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fl. 



Gin 

of 

the Estate of 

Dr. Maud Merrill James 




THE DIFFERENT FORMS OF 

FLOWERS ON PLANTS OF 

THE SAME SPECIES 



^•5 BY 

CHARLES^ARWIN, M. A., F. R. S ' ^ .' ) - / ? v; 



fV/TH ILLUSTRATIONS 



NEW YORK 
D. APPLETON AND COMPANY 

1897 



mmm $1 



Authorized Edition. 



TO 

PROFESSOR ASA GRAY 

THIS VOLUME IS DEDICATED BY THE AUTHOR 
AS A SMALL TRIBUTE OF RESPECT AND AFFECTION. 



CONTENTS. 



INTRODUCTION Page 1-13 

CHAPTER I. 

Hetebostyled Dimobpuio Plants : PBUiuLACEiB. 

Primula veris or the Cowslip— Differences in structure between the 
two forms — ^Their degrees of fertility when legitimately and ille- 
gitimately united — P. elatior, vulgaris, Sinensis, auricula, &c. — 
Summary on the fertility of the heterostyled species of Primula — 
Homostyled species of Primula — Hottonia palustris — Androsaco 
Vitalliana 14-64 



CHAPTER IL 

Htbbid Primulas. 

The Oxlip a hybrid naturally produced between Primula vcris and 
vulgaris — The differences in structure and function between the 
two parent-species — Effects of crossing long-styled and short- 
styled Oxlips with one another and with the two forms of both 
parent-species — Character of the offspring from Oxlips artificially 
self-fertilised and cross-fertilised in a state of 'iature — Primula 
elatior shown to be a distinct species — Hybrids between other 
heterostyled si)ecies of Primula — Supplementary note on spon- 
taneously pnxluced hybrids in the genus Yerbascum .. 65-80 



n CONTEXTS. 

CHAPTER III. 

Heteeostyled DiMOEPnio I'lants — continued. 

Lioiim grandiflorum, long-styled form utterly sterile with own-fonn 
pollen — Li nil in perenne, torsion of the pistils in the long-styled 
form alone — Homostyled species of Linum — Pulmonaria offici- 
nalis, singular difference in self-fertility between the English 
and German long-styled plants— Pulmonaria angustifolia shown 
to he a distinct species, long-styled form w-mpletely self-sterile — 
Polygonum fagopyrum — Various other heterostyled genera — 
Rubiaceas — Mitchella repens, fertility of the flowers in pairs— 
Houstonia — Faramea, remarkable difference in the pollen-graius 
of the two forms; torsion of the stamens in the short-styled 
fonn alone ; development not as yet perfect — The heterostyled 
structure in the several Rubiaceous genera not due to descent in 
common Page 81-136 



CHAPTEK IV. 

Heteeostyled Trimorphio Plants. 

Lythrum salicaria — Description of the three forms — Their power and 
complex manner of fertilising one anothtr — Eighteen different 
unions possible — Mid-styled form eminently feminine in nature 
— Lythrum Graefferi likewise trimorpliic — L. thymifolia dimor- 
phic — L. hyssopifolia homostyled — Nesaea verticillata trimoi-phic 
— Lagerstroemia, nature doubtful — Oxalis, trimorpbic species of 
— 0. Valdiviana — 0. Regnelli, the illegitimate unions quite 
barren — 0. speciosa — 0. sensitiva — Homostyled species of Oxalis 
— Pontederia, the one monocotyledonous genus known to include 
heterostyled si^ecies 137-187 



CHAPTER V. 

Illegitimate Offspring of Heterostyled Plants. 

Illegitimate offspring from all three forms of Lythrum salicaria — 
Their dwarfed stature and sterility, some utterly barren, some 



CONTKNTS. vii 

fertile — Osalis, transmission ol form to tho legitimate and il- 
legitimate seedlings— Primula Sinensis, illegitimate offspring in 
Rome degree dwarfed and infertile — Equal-atjied Taiieties of P. 
Sinensis, auricula, fimnosa, and elatior — P. vul^ris, red-fiowcred 
variety, illegitimate seedlings sterile — P, veris, ille<titimate 
plants raised daring several sucooasiTe generations, their dwarfed 
stature and sterility — Equal-aljled varieties of P. veris — Traiia- 
misaion of form by Pulmonaria and Polygonum — Concluding 
rt'iTiarks — Close piralleliam between illegitimate fertllisatiou and 
hybridism Page 188-243 



CHAPTER TI. 



COSCLUDISQ 



( Ebterostvleo Plants. 



uMai character of hetertstyled plants— Summary of the 
1 fertility between legitimately and illegitimately 
fertiliacd plaala — Diameter of the pollen-grain s, size of anthers 
and structure of stigma in the d ifferent TormB— AESnities ol the 
genera which include heterostyled species — Nature of the 
advantages derived from hetorostylism — ^The means by which 
plants became heteroatyled — Traosmisaion of form — Bqual- 
Btyled varieties of heterostyled plants — Final remarks 244-277 



CHAPTER VII. 



POLTOAMODS, DKECIODB, A 






ri,AKT8. 



The conversion in various ways of hermaphriidlte into diceciona 
plants — Heterostyled plants rendered dimcious — Riiliiaceie — 
VerbonaceiB — Polygamous and sub-dicecioua plants — Eiionynuis 
— Fragaria— Tho two sub-forms of both seites of Ehamnns and 
Epivaa — lloi — Gyno-dioxiioiiB plants — Thymus, diiforeiico in 
fertility of the hermaphrodite a.nd female individuals — Satiirein 
— Mantier in which the two forms j'robably originated — Scaliion-i 
and other gyno-dicecious planlg — Difference in the siio of tliB 
corolla in the forms of p-lygamous, dioaoions, and gyno-diceoioiis 
plant* 278-309 



nil CONTENTS 

CUAPTER VIIL 

Cleistooamio Flowers. 

General character of cleistogaiDic flowers— List of the genera pro- 
ducing such flowers, and their distribution in the vegetable 
series — Viola, description of the cleistogamic flowers in the 
several species ; their fertility compared with that of the perfect 
flowers— Oxalis acetosella — 0. sensitiva, three forms of cleisto- 
gamic flowers — Vandellia — Ononis — Impatiens — ^Drosera — Mis- 
cellaneous observations on various other cleistogamic plants — 
Aneraophilous species producing cleistogamic flowers — Leersia, 
perfect flowers rarely developed — Summary and concluding 
remarks on the origin of cleistogamic flowers — The cuief con- 
clusions which may be drawn from the observations in this 
volume Page 310-345 



Index 346-353 



DIFFEKENT FORMS OF FLO'WEES 



PLANTS OF THE SAME SPECIES. 



INTRODUCTION. 

The subject of t!ie present volume, namely the dif- 
ferently formed fiowera normally produced by certain 
kinds of plunts, either on the same stock or on distinct 
stocks, ought to have been treated by a professed bota- 
nist, to which distinction I can lay uo claim. As far iis 
the sexual relations of flowers are concerned, Linnseus 
long ago divided them into hermaphrodite, monoecious, 
dicecious, and polygamous species. This fundamental 
distinction, with the aid of several subdivisions in each. 
of the four classes, will serve my purpose; but the 
classification is artificial, and the groups often pass 
into one another. 

The bermaplirodite class contains two interesting 
eub-groiips, namely, heterostyied and cleistogamic 
plants; but there are several other less important 
subdivisions, presently to be given, in which flowers 
differing in various woya from one another ai'e pro- 
duced by the same species. 

Some plants were described by me several ye»\rs ago, 
in a scries of papers read before the Linnean Society,' 



2 DTTRODUCTIoy. 

the in.lividuala of which exist un«Ier two or three 
forms, <lilfering in the length «.»f their pistils and 
stam'^ns and in other respects. They w^^re called by 
me dimorphic an- 1 trimorphic, but have since been 
better named by HiM-brand, hetentstvled.* As I 
have many still unpublished observations with respect 
to these plants, it has seemed to me advisable to re- 
publish my former papers in u cimnected and cor- 
rected form, together with the new matter. It will be 
shown that these heterostyled plants are adapted for 
reciprocal fertilisation ; so that the two or three forms, 
though all are hermaphrodites, are related to one 
another almost like the males and females of ordinary 
nnisf.'xual animals. I will also give a full abstract of 
such observations as have been published since the 
appfjarance of my papers ; but only those cases will be 
noticed, with respect to which the evitlence seems fairly 
satisfactory. Some plants have been supposed to be 
heterostyled merely from their pistils and stamens 
varying greatly in length, and I have been myself 
more than once thus deceived. With some species the 



of tbfj PrfKVj^dinjfH of the Linncftn 
Hocii^ty, vol. vi. \m% p. 77. 

" (hi tiio Kxirtt*-iirv) of Two 
KorinH, nri'i on tlioir Ilocipro<;al 

of th«i Of^riiiH fiititiiii." Ibid. YoL 
rii. mVA, p. «II. 

*' Oti ilio K«'Xiifil K';1atioT)flof tlio 
TIiP'^i H'orrriMof I/t/thrum nnlicaria,* 
lhu\. vol. viii. \HV,\, p. 10!). 

'*()ii tli<'(/liMiru'i<)r find Ifybrid- 
Ilko Nfthirn of iUt'. onVprhiff from 
ilio fnoiiiliiiiiiio niiioiirt of IMtnor- 



tibin iiikI Trbiiorpbio riaiittt." 
bid. vol X. iKCH. i>. :\[rx 

•'On Ilio H|H«rllln Difforrnrfa 
tNtiv^ncii i'rf inula wriii, Hrlt. Fl. 
Ivnr.opUuiniliH, \,\\i\\ ), /'. vuUjari»^ 
llili. 1*1. (viir. ntuiuliHf f^nii.j, iukI 



P. elatior^ Jiicq. ; and on the 
Hybrid Nature of the Common 
Oxlip. With Supplementary Re- 
marks on Natnr:illy Produced Hy- 
brids in the Genus Verbascum.** 
Ibid. vol. X. 1868, p. 437. 

* The t»Tm *' heterostyled " does 
not exprefls all the differences be- 
tween tiie forms; but this is a 
failure common in many cases. 
As the term has been adopted by 
writers in various countries, I am 
unwilling to change it for that ot 
heterogone or heterogonous, though 
this ban been proposed by so high 
an authority as Prof. Asa Gray : 
see the * American Naturalist, 
Jan. 1877, p. 42. 



IXTBODUCTIOS. 3 

piatil continues growing for a long time, so Uiat if old 
and yonng flowers are compared they might be thought 
to be heterostyled. Again, a species tending to become 
diceeioua, with the stamens reduced in some individuals 
and with the pistils in others, often presents a decep- 
tive appeaiance. Unless it be proved thut one form 
is fully fertile only when it is fertilised with pollen 
from another form, we have not complete evidence 
that the species is heterostyled. But when the pistils 
and stamens differ in length in two or three sets of 
individuals, and this is accompanied by a dilTerence in 
the size of the pollen-grains or in tlie state of the 
stigma, we may infer with mxich safety that the species 
" i heterostyled. I have, however, occasionally trusted 
to a difference between the two forms in the length 
the pistil alone, or in the length of the stigma 
together with its more or less papillose condition ; and 
in one instance differences of this kind have been 
proved by trials made on the fisrtility of the two forms, 
to be sufficient evidence. 

