta pipiens, L., L. Sld Th., Alism.
398 ; Gross. 158, 161; Umb. 176, 179,
177, 178, 175, 187, 188, 190, 192, 193,
194, 195, 185, 186, 184; Clem. 1; Thal.
3; Ran. 6, 7 ; Papav. 21; Cruc. 27, 28,
37, 38; Res, 42; Parn. 157; Viol. 46 ;
Salix 378; Euon. 85; Rhus 88; Rut.
84; Geran. 80; Polygon. 369, 370*,
371, 372, 373, 374; Cary. 66, 60, 61, 63,
55; Lythr. 165; Ros. 151, 148, 149,
135, 138, 139, 142, 145, 130, 131, 133 ;
Bor. 305 ; Solan. 312, 318 ; Scroph. 317,
319, 325, 326; Lab. 340, 339, 337, 338 ;
Ol. 291; Prim. 290 ; Eric. 287 ; Rubiac.
205; Jas. 283; Comp. 248, 225, 229,
233, 227, 228, 234, 238, 220, 216, 217,
263, 269; Valer, 207 (89 visits).

Syrphus arcuatus, Fall., L. T., Umb.
177 ; Ros, 140 ; Bor. 310 ; Comp. 265,
275.

balteatus, Deg. (2), L. T., Papav.
21; Cruc. 37; Parn, 157; Salix 378;
Hyper. 68; Geran. 78; Cary. 55;
Convolv. 311 ; Plant. 368 ; Camp. 278 ;
Comp. 266, 265, 275, 262, 271, 273.

-— corolle, F., L., Umb. 185; Comp.
229.

decorus, Mgn., T., Cruc. 35.

excisus, Zett., L., Parn. 157 ; Ros.
133.

—— glaucius, L., L., Umb. 194.

-—— nitidicollis, Mgn., (3), L. T., Umb.

THE FERTILISATION OF FLOWERS.

179, 181 ; Rut. 84 ; Ros. 179 ; Convolv.
311; Comp. 229, 274, 271.

Syrphus ochrostoma, Zett., L., Caprif.
202.

—— pyrastri, L., L. T., Umb. 179, 177,
181, 192, 194, 195; Clem. 1; Parn.
157 ; Cist. 45; Salix 378 ; Geran. 78;
Fagopyr. 369 ; Cary. 57 ; Ros. 150; Bor.
310 ; Lab. 338; Scab. 212; Jas. 283;
Comp. 224, 274, 271.

ribesii, L. (3—4), L. T., Umb. 179,

177, 178, 194, 185 ; Ran. 7; Parn. 157;

_ Cist. 45 ; Salix 378 ; Hyper. 68; Euon. .

85 ; Rut. 84 ; Geran. 78 ; Polygon. 370 ;
Cary. 65 ; Onagr. 166 ; Ros. 133 ; Plant.
367 ; Rubiac. 205; Scab. 311; Comp.
224, 234, 237, 265.

—— umbellatarum, Mgn., Sld., Comp.
237.

— spec., L., Cruc. 27 ; Cary. 60 ; Ros.
138, 139 ; Scroph. 330 ; Eric. 287 ; Comp,
248, 263.

Tropidia milesiformis, Fall., L.,

Volucella bombylans, L. (7—8), L. Sld. T.,
Orch. 390 ; Polyg. 370; Cary. 64 ; Ros.
147, 130; Pap. 98, 100*; Lab. 850;
Eric. 286 ; Scab. 211 ; Jas, 283 ; Comp.
253, 225, 237, 271; Valer. 208.

—— hemarrhoidalis, Zett., L., Eric.
286.

pellucens, L., L. T. Sld., Umb.
178 ; Cruc, 34; Til. 73 ; Ros. 134, 135;
Plant. 367; Samb. 199; Scab. 211;
Comp. 225, 229, 237, 270.

— plumata, L., L., Cary. 57 ; Lythr.
165; Ros. 133; Pap. 116; Eric. 286;
Seab. 211.

Xanthogramma citrofasciata, Deg., L.,
Umb. 176 ; Euon. 85; Ros. 144.

Xylota femorata, L., T., Umb. 182.

florum, F., Sld.; Umb. 194.

—— ignava, Pz., L., Clem. 1; Ros. 133.

— lenta, Pz., L., Clem. 1 ; Ros. 133.

— segnis, L., L., Ros. 158, 133; Ol.

291*, Caprif. 202.
silvarum, L., Sld., Lab. 352*.

K. Tabanide (4 species, 9 visits).
Chrysops cecutiens, L., L., Umb. 181 ;
Cary. 55; Ros. 142; Lab. 285.
Tabanus luridus, Pz., L., Valer. 208.
micans, Mgn., L., Umb. 181.
—— rusticus, L., L., Sld. Th., Umb,
194; Comp. 248, 225.

L. T'herevide (1 species, 1 visit).
Thereva, anilis, L., L., Umb. 179.

NEMATOCERA (22 species, 41 visits).

M. Bibionide (5 species, 12 visits).
Bibio hortulanus, F., L. T., Umb. 177,

185, 186; Euon. 85; Ros. 133.
Johannis, L., L., Salix 378,

— le

ee

~~

INDEX OF INSECTS.

Marci, L. L., Salix 378 ; Ros. 153,
2

Dilophus vulgaris, Mgn., L., Ros. 150,
152, 153.
Scatopse soluta, Loew, L., Aristol. 375.

N. Cecidomyide (2 visits).
bi, caramel Adoxa 314 ; Chrysospl.

O. Chironomide (8 species, 4 visits).
ia a sp., L., Aristol. 375; Ros,
Chironomus sp., L., Aristol. 375.
Undetermined genus, Chrysospl. 155.

P. Culicide (1 species, 1 visit).
Culex pipiens, L., L., Rhamn. 86.
Q. Mycetophilide (5 visits).

ee: Adoxa 314; Chrysospl.

155.

Platycera sp., L., Umb, 194.

Sciara Thome, L., L. Th., Umb. 172;
Comp, 238.

R. Psychodide (1 species, 1 visit).

Psychoda phalenoides, L., L., Arum
391.

S. Simulide (2 visits).

Simulia spec., Adoxa 198; Chrysospl.
155. ,

T. Tipulide (5 species, 13 visits).

Tipula oleracea, L., L., Parn. 157 ; Ros.
135.

—— spec., L., Umb. 177, 192; Valer.
390.

Pachyrrhina crocata, L., L. Sld. T., Umb.
179, 181, 185; Rubiac. 205.

—— historio, F., L., Umb. 179, 194.

—— pratensis, L., L., Umb. 185 ; Ros.
1338.

III. HEMIPTERA (6 species, 15 visits).
Anthocoris sp., L., Umb. 178; Salix
378

Capsus sp., L. Th., Umb. 194; Lythr.
165; Papil. 91+; Comp. 258, 255,
231, 228, 238.

Nabis sp., L., Convolv. 311f.

Pyrocoris aptera, L. (4), L., Comp. 274.

Tetyra nigrolineata, L., Th., Umb. 195.

Undetermined genus, L., Umb. 194;
Comp. 234.

~

643

IV. HYMENOPTERA (368 species,
2,750 different visits).

A. Apide (205 species, 2,191 different
visits).

Andrena (51 species, 219 different visits).

Andrena albicans, K. (2—24), L. T.,
Cypr. 386; Gross. 158, 161; Umb.
179, 177; Clem. 1; Ran: 4, 7, 9, 11;
Berber. 18; Coryd. 22+; Cruc. 34;
Viol. 46* ; Salix 378, 379; Rhus 88;
Polygon. 370; Cary. 66, 60; Ros.
150, 151, 152, 153, 148, 149, 139, 133,
127, 129; Papil. 111; Myos. 305,
806 ; Lab. 359t, 349*; Caprif. 203* ;
Comp. 225, 274; Valer. 209.

albicrus, K. (3), L., Umb. 173,
179; Ran. 6; Cruc. 29; Salix 378;
Fagop. 369 ; Cary. 66; Ros. 152, 134,
135, 189, 140, 133 ; Papil. 108* ; Ech.
310 ; Comp 274.

—— apicata, Sm., L., Sal. 378.

— argentata, Sm. = gracilis, Schenck
(2—24), L., Cary. 60 ; Salix 378 ; Ros.
139 ; Jas. 2838; Comp. 225, 274.

—— atriceps, K.=tibialis, K. (34), L.,
Cypr. 12; Salix 378 ; Ros. 152, 153 ;
Papil. 111; Erie. 285 ; Comp. 274.

icolor, F. =estiva, Sm., L., Fagop.

369.

— Cetii, Schr. (84), L., Scab, 212.

——. chrysosceles, K., L., Salix 378;
Ros. 1538, 139 ; Comp. 225.

cineraria, L., (4), L., Salix 378 ;
Cary. 65; Comp. 274.

—— cingulata, F., L., Sed: 162; Ran.
8; Comp. 274.

— coitana, K., Sld. Th., Umb. 194;
Hyper. 68; Geran. 178; Malv. 72;
Ros. 130; Scroph. 323+; Lab. 356;
Camp. 277, 278; Jas. 283; Comp. -
258, 268, 272.

— Collinsonana, K.=proxima, K., L., _
Umb. 179, 185, 184; Salix 378; Ros.
151; Comp. 274.

convexiuscula, K., L., Ros. 152;
Papil. 98, 95, 119 ; Scab. 212 ; Comp.
274.

—— denticulata, K.=Listerella, K., L.
Sld. T. Th.; Ros., 143; Papil. 94;
Lysim. 290* ; Comp. 225, 234, 238,
215, 268, 263, 264, 265, 273, 270.

—— dorsata, K. (3), L. T., Umb. 179,
192; Papav. 20; Cruc. 30, 36 ; Salix
378; Hyper. 68; Geran. 76, -78 ;
Polygon. 369, 371; Cary. 66; Ros.
152, 153, 149, 138, 139, 133, 127;
Papil. 104, 96; Scroph. 318; Eric.
287 ; Jas. 283; Comp. 248, 225, 263,
265, 274.

— eximia, Sm. (34), L., Salix 377.

—— fasciata, Wesm. (8—4), L., Ros.
127 ; Papil. 100* ; Myos. 306 ; Comp.
274.

eo ee

644

Andrena Flesse, Pz., L., Salix 378..
florea, Lep. =rubricata, Sm. (3), L.,
Bry. 171.

fucata, Sm.=clypearis, Nyl., Sld.
Th., Umb. 179, 194, 185; Ros. 148,
133.

—— fulva, Schr. (3), L., Lil. 394 ; Gross.
160, 161; Berb. 18; Ros. 153, 127,
129 ; Scroph. 318* ; Lab. 348* ; Eric.
285 ; Comp. 274.

fulvago, Chr., L. T. Th., Umb. 179;

Geran. 78; Jas. 283; Comp. 267, 263,

273, 270.

fulvescens, Sm., L. Sld., Umb. 181;
Ran. 10; Pap. 108* ; Comp. 267, 268,
263, 274, 272, 273, 269, 270.

—— fulvicrus, K. (3—34), L. Th., Cypr.
386 ; Umb. 177 ; Ran. 4, 7; Berb. 18 ;
Papav. 20; Cruc. 39 ; Cist. 171 ; Bry.
45; Salix. 378; Geran. 76; Malv. 69;
Fagop. 369; Ros. 163, 139, 133, 127 ;
Papil. 98, 100*, 94, 108, 110, 112;
Seroph. 324; Lab. 349; Eric. 287;

. Camp. 278; Jas. 283; Comp. 248,
225, 227, 234, 238, 236, 264, 274, 271,
273, 260.

fuscipes, K.=pubescens, K., L. T.,

Eric. 287; Jas. 283 ; Comp. 225.

Gwynana, K. (24), L. Sld. T. Th.,

Gross. 158, 161; Clem. 1; Ran. 9;

Cruc. 30, 39 ; Salix 378, 379; Geran.

78, 80; Malv. 69; Fagop. 66 ; Cary.

369 ; Ros. 151, 158, 135, 127; Scroph.

320, 324; Prim. 288; Eric. 285;

Scab. 211; Camp. 277, 278, 279, 281;

Comp. 248, 253, 237, 236, 274.

Hattorfiana, I’. (64—7), L. Sld. Th.,

Cary. 53; Scab. 211 ; Jas. 283.

helvola, L. (including varians, Rossi,

and mixta, Schenck), L., Umb. 179 ;

Berb. 18; Salix 378; Fagop. 369 ;

Ros. 153, 136*, 133 ; Jas. 283 ; Comp.

274.

labialis, K., L. Th., Papil. 90, 119*,

116 ; Ech. 310; Lab. 366.

lepida, Schenck., L., Umb. 174,

Comp. 225.

minutula, K., L., Umb. 177, 191;

Comp. 227.

nana, K., L., Gross. 158, 160;
Umb. 177, 194, 195; Cruc. 39, 40;
Salix 378; Fagop. 369; Ros. 139,
140 ; Comp. 248, 225, 227.

—— nigroenea, K. (34—4), L. Sld.,
Cypr. 12; Umb. 177 ; Crue. 39 ; Res.
43 ; Bry. 171; Salix 378 ; Ros. 134,
133 ; Papil. 116 ; Lab. 340; Eric. 284*,
285 ; Comp. 229, 227, 274.

nigriceps, K., L., Comp. 225.

nitida, K. (3), L., Gross. 161;
Coryd. 23+; Salix 878; Cary. 57* ;
Ros. 153; Lab. 366*, 359 ; Comp. 274.

——— parvula, K,, L. Sld. Th., Cypr. 384*;
Sed. 162; Umb. 179, 177, 181, 180, 192,

THE FERTILISATION OF FLOWERS.

°195, 185; Ran. 9, 10; Cruc. 30, 31,
38 ; Salix 378; Geran. 78; Maly. 69 ;
Cary. 65, 66; Ros. 151, 153, 139, 143,
133, 127, 128 ; Scroph. 319, 325, 328 ;
Eric. 287 ; Comp. 217, 236, 265, 274.
Andrena pilipes, F. (3), L. T., Umb. 179,
190; Crue. 38; Salix 378; Fagop.
369; Ros. 149; Scroph. 317; Eric,
285 ; Jas. 286 ; Comp. 257, 248, 225.
—— pratensis, Nyl. = ovina, Kl.
(4—5), L., Cypr. 12 ; Salix 378, 379;
Comp. 274.
punctulata, Schenck, L., Salix

rose, Pz.,.L. T. Th., Umb. 172,
180, 194 ; Salix 378 ; Ros. 127.

— Schrankella, Nyl. (4), L. Th., Crue.
27; Salix 378; Ros. 153, 136, 127;
Papil. 100* ; Comp. 255, 227.

simillima, Sm., T., Eric. 287.

Smithella, K. (2), L., Gross. 160 ;

Berb. 18 ; Salix 378, 379 ; Ros. 152 ;

Comp. 274.

thoracica, K., L., Ros. 125.

——' Trimmerana, K., L., Berb. 18;

Salix 378 ; Ros. 153, 133.

varians, Rossi, L., Salix 378.

ventralis, Imh. (2—23), L., Salix

378, 379.

vitrea, Sm. = nitens, Schenck,

Cassel, Comp. 248.

xanthura, K. (3), L. Sld., Papil.
90, 100, 101, 95, 111, 108; Comp.
274, 270.

— spec., L., Ase. 87.

378

Anthidium (8 species, 16 visits).

Anthidium manicatum, L. (9—10), L.
Sld. Th., Pap. 90, 100, 92* ; Scroph.
320; Lab. 364, 352, 346, 347, 337 ;
Comp. 258.

punctatum, Latr. (54), Sld. Th.,
Pap. 90, 92*, 108*.

—— strigatum, Latr. (5), L. Sld. Th.,
Papil. 90 ; Jas. 283 ; Comp. 257.

Anthophora (5 species, 82 visits).

Anthophora estivalis, Pz. = Haworthana,
K. (15), Th., Papil. 102 ; Lab. 347.
—— fureata, Pz. (11—12), L. Sld. Th.,

Ech, 310; Lab. 364, 352, 355.

—— pilipes, F. (19—21), L. T., Lil. 394;
Did. 22; Coryd. 23, 24; Viol. 47;
Ros. 150; Papil. 100, 118; Bor. 300,
804; Lab. 366, 359, 362, 368, 349;
Vine. 293; Ol. 291; Prim. 287.

— quadrimaculata, F. (9—10), T. Sld.
Th., Malv. 70; Papil. 92; Ech. 310;
Scroph. 365 ; Lab. 364, 352, 336.

— retusa, L. (16—17), L. Pedic. 333.

Apis mellifica, L. 8 (6), L., T. Sld. Th.,
(189 yisits), Lil. 891, 888; Smil.

$89; Ir. 887* ; Gal. 396 ; Orch. 382,
388, 384; Berg. 156 ; Gross, 159, 160 ;

INDEX OF INSECTS.

Umb. 172, 179, 194, 185, 186 ; Clem.
1; Thal. 2,3; Anem. 4; Ran. 5, 7,
9, 11, 12; Ag. 13¢; Berb. 18; Dicl.
22+; Coryd. 238t, 24t; Fum. 26;
Cruc. 27, 29, 30, 31, 34, 35, 39, 40,
41; Res. 42, 48; Viol. 47; Cist. 51;
Bry. 170+ ; Salix 378, 379; Rhamn.
86; Mese. 87 ; Polygal. 45 ; Rhus. 88,
89; Rut. 84; Geran. 77, 80, 83 ; Lin.
75; Til. 73; Malv. 69, 70, 71, 72;
Polygon. 369, 370; Cary. 65, 62, 57 ;
Lythr. 165; Onagr. 166, 169; Ros.
150, 151, 152, 153, 148, 134, 135, 138,
139, 142, 136+, 180, 183, 127, 129;
Papil. 90, 98, 100t, 101, 103, 105, 96,
97, 93t, 94, 95, 92, 111, 108, 109, 110,
Be, 107, 123, 122, 117, LIST, 119,
114, 116; Convolv. 311; Ech. 310;
Bor. 301, 300+, 302, 306 ; Solan. 314,
315 ; Scroph. 318, 319, 320, 324, 325,
327, 332, 330, 335t; Lat. 366, 364,
3591, 362, 363, 360t, 355, 349, 347,
348, 344, 340, 342; Ascl. 295; Ol.
291 ; Plant. 367; Prim. 288*; Eric.
286, 287, 284, 285; Rubiac. 207 ;
Caprif. 201, 202, 203, 204 ; Scab. 211,
212, 213; Camp. 277, 278, 279; Jas.
283 ; Comp. 257, 258, 259, 248, 249,
250, 253, 244, 227, 234, 237, 238, 215,
217, 236, 214, 266, 263, 274, 276, 271,
270, 260; Valer. 208, 209.

Bombus (17 species, 509 visits).

