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THE COLOURS OF FLOWERS.

NATURE SERIES.

x f

THE

i,, 'O •

COLOURS OF FLOWERS

AS

(J

ILLUSTRATED IN THE BRITISH FLORA

BY

GRANT ALLEN

WITH ILLUSTRATIONS

Jtonfroit

MACMILLAN AND CO.
1882

The Right of Translation and Reproduction is Reserved.

Ijfonbon :
R. CLAY, SONS, AND TAYLOR,

BREAD STREET HILL, B.C.

PREFACE.

THE first germ of the theory contained in this
little volume was originally set forth as an article
in the Cornhill Magazine, and I have to thank the
courtesy of the Editor and Publishers of that
periodical for their kind permission to expand it
into its present far fuller form.

I have been encouraged thus to give it shape in
a more permanent dress by the friendly appre-
ciation of the late Mr. Darwin, who wrote to me
as follows with regard to the central idea of my
original paper — the derivation of petals from flat-
tened and abortive stamens : — " Many years ago
I thought it highly probable that petals were in
all cases transformed stamens. I forget (except-
ing the water-lily) what made me think so ; but
I am sure that your evolutionary argument never
occurred to me, as it is too striking and too appa-
rently valid ever to be forgotten." It appeared to
me that if the idea so commended itself to Mr.
Darwin, it might also commend itself to other

vi PREFACE.

evolutionary biologists ; and I have ventured ac-
cordingly to work it out here to its furthest
legitimate conclusions.

My acknowledgments are due in the highest
degree to Sir John Lubbock's admirable little work
on British Wild Flowers in Relation to Insects,
and to Mr. Bentham's British Flora. I also owe
much to Sir Joseph Hooker's Student's Flora,
to Professor Sachs's Botany, and to other books
too numerous to mention. Personally, I have to
thank my friend Mr. F, T. Richards, Tutor of
Trinity College, Oxford, for many valuable sug-
gestions and corrections of which I have gladly
availed myself.

G. A.

CONTENTS.

CHAPTER I.

THE ORIGIN OF PETALS .

CHAPTER II.

GENERAL LAW OF PROGRESSIVE COLOURATION 17

CHAPTER III.

VARIEGATION 6l

CHAPTER IV.

RELAPSE AND RETROGRESSION 71

CHAPTER V.

DEGENERATION 91

CHAPTER VI.

MISCELLANEOUS . IIO

THE COLOURS OF FLOWERS.

CHAPTER I.

THE ORIGIN OF PETALS.

EVERYBODY knows that flowers are rendered beautiful
to us by their shapes, by their perfumes, and above
all by their brilliant and varied colours. All people
who have paid any attention to botany further know
that not every flower is thus bright and conspicuous ;
as a general rule, only those blossoms which depend
for their fertilisation upon the visits of insects are
provided with special attractions of honey, scent, and
vivid hues. An immense number of flowering plants,
perhaps even the majority among them, produce
only small and unnoticeable inflorescences, like those
of grasses, Oaks, conifers, and many other field weeds
or forest trees. The flowers that most people observe
and recognise as such, are the few highly developed
forms which possess large expanded coloured surfaces
to allure the eyes of their insect fertilisers. It is with
flowers in this more popular and ordinary sense that
we shall have to deal mainly in the present little
$ B

THE COLOURS OF FLOWERS.

treatise ; and our object must be to determine, not
why they are all as a group brightly coloured, but
why this, that, or the other particular blossom should
possess this, that, or the other particular hue. Why
is the buttercup yellow, while the stitchwort is white,
the dog-rose pink, and the harebell blue ? Why is
the purple foxglove dappled inside with lurid red spots ?
Why are the central florets of the daisy yellow, while
the ray-florets are pinky-white ? Why does sky-blue
prevail amongst all the veronicas, while yellow pre-
dominates in the St. John's worts, and white in the
umbellates ? These are the sort of questions which we
must endeavour briefly to answer, by the light of
modern evolutionary biology, from the point of view
of the function which each colour specially subserves
in the economy of the particular plant which
displays it.

The brilliant pigments of flowers usually reside in
the specialised organs known as petals, though they
are sometimes also found in the sepals and bracts, or
more rarely in the stamens and even in the pistil.
For the sake of those readers who happen to be
imperfectly acquainted with the subject at large (and
also to bring the botanical reader definitely into the
required point of view), it may be well to begin with
a very brief description of the organs which go to
make up a typical flower, together with a short
account of the part played by colour in general in
the fertilising function.

The essential elements in the flower are not at all
the showy and brilliant leaves which we usually
associate most with the name, but a set of compara-
tively small and unnoticeable organs occupying the

THE ORIGIN OF PETALS.

centre of most ordinary blossoms. The simplest
type of flower consists of two such organs only, a
pistil or ovary containing an embryo seed, and a
stamen which produces the pollen necessary to im-
pregnate it. The production of seed is in fact the
sole function of the flower ; every additional part is
only useful in so far as it conduces to this practical
end. In the most simple (though not the most
primitive) blossoms, fertilisation is effected by a grain
of pollen from a stamen falling upon the stigma or
sensitive surface of the pistil, and thence sending
forth a pollen-tube, which penetrates the ovule or
embryo seed, and so impregnates it.

As a rule, however, it is not desirable that a flower
should be fertilised by pollen from its own stamens.
Mr. Darwin has shown in many cases that when a
pistil is fecundated by pollen from a neighbouring
blossom, or still better from a different plant, it sets
more and sounder seeds, or produces heartier and
stronger young seedlings. To attain the benefits of
such cross-fertilisation, many plants have acquired
special peculiarities of structure : or, to put it more
correctly, those plants which have spontaneously
varied in certain favourable directions have been
oftenest cross-fertilised, and have thus on the average
produced more and stouter offspring. The advantage
thus gained in the struggle for existence has enabled
them to live down their less adapted compeers, and
to hand on their own useful peculiarities to a large
number of descendants. There are two ways in
which plants have ensured such a benefit ; the one is
by adapting themselves to fertilisation by means of
the wind, the other is by adapting themselves to

B 2

THE COLOURS OF FLOWERS.

fertilisation by means of insects. The first class are
said to possess anemophilous, the second class
entomophilous, flowers.1 It is with the latter alone
that we have here mainly to deal.

Entomophilous or insect-fertilised flowers are those
in which the pollen is habitually carried from the
stamens of one blossom to the pistil of the next on
the head or legs of butterflies, bees, beetles, or other
flying arthropods. In order to allure these insects,
and to induce them to visit one flower after another
of the same kind, the plants have often developed
small quantities of honey in the neighbourhood of
the essential organs, as well as specially coloured
floral leaves known as petals. Accordingly, a fully
evolved entomophilous blossom usually consists of
the four following whorls, or sets of parts, beginning
from within outward. First, in the very centre, the
pistil, or carpellary whorl, consisting of one or more
carpels or ovaries, each containing one or more embryo
seeds. Secondly, outside the pistil, the staminal
whorl, consisting of one or more pollen-bearing
stamens, usually three or six in the great class of
Monocotyledons, and five or ten in the great class
of Dicotyledons. Thirdly, outside the stamens, the
corolla or petaline whorl, consisting of several separate
or united petals, usually three in the Monocotyledons
and five in the Dicotyledons. Fourthly, outside the
corolla, the calyx or sepaline whorl, consisting of
several separate or united sepals, usually the same in
number as the petals. The position and arrangement

1 For further particulars see Sir John Lubbock's work on British
Wild Flowers in Relation to Insects, in the Nature Series.

THE ORIGIN OF PETALS.

of these parts is shown in the accompanying diagrams
(Figs, i and 2).

As regards function, the pistil produces the seeds
and grows later into the fruit. The stamens produce
pollen, to impregnate the pistil. The petals attract
the fertilising insects by their bright colour, and
advertise the honey, if any. The calyx covers up
the flower in the bud, and often serves to protect it

FIG. i. — Diagram of typical primitive monocotyledonous flower. «, carpels; />,
inner whorl of stamens ; c. outer whorl of stamens; d, petals; e, sepals. Each
whorl consists of three members.

from the attacks of useless creeping or honey-eating
insects.

One more preliminary explanation is necessary
before we enter upon the consideration of our main
subject. Flowering plants, at a very early date in
their history, split up into two great divisions. One
of these, the GYMNOSPERMS, to which all the oldest
fossil plants belong, as well as our own modern
conifers and cycads, possessed and still possess
flowers and fruits of a very simple character. Each

6 THE COLOURS OF FLOWERS.

blossom consists as a rule of a single stamen or a
single naked ovule, growing on a scale or an altered
leaf: and they display some remarkable analogies
with ferns, club-mosses, and other flowerless plants.
Of course, they never have petals or coloured organs.
The existing Gymnosperms may be regarded as
living survivors of a great class, once dominant, but
now nearly extinct; and their flowers probably still
preserve for us the original type of all blossoms, very

FIG. 2. — Diagram of typical primitive dicotyledonous fl >wer. a, carpels; b,
stamens ; c, petals ; d, sepals. Each whorl consists of five members.

slightly altered by time and circumstances. This is
especially the case with the cycads, small tropical
trees of palm-like appearance, whose inflorescence is
the very simplest of all known flowering plants. The
other great division, that of the ANGIOSPERMS, has
always more fully developed blossoms, often entomo-
philous, and possessed of brilliant colours. It split up
again at an early period of its development into two
secondary large classes, those of the Monocotyledons

THE ORIGIN OF PETALS.

and the Dicotyledons. These important classes are
distinguished from one another by several special
points of structure ; but the most striking one, so far
as regards our present subject, consists in the fact
that the Monocotyledons are generally arranged in
whorls of threes, while the Dicotyledons are generally
arranged in whorls of fives. At the present day,
the two modes of arrangement are often obscured in
various ways ; for example, among some Monocotyle-
dons the stamens are doubled, or consist of two
separate whorls, while the petals and sepals are
coloured alike and are otherwise almost indistinguish-s
able, so that the flowers seem at first sight to be
arranged by sixes rather than by threes ; and again,
among some Dicotyledons, one or more petals are
suppressed, or added, or all the petals are united into
a single circular or tubular corolla, so that the arrange-
ment seems at first sight to be by fours, or by eights,
or by threes rather than by fives. Originally, how-
ever, all Monocotyledons had a trinary arrangement,
while all Dicotyledons had a quinary arrangement ;
and these fundamental plans can still distinctly be
traced in by far the larger number of existing
species.

So much by way of introduction. Now, since the
bright pigments of flowers usually reside in the petals,
and since petals have for their main if not for their
only function the display of such pigments as an
attraction for the fertilising insects, it is clear that we
must begin our inquiry by asking, — What was the
original colour of the organs from which petals were
developed ? For we may take it for granted that the
primordial petals would at first follow the hue of the

THE COLOURS OF FLOWERS.

part out of which they were originally evolved. For
example, if we ought to regard them as altered and
modified leaves, then we may fairly conclude that the
earliest petals were green ; while, if we ought to
regard them as altered and modified stamens, then
we may fairly conclude that they were yellow.
Which of these two alternatives is the most likely
to be true ? Apparently, the latter.

Petals are in all probability originally enlarged and
flattened stamens, which have been set apart for the
special work of attracting insects. It seems likely
that all flowers at first consisted of the central organs
alone — that is to say, of a pistil, which contains the
ovary with its embryo seeds ; and of a few stamens,
which produce the pollen, whose co-operation is
necessary in order to fertilise these same embryo
ovules and to make the pistil mature into the ripe fruit.
But in those plants which took to fertilisation by
means of insects — or, one ought rather to say, in
those plants which insects took to visiting for the
sake of their honey or pollen, and so unconsciously
fertilising — the flowers soon began to produce an
outer row of barren and specialised stamens, adapted
by their size and colour for attracting the fertilising
insects ; and these barren and specialised stamens
are what we commonly call petals. Any flowers
which thus presented brilliant masses of colour to
allure the eyes of the beetles, the bees, and the
butterflies, would naturally receive the greatest
number of visits from their insect friends, and would
therefore stand the best chance of setting their seeds,
as well as of producing healthy and vigorous offspring
as the result of a proper cross. In this way, as we

THE ORIGIN OF PETALS.

have seen, they would gain an advantage in the
struggle for life over their less fortunate compeers,
and would hand down their own peculiarities to their
descendants after them.

But as the stamens of almost all flowers, certainly
of all the oldest and simplest flowers, are yellow, it
would seem naturally to follow that the earliest petals
would be yellow too. When the stamens of the
outer row were flattened and broadened into petals,
there would be no particular reason why they should
change their colour ; and, in the absence of any good
reason, they doubtless retained it as before. Indeed,
we shall see, a little later on, that the earliest and
simplest types of existing flowers are almost always
yellow, seldom white, and never blue; and this in
itself would be a sufficient ground for believing that
yellow was the original colour of all petals. But as
it is somewhat heretical to believe, contrary to the
general run of existing scientific opinion, that petals
are derived from flattened stamens, instead of from
simplified and attenuated leaves, it may be well to
detail here the reasons for this belief, because it
seems of capital importance in connection with our
present subject ; for if the petals were originally a
row of altered stamens set apart for the special
function of attracting insects, it would be natural
and obvious why they should begin by being yellow ;
but if they were originally a set of leaves, which
became thinner and more brightly coloured for the
same purpose, it would be difficult to see why they
should first have assumed any one colour rather than
another.

The accepted doctrine as to the nature of petals is

io THE COLOURS OF FLOWERS.

that discovered by Wolf and subsequently redis-
covered by Goethe, after whose name it is usually
called ; for of course, as in all such cases, the greater
man's fame has swallowed up the fame of the lesser.
Goethe held that all the parts of the flower were
really modified leaves, and that a gradual transition
could be traced between them, from the ordinary
leaf, through the stem-leaf and the bract, to the
sepal, the petal, the stamen, and the ovary or carpel.
Now, if we look at most modern flowers, such a
transition can undoubtedly be observed ; and some-
times it is very delicately graduated, so that you can
hardly say where each sort of leaf merges into the
next. But, unfortunately for the truth of the theory
as ordinarily understood, we now know that in the
earliest flowers there were no petals or sepals, but
that primitive flowering plants had simply leaves on
the one hand, and stamens and ovules on the other.
The oldest types of flowers at present surviving are
certain Gymnosperms, such as the cycads, of which
the well -known Zamias of our conservatories may be
regarded as good examples. These have only naked
ovules on the one hand and clusters of stamens in a
sort of cone on the other. The Gymnosperms are
geologically earlier than any other flowering plants.
But, if petals and sepals are later in origin (as we
know them to be) than stamens and carpels, we can
hardly say that they mark the transition from one
form to the other, any more than we can say that
Gothic architecture marks the transition from the
Egyptian style to the classical Greek. It is not
denied, indeed, that the stamen and the ovary are
themselves by origin modified leaves — that part of

THE ORIGIN OF PETALS, n

the Wolfian theory is absolutely irrefutable — but with
the light shed upon the subject by the modern
doctrine of evolution, we can no longer regard petals
and sepals as intermediate stages between the two.
The earliest flowering plants had true leaves on the
one hand, and specialised pollen-bearing or ovule-
bearing leaves on the other hand, which latter are
what in their developed forms we call stamens and
carpels ; but they certainly had no petals at all, and
the petals of modern flowers have been produced at
some later period. It is probable, too, that they have
been produced by a modification of certain external
stamens, not by a modification of true leaves. Instead
of being leaves arrested on their way towards
becoming stamens, they are really stamens which
have partially reverted towards the condition of
leaves. They differ from true leaves, however, in
their thin, spongy texture, and usually in the bright
pigments with which they are adorned.

All stamens show a great tendency easily to become
petaloid, as it is technically called ; that is to say,
to flatten out their filament or stalk, and finally to
lose their pollen-bearing sacs or anthers. In the
waterlilies — which are in certain ways one of the
oldest and simplest types of flowers we now possess
still preserving many antique points of structure
unchanged — we can trace a regular gradation from
the perfect stamen to the perfect petal. Take for
example our common English white waterlily,
Nymphcza alba (Fig. 3). In the centre of the flower
we find stamens of the ordinary sort, with rounded
stalks or filaments, and long yellow anthers full of
pollen at the end of each ; then, as we move outward,

12 THE COLOURS OF FLOWERS.

we find the filaments growing flatter and broader, and
the pollen-sacs less and less perfect ; next we find a
few stamens which look exactly like petals, only that
they have two abortive anthers stuck awkwardly on to
their summits ; and, finally, we find true petals, broad
and flat, and without any trace of the anthers at all.
Here in this very ancient though largely modified
flower we have stereotyped for us, as it were, the
mode in which stamens first developed into petals,
under stress of insect selection.1

F;c. 3. — Transition fr:m stamens into petals in white waterlily (Nymphara alba):

" But how do we know," it may be asked, " that the
transition was not in the opposite direction ? How
do we know that the waterlily had not petals alone to
start with, and that these did not afterwards develop,
as the Wolfian hypothesis would have us believe, into
stamens ? ° For a very simple reason. The theory
of Wolf and Goethe is quite incompatible with the
doctrine of development, at least if accepted as a

1 The waterlilies belong to a very ancient type, in some respects
partially intermediate between Monocotyledons and Dicotyledons ; but
the comparative unification of their pistil shows them to have under-
gone considerable modification.

THE ORIGIN OF PETALS. 13

historical explanation (which Wolf and Goethe of
course never meant it to be). Flowers can and do
exist without petals, which are no essential part of
the organism, but a mere set of attractive coloured
advertisements for alluring insects ; but no flower can
possibly exist without stamens, which are one of the
two essential reproductive organs in the plant. With-
out pollen, no flower can set its seeds. A parallel
from the animal world will make this immediately
obvious. Hive-bees consist of three kinds — the
queens or fertile females, the drones or males, and
the workers or neuters. Now it would be absurd to
ask whether the queens were developed from an
original class of neuters, or the neuters from an
original class of fertile females. Neuters left to them-
selves would die out in a single generation : they are
really sterilised females, set apart for a special function
on behalf of the hive. It is just the same with petals :
they are sterilised stamens, set apart for the special
function of attracting insects on behalf of the entire
flower. But to ask which came first, the petals or the
stamens, is as absurd as to ask which came first, the
male and female bees or the neuters.

Indeed, if we examine closely the waterlily petals,
it is really quite impossible to conceive of the transi-
tion as taking place from petals to stamens instead of
from stamens to petals. It is quite easy to under-
stand how the filament of an active stamen may
become gradually flattened, and the anthers (or pollen-
sacs) progressively void and functionless : but it is
very difficult to understand how or why a petal should
first begin to develop an abortive anther, and then a
partially effective anther, and at last a perfect stamen.