The second sub-group above referred to consists of 
hermaphrodite plants, which bear two kinds of flowers 
—the one perfect and fully expanded^the other mi- 
nute, completely closed, with the petals rudimentary, 
often with some of the anthers aborted, and the re- 
maining ones together with the stigmas much reduced 
. in size ; yet these flowers are perfectly fertile. They 
I have been called by Dr. Kiibn* cleistogamic, and they 



' BntauiHche Zeitung,' 1SG7, 
[ p. fS. Several pinuls ura knuvn 
oocAaionoUj to pmdure finwerd 
deatilute of & corolla; bat tbty 
belong to V, difiiireiit class uf 
caaea front I'leuiloganuc Buwon. 
Thia dt&deuD; aeeuB to reaull 
tio'u tlie ctoiiditioiiB to whiuli the 
)iluii(8 luiva bull mbjecled, aiiU 



|Hirtak>^a of tbe nature of n moD- 
blrosuy. All tbe flovTura on tho 
sauie plant ore commoQly affuoted 
in tbo HUQie mmmer. Suab ouaH, 
tliougU tliey have eometiniCB bceu 
raiiknl an cleistagunic, da uol 
tome within our prfscnt Brope : 
see Dr. Maxwell Moatcie, ' Vp^p 
lablo Tur,itolog}-,' ISU'J, p. iOX, 



4 DTTBODCCnOK. 

irill IfO (Ictcribed in the last dupter of tfaia Tolomcb 

Tli<-yuro iaa.ti{aAly aii^ited for selt^rtilimtion, which 
in rflWct'r'l at the cost of a wonderfully small expeodt- 
liim of ]KjlIen; whilst the perfect fiuwere prodat^ by 
till] mam ploiit ata capable of croes-fertilisation. Cer^ 
tain aquatic ipecies, wheo they flower beneath the 
watitr, koop their corollas closed, apparently to protect 
tliiiir polli.ti ; they might therefore be culled cleisto- 
gutiiic, but for reosoiiB assigned in the proper place are 
not included in the present sub-group. Several cleis- 
t^igmuio sjtocieB, as we shall hereafter see, bury their 
(ivarieB or yuuiig capsules in the ground ; but some few 
ntlinr plants bfliove iii the same manner; and, as they 
do not bury all their flowers, they might have formed 
II small sepuato subdivision. 

Another interesting subdivision consists of certain 
plants, dincovorod by H. Mailer, some individuals 
of which hear conspicuous Howers adapted for cross- 
rortilisiition by the aid of inaects, and others much 
stnaller and lesa cnnspicuous flowers, which have often 
boon slightly nn."liti(nl bo as to ensure self-fertilisation. . 
Lynmaohiii vul/aris, Eui^irasia q^cinulia. Wiinanthva 
tviMa-ffaUi, ami Viola Irieahr come under this head." 
Tho aniolh'r niul less coiisiiionons flowers are not closed, 
bnt lis far 03 the purjioso which they serve is con- 
(<i>rut>il, namt'ly, tin' assured propagation of the species, 
tlicy approach in miturtt eleistogomic flowers ; but they 
dirttT fn'Tii tlirm by the two kinds being produced on 
dititiiiot plaiita. 

^^'illl tiKUiy plants, (he flowers towards the outside tA 
lhi< tul1oriKi't>ni<i> are utuelt larger and more Ci.>n3iuca- 
ttUN than tho O'titml i4)09. As 1 shall not h«\-e occ»> ; 

ms n^. »«tA ^ ««, »«^ N-v. ift. WIS. p. «h. 

H, WTS \\>it. *«^ r «- A'... 



INTKODUCTIOS 5 

n to TL-tei to plants of this kind in the foliouing 
chapters, I will here give a few detaila respecting them. 
It is familiar to every one that the ray-florets of tLe 
Compositje often differ remarkably from the others ; and 
so it is with the outer flowers of many UinheUifera-, 
some Cnieiferie and a feiv other fauiilies. Several 
species of Hydmngea and Viburnum offer striking 
instances of the same fact. The KuLiaceous gemis 
Slussienda presents a very curious appearance from 
some of the flowers having the tip of oue of the sepals 
developed into a large petal-like e:(pansion, coloured 
either white or purple. The outer flowers in several 
Acauthaccous genera are large and conspicuous but 
sterile; the next in order are small or, open, moderately 
fertile and capable of cross-fertilisation ; whilst the 
central ones are cleistogamie, being still smaller, closed 
and highly fertile ; so that here the inflorescence con- 
sists of three kinds of flowers." From what we know 
in other cases of the use of the corolla, coloured bracteie, 
&c,, and from what H. Mnller has observeilt on the 
frequency of the visits of iuaecta to the flower-heads of 
the Umbelliferaj aud Compositai being largely deter- 
mined by their conspicuousness, there can he no doubt 
that the increased size of the corolla of the outer 
flowers, the inner ones being in all the above cases 
email, serves to attract insects. The result is that 
cross-fertilisation is thus favoured. Jlost flowers wither 
eoon after being fertilised, but Hildebrand states} that 
the ray-florets of the Compositie last for a long time, 
until all those on the disc are impregnated ; aud this 
clearly shows the use of the former. The ray-florets, 



[.' pp. 108. 412. 



• J. Bciitt, ' Jnnrnal of Bolanj,' .^^u, i.^, 
LniKlim. iii'w Knee, vol. i. 1872, t Sen L.. .^^- 

IHi. Illl-Ii;4. 'LMxTilieGfwhli' 

t ■ Diu Ik-frudituiig Jlt Eta- liei .kii ComiHiBitt 



9 INTRODUCTION. I 

liowerer, ai'e of service iu anothet and very diJTereut ^ 
maimer, namely, by folding inwards at uight and 
during cold rainy weather, so aa to protect tfae florets 
of the disc' Moreover thoy often contain matter 
which is excessively poisonous to insects, as may be 
seen in the use of flea-powder, and in the case of 
Pyrethruni, M. Eellionune has shown that the ray- 
flureta are more poisonous than the disc-flurcta in the 
ratio of about three to two. We may therefore believe | 
that the ray-florets are useful in protecting the flowers | 
from being gnawed by insects.t 

It is a well-known yet remarkable iact that the eir- | 
cumferential flowers of many of the foregoing planta I 
have both their male and female reproductive organs 
aborted, as with the Hydrangea, Viburnum and certain 
Composita} ; or the male organs alone are aborted, as 
in many Compositte. Between the sexless, female and ■ 
hermaphrodite states of these latter flowers, the finest 
gradations may be tmced, as Hildebrand has shown.} 
He also shows that there is a close relation between i 
the size of the corolla in the ray-florets and the degree ] 
of abortion in their reproductive organs. As we have ] 
good reason to believe that these florets are highly 
serviceable to the plants which possess them, more 
especially by rendering the flower-heada conspieuoui J 



* Ktroer olenrly ehnvd tbnt 
thI»Utliaciuie:'Ule6i:hutzmittal 
duB Fi>Ueii9,* IH73, p. 28. 

t ■ 6iirdi;iiei''fl Cliroaicle," 1861, 
p. 10U7. Liodley, ' Ve) ' ' 
KingdoiD,' uD CliryBantli 
1853. p. TOe. Kemer ia liia ju- 
tutesting eBgayC DiaSuholimittel 
dar Jlliittien gagva imbcrnffme 
Giiste,' 1875, p. 10) iimlata tlial 
tlia petaU of moat plnnls onntain 
matter wbioli ia offnnBive ti> in- 
■oulo, Kr timt llicy me a^UUia 



Knu« 



1 tima llie o 



IB of 



fruatiKontLoii an proteolcd. Mj 
gmudliitljor in 17110 ('Lotos of 
tlie Plants,' ?anl« iii, note (o liucs 
181, 188) remarks ttiat "Tlie 
QowE^ra or petals of plnnti arp 
pisrliapa in general more aorid 
tlian rheir Icaroa; bBDce tlie; ni 
inQc:h BeldniiiCT ualL-n by insectft 

I ' Utber (lie Gesolilechtarer- 
li&ltniKio b«i den Cmnpooltca, 
18H9, pp. 7SD1. 




I 



tNTEODUCTION. 7 

insects, it ia a natural inference tliat their corollas 
,Te been increased in size fur this special purpose ; 
iaud that their development has subsequently led, 
through the principle of compensation or balance- 
ment, to the more or less complete reduction of the 
reproductive organs. But an opposite view may be 
maintained, namely, that the reproductive organs 
first began to fail, as often happens under cultiva- 
tion,* and, as a consequence, the corolla became, 
through compensation, more highly developed. This 
view, however, is not probable, for when hermaphrodite 
plants become dicecious or gyuo-dicecious — that is, 
are converted into hermaphrodites and females — the 
corolla of the female seems to bo almost invariably 
reduced in size in consequence of the abortion of the 
male organs. The difference in the result in these two 
classes of cases, may perhaps be accounted for by the 
matter saved throngh the abortion of the male organs in 
the females of gyno-dio3ciocs and dicecious plants being 
directed (as we shall see in a future chapter) to the for- 
mation of an increased supply of seeds; whilst in the 
of the exterior florets and flowers of the plants 
which we are here considering, such matter is expended 
in the development of a conspicuous corolla. Whether 
in the present class of cases the corolla was first af- 
fected, as seems to me the more probable view, or the 
reproductive organs first failed, their states of develop- 
ment are now firmly correlated. "VVe see this well illus- 
trated in Hydrangea and Viburnum ; for when these 
plants are cultivated, the corollas of both the interior 
and exterior flowers become largely developed, and 
eir reproductive organs are aborted. 

• I h«Te diaeneBpd this euhject ivili. Sad ©Jit vol. li. pp. 152, 
■£l my 'Variation of Animals and ISC. 
^^lauta under Domestlctttion,' etinp. 



8 INTEODUCTION, 

There is a cloaely analogons subdivision of planta, 
including the genus Muscari (or Feather Hyacinth) 
and the allied Bellevalia, which hear both perfect 
flowers and closed hud-like bodies that never expand. 
The latter resemble in this respect cloistogamio 
flowers, but differ widely from them in being sterile 
and conspicuous. Not only the aborted flower-buds 
and their peduncles (which are elongated apparently 
through the principle of compensation) are brightly 
coloured, but so is the upper part of the spike — 
all, no doubt, for the sake of guiding insects to the 
inconspicuous perfect flowers. From such eases as 
these KB may pass on to certain Labiatte, for instance, 
Saluia Horniinum, in which (as I hear from Mr. Thisel- 
ton Dyer) the upper bracts ore enlarged and brightly 
coloured, no doubt for the same purpose as before, with 
the flowers suppressed. 