Bombus agrorum, F. (= muscorum, L.),
(10—15), L. T., Sld. Th., Smil. 390 ;
Ir. 387; List. 380+; Orch. 382 ; Sed.
164; Aq. 18; Papav..21; Coryd. 25 ;
Viol. 48 ; Hyperic. 68; Rhamn. 86 ;
Til. 73; Malv. 69, 70; Cary. 57;
Lythr. 165; Onagr, 166, 169; Ros.
150, 148, 1385; Papil. 90, 100, 104,
120, 117, 118, 116; Ech. 310, 300,
802, 304 ; Solan. 315 ; Scroph. 317, 321,
$22, 323, 330, 335, 333 ; Lab. 365, 360,
856, 857, 358, 352, 353, 349 ; Gent.
296 ; Vince. 293, 294; Eric. 286, 284,
285 ; Symphor. 201; Dips. 210, 211,
212; Comp. 241, 257, 258, 249, 245,
243, 244, 256 (68 visits).

—— Barbutellus, K. (Apathus?) (12),
L. Sld. Papil. 100 ; Ech. 310 ; Scroph.
326, 334; Lab. 349; Scab. 211;
Comp. 274, 272 (9 visits).

campestris, Pz. (Apathus) (10—12),

L. T., Orch. 382; Sed. 154; Onagr.

166; Ros. 135, 100, 116; Ech. 310;

Eric. 285; Scab. 211; Comp. 256,

250, 244, 238, 215 (14 visits).

confusus, Schenck (12—14), L. Th.,

Orch. 382, 383, 384; Onagr. 165 ;
Ros. 136 ; Papil. 100, 119, 116; Lab.
I Dr. Kriechbaumer tells me that the name

Psithyrus is older than Apathus, and P. saltwum,
Pz., older than Barbutellus, K.

645

366, 349; Prim. 288; Eric. 285;
Comp. 241, 258, 274, 273 (16 visits).
Bombus fragrans, Kirby! (15), L., Orch.
384 ; Salix 378 ; Ros. 136 ; Pap. 100 (4

visits).

hortorum, L.? (18—21), L. Sld. Th.,
Colch. 395 ; Smil. 390; Ir. 387 ; Orch.
882, 383, 384; Berg. 156; Aq. 138;
Delph. 14, 15; Aconit. 17; Dicl. 22;
Viol. 47 ; Salix 378; Malv. 69 ; Pom.
150; Ros. 134, 135, 136, 129; Pap.
91, 125, 117, 119 ; Ech. 310; Bor. 304 ;
Scroph. 319, 320, 321, 323, 334, 335,
333 ; Lab. 366, 359, 361, 362, 360, 352,
349; Vinc. 293; Ol. 291; Prim. 288 ;
Eric. 285 ; Scab. 211 ; Jas. 283 ; Comp.
248, 247 (49 visits).

——hypnorum, L. (10—12), L. Sld.
T. Th., Ros. 136 ; Ech. 310 ; Scroph.
334, 365, 364s; Ascl. 295; Scab. 211
(7 visits).

— lapidarius, L. (8—14), L. Sld. T.
Th., Orch. 382, 383, 384; Sed. 164;
Viol. 46, 47, 49; Salix 378 ; Aisc. 87 ;
Polygal. 51; Malv. 69; Fagop. 369 ;
Cary. 57 ; Onagr. 166, 169; Ros. 150,
136, 129; Papil. 100, 101, 92, 111,
112, 107, 118, 119; Ech. 310; Bor.
300}, 302, 304; Scroph. 321, 332,
333 ; Lab. 366, 364, 359, 358, 355, 349 ;
Vine. 293 ; Ol. 291; Prim. 288 ; Eric.
284 ; Dips. 210, 211, 212, 213 ; Camp.
277, 279; Comp. 240, 241, 242, 257,
258, 255, 248, 250, 251, 257, 245, 246,
238, 266, 274, 271, 270 (65 visits).

—— muscorum, F. (= senilis, F. Smith)
(10—14), L. T. Th., Orch. 382 (2), 383,
384 ; Cist. 45; Papil. 100, 102, 94, 91,
116; Ech. 310; Bor. 302; Seroph.
318, 331 ; Lab. 366, 364; Rubiac. 207 ;
Caprifol. 201, 204; Comp. 240, 241,
258, 246, 274 (23 visits).

—— pratorum, L. (8—12), L. Sld., All.
392 ; Orch. 382, 383, 384 ; Gross. 162 ;
Berb. 18; Chelid. 21; Diclytr. 22t;
Salix 378 ; Onagr. 166 ; Ros. 134, 135,
136; Papil. 98, 100t, 123, 116; Ech.
310; Bor. 301, 300t, 302, 304, 315;
Scroph. 330, 334t, 335f, 364; Lab.
366, 359, 362, 363, 360, 352, 355, 349,
341; Plant. 367; Eric. 285; Caprif.
201, 204 ; Scab. 211, 212 ; Camp. 277 ;
Comp. 257, 253, 246, 247, 237, 238,
272, 208 (52 visits).

—— Rajellus, Ill. (10—13), L., Ir. 387 ;
Sed. 162; Papav. 21; Dicl. 22;
Viol. 47 ; Cary. 57; Papil. 100, 101,
117, 118; Ech. 310; Bor. 300, 304;

t According to Dr. Kriechbaumer, B. fragrans,
K., is quite distinct from B. fragrans, Pall., a
Siberian species. The latter must be called
B. distinguendus, Moraw, and is, perhaps,
identical with B. elegans, Seidl.

2 Including B. ruderatus, F.

646

Scroph. 334 ; Lab. 364, 359, 3611, 363,
360, 349 ; Eric. 286 ; Scab. 211 ; Comp.
253, 268 (23 visits).

Bombus rupestris, F. (Apathus) (11—14),
L. T. Th., Papil. 100, 116 ; Ech. 310;
Lab. 364, 349; Dips. 310, 211, 212;
Jas. 283; Comp. 241, 257, 258, 255,
215 (14 visits).

Scrimshiranus, K. (10), L. T. Th.,
Gross. 161; Salix 378; Ros. 135, 136,
133; Papil. 117, 116; Scroph. 319,
334, 333f, 358, 355; Eric. 284 (13
visits).

—— senilis, F. Smith (= B. muscorum,
F.1) (11—15), L., Orch. 383 ; Ros. 136,
133 ; Papil. 100, 119, 116; Bor. 304;
Seroph. 334, 359; Gent. 296; Eric.
286 ; Scab. 212 (12 visits).

silvarum, L. (9—14), Fig. 15, L. T.

Th., Orch. 383 ; Sed. 164; Malv. 69;

Lythr. 165; Onagr. 169; Ros. 134,

135, 136, 100; Papil. 91, 118, 119,

116; Ech. 310; Bor. 300, 302, 304;

Scroph. 321, 332, 334, 333 ; Lab. 366,

364, 359, 360, 356, 358, 358, 355,

349, 346, 347 ; Gent. 297 ; Prim. 288 ;

Eric. 286, 285; Scab. 211, 212; Jas.

283; Comp. 240, 241, 257, 258, 259,

246, 244, 268, 274 (48 visits).

terrestris, including lucorum, L.

(7—9), L. Sld. T. Th., Lil. 394, 393 ;

Orch. 382, 384; Gross. 161; Umb.

194 ; Clem. 1; Ran. 5, 8,11; Aq. 13t ;

Berb. 18; Dicl. 22+; Coryd. 23f,

24¢; Cruc. 30 ; Sal. 378, 379 ; Hyper.

68 ; Aisc. 87 ; Polygal. 51; Cary, 57;

Lythr. 165; Onagr. 166; Ros. 150,

151, 135, 136+, 133, 128; Papil. 90,

100t, 92, 111, 108, 112, 118t, 119f,

115; Echy 310; Bor. 300t, 304;

Scroph. 317, 320, 321, 323, 334t,

835, 333; Lab. 359+, 361f, 360},

356, 353, 355, 349t, 342; Ascl. 295;

Vine, 293 ; OL. 291; Plant. 368 ; Prim.

2881 ; Eric. 286, 287, 284, 285; Scab.

211, 212; Comp. 241, 242, 258, 255,

250, 229, 239, 215, 268, 274 (79 visits).

vestalis, Fourer. (Apathus) (12), L.
Sld. T. Th., Ir. 387 ; Ros. 135 ; Papil.
100, 117; Ech. 310; Scroph. 326 ;
Lab. 349; Vine. 293 ; Eric. 285 ; Scab.
211, 212; Comp. 253, 247, 214, 274
(15 visits).

Ceratina ccerulea, Vill. (4—5), L., Ech.
310 ; Jas. 283 ; Comp. 267.

Chalicodoma muraria, F. (10), Th., Papil.
116.

Chelostoma (3 species, 25 visits).

Chelostomacampanularum, K. (8—3$), L.
Sld. T. Th., Malv. 69; Lab. 347t ;
* I only lately became aware of the identity of

these species ; I have placed the darker varieties

under B. muscorum, F., the light-yellow ones
uuder B, senilis, Smith.

THE FERTILISATION OF FLOWERS.

Camp. 277, 278, 279, 280; Jas. 283 ;
Comp. 246, 263.

Chelostoma florisomne, L. =maxillosum,
L. (84—4), L. Th., Ran. 7, 8 ; Camp.
280 ; Comp. 274.

—— nigricorne, Nyl. (4—44). L. T. Sld.
Th., Geran. 77, 78; Malv. 69, 72;
Ech. 310 ; Lab. 336 ; Camp. 277, 278,
279, 280, 281; Comp. 225.

Cilissa (3 species, 16 visits).

Cilissa hemarrhoidalis, F. (83—4), L.
Sld., Malv. 69, 71; Lab. 355; Comp.
277, 278, 279.

leporina, Pz. =tricincta, K. (33), L.

Th., Sed. 162; Papil. 100, 101, 94,

92; Jas. 283 ; Comp. 248, 246.

melanura, Nyl. (3—4), L. Sld. T.,

Lythr. 165 ; Comp. 273.

Celioxys (6 species, 28 visits).

Celioxys acuminata, Nyl., Th., Comp.
242.

— spec., L., Ros. 140 ; Papil. 90 ; Lab.
349, 341; Ascl. 295; Comp. 211.

conoidea, Ill. = punctata, Lep. (6),

L. Th., Papil. 116; Ech. 310; Lab.

336; Scab. 211; Jas. 283; Comp.

255, 266.

quadridentata, L. = conica, L. =
acuta, Nyl., L., Papil. 96; Ech. 310 ;
Scab. 211; Jas. 283 ; Comp. 242.

—— simplex, Nyl. (44), L., Bry. 171;
Malv. 69 ; Ech. 310 ; Jas. 283 ; Comp.
218, 266.

umbrina, Sm. = parvula, Schenck,

L. Th., Ros. 1385; Ech. 310; Lab.

336. .

Colletes (4 species, 16 visits).

Colletes cunicularia, L. (34—4), L., Salix
377 ; Eric. 285.

—— Davieseana, K. (24), L. Sld., Onagr.
169 ; Papil. 108 ; Comp. 225, 229, 227,
234, 274, 270.

—— fodiens, K. (2§), L., Papil. 100 ;
Comp. 225, 234.

—— marginata, L. (2), L., Papil. 101 ;
Jas, 283 ; Comp. 227.

Crocisa scutellaris, Pz. (7—74), T. Th.,
Lab. 336.

Dasypoda hirtipes, F. (44—5), Fig. 10,
1., L. Th., Jas. 283 ; Comp, 248, 246,
266, 263 (7 visits).

Diphysis serratule, Pz. (7—8), L. Sld. T.,
Ros. 135 ; Papil. 90, 100, 101, 108*, 120,
265, 271, 117; Ech. 310; Eric. 287 ;
Scab, 211 ; Jas. 283 ; Comp. 257, 267,
271, 270 (15 visits).

Epeolus variegatus, L, (134), L., Jas.
283 ; Comp. 248.

Eucera longicornis, L. (10—12), L. Sld.,
Orch. 383, 384; Ros. 153; Papil. 90,

INDEX OF INSECTS.

100, 123, 126, 117, 116; Ech. 310;
Bor. 300 ; Lab. 359 ; Ol. 291; Plant.
368 ; Caprif. 201 (15 visits).

Halictoides dentiventris, Nyl. (2—24),
L. Sld., Camp. 277, 278.

Hatlictus (32 species, 440 visits, 181 being

to Composite).

Halictus albipes, F. = obovatus, K. (in-
cluding affinis, Schenck), L. Sld. Th.,
Umb. 179, 177, 195; Ran. 9; Salix,
878 ; Geran. 76; Malv. 69 ; Polygon.
371; Ros. 135, 133, 127; Papil. 103,
108, 116 ; Ech. 310 ; Scroph, 326, 328 ;
Lab. 342; Ol. 291*; Plant. 368; Scab.
211; Camp. 279; Jas, 283; Comp.
257, 248, 246, 229, 238, 223, 220, 221,
263, 274, 262, 271, 272, 260 (37 visits).

TS brevicornis, Schenck, Th., Comp.
270.

—— cylindricus, F.=fulvocinctus, K.= °

malachurus, K. (8—4), L. Sld. T. Th.,

Lil. 393; Umb. 172, 179, 194; Ran..

4, 6, 7,9, 10; Papav. 20, 21; Cruc.
30, 39; Salix 378 ; Geran. 76, 77, 78;
Lin. 75; Malv. 71; Cary. 65; Lythr.
165 ; Ros. 153, 135, 189, 127; Papil.
108, 110; Ech. 310; Solan. 316;
Scroph. 319, 323+, Lab. 362*, 363*,
842, 388; Ascl. 295; Plant. 368;
Eric. 285 ; Scab. 211, 212; Camp. 278;
Jas. 283; Comp. 241, 242, 257, 248,
253, 245, 246, 247, 225, 229, 238, 223,
220, 221, 217, 268, 263, 265, 274, 262,
271, 272, 278, 269, 270 (65 visits).

—— fasciatus, Nyl., L., Jas. 283.

—— flavipes, F.,1= seladonius, F. (24),
L. Th., Umb. 194; Ran. 6, 7 ; Papav.
20; Geran. 76; Ros, 139, 141, 133;
Pap. 90, 100, 105, 95, 116 ; Scroph.
322; Eric. 285; Camp. 280; Jas.
283 ; Comp. 248, 220, 221, 263, 274,
276, 273, 270 (26 visits).

— fulvicornis, K., L., Umb. 195.

—— interruptus, Pz., Th., Umb. 175,
195 ; Comp. 257, 246 (4 visits).

— leucopus, K., L. Sld. T. Th., Umb.
194; Cruc. 34; Ros. 139; Scroph.
328 ; Lab. 362* ; Comp. 220, 274, 271
(9 visits).

leucozonius, Schr. (4), L. Sld. T.

Th., Orch. 384; Umb. 191; Ran. 7;

Aq. 13; Cruc. 40; Geran. 77 ; Ros.

135, 140; Scab. 211, 212; Jas. 283 ;

Comp. 257, 246, 225, 229, 220, 266,

267, 2638, 262, 271, 272, 278, 270 (24

visits).

— longulus, Sm. = pauxillus, Schenck,
L. Th., Umb. 172, 189; Ran. 7;
Papay. 20; Geran. 76, 77 ; Convolv.
311; Scroph. 324; Lab. 338 ; Comp.
257, 248,.246, 243, 244, 223, 220, 263,
274, 262, 271, 260 (21 visits).

* According to F. Smith = H. tumulorum, L.

647

Halictus lucidulus, Schenck, L., Cruc. 38;
Geran. 77 ; Ros. 135, 1388 ; Lab. 349* ;
Jas. 283; Comp. 257, 246, 227, 274
(10 visits).

—— lucidus, Schenck, L., Ran. 9 ; Ros,
134.
—— lugubris, K. = levigatus, K., L.
Th., Papil. 116 ; Lab. 359 ; Comp. 263,

276, 273, 270 (6 visits.)

maculatus, Sm., L. T. Th., Umb.
177, 182; Ran. 7; Papav. 20; Geran.
77, 78, 79 ; Malv. 69 ; Ros, 140 ; Papil.-
98 ; Lab. 338 ; Camp. 279 ; Comp. 257,
258, 248, 246, 225, 229, 228, 234, 238,
223, 220, 263, 274, 262, 271, 273 (28
Visits),

— minutissimus, K., L., Iythr. 165 ;
Comp. 217, 274.

— minutus, K. (2), L. T., Umb. 178 ;
Comp. 257, 248, 246, 265, 262 (6
Visits).

— morio, F. (2), L. Th., Malv. 69, 70 ;
Cary. 56; Convolv. 311+, Scroph.
321; Lab. 346+ ; Comp. 225, 220, 278
(9 visits).

— nitidiusculus, K., L. Th., Gross,
158; Ran. 7, 9.; Cruc. 27, 38 ; Geran.
76; Ros. 184; Convolv. 311; Ech.
310; Scroph. 328; Lab. 3461, 338 ;
Comp. 257, 248, 246, 227, 221, 274,
262, 269, 260 (21 visits).

— nitidus, Schenck, L. Th., Gross.
158 ; Ros. 148 ; Ech. 310 ; Lab. 346t,
347, 342; Comp. 238, 223, 236, 267,
263, 274 (12 visits).

—— quadricinctus, F.,1 L. Th., Umb.
191; Ran. 7; Papil. 101, 94; Ascl.
295 ; Comp. 240, 241, 242, 257, 258,
225, 246, 220, 263, 264, 276, 262, 260
(18 visits).

—— quadrinotatus, K., Th., Comp. 246.

quadristrigatus, Latr.,' (5—7), Th.,

Comp. 255.

rubicundus, Chr. (3—44), L. Th.-
Gross. 161; Ran. 7; Berb. 18; dsc.
87; Ros. 151,-152; Papil. 90, 108 ;
Eric. 285 ; Scab. 212 ; Comp. 240, 257,
248, 246, 225, 229, 263, 264, 274, 276,
262, 270, 260 (23 visits).

— Scabiose, I]l., Freiburg, Hild., Asel.
295.

sexnotatus, K. (24—4), L. T., ‘Lil.

388; Umb. 177; Clem. 1; Thal. 2;

Ran. 7 ; Papav. 20, 21 ; Cruc. 29 ; Bry.

171+ ; Rhus 88; Rut. 84; Geran. 79 ;

Cary. 63; Ros. 150, 149, 134, 135;

1 Dr. Kriechbaumer tells me that the species
described by Kirby and later authors as H.
quadricinctus, F., is not the true H. quadri-
cinctus of Fabricius, but a distinct species, H.
tetrazonius, Kl. But H. quadristrigatus, Latr.;
is identical with H. quadricinctus, F., and must
receive that name, as the older one. (Gers-
taecker, Archiv fiir Naturgeschichte, Jahrg.
xxxiv. Bd. 1.)

648

131; Papil. 126; Bor. 301, 300f,
Scroph. 318, 322; Lab. 3621, Eric.

_ 285; Caprif. 201, 202, 200; Scab.
211; Comp. 274, 262 (31 visits).

Halictus sexsignatus, Schenck, L., Ran.
7; Comp. 222, 274.

sexstrigatus, Schenck, :L., Papav.
21; Bry. 171+; Rhus 88; Ros. 149,
138, 189, 140, 141, 183 ; Scroph. 325 ;

_Lab. 346+; Eric. 285; Comp. 270
_ (18 visits).