14 THE COLOURS OF FLOWERS.

The one change is comprehensible and reasonable,
the other change is meaningless and absurd. Of
course, it is not intended to deny the truth of Wolf's
great generalisation in the way in which he meant it
— the existence of a homology between the leaf and
all the floral organs : but the conception certainly
requires to be modified a little by the light of later
evolutionary discoveries. The starting-point consists
of a plant having three kinds of organs, true foliage
leaves, staminal leaves, and carpellary leaves : the
petals and sepals are apparently later intermediate
modifications, produced in special connection with the
acquired habit of insect fertilisation.

In many other cases besides the waterlily, we know
that stamens often turn into petals. Thus the
numerous coloured rays of the Mesembryanthemums
or ice-plant family are acknowledged by many
botanists to be flattened stamens. In Canna, where
one anther-cell is abortive, the filament of the solitary
stamen becomes petaloid. In the Ginger order, one
outer whorl of stamens resembles the tubular corolla,
so that the perianth seems to consist of nine lobes
instead of six. In orchids, according to Mr. Darwin,
the lip consists of one petal and two petaloid stamens
of the outer whorl. In double roses (Fig. 4) and almost
all other double flowers the extra petals are produced
from the stamens of the interior. In short, stamens
generally can be readily converted into petals, especi-
ally in rich and fertile soils or under cultivation. The
change is extremely common in the families of Ran-
unculacece, Papaveracccz, Magnoliacece, Malvacecz, and
Rosacece, all very simple types. Even where stamens
always retain their pollen-sacs, they have often broad,

THE ORIGIN OF PETALS.

flattened petaloid filaments, as in the star of Bethlehem
and many other flowers. The curious scales on the
petals of Parnassia palustris are now known to be
altered stamens. Looking at the question as a whole,
we can see how petals might easily have taken their
origin from stamens, while it is difficult to understand
how they could have taken their origin from ordinary
leaves — a process of which, if it ever took place, no
hint now remains to us. We shall see hereafter that
the manner in which certain outer florets in the
compound flower-heads of the daisy or the aster
have been sterilised and specialised for the work of

FIG. 4.— Transition from stamen (a) to petal (l>) and sepal (c) in flower of double rose.

attraction, affords an exact analogy to the manner in
which it is here suggested that certain stamens may
at an earlier date have been sterilised and specialised
for the same purpose, thus giving rise to what we
know as petals.

In a few rare instances, petals even now show a
slight tendency to revert to the condition of
fertile stamens. In Monandra fistulosa the lower lip
is sometimes prolonged into a filament bearing an
anther: and the petals of shepherds-purse (Capsella
bursa-pastoris) have been observed antheriferous.

The hypothesis upon which we shall hereafter

16 THE COLOURS OF FLOWERS.

proceed, therefore, will be that petals are really de-
rived from altered stamens. We shall return at a later
point to the proofs of this position, and examine a
few arguments which may be brought against it. For
the present, it will be better to put forward the
remainder of our general theory at once, without
interrupting the exposition by any alien controversial
matter. For the most part, it must find its evidence
in its perfect congruity with all the established facts
of the science.

CHAPTER II.

GENERAL LAW OF PROGRESSIVE COLOURATION.

IF the earliest petals were derived from flattened
stamens, it would naturally follow that they would be
for the most part yellow in colour, like the stamens
from which they took their origin. How, then, did
some of them afterwards come to be white, orange,
red, purple, lilac, or blue ? A few years ago, when the
problem of the connection between flowers and insects
still remained much in the state where Sprengel left
it at the end of the last century, it would have seemed
quite impossible to answer this question. But now-
adays, after the full researches of Darwin, Wallace,
Lubbock, and Hermann Miiller into the subject, we
can give a very satisfactory solution indeed. We now
know,, not only that the colours of flowers as a whole
are intended to attract insects in general, but that
certain colours are definitely intended to attract
certain special kinds of insects. Thus, to take a few
examples only out of hundreds that might be cited,
the flowers which lay themselves out for fertilisation
by miscellaneous small flies are almost always white ;
those which depend upon the beetles are frequently
yellow ; while those which specially bid for the favour

C

1 3 THE COLOURS OF FLOWERS.

of bees and butterflies are usually red, purple, lilac, or
blue. Certain insects always visit one species of
flower alone ; and others pass from blossom to
blossom of one kind only on a single day, though
they may vary a little from kind to kind as the season
advances, and one species replaces another. M tiller,
the most statistical of naturalists, has noticed that
while bees form seventy-five per cent, of the insects
visiting the very developed composites, they form
only fourteen per cent, of those visiting umbelliferous
plants, which have, as a rule, open but by no mevans
showy white flowers. Certain blossoms which lay
themselves out to attract wasps are, as he quaintly
puts it, "obviously adapted to a less aesthetically
cultivated circle of visitors." And some livid red
flowers actually resemble in their colour and odour
* decaying raw meat, thus inducing bluebottle flies to
visit them and so carry their pollen from head to
head.

Down to the minutest distinctions between species,
this correlation of flowers to the tastes of their par-
ticular guests seems to hold good. Hermann Miiller
notes that the common Galium of our heaths and
hedges (G. mollugd] is white, and therefore visited by
small flies ; while the lady's bedstraw, its near relative
(G. verum\ is yellow, and owes its fertilisation to little
beetles. Mr. H. O. Forbes counted on one occasion
the visits he saw paid to the flowers on a single bank ;
and he found that a particular bumble-bee sucked the
honey of thirty purple dead nettles in succession,
passing over without notice all the other plants in
the neighbourhood ; two other species of bumble-bee
and a cabbage-butterfly also patronised the same dead-

LA W OF PROGRESSIVE CCLO URA TION. 1 9

nettles exclusively. Fritz Miiller noticed a Lantana in
South America which changes colour as its flowering
advances ; and he observed that each kind of butterfly
which visited it stuck rigidly to its own favourite colour,
waiting to pay its addresses until that colour appeared.
Mr. Darwin cut off the petals of a lobelia and found that
the hive-bees never went near it, though they were
very busy with the surrounding flowers. But perhaps
Sir John Lubbock's latest experiments on bees are
the most conclusive of all. He had long ago con-
vinced himself, by trials with honey placed on slips of
glass above yellow, pink, or blue paper, that bees
could discriminate the different colours ; and he has now
shown in the same way that they display a marked
preference for blue over all other hues. The fact is,
blue flowers are, as a rule, specialised for fertilisation
by bees, and bees therefore prefer this colour ; while
conversely the flowers have at the same time become
blue because that was the colour which the bees
prefer. As in most other cases, the adaptation must
have gone on pari passu on both sides. As the bee-
flowers grew bluer, the bees must have grown fonder
and fonder of blue ; and as they grew fonder of blue,
they must have more and more constantly preferred
the bluest flowers.

We thus see how the special tastes of insects may
have become the selective agency for developing
white, pink, red, purple, and blue petals from the
original yellow ones. But before they could exercise
such a selective action, the petals must themselves
have shown some tendency to vary in certain fixed
directions. How could such an original tendency
arise? For, of course, if thes insects never saw any

C 2

20 THE COLOURS OF FLOWERS,

pink, purple, or blue petals, they could not specially
favour and select them ; so that we are as yet hardly
nearer the solution of the problem than ever.

Here Mr. Sorby, who has chemically studied the
colouring matter of leaves and flowers far more deeply
than any other investigator, supplies us with a useful
hint. He tells us that the various pigments of bright
petals are already contained in the ordinary tissues of
the plant, whose juices only need to be slightly
modified in chemical constitution in order to make
them into the blues, pinks, and purples with which we
are so familiar. "The coloured substances in the
petals," he says, " are in many cases exactly the same
as those in the foliage from which chlorophyll has
disappeared ; so that the petals are often exactly like
leaves which have turned yellow and red in autumn,
or the very yellow or red leaves of early spring." " The
colour of many crimson, pink, and red flowers is due
to the development of substances belonging to the
erythrophyll group, and not unfrequently to exactly
the same kind as that so often found in leaves. The
facts seem to indicate that these various substances
may be due to an alteration of the normal constituents
of leaves. So far as I have been able to ascertain,
their development seems as if related to extra oxidi-
sation, modified by light and other varying conditions
not yet understood.'

The different hues assumed by petals are all thus,
as it were, laid up beforehand in the tissues of the
plant, ready to be brought out at a moment's notice.
And all flowers, as we know, easily sport a little in
colour. But the question is, do their changes tend to
follow any regular and definite order ? Is there any

LA W OF PROGRESSIVE COLOURATION. 21

reason to believe that the modification runs from any
one colour toward any other ? Apparently there is.
The general conclusion to be set forth in this work is
the statement of such a tendency. All flowers, it
would seem, were in their earliest form yellow ; then
some of them became white ; after that, a few of them
grew to be red or purple ; and finally, a comparatively
small number acquired various shades of lilac, mauve,
violet, or blue. So that, if this principle be true, such
a flower as the harebell will represent one of the
most highly-developed lines of descent ; and its
ancestors will have passed successively through all the
intermediate stages. Let us see what grounds can be
given for such a belief.

Some hints of a progressive law in the direction of
a colour-change from yellow to blue are sometimes
afforded us even by the successive stages of a single
flower. For example, one of our common little
English forget-me-nots, Myosotis versicolor, is pale
yellow when it first opens ; but as it grows older, it
becomes faintly pinkish, and ends by being blue like
the others of its race. Now, this sort of colour-change
is by no means uncommon ; and in almost all known
cases it is always in the same direction, from yellow
or white, through pink, orange, or red, to purple or
blue. For example, one of the wall-flowers, Cheiran-
thus chamceleo, has at first a whitish flower, then a
citron-yellow, and finally emerges into red or violet.
The petals of Stylidiu m fruticosum are pale yellow to
begin with, and afterwards become light rose-coloured.
An evening primrose, (Enothera tetraptera, has white
flowers in its first stage and red ones at a later period
of development. Cobtza scandens goes from white to

22 THE COLOURS OF FLOWERS.

violet ; Hibiscus mutabilis from white, through flesh-
coloured, to red. The common Virginia stock of our
gardens (Malcolmia} often opens of a pale yellowish
green ; then becomes faintly pink ; afterwards deepens
into bright red ; and fades away at last into mauve or
blue. Fritz Miiller's Lantana is yellow on its first
day, orange on the second, and purple on the third.
The whole family of Boraginacece begin by being pink
and end with being blue. The garden convolvulus
opens a blushing white and passes into full purple.
In all these and many other cases the general direc-
tion of the changes is the same. They are usually
set down as due to varying degrees of oxidation in
the pigmentary matter.

If this be so, there is a good reason why bees should
be specially fond of blue, and why blue flowers should
be specially adapted for fertilisation by their aid. For
Mr. A. R. Wallace has shown that colour is most apt
to appear or to vary in those parts of plants or animals
which have undergone the highest amount of modifi-
cation. The markings of the peacock and the argus
pheasant come out upon their immensely developed
secondary tail-feathers or wing-plumes ; the metallic
hues of sun-birds and humming-birds show themselves
upon their highly-specialised crests, gorgets, or lap-
pets. It is the same with the hackles of fowls, the
head-ornaments of fruit pigeons, and the bills of
toucans. The most exquisite colours in the insect
world are those which are developed on the greatly
expanded and delicately-feathered wings of butter-
flies ; and the eye-spots which adorn a few species are
usually found on their very highly modified swallow-
tail appendages. So, too, with flowers ; those which

LA W OF PROGRESSIVE COLOURATION. 23

have undergone most modification have their colours
most profoundly altered. In this way, we may put
it down as a general rule (to be tested hereafter)
that the least developed flowers are usually yellow
or white ; those which have undergone a little
more modification are usually pink or red ; and
those which have been most highly specialised of
any are usually purple, lilac, or blue. Absolute
deep ultramarine probably marks the highest level
of all.

On the other hand, Mr. Wallace's principle also
explains why the bees and butterflies should prefer
these specialised colours to all others, and should
therefore select the flowers which display them by
preference over any less developed types. For bees
and butterflies are the most highly adapted of all
insects to honey-seeking and flower-feeding. They
have themselves -.on their side undergone the largest
amount of specialisation for that particular function.
And if the more specialised and modified flowers,
which gradually fitted their forms and the position of
their honey-glands to the forms of the bees or
butterflies, showed a natural tendency to pass from
yellow through pink and red to purple and blue, it
would follow that the insects which were being evolved
side by side with them, and which were aiding at the
same time in their evolution, would grow to recognise
these developed colours as the visible symbols of
those flowers from which they could obtain the largest
amount of honey with the least possible trouble.
Thus it would finally result that the ordinary un-
specialised flowers, which depended upon small insect
riff-raff, would be mostly left yellow or white ; those

24 THE COLOURS OF FLOWERS.

which appealed to rather higher insects would become
pink or red ; and those which laid themselves out for
bees and butterflies, the aristocrats of the arthropo-
dous world, would grow for the most part to be purple
or blue.

Now, this is very much what we actually find to be
the case in nature. The simplest and earliest flowers
are those with regular, symmetrical, open cups, like
the Ranunculus genus, the Potentillas, and the Alsinece,
or chickweeds, which can be visited by any insects
whatsoever; and these are in large part yellow or
white. A little higher are flowers like the campions
or Silenece, and the stocks (Matthiola), with more or
less closed cups, whose honey can only be reached by
more specialised insects ; and these are oftener pink
or reddish. More profoundly modified are those
irregular one-sided flowers, like the violets, peas, and
orchids, which have assumed special shapes to accom-
modate bees or other specific honey-seekers ; and
these are often purple and not unfrequently blue.
Highly specialised in another way are the flowers like
harebells (Campanula}, scabious (Dipsacecz), and heaths
(Ericacecs], whose petals have all coalesced into ^ a
tubular corolla ; and these might almost be said to be
usually purple or blue. And, finally, highest of all
are the flowers like labiates (rosemary, Salvia, &c.)
and speedwells ( Veronica), whose tubular corolla has
been turned to one side, thus combining the united
petals with the irregular shape ; and these are almost
invariably purple or blue.

We shall proceed to give a few selected examples
from the families best represented in the British
flora.

LA W OF PROGRESSIVE COLOURA TION, 25

The very earliest types of angiospermous flowers
now remaining are those in which the carpels still
exist in a separate form, instead of being united into
a single compound ovary. Among Dicotyledons, the
families, some of whose members best represent this
primitive stage, are the Rosacece and Ranunculacece ;
among Monocotyledons, the Alismacece. We may
conveniently begin with the first group.

FIG. 5. — Flower of cinquefoil (Potentilla). Primitive yellow.

The roses form a most instructive family. As a
whole they are not very highly developed flowers,
since all of them have simple, open, symmetrical
blossoms, generally with five distinct petals. But of
all the rose tribe, the Potentillece, or cinquefoil group, in-
cluding our common English silver-weed, seem to make
up the most central, simple, and primitive members
(Fig. 5). They are chiefly low, creeping weeds, and
their flowers are of the earliest symmetrical pattern,

26 THE COLOURS OF FLOWERS.

without any specialisation of form, or any peculiar
adaptation to insect visitors. Now, among the poten-
tilla group, nearly all the blossoms have yellow petals,
and also the filaments of the stamens yellow, as is
likewise the case with the other early allied forms,
such as agrimony (Agrimonia Eupatorid) and herb-
bennet (Geum urbanum}. Among our common yellow
species are Potentilla reptans (cinquefoil), P. tormcn-
tilla, P. argentea, P. verna, P. fruticosa, and P. anse-
rina. Almost the only white potentillas in England
are the barren strawberry (P. fragariastr 11111) and the
true strawberry (Fragaria vescd]^ which have, in many
ways, diverged more than any other species from the
norma of the race. Water-avens (Geum rivale), how-
ever, a close relative of herb-ben net, has a dusky
purplish tinge; and Sir John Lubbock notes that it
secretes honey, and is far oftener visited by insects
than its kinsman. The bramble tribe (Rubece), including
the blackberry (Fig. 6), raspberry, and dewberry, have
much larger flowers than the potentillas, and are very
greatly frequented by winged visitors. Their petals
are usually pure white, often with a pinky tinge,
especially on big, well-grown blossoms. But there is*
one low, little-developed member of the blackberry
group, the Rubus saxatilis, or stone-bramble, with
narrow, inconspicuous petals of a greenish-yellow,
merging into dirty white ; and this humble form seems
to preserve for us the transitional stage from the yellow
potentilla to the true white brambles. One step
higher, the cherries and apples (though genetically
unconnected), have very large and expanded petals,
white toward the centre, but blushing at the edges into
rosy pink or bright red (Fig. 7). We shall sea hereafter

LA W OF PROGRESSIVE COLOURA TION. 27

that new colours 'always make their appearance at the
outer side of the petal, while the base usually retains
its primitive colouration. For the present, this prin-

FIG. 6 —Vertical section of bramble-flower (Rubus). White.

ciple must be accepted on trust. Finally, the true roses
(Fig. 8), whose flowers are the most developed of all,
have usually broad pink petals (like those of our own

FIG. 7. — Vertical section of appli-blossom (Pyrus ntalus). Pinky white.

dog-rose, Rosa canina, R. villosa, R. rubigtnosa, &c.),
which, in some still bigger exotic species, become
crimson or damask of the deepest dye. They are

28 THE COLOURS OF FLOWERS.

more sought after by insects than any others of their
family.