In the Carrot and some allied UmbelUferae, the cen- 
tral flower has its petals somewhat enlarged, and these 
are of a dark purplish-red tint ; but it cannot be sup- 
posed that this one small flower makes the large white 
umbel at all more conspicuous to insects. The cen- 
tral flowers are said" to be neuter or sterile, but I 
obtained by artificial fertilisation a seed (fruit) appa- 
rently perfect from one such flower. Occasionally two 
or three of the flowers next to the central one are simi- 
larly characterised; and according to Vaucberf "eette 
ainguliere degeneration s'etend quelquefois a I'ombelle 
entiere." That the modified central flower is of no 
functional importance to the plant is almost certain. 
It may perhaps be a remnant of a former and ancient 
aondition of the species, when one flower alone, the 



rhjB. dca riunti 



INTEODUCnOH. 9 

■ aentral one, was female and yielded seeds, as in tLe 
innbeLUferoua genus Echinophora. Theie is notliing 
Biirprising in the central flower tending to retain its 
former condition longer than the others ; for when ir- 
regular flowers become regular ot peloric, they are apt 
to be central ; and such peloric flowers apparently owe 
their origin either to arrested development— that is, t« 
the preservation of an early stage of development — or 
to reversion. Central and perfectly developed flowers 
in not a few plants in their normal condition (for in- 
stance, the common Rue and Adosa) difl'er slightly in 
Btructure, as in the number of the parts, from the other 
flowers on the same plant. All such cases seem con- 
nected with the fact of the bad which stands at the 
end of the shoot being better nourished than the 
^^ others, as it receives the most sap.* 
^L The cases hitherto mentioned relate to hermaphro- 
^Hdite species which bear differently constructed flowers ; 
^H.but there are some plants tliat produce differently 
^■formed seeds, of which Dr. Kuhn has given a list.f 
^H With the TJmbelliferfe and Compositie, the flowers that 
^f produce these seeds likewise differ, and the diSerences 
in the structure of the seeds are of a very important 
nature. The causes which have led to difi'erences in 
the seeds on the same plant are not known ; and it is 

■very doubtful whether they subserve any special end. 
We now come to our second Class, that of moncecious 
species, or thoae which have their sexes separated but 
liomo on the same plant. The flowers necessarily 
difl'er, but when those of one sex include rudiments 



• Tliiawhola Hubject, ircludiuB DnmeBticstion,' chap. «vi. 2ml 

Epelotinii, has beun ilLiOtiBscd. and edit. val. ii. p. 33S. 
PtvrerenceBKiven.iDiar ■ Varialiun t ' But. Zdtiuis,' 18G7, p- 67 

mat AuimiJa and Plants under 



10 



IKTBODUCTIOIT. 



of the other sex, the difference between the two kiii^ 
IB usually not great. When the difference is great, 
aa we see in catkln-beariiig planta, thia depend* 
largely on many of the species in thia, aa well as in 
the next or dicecious class, being fertilised by tho 
aid of the wind ;* fur the male flowers have in this 
case to prodnce a surprising amount of incoherent 
pollen. Some few monoscious planta consist of two 
bodies of individuals, with their ilowers differing in 
function, though not in structure ; for certain indivi- 
duals mature their pollen before the female flowers on 
the same plant are ready for fertilisation, anil are called 
proterandrous ; whilst conversely other individuals, 
called proterogynous, have their stigmas mature before 
their pollen is ready. The purpose of this curious func- 
tional difference obviously is to favour the cross-fertili- 
sation of distinct plants. A case of this kind was first 
observed by Delpino in the Walnut {Juglans retfia), and 
has since been observed with the common Nut {Corylm 
avellana). I may add that according to H. Muller the 
individuals of some few hermaphrodite planta differ in 
a like manner ; some being proterandrous and others 
proterogynona.t On cultivated trees of the Walnut and 
Mulberry, the male flowera have been observed to abort 
on certain individuals^, which have thus been converted 
into females ; but whether there are any species in a 
state of nature which co-exist as monoecious and female 
individuals, I do not know. 

The third Class consists of dioecious species, and the 



t Delpino, 'Ult. Osseryftzioni 
inlla DicogttDiia,' part ii. fssc, ii. 
p. 337 Mr. Wetterhan and H. 
Miiller ou Corjlua, ■ Nntutr,' vul. 



iL p. EOT. Bad 1875, p. 26. On 

Eroteraniii'iua anil proterogynoiu 
ermaphmdite indiviiluiila of tho 
same speolea, iea H. Miiller. 'Dia 
BefiuolituDg,' &0., pp. 283, 339. 

t ■ Gardener's Oliton.' 1847 pp. 
511,558. 



INTEODUCTION. 



11 



I 



remarks made under the last class with respect to tlie 
amount of difference between the male and female 
flowers are here applicable. It is at present an in- 
explicable fact that with some dicecious plants, of 
which the Restiaceie of Australia and the Cape of 
Good Hope offer the most striking instance, the dif- 
ferentiation of the seses has affected the whole plant 
to such an extent (as I bear from Mr, Thiselton Dyer) 
that Mr. Bentham and Professor Oliver have often 
found it impossible to match the male and female spe- 
cimens of the same species. In my seventh chapter 
Bome observations will be given on the gradual con- 
Tersion of heterostyled and of ordinary hermaphrodite 
plants into dicecious or sub-dicecious species. 

The fourth and last Class consists of the plants which 
were called polygamous by Linnaiua ; but it appears to 
me that it would be convenient to confine tiiis term to 
the species which co-exist as hermaphrodites, males and 
females ; and to give new names to several other com- 
binations of the sexes— a plan which I shall here 
follow. Polygamous plants, in this confined sense of 
the term, may be divided into two sub-groupa, accord- 
ing as the three sexual forms are found on the same 
individual or on distinct individuals. Of this latter or 
trioicous sub-group, the common Ash {Fraxinua ex- 
celsior) offers a good instance : thus, I examined during 
the spring and autumn fifteen trees growing in the 
same field ; and of these, eight produced male flowers 
alone, and in the autumn not a single seeil ; four pro- 
duced only female Sowers, which set an abundance of 
seeds ; three were hermaphrodites, which had a dif- 
fejent aspect from the other trees whilst in flower, and 
two of them produced nearly as many seeds as the 
female trees, whilst the third produced none, so that it 



12 



INTRODUCTION. 



was in function a male. The separation of the sexe^^ 
however, is not complete in the Ash ; for the female 
fiowets include stamens, which drop off at an early 
period, and their anthers, which never open or dehisce, 
generally contain pulpy matter instead of pollen. On I 
some female trees, however, I found a few anthers con-l 
taining pollen-grains apparently sound. On the male 1 
trees most of the flowers include pistils, but these like- 
wise drop off at an early period ; and the ovules, which 
ultimately ahort, are very small compared with those 
in female flowers of the same age. 

Of the other or monoicoua sub-group of polygamous 
plants, or those which bear hermaphrodite, male an&l 
female flowers on the same individual, the commoa'fl 
Maple (Acer campestre) offers a good instance; bnti 
Lecoq states* that some trees are truly dicecious, and I 
this shows how easily one state passes into another. 

A considerable number of plants generally ranked! 
aa polygamous exist under only two forma, namely, i 
hermaphrodites and females; and these may be called J 
gyno-dicecious, of which the common Thyme offers a i 
good example. In my seventh chapter I shall give | 
some observations ou plants of this nature. Othw ' 
species, for instance several kinds of Atriplex, bear on ( 
the same plant hermaphrodite and female flowers ; and i 
these might be called gyno-monoecious, if a name were 1 
desirable for them. 

Again there are plants which produce hermaphrodite ] 
and male flowers on the same individual, for 
stance, some species of Galium, Veratrum, &c. ; and 
these might be called andro-moncecious. If there 
exist plants, the individuals of which consist of her- | 
maphrodites and males, these might be distinguished ( 



' G&igrapMeBolaniqne,' h 



INTHODDCTION. 



13 



andro-dicBcious, But, after making inquiries irom 
several botanists, I can hear of no such cases, Lecoq, 
however, states,' but without entering into full details, 
that some plants of Caltlia palustns produce only mala 
flowers, and that these live mingled with the her- 
maphrodites. The rarity of such cases as this last one 
ia remarkable, as the presence of hermaphrodite and 
male flowers on the same individual is not an un- 
usual occurrence ; it would appear as if nature did 
not think it worth while to devote a distinct indi- 
vidual to the production of pollen, excepting when 
this was indispensably necessary, as in the case of 
dioecious species. 

I have now finished my brief sketch of the several 
far as known to me, in which flowers differing 

structure or in function are produced by the same 
of plant. Full details will be given in the fol- 
lowing chapters with respect to many of these plants. 
I win begin with the heterostyled, then pass on to 
certain dioecious, sub-dicecious, and polygamous species, 
and end with the cleistogamic. For the convenience of 
the reader, and to save space, the less important cases 
[Bud details have been printed in smaller typo. 

1 cannot close this Introduction without expressing 
ly warm thanks to Dr. Hooker for supplying me with 
specimens and for other aid; and to Mr. Thiselton 
Dyer and Professor Olivet for giving me much in- 
formation and other assistance. Professor Asa Gray, 
also, has uniformly aided me in many ways. To Fritz 
Ululler of St. Catliarina, in Brazil, I am indebted for 
many dried flowers of heterostyled plants, often accom- 

lied with valuable notes. 



^Wtsei 
^Ki St 






* 'G6)grupliia Uotaniqae,' torn. it. p. IBS, 



HETEUUSTYLED UIMOlirulC I'LANTa 



HRTE1tO«rTI.ED DlUDRFEllC Pl,&I(TB : PlUllULACEA.- 

'ilmnU veriB or tiie Ouwelip— DiffBrencoa in stnicture bof 
two frinua — Their degrees of fertilitj when legitimately and illo- 
gltiiuutel; uniti-d — P. elutior, yt/.garia, Sincobia, aartculii, &o, — 
Sunimary on the fertility of tlie heteroatjlod flpncita of Primalft — 
Homob-tyled species of Primula — Hottonla paliutris — Andctwaos 
Vilalliuja. 




3 conmioii^^H 

he length^^H 
•.ence has^^H 
sre varia- ^^\ 



It has long been known to botanists that the commoiij 
Cowslip (Primula veris, Brit. Flora, var. 
Ijn,) exists under two forms, about equally 
which obviously differ from each other in the length' 
of their pistils and stamens.* This difference has 
hitherto been looked at as a case of mere 
bility, but this view, as we shall presently seOj is far 
from the tme one. Florists wlio cultivate the Polyan- 
thus and Auricula have long been aware of the two 
kinds of flowers, and they call the plants which dis- 
play the globular stigma at the mouth of the co^oll£^, 
"pin-headed" or "pin-eyed," and those which display:! 
the anthers, " thrum-eyed."t I will designate the twa. 
forms as the long-styled and short-styled. 