— Smeathmanellus, K., L. T. Sld.
Th., Umb. 185; Aq. 13; Res. 42;
Geran. 78; Malv. 69; Scroph. 319,
3217; Camp. 277 ; Comp. 257, 246,
262, 271, 272, 273 (14 visits).

tarsatus, Schenck, L., Pap. 98;

Comp. 248 (2 visits).

villosulus, K. = punctulatus, K.,-

L. T. Th., Ran. 7 ; Cist. 45 ; Ros. 135,

Convolv. 311; Jas. 283; Comp. 225, —

229, 266, 267, 264, 265, 274, 271, 272,
273, 270 (16 visits).
zonulus, Sm. (4), L. Tekl. Th., Sed.
164; Ran. 7; Resed. 42 ; Geran. 76;
Malv. 69; Ros. 152, 149, 135, 142,
131; Papil. 101, 112 ; Bor. 301, 308 ;
Scroph. 321+, 322; Lab. 366* ; Prim.
290* ; Comp. 257, 238, 274, 262 (22
visits).
spec., L., Cruc. 31; Geran, 80;
Cary. 60, 53; Ros. 145; Ascl. 2957 ;
Plant. 367, 368 ; Valer. 208 (10 visits).
Heriades truncorum, L. (4—44), L. T.
Th., Umb. 187; Papil. 96; Ol. 292;
Scab. 211; Comp. 248, 246, 225, 228,
238, 223, 263, 264 (13 visits).
Macropis labiata, Pz. (25—3), L., Umb.
187 ; Rhamn, 86 ; Ros. 135 ; Prim. 290.

Megachile (9 species, 77 visits).

Megachile argentata, F., (6) L., Jas. 283 ;

Comp. 266.
centuncularis, L. (6-—7), L. Sld.
Th., Lil. 388; Sed. 162; Umb. 194;
Dicl. 22+; Lythr. 165; Ros. 149;
Papil. 108* ; Bor. 301 ; Scroph. 321+ ;
Lab. 336 ; Caprif. 201, 203 ; Scab. 211 ;
Comp. 257, 258, 246, 244, 224, 276
(20 visits).
cireumcineta, K. (8), L. Sld. Th.,
Sed. 162; Ros. 148, 149; Papil. 90,
100, 92, 108, 107, 117, 116; Ech. 310;
Scroph. 335; Lab. 340; Plant. 368 ;
Scab. 211; Comp. 242 (16 visits).
lagopoda, L. (10), Th., Umb. 191 ;
Comp. 242, 257, 255, 251, 246 (6
visits).
ligniseca, K., L. Th., Malv. 69;
Comp. 258.
maritima, K., L. (8—9), Sed. 163 ;
Papil. 101, 92, 120, 117 ; Scroph. 320 ;
Scab. 211; Jas. 283; Comp. 259, 250
(9 visits).

THE FERTILISATION OF FLOWERS.

Megachile pyrina, Lep. = M. fasciata, Sm.*
(9), L. Sld. Th., Papil. 90, 93, 92%,
124 ; Lab. 364, 346, 336 (7 visits).

— versicolor, Sm., L. Sld. Th., Pap.
92, 108, 120, 117; Comp. 246 (5
visits).

—— Willughbiella, K. (64—7), L. Sld.
Th., Malv. 69; Papil. 90, 98, 108*,
117 ; Ech. 310; Lab. 354, 336; Scab.
211; Comp. 266 (10 visits).

Melecta armata, Pz. = punctata, K. (11),
L. T., Lab. 358, 361.

—— luctuosa, Scop. (10), L. Th., Ech.
310.

Nomada (21 species, 85 visits).
Nomada alternata, K.=N. Marshamella,
K., L., Comp. 274.
armata, Schaeff. = N. cincticornis,
Nyl., L., Seab. 211.
Fabriciana, L., L., Coryd. 23+ ; Ros.
135 ; Scab. 211; Jas. 283 ; Comp. 267.
—— ferruginata, K., L. Sld. Th., Sed.
162 ; Umb. 194; Papil. 94 ; Eric. 285 ;
Comp. 238.
flavoguttata, K., L., Cary. 65;
Comp. 217, 274.

furva, Pz. = minuta, F.;, L.,
Comp. 238.

germanica, Pz., L. T., Lab. 340;
Comp. 266.

Jacobee, Pz. (4), L., Onagr. 166 ;
Lab. 358 ; Scab. 311 ; Jas. 283 ; Comp.
248.
lateralis, Pz., L., Th., Umb, 195 ;
Cruc. 30; Hyper. 68 ;-Malv. 69 ; Ros.
135 ; Scroph. 330. eae
Lathburiana, K. = rufiventris, K.,
L., Salix 378 ; Comp. 274.
lineola, Pz. (6), L:, Cruc. 30 ; Salix
378 ; Hyper. 68 ; Ros. 135 ; Scab. 317 ;
Jas. 326; Comp. 248, 217, 274.
nigrita, Schenck, L., Jas. 283;
Comp. 248.
Roberjeotiana, Pz., L. Th., Umb.
172; Onagr. 166; Jas. 283; Comp.
349.
ruficornis, L. = flava, Pz (8—44),
L. Sld., Salix 378; Cary. 65; Ros.
152, 161, 185, 188, 189; Pap. 90;
Eric. 285; Jas. 283 ; Comp. 225, 274.
sexfasciata, Pz. (7), L., Orch. 384;
Ros. 138; Ech. 310.
solidaginis, Pz., L. T., Papil. 94 ;
Eric. 286* ; Comp. 248, 220.
signata, Jur., L., Salix 378 ; Ros.
152, 153, 1389 ; Comp. 274.
— succinct, Pz. (64—7), L., Salix
378 ; Ros. 140, 127 ; Comp. 257, 274.

t According to Dr. Kriechbanmer identical
with M. pyrina, Smith, but not with M. pyrina,
Lep., identical, however, with M_ ericetorwm,
Lep., which name is the oldest, and has priority
over M. fasciata, Sm.

_ eo eee Se

INDEX OF

Nomada varia, Pz. =fucata, Pz. (54—6),
L. Th., Salix 378 ; Papil. 94 ; Lab. 349 ;
Jas. 283 ; Comp. 238, 274, 276.

— xanthosticta, K., L., Ros. 140.

eo zonata, Pz., L. T. Th., Comp. 225,
276.

Osmia (13 species, 100 visits).

Osmia adunea, Latr. (10), L. T. Sld. Th.,
Pap. 117 ; Ech. 310.

— enea, L. (9—10), L. Sld. Th.,
Malv. 69; Papil. 90, 100, 92; Ech.
310 ; Scroph. 320 ; Lab. 366, 364, 359,
349, 336 ; Scab. 211 ; Comp. 258, 246.

— aurulenta, Pz. (8—9), Sld. Th.,
Pap. 90, 94, 91, 92, 116; Lab. 364 ;
Comp. 246.

— cementaria, Gerst. Spinole,
Schenck, Th., Papil. 101; Ech. 310.
cornuta, Latr. (8—9), L., Ros. 129.
— fulviventris, Pz., L. Th., Lab. 364;

Scab. 211; Comp. 255, 245, 246.

— fusca, Chr. = bicolor, Schr. (8),
L. Sld. T. Th., Orch. 384 ; Ran. 4, 8;
Viol. 49 ; Geran. 78; Ros. 135, 139 ;
Papil. 112; Ech. 310; Pulm. 304;
Lab. 366, 349 ; Comp. 274.

—— interrupta, Schenck, L. Th., Papil.
90

— leucomelena, K. (¢ 24, ? 34—4),
L., Ech. 310 ; Scroph. 320 ; Comp. 225.

—— pilicornis, Sm., L., Pulm. 304.

— rufa, L. = bicornis, L. (7—9), L.
T., Lil. 394, 388 ; Ir. 387 ; Orch. 383 ;
Clem. 17; Ran. 7, 11; Dicl. 22+ ; Crue.
80; Viol. 47, 49; Salix 878; Aisc.
87; Geran. 77; Cary. 66, 57; Ros.
150, 153, 133, 127, 129 ; Papil. 118t,
119; Ech. 310; Bor. 304; Lab. 366,
349, 346, 347, 336; Vinc. 291, 293;
Prim. 288*; Eric. 285; Comp. 217,
274 (37 visits).

spinulosa, K. (5), Abundant in
Thuringia, nesting in empty shells of
Helix ericetorwm. Papil. 116 ; Comp.
257, 258, 255, 246, 225, 238, 263, 264,
276, 262, 260 (12 visits).

— spec., L., Pap. 96.

— villosa, Schenck (according to Dr.
Kriechbaumer, identical with O. platy-
cera, Gerst.), Sld., Papil. 108.

Panurgus (2 species, 16 visits).

Panurgus Banksianus, Latr.=P. ater,
Latr. (3), L. T. Th., Comp. 263, 265,
276, 270.

calcaratus, Scop. =P. lobatus F. (8),

L. T. Th,, Ran. 7 ; Onagr. 169 ; Comp.

266, 267, 268, 263, 265, 276, 262, 271,

273, 270 (12 visits).

INSECTS. 649

Prosopis (15 species, 88 visits).

Prosopis annularis, Sm., Th., Lil. 388 ;
Res. 42.

——armillata, Nyl. (14), L. T. Sld., Sed.
162 ; Umb. 173, 192, 194, 186; Crue.
38 ; Res. 42, 43 ; Hyper. 68 ; Polygon.
371; Ros. 140 ; Comp. 271 (13 visits).

ma yl., L.,Sed. 162; Umb.

—— clypearis, Schenck., Th., Umb. 179.

—— communis, Nyl. (1—14), L. T. Th.,
Umb. 177, 179, 192, 186 ; Cruc. 38;
Res. 42, 43 ; Rhus 89 ; Geran. 76, 77 ;
Maly. 69; Cary. 63; Ros. 148, 149, 135,
138, 130; Scroph. 317, 327; Lab. 346+;
347 ; Jas. 283; Comp. 248, 229 (24
visits).

—— dilatata, K., L., Malv. 69; Jas.

' 283.

— excisa, Schenck., L., Ros. 135.

—— hyalinata, Sm. = P. confusa, Nyl.,
L. 'Th,, Ran. 7; Geran. 77 ; Malv. 69 ;
Cary. 63 ; Ros. 140 ; Ech. 310 ; Camp.
“He 278, 279, 282 ; Jas. 283; Comp.

—— pictipes, Nyl., L., Res. 42; Malv.
69 ; Jas. 283 ; Comp. 225.

—— propinqua, Nyl., L., Kos. 149.

—— punctulatissima,Sm. = P. obscurata,
Schenck, Th., Lil. 4; Comp. 246.

— signata, Pz. (14), L. Th., Umb.173;
Clem 1; Thal. 22; Res. 42 ; Malv. 69;
Ros. 343 ; Seroph. 317 ; Comp. 233 (8
visits).

— sinuata, Schenck, L. Th., Umb. 192,
195 ; Rut. 84; Comp. 248.

variegata, F., L. Th., Sed. 162;

Umb. 188, 191, 198, 195; Ros. 135;

Jas. 283 ; Comp. 248, 225.

spec., L., Umb. 187, 190 ; Til. 73.

Psithyrus. The species of this genus
are referred to Bombus.

Rhophitoides canus, Eversm. (24—3),
Th., Papil. 90, 94.

Rhopbites halictula, Nyl., L., Jasione
283.

vulgaris (Dufourea), Schenck (2),
T. Th., Comp. 263, 264, 265, 262,
273, 279, 270.

Saropoda bimeculata, Pz.=S. rotundata,
Pz. (9), L. Th., Hyper. 68; Lythr.
165 ; Ech. 310; Scroph. 365 ; Lab. 340;
Eric. 287 ; Jas. 283; Comp. 257, 255
(9 visits).

Sphecodes gibbus, L. (including rufescens,
ephippia, etc.) (14), L. T. Sld. Th., Sed.
162; Gross. 158 ; Umb. 176, 181, 188,
192, 194, 195, 183; Coryd. 22; Crue.
83 ; Salix 378; Geran. 78; Fagopyr. 369;
Onagr. 166 ; Ros. 140; Jas. 283; Comp.
248, 225, 229, 233, 284, 222, 217, 274,
269, 270 (28 visits).

Stelis aterrima, Pz. (5—54), Th., Ger. 77;

650

Ascl. 295; Comp. 255, 245, 246 (5
visits).

Stelis breviuscula, Nyl. = S. pygmea,
Schenck, L. Th., Ros. 135; Ech. 310 ;
Scab. 211 ; Comp. 246, 225 (5 visits).

— phezoptera, K. (5), L. Th., Ech.
310; Comp. 246.

B. Chryside (8 species, 23 visits).
Chrysis bidentata, L., Th., Umb. 192.
—— cyanea, L., L., Ros. 149.

— ignita, L., L. Th., Umb. 192, 183;
Rut. 84 ; Ros. 149, 130*.

spec., L., Umb. 172.

Cleptes semiaurata, F., L., Ech. 310.

Elampus auratus, Wesm., L., Ros. 130*.

Hedychrum coriaceum, Dlb., L., 368.

— lucidulum, Latr., L., Th., Umb.
179, 191, 192, 195; Cruc. 38, Ros. 130*,
133 ; Jas. 283 ; Comp. 248, 225, 230,
266.

C. Cynipide (1 species, 1 visit).
Eucoila spec., L., Chrysospl. 155.
D. Formicide (4 species, 18 visits).

Formica congerens, Nyl., L., Ros. 152;
Comp. 274.

Lasius niger, L., L., Chrysospl. 155 ;

Ros. 151, 152. .
Myrmica levinodis, Nyl., L , Chrysespl.
155 ; Comp. 217.
M. ruginodis, Nyl., Chrysospl. 155.
Undetermined: Umb. 192, 185, 186; Ran.
10; Cary. 55; Ros. 150, 151, 152,
Scroph. 320 ; Ascl. 295t.

E. Ichnewmonide and their allies
(13 species, 48 visits).

Alysia, L., List. 380.

Campoplex, L., List. 380.

Cryptus, L., List. 380.

Eulophus, L., Adoxa 198.

Feenus jaculator, F. (1), L. Th., Umb.
179, 192, 183 ; Rut. 84; Cary. 55.

—— affectator, F. (1), L. Th., Umb.
179, 190, 191, 184; Rut. 84.

Ichneumon uniguttatus, L., L., List.
380.

Microgaster rufipes, F., L., List. 380.

Perilampus (?), L., Salix 378.

Pezomachus, L., Adoxa 198.

Phegadeuon, L., List. 380.

Tryphon, L., List. 380.

Undetermined: Umb. 179, 177, 181, 178,
180, 188, 190, 192, 193, 194, 195, 185,
186, 182, 174; Cruc. 37; Parn, 157;
Rut. 84; Salix 378; Malv. 69; Ros.
133 ; Lub. 338 ; Adoxa 198.

F, Sphegide (in the sense of Fossores,
Latr.) (81 species, 275 visits).
Agenia punctum, F., L., Rut. 84.
Ammophila sabulosa, L. (4), L. Sld. T,

THE FERTILISATION OF FLOWERS.

Th., Sed. 162 ; Umb. 172; Ciuc. 29;
Bry. 171; Geran. 78; Onagr. 166; Ros.
135, 140, 183 ; Papil. 96 ; Ech. 310;
Lab. 340; Ascl. 295; Rubiac. 205;
Caprif. 201 ; Jas. 283 ; Comp. 248, 225
(19 visits).

Bembex rostrata, F. (7—8), L., Scab.
211 ; Comp. 248.

Cemonus unicolor, F., L. Th., Umb. 177,
190 ; Crue. 37.

Cerceris albifasciata, Dlb., Th., Umb.
172.

arenaria, L. (1s—2), L. Th., Res. 44 ;

Ros. 133 ; Jas. 283 ; Comp. 248, 225.

labiata,-F., L. Th., Umb. 172; Res.

44; Fagop. 369; Scroph. 327; Jas. 283;

Comp. 225, 220. ;

Nasuta, K1. (quinquefasciata, Rossi,
v. d. L., Sm., interrupta, Pz.), L..Th.,
Umb. 172; Fagop. 369 ; Onagr. 166;
Ros. 135; Scroph. 327; Jas. 283; Comp.
248,

—— variabilis, Schrk. (ornata, F.), L.
Th., Umb. 172, 179, 195; Crue. 37 ;

Res. 42, 44; Cary. 52; Lab. 340; Comp. ©

248, 246, 225, 229, 231, 227.

Ceropales maculata, F. (1), L. T. Th.,
Umb. 191, 194, 196, 195; Jas. 283;
Comp. 242, 225, 222.

variegata, F., Th., Umb. 190.

Crabro alatus, Pz., L., Onagr. 166 ; Jas.
283 ; Comp. 248, 222, 227. :

cephalotes, Pz. (Shk., Lepel., H.
Sch.), L., Umb. 179, 185 ; Comp. 229.

—— cribrarius, L., L. Th., Umb. 191,
194, 184; Comp. 248, 222, 227.

denticrus, H. Sch., Th., Umb. 192.

—— dives, H. Sch., L., Umb. 178.

—— elongatulus, v. d. L. (luteipalpis,
Lep.), L., Rut. 84.

—— lapidarius, Pz., Dlb. (chrysostomus,
Lep., xylurgus, Shk.), L. Th. Sld.
Tekl., Umb. 179, 177, 178, 190, 194 ;
Ros. 133 ; Comp. 225.

patellatus, v. d. L., L., Ros, 149,
135 ; Ech. 310 ; Jas. 283.

—— podagricus, H. Sch., Th., Umb. 192.

—— pterotus, F., L., Umb. 177, 178;
Jas. 283.

sexcinctus, v. d. L. (1), L. T. Th.,
Umb. 179, 192, 193, 185 ; Comp. 262.

—— subterraneus, F., L. Th., Umb.
183; Comp. .

—— vagabundus, Pz., L., Umb. 177.

vagus, L., L., Th., Umb. 179, 178,
191, 194, 196,

—— vexillatus, Pz., Th., Umb. 192.

—— Wesmaeli, v. d. L., Th., Umb. 192;
Crue. 27.

—— spec., L., Comp. 233.

Dinetus pictus, F. (14), L., Umb. 194;
Comp. 248, 225, 234.

Entomognathus brevis, v. d. L., L.,
Umb. 184,

~~

Pp

eS eee

INDEX OF INSECTS.

Gorytes campestris, L.' (1), L. Sld.,
mb. 179, 177, 194; Parn. 157;
Rhus 88.

—— mystaceus, L. (1), L. T., Clem. 1;
Bry. 171; Ros. 134.

Hoplisus laticinctus, Lep..(1), Th., Umb.
179, 185,

Lindenius albilabris, F., L., Lab. 340 ;
Jas, 283 ; Comp. 248, 253, 225.

Mellinus arvensis, L., ea Comp. 234.

sabulosus, Dlb., L., Jas. 233,

Mimesa bicolor, Shuck, Th., Umb. 194.

—— unicolor, v. d. 1G i Th., Umb.
194.

Miscus campestris, Latr. (4), L. Th.,
All. 393; Ros. 135; Jas. 283.

Mutilla europea, L. (14), Th., Umb. 193,
195.

Myrmosa melanocephala, F., L. Th.,

mb. 179, 192, 183.

Nysson maculatus, v. d. L., Th., Umb.
191.

Oxybelus bellicosus, Ol., L., Umb. 179,
196 ; Jas. 283.