Now, if we look closely at these facts, we see that
they have several interesting implications. The yellow
potentillas have the very simplest arrangement of the
carpels in the whole family, and their fruit is of the
most primitive character, consisting only of little dry
separate nuts. They have altered very little from
their primitive type. Accordingly, almost all the
genus is yellow ; a very few members only are white ;
and these in their habits so far vary from the rest that

FIG. 8. — Vertical section of dog-rose {Rosa). Pink.

they have very erect flowers, and three leaflets instead
of five or more to each leaf. One of them, the straw-
berry, shows still further marks of special differentia-
tion, in that it has acquired a soft, pulpy, red fruit, pro-
duced by the swelling of the receptacle, and adapted
to a safer mode of dispersal by the aid of birds. This
group, however, including Geuin, cannot claim to be
considered the earliest ancestral form of the roses,
because of its double calyx, which is not shared by
other members of the family, as it would be if it had
belonged to the actual, common ancestor. In that

LA W OF PROGRESSIVE COLOURA TION, 29

respect, agrimony more nearly represents the primitive
form, though its tall habit and large spikes of flowers
show that it also has undergone a good deal of modi-
fication. Nevertheless, the yellow members of the
potentilla group, in their low creeping habit, their
want of woodiness, and their simple fruit, certainly
remain very nearly at the primitive ancestral stage,
and may be regarded as very early types of flowers
indeed. It is only among handsome and showy
exotic forms, which have undergone a good deal more
modification, that we get brilliant red-flowered species
like the East Indian P. nepalensis and P. atropurpurea.
But as soon as the plants rise a little in the scale,
and the flowers grow larger, we get a general tendency
towards white and pink blossoms. Thus the Prunece
have diverged from the central stock of the rose
family in one direction, and the Pomece and Rosece in
another ; but both alike begin at once to assume white
petals ; and as they lay themselves out more and more
distinctly for insect aid, the white passes gradually
into pink and rose-colour. To trace the gradations
throughout, we see that the Rubece, or brambles, are
for the most part woody shrubs instead of being mere
green herbs, and they have almost all whitish blossoms
instead of yellow ones ; but their carpels still remain
quite distinct, and they seldom rise to the third stage
of pinkiness ; when they do it is generally just as
they are fading, and we may lay it down as a
common principle that the fading colours of less
developed petals often answer to the normal colours
of more developed. In the Prunece, again, the de-
velopment has gone much further, for here most of
the species are trees or hard shrubs, and the number

30 THE COLOURS OF FLOWERS.

of carpels is reduced to one. They have a succulent
fruit — a drupe, the rr'ghest type — and though the
flower contains two ovules, the ripe plum has only
one seed, the other having become abortive. All
these are marks of high evolution : indeed, in most
respects the Prunece stand at the very head of the rose
family ; but the petals are seldom very expanded, and
so, though they are usually deeply tinged with pink
in the cherry (Primus cerasus), and still more so in
larger exotic blossoms, like the almond, the peach,
and the nectarine, they seldom reach the stage of red.
Our own sloe (P. commums] has smallish white
flowers, as has also the Portugal laurel (P. lusi-
tanicus). In these plants, in fact, higher development
has not largely taken the direction of increased attrac-
tion for insect fertilizers; it has mainly concentrated
itself upon the fruit, and the devices for its dispersal
by birds or mammals. In the Rosecz, on the other
hand, though the fruit is less highly modified, the
methods for ensuring insect fertilisation are carried
much further. There are several carpels, -but they
are inclosed within the tube of the calyx, and the
petals are very much enlarged indeed, while in some
species the styles are united in a column. As regards
insect-attraction, indeed, the roses are the most ad-
vanced members of the family, and it is here, accord-
ingly, that we get the highest types of colouration.
Most of them are at least pink, and many are deep
red or crimson. Among the Pomea, we find an inter-
mediate type (as regards the flowers alone) between
Rosece and Prunece ; the petals are usually bigger and
pinker than those of the plums ; not so big or so pink
as those of the true roses. This interesting series

LA W OF PROGRESSIVE COLOURA TION. 51

exhibits very beautifully the importance as regards
colouration of mere expansion in the petals. Taking
them as a whole we may say that the smallest petals
in the rose family are generally yellow; the next in
size are generally white ; the third in order are gene-
rally pink ; and the largest are generally rose-coloured
or crimson.

At the same time, the roses as a whole, being a
relatively simple family, with regular symmetrical
flowers of the separate or polypetalous type, have
never risen to the stage of producing blue petals.
That, probably, is why our florists cannot turn out a
blue rose. It is easy enough to make roses or any
other blossoms vary within their own natural limits,
revert to any earlier form or colour through which
they have previously passed ; but it is difficult or
impossible to make them take a step which they have
never yet naturally taken. Hence florists generally
find the most developed flowers are also the most
variable and plastic in colour ; and hence, too, we can
get red, pink, white, straw-coloured, or yellow roses,
but not blue ones. This would seem to be the
historical truth underlying De Candolle's division of
flowers into a xanthic and cyanic series. Of course,
there is nothing to prevent florists from developing a
blue rose in the same way as the insects would do it,
by gradually selecting and preserving the most bluish
or slate-coloured among their pink or crimson kinds.
But it would appear from the comparative rarity of
blue flowers in nature that the spontaneous variations
which make towards blue are far less frequent than
those which make towards pink, red, purple, or
orange.

32 THE COLOURS OF FLOWERS.

There is one small set of rosaceous plants which
exhibit green flowers, such as the genera Alchemilla
and Poterium. When we come to consider the sub-
ject of degeneration, however, we shall see that these
are not really primitive blossoms, but very degraded
and altered types. For the present, it must suffice to
point out that they have lost some of their sepals, all
their petals, and many of their carpels ; and that they
cannot therefore be regarded in any way as represen-
tatives of the central primordial stock from which the
roses are originally derived. This place certainly
belongs rather to Potentilla, Agrimoma, and some
allied exotic types, with simple regular yellow
blossoms.

Even more primitive in type than the Rosacecz are
the lowest members of the Ranunculacece, or buttercup
family, which perhaps best of all preserve for us the
original features of the early dicotyledonous flowers.
The family is also more interesting than that of the roses
because it contains greater diversities of development,
and accordingly covers a wider range of colour, its
petals varying from yellow to every shade of crimson,
purple, and blue. The simplest and least differentiated
members of the group are the common meadow butter-
cups (Fig. 9), forming the genus Ranunculus, which, as
everybody knows, have five open petals of a brilliant
golden hue. Nowhere else is the exact accordance in
tint between stamens and petals more noticeable
than in these flowers. The colour of the filaments
is exactly the same as that of the petals ; and the
latter are simply the former a little expanded and
deprived of their anthers. We have several English
meadow species, all with separate carpels, and all very

LA IV OF PROGRESSIVE COLOURATION. 33

primitive in organization, such as R. acris (the central
form), R. bulbosus, R. repens, R.flammula, R. sceleratus,
R. auricomus, R. philonotis, &c. In the lesser celan-
dine or pilewort, R. ficaria, there is a slight divergence
from the ordinary habit of the genus, in that the
petals, instead of being five in number, are eight or
nine, while the sepals are only three; and this
divergence is accompanied by two slight variations in
colour : the outside of the petals tends to become
slightly reddish or purplish, and the flowers fade

FIG. 9. — Vertical section of buttercup {Ranunculus acris)', primitive yellow.

white, much more distinctly than in most other
species of the genus.

There are two kinds of buttercup in England, how-
ever, which show us the transition from yellow to white
actually taking place under our very eyes. These
are the water-crowfoot, R. aquatilis (Fig. 90), and its
close ally the ivy-leaved crowfoot, R. hederaceus, whose
petals are still faintly yellow toward the centre, but
fade away into primrose and white as they approach
the edge. We have already noticed that new colours
usually appear at the outside, while the claw or base

D

34 THE COLOURS OF FLOWERS,

of the petal retains its original hue ; and this law is
strikingly illustrated in these two crowfoots. It is
remarkable, too, that in this respect they closely
resemble the half-faded flowers of the lesser celandine,
which become white from the edge inward as they
die. The petals also similarly vary, in number,
though to a less extent. White flowers of the sam-e
type as those of water-crowfoot are very common
among aquatic plants of like habit, and they seem to
be especially adapted to water-side insects.

FIG. ga. — Flower of water crowfoot (Rantmc-uhts aquatilis); white, with yellow
claws.

In many Ranunculacecz there is a great tendency
for the sepals to become petaloid, and this peculiarity
is very marked in Caltha palus tris, the marsh-marigold,
which has no petals, but bright yellow sepals, so
that it looks at first sight exactly like a very large
buttercup.

The clematis and anemone, which are more highly
developed, have white sepals (for the petals here also
are suppressed), even in our English species ; and
exotic kinds varying from pink to purple are culti-
vated in our flower-gardens.

LA W OF PROGRESSIVE COLOURA TION. 35

It is among the higher ranunculaceous plants, how-
ever, that we get the fullest and richest colouration.
Columbines (Aquilegia) are very specialised forms of
the buttercup type (Fig. 10). Both sepals and petals

FIG. 10. — Flower of columbine (.A quilegia vulgaris), with petals produced into
honey-bearing spurs ; purple or blue.

are brightly coloured, while the former organs are pro-
duced above into long, bow-shaped spurs (Fig. 1 1), each
of which secretes a drop of honey. The carpels are also

D 2

36 THE COLOURS OF FLOWERS.

reduced to five, the regularity of number being itself
a common mark of advance in organization. Various
columbines accordingly range from red to purple and
dark blue. Our English species, A. vulgaris, is blue
or dull purple, though it readily reverts to white or
red in cultivated varieties. Even the columbine,
however, though so highly specialised, is not bila-
terally but circularly symmetrical. This last and
highest mode of adaptation to insect visits is found in
larkspur (Delphinium ajacis), and still more developed
in the curious monkshood (Aconitum napellus, Fig. 12).

FIG. ii. — Petal of columbine produced into a honey-bearing spur.

Now larkspur is usually blue, though white or red
blossoms sometimes occur by reversion ; while monks-
hood is one of the deepest blue flowers we possess.
Both show very high marks of special adaptation ;
for besides their bilateral form, Delphinium has the
number of carpels reduced to one, the calyx coloured
and deeply spurred, and three of the petals abortive ;
while Aconitum has the carpels reduced to three and
partially united into a compound ovary, the upper
sepals altered into a curious coloured hood or helmet,
and the petals considerably modified (Fig. 13). All
these very complex arrangements are defintely corre-

LA W OF PROGRESS! VE COLOURA TION. 3?

lated with the visits of insects, for the two highly
abnormal petals under the helmet of the monkshood
produce honey, as do also the two long petals within the
spur of the larkspur. Both flowers are also specially
adapted to the very highest class of insect visitors.

FIG. 12. — Flowers of monkshood (A conitum napellus) > dark blue.

Aconitum is chiefly fertilized by bees ; and Sir John
Lubbock observes that " Anthophora pilipes and Bom-
bus hortorum are the only two North European
insects which have a proboscis long enough to reach
to the end of the spur of Delphinium elatum, A.

38 THE COLOURS OF FLOWERS.

pilipes, however, is a spring insect, and has already
disappeared before the Delphinium comes into flower,
so that it appears to depend for its fertilisation
entirely on Bombus hortorum"

Thus within the limits of the Ranunculacecs we get
every gradation in colouring, from the very simple,
open, yellow buttercups, through the white water

FIG. 13.— Petals of monkshood, concealed by sepals, and produced into honey-
bearing sacs.

crowfoots, the red adonis, the scarlet paeony, and the
purple columbine, to the very irregular blue larkspur,
and the extremely complex ultramarine monkshood.
In this family it may be noted, too, that increase of
adaptation to insect visits is shown rather by peculi-
arities of shape and arrangement than by mere
increased size of petals, as among the roses.

Observe also that every advance either in insect

LAW OF PROGRESSIVE COLOURATION. 39

fertilization or in special adaptation for dispersal of
seeds results in a lessening of the number of carpels
or of seeds. The plant does not need to produce so
many when all are fairly sure of arriving at maturity
and being dispersed.

Flowers in which the carpels have arranged them-
selves in a circle around a common axis, like the
Geraniacea and Malvacece, thereby show themselves
to be more highly modified than flowers in which all
the carpels are quite separate and scattered, like the
simpler Rosacece and Ranunculacecz. Still more do
families such as the Caryophyllacecz, or pinks, in which
all the five primitive carpels have completely coalesced
into a single five-celled ovary. Accordingly, it is cot
remarkable that the pinks should never be yellow.
On the other hand, this family has no very specialised
members, like the larkspur and the monkshood, and
therefore it very rarely produces bluish or purplish
flowers. Pinks, in fact, do not display so wide a
range in either direction as Ranunculacecz. They
begin as high up as white, and hardly get any higher
than red or carnation. They are divisible into two
sub-families, Alsinece and Silenecz. The Alsinece have
the sepals free, the blossoms widely expanded, and no
special adaptations for insect fertilization (Fig. 14).
They include all the small undeveloped field species,
such as the chickweeds (Stellaria media, A renaria trin-
ervisy Cerastium vulgatum, &c.), stitchworts (Stellaria
holostea, &c.), and cornspurries (Spergula arvensis),
which have open flowers of a very primitive character ;
and almost all of them are white. These are ferti-
lized by miscellaneous small flies. The Silenecz, on the
other hand, including the large-flowered types such as

THE COLOURS OF FLOWERS.

the campions (Fig. 15) and true pinks, have a tubular
calyx, formed by the coalescence of the five sepals,
and the expanded petals are raised on long claws ;
which makes their honey, inclosed in the tube, acces-
sible only to the higher insects. Most of them also
display special adaptations for a better class of insect
fertilization in the way of fringes or crowns on the
petals. These more profoundly modified kinds are

FIG. 14. — Flowers of chickweed (Stellaria) ; white.

generally pink or red. For example, in the most
advanced British genus, Dianthus, which has usually
vandyked edges to the petals, our four English species
are all brightly coloured, D. armeria, the Deptford
pink, being red with dark spots, D. prolifer purplish
red, D. deltoides, the maiden pink, rosy spotted with
white, and D. ccesius, the Cheddar pink, bright rose-
coloured. It is much the same with the allied genus
Lychnis.

LAW OF PROGRESSIVE COLOURATION. 41

Our own beautiful purple English corn-cockle
(L. githago), is a highly developed campion, so
specialised that only butterflies can reach its honey
with their long tongues, as the nectaries are situated
at the bottom of the tube. Two other species of
campion, however, show us interestingly the way
in which variations of colour may occur in a retro-
grade direction even among highly evolved forms.

FIG. 15. — Flower of night campion {Lychnis vespertina) ; white.

One of them, the day lychnis, (L. diurnd), has red,
scentless flowers, opening in the morning, and it is
chiefly fertilized by diurnal butterflies. But its de-
scendant, the night lychnis (L. vespertina), has taken
to fertilization by means of moths ; and as moths can
only see white flowers it has become white (Fig. 1 5), and
has acquired a faint perfume as an extra attraction.
Still, the change has not yet become fully organised

42 THE COLOURS OF FLOWERS.

in the species, for one may often find a night lychnis
at the present time which is only pale pink, instead of
being pure white.

Sir John Lubbock remarks of the Caryophyllacece
that " the order presents us with an interesting series
commencing with open-flowered species, the honey of
which is accessible even to beetles, and short-tongued
flies, through those which are adapted to certain flies
(Rhingia) and Bees ; to the species of Diant/ius,
Saponaria, and Lychnis Githago, the honey of which
is accessible to Lepidoptera only." It is a curious
fact that in just the same progression the flowers pass
gradually from small white inconspicuous petals to
large and deeply coloured red or purple ones.

The Cistacece are another family of simple flowers,
with the carpels united, but otherwise very primitive
in form. Their petals usually spread around the ovary
in a regular discoid form ; and the earliest members
only differ essentially from Potentilla in the union of
their carpels into a single imperfectly three-celled
capsule. Our English genus, Helianthemum or rock-
rose, comprises some of the smallest and simplest
forms, with yellow petals, and very like Potentilla in
general appearance. One species, however, H.poli-
folium (a mere slight variation on the yellow H.
vulgare), has white flowers. The larger South Euro-
pean forms, which make up the genus Cistus, have
much more expanded petals, and these are usually
white, pinkish, or rose-coloured. One Mediterranean
species has a yellow centre with white edges : another
closely allied to it, has a white centre with pink edges.
Here, as in the roses, mere increase in size (coupled
of course with special insect selection) seems to have

LA W OF PROGRESSIVE COLOUR A TION. 43

effected the progressive modification of the pig-
mentary matter.

The Papaveracece or poppies show us somewhat
similar results. Many of the less developed forms,
with small petals, are yellow. For example, the
celandine, Chelidonium majus, has a very simple ovary
and comparatively inconspicuous flowers : and its
petals are of just the same primitive golden yellow as
those of the buttercups, the potentillas, and the rock-
roses. GlaMcium luteum, another little-developed
form, is also yellow. So are the Californian Esch-
scholtzias of our gardens. But in the field poppies,
Papaver rhczas, P. dubium, P. hybridum, &c., which
have extremely large and expanded petals, together
with a highly modified compound ovary, bright scarlet
is the prevailing colour, though pale red and white
also occur. The still larger garden poppy, P. somni-
ferum, is bluish white, with a purple base to the
petals.

The Cruciferce are a family which display a good
deal of variety of colouration, though not so largely
within the limits of our British species. The most
primitive and simple forms have yellow flowers, as in
the case of the cabbage genus (Brassica) including char-
lock, mustard, and turnip ; the rockets (Barbarea and
Sisymbriuni) ; and the gold-of-pleasure (Camelina
sativa). Most of these are dry-field weeds, and they
have open little-developed blossoms. Their petals
usually fade white. In the genus Nasturtium or
watercress we have four species, three of which are
yellow, while one is white. In treacle-mustard (Ery-
simum\ the yellow is very pale, and the petals often
become almost white. Just above these earliest forms

44 THE COLOURS OF FLOWERS.

come the common small white crucifers like Cardamine
hirsuta, Cochlearia officinalis, and Capsella bursa-
pastoris. Many of these are little if at all superior in
organization to the yellow species, and some of them (as
we shall see hereafter) are evidently degenerate weeds
of cultivation. But such flowers as Alyssum mariti-
mum> with its sweet scent, its abundant honey, its
reduced number of seeds, and its conspicuous,
spreading milk-white petals, are certainly more
developed than small yellow species like Alyssum caly-
cinum. Even more remarkably is this the case in the
genus Iberis or candytuft, which has become slightly
irregular, by the two adjoining exterior petals growing
larger than the interior ones. They thus form very
conspicuous heads of bloom, obviously adapted to
higher insect fertilisation. Accordingly, they are
usually white, like our British species, /. amara ; while
some of the larger exotic species are a pretty pink in
hue. The genus Cardamine supplies us with like
instances. Here the smaller species have white
flowers, and so has the large C. amara. But in
C. pratensiSy the cuckoo-flower, they are usually tinged
with a pinkish purple, which often fades deep mauve ;
and in some showy exotic species the flowers are a
rich pink. So with Arabis : our small English kinds
are white; A. petrcza, with larger petals, is often
slightly purplish, and some handsome exotics are a
vivid purple. In Hesperis we get a further degree of
modification in that the petals are raised on rather
long claws ; and the flowers (represented in England
by H. matronalis, the dame's-violet) are a fine purple
and possess a powerful perfume. Closely allied is
the Virginia stock of our gardens, (Malcohnid) which

LA W OF PROGRESSIVE COLOURATION. 45

varies from pale pink to mauve : its calyx has become
tubular. Yellow blossoms occasionally occur in this
genus. But the highest of all' our crucifers are con-
tained in the genera Matthiola and Cheiranthus, which
have large spreading petals on long erect claws,
besides often being sweet scented. The common
stock (M. incana) is purple, reddish, or even violet ;
our other British species, M. sinuata, is pale lilac ; and
no member of the genus is ever yellow. The wall-
flower (Cheiranthus ctieirt) is rich orange or red, some-
times yellow : its colour, however, differs widely from
the primitive golden yellow of the charlocks or
buttercups ; and it will receive further attention here-
after.