The pistil in the long-styled form is almost exactly 
twice as long as that of the short^tyled. The stigmii 



• Thifl font, aooordiDg to Tor 
UoUl ('t5ut.Zeitiing,' 1S63, p. i2H, 
wae first ohtierved bj PerBono ii 
the yea* 1794, 

t In JoLnwiu'a Diclicioary 
lAruin IB eaid to be the enilg d 
ireaTeni' UireadBi and I enppobi 



that same weaver who oultirutedifl 
the polyanthiu invenCod tikis nanui, IT 
from being ctruek with ttume degrefil 
of reaemblanee between thsclaBteal 
of Bntbuis in tbe mouth oT tbaS 
corolla aud the ends of tiii 1 



PKDIULA YEKI8. 



15 



f stands in the mouth of the corolla or projects just 
I above it, and is thus externally visible. It stands 
high above the anthers, which are situated halfway 
down the tube and cannot be easily seen. In the 
short-styled form the anthers are attitehed near the 
mouth of the tube, and therefore stand above the 
stigma, ivhich is seated in about the middle of the 
tubular corolla. The corolla itself is of a different 




Ua^«fiM bna. Short-cijM foi 

FancDLA V 



lape in the two forms; the throat or expanded 
' portion above the attachment of the anthers being 
much longer in the long-styled than in the short- 
styled fonn. Village children notice this difference, 
as they can best make necklaces hy threading and 
slipping the corollas of the long-styled flowers into 
one another. But there are much more important 
The stigma in the long-styled form 



HETEBOSTVl-ED DIMORPHIC TLANTB. 

18 globular ; in the Bhort-styled it is depressed on 
the summit, so that the longitudinal axis of the 
former is sometimes nearly double that of the latter. 
Although somewhat variable in shape, one difference 
is persistent, namely, in roughness : in some speci- 
mens carefully compared, the papillaj which renUer 
the stigma rough were in the lung-styled form from 
twice to thrice as long as in the short-styled. The 
anthers do not differ in size in the two forms, which 
I mention because this is the case with some hetero- 
styled plants. The most remarkable difference is in 
the pollen-grains. I measured with the micrometer 
many apecimena, both dry and wet, taken from plants 
growing in different situations, and always found a 
palpable difference. The grains disteniled with water 
from the short-styled flowers were about 'OSS mm. 
fWoV '^^ ^° inch) in diameter, whilst those irom the 
long-styled were about -0254 mm. (yj^ of an inch), 
which is in the ratio of 100 to 67. The pollen-grains 
therefore from the longer stamens of the short-styled 
form are plainly larger than those from the shorter 
stamens of the long-styled. When examined dry, 
the smaller grains are seen under a low power to 
bo more transparent than tho larger grains, and 
apparently in a greater degree than can be ac- 
counted for by their less diameter. There is also a 
difference in shape, the grains from the short-styled 
plants being nearly spherical, those from the long- 
styled being oblong with the angles rounded; this 
difference disappears when the grains are distended 
with water. The long-styled plants generally tend 
to flower a little before the short-styled : for instance, 
I had twelve plants of each form growing in separate 
pots find treated in every respect alike; and at the 
time when only a single ahort-styled plant was in 




Chap. 1. 



PKIMULA VERI8. 



17 



flower, seven of the long-styled had expanded their 

^ Sowers. 
We ahall, also, presently see that the short-atyled 
plants produce more seed than the long-styled. It is 
lemarkable, according to Prof. Oliver," that the ovules 
in the imexpanded and im impregnated flowers of the 
latter are considerahly laiger than those of the short- 
styled flowers ; and this I suppose b connected with the 
iong-styled flowers producing fewer seeds, so that the 
ovules have more space and r.onriahment for rapid 
development. 

To sum up the differences :— The long-styled plants 
have a much longer pistil, with a globular and much 
rougher stigma, standing high above the anthers. The 
stamens are short; the grains of pollen smaller and 
oblong in shape. The upper half of the tube of the 
corolla is more expanded. The number of seeds pro- 
duced is smaller and the ovules larger. The plants 
tend to flower first. 

The ahort-styled plants have a short pistil, half the 
mgth of the tube of the corolla, with a smooth de- 
stigma standing beneath the anthers. The 
(Btamens are long ; the grains of pollen are spherical 
rand larger. The tube of the corolla is of uniform 
Fdiameter except close to the upper end. The number 
of seeds produced is larger. 

I have examined a large number of flowers; and 
though the shape of the stigma and the length of the 
pistil both vary, especially in the short-styled form, I 
have never met with any transitional states between 
ttie two forms in plants growing in a state of nature. 
~' i never the slightest doubt under which form a 

ight to be classed. The two kinds of flowers ate 



■ KaL HUt. Rc™>»,' July 18G2, p. 237. 




I 



UETEEOSTYLED DIMOBPinC PLANTS. Caw. I 

aorer found on tlie same individual plant. I marked 
many Cowslips and Primroses, and on the following 
year all retained the same character, as did some in my 
garden which flowered out of their proper season in the 
autumn. Mr. W. Wooler, of Darlington, however, in- 
forms us that he has seen early bloasoma on the Polyan- 
thus," which were not long-styled, but became so later 
in the season. Possibly in this case the pistils may not 
have been fully developed during tbe early spring. An 
excellent proof of the permanence of the two forma may 
be seen in nursery-gardens, where choice varieties of 
the Polyanthus arc propagated by division ; and I found 
whole beds of several varieties, each consisting exclu- 
sively of the one or the other form. The two forms exist 
in the wild state in about equal numbers : I collected 
522 umbels from plants growing in several stations, 
taking a single umbel from each plant ; and 241 were 
long-styled, and 281 short-atyled. No difi'erence in 
tint or size could be perceived in the two great massea 
of flowers. 

We shall presently see that most of the species of 
Primula exist under two analogous forms ; and it may 
be asked what is the meaning of the above-described 
important differences in their structure? The ques- 
tion seems well worthy of careful investigation, and I 
will give my observations on the cowslip in detaiL 
The first idea which naturally occurred to me was, 
that this species was tending towards a dioecious 
condition; that the long-styled plants, with their 
longer pistils, rougher stigmas, and smaller pollen- 
grains, were more feminine in nature, and would pro- 
duce more seed ; — that the short-styled plants, with 
their shorter pistils, longer stamens and larger pol- 

it tbe PoljaDtbas is a viirietj 






PBDIUIjI VEBI3. 



19 



len-graina, were more maaculine in nature. Accord- 
ingly, in I860, 1 marked a few cowslips of botli forms 
growing in my garden, and others growing in an 
open field, and others in a ahady wood, and gathered 
and weighed the -seed. In all the lots the short- 
atyled plants yielded, contrary to my expectation, most 
_aeed. Taking the lota together, the following ia the 



^f Short 



Table 1. 



flhort-stjleJ .:owslijH . . 
Loog-ttfleil oomlipe . . 



\ 



If we compare the weight from an equal number of 
plants, and from an eqnal number of umbels, and from 
an equal number of capsules of the two forms, we get 
the following results : — 



Table 2. 



- 




' Pliiila. 


OfS.ld 

gmTns. 


Um'b,.L.. 


3ord. 


Komto 
oJCip- 
anlFS. 


Welnht 


Bhorl-stjilfla cowslips 
tong-ttjled cowslips 


10 
10 


92 
70 


100 
100 


178 


100 
100 


34 



So that, by all these standards of comparison, the 
short -styled form is the more fertile ; if we take the 
number of umbels (which is the fairest standard, for 
large and small plants are thus equalised), the ahort- 
Btyled plants produce more seed than the long-styled, 
in the proportion of nearly four to three. 
In 18C1 the (rial was made in a fuller and fairer 











-* * 


-% 






rwiiTjiii ^ . » fr:s 


T« 




Tbeae figntes gire a» tlie fijliuwiiig pn^ntkm 


- 


— 


^«:^ -H-. 


0— 1*1 ink^ 


Long^yW CTwdip. . . . 


IDO ' 1583 
100 1093 


100 MO 
100 333 



The season was much more (avoutable this year than 
the last ; the plants also now grew in good soil, instead 
of in a shofly wood or stniggling with other plants in 
the open field ; consequently the actual produce of 
seed was considerably larger. Kevertheless we hate 
the same relative result; for the ahort-styled plants 
produced more seed than the long-atyled in nearly the 
proportion of three to two ; but if we take the fairest 
Bfamdurd of eompariaon, namely, the product of seeds 
from an equal number of umbels, the excess is, as in 
the former case, nearly as four to three. 

Looking to theso trials made during two successive 
yoara on a large luinibor oi plants, we may safely con- 
oliido t.liut tlio Bhort-styled form is more productive 
ihiiii till' long-Hl.ylod form, and the same result holds 



PBIMULA VEBia. 



21 



^ 



good with some other species of Primula. Conse- 
quently my anticipation that the plimt3 with longer 
pistils, rougher stigmaSj shorter stamens aad smaller 
pollen- grains, would prove to be more feminine in 
nature, is exactly the reverse of the truth. 

In 1860 a few umbels on some plants of both the 
long-styled and short-styled form, which had been 
covered by a net, did not produce any seed, though 
other umbels on the same plants, artificially fertilised, 
produced an abundance of seed ; and this fact shows 
that the mere covering in itself was not injurious. 
Accordingly, in 1861, several plants were similarly 
covered just before they expanded their flowers ; these 
tnrned out as follows : — 



1 


Table 5. 




1 




■«.,., s^ 


H Hiort-stykd . . . 
B lcrag-«ty1eJ . . . 


IS 


24 

74 


(t-3 grain weiaht of sbrf, 
\ or about 50 ia number. 
Not one seed. 



Judging from the exposed plants which grew all round 

IB the same bed, and had been treated in the same 

manner, excepting that they had been exposed to 

the visits of insects, the above six short-styled plants 

ought to have produced 92 grains' weight of seed 

instead of only 1'3; and tha eighteen long-styled 

plants, which produced not one seed, ought to have 

produced above 200 grains' weight. The production of 

« few seeds by the short-styled planta was probably due 

the action of Thrips or of some other minute insect. 

is scarcely nccessai-y to give any additional evidence. 

It I may add that ten pots of polyanthuses and 



22 HETEEOSTYLED DIMORPHIC PLANTS. Cbak^ 

comdips of both forms, protected from insects in i 
greenhouse, did not set one pod, though artificially 
fertilised flowers lu other pots produced an abundance. 
We thus see that the visita of insects are absolutely 
necessary for the fertilisation of Primula vei-ia. If the 
corolla of the long-styled form had dropped off, in- 
stead of remaining attached in a withered state to 
the ovarium, the anthers attached to the lower part of 
the tube with some pollen still adhering to them 
would have been dragged over the stigma, and the 
flowers would have been partially self-fertilised, as is 
the case with PrimuJa Sin^ms through this means. 
It is a rather curious fact that so trifling a difference 
as the falling-off of the withered corolla, should make 
a very great difl'erence in the number of seeds pro- 
duced by a plant if its flowers are not visited by 
insects. 