— bellus, Dib. (14 guttatus, Sh.), L.,
Sed. 162; Umb. 179; Crue. 38 ; Rut,
84; Ros. 141, 142 ; Comp. 225.

— ‘bipunctatus, Ol., L., Umb. 179,
188, 195.

mandibularis, Dib., L., Jas. 283.

— trispinosus, F., L., Comp. 248, 225,

—— uniglumis, L. (14), L. T., Sed. 162 ;
Umb. 179, 192, 194, 196, 195, 186;
Clem. 1, 7; Cruc. 38; Rhus. 88;
Til. 73; Cary. 55; Ros. 135, 138,
140, 141, 142, 133; ’ Jas. 283 ; Comp.
248, 425, 229, 233 (23 visits.)

— spec., L., Geran. 79.

Passalcecus monilicornis, Dib., L., Ros.
133.

Philantbus* triangulum, F. (2—23), L.
Th., Umb. 172, 179, 190, 194; Jas.
283 ; Comp. 248, 225.

Pompilus chalybeatus, Schi., L., Comp.
225.

— cinctellus, v. d. L., Th., Umb.
192

— intermedius,
Umb. 195, 184.

neglectus, Wesm., L. Th., Umb.
179, 192, 195, 185 ; Ros. 183.

—— niger, F., L. T., Umb. 179, 195.

—— pected, Wetis Jaret Bie de 2 Mey
Umb. 194, 186, 183.

—— plumbeus, Dlb., L., Comp. 225.

—— rufipes, F., L., Jas. 283; Comp.
225.
he Schi., L., Umb. 179, 186.

Pane oy spi
x ap hceptaing to Frederick Smith the riginal
ns of Gorytes campestris, L., in Linnzus’
pyar on are only males of G. mystaceus, L.;
and the insect called G. campestris, L., in this
book must be called G. Fargei, Shuck.

Schenck, L. Th.,

651

Pompilus trivialis, Kl., L., Umb. 188,
174; Fagop. 369 ; Comp. 225.

viaticus, Scop. 1(F., not L.!) (1—14),
L. Sld. Th., Umb, 188, 189, 191, 194,
195, 185 ; Parn. 157 ; Hott. 289 ; Jas.
283 ; Comp. 225, 222, 264, 271.

— spec., Ley Corn, 197.

Priocnemis bipunctatus, F.,? Th., Umb.
172, 191.

—— exaltatus, F., Th., Umb. 194.

—— obtusiventris, Schi., Th., Umb.
191, 195.

Psammophila affinis, K,? L. Th., Pap.

~ 101; Ech. 310; Lab. 348 ; Ascl. 295 ;
Scab. 211 ; Jas. 283 ; ; Comp. 259, 255.

— viatica, Le. bi “'Th., Umb. 191;
Veron. 327 ; Scab, 211.

Psen atratus, "Pz, (s— 3), L. Th., Umb.
192; Ros. 133.

Rhopalum clavipes, L., L., Rut. 84.

Salius sanguinolentus, F., Tis Comp. 248.

Scolia_bicincta, hortorum, 4punctata
(34), Ascl. 295.

Tachytes pectinipes, v. d. L.,4 L. Th.,
Umb. 191, 192; Jas. 283.

— unicolor, Pz., Th., Umb. 192.

Tiphia femorata, F., L. Th., Umb. 172,
191, 192, 193, 194, 195.

— minuta, v. d. L., L., Crue. 27;
Rut. 84.

ruficornis, Kl. (1), L., Umb. 188.

Trypoxylon clavicerum, Latr. (3), Th.,
Umb. 192.

— figulus, L. (3), L., Rut. 84.

G. Tenthredinide (38 species, 125 visits).

Athalia rose, L., L. Th., Umb. 178, 188,
190, 194, 195, 185, 183.

— spinarum, F, L,., Umb. 177 ; Fagop.
369

Cephus pallipes, K]., L., Ran. 8 ; Cary.

—. ‘spinipes, Pz., L., Ran. 7 ; Crue. 40,

troglodytes, i, o Umb. 177.

—— spec., L., Ran. 7, 8; Cruc. 40;
Comp. 267, 274.

Cimbex sericea, L., L. Sld., Umb. 179,
177, 181, 194; Comp. 229.

Dolerus cenchris, Htg., T., Umb. 183.

eglanterie, F. (3—1), L., Umb.

177 ; Salix 378, 379.

T According to Frederick Smith the specimens
of this species in Linneus’ collection are identi-
cal with Sphex fusca, L., and the species must
therefore be called P. fuscus, L

2 According to F. Smith = P. variabilis, Rossi.

3 According to F. Smith this species, from
the original type-specimens in Fabricius’ collec-
tion in Kiel, is identical with P. lutaria, F.,
which name has priority.

4 According to F. Smith the Linnean type-
specimens of Sphex pectinipes, F., show it to
be a Pompilus, and what is called Tachytes
pectinipes, lu., in this book, must be called 7,
pompiliformis, Pz.

652 THE FERTILISATION OF FLOWERS.

Dolerus gonager, K1., L., Salix 378 ; Ros.
151, 127.

-—— madidus, K1., L., Salix 378.

Hylotoma ccerulescens, F., L. T., Umb.
177, 194, 182.

enodis, L., L. Th., Umb. 177, 183.

—— femoralis, Kl., L. Th., Umb. 179,
177, 194, 195, 185.

rosarum, F., L. Th., Umb. 179,
177, 181, 175, 194.

—— segmentaria, Pz., Th., Umb. 183.

— ustulata, L., L. Sld., Umb. 179,
194, 14.

—— vulgaris, Kl., L. Th., Umb. 179,
194.

Macrophya neglecta, KI., T., Umb. 185.

Nematus capree, L., L., Ros. 151.

hortensis, Htg., L., Umb. 185.

— myosotidis, F., T., Umb. 185.

—— rufescens, H., L., Salix 378.

vittatus, Lep., L., Umb. 185, 174.

Selandria serva, F. (?—1), L., Umb. 179,
177, 181, 194, 195, 185.

Tarpa cephalotes, F., Th., Comp. 238.

Tenthredo annulata, F., L., Umb. 194,
185.

atra, L., L., Umb. 179.

bicincta, L., L. Sld., Umb. 181;

Ros. 133.

bifasciata, L., L. Th., Umb. 179,
177, 181, 194, 183.

—— flavicornis, L., T,, Umb. 179, 184,
182,

marginella, Kl., L., Rhus 88.

— notha, K]. (14), L. T. Th., Sed. 164 ;
Umb. 179, 177, 181, 178, 189, 194,
196, 195, 185, 184, 183; Comp. 238,
225, 229; 297.

rape, Kl., L., Umb. 185; Rubiac.
206.

rustica, L., L. T., Umb. 185, 184;

Ros. 134.

scrophularie, L., L. T., Onagr. 166 ;

Comp. 225, 229.

tricincta, F., L. T., Umb. 177, 194.

—— spec., L. Th., Umb. 179, 177, 181,
192, 193, 194, 185, 184, 183, 174;
Hyper. 68*; Ros. 134; Papil. 96* ;
Comp. 248, 225, 229, 272.

H. Vespide (18 species, 74 visits).

Eumenes pomiformis, Rossi (2), L., Umb.
192; Bry. 171; Rhamn. 86; Rhus
88

Odynerus debilitatus, Sauss., Th., Umb.
190, 192.

elegans, Wesm.,T., Umb. 179, 185.

—— parietum, L. (2), L. T. Th., Umb.
172, 192, 193, 194,-196, 184; Clem. 1;
Res. 44; Bry. 171; Salix 378; Rut.
84; Cary. 55; Poterium*; Ech. 310 ;
Prim. 290* ; Scab. 211; Comp. 225,
234,

Odynerus quinquefasciatus, F. (spinipes,
L.), L. T., Umb. 179; Ran. 7; Rhus
88 ; Geran. 78; Ros. 133.

—— simplex, F. = reniformis, Wesm.,-

L. Th., Cary. 55; Papil. 212*.

—— sinuatus, F. (according to Smith =
bifasciatus, L.) (13), L. Sld., Umb.
190, 194, 195; Rhus 88; Ros. 132* ;
Comp. 225.

- spinosus, H. Sch., L., Ran. 7.

—— trifasciatus, F. (gazella, Pz.), L.

Sld., Umb, 194 ; Papil. 108*.
~— spec., L., Ol. 291* ; Caprif. 201.
Polistes gallica, F. (including P. diadema),

Th.,.Umb. 172, 175, 191, 192, 193;

Secroph. 319; Lab. 339; Ascl. 295;
Symphor. 201 ; Comp. 240, 257, 250.
Pterocheilus phaleratus, Latr., L., Comp.
225.
Vespa germanica, F., L., Salix 3878;
Scroph. 322.
holsatica, F. (3-33), L. Th., Umb.
194; Berb. 18; Scroph. 322; Eric.
287 ; Symphor. 201.
— media, Deg., L. Th., Scroph. 322 ;
Symphor. 201.
rufa, L., L., Umb. 190, 194; Berb.
18 ; Scroph. 322 ; Eric. 285 ; Symphor.
201.
—— saxonica, F., Th., Symphor. 201.

Scroph. 322.

V. LEPIDOPTERA (79 species, 365
different visits).
A. Bombyces (3 species, 3 visits).
Dasychira pudibunda, L. (0), L., Caprif,
202*

Euchelia Jacobee, L., L., Cruc. 29.
Porthesia aurifiua, S. V., L., Pap. 90*.

B. Microlepidoptera (6 species, 13 visits).

Adela sulzella, 8S. V., L., Ros. 133.

—— spec., L., Umb. 177; Salix 378;
Lab. 339; Seab. 211.

Ephestia elutella, Hiibn., L., Scroph.
317.

Botys purpuralis, L., L., Scab. 211, 212;
Jas. 283; Comp. 199, 234.

nemotois, Hb., spec., L., Umb. 195.

Tortrix plumbagana, Tr., L., Ros, 133.

C. Noctuce (10 species, 42 visits).
Agrotis pronuba, L., L., Dianth. 54 ;
Eryth. 298.
Anarta myrtilli, L., L., Comp. 229.

Brotalamia meticulosa, L., L., Dianth. ~

54.

Cucullia umbratica, L. (18—22), L.,
Caprif. 202.

Dianthecia capsincola, 8. V. (23— 25),
L., Caprif. 202.

vulgaris, L. (2—23), L., Umb. 194;

INDEX OF INSECTS.

Euclidia glyphica, L. (7), L., Ran. 7 ;
Cruc. 40; Cary.j 57; Papil. 90+t, 94t,
116+ ; Seroph. 334 ; Lab. 366; Scab.
211 ;-Comp. 249.

— Mi, L., L., Comp. 267.

Hadena didyma, Esp., L., Comp. 234.

Mamestra serena, 8. V., Th., Seab. 211.

Plusia gamma, L. (15), L. Th., Lin. 75 ;
Dianth. 53, 54; Papil. 100, 94, 1111,
122}, 116+; Ech. 310; Bor. 302; Lab.
353, 846+; Eryth. 298; Caprif. 202 ;
Scab. 212; Comp. 257, 259, 253, 246,
244, 221, 271, 273 (28 visits).

D. Rhopalocera (46 species, 259 visits).

Argynnis Aglaia, L., Sld. Th., Lab. 340 ;
Comp. 248, 237.

Paphia, L., Th. Westf., Umb. 190 ;
Ros. 135; Lab. 371; Comp. 214.

Colias Hyale, L., L. Th., Dianth. 53 ;
Papil. 94; Ech. 310; Lab. 364 ; Scab.
211 ; Comp. 257, 256, 271, 260.

— (Rhodocera) rhamni, L., L. Sld.
Th., Cruc. 30; Viol. 47, 48, 49;
Dianth. 53 ; Lythr. 165; Papil. 122 ;
Bor. 304; Lab. 366, 350 ; Comp. 249,
274.

Hesperia (Syrichthus) alveolus, Hb., L.
Sld., Viol. 49; Papil. 90t; Lab. 366 ;
Comp. 229, 274.

— lineola, 0., L., Umb. 195; Scab.
211 ; Comp. 214.

—— (Carterocephalus) Paniscus, Esp.,
L., Ros. 135.

-— silvanus, Esp., L. Sld., Hyper. 68* ;
Malv. 72; Cary. 59; Papil. 100, 122;
Ech. 310; Lab. 355 ; Comp. 248, 253,
225, 272.

—— (Erynnis) Tages, L., L., Papil. 90f.

—— thaumas, Hfn. (linea, S. V.), L.,
Papil. 100, 101, 94+; Bor. 303; Jas.
283 ; Comp. 257, 223.

spec., L. Th., Delph. 15f; Viol.
49 ; Papil. 98+, 94+ ; Lab. 366 ; Comp.
229, 274. ‘

Lycena Mgon, S. V., L., Jas. 283;
Comp. 225.

— Alsus, 8. V., Th., Papil. 91* ; Comp.
221.

Argiolus, L., L., Salix 378; Papil.
94; Lab. 355 ; Eric. 285 ; Comp. 267.

— Icarus, Rott. (Alexis,S. V.), L., Ran.
7; Cary. 57; Papil. 90t;. Bor. 307 ;
Lab. 340 ; Comp. 268. ;

spec., L. Th., Papil. 94f, 116t ;
Ech. 310 ; Comp. 257, 223, 214.

Melita Athalia, Esp., Sld. Th., Lil.
391; Papil. 355 ; Comp. 258, 230.

Cinxia, L. (10), L., Ech. 310.

Papilio Machaon, L. (18), L. Th., Lil.
391; Ol. 291; Scab. 210.

— Podalirius, L., L., Lab. 366; Ol.
291.

653

Pieris brassice, L. (15), L. Th., Crue.
30, 34; Viol. 48; Fagop. 369; Cary.
57, 59 ; Ros. 129 ; Papil. 98t, 100, 94 ;
Ech. 310; Bor. 309; Lab. 366, 364,
358, 349, 343; Ol. 291; Comp. 257,
248, 250, 253, 246, 267, 264, 275, 262
(27 visits).

—— (Anthocharis) cardamines, L. (11—
12), L.,:Cruc. 30; Viol. 48 ; Ol. 291.

— crategi, L. (17), L., Ros. 135.

—— napi, L. (11), L., Cruc. 30, 34, 36;
Viol. 48, 49; Bry. 171; Geran. 82;
Fagop. 369; Cary. 65; Ros. 135;
Papil.s 115¢; Bor. 309; Lab. 366;
Ol. 291; Comp. 257, 253, 245, 225,
266, 274; Valer. 209 (23 visits).

rape, L. (12), L., Umb. 196 ; Cruc.
34, 36; Viol. 48, 49; Geran. 76;
Maly. 69 ; Polygon, 371; Dianth. 52 ;
Cary. 57 ; Lythr. 165 ; Ros. 129 ; Pa-
pil. 100, 94, 121, 122, 117; Lab. 366,
353 ; Ol. 291 ; Scab. 212 ; Comp. 253,
245, 214, 262 (25 visits).

Polyommatus dorilis, Hfn. (Circe, S. V.),
L., Jas. 283; Comp. 234, 223, 221,
217.

—— Eurydice, Rott., L., Polygal. 51.

— phleeas, L., L. Th., Ran. 7 ; Fagop.
369; Cary. 60, 53; Scab. 212; Jas.
283 ; Comp. 330, 346, 234, 238 (10
Visits).

Satyrus (Pararga) Egeria, L., Westf.,
Comp. 214.

—— (Epinephele) Galatea, L., Westf.,
Comp. 257, 255, 214.

—— (Epinephele) Hyperanthus, L., L.
Sld., Lab. 342, 343; Comp. 238.

—— (Epinephele) Janira, L. (10), L.,
Hyper. 68; Dianth. 52; Papil. 100;
Ech. 310; Lab. 340, 342, 337; Jas.
283 ; Scab. 211, 212; Comp. 257, 258,
248, 253, 229, 262.

—— (Erebia) Medea, S. Y., Sld., Scab.
211,

—— (Erebia) Medusa, S. V., Westf.,
Comp. 214.

—— (Pararga) Megera, L., L., Papil.
100, 108 ; Comp. 257, 266, 274.

—— (Cenonympha) Pampbilus, L., L.
Sld. Th., Ran. 6, 7; Lab. 340; Jas.
283 ; Comp. 257, 225, 217.

spec., L., Delph. 15¢ ; Papil. 121.

Thecla ilicis, Esp., L., Comp. 215.

quercus, L., Westf., Comp. 214.

— rubi, L., L., Papil. 95; Eric. 285;
Comp. 248.

spec., L., Camp. 257, 216, 217.

Vanessa Atalanta, L., L., Comp. 234.

C-album, L. (11), L., Umb. 188.

— cardui, L., L. Th., Lab. 364.

Io, L. (15—16), L. Sld., Salix 379 ;

Papil. 122; Comp. 237, 214, 274.

urtice, L. (12), L. Sld., Viol. 47 ;

Salix 378 ; Fagop. 369 ; Papil. 100, 94,

654 THE FERTILISATION OF FLOWERS.

122; Lab. 364; Ol. 291; Scab. 211;
Comp. 255, 248, 237, 218, 266, 275
(15 visits).

E. Sphinges (14 species, 48 visits).

Ino Statices, L., L. T. Sld., Cary. 57 ;
Onagr. 166; Scab. 211; Camp. 277 ;
Jas. 283 ; Comp. 229.

Macroglossa fuciformis, L., L., Cary. 57 ;
Lab. 366, 349 ; Ol. 291.

— stellatarum, L., L. Sld. Th., Dianth.
53; Onagr. 169; Ech. 310; Lab. 364,
349; Eryth. 298; Ol. 291; Comp.
255.

Sesia asiliformis, Rott. (S. cynipiformis,
Esp.), Th., Papil. 94¢ ; Comp. 238.
—— empiformis, Esp., Sld. Th., Papil.

90+ ; Lab. 340.

—— tipuliformis, L., L. T., Cruc. 38;
Lab. 340; Comp. 232.

Sphinx convolvuli, L. (65—80), L., Con-
volv. 311* ; Caprif. 202.

—— (Deilephila) Elpenor, L. (20—24),
L., Caprif. 202.

ligustri, L. (37—42, L.,) Sapon. 56 ;

Caprif. 202.

pinastri, L. (28—33), L., Caprif.
202.

--— (Deilephila) Porcellus, L. (20), L.,
Cary. 58 ; Caprif. 202.

Sphinx (Smerinthus) tilie, L. (8), L.,
Caprif. 202*.

Zygexna carniolica, Scop. (Zonobrychis
S. V.), Th., Dianth. 53; Pap. 94f,
119t ; Comp. 257, 258, 248, 249.

loniceree, Esp., L. Th., Papil. 90+ ;

Ech. 310; Scab. 211; Comp. 247,

257.

VI. NEUROPTERA (4 species, 13 visits).

Agrion spec., L., Ros, 133.

Hemerobius spec., L., Umb. 195, 185.

Panorpa communis, L., L. Sld. T., Umb.
179, 181, 190; Rhus 89; Ros. 133;
Scroph. 317 ; Comp. 214, 234.

Sialis lutaria, L., L., Umb. 177, 185.