There is one special (perhaps artificial) tribe of
crucifers, the Lomentosa, which display specially high
modification in the pod or fruit ; and these deserve
separate treatment. Yellow flowers are here very
rare ; but one English species, Isatis tinctoria, the
dyer's woad, has small yellow petals. Raphanus
raphanistrum, the wild radish, has usually in its sea-
coast form pale primrose blossoms, much larger than
woad ; but inland they are oftener white with coloured
veins, and sometimes even lilac. Crambe maritima,
the seakale, a somewhat more developed type, is
always white, never yellow ; and Cakile maritima, a
still higher plant of the same tribe, has purple
blossoms, much like those of a stock.

So much by way of illustration of the families with
usually regular polypetalous flowers and free superior
ovaries. The other families of this type not noticed
here will receive attention in a later chapter. We
may next pass on to the families of polypetalous

46 THE COLOURS OF FLOWERS.

flowers with usually irregular corollas, which represent
of course a higher stage of development in adaptation
to insect visits.

Of these, three good illustrative cases are included
in the British flora. They are the Polygalacece, the
Violacece, and the Papilionacecs.

Poly gala vulgaris, or milkwort, our only British
representative of the first named family, is an ex-
tremely irregular flower, very minutely and remark-
ably modified for special insect fertilisation. It is
usually a bright blue in colour, but it often reverts to
pink, and not infrequently even to white. Two of
the sepals are coloured, as well as the petals.

The Violacece or violets are a whole family of
bilateral flowers, highly adapted 'to fertilisation by
insects ; and as a rule they are a deep blue in colour.
This is the case with four of our British species, Viola
odorata, V. canina, V. hirta, and V. palustris. Here,
too, however, white varieties easily arise by reversion ;
while one member of the group, the common pansy,
V. tricolor, is perhaps the most variable flower in all
nature. This case, again, will receive further attention
when we come to consider the subject of variegation
and of reversion or retrogression.

The Papilionacecz or peaflowers are closely related
to the roses, but differ conspicuously in their bilateral
form. The lower and smaller species, such as the
medick, lotus, and lady's fingers, are usually yellow,
though often reddish outside. So also are broom
and gorse. Among the more specialised clovers,
some of which are fertilised by bees alone, white,
red, and purple predominate. Even with the smaller
and earlier types, the most developed species, like

LAW OF PROGRESSIVE COLOURATION. 47

lucerne, are likewise purple or blue. But in the
largest and most advanced types, the peas, beans,
vetches, and scarlet runners, we get much brighter and
deeper colours, often with more or less tinge of blue.
In the sweet-peas and many others, the standard
frequently differs in hue from the keel or the wings —
a still further advance in heterogeneity of colouration.
Lupines, sainfoin, everlasting pea, and wistaria are
highly evolved members of the same family, in which
purple, lilac, mauve, or blue tints become distinctly
pronounced. The colouration of the Papilionacece,
however, does not as a whole illustrate the general law
so well as that of many other groups.

When we pass on to the Corolliflora, or flowers in
which the originally separate petals have coalesced
into a single united tube, we meet with much more
striking results.

Here, where the very shape at once betokens high
modification, yellow is a comparatively rare colour
(especially as a ground-tone, though it often comes out
in spots or patches), while purple and blue, so rare
elsewhere, become almost the rule.

The family of Campanulacecsy or bluebells, forms an
excellent example. Its flowers are usually blue or
white, and the greater number of them, like the hare-
bell (Campanula rotundifolia] and the Canterbury bell
(C. media), are deep blue (Fig. 1 6). We have nine British
species of the genus, varying from pale sky-blue to ultra-
marine and purplish cobalt, with an occasional relapse
to white. Rampion and sheep's bit, also blue, are
clustered heads of similar blossoms. The little blue
lobelia of our borders, which is bilateral as well as
tubular, belongs to a closely-related tribe. One of

THE COLOURS OF FLOWERS.

our British species, Lobelia Dortmanna, is sky-blue ;
the other, L. urens, is a dingy purple. Not far from
them are the Dipsacece, including the lilac scabious,
the blue devil's bit, and the mauve teasel. Amongst

FIG. 16.— Flower of harebell (Campanula); bright blue.

all these very highly- evolved groups blue distinctly
forms the prevalent colour.

In the great family of the Ericacece, or heaths, which
is highly adapted to insect fertilisation, more particu-
larly by bees, purple and rose are the prevailing tints,

LAW OF PROGRESSIVE COLOURATION. 49

so much so that, as we all have noticed a hundred
times over, they often colour whole tracts of hillside to-
gether. In all probability there are no really yellow
heaths. The bell-shaped blossoms mark at once the
position of the heaths with reference to insects ; and
the order, according to Mr. Bentham, supplies us
with more ornamental plants than any other in the
whole world. Among our British species, in the less
developed forms, like V actinium, Arbutus, and Andro-
meda, the flowers are usually white, flesh-coloured,
pinkish, or reddish. The highly developed Erica, on
the other hand, are mostly purple or deep red. E.
vulgaris has the calyx as well as the corolla coloured
with a mauve variety of pink. Menziesia ccerulea is a
deep purplish blue. Monotropa alone, a very degraded
leafless saprophyte form, has greenish-yellow or pale
brown free petals.

The Boraginacea are another very advanced family
of Corolliflorce, and they are blue almost without
exception. They have usually highly - modified
flowers, with a tube below and spreading lobes above ;
in addition to which most of the species possess
remarkable and strongly-developed appendages to the
corolla, in the way of teeth, crowns, hairs, scales,
parapets or valves. Of the common British species
alone, the forget-me-nots (Myosotis) are clear sky-
blue with a yellow eye ; the viper's bugloss (Echium
vulgare) is at first reddish purple, and afterwards a
deep blue ; the lungwort (Pulmonaria officinalis] is
also dark blue ; and so are the two alkanets (Anchusd),
the true bugloss (Lycopsis), the madwort (Asperugo],
and the familiar borage (Borago officinalis), used to
flavour claret-cup ; though all of them by reversion

E

50 THE COLOURS OF FLOWERS.

occasionally produce purple or white flowers. Hounds-
tongue (Cynoglossum officinale) is purple-red, and most
of the other species vary between purple and blue ;
indeed, throughout the family most flowers are red at
first and blue as they mature. The purplish-red of
the less advanced species exactly answers to the
immature colouring of the more advanced, which are
blue in their full-blown stage. Of these, borage at
least is habitually fertilised by bees, and the same is
partially true of many of the other species. All of
them are adapted to a high class of insect visitors.

Other families of regular Corolliflorce must be
glanced at more briefly. Among the Gentianacece,
the less advanced types, like the simple Chlora per-
foliata and Limnanthemum nymphceoides, are yellow,
perhaps by reversion ; but Menyanthes trifoliata, a
slightly more developed ally of Limnanthemum, has
white blossoms, tinged outside with red ; Erythrcza
centaurium, with a divided calyx and the cells of the
ovary imperfectly united, is red ; and the true gentians,
Gentiana verna, G. campestris, G. nivalis, &c., with a
tubular calyx, long throat, and sometimes fringed
hairs to the tube, are bright blue. In Apocynacecs, we
have the highly developed periwinkles, Vinca major
and V. minor, normally blue, though pink and white
varieties or species are also cultivated. In Plumbaginecz
we have the bluish purple sea-lavender (Statice Li-
moniuni] and the pink thrift (A rmeria vulgaris). Other
families with special peculiarities will receive notice
later on.

It is necessary, however, here briefly to refer to the
great family of Composites, some of whose peculiarities
can only properly be considered when we come to

LA IV OF PROGRESSIVE COLOURATION. 51

inquire into the phenomena of relapse and retrogres-
sion. Nevertheless, even at the present stage of our
inquiry, the composites afford some excellent evidence.
In certain ways they may be regarded as the very
highest race of flowering plants. Not only are their
petals united into a tubular corolla, but their blossoms
are compounded into large bunches or groups of a
very showy and attractive sort. Each flower-head
here consists of a number of small florets, crowded
together so as to resemble a single blossom. So far
as our present purpose is concerned, they fall natur-
ally into three groups — Jussieu's old-fashioned sub-
orders of Ligulatce, Cynaroidecz, and Cory mbife fee,
which are quite sufficient for all ordinary objects of
botanical study. The first, or ligulate tribe, is that
of the dandelions or hawkweeds, with open florets,
fertilised, as a rule, by very small insects ; and these
are generally yellow, with only a very few divergent
species. They will receive further notice hereafter.
The second, or cynaroid tribe, is that of the thistle-
heads, visited by an immense number of insects, in-
cluding the bees ; and these are almost all purple,
while some highly-evolved species, like the corn-flower
or blue-bottle (Centaurea cyanus, Fig. 17) and the true
artichoke (Cynara scolymus], are bright blue. The
third, or corymbiferous tribe, is that of the daisies and
asters, with tubular central florets and long flattened
outer rays ; and these demand a closer examination
here.

The central florets of the daisy tribe, as a rule, are
bright golden ; a fact which shows pretty certainly
that they are descended from a common ancestor
who was also yellow. Moreover, these yellow florets

E 2

THE COLOURS OF FLOWERS.

are bell-shaped, and each contains a pistil and five
stamens, like any other perfect flower. But the outer
florets are generally sterile ; and instead of being

FIG. 17. — Flower of corn bluebottle (Cenia-urea cyanus); highest type of cynaroid
composite ; bright blue.

bell-shaped they are split down one side and unrolled,
so as to form a long ray ; while their corolla is at
the same time much larger than that of the central

LA W OF PROGRESSIVE COL O URA TION. 5 3

blossoms (Fig. 18). In short, they are sterilised mem-
bers of the compound flower-head, specially set apart
for the work of display ; and thus they stand to the
entire flower-head in the same relation as petals do to
the simple original flower. The analogy between the
two is complete. Just as the petal is a specialised
and sterilised stamen told off to do duty as an
allurer of insects for the benefit of the whole flower,
so the ray-floret is a specialised and sterilised blos-
som told off to do the self-same duty for the benefit

FIG. 18.— Vertical section of head of daisy (Bellis pe rennls) \ central florets, yellow ;
ray florets, white, tipped with pink.

of the group of tiny flowers which make up the
composite flower-head.

Now, the earliest ray-florets would naturally be
bright-yellow, like the tubular blossoms of the central
disk from which they sprang. And to this day the
ray-florets of the simplest corymbiferous types, such
as the corn-marigold (Chrysanthemum segetum), the
sun-flower (Helianthus annuus], and the ragwort
(Senecio jacobced}, are yellow like the central flowers.
In the camomile, however, the ox-eye daisy, and the
may-weed (Anthemis cotula, Chrysanthemum leucan-
t/iemum, &c.), the rays have become white ; and this,

54 THE COLOURS OF FLOWERS.

I think, fairly establishes the fact that white is a
higher development of colour than yellow ; for the
change must surely have been made in order to
attract special insects. Certainly, such a differentia-
tion of the flowers in a single head cannot be without
a good purpose. In the true daisy, again (Bcllis
perennis], the white rays become tipped with pink (Fig.
1 8) which sometimes rises almost to rose-colour ; and
this stage is exactly analogous to that of apple-
blossom, which similarly halts on the way from white
petals to red. In our own asters (A. tripolium, &c.)
and the Michaelmas daisies of America, we get a
further advance to purple, lilac, and mauve, while
both in these and in the chrysanthemums true shades
of blue not infrequently appear. The Cinerarias of
our gardeners are similar forms of highly-developed
groundsels from the Canary Islands.

Tubular flowers with an irregular corolla are ob-
viously higher in their mode of adaptation to insect
visits than tubular flowers of the ordinary symmetrical
type. Amongst them, the first place must be as-
signed to the Labiates — perhaps the most specialised
of any so far as regards insect fertilisation. Not
only are they deeply tubular, but they are very
bilateral and irregular indeed, displaying more modi-
fication of form than almost any other flowers except
the orchids. They mostly secrete abundant honey,
and often possess highly aromatic perfumes. More-
over, they form geologically one of the latest families
of flowering plants, specially developed in adaptation
to bees and other highly-evolved honey-suckers.
Almost all of them are purple or blue. Among the
best known English species are thyme, mint, marjoram,

LA W OF PROGRESSIVE COLOURA TION. 55

sage (Fig. 19), and basil, which it need hardly be said
are great favourites with bees. Ground-ivy (Nepeta gle-
chomd) is bright blue ; catmint (Nepeta cataria], pale
blue ; Prunella, violet-purple ; and common bugle
(Ajuga reptans], blue or flesh-colour. Many of the
others are purple or purplish. It must be added that
in this family the flowers are very liable to vary
within the limit of the same species ; and red, white,
or purple specimens are not uncommon in many of
the normally blue kinds.

FIG. 19. — Flower of sage (Salvim) visited by bee ; blue.

The Scropkularinecz and other allied irregular tubular
families are mostly spotted, and so belong to a later
stage of our inquiry ; but even amongst this group,
the Veronica genus has almost always pure blue
flowers ; foxglove (Digitalis purpured] is purple; and
most of the Broomrapes (Orobanchacece] are more or
less bluish. Blue and lilac also appear abundantly
in spots or stripes in many species of Linaria, in
Euphrasia, and in other genera,

We have given so much consideration to the Dico-
tyledons that the relatively simple and homogeneous

56 THE COLOURS OF FLOWERS.

Monocotyledons need not detain us long. Their
colouration is as a whole both less complicated and
less instructive. As a rule, sepals and petals are here
petaloid and often indistinguishable.

The AlismacecE answer very closely to the Ranun-
culacece as being in all probability the earliest sur-
viving type of entomophilous Monocotyledons. Their
arrangement is of course trinary, but they have
similarly separate carpels, often numerous, surrounded
by one, two, three, or many rows of stamens, and
then by one row of three petals and one row of three
sepals. All our English species, however, are white
or rosy, instead of yellow. As they are marsh plants,
they seem, to have reached or passed the stage of
Ranunculus aquatilis. One species, A lisma plantago,
the water-plantain, however, still retains a yellow
claw to the petals, though the limb is white or pale
pink. So also does Damasonium stellatum. These
two interesting plants present a remarkable analogy
to the water-crowfoot.

Among monocotyledonous families with a united
ovary, the Liliacece are probably the most primitive.
Their simplest type in England is Gagea lutea (Fig. 20),
a yellow lily looking extremely like a bunch of Ranun-
culus Ficaria. In Lloydia serotina, a closely allied
but more developed form, the petals are white, with
a yellow base, and three reddish lines. The wild
tulip is likewise yellow. A Ilium ursinum, a some-
what higher type, is pure white. The fritillary
(Fritillaria Meleagris], a large, handsome, bell-shaped
flower, with separate petals converging into a campanu-
late form, and with a nectariferous cavity at their base
(Fig. 21), is purple or red, chequered with lurid marks ;

LA W OF PROGRESSIVE COLOURA TION. 57

but it often reverts to white or even to a faint yellow.
In Scilla, however, including our common wild hya-
cinth (S. nutans), the deep tubular flowers, composed
of perianth pieces with long claws, are usually blue,
rarely pink or white ; while in Hyacinthus and Mus-
cari, which have a united bell-shaped or globular
blossom, formed by the coalescence of the sepals and
petals, dark-blue and ultramarine are the prevalent

FIG. 20. — Flowers of simplest typical lily (Gagta lutea) ; primitive yellow.

tones. Meadow saffron (Colchicum autumnale), which
has also a united tube and very deep underground
ovary, is a fine reddish purple : its stamens secrete
honey.

The Iridece and Amaryllidece are more advanced
than the lilies, in that they possess inferior ovaries —
in other words, their perianth tube has coalesced with
the walls of the inclosed carpels. In many cases,

THE COLOURS OF FLOWERS.

especially in the more highly-developed species, their
flowers are red, blue, or purple. Trichonema Bulbo-
codium is purplish-blue with a yellow centre. Our
two native crocuses (C. vernus and C. nudiflorus] are
also purple. Sisyrinchium Bermudianum is a delicate
blue. Gladiolus communis is brilliant crimson. Iris
fcetidissima (Fig. 22) is violet. Our own Amaryllids
are white or primrose, but brilliant reds and purples,

FIG. 2i.— Fbwer of fritillary (Fritillaria Meleagris); purple, spotted with white.

as well as highly-developed spotted types, are common
amongst the cultivated exotics.

The OrchidacecB stand at the head of the entomo-
philous Monocotyledons by virtue of their inferior
ovary, their irregular flowers, and their extraordinary
adaptations to insect fertilization. Purples are the
prevailing ground-tones ; but in the commonness of
variegation and of specialized lines or spots of colour
the Orchids answer closely to the Scrophularinem

LA W OF PROGRESSIVE COLOURA TION. 59

among Dicotyledons, and may therefore best be con-
sidered in the succeeding chapter.

This brief review of the chief families of English
entomophilous flowers will probably have made clear
the general truth of the law of progressive coloura-
tion here laid down. There are many exceptions and
special peculiarities, some of which will be explained

FIG 22. — Flower of common flag (Irisfcetidisshna) ; violet blue.

or accounted for in the sequel ; but on the whole we
may consider the following facts fairly proved :—

(i.) Most of the very simplest flowers are yellow.
(2.) Many of the simpler flowers in each family

(except the highest) are apt to be yellow.
(3.) The more advanced members of very simple
families are usually white or pink.

60 THE COLOURS OF FLOWERS.

(4.) The simpler members of slightly advanced

families are usually white or pink.
(5.) The most advanced members of all families

are usually red, purple, or blue.
(6.) Almost all the members of the most advanced

families are purple or blue.
(7.) The most advanced members of the most

advanced families are almost always blue,

unless spotted or variegated.

CHAPTER III.

VARIEGATION.