The flowers of the cowslip and of the other species of 
the genus secrete plenty of nectar ; and I have often 
seen humble-bees, especially B. hortorum and muscorum, 
sucking the former in a proper manner,' though they 
sometimes bite holes through the corolla. No doubt 
moths hkewise visit the flowers, as one of my sons 
caught Cueullia verbasci in the act. The pollen readily 
adheres to any thin object which is inserted into a 
flower. The anthers in the one form stand nearly, but 
not exactly, on a level with the stigma of the other ; 
for the distance between the anthers and stigma ia the 
short-styled form is greater than that in the long- 
atyled, in the ratio of 100 to 90. This difference ia 
the result of the anthers in the long-styled form 
standing rather higher in the tube than does the 
stigma in the short-styled, and this favours their 



] 



PBIMULA VEBIS. 23 

Ipollen being deposited on it. It follows from tho 
position of the organs that if the proboscis of a 
dead humble-bee, or a thick bristle or rough needle, 
be pushed down the corolla, firat of one form and 
then of the other, as an insect would do in visiting 
the two forma growing mingled together, pollen from 
the long-stamened form adheres round the base of 
the object, and is left with certainty on the stigma 
of the long-styled form ; whilst pollen from the short 
stamens of the long-styled form adheres a little way 
above the extremity of the object, and some is 
generally left on the stigma of the other form. In 
accordance with this observation I found that the 
two kinds of pollen, which could easily be recog- 
nised under the microscope, adhered in this manner 
to the proboscides of the two species of humble- 
bees and of the moth, which were caught visiting 
the flowers; but some small grains were mingled 
with the larger grains round the base of the proboscis, 
and conversely some large grains with the small 
grains neat the extremity of the proboscis. Thus 
pollen will be regularly carried from the one form 
to the other, and they will reciprocally fertilise one 
another. Nevertheless an insect in withdrawing its 
proboscis from the corcilla of the long-styled form 
cannot fail occasionally to leave pollen from the same 
flower on the stigma ; and in this case there might 
be self-fertilisation. But this wUl be much more 
likely to occur with the short-styled form ; for when I 
inserted a bristle or other such object into the corolla 
of this form, and had, therefore, to pass it down be- 
tween the anthers seated round the mouth of the 
corolla, some pollen was almost invariably carried 
down and left on the stigma. Minute insects, such 
B ThripB, which sometimes haunt the flowers, would 



24 



HETEBOBTYLED DIMORPHIC PLANTS. Chap. L 



likemse be apt to cause the self-fertilisatitm of both 
forms. 

The several foregoing facts led me to try the effects 
of the two kinda of pollen on the stigmas of the 
two forma. Four essentially different unions are pos- 
sible ; namely, the fertilisation of the stigma of the 
long-styled form by its own-form pollen, and by that 
of the short-styled ; and the stigma of the short-styled 
form by its own-form pollen, and by that of the long- 
styled. The fertilisation of either form with pollen from 
the other form may be conveniently called a legitimate 
union, from reasons hereafter to be made clear ; and that 
of either form with its own-form pollen an illegitimate 
union. I formerly applied the term " heteromorphic " 
to the legitimate unions, and " homomorphic " to the 
illegitimate unions ; but after discovering the exist- 
ence of trimorphic plants, in which many more unions 
are possible, these two terms ceased to be applicable. 
The illegitimate unions of both forms might have been 
tried in three ways ; for a flower of either form may be 
fertilised with pollen from the same flower, or with that 
from another flower on the same plant, or with that 
from a distinct plant of the same form. But to make 
my experiments perfectly fair, and to avoid any evil 
result from self-fertilisation or too close interbreeding, 
I have invariably employed pollen from a distinct 
plant of the same form for the illegitimate unions of 
all the species ; and therefore it may be observed that 
I have used the term " own-form pollen " in speaking 
of such unions. The several plants in all my experi- 
ments were treated in exactly the same manner, and 
were carefully protected by fine nets from the access of 
insects, excepting Tbrips, which it is impossible to ex- 
clude. I performed all the manipulations myself, and 
weighed the seeds in a chemical balance ; but durioj} g 



J 



Jbap. I. PEIMDLA TEEIB. 25 ^M 

bany subsequent trials I followed the more accurate ^M 
plan of counting the seeds. Some of the capsules con- ^M 
iained no seeds, or only two or three, and these are ^M 
excluded in the column headed " good capsules " in ^H 
■ereral of the following tables : — ^^H 

Taslb 6, ^^M 
Prim-ula urn's. ^| 


Maton or tbe Unlun. 


toUltacd. 


TdUI 


ofSUd 
Capsule>. 




Capenlet, 


- LMg^tjled by pollen 
ofihort-Btyled, Le- 
gitiaiat. onion . .| 


22 


15 


U 


8-8 


62 


Un?-.tjl*d by own-j 
form pollen. IIIb-' 
gilimate^nion. .) 


30 8 


5 


3-1 


43 


Short-styltdbv pollen: 
of long-styled. Le-' 
gilEmaw union . .| 


13 


12 


" 


4-e 


44 


Short-styled by o»n-| 
funn pollen. Ille- 


15 


8 


« 


... 


30 


^Bl» two legitimatot 


35 


37 


25 


13'7 


64 


^■Cke t<ro illegitimate) 


35 16 


11 


3-9 


35 


The results may he given in another form (Table 7) ^| 
by comparing, first, the number of capsules, whether ^| 
good or bad, or of the good alone, produced by 100 ^H 
flowers of both forms when legitimately and illegiti- ^| 
niately fertilised ; secondly, by comparing the weight ^| 
of seed in 100 of those capsules, whether good or bad ; ^| 
mvtt thirdly, in 100 of the good capsules. ^H 



26 nP.TKItOSTYLED DIMllRrmC I'LANTS. Chap.^ 

Table 7. 





S.^^. 


Knn,b« 


N«,.,., 


Wi'Lglit 


Numt™ Wi^lghl 


Namlvr' WelrUll 




































till>ed. 








■■'-I"'"- 




gr-dnn 


The two le-j 










1 








100 


77 


71 




lOO 1 50 


lUO 


54 


The two il-l 


















l.gLti™«to 
unions . j 


100 


45 


31 


" 


100 


24 


100 


35 



We here see that the long-atyled flowers fertiliaeil 
with pollen from the short-styled yield more capsules, 
especially good ones (i.e. containing more than one 
or two seeds), and that these capsules contain a greater 
proportional weight of seeds than do the flowers of the 
long-styled when fertilised with pollen from a distinct 
plant of the same form. So it is with the short-styled 
flowers, if treated in an analogous manner. Therefore I 
have called the former method of fertilisation a legiti- 
mate union, and the latter, as it fails to yield the full 
complement of capsules and seeds, an illegitimate 
union. These two kinds of union are graphically re- 
presented in Fig. 2, 

If we consider the results of the two legitimate 
unions taken together and the two illegitimate ones, 
as shown in Table 7, we see that the former com- 
pared with the latter yielded capsules, whether con- 
taining many seeds or only a few, in the proportion of 
77 to 45, or as 100 to 58. But the inferiority of the 
illegitimate unions is here perhaps too great, for on a 
subsequent occasion 100 long-styled and short-styled 
flowers were illegitimately fertilised, and they together 
yielded 53 capsules : therefore the rate of 77 to 53, or 
Its 100 to 69, is a fairer one than that of 100 to 



1 



PBIMDLA VEHI8. 



27 



Eetnrning to Table 7, if we oonsider only the good 
capsules, those from the two legitimate unions were to 
those from the two illegitimate in number aa 71 to 31, 
or as 100 to 44. Agaiu, if we take an equal Dumber of 
capsules, whether good or bad, from the legitimately 
and illegitimately fertilised flowers, we find that the 
former contained seeds by weight compared with the 
.latter as 50 to 24, or as 100 to 48; but if all the 




poor capsules are rejected, of which many were pro- 
duced by the illegitimately fertilised flowers,tbe propor- 
tion is 54 to 35, or as 100 to 65. In this and all other 
cases, the relative fertility of the two kinds of union 
can, I think, be judged of more truly by the average 
number of seeds per capsule than by the proportion of 
I llnwera which yield capsules. The two methods might 



♦rr IT 



.r 



*i;> 



^. '■- .n 



( 



J. lu 
1 "lie 

■Viler 
■:s . r 
?, ir 



-•••- - • ... ... 



- •* . . « 



* ■ 



PRIMULA VEB18. 



29 



I 



00 here we have two bodies, approximately equal id 
number, differing in their sexual powers and related to 
each other like males and females. There are many 
hermaphrodite animals which cannot fertilise them- 
selves, bnt must unite with another hermaphrodite. 
So it is "with numerous plants ; for the pollen is often 
mature and shed, or is mechanically protruded, before 
the flower's own stigma is ready ; and such flowers ab- 
solutely require the presence of another hermaphro- 
dite for sexual union. But with the cowslip and various 
other species of Primula there is this wide difference, 
that one indiridual, though it can fertilise itself im- 
perfectly, must unite with another individual for full 
fertility ; it cannot, however, unite with any other in- 
dividual in the same manner as an hermaphrodite 
plant can unite with any other one of the same species ; 
or as one snail or earth-worm can unite with any other 
hermaphrodite individual. On the contrary, an indi- 
vidual belonging to one form of the cowslip iu order 
to be perfectly fertile must unite with one of the other 
form, just as a male quadruped must and can unite 
only with the female. 

I have spoken of the legitimate unions as being 
fully fertile ; and I am fully justified in doing so, for 
flowers artificially fertilised in this manner yielded 
rather more seeds than plants naturally fertilised in 
a state of nature. The excess may be attributed to 
the plants having been grown separately in good soil. 
With respect to the illegitimate unions, we shall best 
appreciate their degree of lessoned fertility by the 
following facts. Gartner estimated the sterility of the 
onions between distinct species,* in a manner which 
IkUows of a strict comparison with the resolta of the 



I 



Versnclie Qbcr die BoalardeTzengung,' 1819, p. 216. 



HETEBOSTYLED DOIOBPHIO PLANTS. Ctup. 

legitimate and iUegitimate nnions of Primula. Wil 
/'. wri», for every lOU seeds yielded by the two le- 
gitlmute uaioDs, only 64 were yielded Ly an equal 
number of good capsules from tlie two illegitimate 
unions. Witb P. Sinensis, as we sball hereafter see, 
tlie proportion was nearly the same — namely, as 100 
to G2. Kow Gartner has shown that, on the calcula- 
tion of Verbasmm lychnitis yielding with its own poUea 
100 seeds, it yielded when fertilised by the pollen of 
V. Plueniceum DO seeds ; by the pollen of V. nigrum, 
63 aeeda ; by that of V, hlattaria, 62 seeds. So again, 
Vianthue harhaius fertilised by the pollen of D. superhta 
yielded 81 seeds, and by the pollen of D. Japonieus 
60 seeds, relatively to the 100 seeds produced by its 
own pollen. We thus see — and tlie fact is highly re- 
markable — that with Primula the illegitimate unions 
relatively to the legitimate are more sterile than. 
crosses between distinct species of other genera reW 
tively to their pure unions. Mr. Scott has given* a 
still more striking illustration of the same &ct: he 
crossed Primula auricula- with pollen of four other 
species (P. PcUinurt, viscosa, hirstUa, and veriiciUata), 
and these hybrid unions yielded a larger averse 
number of seeds than did P. auricula when fertilised 
illegitimately with its own-form pollen. 