VII. ORTHOPTERA (3 species, 8 visits).

Forficula auricularia, L., L., Papav. 20;
Camp. 282.
Podura spec., L., Convolv. 311*.

VIII. THYSANOPTERA (18 visits).

Thrips spec., L., Ran. 9, 10; Crue. 30,
39; Res. 42; Cary. 65, 66, 60, 63;
Lythr. 165; Ros. 151, 188; Convolv.
311* ; Scroph. 317; Lab. 339; Vince.
293 ; Eric. 287.

SuMMARY OF INSECT-VISITS NOTED IN THIS Book.

Coleoptera .........- 129 species with 469 visits.
Diptera ........... 258 Fo 1598 ,,
Hemiptera ......... i 30
Hymenoptera ... 368 . 2750s,
Lepidoptera ..... 79 ra 365,
Neuroptera ...... 4 “ a
Orthoptera......... 3 ae 3.
Thysanoptera 1 oa | ee

Altogether...

843 species, with 5231 different visits.

INDEX OF PLANTS,

WITH THE NUMBER OF THEIR INSECT-VISITORS.

ABBREVIATIONS.—Coleopt. = Coleoptera; Dipt. = Diptera in general ;
Muse. = Muscide ; Syrph. = Syrphide ; Rhing. = Rhingia; Hemipt. =
Hemiptera ; Hymen. = Hymenoptera, not including the bees; Apid. =
Apide in general ; A*, = Apis mellifica; B. = Bombus and Anthophora (the
longest-tongued of our bees) ; Lepid. = Lepidoptera in general; Lepid. d. =
diurnal Lepidoptera ; Lepid. n. = nocturnal Lepidoptera; Newropt. =
Neuroptera ; Orthopt. = Orthoptera ; Th. = Thrips.

The figures placed after these abbreviations indicate the number of species
of insect-visitors observed. Groups of insects which are useless in the work
of fertilisation are placed in square brackets [_ ].

ABUTILON, p. 145.

Acacia Julibrizzin, p. 220.

Acanthacee, p. 467.

Acanthus, p. 468.

Acer, p. 164.

Achillea Millefolium, No. 225 (Apid. 30,
Hymen. 25, Dipt. 21, Lepid. 6, Coleopt.
5), p. 325.

A. Ptarmica, No. 226, p. 327.

Aconitum Lycoctonum, No. 17 (B. 1),

p. 87.

A. Napellus, No. 16, p. 86.

A. septentrionale, p. 88.

Adenostemma, p. 318.

Adonis vernalis, p. 73.

Adontostyles, p. 361.

Adoxa moschatellina, No. 198 (Dipt. 4,
Hymen. 3, Coleopt. 1), p. 289.

Aichmanthera, p. 467.

Agiphila elata, p. 469.

Z. mollis, p. 469.

ZE. obdurata, p. 469.

Jigopodium Podagraria, No. 179 (Dipt.
34, Coleopt. 21, Hymen. 33, Apid. 15,
Neuropt.1), p. 276.

#Esculus Hippocastanum, No. 87 (Apid.
7), p. 164.

4. rubicunda, p. 166.

Agathea, p. 361.

Agrimonia Eupatorium, No. 145 (Syrph.
9, Muse. 1, Api. 1), p. 235,

Agrostis alba, p. 568.

Ajuga genevensis, p. 502.

A. pyramidalis, p. 502.

A. reptans, No. 366 (Apid. 15, Syrph.
1, Lepid. 7), p. 501.

Alchemilla alpina, p. 235.

A. fissa, p. 235.

A. pentaphylla, p. 235.

A. vulgaris, No. 144 (Syrph. 5), p. 234.

Alisma natans, p. 567.

A. Plantago, No. 398 (Syrph. 5), p. 565.

Alismacee, p. 565.

Alliaria officinalis, No. 35, p. 109.

Allium carinatum, p. 554.

A. Cepa, No. 393 (Apid. 3, Hymen. 3,

Dipt. 1), p. 553.

. fistulosum, p. 554.

. rotundum, p. 554.

. Schcenoprasum, p. 554,

. sibiricum, p. 554.

. Spherocephalum, p. 554.

. ursinum, No. 392 (B. 1), p. 553.

. victoriale, p. 554.

Alocasia odora, p. 564.

Alopecurus pratensis, p. 568.

Alpinia, p. 542.

Alsinex, p. 131.

Amarantacee, p. 509.

Amaryllidee, p. 559.

Ambrosinia Bassii, p. 565.

Amelanchier vulgaris, p. 242,

> > > >

656 THE FERTILISATION OF FLOWERS.

Ambherstia nobilis, p. 220.
Ammannia latifolia, p. 261.
Amorpha canescens, p. 198.

A. fruticosa, p. 198.
Amorphophallus campanulatus, p. 5638.
A. Titanum, p. 564.

A. variabilis, p. 564.
Amphbicarpea monoica, p. 214.
Amsinckia, p. 422.

Anacamptis pyramidalis, p. 534.
Anacardiacee, p. 166.
Anagallis arvensis, p.. 390.

A. coerulea, p. 390.

Anandria, p. 351.

Anchusa officinalis, No. 302 (Apid. 6,

Lepid. 1), p. 411.

Andromedex, p. 376.

Androsace Chamzjasme, p. 389.

A. obtusifolia, p. 389.

A. septentrionalis, p. 389.

A. Vitaliana, ‘p. 389.

Anemone alpina, p. 73.

A. narcissifolia, p. 73.

A. nemorosa, No. 4 (Apid. 5, Muse. 2,
Coleopt. 1), p. 72.

A. ranunculoides, p. 88.

A. silvestris, p. 88.

Anethum graveolens, No. 192 (Dipt. 15,
Hymen. 25, Apid. 6), p. 283.

Angelica silvestris, No. 190 (Dipt. 11,
Coleopt. 6, Apid. 2, Hymen. 9, Lepid.
1, Newropt. 1), p. 282,

Angrecum, p. 528.

Anoda hastata, p. 145.

Anonacee, p. 90.

Anthemidew, p. 325.

Anthemis arvensis, No. 227 (Apid. 8,
Hymen, 4, Dipt. ’9, Coleopt. 3), p. 329.

A. tinctoria, No. 228 (Apid. 3, Hymen. 1,
Dipt. 6, Coleopt. 2), p. 329.

Anthericum Liliago, p. 553.

A. ramosum, No. 391 (Apid. 1, Syrph.
1, Lepid. 2), p. 552.

Anthoxanthum odoratum, p. 568.

Anthriscus epee No. 186 (Dipt. 11,
Coleopt. 7, Hymen. 5, Apid. 3), p. 281.

4. silvestris, No. 185 (Dipt. 26, Coleopt.
20, Hymen. 20, Apid. 5, Newropt. 2),
p- 879,

Anthurium Pothos, p. 565.

Anthyllis vulneraria, No. 91 (Apid. 4),

p. 172.

Auta majus, No. 321 (B. 5, [Apid.
3]), p. 433.

Aphelaideh aig 54 | p- 468.

Apocynacer, p. 394.

Apocynum androsemifolium, p. 396.

A. hypericifolium, p. 396.

Aquilegia vulgaris, No. 13 (B. 2, [Apid.
4]), p. 81.

Arabis alpina, p. 102.

A. bellidifolia, p. 102.

A. hirsuta, No. 29 (Hymen. 1, Apid. 1,
Lepid, 1); p . 102.

Arachis, p. 201.

Araliaceee, p. 287.

Araujia albens, p. 400.

Arbutus, p. 375.

Arbutez, p. 375.

Arctium minus, p. 338.

A. tomentosum, p. 338.
Arctostaphylos uva-ursi, p. 375.
Arctotis, p. 361.

Arenaria muscosa, p. 137.

A. trinervia, No. 57 (Coleopt. 1), p. 186.
Argemone ochroleuca, p. 94.
Arisema filiforme, p. 564.
Arisarum, p. 564.

Aristolochia Bonplandi, p. 518.

A. Clematitis, No. 375 (Dipt. 8), p. 517.

A. grandiflora, p. 519.

A. Sipho, No. 376 (Dipt. 5), p. 518.

Aristolochiacee, p. 517.

Armeria, p. 382.

Armoracia amphibia, No. 28 (Hymen. 1,
Dipt. 4), p. 102.

Arnebia, p. 422.

Arnica montana, No. 237 (Apid. 3, Dipt.

10, Lepid. 3, Coleopt. 2), p. 335.
Aroidew, p. 562.
Aronia rotundifolia, p. 242.

Artemisia Dracunculus, No. 2385 (Syrph.

1), p. 333.

Artocarpex, p. 521.

Arum crinitum, p. 564.

A. Dracunculus, p. 564.

A. italicum, p. 563.

A. maculatum, No. 397 (Dipt. 1), p. 562.

A. ternatum, p. 564.

Asarum canadense, p. 517.

A. europxeum, p. 317.

Asclepiadex, p. 396.

Asclepias Cornuti, No. 295 (Apid. 10,
Hymen. 7, Dipt. 7), p. 396.

A. curassavica, p- 400.

A, fruticosa, p. 400.

A. tenuifolia, p. 400.

Asimina triloba, p. 90.

Asparagus officinalis, No. 888 (Apid. 5),
p. 548.

Asperula azurea, p. 304.

A. ee No. 207 (Dipt. 1, Apid.
1), p

A. odorata (A*.), p. 304.

A. pusilla, p. 306.

A. scoparia, p. 306.

A. taurina, p. 303,

Aspicarpa urens, p. 149.

Aspidistra elatior, p. 560.

Aster alpinus, p. 322.

A. Ariélins: NS No. 219 (Syrph. 1)? . 322.

A. chinensis, No. 218 (Syrph. 2 evi
1, Apid. 1), p. 322.

Asteroides, p. 820.

Astrantia major, No. 178 bl oncat 3; ee
3, Coleopt. 1), P- 272,

AV minor, p.. 273."

Ataccia celatatds p. 558,

|

ii A

INDEX OF PLANTS.

Atherurus tripartitus, p. 564.
Atragene alpina, p. 70.
Atropa Belladonna, p. 427.
Azalea procumbens, p. 380.

BALLOTA NIGRA, No. 364 (Apid. 14,
Lepid. 7), p. 498.

Balsaminez, p. 160.

Barbarea vulgaris, p. 104.

Bartsia alpina, p. 445.

Bellidiastrum, p. 361.

Bellis perennis, No. 217 (Apid. 8,
Hymen. 1, Dipt. 13, Lepid. 2, Coleopt.
3), p. 821.

Berberidex, p. 90.

Berberis vulgaris, No. 18 (Dipt. 11, Apid.
10, Hymen. 2, Coleopt. 2), p. 90.

Bergenia crassifolia, No. 156 (Apid. 2),
p. 247.

Betonica officinalis, No. 354 (B.1, [Syrph.
2, Lepid. 1}), p. 487.

Biarum, p. 565.

Bidens, p. 361.

Bignonia, p. 466.

Bignoniacee, p. 466.

Biscutella levigata, p. 108.

Bonjeania hirsuta, p. 173.

Boragez, p. 408.

Boraginez, p. 408.

Borago officinalis, No. 301 (Apid. 5), p.

409.

Borreria, p. 304.

Boucerosia, p. 401.

Brachypodium pinnatum, p. 568.

Brassica oleracea, No. 39 (Coleopt. 1,
Apid. 6, Th. 1), p. 111.

B. Rapa, p. 112.

Bromus mollis, p. 568.

Browallia elata, p. 427.

Brugmansia Zippelii, p. 516.

Bryonia dioica, No. 171 (Apid. 7, Hymen.
4, Coleopt. 1, Lepid. 1), p. 268.

Bryophyllum calycinum, p. 251.

Bunchosia Gaudichaudiana, p. 149.

Bupleurum faleatum, No. 175 (Dipt. 4,
Hymen. 8, Apid. 1), p. 275.

B. rotundifolium, p. 286.

Burlingtonia, p. 528.

Buxus, p. 520.

CACALIA, p. 361.

Cesalpiniaceee, p. 220.

Caffea arabica, p. 304.

Cajophora lateritia, p. 267.

Calamintha Acinos, No. 344 (Apid. 1,
Dipt. 1), p. 477.

C. alpina, p. 477.

C. ane ium, No. 348 (Lepid. 2), p-

6

476.
C. Nepeta, p. 476.
Calathea discolor, p. 542.
C. zebrina, p. 542.
Calceolaria, p. 431.

657
Calendula, p. 361.
Calla palustris, p. 565.
Callitriche verna, p. 255.
Calluna vulgaris, No. 287 (Apid. 9,

Hymen. 1, Dipt. 6, Th. 1), p. 377.

Calogyne, p. 364.

Calonyction, p. 425.

Caltha palustris, No. 11 (Dipt. 7, Coleopt.
1, Apid. 4), p. 79.

Calycanthacee, p. 89.

Calycanthus floridus, p. 89.

Calystegia sepium, p, 424. .

Camarea, p. 149.

Campanula bononiensis, No, 280 (Apid.
4, Coleopt. 1), p. 368.

C. canescens, p. 369.

C. colorata, p. 369.

C. Medium, p. 366.

C. patula, No. 281 (Apid. 2), p. 368.

C. persicifolia, No. 282 (Apid. 1,
[Orthopt. 1]), p. 368.

C. pusilla, p. 367.

C. rapunculoides, No. 279 (Apid. 9,
Rhing. 1), p. 368.

C. rotundifolia, No. 277 (Apid. 10, Dipt.
2, Lepid. 1, Coleopt. 3), p. 368.

C. Trachelium, No. 278 (Apid. 9, Dipt.
2, Coleopt. 2), pi 368.

Campanulaceee, p. 365.

Campanulez, p. 366.

Canna, p. 543.

Canneee, p. 543.

Capparidez, p. 114.

Capparis, p. 114.

Caprificus, p. 521.

Caprifoliacee, p. 289.

Capsella bursa-pastoris, No. 37 (Lepid.
7, Muse. 1), p. 110.

Cardamine ehenopodifolia, p. 104.

C. impatiens, p. 104.

C. pratensis, No. 30 (Apid. 9, Dipt. 6,
Lepid. 4, Coleopt. 1, Th. 1), p. 102.

Cardiospermum, p. 164.

Carduus acanthoides, No. 246 (Apid. 32,
Hymen. 1, Dipt. 3, Lepid. 4, Coleopt.
4), p. 339.

C. crispus, No. 245 (Apid. 5, Syrph. 1,
Lepid. 2), p. 338. °

C. nutans, No. 247 (Apid. 5, Lepid. 1),
p. 340.

Carex hirta, p. 567.

C. montana, p. 567.

Carlina acaulis, No. 241 (Apid. 9, Coleopt.
1), p. 337.

C. vulgaris, No. 242 (Apid. 8, Hymen.
p. 1), 337.
Carum Carui, No. 177 (Dipt. 21, Coleopt.

5, Hymen. 17, Apid. 11, Lepid. 1,
Neuropt. 1), p. 275.
C. sativum, No. 176 (Dipt. 8, Amid. 10),

p. 275.
Caryophyllee, p. 125.
Cassia multijuga, p. 220.
Cattleya, p. 528.

658

Caucalis Anthriscus, No. 196 (Dipé. 1,
Hymen. 8, Lepid. 1), p. 286.

C, daucoides, p. 286,

Celastrinee, p. 162.
Centaurea Cyanus, No. 259 (Apid. 3,
Hymen. 1, Dipt. 3, Lepid. 1), p. 350.
C. Jacea, No. 257 (Apid. 28, Hymen. 1,
Dipt. 6, Lepid. 13), p. 346.

C. Scabiosa, No. 258 (Apid. 14, Dipt. 2,
Lepid. 3, Coleopt. 1, Hemipt. 1), p. 349.

Centranthus ruber, p. 308.

Centrosema, p. 215.

Centrostemma, p. 401.

Centunculus, p. 390.

Cerastium arvense, No. 60 (Dipt. 13,
Apid. 3, Culeopt. 1, Th. 1, Lepid. 1),

131

p- ‘

C. semidecandrum, No. 62 (Dipt. 3,
Apid. 1), p. 132.

C, triviale, No. 61 (Dipt. 2), p. 132.

C, viscosum, p. 133.

Cerinthe glabra, p. 421.

C. minor, p. 422.

Ceropejia elegans, p. 401.

Cherophyllum hirsutum, No. 183 (Dipt.
1, Coleopt. 2, Hymen. 11, Apid. 1), p.
278.

C. temulum, No. 184 (Dipt. 10, Coleopt.
5, Hymen. 7, Apid. 1), p. 279.

Chamedorea, p. 562.

Chameorchis, p. 532,

Chamissoa, p. 509.

Chapmannia, p. 201.

Chasalia, p. 304.

Chelidonium majus, No. 21 (Apid. 7,
Syrph. 5, [Dipt. 1]), p. 94.

Chelone, p. 434,

Chenopodiacee, p. 509.

Chenopodium album, p. 509.

C. ambrosioides, p. 509.

C. bonus-Henricus, p. 509.

Chimonanthus fragrans, p. 89.

Chrysanthemum corymbosum, No. 231
(Hymen. 1, Dipt. 1, Hemipt. 1), p. 331.

C. inodorum, No. 230 (Hymen. 1), p.
331.

C. leucanthemum, No. 229 (Apid. 12,
Hymen. 10, Dipt, 28, Lepid. 5, Coleopt.
17), p. 329.

C. Parthenium, No. 232 (Lepid. 1), p.
332.

Chrysocoma Linosyris, No. 221 (Apid.
4, Dipt. 4, Lepid. 3), p. 322.

Chrysosplenium alternifolium, No. 155
(Dipt. 5, Hymen. 4, Coleopt. 4), p.
245.

Chuquiraga insignis, p. 351.

Cichoriacew, p. 351.

Cichorium Intybus, No. 260 (Apid. 8,
Dipt, 3, Lepid. 1, Coleopt. 1), p. 351.

Cinchona, p. 304.

Circeea lutetiana, No. 170 (Dipt. 5), p.
265.

Cirsium, see Cnicus.,

*- C. ochroleucus, No. 252,

THE FERTILISATION OF FLOWERS.

Cistiner, p. 117.

Cistus hirsutus, p. 117.

C. villosus, p. 117.

Clematis balearica, p. 70.

C. integrifolia, p. 70.

C. recta, No. 1 (Apid. 7, Hymen. 3,
Syrph. 7, Muse. 1, Coleopt. 1), p. 69.

Cleome, p. 114. :

Clitoria mariana, p. 215.

Cnicus acaulis, p. 344. ,

C. arvensis, No. 248 (Apid. 32, Hymen.17,
Dipt. 24, Lepid. 7, Coleopt. 8), p. 340.

C. eriophorus, No. 251 (Apid. 1), p. 348.

C. heterophyllus, No. 254, p. 344.

C. lanceolatus, No. 250 (Apid. 6, Hymen.
1, Syrph. 3, Lepid. 2), p. 348.

p. 343.

C. oleraceus, No, 249 (Agid. 2, Lepid.
1), p. 343.

C. palustris, No. 253 (Aid. 9, Hymen.
1, Dipt. 4, Lepid. 6, Coleopt. 2), p. 348.

C. spinosissimus, p. 344.

~ Cobea penduliflora, p. 407.