So far we have spoken for the most part only of
what ladies would call self-colour, as though every
flower were of one unvaried hue throughout. We
must now add a few considerations on the subject of
the spots and lines which so often variegate the
petals in certain species. In this connection, again,
Mr. Wallace's hint is full of meaning. Everywhere
in nature, he points out, spots and eyes of colour
appear on the most highly-modified parts, and this
rule applies most noticeably to the case of petals.
Simple regular flowers, like the buttercups and roses,
hardly ever have any spots or lines ; but in very
modified forms like the labiates and the orchids they
are extremely common. The scrophularineous family,
to which the snap-dragon belongs, is one most specially
adapted to insects, and even more irregular than that
of the labiates ; and here we find the most singular
effects produced by dappling and mixture of colours.
The simple yellow mullein, it is true, has few such
spots or lines, nor have even many of the much higher
blue veronicas ; but in the snapdragons, the foxglove,
the toadflax, the ivy-linaria, the eyebright, and the cal-

62 THE COLOURS OF FLOWERS.

ceolarias, the intimate mixture of colours is very notice-
able. In the allied tropical Bignonias and Gloxinias
we see much the same distribution of hues. Many
of the family are cultivated in gardens on account of
their bizarre and fantastic shapes and colours. As to
the orchids, it is hardly necessary to say anything
about their wonderfully spotted and variegated flowers.
Even in our small English kinds the dappling is
extremely marked, especially upon the expanded and
profoundly modified lower lip ; but in the larger
tropical varieties the patterns are often quaint and
even startling in their extraordinary richness of fancy
and apparent capriciousness of design. Mr. Darwin
has shown that their adaptations to insects are more
intimate and more marvellous than those of any other
flowers whatsoever.

Structurally speaking, the spots and lines on petals
seem to be the direct result of high modification ; but
functionally, as Sprengel long ago pointed out, they
act as honey-guides, and for this purpose they have
no doubt undergone special selection by the proper
insects. The case is just analogous to that of the
peacock's plumes or the wings of butterflies. In
either instance, the spots and eye-marks tend to
appear on the most highly-modified surfaces ; but
they are perpetuated and intensified by special selec-
tive action. Among birds and insects, sexual selection
performs the work of fixing the colours ; among
flowers, the visits of bees and butterflies effect the
same end. Lines are comparatively rare on regular
flowers, but they tend to appear as soon as the flower
becomes even slightly bilateral, and they point directly
towards the nectaries. Hence they cannot be mere

VARIEGATION. 63

purposeless products of special modification ; they
clearly subserve a function in the economy of the
plant, and that function is the direction of the
insect towards the proper place for effecting the
fertilization of the ovary. In the common rhodo-
dendron, the connection can be most readily observed
with the naked eye, and the honey tested by the
tongue. In this case, one lobe of the corolla secretes
a very large drop of nectar in a fold near its base,
and the lines of dark spots appear on this lobe alone,
pointing directly towards the nectariferous surface.

The Geraniacece afford an excellent illustration of
the general principle. They are on the whole a com-
paratively high family of polypetals, for their ovary
tends to become compound and very complicated,
and they have many advanced devices for the disper-
sion of their seeds. Oxalis corniculata, our simplest
English form, is pale yellow : O. acetosella is white,
with a yellow base, and its veins are delicately tinged
with lilac. The flowers of Er odium and Geranium,
which are much more advanced, are generally pink
or purplish, often marked with paler or darker lines.
For the most part, however, these regular forms are
fairly uniform in hue ; but many of the South African
Pelargoniums, cultivated in gardens and hot-houses,
are slightly bilateral, the two upper petals standing
off from the three lower ones ; and these two become
at once marked with dark lines, which are in some
cases scarcely visible, and in others fairly pronounced.
From this simple beginning one can trace a gradual
progress in heterogeneity of colouring, till at last the
most developed bilateral forms have the two upper
petals of quite a different hue from the three lower

64 THE COLOURS OF FLOWERS.

ones, besides being deeply marked with belts and spots
of dappled colour. In the allied Tropceohim (Fig. 23) or
Indian cress (the so-called nasturtium of old-fashioned
gardens — though the plant is really no more related
to the water-cress and other true nasturtiums than we
ourselves are to the great kangaroo) this tendency is
carried still further. Here, the calyx is prolonged
into a deep spur, containing the honey, inaccessible to
any but a few large insects ; and towards this spur all
the lines on the petals converge. Sir John Lubbock

FIG. 23.— Flower of Indian cress (Tropceolnm maj'us). with one sepal prolonged into
a honey-bearing spur ; orange and yellow.

observes that without such conventional marks to
guide them, bees would waste a great deal of time in
bungling about the mouths of flowers ; for they are
helpless, blundering things at an emergency, and
never know their way twice to the same place if any
change has been made in the disposition of the
familiar surroundings.

The readiness with which the Geraniacecz pass into
irregular forms in Pelargonium and in the balsam
genus (Impatiens], in itself shows that they are a fairly
advanced family, and explains the common appear-

VARIEGATION. 65

ance of pink and purple petals among flowers which
at a casual glance seem scarcely so much modified as
the pinks or the crucifers.

The Malvacece are another family in which lines
and stripes commonly occur ; and they are shown to
be of a comparatively advanced type by their pecu-
liarly modified pistil, and by the union of their
stamens into a tube, to which the petals adhere at the
base. Lavatera arborea is purplish red \ of our three

FIG. 24 —Flower of pink (Dianthus) ; pink, with lighter spots.

Malvce, one, M. rotundifolia, is pale blue ; M. syl-
vestris is purple ; and M. moschata, rose-coloured, or,
rarely, white. All have strongly-marked lines, -and,
in addition to this, the vivid green calyx, seen through
the interstices of the petals, acts apparently as a
supplementary honey-guide. The same peculiarities
distinguish the genus Althcea, of which we have two
species, A.officinalis, pale rose-colour, and A. hirsuta,
purplish blue.

65 THE COLOURS OF FLOWERS

Among the very regular Caryophyllacece, the small,
open Alsine<z are never spotted or variegated ; and
even in the more developed Silenece, with their tubular
calyces, only the highest British genus, Dianthus
(Fig. 24), ever has marks on its petals.

In most regular flowers, the lines are mere intensi-
fications (or diminutions) of the general colouration
along the veins or ribs of the corolla ; and they
point towards the base or claw of the petal, where
the honey is usually secreted. But in irregular
flowers, we often get a higher modification of colour,
so that one region of the petal is yellow or white, while
another is pink or blue ; and these regions often run
transversely, not longitudinally. Such modifications
usually affect the most highly altered parts of the
irregular flower.

The common wild pansy, Viola tricolor, affords a
good example of complex variegation. Its flowers
are purple, white, or .yellow ; or have these pigments
variously intermixed. The two upper pairs of petals
are usually the most coloured ; the lower one is
broadest, and generally yellow at the base, with dark
lines leading toward the spur. Viola palustris ex-
hibits the same tendency in a less degree ; it is pale
blue, with purple streaks. V. canina has hardly more
than a few darker or lighter lines. The whole family
is immensely interesting from the 'present point of
view, and should be closely observed by the student
at first hand. Its changes and varieties will be found
full of instructive suggestions as to the origin and
nature of colour modifications.

\\±Polygala vulgarisfae two coloured petaloid sepals,
commonly called wings, are also delicately veined.

VARIEGATION. 67

Among the Papilionace<z> variegation and lines of
colour are common in the higher genera, which are
more strictly adapted to bees and other specialised
honey-suckers, such as Vicia, Lathyrus, Onobrychis, &c.
The standard is usually the most highly coloured ;
the wings and keel are generally paler, or one degree
lower in the scale of progressive colouration. In
Lathy rus hirsutus, L. silvestris, Vicia Bithynica, and
Astragalus alpinus, this peculiarity is well marked.
The cultivated sweet-pea, a Sicilian Lathyrus, illus-
trates the general principle even better than any of
our native kinds.

Among regular Corolliflorce, variegation is not very
common, though it occurs much oftener than in the
polypetalous classes, especially at the throat of the
tube, as in the forget-me-nots (Myosotis) ; but in irre-
gular Corolliflorce it is exceedingly frequent. The
Lentibulacece and 4 other small families afford several
examples. In the great order of Labiatcz, the highly
modified lower lip is very often spotted, especially
where it is most developed. This is the case in
S tacky s silvatica, Lamium purpureum, Galeopsis tetra-
Jiit, Calamintha acinos^ Nepeta cataria, N. glechoma,
Ajuga reptans, Scntellaria galericulata, and many other
species. Several exotic kinds show the same tendency
in a more marked degree.

The Scrophularinece, however, form perhaps the
best example of any. It was noticed above that
comparatively few of these are as blue or as purple
as might be expected from their high organisation,
The explanation is that they have mostly got beyond
the monochromatic stage altogether, and reached the
level of intense variegation. They are, in fact, a

F 2

68 THE COLOURS OF FLOWERS.

family with profoundly modified flowers (Fig. 25), most
of which are very specially adapted to very exceptional
modes of insect fertilisation. The Veronicas alone
among our English genera are simply blue, with
white or pink lines ; the others are mostly spotted or
dappled. Antirrhinum majus is purple, sometimes
crimson or white, with the curiously closed throat a
bright yellow. Linaria cymbalaria is blue or lilac,
with white patches, and the palate a delicate primrose.
L. spuria is yellow, with a purple throat. L. minor is
purple, with a white lower lip and yellow palate.

FIG. 25. — Flower of toad flax (Linaria vulgaris), with corolla prolonged into a
honey-bearing spur ; yellow, with orange palate.

The very strange flowers of Scrophularia have a
curious, indescribable mixture of brown, green, dingy
purple, and buff. Sibthorpia is pink, with the two
smaller lobes of the corolla yellow. Digitalis pur-
purea, the foxglove, is purple, spotted with red and
white. Euphrasia, eye-bright, is white or lilac, with
purple veins, and the middle lobe of the lower lip
yellow. Melampyrum arvense is red, with pink lips
and a purple throat. Description, indeed, is quite in-
adequate to convey any sufficient notion of the inti-
mate intermixture of hues in most scrophularineous

VARIEGATION.

69

plants. As a rule, the spots or patches of intrusive
colour are developed transversely near the palate or
around the throat. Purple, red, or blue appear to be
the prevalent ground-tones, with white and yellow
introduced as contrasted tints to heighten the effect
of the principal constructive parts.

Among Monocotyledons, such plants as the highly
modified Iris genus show similar results. Our own
I . fcetidissima has blue sepals, with yellow petals and

FIG 26.— Flower of spotted orchid (Orchi* tnaculiita) ; purple, dappled with pink
and white.

spathulate stigmas, all much veined. The Orchidacea
exhibit the same tendency far more markedly.
OrcJiis mascula, O. maculata, O. laxiflora, and many
other British species have the lip spotted (Fig. 26).
In O. militaris and O. hircina, the variegation is
even more conspicuous. In O. ustulata, the spots on
the lip are raised., The problematical bee-orchid,
Ophrys apifera, is singularly dappled on the lip and
disk, and has the sepals different in colour from the

70 THE COLOURS OF FLOWERS

rest of the flower. Aceras anthropophora, the man-
orchid, has green sepals and petals, edged with red,
and a yellow lip, pink fringed. Cypripedium calceolus,
the lady's slipper, Cephalanthera grandiflom, white
helleborine, and most other British species, are simi-
larly very diversified in colour. As to the exotic
species, some of them are more peculiarly tinted and
blended with half a dozen different hues than any
other forms of flowers in the whole world.

On the other hand, primitive yellow flowers of the
earliest type never have any lines or spots whatsoever.
We may therefore sum up the facts about variegation
as follows : —

(i.) Very simple and primitive flowers are usually
of one colour throughout.

(2.) Regular flowers of higher types are often
marked by lines of a different colour or shade, which
generally correspond with the venation of the petals.

(3.) Irregular flowers are often marked with distinct
patches of different colour (sometimes transverse),
which seem to act as honey-guides.

(4.) The most divergent colours usually appear on
the most highly modified parts of the flower.

CHAPTER IV.

RELAPSE AND RETROGRESSION.

FLOWERS which have reached a given stage in the
progressive scale of colouration often show a tendency
to fall back to a lower stage. When this tendency is
of the nature of a mere temporary reversion (that is
to say, when it affects only a few individuals, or a
casual variety), it may conveniently be described as
Relapse. When> however, it affects a whole species,
and becomes fixed in the species by a new and pre-
sumably lower adaptation, it may best be styled Retro-
gression. The difference between these two forms of
reversion will become clearer after we have examined
a few cases of each in detail.

Primary yellow flowers, like the buttercups, poten-
tillas, and St. John's worts, show little or no ten-
dency to vary in colour in a state of nature. They
have never passed through any earlier stage to which
they can revert ; and they are not likely to strike out
a new hue for themselves except through the action
of some special differentiating circumstances, such as
those ensured by cultivation.

Some white flowers, on the other hand, show a
decided tendency occasionally to revert to yellow,

72 THE COLOURS OF FLOWERS.

especially in the simpler orders. Erysimum orientale
varies from white to pale primrose. Raphanus ra-
phanistrum, as already noted, is usually even lilac,
often white, and on the sea-shore yellow. The
white cistuses often revert to a pale sallow tinge. In
some roses, the throat becomes yellow in certain
specimens. Many umbellates vary from white to a
faint yellowish green. In several other cases, stray
yellow specimens of normally white species are not
uncommon.

Pink and red flowers almost invariably revert in
many individuals to white. Indeed, there is probably
not a single blossom of these colours in England of
which white specimens may not occasionally be
gathered. A few typical instances must suffice. All
the British roses are reddish pink or white. So are
Saponaria officinalis, and many pinks. Malva moschata
runs from rose-coloured to white ; M. rotundifolia from
pale lilac-pink to whitish. Erodium cicutarium has
rosy or white petals ; all the geraniums occasionally
produce very pale flowers. White varieties of heaths
are frequent in the wild state. Where the red or
purple is very deeply engrained, however, as in
labiates, reversion to white occurs less commonly.
But almost all pink or red flowers become white with
the greatest readiness under cultivation.

Blue flowers in nearly every case produce abundant
red, pink, and white varieties in a state of nature. It
would seem, indeed, as though this highest develop-
ment of colour had not yet had time thoroughly to
fix itself in the constitution of most species. In an
immense number of cases, it still appears as a late
modification of red, the bud or young petals being

RELAPSE AND RETROGRESSION. 73

still of that colour, and only deepening into blue as
the flower opens. Hence individual reversion is here
almost universal as an occasional incident in every
species. The columbine (Aquilegia vulgaris] is blue
or dull purple, sometimes red or white. The larkspur
(Delphinium ajacis) often declines from blue to pink
or white. The monkshood (Aconitum napellus] is an
extremely deep blue, very rarely white. White violets
everybody knows well. The rampions (Phyteumd]
vary from blue to white ; so do many of the cam-
panulas. Gentiana campestris is sometimes white. In
most Boraginece — for example, in borage, viper's bu-
gloss, and forget-me-not — pink and white varieties are
common. Pink and white Veronicas also occur in
abundance among normally blue species. Prunella
vulgaris occasionally produces rosy or white blossoms.
White wild hyacinths are often gathered. Many
other cases will suggest themselves to every practical
botanist.

Blue flowers, however, very seldom revert to yellow,
though this change takes place in some cultivated
hyacinths, and somewhat differently in the pansy. As
a rule, the blue goes back only as far as those shades
from which it has more recently been developed.
This is, perhaps, the true rationale of De Candolle's
law of xanthic and cyanic types.

Sometimes, indeed, we may say that the new colour
has not yet begun to fix itself in the species, but that
the hue still varies under our very eyes. Of this the
little milkwort (Polygala vulgaris] affords an excel-
lent example, for it is occasionally white, usually pink,
and frequently blue. Here we may fairly regard
the pink as the normal hue, while the white is doubt-

74 THE COLOURS OF FLOWERS.

less due to reversion, and the blue to progressive
modification, not yet fully selected by insects ; so
that in all probability it is now actually in course of
acquiring a new colour. Much the same thing hap-
pens with the common pimpernel (Anagallis arvensis],
Its ancestral form is probably the woodland loose-
strife (Lysimachia nemorum), for though the capsule
of the pimpernel now opens transversely, it still retains
the five dark lines which mark the primitive dehis-
cence ; and in other respects it most closely resembles
Lysimachia^ which is a bright yellow. But pimpernel
itself is usually orange-red, while a blue variety is
frequent on the continent, and sometimes appears in
England as well. Every botanist can add half a
dozen equally good instances from his own memory.

Highly variegated flowers show the greatest ten-
dency of any to such occasional reversions, or, as it
is usually put, are extremely variable. The pansy
( Viola tricolor) is an excellent example. The snap-
dragons, orchids, and irises are also cases in point.

Indeed, the extent to which flowers are modifiable
in the hands of gardeners largely depends upon the
amount of modification which they have already
undergone in the natural condition. Very highly
developed plants have on the one hand acquired a
great constitutional plasticity of nature, and on the
other hand have a large number of previous stages to
fall back upon. Hence gardeners can do almost any-
thing they like with Dahlias, Cinerarias, Asters,
Chrysanthemums, and other advanced corymbiferous
composites; with Calceolarias, Antirrhinums, and
other Scrophularinece; with pansies, pea- flowers, heaths,
and lilies ; with exotic Gloxinias, Bignonias, Tecomas,

RELAPSE AND RETROGRESSION. 75

and Gesnenas.. On the other hand, variegated or
largely altered flowers of the simpler types rarely
occur even in cultivation. Hence we may, perhaps,
reasonably infer that great readiness to assume new
colours affords in itself a certain slight presumption
in favour of some previous colour modification. We
shall apply this hypothetical principle in the sequel to
sundry cases of yellow colouration in apparently high
families, as one among several tests by which we may
be aided in distinguishing retrograde from primitive
yellowness.

This seems also the proper place to consider "the
proofs of the position already advanced, that new
colours make their appearance at the edge of the
petal, and gradually work their way inward. Four
such proofs may be advanced. In the first place,
purely adventitious individual colours almost always
so appear. For example, the reddish tinge occa-
sionally observed on many yellow flowers is usually at
the tip : so is the lilac tinge on certain white anemones,
and the pink tinge on many crucifers and umbellates.
In the second place, the slight blush which occurs
normally on flowers like the daisy, the apple-blossom,
and the blackberry, and which appears to be as yet
comparatively uninfluenced by insect selection, seeing
that it is deepest on the back of the petals, generally
occurs near the tip. The same peculiarity may be
observed also in several small Caryophyllacece, Papi-
lionacece, and Ericacecs. In the third place, flowers
which open pink, like so many Boraginacece, and then
become blue, remain always red at the base, and only
acquire the new hue in the expanded limb of the corolla.
In tulips, Hydrangea, Richardia, &c , like facts occur.