The benefit which heterostyled dimorphic plants de- 
rive from the existence of the two forms is sufficiently 
obvious, namely, the iuterorossing of distinct plants 
being thus ensured.'l' Nothing can be better adapted 
for this end than the relative positions of the anthers 
and stigmas in the two forms, as shown in Fig. 2 ; but to 



• ' JonTD. Linn. Soo. Bot.,' vol. fertilisalinn ' how gitntlj the off- 
tUL 181H, p. 93. spHng from interorosaed plnata 



f 



■tUP. I. FRIUULA TEKIS. 31 

W&ia whole subject I shall recur. No doubt poUeu will 
occaaionallf be placed by insects or fall on the stigma 
of the same flower ; and if cross-fertilisation fails, such 
self-fertilisation will be advantageous to the plant, aa 
it will thus be saved from complete barrenness. But 
the advantage is not so great as might at first be 
thonght, for the seedlings from illegitimate unions do 
inot generally consist of both forms, but all belong to 
the parent form ; they are, moreover, in some degree 
weakly in constitution, as will be sliown in a future 
chapter. If, however, a flower's oivn pollen should first 
be placed by insects or fall on the stigma, it by no 
means follows that cross-fertilisation will be thus pro- 
vented. It is well known that if pollen from a distinct 
species be placed on the stigma of a plant, and some 
hours afterwards its own pollen be placed on it, the 
latter will be prepotent and will quite obliterate any 
effect from the foreign poUen; and there can haitlly 
be a doubt that with heterostyled dimorphic plants, 
pollen from the othor fonn will obliterate the effects of 
pollen from the same form, even when this has been 
placed on the stigma a considerable time before. To 
test this belief, I placed on several stigmas of a long- 
styled cowslip plenty of pollen from the same plant, 
and after twenty-four hours added some from a short- 
styled dark-red polyanthus, which is a variety of the 
cowslip. From the flowers thus treated 30 seedlings 
were raised, and all these, without exception, bore 
rifddish flowers ; so that the efl'ect of pollen from the 
same form, though placed on the stigmas twenty-four 
hours previously, was quite destroyed by that of pollen 
from a plant belonging to the other form. 

Finally, I may remark that of the four kinds of 
miions, that of tlie short-styled illegitimately fertilised 
with its own-form pollen seems to be the most sterile of 



U2 



UKTKHOSTTL&D UIUOBTHIO PLANTS. 



nil, M jn<Ig<i>tl by Ute AvvnigQ number of seeds, whici 
(lio mjisiiW (.^mtMned. A smaller proportion, also, of 
tbcBD ilimU tltttn of the others germinated, and they 
Itenuitiatod moiv sluvrly. The sterility of this union Ls 
Hifl more rvmuTkubK', «3 it has already been shown 
tbnt thp all" irl-«t villi pluits yield a larger number of 
•otiJs tlk&u tbi> long^tyled, whoD both forms are fer- 
tiliited, oitlior naturally or arttficiallr, in a legitimate 
matincr. 

Ill a future ctmpti?r, whon I treat of the offspring 
frv»m lietorostyled dimorphic and trimorphic plants 
illi'gitimftlt'ly fertilised with their own-form pollen, I 
sliall ha\-c occasion Ut sliovr that with die present 
Biwoi^ and s^vcml others, eqnal-styled vsrioties some- 
times Ap|H>ar. 

Prikula. BUTioit, Jacq. J 

This plant, as well as the last or Cowslip (P. vena, 
vel o^emaiie), and the I'rimroso {P. nJ^arw, Tel aeauJis) 
have bot>n ooneiilered by aome botanists as varieties of 
tbo same spocii's. But they are all three undoubtedly 
dlatiuot, as will Iw shown in the next chapter. The 
present spcPies resembles to a certain extent in general 
appearauoe the common oxlip, which is a hybrid be- 
tween the cowslip and primrose. Primula datior is 
fouud in England only in tiro or three of the eastern 
oouutios ; and I was supplied with living plants by Mr. 
Doubleday, who, as I bolievc, first called attention to 
ite oxist^'noe in England. It is common in some parts 
nf the Continent; and U. Muller* has seen sevei 
kinds of humble-bees and other boes, and BomWUn 
visiting tlie flowers in Korth Germany. 

• ' Die BoTruoliCuag der Blumeu,' i^ 34?. 



PKiiruLA p::i^tior 



The results of my trials on the relative fertility of 
vthe two forms, when legitimately and illegitimately 
lifertiliaed, are given in the following table : — 



1 


Tadik 8- 








H SiOmotXJmm. 


fatili^!prJlu.«i, 


CpaulB. 


'5Sr 




■ LoDf-styied fotm, bv] 

" polUnof.hort-styki! 

Legitimate umoiT .( 


10 


6 


62 


31 


48-5 


Long-«tyled forni, hyl 
own-form pollen. 11- 


,. 


« 


49* 


3 


.,., 


pollenof long-slvk'd. 


., 


8 


61 


37 


47-7 


Shorl-stjUd foiTO, byl 
own-form poUen. 11- 


17 


3 


19 


9 j 12-1 


L Th. t»0 legitimate! 
B nniona togetber . ./ 


20 U 


62 


37 


47-1 


H Tlia two illegitimate) 
■ uBioDS logethBr . .J 


», 1 , 


49* 


2 35-5 



H we compare the fertility of the two legitimate 
I Unions taken together with that of the two illegitimate 
Jimions together, as judged by the proportional number 
Kof flowers which when fertilised in the two methods 
ryielded capsules, the ratio is as 100 to 27 ; so that by 
" this standard the present species is much more sterile 
than P. veris, when both species are illegitimately fer- 
tilised. If we judge of the relative fertility of the two 
kinds of unions by the average number of seeds per 
capsule, the ratio is as 100 to 75. But this latter 



UETKKOSTYLEU DIMORPHIC I'LA>JTS. Coat. 



1(1 
DOt I 



niunber is probably mucb too liigh, as many of the seeds 
prtnlucftd by tlio illegitimately fertilised long styled 
flowers were so small that tbcy probably would not 
have germinated, and ought not to have been coimted.J 
Several long-atylcd and short-styled plants were pro 
tected from the access of insects, and must have beenl 
spontaneously self-fertilised. They yielded altogether 
only six capsules, containing any seeds ; and their 
average number was only 7 ■ 8 per capsule. Some, 
moreover, of these seeds were so small that they coulcl J 
hardly have germinated. 

Herr W. Breitenbach informs me that he examined,^ 
in two sites near the Lippe (a tributary of the Khine), 
894 flowers produced by 198 plants of this species; and 
he found 407 of these flowers to be long-styled, 411 
sbort-Btyled, and 16 equal-styled. I have heard of no J 
other instance with heterostyled plants of equal-styleiB 
flowers appearing in a state of nature, though far &oittJ 
rare with plants which have been long cultivated. Itl 
is still more remarkable that in eighteen cases thel 
same plant produced both long-styled and short-styled,! 
or long-styled and equal-styled flowers ; and in two 
out of the eighteen cases, long-styled, short-styled, and 
equal-styled flowers. The long-styled flowers greatly 
preponderated on these eighteen plants, — 61 consistin 
of this form, 15 of equal-styled, and 9 of the short 
styled form. 

Primula voiGARia (var. acaulis, Linn.), 
The primrose of En'jUtJt Writers. 

Mr. J. Scott examined 100 plants growing near] 
Edinburgh, and found 44 to be long-styled, and 59 1 
short-styled ; and 1 took by chance 79 plants in Kent,! 
of which 39 were long-styled and 40 short-styled; 



I 

id 

1 

1 



PnUIULA VULGARIS. ^0 

Ltfaat the two lots together consisted of 83 long-styled 
and 96 short-styled planta. In the long-styled form 
the pistil is to that of the short-styled in length, from 
an average of five measiireraents, as 100 to 51. The 
stigma in the long-styled form is conspicuously more 
globose and much more papillose than in the short- 
styled, in which latter it is depressed on the siunmit ; 

Fig. 3. 




BjQvUlDesof polUn-gniDs al Primula suji/oru, distenileil with wni«i, taaen 
magnified and dmwn nnder Ihe camera luoidi. the upper and smaller 
gnioa fTDm the luog-stylad fonn ; Ihg lower and larger grains from 
ttaa ahoit-ttyled. 

Bit is equally broad in the two forms. In both it stands 
paearly, but not exactly, on a level with the anthers of 
the opposite fonn ; for it was found, from an average 

fof 15 measurements, that the distance between the 
middle of the stigma and the middle of the anthers 
in the short-styled form is to that in the long-styled 
as 100 to 93. The anthers do not differ in size in the 

I two forms. The pollen-graius from the sbort-atyled 



3G 



HETEEOBTYLED DIMOBPHIC I'LANTS. Chap. 



flowers Iwfore they were soaked in wat€r were decidedly 
broader, in proportion to tlieir length, than those from 
the long-styled ; after being soaked they were relatively 
to those from the long-styled as 100 to 71 in diameter, 
and more transparent. A large number of flowers from 
the two forms were compared, and 12 of the finest 
flowers from each lot were measured, but there was no 
Bensiblo difference between them in size. Nine lon^ 
styled and eight ahort-styled plants growing together ini 
a state of nature were marked, and their capsules col* , 
lected after they had been naturally fertilised ; and 
the seeds from the short-styled weighed exactly twice 
as much as those from an equal number of long-styled 
plants. So that the piimrose resembles the cowslip in 
the short-styled plants, being the more productive of 
the two forms. The reeults of my trials on the fer- 
tility of the two terms, when legitimately and illegi- 
timately fertilised, are given in Table 9. 

We may infer from this table that the fertility of the 
two legitimate unions taken together is to that of the 
two illegitimate unions together, as judged by the pro- 
portional number of flowers which when fertilised in 
the two methods yielded capsules, as 100 to 60, If we 
judge by the average number of seeds per capsule pro- 
duced by the two kinds of unions, the ratio is as 100 
to 54 ; but this latter figure is perhaps rather too low. 
It is surprising how rarely insects can be seen during the 
day visiting the flowers, but I have occasionally observed 
small kinds of bees at work ; I suppose, therefore, that 
they are commonly fertilised by nocturnal Lepidoptera. 
The long-styled plants when protected from insects 
yield a considerable number of capsules, and they thus 
differ remarkably from the same form of the cowslip, 
which is quite sterile under the same circumstances. 
Twenty -three spontaneously self-fertilised capsules from 



1 



Cn»r, 1. PRIMULA VULQABIS, 

Tablb 9. 
^t Primula vu!(/ai-is. 




37 


1 ..,.„„„.„. 


Number Numher 
of ! o(B"ocl 

letUlised. ptiidu™!- 


S^u^. 






^Hong-atjled form, bj pul-J 
^■Jm from cbon-sUled. 


„ j ■■ 


77 


47 


.... 


^BngstTled form, b^j 

H^owu-farm pollen. II- 

legilimale imioa . , ) 


21 1+ 




30 


52-2 


Sbortttytcd form, b;| 
pDllenrromlDDg-styled. 