C. scandens, p. 407.

Cochlearia officinalis, No. 32 (Syrph. 3,
Coleopt. 1), p. 105.

Cocos, p. 562.

Colchicum autumnale, No. 395 (B. 1),
p. 556.

Coleus, p. 471.

Collinsia bicolor, p. 436.

C. verna, p. 436.

Collomia, p. 407.

Combretacex, p. 255.

Combretum, p. 255.

Commelina bengalensis, p. 561.

Commelinacee, p. 561.

Composite, p. 315.

Conifer, p. 526.

Conium maculatum, No. 174 (Dipt. 5,
Coleopt. 3, Hymen. 4, Apid. 1), p. 274.

Conophallus Titanum, p. 564.

Convallaria majalis, No. 389 (4*.), p.
549.

C. multiflora, No. 390 (B. 2, Rhing. 1),
p. 550.

C. verticillata, p. 550.

Convolvulacez, p. 423.

Convolvulus arvensis, No. 811 (Apid. 6,
Dipt. 8, Coleopt. 3, Hymen. 1), p. 423.

C. sepium (Lepid. n. 1! [Dipt. 2, Apid.
2, Coleopt. 1, Orthopt. 1, Th. 1)) p. 424.

Conyza squarrosa, No. 220 (Apid. 10,
Hymen. 1), p. 322.

Cordia, p. 408.

Cordier, p. 408.

Coriaria myrtifolia, p. 167.

Coriariex, p. 167.

Cornacer, p. 287.

Cornus sanguinea, No. 197 (Coleopt. 12,
Dipt. 2, Hymen. 1), p. 287.

Coronilla Emerus, No. 113, p. 198.

C, glauca, p. 199.

C, minima, p. 199.

INDEX OF PLANTS.

Coronilla montana, p. 199.

C. varia, No. 114 (A*.), p. 198.

Correa, p. 162.

Cortusa, p. 389.

Corydalis cava, No. 23 (B. 1, [Apid. 6,
Dipt. 2}), p. 97.

C. lutea, No. 25 (B. 1), p. 99.

C. nobilis, p. 98.

C. ochroleuca, p. 98.

C. solida, No. 24 (B. 1, [Apid. 2, Dipt.
2]), p. 98.

Corylus Avellana, p, 523.

Cotoneaster vulgaris, No, 154, p. 241.

Crassulacere, p. 251.

Crategus Oxyacantha, No. 153 (Dipt.
24, Coleopt. 14, Apid. 19), p. 240.

Crepis biennis, No. 263 (Apid. 23, Dipt.
7, Coleopt. 1), p. 353.

C. tectorum, No. 264 (Apid. 8, Hymen. 1,
Dipt. 1), R 353.

C. virens, No. 265 (Apid. 9, Dipt. 8,
Ooleopt. 1), p. 353.

Crinum, p. 560.

Crocus sativus, p. 548.

C. vernus, p. 547.

Crucifere, p. 100.

Cryphiacanthus barbadensis, p. 467.

Cryptocoryne, p. 565.

Cryptostachys, p. 568.

Cryptostemma, p. 361.

Cucurbitacer, p. 268.

Cuphea floribunda, p. 261.

C. melvyilla, p. 261.

C, silenoides, p. 261.

Cupuliferz, p. 523.

Cuseuta Epithymum, p. 425.

Cynanchum Vincetoxicum, p. 401.

Cynaroidex, p. 336.

Cypella, p. 547.

Cyperaceer, p. 565.

Cyphiez, p. 366.

Cypripedine, p. 539.

Cypripedium barbatum, p. 541.

C. Calceolus, No. 386 (Apid. 5, [+ 1,
Dipt. 4, Coleopt. 1]), p. 539.

C. caudatum, p. 541.

Cytinacee, p. 516.

Cytisus albus, p. 195.

C. canariensis, p. 195.

C. Laburnum, No. 111 (Apid. 6, [Lepid.
1, Coleopt. 1}), p. 193.

C. sagittalis, p. 195.

C. scoparius, Ko, 112, p. 195.

D&DALACANTHUS, p. 467.

Dahlia, p. 361.

Dalechampia, p. 520.

Dampiera, p. 364.

Daphne mezereum, p. 519.

D. striata, p. 519.

Daucus Carota, No. 195 (Dipti. 19,
Coleopt. 10, Hymen. 19, Apid. 9, Lepid.
2, Hemipt. 1, Newropt. 1), p. 285.

D. grandiflora, p. 286.

659

Delphinium Ajacis, p. 86.

D. we Eeees No. 15 (B. 1, [Lepid. 2]),
p. 85.

D. elatum, No. 14 (B. 1), p. 83.

D, Staphysagria, p. 85.

Dendrobium, p. 527.

Dianthus atrorubens, p. 127.

D. Carthusianorum, No. 53 (Lepid. d. 7,
[Apid. 1]), p. 126.

D. chinensis, No, 54 (Lepid. d. 3), p.

127.

D. deltoides, No. 52 (Lepid. d, 2, [Syrph.
4]), p. 125.

D. silvestris, p. 127.

D. superbus, p. 127.

Diclytra cucullaria, p, 96.

D. eximia, p. 96.

D. spectabilis, No. 22 (B. 2, [Apid. 6]),
p. 95.

Dictamnus, p. 162.

Diervilla, p. 299.

Digitalis ambigua, p. 438.

D. lutea, p. 438.

D. purpurea, No. 323 (B. 3, [Apid. 2,
Coleopt. 3]), p. 437.

Dionysia, p. 389.

Dioscorea, p. 561.

Dioscoreacee, p. 561.

Diospyros virginiana, p. 392.

Diplacus, p. 426.

Dipsacee, p. 308.

Dipsacus silvestris, No. 210 (B. 3), p. 308.

Dipteracanthus, p. 467.

Doronicum, p. 361.

Dorycnium hirsutum, p. 173.

Draba aizoides, p. 105.

D. verna, No. 31 (Apid. 3), p. 105.

D. Wahlenbergii, p. 105.

Dracunculus vulgaris, p. 564,

Drosera, p. 255.

Droseracer, p. 255.

Drummondia, p. 243.

Dryas octopetala, p. 228.

EBENACEA, p. 392.

Echinops Ritro, p. 337.

E, spherocephalus, No. 240 (Apid. 5,
Hymen. 1), p. 336.

Echinospermum Lappula, p. 416.

Echium vulgare, No. 310 (Apid. 44,
Hymen. 5, Dipt. 6, Lepid. 9, Coleopt.
1), p. 418. :

Eleagnacee, p. 520.

Eleagnus, p. 520.

Empetracee, p. 526.

Empetrum, p. 526.

Epacridee, p. 382.

Epacris, p. 382.

‘Epidendree, p. 528.

Epidendrum, p. 529.

Epigzea, p. 376.

Epilobium alpinum, p. 264.

E. angustifolium, No. 166 (Apid. 10,
Hymen, 4, Dipt. 3, Lepid. 1), p. 261.

: oak Se

660 THE FERTILISATION OF FLOWERS.

Epilobium Fleischeri, p. 262.

E. hirsutum, p. 263.

E. origanifolium, No. 168 (Lepid. 1), p
263.

E. parviflorum, No. 167 (Coleopt. 1),
p- 262.

Epipactis latifolia, p. 532.

E. microphylla, p. 532.

E. palustris, p. 533.

E. viridiflora, p. 532.

Epipogon Gmelini, p. 533.

Eranthemum, p. 467.

Eranthis hiemalis, No. 12 (Dipt. 3, A, )
p. 80.

Eremurus spectabilis, p. 552.

Erica carnea, p. 377.

E. cinerea, p. 377.

E. tetralix, No. 286 (Apid. 7, Syrph. 3,
Lepid. 1), p. 376.

Ericacee, p. 375.

Ericee, p. 376.

Erigeron alpinus, p. 322.

E. uniflorus, p. 322.

Eritrichium, p. 422.

Erodium Cicutarium, No. 83 (Apid. 1,
Coleopt. 1), p. 158.

Ervum lens, p. 201.

Eryngium campestre, No. 172 (Hymen.
11, Apid. 5, Dipt. 8), p. 271.

Erythrea Centaurium, No. 298 (Lepid.

3), p. 407.

Erythrina crista-galli, p. 215.

herbacea, p. 215.
E. velutina, p. 215.

Erythroxylon, p- 149.

Eschscholtzia californica, p. 94.

Eupatoriacee, p. 318.

Eupatorium cannabinum, No. 214,
(Apid. 2, Dipt. 6, Lepid. 7), p. 318.

Euphorbia ‘Cyparissias, p- 520.

E. helioscopia, p. 519.

Euphorbiacee, p. 520.

Euphrasia minima, p. 447.

E. officinalis, No. 332 (Apid. 4, Dipt.
3), p. 447.

E. salisburgensis, p. 450.

Euonymus europea, No. 85 (Dipt. 12,
Hymen, 1), p. 162.

FARAMEA, p. 304.

Festuca pratensis, p. 568.

Ficus Carica, No. 377, p. 521,

Forsythia, p. 392.

Fragaria vesca, No. 138 (Dipt. 8, Coleopt.
7, Th. 1, Apid. 8, Hymen. 1), p
230.

Fritillaria imperialis, p. 556.

Fuchsia, p. 265.

Fumaria capreolata, p. 100.

F. officinalis, No, 26 (A*.), p. 99.

F. parviflora, p. 100.

F, spicata, p. 100.

Fumariace, p. 95,

GAGEA ARVENSIS, p. 556.

G. Liottardi, p. 556.

G. lutea, p. 556.

Galactia, p. 215.

Galanthus nivalis, No. 396 (A*.), p. 559.

Galeobdolon luteum, No. 360 (B. 5, [B.
1, Apid.1}), p. 496.

Galeopsis Ladanum, No. 358 (B. 3, Apid.

1), p. 493.
G. ochroleuca, No. 357 (B. 1), p. 492.

G. tetrahit, No. 356 (B. 3, CMpia. 1,

Syrph. 1]), p. 491.

G. versicolor, p. 493.

Galium boreale (Dipt. 1), p. 301.

G. eruciatum, p. 306.

G. Mollugo, No. 205 (Dipt. 8, Hymen.
1), p. 300.

G. palustre, p. 302.

G. silvestre, p. 301.

G. tricorne, p. 302.

G. uliginosum, p. 302.

G. verum, No. 206 (Dipt. 2, Coleopt. 4,
Hymen. 1), p. 301.

Gaudichaudia, p. 149.

Genista anglica, No. 109 (Apid. 3), p
192.

G. pilosa, No. 110 (A*.), p. 193.

G. tinctoria, No. 108 (Api 16, Boe snag
1, Dipt. 3, Lepid. 1, Coleopt. 3]), Pp
188.

Genistes, p. 187.

Gentiana acaulis, p. 403. 2

. Amarella, No. 297 (B. 1), p. 404.”

. asclepiadea, p. 403.

. bavarica, p. 404.

campestris, p. 405.

ciliata, p. 404.

. glacialis, p. 404.

. lutea, p. 402.

. nana, p. 405.

. nivalis, p. 404.

: obtusifolia, p- 405.

. Pneumonanthe, No. 296 (B. 9);

“403.

G. punctata, p. 403.

G. tenella, p. 404.

G. verna, p. 404.

Gentianex, p. 402.

Geraniacee, p. 149.

Geraniez, p. 149.

—. i No. 80 (Dipt. 5, Apid.
3);

G. pa alte No. 76 (Apid. 9, Dipt. 6,
Lepid. 1), p. 149.

G. pratense, No. 77 (Apid. 12, Dipt. 1),

. 150.

G. pusillum, No. 81 (Syrph. 1), p. 154.
G. pyrenaicum, No. 78 ( Apid. 10,
Hymen. 2, Dipt. 12, Coleopt. 3), p

151.

G. robertianum, No. 82 (Rhing. 1,
Coleopt. 1, Lepid. 1), p. 156.

G. sanguineum, No. 79 Capi. 2, Hymen.
2, Rhing. 1), p. 152.

AARARRARHALRL

INDEX OF PLANTS. 661

Gesneracer, p. 466.

Geum montanum, p. 229.

G. reptans, g 229. -

G. rivale, No. 136 (B. 11, [Apid. 2],
Rhing. 1, Coleopt. 1), p. 229.

G. urbanum, No. 137 (Syrph. 1, Coleopt.
1), p. 230.

Gilia micrantha, p. 408.

G. pulchella, p. 408.

Gladiolus communis, p. 548.

G. palustris, p. 548.

G. segetum, p. 548.

Glaucium luteum, p. 94.

Glechoma ; see Nepeta, p. 484.

Globularia cordifolia, p. 468,

G. nudicaulis, p. 468.

G. vulgaris, p. 468.

Globulariacex, p. 468.

Gloriosa superba, p. 557.

Glosgostigma elatinoides, p. 436.

Glycine, p. 214.

Gnaphalium luteo-album, No. 222 (Apid.
2, Hymen. 2, Dipt. 4), p. 324.

G. uliginosum (Apid, 1), p. 324.

Godetia, p. 265, |

Geethea coccinea, p. 146.

Goldfussia anisophylla, p. 467.

Gomeza, p. 528.

Gomphocarpus, p. 400.

pies bri herbaceum, p. 145.

Goodenia, p. 364.

Goodenoviex, p. 364.

Goodyera repens, p. 532.

Gramine, p. 568.

Gymnadenia conopsea, p. 534.

G. odoratissima, p. 534.

Gymnospermee, p. 526.

Gypsophila paniculata, No. 55 (Dept. 15,
Hymen. 5), p. 127.

G. repens, p. 128.

HABENARIA, p. 533.

Halorageze, p. 255.

Hedera, p. 287.

Hedychium, p. 542.

Hedyotis, p. 304.

Heeria, p. 255.

Helianthemum alpestre, p. 117.

H. guttatum, p. 117.

H. Kahiricum, p. 117.

H. ledifolium, p. 117.

H. Lippii, p. 117.

H. villosum, p. 117.

H. vulgare, No. 45 (Syrph. 6, Apid. 4,
Coleopt. 1), p. 117.

Helianthoidez, p. 325. _ et oe a

Helianthus multiflorus, No. 224 (Apid.
1, Syrph. 3), p. 325.

Helleborus, p. 81.

Hemerocallis fulva, p. 554.

Hepatica triloba, p. 71.

Heracleum Sphondylium, No. 194 (Dipt.
49, Coleopt. 21, Hymen. 34, Apid. 13,
Hemipt. 1), p. 284. a what]

Herminium Monorchis, p. 533.

Herniaria glabra, p. 509.

Hesperis matronalis, No. 34 (Dipt. 6,
Apid. 3, Lepid. 3, Coleopt. 1), p. 108.

H. tristis, p. 108.

Heterocarpea, p. 201.

Heterotoma, p. 365.

Heterotropa asaroides, p. 517.

Heuchera, p. 243.

Hieracium pilosella, No. 267 (Apid. 9,
Hymen. 1, Dipt. 2, Lepid. 3, Coleopt.
3), p. 355.

H. umbellatum, No. 266 (Apid. 10,
Hymen. 1, Dipt. 5, Lepid. 4), p. 354.

H. vulgatum, No. 268 (Apid. 8, Lepid.
1), p. 356, |

Himantoglossum hircinum, p. 534.

Hippocrepis comosa, No. 115, p. 199.

Hockinia, p. 422.

Homogyne alpina, p. 335.

Honkeneja peploides, p. 137.

Hordeum distichum, p. 568.

H. vulgare, p. 568.

Horminum pyrenaicum, p. 477.

Hottonia palustris, No. 289 (Hymen. 1,
Dipt. 6), p. 386.

Hoya, p. 401.

Hutchinsia alpina, p. 111.

Hyacinthus orientalis, No. 394 (Apid. 4,
Dipt. 1, Coleopt. 1), p. 554.

Hydrangee, p. 248.

Hydrocharidex, p. 526.

Hydrocharis, p. 527.

Hydrocotyle americana, p. 271.

H. vulgaris, p. 271.

Hyoscyamus niger, No. 316 (Apid. 2),
p. 427.

Hyoseris radiata, p. 351.

Hypecoum grandiflorum, p. 95.

H. procumbens, p. 95.

Hypericacer, p. 189. -

Hypericum hirsutum, p. 140.

H. humifusum, p. 141.

H. perforatum, No. 68 (Apid. 8, Hymen.
1, Dipt. 15, Lepid. 2, Coleopt. 1), p.
139.

H. quadrangulum, p. 141.

Hypocheris glabra, No. 269 (Apid. 5),

. 356.

ul radicata, No. 270 (Apid. 22, Dipt.
6), p. 356. .

ILLECEBRACE, p. 509.

Illecebrum verticillatum, p. 509,

Illicium religiosum, p. 89.

Impatiens, p. 160.

Indigofera macrostachya, p. 198.

I, speciosa, p. 198.

Inula, p. 361.

Inuloidex, p. 324.

Ioeroma tubulosum, p. 427.

Jonidium, p. 121.

Ipomea pestigridis, p. 425. -

Iridex, p. 548.

662

Iris Pseud-Acorus, No. 387 (B. 4, LApid.
2], Rhing. 1), p. 548.
Isotoma axillaris, p. 365.

JANUSIA, p 149.

Jasione montana, No. 288 (Apid. 47,
Hymen. 20, Dipt. 22, Lepid. 7, Coteopt.
3), p. 369,

Jasminum, p. 392.

Juglandacer, p. 523.

Juglans cinerea, p. 523.

J. regia, p. 523.

Juncacer, p. 561.

Juncus bufonius, p. 561.

J. filiformis, p. 561.

J. spherocarpus, p. 561.

Jurinea, p. 361.

KALMIA ANGUSTIFOLIA, p. 381,
K. latifolia, p. 380.

K. polifolia, p. 380.

Kernera saxatilis, p. 105.
Knautia ; see Scabiosa, p. 309.
Knoxia, p. 304.

LABIATA, p. 469.

Lactuca, p. 361.

Lagerstreemia, p. 260.

Lamium album, No. 359 (Apid. 11,
[Apid. 5], Rhing. 1), p. 493.

L. amplexicaule, p. 496.

L. Galeobdolon, No. 360 (B. 5, [B. 1,
Apid. 1), p. 496.

L. incisum, No. 363 (Apid. 5), p. 498.

L. maculatum, No. 361 (A4pid. 2, [ Apid.
2), Rhing.), p. 496.

L. purpureum, No, 362 (Apid. 9, Dipt.
1), p. 497.

Lantana, p. 469.

Lappa minor, No, 243 (Apid. 2), p. 338.

L. tomentosa, No. 244 (Apid. 5, Lepid.
1), p. 338.

Lapsana communis, No. 261 (Sy7ph. 3),
p. 351.

Larix, p. 526.

Lathyrus grandiflorus, p. 211.

L. montanus, No, 123 (Apid. 2, [Lepid.
1}), p. 210.

L. odoratus, No. 124, p. 211.

L. pratensis, No. 120 (Apid. 5), p. 207.

L. silvestris, No. 122 (Apid. 1, [Lepid.
5]), p. 210.

L.. tuberosus, No, 121 (Apid. 1, [Lepid.
2]), p. 210.

L. vernus, No. 125 (Apid. 1), p. 211.

Lavandula vera, No. 336 (Apid. 11), p.
469.