76 THE COLOURS OF FLOWERS.

And in the fourth place, white varieties of blue flowers
usually have the centre bluish and the edge white ;
pink varieties have the centre bluish and the edge
pink, and so forth. Here, we know what the normal
colour is like, and can see that the new hue appears
first at the periphery. For example, white violets,
a variety of Viola odorata, have the spur and lower
part of the petals blue or bluish ; the whiteness only
extends to the broad part of the petals. In a large
number of varieties examined by the writer, the same
law holds good. Hence we are justified to some
extent in assuming that when a plant exhibits a
different colour at the base and at the tip of the
petal, the basal colour is probably more primitive
than the peripheral one.

If we turn from the white violet, with its blue spur,
to the very variegated pansy, we may perhaps ask
ourselves which is the earlier of its colours, the purple,
the white, or the yellow. But if we observe that the
spur, unseen at the back of the flower, is usually deep
violet blue, as are also the bases of the petals, while
the yellow is usually found on the most expanded
and modified part of the corolla, the lowest petal, and
in its most nodal or functionally attractive part, just
in front of the honey-cavity, we can hardly resist the
inference thrust upon us by analogy — that the pansy was
once all blue, and that the yellow has been developed
here, as in the snapdragon and the ivy-linaria, to guide
the bees to the proper place for securing the nectar
and effecting cross fertilisation.

It is an interesting fact in this connection that an
immense number of the very simplest flowers, when
not themselves yellow, have yellow spots or patches

P ELAPSE -AND RETROGRESSION.

at the bases of their petals. The reader is recom-
mended to notice this point for himself in the
commoner white or pink polypetalous flowers.

With the light thus cast upon the question to guide
us, we may pass on to the general consideration of
Retrogression in colours. Certain species of advanced
families have apparently found it advantageous in
certain circumstances regularly and consistently to
revert to colours lower in the scale than the normal hue
of their congeners. The reasons for such Retrogression
are often easy enough to understand.

We may take the evening campion (Lychnis vesper-
tina) as a good example (Fig. 15). This white flower,
as we saw, is evidently descended from the red day
campion (Lychnis diurna), because it is still often pale
pink, especially towards the centre, verging into white
at the edge. But it has found it convenient to attract
moths and be fertilised by them ; and so it has lost its
pinkness, because white is naturally the colour best
seen by crepuscular insects in the dusky light of
evening. It is scented at nightfall, and readily allures
many moths by the combined attraction of sight and
smell. Sir John Lubbock notes that such evening flowers
never have any spots or lines as honey-guides on the
petals, because such marks could not be seen at night,
and would therefore be useless. All the other British
species of Lychnis are red, pink, or purple.

The evening primrose ((Enothera biennis), now
naturalised in England, is another excellent instance
of the same sort. It belongs to the family of the
Onagracece, which are highly evolved polypetalous
plants, with the petals reduced to four or two in
number, and placed above instead of below the ovary.

78 THE COLOURS OF FLOWERS.

We should thus naturally expect them to be pink or
lilac, and this is actually the case with most of our
native species, the genus Epilobium having usually
purple or red flowers, rarely white ; while the smaller
Circ&as are pink or whitish. Why, then, is the even-
ing primrose yellow ? Because it is a night-flowering
plant, fragrant in the evening, and its pale yellow
colour makes it easily recognisable by moths. In this
case, however, two points mark it off at once from the
really primitive yellow flowers. In the first place, it
has not the bright golden petals of the buttercup, but
is rather more of a primrose tint ; and this is a
common distinguishing trait of the later acquired
yellows. In the second place, it belongs to a genus
in which red and purple flowers are common, whereas
the buttercups are almost all yellow or whitey-yellow,
and the potentillas mostly yellow or white, In short,
primitive yellow flowers are usually golden, and belong
to mainly yellow groups : reverted yellow flowers are
often primrose, orange, or dull buff, and occur
sporadically among blue, red, or purple groups.

There are other cases less immediately apparent than
these. For instance, Lamium galeobdolon, a common
English labiate, belonging to a usually purple or blue
family, is bright yellow. But we can form some idea
of how such changes take place if we look at the
pansy, which we have seen reason to believe is
normally violet-purple, but which usually has a yellow
patch on the lowest petal. In the pansy's var. lutea,
the yellow extends over the whole flower, no doubt
because this incipient form has succeeded in attract-
ing some special insect, or else grows in situations
where yellow proves more conspicuous to bees than

RELAPSE AND RETROGRESSION. 79

blue or purple. So, again, another English labiate,
Galeopsis tetrahit, the hemp-nettle, has a pale purple or
white corolla, sometimes with a tinge of yellow in the
throat : and in the var. versicolor, the yellow spreads
over all the flower, except a purple patch on the
lower lip. In G. ochroleuca, the whole corolla has
become pure yellow. In this way, one can under-
stand the occurrence of such a flower as Lamium
galeobdolon, especially since an allied species, L. album,
is white, and all the genus is extremely variable in
colour. Indeed, it is to be noted that the yellow
labiates do not commonly occur among the less
developed thymes, mints, and marjorams, but among
the extremely specialised Stachydece, which have very
modified flowers, and usually variegated or spotted
lips. They seem to be essentially reversionary forms
from purple or blue species, spotted with yellow.
Nay, the lower lip of L. galeobdolon itself still shows
marks of dark orange variegation, exactly answering
to that of several purple Lamiums : and the base of
the corolla tube is still pink or purplish.

Another hint of Retrogression is given us by flowers
like our English balsams, Impatiens noli-me-tangere
and /. fulva, in the fact that their yellow is generally
dappled with numerous spots of deeper colour. The
balsams are highly modified irregular Geraniacece,
sepals and petals being both coloured : and at first
sight it seems curious that our species should be
yellow, while the simpler Geraniums and Erodiums
are pink or red. But the genus as a whole contains
many red and variegated species, and alters in colour
with much plasticity under the hands of gardeners.
/. noli-me-tangere is pale yellow spotted with red :

80 THE COLOURS OF FLOWERS.

/, fulva is orange, dappled with deep brown. Both
are almost certainly products of retrogressive
selection.

Something of the same sort is seen in Cheiranthus
cheiri, the wallflower. This large and highly de-
veloped stock-like crucifer is a peculiar yellowish
brown in the wild state, frequently even primrose or
primitive yellow. But it varies readily, often be-
coming red at the edges ; and under cultivation it
assumes numerous shades of red, purple, and brown.
It appears to be a product of retrogressive selection
from an original form like the European stock. This
flower, combined with some others like Adonis
autumnalis, Ranunculus Ficaria, and Lotus corniculatus,
seems to suggest the idea that yellow may sometimes
merge directly into red, without passing through the
intermediate stages of white and pink. The other order
would appear, however, to be the more regular and
usual gradation.

In the Primulacece, we find similar instances.
Hottonia palustris, a less developed form, is rosy
lilac. Cyclamen europaum is white or rose-coloured.
Trientalis europcea is white or pale pink, wjth a yellow
ring. From such a stage as this, it is easy to get at
our primroses, cowslips, and oxlips, which have pale
yellow corollas, with orange spots at the throat.
Indeed, one English species, Primula farinosa, is
pale-lilac, with a yellow centre : and this might easily,
under special circumstances, become pale primrose all
over. The cultivated varieties of the cowslip, called
Polyanthuses, readily assume various tints of orange,
red, and pink, always at the edge, the deep yellow
of the throat remaining unchanged. On the other

RELAPSE AND RETROGRESSION. 81

hand, the yellow of the allied Lysimachias certainly
appears to be primitive.

Among heaths, our only yellowish sort is the
very degraded Monotropa, a leafless saprophyte of
the lowest type, obviously a product of extreme
Retrogression.

The colours of many Scrophularine<z may be ex-
plained in the same way. Perhaps the yellow of the
mulleins is primitive ; but as some species are white or
purple, it is just as likely to be retrogressive. In
Linaria, we may almost be sure that retrogression has
taken place ; for we can trace a regular gradation from
lilac flowers with a yellow palate, like L. cymbalaria,
to pale yellow flowers, like L. vulgaris (Fig. 25), which
has the mass of the corolla primrose, and the palate
orange. Mimulus luteus is also yellow, but it is usually
marked inside with small purple spots, and sometimes
has a large pink or red patch upon each lobe. In
Melampyrum cristatum, the yellow corolla is variegated
with purple : in M. pratense, it has the lip deeper in
hue. All these genera include many purple and
variegated species ; and the yellow members almost
always bear evident marks of being descended from
polychromatic ancestors.

Among Lentibulacea, our debased Utricularice have
pale yellow flowers ; but Pinguicula vulgaris is bluish
purple, and Pinguicula lusitanica yellow, tinged with
lilac : so that here, too, we may suspect Retrogression.

The case of the yellow Composites, especially the
Ligulatce, is more difficult to decide. It would seem
as though these plants, which have all their florets ligu-
late (Fig. 27), must be more highly developed than the
Corymbiferce, which have only the ray-florets ligulate,

G

82 THE COLOURS OF FLOWERS.

or than the Cynaroidece, which have no ligulate florets
at all. Hence we should naturally expect them to be
blue or purple, whereas they are for the most part
yellow of a very primitive golden type, while the
ray- florets of the Corymbifers are usually white or
pink, and all the florets of the Cynaroids are usually
purple. It is, of course, quite possible that a flower
might have progressed as far as the Corollifloral stage
— might have joined all its petals into a united corolla
under the influence of insect selection — and yet might

FIG. 27. — Vertical section of head of typical ligulate ; yellovr.

never have got beyond its primitive golden-yellow
colouration. Something of the sort may be the
case with Chlora perfoliata among the Gentianacece ; it
may even be the case with the Lysimackia genus
among the Primulacece ; and therefore it may also have
been the case with the primordial ancestor of the
Composites. But there are great difficulties in the way
of this explanation. In the first place, it would be
hard on that supposition to understand why the less-
developed Cynaroids should have outstripped the
more-developed Corymbifers and the most-developed

RELAPSE AND RETROGRESSION. 83

Ligulates. In the second place, it would be equally
hard to understand why the most primitive
Corymbifers, such as Eupatorium, should have
purple or white florets, while the more developed
genera, such as Aster and Chrysanthemum, should
have most of them yellow. The following hypothetical
explanation is suggested as a possible way out of this
difficulty.

The primitive ancestral composite had reached the
stage of blue or purple flowers while it was still at a
level of development corresponding to that of the
scabious or the Jasione. The universality of such
colours among the closely allied Dipsacecz, Valerainecz,
Lobeliacece, and Campanulacecz, adds strength to this
supposition. The central and most primitive group
of composites, the Cynaroids, has kept up the
original colouration to the present day ; it includes
most of the largest forms, such as the artichoke, and
it depends most of any for fertilisation upon the
higher insects. Very few of its members have very
small florets. All our British species (except the
degenerate Carlina) are purple, sometimes reverting
to pale pink or white, while Centaurea cyanus, our
most advanced representative of the tribe, rises even
to bright blue.

Next to the Cynaroids in order of development
come the Corymbifers, some of which have begun to
develop outer ligulate rays. Here the least evolved
type, Eupatorium, with few and relatively large
florets, is usually purple or white, never yellow. But
as the florets grew smaller, and began to bid for the
favour of many miscellaneous small insects, reversion
to yellow became general. In a few cases here and

G 2

84 THE COLOURS OF FLOWERS.

there we still find purple or white central florets, as in
Petasites vulgaris, the butter-bur ; but even then we
get closely related forms, like Tussilago farfara, colts-
foot, which have declined to yellow. The smallest and
most debased species, such as Solidago virga-aurea,
golden rod, Tanacetum vulgare, tansy, and Senecto
vulgaris y groundsel, have all their florets yellow and
similar ; unless, indeed, like Gnaphaliiim and Filago,
cud-weed, Artemisia absinthium, wormwood, or Xan~
thium strumarium, burweed, they have declined as
far as colourless or green florets, in which case they
must be considered under our next head, that of
Degeneration. On the other hand, the larger and
better types of Corymbifers began a fresh progressive
development of their own. In many Senecios, Inulas,
Chrysanthemums , they produced yellow ray florets,
similar in colour to those of the disk. In Chrysan-
themum leucanthemum, Anthemis cotula, Matricaria
inodora, &c., these rays, under the influence of a
different type of insect selection, became white. In
the daisy they begin to show signs of pink, and
in the Asters, Cinerarias, &c., they have become lilac,
purple, and blue. Complicated as these changes
seem, they must yet have taken place two or three
times separately in various groups of Corymbifers,
for example in the Asteroidece, the Anthemidea, and
the Senecionida.

The Ligulates were again developed from yellow-
rayed Corymbifers by the conversion of all the disk
florets into rays. Appealing for the most part to
very large and varied classes of miscellaneous insects,
they have usually kept their yellow colour ; but in a
few cases a fresh progressive development has been

RELAPSE AND RETROGRESSION. 85

set up, producing the violet-blue or purple florets of
the salsify (Tragopogon porrifolius}, the deep blue
Sonchus alpinus, and the bright mauve succory,
Cichorium intybus. As a whole, however, the Ligu-
lates are characterised by what seems a primitive
golden yellow, only occasionally rising to orange-red
or primrose in a few hawkweeds.

That this hypothetical explanation may be the
true one seems more probable when we examine the
somewhat similar case of the Stellatce. Here it seems
pretty clear that mere dwarfing of the flowers, by
throwing them back upon earlier types of insect
fertilisation, has a tendency to produce retrogression
in colour. Even in the more closely allied Dipsacece,
Valerianea, and Campanulacece, we see a step taken
in the same direction, for while the large-flowered
Campanulas and Scabiosas are bright blue, the smaller
flowered teasel (Dipsacus silvestris) is pale lilac, the
Valerianas are almost white, and the V aleriandlas
are often all but colourless. In the Stellatcz, the
same tendency is carried even further. As a whole,
these small creeping weeds of the temperate regions
form a divergent group of the tropical Rubiacecz (in-
cluding Cinc/wniacece), from which they are clearly
derived as a degraded or dwarfed sub-order. Their
square stems, their leaf-like interpetiolar stipules, and
their usually lessened number of corolla-lobes, all
point them out as derivative forms, not as survivals
from an early ancestral type. Now, the tropical
Rubiacecz have tubular blossoms with long throats,
and as a rule with five lobes to the corolla ; but many
of the Stellates have lost the tube and one corolla
lobe. Sherardia arvensis, which has departed least

86 THE COLOURS OF FLOWERS.

of our British species from the norma of the race, has
a distinct tube to the corolla, and is blue or pink,
Asperula, which approaches nearer to the retrograde
Galiums, has one pale lilac species and one white.
The Galiums have no corolla-tube at all, and most of
them are white ; but two British species, G. verum and
G. cruciata, are yellow, and one of these has become
practically almost bi-sexual — a common mark of
Retrogression. Rubia peregrina is even green. This
clearly marked instance of Retrogression from blue
through lilac and white to yellow makes the case of
the Composites easier to understand. No doubt the
dwarfed northern Stellates have found that they suc-
ceeded better by adapting themselves to the numerous
small insects of the fields and hedgerows, and there-
fore have fallen back upon the neutral colours, white
and yellow.

Something the same explanation may be hazarded
in the case of the Umbelliferce, a difficult family to
deal with satisfactorily. It would be rash to assert
that these curious flowers are descended from mono-
petalous ancestors, yet, with the analogy of Galium
before our eyes, a suggestion to that effect may at
least be entertained as possible. The relations of the
Umbellifera with the Araliacece and Cornea are very
close ; and it is difficult to believe that the last named
family at least are not truly monopetalous. From
the Rubiacecz, indeed, a regular line of affinities leads
us on through Caprifoliacecz and Cornea to Umbelli-
fera ; and if we allow that Galium is descended from
a tubular form like Sherardia it is hard to draw a line
at such types as the elder, the wayfaring tree, the
dogwood, or the ivy, till we arrive at the true

RELAPSE AND RETROGRESSION. 87

umbellates themselves. Be this as it may, the family
is one which clearly lays itself out to attract a large
number of miscellaneous insects, as Miiller has shown ;
and its prevailing colours are white and pale yellowish
green. The flowers are all adapted to such small
visitors as prefer these hues.

" The position of the honey on a flat disk," says
Sir John Lubbock, " which renders it accessible to
most insects, has the opposite result as regards the
Lepidoptera, which therefore, as might naturally be
expected, are but rare visitors of the Umbellifercz.
I have sometimes wondered whether the neutral tints
of these flowers have any connection with the number
of species by which they are frequented." This
pregnant hint is full of meaning for the student of
floral colouration.

After so many instances of more or less probable
Retrogression, it, will not surprise the reader to learn
that in an immense number of other cases there is
good reason to suspect some small amount of dwarf-
ing or even Degeneration. These cases might perhaps
be properly treated in the next chapter ; but their con-
nection with our present subject is so close that they
fall into place more naturally here. It may have struck
the reader, for example, when we were dealing with the
Crucifers, that many of the smaller white forms were
apparently lower in type than large and brilliant
yellow flowers like the charlocks. That is quite
true ; but then, many of these small types are de-
monstrably dwarfed and slightly degraded, as, for
example, Cardamine hirsuta, which has usually only
four stamens instead of six, thus losing the most
characteristic mark of its family. In Senebiera didyma,

88 THE COLOURS OF FLOWERS.

the petals have generally become quite obsolete ; in
some species of Lepidium,Arabis, Draba, &c., they are
inconspicuous and often wanting. So in the smaller
Alsinece there are many signs of Degeneration. The
normal forms of Caryophyllacece have two whorls of
five stamens each ; but these little creeping or weedy
forms have often only one whorl, as in Holosteum,
some Cerastiums, the smaller Stellarias, Spergula,
Polycarpon, &c. In Sagina, Cherleria, and other very
small types, the petals are often or always wanting.
Indeed, most botanists will probably allow that nearly
all our minute- flowered species, such as Montia
fontana, Claytonia perfoliata, Elatine hexandra, Radiola
Millegrana, Circ&a lutetiana, Ludwigia pains tr is,
Peplis Portula, Till&a muscosa, Myriophyllum spicatum,
Hippuris vulgaris, Centunculus minimus ', and Cicendia
pusilla, are distinctly degenerate forms. Though ob-
viously descended from petaliferous ancestors, and
closely allied with petaliferous genera or species,
many of them have lost their petals altogether, while
others have them extremely reduced in size. In
several cases, too, the number of sepals, petals, or
stamens has been lessened, and the plant as a whole
has suffered structural degradations. Most of these
dwarfed and degenerate flowers, if they have petals
at all, have them white or very pale pink.