' 1 ' 


" 


48 


65-0 


Short-Styled form, by] 
own-form polUa. 11- 


18 7 


43 


5 


188* 


«>lo»* together . .| 


20 18 


77 


47 


66-0 


_ nuloiu together . .J 


39 1 ai 


68 


5 


35-5» 



■ * This BTertES Is perhiiH ralber too low. 

'this form contained, on an average, 19'2 seeds. The 
flhort^styled plants produced fewer spontaneously self- 
fertilised capsules, and fourteen of them contained only 
6"2 seeds per capsule. The self-fertilisation of both forms 
was probably aided by Thrips, which abounded within 
the flowers ; but these minute insects could not have 
placed nearly sufBcient pollen on the stigmas, as the 
spontaneously self-fertilised capsules contained much 
fewer seeds, on an average, than those (as may be seen 
in Table 9) which were artificially fertilised with their 
own-form pollen. But this difference may perhaps be 
attributed in part to the flowers in the table having 
been fertilised with pollen &oni a distinct plant he- 



I 



38 HETEEOSTYLKD DIMOKPUIO PLANTS CEiP. | 

longing to tlie same form ; wliilst tlioae wliich i 
flpontaneoualy self-fertilised no doubt generally rcceiTM 
their own pollen. In a future part of tliU volume 3< 
observations will be given on tlie fertility of a i 
coloured variety of the primrose. 



Primula Sinensis. 

In the long-styled form the jiistil is about twice a 
long as that of the short-styled, and the stamens didW^ 
in a corresponding, but reversed, manner. The stigma 
is considerably more elongated and rougher than that 
of the short-styled, which is smooth and almost 
spherical, being somewhat depressed on the summit; 
but the stigma varies much in all its characters, the 
result, probably, of cultivation. The pollen-grains of 
the short-atyled form, according to Hildebrand,* are 
7 divisions of the micrometer in length and 5 in 
breadth; whereas those of the long-styled are only 
i in length and 3 in breadth. The grains, ther 
fore, of the short-styled are to those of the lonj 
styled in length as 100 to 57. Hildebrand also i 
marked, as I had done in the case of P. veHs, that ti 
smaller grains from the long-styled are much mora 
transparent than the larger ones from the short-stylec' 
form. We shall hereafter see that this cultivatec 
plant varies much in its dimorphic condition a 
often equal-styled. Some individuals may be s 
be sub-he terosty led ; thus in two white-flowered plan^ 
the pistil projected above the stamens, but in one of theiQ'l 



* A.ftfr Ibe HjipeRmnce of way tliat I erred greatly about thdl 

pnper tliia Biitluir published some size nf the pollt-n-t^rninB In " 

excellent observnliuiu on the two firms. I suppoae that 

preBent apecies ('Bot. Zuitutig,' miBtukB I nioftHUred tnloe fl 

iiw. 1, Ittji), and he showd pollen -grains frum the i 



^^&U>. L FfilUIILA SINENSIS. 39 ^H 

^B was longer and had a more elongated and rougher ^H 
^Rtigma, than in the other ; and the pollen-grains from ^H 
^Kie latter were to those from the plant with a more ^H 
^^ongated pistil only aa 100 to SS in diameter, instead ^M 
of aa 1,00 to 57. The corolla of the long-styled and ^M 
short-styled form differs in shape, in the same manner ^H 
aa in P. mris. The long-styled plants tend to flower ^^M 
^^)efore the short-styled. When hoth forms were legiti- ^H 
^niately fertilised, the capsules from the short-styled ^H 
^^mAnts contained, on an average, more seeds than those ^^H 
^Bbom the long-styled, in the ratio of 12-2 to 9*3 by ^M 
^Ereight, that is, as 100 to 78. In the foUowing table ^H 
^Kre have the results of two sets of experiments tried ^^^ 
^Rtt different periods. ^^H 
^1 Iaslb ^^H 
^M Primula Siiiensif. ^^| 


1 ....... 


SumbcT 
fcrtiliiKiL 


...» 

olguod 
prudued. 


1S5 

&P.OW. 


IWcminnl on 1 ^^M 


^Htong-ttf led form, bj pollen { 
^r ofihort-styled. Legitj. 
^^ mate union . . . .) 


,. 


16 


0-5B 


• 1 


Long-stjlrffo™,byawa-l 
fortD pollen. lUegiti- 
mate union , . . .| 


.0 


13 


..„ 


1 


Short-stjied form, by pol-l 
Ua of luDg-»Ijlcd. Le- 
gi lim ate nolo u . . .| 


8 


8 


.-,. 


64 


Sbort-itjled form, by own-l 
form pollen. illegUi- 


7 


' 


,:., 


25 


Tli« two legitimate uuioDi] 


32 


Si 


..«4 


M 


Tba two ilUgltimate nnionsl 
*^>^ / 


27 


" 


o.« 


I 


L J 



iO HETEBoaTYLED DIMOBPHIC PLASTa Oatr.l 

The fertility, therefore, of the two legitimate anioDS 
(ogethet to that of the two illegitimate uniong, as judged 
by the proportional number of flowers which yielded 
capsules, la as 100 to 84. Judging by the average 
weight of seeda per capsule produced by the two kiuda 
of unions, the ratio is as 100 to 63. On another occa- 
sion a large number of flowers of hoth forma were 
fertilised in the same maimer, but no account of their 
number was kept. The seeds, however, were carefully 
counted, and the averagea are shown in the right-hand 
column. The ratio for the number of seeds produced 
by the two legitimate compared with the two illegiti- 
mate unions is here 100 to 53, which is probably more 
accmate than the foregoing one of 100 to 63, 

Hildebrand in the paper above referred to gives the 
results of his experiments on the present species ; and 
these are shown in a condensed form in the following 
table (11), Besides using for the illegitimate unions 
pollen from a distinct plant of the same form, as was 
always done by me, he tried, in addition, the effects of!' 
the plant's own pollen. He counted the aeeds. 

It is remarkable that here all the flowers which' 
were fertilised legitimately, as well as those fertilised 
illegitimately with pollen from a distinct plant be- 
longing to the same form, yielded capsules ; and from 
this iact it might be inferred that the two forms wi 
reciprocally much more fertile in his ease than ii 
mine. But his illegitimately fertilised capsules froi 
both forms contained fewer seeds relatively 
legitimately fertilised capsules than in my expei 
ments ; for the ratio in his case is as 42 to 10( 
instead of, as in mine, as 53 to 100. Fertility is 
very variable element with most plants, being dete»*] 
mined by the conditions to which they are subjected,' 
(chich fact 1 have observed striking instances with 



1 



PRIMULA SINENSia 



Table 11. 
-Primula Sinenm (from midebrand). 



r — 


fi'iiilieea. 


Niunbor 

ofgr^* 


uSmbe'r^l 


^ Long^tyled form, by pnllon of ahort.\ 
rtyisd. Legitimala unioD . . . ./ 


„ j ,. 


„ 


Long^tjlsdfoiTn.hyowQ-fo™ pollen, from! 
■ dbtincl pb.Ilt. iUegitimatB imion ,/ 


28 2G 


IS 


Long-.tyled form, by pollen from samel 
Dower. IlLgitimate union. . . .) 


.7 


21 


17 


Short-atjled form, b; pollsn of loog-l 
»ty!ed. Legitimnte onion . . . ,/ 


u 1 U 


44 


Short styled fgrm, bj own-form pollen,! 


IG 10 


20 


Short-stfleJ, by pollen from the samel 


21 11 


8 


The tVD Irgitlmats nnioni logethgr . . 


28 


2B 


43 


Th« two illegitimate unions togetbtrl 
(own-form pollen) / 


42 


43 


.. 


The two illegitiro-ilo onions together (poL! 
len from the Miae QuwerJ . , . ./ 


48 


33 


13 



present species ; and this may accoimt for the differ- 
ence between my results and those of Hildebrand. His 
plants were kept in a room, and perhaps were grown in 
too small pots or under some other unfavourable condi- 
tions, for his capsules in almost every case contained a 
smaller number of seeds than mine, aa may he seen 
by oomparing the right-hand columns in Tables 10 
■ 111. 

[ The most interesting point in Hildebrand'a expert- 
mta is the difference in the effects of illegitimate 
tilisation with a flower's own pollen, and with that 



UETEBOSTYLED DISIOKPHIC PLANTS. Ciii*. fl 

from a distinct pltiut of the same form. In the latter 
case all the fiowcra produced capsules, whilst only 67 
out of 100 of those fertilised with their own pollen pro- 
duced capsules. The self-fertilised capsules also con- 
tained seeds, as compared with capsules from flowers 
fertilised with pollen from a distinct plant of the & 
form, in the ratio of 72 to 100. 

In order to ascertain how far the present species wat 
spontaneously self-fertile, five long-styled plants i 
protected by me from insects ; and they bore up to t 
given period 147 flowers which set 62 capsules 
many of these soon fell ofl", showing that they had not I 
been properly fertilised. At the same time five shorts 
styled plants were similarly treated, and they bore 116 
flowers which ultimately produced only seven capsules. 
On another occasion 13 protected long-styled plants 
yielded by weight 25-9 grains of spontaneously self- 
fertilised seeds. At the same time seven protected 
short-atyled plants yielded only hall-a-grain weight of 
seeds. Therefore the long-styled plants yielded nearly 
24 times aa many spontaneously self-fertiliaed seeds as 
did the same number of short-styled plants. The chief 
cause of this gre-at difference appears to bo, that when 
the corolla of a long-styled plant falls off, the antheiH, 
from being situated near the bottom of the tube s 
necessarily dragged over the stigma and leave f 
on it, as I saw when I hastened the fall of n 
withered flowers ; whereas in the short-styled flc 
the stamens are seated at the mouth of the corolli 
and in falling off do not brush over the lowly-se 
stigmas. Hildchrand likewise protected some 1 
styled and short-styled plants, but neither ever yielded 
a single capsule. He thinks that the difi'erence in ota 
results may be accounted for by his plants havinO: 
been kept in a room and never having been shaken f' 



Fciup. I. 



PRBtULi AOBICULA. 



43 



I bnt this explaoatioii seems to me doubtful ; Lis plants 

' were in a less fertile condition than mine, as shown by 

\ the difference in the number of seeds produced, and 

it is highly probable that their lessened fertility would 

have interfered with especial force with their capacity 

for producing self-fertilised seeds. 