Lechea, p. 117.

Leguminose, p. 167.

Lemna gibba, p. 565,

I. minor, Pp 565.

L. polyrrhiza, p. 565.

1,. trisulea, p. 565.

Lemnaceer, p. 565.

THE FERTILISATION OF FLOWERS.

Lentibulariez, p. 465.

Leontodon autumnale, No. 271(Apid. 14,

_ Hymen. 1, Dipt. 11, Lepid. 2), p. 356.

L. hastile, No. 272\(Apid. 9, Hymen. 1,
Dipt. 8; Lepid. 1), p. 358.

L. hirtus, No. 273 (Apid. 15, Syrph. 8,
Lepid. 1), p. 358.

Leonurus Cardiaea, p. 495.

Lepidium sativum, No. 38 (Dipti. 10,
Hymen. 5, Apid. 6, Coleopt. 4, Lepid.
1), p. 110.

Leptosiphon micranthum, p. 408.

Leschenaultia formosa, p. 364.

Lesperdeza, p. 201.

Leucosmia, p. 519.

Liatris, p. 361.

Ligustrum vulgare, No. 292 (Apid. 1,
Syrph. 1), p. 3938.

Liliacee, p. 548.

Lilium bulbiferum, p. 555.

L. croceum, p. 556.

L. Martagon, p. 555.

Limnanthemum, p. 407.

Linaria alpina, p. 432.

L. Cymbalaria, p. 433.

L. minor, p. 432.

L. vulgaris, No. 320 (Apid. 8, [Hymen.
1]), p. 431.

Line, p. 147.

Linnea borealis, p. 293.

Linum catharticum, No. 74 (Dipé. 2),

; dads

ied usitatissimum, No. 75 (Apid. 2,
Lepid. 1), p. 148.

Listera ovata, No. 380 (Coleopt. 2,
Hymen. 7, [B. 1]), p. 295.

Lithospermum arvense, No. 309 (Lepid.
d. 2), p. 417.

L. canescens, p. 418.

L. longiflorum, p. 418.

Lloydia serotina, p. 555.

Loasex, p. 267.

Lobelia Erinus, p. 365.

L. fulgens, p. 365.

L. syphilitica, p. 365.

Lobeliex, p. 365. .

Loiseleuria procumbens, p. 300.

Lonicera alpigena, p. 298.

L. Caprifolium, No. 202 (Lepid. n.! 7,
[+ 3, Apid. 2, Dipt. 3]), p. 298.

L. ceerulea, p. 295.

L. Periclymenum (Lepid. n.! [B. 1)),

p- 295.
1. serotina, p. 555.
L. tatarica, No. 203, p. 297.

L. Xylosteum, No. 204 (Apid. 3, Dipt.
2), p. 297.

Lopezia coronata, p. 265.

L. miniata, p. 265.

L. racemosa, p. 265.

Lotex, p. 167.

Lotus corniculatus, No. 90 (Apid. 22,
[Dipt. 2, Lepid. 6]), p. 167.

Luculia, p. 304.

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———_—- ©

INDEX OF PLANTS.

Lupinus luteus, No. 107 (Apid. 3), p.
187.

Luzula campestris, p. 561.

L. lutea, p. 561.

L. nivea, p. 561.

L. pilosa, p. 561.

Lychnis alpina, p. 129.

L. flos-cuculi, No. 57 (Apid. 7, Lepid.
6, Syrph. 3), p. 129.

L. flos-Jovis, p. 129.

L, Githago, No, 59 (Lepid. d. 2, [Rhing.
1)), p. 131.

L. vespertina, No, 58 (Lepid. n.1), p. 131.

L. viscaria, p. 129.

Lycium barbarum, No. 315 (Apid. 3),
p- 426.

Lycopsis arvensis, No. 303 (Lepid. d. 1),
p. 411.

Lycopus europeus, No. 339 (Hymen. 1,
Dipt, 6, Hemipt. 1, Lepid. 1, Th. 1),
p. 471.

Lysimachia Nummuiaria, p. 390.

L. thyrsiflora, p. 390.

L. vulgaris, No. 290 (Apid. 3, Hymen.
1, Syrph. 1), p. 389.

Lythrariexw, p. 255.

Lythrum Greefferi, p. 260.

L. hyssopifolia, p. 260.

L. Salicaria, No. 165 (Apid. 9, Syrph. 7,
Lepid. 2, Coleopt. 2, Th. 1, Hemipt. 1),

2

p. 255.
L. thymifolia, p. 260.

MAGNOLIA ULAN, p. 89.

M. grandiflora, p. 90.

saan p- 89.

Malachium aquaticum, No. 63 (Dipt. 5,
Coleopt. 1, Th. 1, Apid. 3), p. 133.

Malpighiacez, p. 149.

Malva Alcea, No. 71 (Apid. 3), p. 144.

M. moschata, No. 72 (Apid. 3, Dipt. 1,
Lepid. 1), p. 144.

M. rotundifolia, No. 70 (Apid. 4), pp.
142, 144.

M. silvestris, No. 69 (Apid. 26, Hymen.
1, Dipt. 2, Lepid. 1, Coleopt. 1), p.
142.

Malvacee, p. 142.

Mandragora vernalis, p. 427.

Manettia, p. 304.

Maranta arundinacea, p. 543.

M. bicolor, p. 542.

M. cannefolia, p. 542.

Marantee, p. 542.

Marcgravia nepenthoides, p. 142.

Maregraviacee, p. 142.

Marrubium, p. 489.

Martha fragrans, p. 305.

Martiusia, p. 214.

Martynia, p. 466.

Matricaria Chamomilla, No. 233 (Apid.

. 2, Hymen. 1, Dipt. 11, Coleopt. 3), p.
332.
Maurandia, p. 434.

663

Medicago faleata, No. 94 (Apid. 11,
- Dipt. 2, [Lepid. 5]), p. 179.
M. lupulina, No. 95 (Apid. 4, Dipt. 2,
Lepid. 1), p. 180.
M. sativa, No. 93 (Lepid. d. 9%, [Apid.
2]), p. 175.
Melampodium, p. 361.
Melampyrum arvense, p. 461.
M. nemorosum, p. 461.
M. pratense, No. 335 (Apid. 3, [+ 3,
Dipt. 1]), p. 458.
M. silvaticum, p. 461.
Melastomacee, p. 255.
Melilotus officinalis, No. 96 (Apid. 5,
Hymen. 1, [+ 1]), p. 180.
M. vulgaris, No. 97 (4*.), p. 181.
Melittis melissophyllum, No. 351 (Ayid.
1), p. 486.
Melvilla, p. 261.
Mentha aquatica, No. 338 (Apid. 4,
Hymen. 1, Dipt. 18), p. 471.
M. arvensis, No. 337 (Dipt. 10, Lepid.
1), p. 470.
Menyanthes trifoliata, p. 407.
Mertensia, p. 422.
Methonica superba, p. 557.
Meum, p. 286.
Meyenia erecta, p. 467.
Mimosaceex, p. 220.
Mimulus, p. 436.
Mirabilis Jalapa, p. 508.
Mitchella, p. 304.
Mitella pentandra, p. 243.
Meehringia trinervia, No. 67 (Coleopt. 1),
. 136.
Weoards ciliata, p. 477.
M. didyma, No. 345 (Lepid. 1), p. 477.
Monochoria, p. 561.
Monocotyledons, p. 526. -
Morina elegans, p. 308.
Musa, p. 543.
Muscari botryoides, p. 554.
Musee, p. 543.
Mutisiacee, p. 351.
Myosotis alpestris, p. 415.
M. hispida, No. 308 (Apid. 1), p.416.
M. intermedia, No. 306 (Apid. 3, Dipt.
2), p. 415.
M. palustris, No. 307 (Lepid. 1, Dipt. 1),
. 416.
ue silvatica, No. 305 (Apid. 1, Dipt.
11), p. 414.
M. versicolor, p. 416.
Myosurus minimus, p. 73.
Myriophyllum spicatum, p. 255.
M. verticillatum, p. 255.
Myrrhis odorata, No. 182 (Dipl. 3,
Coleopt. 1, Hymen. 1, Apid. 1), p. 278.

NAIADACEA, p. 567.

Narcissus Tazetta, p. 560.

Nardus stricta, p. 568.

Nasturtium amphibia, No. 28 (Hymen. 1,
Dipt. 4), p. 102.

664

Nasturtium officinale, p. 101.

N. silvestre, No. 27 (Hymen. 2, Apid. 3,
Dipt. 5), p. 100.

Neea theifera, p. 508.

Neotinea, p. 527.

Neottia nidus-avis, No. 381, (Dipt. 1,
[+ 2]), p. 531.

Neottiex, p. 529.

Nepeta Glechoma, No. 349 (Apid. 21,
Dipt. 4, Lepid. 3), p. 484.

Nerium odorum, p- 396.

N. Oleander, p. 396,

Nertera, p. 304.

Neseea, p. 260.

Neurocarpum, p. 214.

Nigella arvensis, p. 81,

N. damascena, p. 81.

Nigritella angustifolia, p. 534.

N. suaveolens, p. 534.

Notylia, p. 528.

Nuphar aia No. 19 (Dipt. 1, Coleopt.
1), p. 93.

Hee p- 508.

Nympheea alba, p. 93.

Nympheacee, p. 93.

OcyMuM, p. 469.

Odontites lutea, No. 331, p. 447.

O. serotina, No. 330 (Apid. 3), p. 445. \

(Enanthe fistulosa, No, 187 (Dipti. 9,
Coleopt. 1, Apid. 3), p. 281.

(i. Phellandrium, No. 188. (Dipt. 7,
Coleopt. 3, Hymen. 7, Apid. 2, Lepid.
1), p. 281.

(Enothera biennis, No. 169 (Lepid. n. 1,
Apid. 6, Syrph. 3), p. 264.

(KE. sinuata, p. 264.

CE, tenella, p. 265.

Oleacez, p. 392,

Omphalodes verna (Apid. 2), p. 416.

Onagrariex, p. 261.

Oncidium, p- 528.

Onobrychis sativa, No. 116 (Apid. 22,
Syrph. 1, Lepid. 5), p. 200.

Ononis spinosa, No. 92 (Apid. 13), p. 174.

Onopordon Acanthium, No. 255 (Apia.
11, Hymen. 1, Lepid. 3, Coleopt. 1,
Hemipt. 2), p. 344.

Ophiorhiza, p. 304,

Ophryde, p. 533.

Ophrys muscifera, p. 534,

Orchider, p. 527.

Orchis globosa, p. 539.

O. latifolia, No. 384 (Apid. 12, Dipt.),
pp. 535, 539.

O. maculata, No. 385 (B. 1, Dipt. 4), pp.
535, 539.

0. mascula, No. 382 (B. 8), pp. 535, 539.

O. morio, No. 383 (Apid. 9), pp. 535,
539.

O. tridentata, p. 539,

Q. ustulata, p. 539.

Origanum vulgare, No. 342 (Apid. 5,
Dipt. 12, Lepid. 2), p. 475.

THE FERTILISATION OF FLOWERS. sa

Oryza clandestina, p. 568.

Oxalidex, p. 159.
Oxalis, p. 159.
Oxybaphus, p. 508.

PmONIA Movuray, p. 88.

Paliurus aculeatus, p. 163.

Palme, p. 562.

Pancratium maritimum, p. 560.

Papaver alpinum, p. 94,

P. Argemone, p. 94.

P. Argemonoides, p. 94.

Fi dubium, p-. 94.

i hybridum, p- 94.

P. Rheas, No. 20 (Apid. 7, Dipt. 1,
Coleopt. 1, Orthopt. 1), p. 93.

Papaveracee, p. 93.

Paradisia Liliastrum, p. 552.

Parietaria, p. 520.

Paris quadrifolia, p. 557.

Parnassia palustris, No. 157 (Muse. 15,
Hymen. 4, Coleopt. 2), p. 247.

Passiflora ccerula, p. 267.

P. racemosa, p. 268.

Passifloree, p. 267.

Pastinaca sativa, No.
Hymen. 7), p. 284.

Paullinia, p. 164.

Pavia rubicunda, p. 166.

Pavonia hastata, p. 146.

Pedicularis silvatica, No. 333 (B. 6, [+
1]), p. 450.

P. verticillata, p. 454.

Pelargoniez, p. 159.

Pelargonium, p. 158.

Pemphis, p. 261.

Pentstemon, p. 434.

Periploca, p, 402.

Petasites albus, p. 334.

Petroselinum sativum, No. 176 (Dipt. 8,
Apid. 1), p, 275.

Peucedanum Cervaria, No. 191 (Dipé. 4,
Coleopt. 2, Hymen. 15. Apid. 5), p
282.

P. graveolens, No, 192 (Dipt. 15, Hymen.
25, Apid, 6), p. 283.

hogs sativum, No. 193, p. 284.

Phaseolew, p. 214.

Phaseolus angulus, p. 215,

P. Caracalla, p. 215.

P. coecineus, p, 215.

P. multiflorus, p. 217.

P. vulgaris, p. 216,

Philadelphius coronarius (Apid. 9, Syrph.
3, Coleopt. 2), p. 248.

Phlox paniculata, No. 299 (Lepid. x.,

Dipt. 2), p. 407.

Physianthus, p. 400.

Physostegia, p. 489.

Phyteuma, p. 369.

Picris hieracioides, No. 262 (Apid. 16,
Hymen. 1, Dipt. 9, Lepid. 3), p. 352.

Pimpinella magna, No. 180 (Apid. 2), p
277.

193 (Dipt. 7,

INDEX OF PLANTS.

Pimpinella Saxifraga, No. 181 (Dipt. 8,.

Coleopt. 4, Hymen. 7, Apid. 8, Neuropt.
1), p. 277.

Pinguicula alpina, p. 466.

P. lusitanica, p. 466.

P, vulgaris, p. 466.

Pinus, p. 526.
Pisonia hirtella, x. 508.
Pisum sativum, No. 126 (Apid. 3), p. 211.

Plantaginee, p. 503.

Plantago alpina, p. 506.

P. lanceolata, No. 867 (Apid. 3, Syrph.
3), p. 503.

LP. media, No. 368 (Apid. 6, Dipt. 7,
Coleopt. 4), p. 506.

Platanthera bifolia, p. 533.

P. chlorantha, p. 533.

P. solstitialis, p. 533.

Plectranthus fruticosus, p. 469.

Plumbaginer, p. 382.

Plumbago, p. 382.

Poa annua, p. 568.

Poinsettia pulcherrima, p. 520.

Polanisia, p, 114.

Polemoniacez, p. 407.

Polemonium cceruleum, p. 407,

Polycarpex, p. 138.

Polycarpon tetraphyllum, p. 138.

Polygala alpestris, p. 123.

P. Chamebuxus, p. 123.

P. comosa, No. 50, p. 122.

P. myrtifolia, p. 133.

Uy: ey ia No. 51 (Apid. 3, Lepid. 1),

Poly gal ee, p. 122.

Polygonacex, p. 509.

en Gage aviculare, No. 374 (Syrph.
3), P

P; Bintorte, No. 370 (Apid. 2, Dipt. 5),
p- 511.

¥. fagopyrum, No. 369 (Apid. 12,
Hymen. 4, Dipt. 21, Lepid. 4), p. 509.

Ey Japathifolium, No. 372 (Syrph. 3), p

P. ieee No. 373 (Syrph. 4), p. 514.

P. Persicaria, No. 371 (Syrph. 7, Apid.
3, Lepid. 1), p. 512.

P. viviparum, p. 512.

Polystachya, p. 528.

Pome, p. 238.

Pontederia, p. 561.

Pontederiaceze, p. 561.

Posidonia, p. 567.

Posoqueria fragans, p. 305.

Potamogeton, p. 567.

Potentilla anserina, No. 141 (Hymen, 2,
Apid. 2), p. 233.

P, argentea, p. 234.

P. atro-sanguinea, p. 234.

P. aurea, p. 234.

P. caulescens, p. 234.

P. fruticosa, No. 142 (Apid. 2, Hymen.
. 2, Dipt. 15, Coleopt. 2), p. 233,

P. grandiflora, p. 234.

665°

Potentilla minima, p. 232. ‘

P. reptans, No. 140 (Apid. 10, Hymen,
1, Dipt. 1), p. 232.

P. salisburgensis, p- 234.

P. tormentilla, No. 143 (Apid. 2, Dipt.
4), p. 233.

P, verna, No. 139 (Apid. 15, Dipt. 9,
Coleopt. 1), p. 231.

Potentillex, p. 229.

Poteriex, P- 234.

ae anguisorba, No. 146 (Vesp. 1),

Peoantion, p- 361.

Primula Auricula, p. 383.

P, cortusoides, p. 384.

P. elatior, No. 288 (Apid. 9, Dipt. 2,

[ Coleopt. 1]), p. 384.

. fayinosa, pp. 383, 385, 386.

: rs pa p. 385.

- Involucrata, p. 384.

- longiflora, pp. 383, 385, 386.

. minima, pp. 383, 385.

. mollis, p. 383.

officinalis, p. 385.

. scotica, p. 383.

. sikkimensis, p. 384.

. sinensis, p. 383.

stricta, p. 383.

. verticillata, p. 383.

. Villosa, pp. 383, 385.

. viscosa, p. 385.

Primulacez, p. 383.

Pringlea antiscorbutica, p. 106.

Prostanthera, p. 499.

Proteacex, p. 519.

Prune, p. 221.

Prunella grandiflora, p. 490.

P. vulgaris, No. 355 (Apid. 8, Lepid. 3),
p. 489. ,

Prunus avium, Cerasus, domestica, No.
129 (Apid. 8, Syrph. 3, Lepid. 3), p. 222.

P. communis (P. spinosa), No. 127 (Apid.
15, Hymen. 1, Dipt. 10, Coleopt. 1),

921

¥ Dadegs No. 128 (Dipt. 2, Apid. 1,
Coleopt. 1), p. 211.

Pulicaria dysenterica, No. 223 (Apid. 6,
Syrph. 3, Lepid. 3, Coleopt. 1), p. 324.

Pulmonaria angustifolia (azurea), p. 411.

P. officinalis, No. 304 (Apid. 12, Syrph.
3, Lepid. 1, [Coleopt. 1]), p. 412,

Pulsatilla vernalis, p- 71.

P. vulgaris, p. 71.

Pyrola minor, p. 382.

P. rotundifolia, p. 382.

P. secunda, p. 382.

P. uniflora, p. 382.

Pyrolex, p. 382.

Pyrus Aucuparia, No. 152 (Apid. 11,
Hymen. 3, Dipt. 14, Coleopt. 18), p. 239.

P. communis, No. 151 (Dipt. 16, Apid.
7, Hymen. 3, Coleopt. 4, Th. 1), p. 239.

P. malus, No. 150 (Apia. 9, Siymen, 1,
Dipt. 6), p. 238.

Ny Oa Ee he ae

666

RADIOLA LINOIDES, p. 149.

Rafilesia, p. 517.

Ranunculaceex, p. 69.

Ranunculus acris, bulbosus, repens, No.
7 (Dipt. 23, Coleopt. 11, Hymen. 4,
Apid, 20, Lepid. 4), p. 76.