Readers of Sir John Lubbock's admirable little
book on British Wild-Flowers in Relation to Insects
will readily understand the reason for this change.
They will remember that white flowers, as a rule,
appeal to an exceptionally large circle of insect
visitors, mostly of small and low grades. Hence,
some among these very small flowers may often

RELAPSE AND RETROGRESSION. 89

succeed, in certain positions, better than larger ones.
Moreover, they will recollect that in numerous in-
stances the larger blossoms of each family are so
exclusively adapted to insect fertilisation that they
cannot fertilise themselves ; while among the smaller
blossoms alternative devices for self-fertilisation com-
mcfnly come into play after the flower has been open
for some time, if it has not first been cross-fertilised.
Structural considerations show us that in most such
instances the larger and purely entomophilous flowers
are the more primitive, while the smaller and occa-
sionally self-fertilising flowers are derivative and
degraded, having usually lost some of their parts.
Hence, in tracing the progressive law of colouration
in the families generally, it is necessary, for the most
part, to consider only the larger and more typical
species, setting aside most of the smaller as products
of degeneration.

Moreover, as Mr. Henslow has shown, a large
number of minute species have fallen back almost
entirely upon self-fertilisation ; and these, we must
presume, when they retain their petals at all, retain
them either by mere hereditary habit, as functionless
relics, or else use them to effect an occasional cross
at long intervals. Such degenerate and dwarfed
species survive exactly as mites and other degraded
forms survive in the animal world — because they fill
certain holes and corners of the organic system better
than more highly developed forms could do. The
advantages of cross-fertilisation are seen in the large
stature and vigorous constitution of the truly en-
tomophilous or anemophilous plants, which have

90 THE COLOURS OF FLOWERS.

usurped all the best and richest places in nature,
like dominant races that they are ; the small de-
graded types are the species that have fallen behind
in the struggle, and manage merely to eke out a
precarious existence in the back slums of nature's
economy.

CHAPTER V.

DEGENERATION.

THE cases detailed in the last chapter lead us
gradually up to the consideration of those very
degenerate flowers whose structure has become com-
pletely debased, and especially of those which have
green perianths instead of coloured corollas. As a
rule, evolutionists have taken it for granted that
green flowers were the earliest of any, and that
from them the coloured types have been derived
by insect selection. But if the principles laid down
so far in this little treatise be correct, then it is
obvious that, since all petals were originally yellow,
green petals must be degraded, or at least altered
types. Of course, the flowers of gymnosperms (in
their blossoming stage) are mostly composed of green
scales or leaves ; and so it no doubt remains true
that all flowers are ultimately descended from green,
or greenish, ancestors. But if petals are by origin
modified stamens, it will follow that all corollas at
least were once coloured ; and we shall probably see
reason in the sequel to extend the principle to all
perianths whatsoever. Without insisting upon the
rule too dogmatically, so as to embrace every kind

92 THE COLOURS OF FLOWERS.

of angiosperm, we may, with some confidence, assert
that wherever a flower possesses a rudiment of a
perianth in any form, it is descended from coloured
and entomophilous ancestors.

Those who have read Professor Ray Lankester's
able little work on Degeneration will not be surprised
to find that this retrograde agency has played as
large a part in the vegetable as in the animal world.
We will begin by examining some of the most certain
cases, and then will proceed to those in which the
evidence is more remote, and the traces of the original
petaliferous structure more completely obliterated.

The Composites are, perhaps, in some respects, the
very highest family of entomophilous flowers now
existing on the earth. Their very structure implies
the long and active co-operation of insect fertilisers.
They could not otherwise have acquired the tubular
form, the united corolla, the sheathed anthers, the
compound heads of many-clustered florets. That
originally green flowers could attain to this stage of
development, and yet remain green, is simply incon-
ceivable. But the Composites contain also some of
the most degraded flower types in all nature. Be-
ginning with such forms as the common groundsel
(Senecio vulgaris), which has an inconspicuous yellow
rayless head, specially adapted to self-fertilisation,
we go on to plants like the Artemisias, with small
greenish florets, which have taken, or are taking, to
wind-fertilisation. Still more degraded are the Gna-
phaliums, Filagos, and Antennarias, whose mode of
fertilisation is problematical. And at the very bottom
of the scale we get the little green Xanthium ; so
degenerate a form that its connection with the other

DEGENERATION. 93

Composites can only be traced by means of several
intermediate exotics, in every stage of progressive
degradation. Such conclusive examples clearly show
us that green flowers may occur as products of degra-
dation even in the most advanced families.

Adoxa moschatellina is another excellent specimen
of a green corollifloral blossom. This pretty little
plant is closely allied to the honeysuckles and ivies ;
but it has somehow acquired a light green corolla, in
place of a white or pink one. It is still entomophi-
lous, and scantily secretes honey, so that the reason
of the change cannot be immediately pointed out.
Perhaps its very inconspicuousness saves it from the
obtrusive visits of undesirable insect guests. The
flowers of Hedera helix, common ivy, are also yel-
lowish green. In the allied family of Umbelliferce
many flowers have declined to similar greenish tints ;
but this can hardly be their primitive colour, as they
have an inferior ovary, which marks high develop-
ment, even if they are not, as suggested, degenerate
gamopetalous forms. Smyrnium olusatrum in this
family, and Chrysosplenium among the Saxifragacece,
exhibit very well the steps by which green corollas or
perianths may be produced from originally white or
yellow flowers. Rubia peregrina (wild madder) has
also greenish monopetalous blossoms. All these are
entomophilous. Their high structural development
obviously negatives the notion that they are primitive
green flowers ; and we must necessarily conclude that
they have become green for some special functional
purpose of their own.

Among the highly developed Ericacece, greenish
flowers occur in Pyrola, and to a less extent in

94 THE COLOURS OF FLOWERS.

Arbutus and Vaccinium. Pyrola, at least, is a
clearly degraded type.

The Orchids themselves, that most specialised of
entomophilous types, show us other examples of
flowers which have become more or less green ; such
as Malaxis paludosa, which has a yellowish tinge ;
Liparis loeselii, also yellowish ; Epipactis latifolia,
greenish brown ; Listera ovata, grass-green ; Habe-
naria viridis, yellowish green, and Herminium
monorchis, pale greenish yellow. Why these highly-
developed entomophilous blossoms should have found
green suit them better than white, pink, or purple, it
would be hard to say ; but the fact remains indis-
putable ; and it would be almost inconceivable that
flowers of so high a type should have remained green
all through the various stages of their long previous
development. We may confidently set them down
as products of incipient degeneration.

Among polypetalous flowers we get some equally
interesting facts. Green appears as a variegation-
colour on the highly-developed pea-flower, Lathy rus
silvestris, and some others. Helleborus viridis, a
doubtfully English ranunculaceous plant, has small
green petals, employed as nectaries, and concealed
by the large green sepals. It is entomophilous, and
much visited by insects. Instead of being one of
the least-developed RanunculacecEy however, it is one
of the most advanced and highly differentiated types.
In the lily family, again, the onion genus (A Ilium) is
a small, and often degraded, group, whose more retro-
grade members produce green in place of purple or
white flowers. In A Ilium vineale, and some others,
the flowers often degenerate so far as to become

DEGENERATION. 95

small caducous bulbs. Here, degeneration is the
only possible solution of the problem presented by
the facts.

More frequently, however, reversion to wind-ferti;
lisation (probably the primitive habit of all flowering
plants) has produced green blossoms among angio-
sperms. This may result in two or three distinct
ways. Either the corolla may become dwarfed and
inconspicuous, or it may coalesce with the sepals or
calyx-tube, or it may cease to be produced alto-
gether. We may take the plaintains (Plant ago} as
a good example of the first-named case. Here we
have tubular florets with four corolla-lobes, apparently
descended from some form not unlike Veronica (though
with four cells to the ovary) but immensely degraded.
The corolla is thin and scarious,. and its lobes are
tucked away at the sides, so as not to interfere with
the stamens and style. These, again, as in most
wind-fertilised plants, hang out freely to the breeze ;
so that the whole spike when flowering shows no
signs of a corolla from without, but seems to consist
entirely of scales, stamens, and styles, just like a
sedge or grass-plant. The expensive display of
petals is no longer useful to the plant, which, there-
fore, economises the material that would otherwise
be employed to allure the insects. It is impossible,
however, to examine the functionless corolla without
coming to the conclusion that Plantago must be de-
scended from an entomophilous ancestor. Indeed,
P. media still to some extent lays itself out to attract
small flies, by which it is even now often visited and
fertilised.

More degraded still is the allied Littorella, which

96 THE COLOURS OF FLOWERS.

leads on to the very degenerate types of water-
plants.

The Rosacece offer some good examples of green
flowers in which the petals have become quite extinct
Some of them are entomophilous, and some anemo-
philous. Alchemilla vulgaris (lady's mantle, Fig. 28)
is one of the former class. It is a degraded represen-
tative of the same group as agrimony ; but it has lost
its petals altogether. That it is a late, not a primitive

FIG. 28. — Flower of lady's mantle (Alchemilla), with double calyx, but no petals;

green.

form, is shown by its very reduced carpels, and its small
number of stamens. Alchemilla arvensis (parsley-
piert) is an extremely debased moss-like descendant
of some similar ancestor. It has tiny green petalless
axillary flowers, self-fertilised, but occasionally visited
by minute insects. Not far from these may be placed
Poterium sanguisorba (Fig. 29), another degraded
type, which has become anemophilous. This flower,
too, is green, and has no petals ; it usually possesses
but one carpel, and it is altogether a clearly

DEGENERATION. 97

debased bisexual form. Its stamens are numerous,
and they hang out to the wind, as do also the
feathery stigmas in the female flowers, to catch the
pollen from neighbouring heads. But the closely-
allied Sanguisorba officinalis (Fig. 30) is evidently
an entomophilous variation on the same ancestral
form ; for it resembles Poterium in every respect
except in its flowers, which have very few stamens,
enclosed in the purple calyx-tube. This interesting
case shows us that when a flower has once lost its

4'V4 "^*

F"jc. 29. — Flower of salad burnet FIG. 30. — Flower of great burnet (Satigui-
(Poterium sanguisorba) ; green sorba officinalis) ; purple and entomoplii-

and anemophilous. lous.

petals and become anemophilous, it cannot re-develop
them if it reverts to insect fertilisation, but must
acquire a coloured calyx instead. The same lesson
is perhaps elsewhere enforced by Glaux maritima
among the Primulacea, and by Clematis among the
Ranunculacece.

Mr. Darwin remarks that anemophilous flowers
never possess a gaily-coloured corolla. The reaspn
is clear. Such an adjunct could only result in the
attraction of stray insects, which would uselessly ea-t
up the pollen, and so do harm to the plant. Hence

H

98

THE COLOURS OF FLOWERS.

when flowers revert to wind-fertilisation, both disuse
and natural selection cause them to lose their petals,
and become simply green.

In practice, however, it is often hard to distinguish
between the casually entomophilous, the self-fertilised,
and the really anemophilous species ; and they are
so intermixed that it may perhaps be best to consider
them together. For example, the common ash (Fraxi-
nus excelsior, Fig. 31) belongs to a gamopetalous
family, the Oleacece, and is closely related to the white
privet (Ligustrum vulgare), which has conspicuous

FIG. 31.

-Hermaphrodite, male and female flowers of English ash (Fraxinus
excelsior); purplish— no petals.

white flowers. But many large trees, owing, perhaps,
to their long life, and consequent less necessity for
producing many seeds, tend to lose their petals ; and
this is remarkably the case among the olive group.
The shrubby species have usually flowers with a four-
lobed corolla ; and so have many of the southern ar-
boreal forms (Fig. 32) : but the northern trees, like our
ash, have lost both calyx and corolla altogether, each
naked flower consisting only of two stamens, with a
single ovary between them. In appearance their
blossoms seem of much the same sort as the wind-

DEGENERATION. 99

fertilised catkins and oak-kinds. Nevertheless, they
are entomophilous, for their pollen, their arrangement
in large masses, and their dark purple colour, suffi-
ciently serve to entice numerous insects.

The spurges (Euphorbiacece] are a very interesting
family of the same sort, exhibiting every gradation
from perfect corolliferous blossoms to the most de-
graded flowers in all nature. Our English species have
no true petals ; but some exotic forms are truly

FIG. 38. — Hermaphrodite perfect flower of South European flowering ash (Fraxinus
ornus) ; white, with four-lobed corolla.

dichlamydeous ; and from them we can trace a gradual
decline, through plants like dog's mercury (Figs. 33 and
34, Mercurialis perennis\ which has a green calyx, but
no corolla, to very degenerate green blossoms like our
own spurges (Euphorbia}, which consist of several ex-
tremely simplified flowers, collected together in a
common involucre (Fig. 35). Each separate male
floret is here reduced to a single stamen, raised on a
short peduncle, and with a distinct joint at the spot
where the petals once stood. It is worthy of notice,

H 2

100

THE COLOURS OF FLOWERS.

too, that when these degenerate, but still entomophilous,
green flowers have found it desirable to attract insects

FIG. 33. — Male flower of dog's mercury
(Mercurialis) \ green.

FIG. 34. — Female flower of dog's
mercury {M ercurialis) \ green.

by developing new coloured surfaces in place of the
lost corolla, they have not done so by producing a
fresh set of petals, but have acquired coloured bracts

FIG. 35. — Inflorescence of spurge (Euphorbia), the male flowers reduced to a single
stalked stamen, the female flowers to a naked ovary ; green.

or involucres instead, as in the well-known latrophas
and Poinsettias of our hot-houses. This instance is

DEGENERATION. 101

exactly analogous to that of the Sanguisorba, con-
sidered above. It tends to show that petals are not
developed from bracts, but from altered stamens.

From cases like these, we go down insensibly
through all the ranks of the dicotyledonous Mono-
chlamydce. In the Paronychiacece, for example, we
get an order closely allied to the Caryophyllacece
(especially to Polycarpon] ; and in one genus (Cor-
rigiola] the flowers have small white petals, which
certainly aid in attracting insects. But in Herniaria
the flowers are quite green, and the petals are re-
duced to five small filaments, thus partially reverting
to their presumed original character as stamens. In
Scleranthus the filaments are often wanting, and in
some exotic species altogether so. The A marantacece^
unrepresented in Britain, approach the last-named
family very nearly, but have the petals altogether
obsolete ; and in many cases, such as Prince's feather
(A waranthus hypochondriacus] and Love-lies-bleeding
(A. caudatus), the calyx becomes scarious and brightly
coloured. The Chenopodiacece are other near relations,
in which also the petals are quite obsolete ; and in most
of them the perianth (or calyx) is green. In Salicornia
it has become so embedded in the succulent leafless
stem as to be almost indistinguishable. The Poly-
gonacece, on the other hand, are a group of plants,
allied to Chenopodiacece y but with a row of degraded
petals, and a strong tendency to produce coloured
perianths, analogous to that which we observed in
Sanguisorba. The flowers of Rumex, the docks, are
sometimes green, sometimes red ; those of Polygonum
are pale-green, white, or pink. Rumex is sometimes,
Polygonum constantly, fertilised by insects.

102 THE COLOURS OF FLOWERS.

Submerged or floating plants especially tend as a rule
to become green-flowered, and to grow very degraded
in structure. As instances, we may take Myrio-
phyllum, Ceratophyllum, Elodea, Lemna, Callitriche,
Potamogeton, Ruppia, and Hippuris. In most of
these groups the proofs of great degeneration are
too obvious to need insisting upon.

There remain doubtful, then, among green Dico-
tyledons, only the highly anemophilous families, like
the nettles (Urticacece) , and the catkin-bearing trees
(Amentiferce]. The former have a well-developed
calyx, at least to the male flowers ; and it is difficult
to see how any one who compares them with Scleran-
thus or Mercurialis, known descendants of petaliferous
forms, can doubt that they too are degenerate types.
Indeed, the mere fact that the stamens are opposite to
the lobes of the calyx (Fig. 36), instead of alternate
with them, in itself shows that a petal-whorl has been
suppressed ; as is likewise the case in the goose-foots
and many other doubtful instances. Moreover, the
nettles are closely allied to the elms ( Ulmacetz), which
are obviously degenerate, and have acquired a coloured
perianth, side by side with their resumption of the
entomophilous habit.

As to the Amentiferce, Cupuliferce, and other catkin-
bearers, at first sight we might suppose them to be
primitive green anemophilous orders. But on closer
consideration, we may see grounds for believing that
they are really degenerate descendants of entomo-
philous plants. In the alder (Alnus) the male catkins
consist of clustered flowers, three together under a
bract, each containing a four-tobed perianth, with four
stamens within (Fig. 37). These little florets exactly

DEGENERA TION.

103

resemble, on a smaller scale, those of the nettle;
and the stamens here, again, are opposite to the
calyx-lobes, which of course implies the suppression

FIG. 36.— Male flower of nettle (Urtica dioica); green, with stamens opposite
the sepals.

of a corolla. In the beech (Betuld) the three florets
under each bract are loosely and irregularly arranged ;
and in the male hornbeam (Carpinus) and hazel (Cory-
/us) the perianth is wholly obsolete. All these are

FIG. 37.— Flowers of alder (A Inns); jrreen, with stamens opposite the sepals.

probably quite anemophilous. The willows (Salix),
on the other hand, though included by Sir John
Lubbock in the same category (doubtless through

104

THE COLOURS OF FLOWERS.

inadvertence) have really become once more ento-
mophilous ; and they are much visited by bees,
which obtain honey from the small glands between
the florets and the axis (Figs. 38 and 39). Degenerate
as these last-named species undoubtedly are, they
may be connected by a regular line of illustrative
examples (not genetically) through the beech, alden

FIG. 38.— Male flower of willow
(Salix)\ greenish.

FIG. 39 — Female flower of willow
(Salix); greenish.

nettle, goosefoot, Sclerantkus, Herniaria, and Corri-
giola, with such perfect petaliferous types as the pinks,
and ultimately the buttercups.

Among Monocotyledons, the very degraded little
entomophilous flowers of the Arum (Fig. 40), enclosed
in their green spathe, are often spoken of as though
they represented a primitive type. In reality, how-
ever, they are degenerate dichlamydeous blossoms,
linked to the lilies by Acorus (Fig. 41), which has
numerous hermaphrodite flowers, each with a perianth
of six scales, two rows of stamens, and a two-celled

DEGENEPA TION.

105

or three-celled ovary. Here, again, the green flower
is obviously of late date.