R. alpestris, p. 74.

R. aquatilis, No. 5 (Dipt. 6, Apid. 2,
Coleupt. 1), p. 74.

R. auricomus, No. 10 (Apid. 3, Hyimen.
1, Dipt. 4, Th. 1), p. 78.

R. bulbosus ; see R. acris,

R. ficaria, No. 9 (Dipt. 4, Coleopt. 1, Th.
1, Apid. 8), p. 78.

R. flammula, No. 6 (Dipt. 5, Apid. 2,
Lepid. 4), p. 74.

R. glacialis, p. 74.

R. lanuginosus, No. 8 (Dipt. 8, Colzopt.
2, Hymen. 1, Apid. 4), p. 78.

R. montanus, p. 76.

R. parnassifolius, p. 74.

R. pyreneus, p. 74.

R, repens ; see R. acris,

Raphanus Raphanistrum, No. 41 (Apid.
1), p. 113.

Reseda lutea, No. 44 (Hymen. 4), p. 116.

R. luteola, No. 43 (Apid. 4), p. 116.

R. odorata, No. 42 (Apid. 8, Hymen. 1,
Dipt. 1, Th. 1), p. 114.

Resedacee, p. 114.

Rhamnee, p. 163.

Rhamnus Frangula, No. 86 (Apid. 3,
Hymen. 1, Dipt. 1), p. 163.

Rheum Rhaponticum, p. 516.

Rhinacanthus, p. 468.

Rhinanthus Alectorolophus, p. 457.

R. crista-galli, No. 334 (B. 9, [Lepid. 1}),

p. 454. °

Rhododendron, p. 382.

Rhodoree, p. 380.

Rhus Cotinus, No. 88 (Dipt. 6, Coleopt,
1, Hymen. 6, Apid. 4), p. 166.

R. typhina, No. 89 (Apid. 2, Newropt.
1), p. 167.

Rhynchodia jasminoides, p. 396.

Rhynchospermum, p. 396.
Ribes alpinum, No. 158 (Apid. 6, Dipt.
3), p. 249.

R. aureum, p. 251.

R. grossularia, No. 161 (Apid. 9, Dipt.
4), p. 250.

R. nigrum, No. 159 (A*.), p. 250.

R. petreum, p. 251.

R. rubrum, No. 160 (Apid. 3, Hymen. 1),
p- 250,

R. sanguineum, p. 251.

Ribesiex, p. 249.

Rohdea japonica, p. 551.

Rosa canina, No. 148 (Apid. 6, Syrph. 2,
Coleopt. 12), p. 236.

R. Centifolia, No. 149 (Apid. 10, Hymen.
3, Syrph. 5, Coleopt. 16), p. 237.

R. rubiginosa, p. 238.

Rosacew, p. 221.

THE FERTILISATION OF FLOWERS.

Rosex, p. 236.

Rosmarinus, p. 477.

Rotala, p. 261.

Rubee, p. 227.

Rubiacee, p. 301.

Rubus fruticosus, No. 185 (Apid. 31,
Hymen. 5, Dipt. 12, Coleopt. 15, Lepid.
4), p. 227.

R. ideus, No. 134 (Apid. 11, Hymen. 2,
Syrph. 2, Coleopt. 2), p. 226.

R. saxatilis, p. 228.

Ruellia, p. 467.

Rumex crispus, p. 516.

R. obtusifolius, p. 516.

Ruta graveolens, No. 84 (Dipt. 19, Hymen.
11, Apid. 3), p. 160. |

Rutacez, p. 160.

SABAL ADAMSONI, p. 562.

Sagina nodosa, p. 137.

Salicinez, p. 524.

Salix cinerea, Caprea, etc., No. 378 (Apid.
46, Hepid. 8, Dipt. 26, Lepid. 3,
Coleopt. 2, Hemipt. 1), p. 524.

S. herbacea, p. 526.

S. repens, No. 379 (Apid. 6, Hymen. 1,
Dipt. 2, Lepid. 1), p. 526.

Salvia ethiopica, p. 479.

. argentea, p. 479.

austriaca, p. 483.

cleistogama, p. 483.

glutinosa, p. 481.

Grahami, p. 480.

hirsuta, p. 480.

. lanceolata, p. 480.

. nilotica, p. 482.

- nutans, p. 479.

. Officinalis, No. 347 (Apid. 6, [+2,

Lepid. 1]), p. 480.

. patens, p. 482.

pendula, p. 479.

porphyrantha, pp. 479, 481.

pratensis, No. 346 (Apid. 4, [+5,

Lepid. 2)), pp. 477, 479.

rubra, p. 479.

Sclarea, p. 479.

. Silvestris, No. 348 (Apid. 1, Hymen.

1), p. 483.

. Splendens, pp. 480, 483.

. triangularis, pp. 479, 483.

. tubiflora, p. 483.

. verticillata, p. 482.

. virgata, p. 479.

Sambucus Kbulus, p. 290.

8. nigra, No. 199 (Dipt. 6, Coleopt. 2),
p. 290.

Sanguisorba officinalis, No. 147 (Syrph.
2), p. 236.

Sanicula europea, p. 274.

Santalacez, p. 520.

Sapindacee, p. 164.

Saponaria ocymoides, p. 128.

S. officinalis, No, 56 (Lepid. n. 1, [Dipt.
1}), p. 128.

RANANR NNRN NANN BMNNMNNMNMDM

INDEX OF PLANTS.

Saponaria vaccaria, p. 128.

Sarothamnus scoparius, No. 111 (4pid.
6, Syrph. 1, Coleopt. 2), p. 195.

Satureia hortensis, p- 476.

Saussurea, p. 361.

Saxifraga aizoides, p. 245.

S. crassifolia, p. 243.

8. oppositifulia, p. 245.

S. sarmentosa, p. 243.

Saxifragacese, p. 243.

Saxifragex, p. 243.

Scabiosa arvensis, No. 211 (Apid. 34,
Hymen. 4, Dipt. 15, Lepid. 11, Coleopt.
12), p 309.

2 Sesbroiaitk: he
S. Columbaria, No. 213 (Apid. 2, Dipt.
4), p. 315.

S. lucida, p. 315.

S. succisa, No. 212 (Apid. 14, Dipt. 11,
Lepid. 5, Coleopt. 1), p. 313.

Scevola, p. 364.

Schizanthus, p. 428.

Schomburgkia, p. 527.

Scilla maritima, p. 554.

Scirpus palustris, p. 567.

Scitaminex, p. 542.

Scleranthus perennis, p. 509,

Scopolina, p. 427.

Scrophularia aquatica, p. 436.

S. nodosa, No. 322 (Vesp. 5, Apid. 4), p.
434.

Scrophularinez, p. 429

Scutellaria galericulata, No. 350 (Lepid.

1), p. 486.

Secale cereale, p. 568.

Sedum acre, No. 162 (dpid. 11, Hymen.

- 2, Dipt. 2), p. 251.

8. album, p- 253.

8. atratum, p. 254.

S. reflexum, No. 163 (Apid. 1, Syrph. 1),

. 258.

S. repens, p. 254

8. Telephium, No. 164 (Apid. 5, Fyhen.

» 1, Dept. 1), p. 253.

Selaginew, p. 468.

Sempervivum, p- 254.

Senecio Jacobea, No. 238 (Apid. 16,
Hymen. 1, Dipt. 18, Lepid. 3, Coleopt.
1, Hemipt. 1), p. 335.

S. vulgaris, No. 239, p. 336.

Senecionidez, p, 333.

Serapias, p. 533.

Serjania, p. 164.

Serratula tinctoria, No. 256 (Apid. 1,
Lepid. 1), p. 345.

Sherardia arvensis, p- 804.

Sibbaldia alegeaciare p. 234.

Sideritis romana, p. 488.

Silaus pratensis, No.
Apid. 1), p. 282.

Silene acaulis, p. 129.

S. inflata, p. 129.

S. nutans, p. 129.

S. rupestris, p. 129.

189 (Hymen. 2,

667

Silene, p. 125.

Silphium, p. 361.

Silybum, p. 361,

Sinapis arvensis, No. 40 (Syrph. 3,
Hymen. 1, Apid. 3, Coleopt. 1, Lepid.
1), p. 112.

Siphocampylus bicolor, p. 365.

Sisymbrium Alliaria, No. 35 (Apid. 1,
Dipt. 3, Coleopt. 3), p. 109.

S. officinale No. 36 (Apid. 1, Lepid. 2),

P:

ne “TetteDas No. 178 (Dipt. 20,
Pia 3, Hymen. 8, Hemipt. 1), p

Solanacer, p. 425.

Solanum Dulcamara, No. 313 (Syrph. 1),
p. 426.

S. — No. 314 (Syrph. 2, Apid. 2),

8. tain * 812 (Syrph. 2), p. 425.

Soldanella, p. 389.

Solidago canadensis, No. 216 (Dipt. 5), p.
321.

S. virga-aurea, No. 215 (Apid. 5, Syrph.
2, Lepid. 1), p. 320.

Sonchus arvensis, No. 276 (Apid. 11,
Dipt. 4, Lepid. 1, Coleopt. 2), p. 361.
S. oleraceus, No. 275 (Syrph. 3, Lepid. 1),

p. 361.

Specularia perfoliata, p. 369.

Spirea Aruncus, No. 132 (Apid. 1,
Hymen. 2, Dipt. 2, Coteopt. * p. 224.

Ss. Filipendula, No. 131 (Apid. 2, Syrph.
4, Uoleopt. 1), p. 223.

8. salicifolia, sorbifolia, ulmifolia, No.
133 (Dipt. 42, Hymen. 14, Apid. 17,
Coleopt. 21, Newropt. 2, Lepid. 2), p
224.

S. ulmaria, No. 130 (Apid. 3, Hymen. 3,
Syrph. 9, Coleopt. 7), p. 222.

Spire, p. 929,

Spiranthes autumnalis, p. 529.

Stachys Betonica, No. 354 (Apid. 1,
Dipt. 2, Lepid. 1), p. 487.

8. germanica, p. 487.

8. palustris, No. 353 (B. 3, Syrph. 2,
Lepid. 3), p. 487.

S. silvatica, No. 352 (Apid. 6, my" 1,
[+ 1]), p. 486.

Stapelia, p. 401.

Statice, p. 382.

Stellaria cerastoides, p. 136. '

S. graminea, No. 64 (Syrph. 1), p. 188.

8. aa No. 65 (Dipt. 7, Ayia, 6,
Hymen. 1, Coleopt. 2, Lepid. 1, Th. 1),
. 135.

A tacit: No. 66 (Apid. 6, Dipt. 4, Th.
1), p. 135.

Stephanotis, p. 401.

Sterculiaceee, p. 146.

Stigmatostalix, p. 528.

Strelitzia regine, p. 5438.

Strobilanthes, p. 467.

Stylidier, p. 364.

668

Stylochiton hypogzeus, p. 564.

8S. lancifolius, p. 564.

Stylosanthes, p. 201.

Subularia aquatica, p. 113.

Syagrus, p. 562.

Sycomorus antiquorum, p. 522.

Symphoricarpus racemosus, No. 201
(Vesp. 6!, Apid. 7, Hymen.1), p. 292.

Symphytum officinale, No. 300 (Apid.
5, [+ 5], Rhing. 1, [Coleopt. 1]), p.
408.

Symplocarpus feetidus, p. 565.

Syringa persica, p. 393.

S. vulgaris, No. 291 (Apid. 8, Hymen. 1,
Dipt. 1, Lepid. 9), p. 392.

TABERNEZEMONTANA ECHINATA, p. 396,

Tacca cristata, p. 560.

Taccacez, p. 560.

Tanacetum vulgare, No. 234 (Apid. 7,
Hymen. 4, Dipt. 7, Lepid. 5, Coleopt.
2, Hemipt. 1, Newropt. 1), p. 332.

Taraxacum officinale, No. 274 (Apid. 58,

_ Hymen. 2, Dipt. 21, Lepid. 7, Coleopt.
4, Hemipt. 1), p. 359.

Tecoma capensis, p. 466.

Teesdalia nudicaulis, No. 33 (Hymen. 1,
Coleopt. 6, Dipt. 3), p. 106.

Telekia, p. 361.

Teucrium Botrys, p. 501.

T. Chameedrys, p. 501.

T. Scorodonia, No. 365 (Apid. 5, Syrph.
I), p. 499.

Thalictrum aquilegifolium, No, 2 (Apid.
3, Syrph. 5, Coleopt. 1), p. 70.

T. flavum, No. 3 (Syrph. 5, Muse. 1,
AX), p10.

T. minus, p. 71.

Thesium, p. 520.

Thlaspi arvense, p. 105.

Thrincia hirta, No. 273 (Apid. 15, Syrph.
3, Lepid. 1), p. 358.

Thunbergia alata, p. 467.

Thymeleaceze, p. 519.

Thymus Serpyllum, No. 340 (Apid. 7,
Hymen. 8, Dipt. 14, Lepid. 6), p. 472.

T. vulgaris, No. 341 (Apid. 2, Hymen.
1, Dipt. 3, Lepid. 1), p. 475.

Tilia europea, No. 73 (Apid. 3, Hymen.
1, Dipt. 9), p. 146. :

Tiliacee, p. 146.

Tofieldia calyculata, p. 557.

Torilis Anthriscus, No. 195 (Dipt. 1,
Hymen. 6, Apid. 1, Lepid. 1), p. 286.

Tozzia alpina, p. 458.

Trachelium, p. 369.

Tradescantia erecta, p. 561.

Trianospermum, p. 270.

Trientalis europeum, p. 392.

Trifolium alpestre, p. 186.

ii pe asig” 186.

T. arvense, No. 101 (Apid. 11, Hymen.
1, [Zepid. 1]), p. 186.

T. badium, p. 186.

THE FERTILISATION OF FLOWERS.

eeceny filiforme, No. 103 (Apid. 3)»

p- 187.

T. fragiferum, No. 99 (Apid. 1), p. 183.

T. medium, No. 104 (Aid. 2), p. 187.

ip ——— No. 106 (Apid. 1), p.
187.

T. nivale, p. 186.

T. pallescens, p. 186.

T. polymorphum, p. 186.

T. pratense, No. 100 (Apid. 24, [+ 4,
Lipt. 3, Lepid. 8]), p. 184.

Ss No. 105 (Apid. 2), p.

87.

T. repens, No. 98 (Apid. 6, [Dipt. 3,
Lepid. 2}), p. 181.

T. rubens, No. 102 (Apid. 2), p. 187.

Triglochin palustre, p. 567.

Triticum vulgare, p. 568.

Tritoma Uvaria, p. 561.

Trollius europeus, p. 80.

Tropeolum, p. 159.

Tussilago farfara, No. 236 (Apid. 5, Dipt.
2, Coleopt. 1), p. 333.

Typhonium cuspidatum, p. 564.

ULEX EUROPAUS, p. 198,
Umbelliferee, p. 270.
Urtica, p. 521.
Urticacee, p. 520.
Urticez, p. 520.
Utricularia, p. 465.

VACCINIACEA, p. 373.

Vaccinium Myrtillus, No. 284 (Amid. 5,
[+ 1]), p. 373.

V. Oxycoccos, p. 375.

V. uliginosum, No. 285 (Apid. 23,
Hymen. 1, Syrph. 4, Lepid, 2), p. 373.

V. vitis-idea, p. 375.

Valeriana cordifolia, p. 308.

V. dioica, No. 209 (Apid. 2, Dipt. 3,
Lepid. 1, Coleopt. 1), p. 307.

V. montana, p. 307.

V. officinalis, No. 208 (Apid. 8, Dipt.
19), p. 306.

V. Tripteris, p. 308.

Valerianez, p. 306.

Valerianella olitoria, p. 308.

Vallisneria spiralis, p. 526.

Vandee, p. 528.

Vandellia, p. 437.

Velleja, p. 364.

Veratrum album, p. 557.

Verbascum Lychnitis, (Apid. 1), pp. 480,
431.

V. nigrum, No. 317 (Apid. 5, Dipt. 4,
Lepid. 1, Coleopt. 1, Th. 1, Newropt.
1), p. 429.

V. pheniceum, No. 318 (Apid. 5, Syrph.
1), p. 430.

V. Thapsus, No. 319 (Apid. 6, Hymen.
1, Syrph. 3), p. 430.

Verbena officinalis, p. 469,

Verbenacer, p. 469.

INDEX OF PLANTS.

Vernonia, p. 361.

Veronica agrestis, p. 443.

V. alpina, p. 444.

V. arvensis, p. 444.

¥. - oe aa No. 325 (Dipt. 4, Apid.
we

) Risivides, R 444,

v. Chamedrys, No. pees (Syrph. 3, Apid.
4, Coleopt. 1), fe ha

¥. ‘hedervefolia, o. 328 (Apid. 4), p
442,

V. montana, p. 439.

ys ogame No. 326 (Dipt. 3, Apid. 3),

44

Wo ipxatille, p:

V. serpyllifoli a No. 329 (Dipt. 1), p
443.

¥. aang No. 327 (Apid. 2, Hymen.
3), D-

bx d Biyllos p. 444.

V. urticifolia, p. 439.

Viburnum Opulus, No. 200 (Dipt. 7,
Apid. 1, Coleopt. 2), p. 291.

Vicia amphicarpa, p. 20

V. angustifolia, p. 203.

V. Cracca, No. liz (Apid. 13, [Hymen.
1, Dipt. 1, Lepid. 1}), Pp. 202.

Vs Faba, No. 119 (Apid. 8, [+ 2, Coleopt.
1}), p. 206.

V. hirsuta, p. 201.

Vv ae o. 118 (B. 5, [+ 1, Apid.

Viciez, Dp. 201.

Victoria regia, p. 93.

Villarsia, p. 407.

Vinca major, No. 294 (B. 1), p. 396.

“V. minor, No. 293 (Apid. 7, Dipt. 2,
Th. 1), p. 394.

V. rosea, p. 395.

669

Vincetoxicum, p. 401.

Viola arenaria, p. 119.

V. arvensis, p. 118.

V. bicolor, p. 121.

¥, biflora, p. 119.

V. calcarata, p. 119.

VY. canina, No. 49 (Apid. 3, Dipt. 1,

Lepid. 2), p. 121.

. cornuta, p. 119.

. cucullata, p. 121.

. elatior, p. 121.

. floribunda, p. 121.

. mirabilis, p. 121.

. montana, p. 121.
odorata, No. 47 (Apid. 6, Dipt. 1,

Lepid, 2), p. 119.

V. pinnata, p. 121.

V. pumila, p. 121.

V. sagittata, p. 121.

V. silvatica, No. 48 (Apid. 1, Dipt. 1,
Lepid. 5), p. 119.

V. stagnina, p. 121.

V. tricolor, No. 46 (B. 1, Apia, t;
Syrph. 1]), p. 117.

Violariex, p. 117.

Voandzeia, p. 215.

Adddsaa

WEIGELIA ROSEA, p. 299.
Wulfenia carinthiaca, p. 445.

XERANTHEMUM, p. 361.
Yuooa, p. 561.

ZINGIBER OFFICINARUM, p. 542.
Zingiberex, p. 542.

Zinnia, p. 325.
Zostera, p. 567.

THE END.

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