What, then, are we to say about the anemophilous
Monocotyledons, the great families of the sedges and
grasses ? Surely these, at least, are primitive green
wind-fertilised flowers. Dogmatically to assert the
contrary would, indeed, be rash with our existing

FIG. 40.— Spike or spadix of cuckoo-pint
(A rum maculatum), consisting of nu-
merous naked male,female, and neuter
flowers, in separate clusters ; purplish
green.

FIG. 41. — Single floret of sweet sedge
(Acorus), with six perianth pieces,
six stamens, and an ovary ; greenish
yellow.

knowledge ; yet we may see some reason for be-
lieving that even these highly anemophilous types
are degenerate descendants of showy petaliferous
blossoms. For, if the origin here assigned to petals
be correct, it becomes clear that the Juncacece, or
rushes, are only Liliacecs in which the perianth has
become dry and scarious ; for the absolute homology

io6 THE COLOURS OF FLOWERS.

of parts in the two orders cannot, of course, be
denied. Some rushes, such as Luzula, approach
very closely in general character to the grasses ;
and they also show themselves to be higher types
by the further development of the ovary, and the
decreased number of seeds. Eriocaulon and the
Restiacece give us a further step towards the grass-*
like or sedge-like character. Some of the Cyperacece
show apparent relics of a perianth in the bristles which
surround the ovary, especially in Scirpus (Fig. 42) ;

FIG. 42. — Flowei of a sedge (Scirpus). with six hypogynous bristles, representing the
calyx and corolla.

and perhaps the perigynium of Carex may represent
a tubular perianth, though this is far more doubtful.
In the grasses (Graminece) the perianth is either
altogether obsolete, or else is reduced to the paleae
with the hypogynous scales or lodicules (Fig. 43).
According to the most probable view (Fig. 44), the
two paleae represent the calyx (for the inner palea
exhibits rudiments of two sepals, thus making up,
with the outer palea, a single trinary whorl) ; while

DE 'GENERA 77(9. V. 1 07

the lodicules represent two of the petals, the third
(the inner one) being usually obsolete. It is fully
developed, however, in the bamboo. The connection
is here less clearly traceable than in the Amenti/erce,
but it is still quite distinct enough to suggest at
least the possibility that even grasses and sedges are
ultimately derived from entomophilous flowers.

There is, however, another and more powerful argu-
ment against the idea that any of these existing green

FIG. 43. — Flower of grass, showing two lodicnles or rudimentary petals three
stamens, and ovary with two styles. One petal and one style are abortive.

flowers are really primitive. For what are the known
marks of the most primitive existing flowers ? Nu-
merous simple superior carpels ; distinct flowers on
separate peduncles ; no specialised bracts, no heads,
no complications of any sort. And what are the
known marks of late and more developed or degraded
flowers ? Unification of the pistil by union or sup-
pression of the carpels ; grouping of flowers in heads ;
separation of sexes ; multiplication of accessory parts,

io8

THE COLOURS OF FLOWERS.

involucres, bracts, glumes, glands, awns, and so forth.
Now, to which of these classes do the yellow flowers
ordinarily belong ? Clearly to the first. To which
do the green flowers ordinarily belong ? Clearly to
the second. The organisation of the catkins, the
sedges, and the grasses is exactly analogous to that
of the spurges, which we know by an unbroken line
of intermediate links to be descended from petali-
ferous ancestors. The inference is almost irresistible

OJ?.

a,3.

FIG. 44 — Diagram of flower of grass, a, sepals ; a i, outer sepal, flowering glume,
or outer palea ; a 2 and a 3, inner sepals, combined into a single inner palea ;
b, petals ; b i and b 2, the lodicules ; b 3, suppressed ; c, stamens, all present ; d,
styles or stigmas; di and dz, present ; d 3, suppressed. The whole inner side
of the flower is thus abortive.

that so highly complicated a flower as that of the
grasses, with its one-celled, one-ovuled ovary, its two
styles, and its advanced paraphernalia of lodicules,
paleae, and glumes, arranged in long and subdivided
spikes, must be a very specialised or degenerate, not
a primitive or early type. The more closely we
examine green flowers, the more do we see that
they form the opposite pole to such simple and truly

DEGENERA TION. 1 09

primitive forms as the buttercups, the potentillas, the
Alismacecz, and the simpler lilies of the Gagea type.

Thus we are led, at last, to the somewhat unex-
pected conclusion that anemophilous angiosperms
are later in development than entomophilous angio-
sperms, and are derived from them. Though the
earliest flowering plants — the pines, cycads, and other
gymnosperms — were undoubtedly anemophilous from
the first, yet the probability seems to be that all
angiosperms were originally entomophilous, and that
certain degenerate types have taken later on either to
self-fertilisation, or to fertilisation by means of the
wind. Why this apparently retrograde change has
proved beneficial to them it would be impossible pro-
perly to inquire at the close of a work devoted to the
simple question of the colours of flowers. We must
content ourselves with noting that such degraded
green flowers fall for the most part under one or
other of four heads: (i) dwarfed or weedy forms;
(2) submerged or aquatic forms ; (3) forest trees ;
(4) grass-like or plaintain-like plants of the open
wind-swept plains. That there are no primitive
families of green or anemophilous angiosperms, it
might perhaps be rash and premature to assert ;
but at least we may assume as very probable the
principle that wherever green flowers possess any
perianth, or the relic or rudiment of any perianth,
or are genetically connected with perianth-bearing
allies, they have once possessed coloured insect-
attracting corollas. In short, green flowers seem
always (except in gymnosperms) to be the degene-
rate descendants of blue, yellow, white, or red ones.

CHAPTER VI.

MISCELLANEOUS.

A FEW general hints upon various side questions
may here be conveniently thrown together in con-
cluding our hasty survey. They must be accepted
in most cases merely as suggestions for observation
on the reader's own part. The subject is still a new
one, and only vague ideas can as yet in certain
directions be formulated upon it.

We have seen in several cases already that flowers
which have lost their corolla often tend to re-develop
brilliant colours in their calyx, as in Sanguisorba; while
flowers which have lost both corolla and calyx often
tend to re-develop such colours in bracts, involucres,
or leaves, as in latropha and Poinsettia. Among our
British Monochlamydce there are comparatively few
instances of such coloured calyxes, Glaux, Daphne
mezereum, and Ulmus, being our best examples ; but
in many well-known exotic species, such as Mirabilis
dichotoma, marvel of Peru, and the Begonias, the
calyx is quite as beautifully coloured as any corolla.
In Bougainvillea, three lilac bracts form the attractive
organ. In Aristolochia, the tubular calyx simulates
an irregular corolla, and in A. cordata it is large and

MISCELLANEO US. in

brilliantly scarlet. In Richardia africana, the so-
called Ethiopian lily, the spathe, surrounding a
spike of very degraded achlamydeous flowers, is
pure white, and very attractive. Amherstia nobilis,
Bromelia pinguin, several species of Salvia, and
many other exotics, have handsome bracts, which
add greatly to their beauty.

The fact that in such cases flowers do not develop
new petals from bracts or leaves, but acquire instead
coloured calyxes or involucres, goes to prove the
validity of the view with which we set out, that
petals are really altered stamens, not altered leaves
or sepals. For if they could once be developed from
leaves, there would be no reason why they should
not be developed from them here again. But if they
were developed from stamens, and then lost in these
instances, we could easily understand why the plant
could not afford to waste any more of its now
diminished number of stamens for purely attractive
purposes, and so was forced to pour the necessary
pigment for alluring insects into the other surround-
ing organs. In other words, on the Wolfian principle,
there would be no reason why flowers with petals
should not appear sporadically among monochlamy-
deous families ; on the principle here advocated, it is
quite clear why stray entomophilous species, de-
veloped from these degraded types, should have
coloured calyxes, instead of coloured petals.

Among highly-developed, or succulent plants, the
calyx and bracts often tend to assume colours like
those of the petals, as do also the peduncles and the
stem. Cases occur in Ajuga reptans, Echium, Sedum,
and RumeX) among British plants ; and more notice-

ii2 THE COLOURS OF FLOWERS.

ably in Peperomia, Echeveria, Epipkyllum, and other
exotics. The calyx and the expanded stipules which
cover the young flower- heads in red clover (Trifolium
pratense] and many other clovers, are delicately pink
or purple. In T. arvense the sepals are pale lilac,
and in T. incarnatum pale yellow. The whole upper
portion of the flowering stem in Chrysosplenium is
bright golden.

Where the calyx is largely exposed to view, as in
the globe-flower (Trollius), the columbine, the helle-
bores, and the monkshood, it is apt to become quite
as brilliant as the petals. In such cases its coloura-
tion usually follows the same law of progressive
development as the corolla. Sometimes, under these
circumstances, the now almost useless petals are
suppressed altogether, as in Caltka, a near relative
of Trollius, as well as in the Anemones and Clematis.
At other times they are utilised as nectaries, as
in columbine, hellebore, and monkshood. In the
meadow-rues (Thalictmm) the petals are suppressed,
and the sepals very small, so that the flower depends
for attractiveness almost entirely upon its clustered
yellow stamens. In Impatiens, Polygala, and some
other British genera, sepals and petals share almost
equally in the attractive display.

Where the petals have become much dwarfed, the
calyx is apt to aid them, if brilliant colouration again
becomes necessary. For example, our own wild
gooseberry, wild currant, and most other members
of the Ribes genus, have very inconspicuous petals ;
but in the North American scarlet Ribes of our
gardens {R. sanguineus), the flower has re-assumed a
brilliant colouring, and it has done so by making its

MIS CELL A NEO US. 1 1 3

calyx bright red, instead of by increasing the size
and deepening the hue of its small white petals. In
the Fuchsia, the Hydrangea, and many other well-
known exotics, we get exactly similar devices.

Parasites and saprophytes do not as a rule require
to produce green leaves ; hence, most of them, like
Cuscuta, Orobanche, Lathrcza, and Monotropa, have
the stem and leaves (or scales) coloured like the
flowers. Imperfect parasites which contain chloro-
phyll, however, have the leaves more or less green,
as in Viscuiftt Bartsia, Rhinanthus, and Melampyrum.

The outer florets of compound heads are apt to
produce larger petals than the inner ones, as in many
Umbellates (like cow-parsnip), the guelder-rose, the
Hydrangea, and the rayed forms of Composites. These
are obviously intended to increase the total attractive
effect. In the Umbellates and in candytuft the outer
petals of the individual flowers grow longer than the
inner ones.

Petals have perhaps been independently developed
from stamens at least twice over, once in the Dico-
tyledons, and once in the Monocotyledons. Insects,
having once learnt to visit coloured surfaces in search
of pollen and honey, would naturally tend to visit all
such surfaces in future, and thus to select for fertili-
sation any coloured flowers that offered them any
attraction in the way of food, of whatsoever sort.
Apparently, at last one species of gymnosperm, the
larch (Pinus larix), has thus become entomophilous,
its fertile scales being interspersed with bright pink
or red empty bracts, which seem to subserve an
attractive function. They are certainly visited by
insects, perhaps in search of some secretion from

I

ii4 THE COLOURS OF FLOWERS.

the bracts. This case may be looked upon as
analogous to those of the ripe cones in the juniper
and yew, which have similarly assumed the guise of
attractive fruits, eaten by birds, who disperse their
seeds. Such gymnosperms may be said metaphori-
cally to have taken a hint from the angiosperms
about them, and have acted upon it for their own
advantage.

It has .been assumed throughout that the progres-
sive modification of the colours of petals is due in
the main to increased oxidation of their contents. It
may be added here that the thin edges of the petals
where the newer colours usually first make their ap-
pearance, are the parts where oxidation would most
naturally take place. Hence, probably, the distinct
analogy between fading colours and progressive
colours. In most cases, colours appear most vividly
on the outside of the petals, where they were ex-
posed in the bud, and where oxidation would most
readily occur. The red tinge on the outside of
daisies, apple-blossom, &c., is here once more very
significant. In Convolvulus arvensis the mass of the
corolla is white ; but the lines exposed in the bud
are deep pink, evidently from oxidation ; and at the
same time they form excellent honey-guides of the
ordinary simpler sort. In many others of the same
genus a similar result may be observed. The under
side of the petals in St. John's worts, and the back
of the standard in Lotus, are frequently ruddy red.
The outer glumes of grasses are often purplish ; the
fruiting perianths of Rumex grow red as they ripen.
Put beside the rosy cheeks of peaches, apples, and
many other fruits, and the obvious oxidation colours

MISCELLANEOUS. 1 1 5

of injured parts and autumn leaves, these facts are
full of functional significance.

In a single flower, the common pink Phlox, a
change apparently takes place in the reverse order
to that laid down in this treatise as the general law,
for it presents early in the morning a light blue tint,
and retrogrades to pink as the sun advances in the
sky. But it has been suggested (quite apart from
our present theory) that the blue colour is due to the
presence of some substance which becomes blue by
non-elimination of oxygen during the night ; and as
the oxygen is given out during the day, the blue
colour disappears. If this theory be well founded,
the apparent exception really confirms our rule.

It has been objected by two or three authoritative
critics that the original petals need not necessarily
have been yellow, because they represent the flat-
tened filament, not the anthers ; and it is the pollen
that gives the ydlow colour to most stamens. But it
may be answered that in the primitive yellow flowers
(for example, the buttercups) the filaments are usually
of the same golden yellow as the petals ; and in many
other flowers they retain more or less of a yellowish
tinge. In white flowers they show a strong tendency
to become white ; but in pink and blue ones, pink
or blue filaments are comparatively rare. Sometimes,
indeed, the filaments become brightly coloured, so as
to share in the attractive display ; as a rule, however,
they are yellow in the yellow flowers, white or greenish-
yellow, with more or less of a pinky tinge, in almost
all others. The subject is certainly one which requires
further investigation.

According to Sachs, the yellow pigment of the

ii6 THE COLOURS OF FLOWERS.

flowers here described as primitive is usually identi-
cal in composition with the ordinary yellow chloro-
phyll of leaves, while the orange, pink, red, and blue
pigments are of more elaborate kinds.

If the botanical reader will provisionally accept the
principles laid down in this little book, and will then
test their validity by applying them to the flowers
which he meets in his daily walks, he will find that
many other confirmatory examples occur to him at
every step, most of which are too numerous to insert
here. He will also often find that close inspection
reveals some unexpected answer to a superficial
difficulty, some solution for the problem of an ap-
parent exception, which can only be obtained by
personal examination of the specimen with that
particular object held definitely in view. For ex-
ample, the case of the dead-nettle (Lamium album}
was cited above as one of a labiate grown white by
reversion (Fig. 45). This may have seemed at the
time a purely gratuitous and arbitrary supposition.
Why should not the white form be primitive, and the
purple or pink ones be derived from it ? But if
the flower of a dead-nettle be carefully examined,
it will be found in most cases to be not purely white,
but to have some dusky fines and markings on its
lower lip, of a pale brown or dim grey-black, which
exactly answer to those on the lip of L. maculatum,
and in a less degree of L, ptirpureum. Now, such
markings do not occur among original white flowers
like the crucifers and Caryophyllacece ; but they are
common on the lower lip of purple labiates. More-
over, we know that Lamium maculatum is very closely
allied to L. album, and that it is purple-red instead

MfSCELLANEO US. 1 1 7

of white. Both have the leaves occasionally marked
in the centre with a white line or spot, which is a
symptom of very close relationship. Indeed, Mr.
Bentham formerly united the two in a single species ;
and even now he is doubtful whether they should be
regarded as more than mere varieties. When we
consider that all purple labiates are liable to be
spotted with white ; that the purple and white forms
are here closely allied ; that in Galeopsis tetrahit we

.,„////*/, „.

FIG. 45.--Vertical section of dead-nettle (Lamiitni albutn~) \ white, with dark lines.

have a regular gradation from pure purple flowers to
almost pure yellow ones ; that in Lamium galeobdolon
we have a related yellow form similarly spotted ; that
all the Lamiums show a tendency to variegation ; and
that the white flower has itself an inconspicuous and
probably functionless variegation, where the purple
one has conspicuous and useful honey-guides, the
inference is almost irresistible that the common white
form, L. album, represents a retrogressive modification

1 1 8 THE COLO URS OF FLO WERS.

of the rarer and obsolescent purple form, L.
maculatum.

It would, of course, be impossible to treat every
similar instance at equal length without swelling this
volume to an unreasonable extent. But if the reader
will carefully examine, at first hand, all cases of what
seem to him adverse examples, he will usually find
some such hint of the true relation, surviving in the
flower itself. Excellent studies may thus be made of
Teucrium scorodonia, compared with our three other
British Teucriums (where the calyx suggests the rela-
tive stages of development) ; of Ajuga chamcepitys
with A. reptans ; of our three Melampyrums ; of
Rhinanthus and Pedicularis, and of the various
Linarias. The Orobanches are also full of instruc-
tiveness, as are likewise Pinguicula and Utricularia.
The descriptions given in Floras and other botanical
works, and even the best coloured plates, supply very
inadequate ideas of the minute observation involved
in the study of this subject from the evolutionary
point of view. Dried specimens are of course almost
useless. The investigation must be conducted upon
the living corolla in all stages of its development.
Those who will take the trouble thus to watch the
actual growing flowers for themselves will soon learn
to recognise many other little marks of relative pro-
gress or retrogression which cannot all be set down
definitely in black and white without unnecessary
and tedious prolixity.

If the general principle here put forward is true,
the special colours of different flowers are due to no
mere spontaneous accident, nay, even to no mean-
ingless caprice of the fertilising insects. They are

MfS CELL A NEO US. 119

due in their inception to a regular law of progressive
modification ; and they have been fixed and stereo-
typed in each species by the selective action of the
proper beetles, bees, moths, or butterflies. Not only
can we say why such a colour, once happening to
appear, has been favoured in the struggle for exist-
ence, but also why that colour should ever make its
appearance in the first place, which is a condition
precedent to its being favoured or selected at all.
For example, blue pigments are often found in the
most highly-developed flowers, because blue pigments
are apparently a natural product of high modification
— a simple chemical outcome of certain extremely
complex biological changes. On the other hand,
bees show a marked taste for blue, because blue is
the colour of the most advanced flowers ; and by
always selecting such, where possible, they both keep
up and sharpen their own taste, and at the same
time give additional opportunities to the blue flowers,
which thus ensure proper fertilisation. • May we not
say that it ought always to be the object of naturalists
in this manner to show not only why such and such
a " spontaneous " variation should have been favoured
whenever it occurred, but also to show why and how
it could ever have occurred at all ?

THE END.

Bonbon :
Tt. CLAY, SONS, AND TAYLOR,

BREAD STREET HILL, E.G.

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