I 



This species is heterostyled, like the precediug ouea ; but 
amongst the rarietieB distrihuted by florists the long-stjled form 
is rare, as it is not valued. Tliere ie a much greater rektiye in- 
equality in the length of the piati! and stamens in the two forms 
of the anricnJa than in the cowslip ; the pistil in the loag-styled 
being nearly four times as long aa that in the ehort-stjled, in 
which it is barely longer than tliooTiwium. The stigma is nearly 
of the same shape in both forms, but is rougherin the long-styled, 
though the difference is not so greut as between the two forms 
at the cowslip. In the long-etjled plants the stamens are 'very 
■hort, rising bnt little above the ovarimn. The pollen-grains of 
these short stamens, when distended with water, were barelyj^j 
of an inoh in diameter, whereas those irom the long stameus of 
the short^styled plants wero barely j^, showing a relative dif- 
ference of about 71 to 100, The smaller grains of the long- 
etyied plant are also much more transparent, and before disten- 
tion with water more triangular in outline than those of the 
other form. Mr. Scott t compared ten plants of both forms grow- 
ing nnder similar conditions, and four 
styled plant produced more uml>ela a 
Bltort«tyled, yet they yielded fewer Si 
100. liree short-styled plants w 



d that, although the long- 
id more cajisnlcs than the 
Beds, in the ratio of 66 to 
B protected by me from the 



* Aoconling to Kemer oni gar- 
den auricnJaa are detweotled ftumP. 
Mbeiccnif, Jfioq., whjcb is a hybriil 
betweou I he true F. auricHla aud 
tnnuta. TliJBhjbridbBBniiwboen 
propagated for about aOO jeara, 
and produces, when legiiinmttly 
r«ttiliMd, a large aumb^uf aiieda ; 
tiia long-atyled forma yieliliug au 
Lige aambti of 73, and the 



Bhorf-atjled 98 aeeda per capaule- 
see hia " Geschii-ble di:t Anrikel," 
■ Zei tGChr. dea Deiitbcheii und Oeat, 
Alpea-VtraiiiB,' Band vi. p. 52. 
Also ■ Die Priniulocet-n-Biwturten,' 
• Deal. Bot. ZeiliioliTin,' 1^35, Nub. 
3, i, anil 3. 

t 'jDUrn. Linn. Boo. Bui." fol 
viii. ISM, p. 8U. 



44 



HETEKOSTYLED DIMOBPHIO PLANTS. Chap, i 



access of iusecta, and tbey did not produce a single seed. 1 
Scott protected six plants of both forms, and found them ex- 
cessively sterile. Tite pistil of the long'Styled form stands so 
high above the anthers, that it is scarcely possible that poileu 
should reach the stigma without some aid ; and one of Mr. 
Scott's loDg-stjled plants which yielded a few seedii (only 16 in 
number) wsa infested by aphides, and he does not doubt that 
these had. imperfectly fertilieed it. 

I tried a few espenments by reoiprocally fertilising the two 
forms in the same maimer as before, but my plants were un- 
healthy, so I will give, in a condensed form, the results of Mr. 
Scott's eiperimeuts. For fuller particulars with respect to this 
and the five following species, the paper lately referred to may 
be consulted. In each cosa the fertility of the two legitimate 
unions, taken together, is compared with that of the two ille- 
gitimate unions together, by the same two standards a.B before, 
namely, by the proportional number of Bowers which pro- 
duced good capsules, and by the average nomber of seeds per 
capsula The fertility of the legitimate unions is always taken 
at 100. 

By the first standard, the fertility of the two legitimate nuions 
of the auricula is to that of the two illegitiniate unions as 100 
to 80 ; and by the second standard as 100 to 15, 



According to Mr. Scott, tlie pistil of the long-styled form U 
fnlly four times as long as that of the short-styled, but t 
stigmas are nearly alike in shape and roughness. The si 
do not differ so much in relativo length as the pistils. The pollaa 
grains differ in a marked manner in the two forms; "those e 
the long-styled plants are sharply triquetrous, smaller, and n: 
transparent than those of the short-styled, which are of a blnnt!) 
triangular form," The fertility of the two legitimate nniona t( 
that of the two illegitimate unions is by the first standard i 
100 to 95, and hy the second standard as 100 to 31. 



PllIMnLA COHTUSOIDES. 

The pistil of the long-styled form is about thrice oa long m 
that of the short-styled, the stigma being double as long ai 
jovered with much longer papilla. The pollen-grains of 1 he ehta 



SUMMARY ON PHIMULA. 



45 



I 



Bt;lod form are, as usual, "larger, lees transparent, and more 
bluntly tiiangular than those from the long-styled plants." Tho 
fertility of the two legitimate unions to that of the two ille- 
gitintate unions is b; the first etaadard ob 100 to 7i, and b; 
the second standard as 100 to 66. 

PlUMDLA INVOLUCRATA. 

The pistil of the long-stjlod fona is about thrice as long as 
tiiat of the shorl^styled ; the stigma of the former is globular 
and closely beset with papillie, whilst that of the short-styled 
is Bmootta and depressed oa the apex. The pollen-grains of the 
two forms differ in size and transpaxency as before, but not in 
The fertiUty of tlio two legitimate fo that of the two 
tat« unions is by tiie first standard as 100 to 72; and by 
second Btundord as 100 to 47. 



PnnnjiA faiunoba. 

According la Mr. Scott, the pistil of the long-styled form ia 
only about twice as long aa that of the shorl^styled. The 
Btigmas of the two forms differ but little in shape. The pollen- 
grains differ in tJie usual manner iu size, but not in form. The 
fertility of the two legitimate to that of the two illegitimate 
unions is by the first standard as 100 to 71, and by the second 
standard as 100 to i4. 

^K Summary on iJie fm-egoing heterosiyled species of Pri- 
^^tvla. — Tte fertility of the long and short-styled pltmfs 
^^i the above species of Primula, when the two forms 
^Mre fertilised legitimately, and illegitimately with 
^raollen of the same form taken from a distinct plant, 
has now been givfen. The reanlts are seen in the fol- 
lowing table; the fertility being judged by two 
■tandards, namely, by that of the proportional number 
tof floweit) which yielded capsules, and by that of the 
number of seeds per capsule. But for full 
Bcuracy many more observations, under varied condi- 
jlioc?, would be requisite. 



HETKB06TYLED DMOBPIUC PLAXTS. Cuxr.^ 



Summary an the Ptrt3ilji ef Hu tiro l*gitima/« Unioiu, a 
vitk Mai ^ (A« l<f« JV^malt Cnum*, m titt gtnut iYtnwIa^ | 
rt/omur talen% <rf 100. 





mfBiit.1. u.d««. 


)iu»»rs|K<i<k 


^55^-?^^ 


JndctdollrUx 


P. .blior 

e.Ti>\gniM 

P.Hnari* 




69 
37 
M 
84 


'^tOOhiglL) 

gJCParhipi 


(Hund Iriul) . . 




t 


S3 


(»ft.rHilJ.br«id) . 




100 


42 


P. .uriouU (3«otl) .... 




80 


IS 


P. SikkimcuU (ScoU) . . 




95 


31 


P, cortuwide. (Scotl) . . . 




74 


6B 


P. inrolacraU CScolt) . . . 




72 


48 


P. &rino« (Scoll) . . . . 




71 


44 


AT«.gDofth>aiu<>ped» . 




BB-4 


61-S 



With pliLnta of uU kinds some flowers generally fail 

to produce aipsuk'S, trom vnrious accidental causes ; 
but this source of eiTor has been eliminated, aa f ar as 
possible, in ail tko previous cases, by the manner in 
which the calculations have been made. Supposing, 
for instance, that 20 flowers were' fertilised legiti- 
mately and yielded 18 capsules, and that 30 flowers 
were fertilised illegitimately and yielded 15 cap- 
sules, we may assume that on an average an equal 
projwrtion of thd flowers iu both Iota would fail to 
produce capsules from various accidental causes ; and 
the ratio of Jg to Jg, or aa 100 to 56 (in whole 



mow H 



SUMMAEY ON PRIMULA. 



47 



• hnmbers), would show the proportional number of cap- 
sules due to the two methods of fertilisation ; and the 
number 56 would appear in the left-hand column of 
Table 12, and in my other tables. With respect 
to the average number of seeds per capsule hardly 
anything need be said : supposing that the legiti- 
mately fertilised capsules contained, on an average^ 
I 50 seeds, and the illegitimately fertilised capsules 
I 25 seeds ; then as 50 is to 25 so is 100 to 50 ; and 
I the latter number would appear in the right-hand 
column. 

It ia impossible to look at the above table and doubt 
that the legitimate unions between the two forms of the 
above nine species of Primula are much more fertile 
than the illegitimate unions ; although in the latter 
case pollen was always taken from a distinct plant of 
the same form. There is, however, no close corre- 
spondence in the two rows of figures, which give, 
according to the two standards, the difference of fer- 
tility between the legitimate and Illegitimate unions. 
Thus all the flowers of P. Sinensis which were illegiti- 
mately fertilised by Hildebrand produced capsules ; 
but these contained only 42 per cent, of the number 
of seeds yielded by the legitimately fertilised capsules. 
So again, 95 per cent, of the illegitimately fertilised 
flowers of P. SO^himensis produced capsules ; but these 
contained only 31 per cent, of the number of seeds in 
the legitimate capsules. On the other hand, with 
P. elatior only 27 per cent, of the illegitimately fer- 
tilised flowers yielded capsules; but these contained 
nearly 75 per cent, of the legitimate number of seeds. 
It appears that the setting of the flowers, that is, the 
fjooduction of capsules whether good or bad, is not 
Wto much influenced by legitimate and illegitimate fer- 
1 tilisation as is the number of seeds which the capsules 



46 HETEROSTYLED DIMOHPHIC PLANTS. Chap.| 

Tablb 12. 

Summary on f'ls FertUity ef Qi« ttno Legitiiiiale Unumi, o....^ _. _ 
unlh that <f (Ab Uco IlltffiliTn'tle Unitmt, in the gtnwi I'rivMla, 



P. ebtiur . . . 
P. Sinetuia . . . 

„ (ufterHildebTand) 
cula (Scott) . 
[imenais (Scott) 
usoides (Scott) 
.iBci-Bta (Soott) 
i™ (Scott) . 
Average a! the niae 



Jod^ of by thfl 
rpppnrlloaiLL S umbel 

prodiutd CapauLw. 



Jodged or bv tbe 
Ivcngo Nambiir (of 

if £edi prx Ceptslg. 



'^\ too high.) 
Si f (Porbsps 

I 

61-8 ^^M 



With plants of all kinda some flowers generally fail 
to produce capsules, from various accidental causes ; 
but this source of error has been eliminatedj as far as 
possible, in all the previous cases, by the mannet in 
which the calculations have been made. Supposing, 
for instance, that 20 flowers wore' fertilised legiti- 
mately and yielded 18 capsules, and that 30 flowers 
were fertilised illegitimately and yielded 15 cap- 
sules, we may assume that on an average an equal 
proportion of the flowers in both lots would fail to 
produce capsules from various accidental causes ; and 
the ratio of ^g to Jg, or as 100 to 56 (in wholfrj 



holfr^H 



IP. L 



SUMMAEY ON PHniULA. 



47 



iBunibers), would show the proportional number of eap- 
Bules due to the two metiioda of fertilisation ; and the 
number 50 would appear in the left-hand column of 
Table 12, and in my other tables. With respect 
to the average number of seeds per capsule hardly 
anything need be said : supposing that the legiti- 
mately fertilised capsules contained, on an average, 
50 aeeda, and the illegitimately fertilised capsules 
25 seeds; then as 50 is to 25 so is 100 to 50; and 
the latter number would appear in the right-hand 
»lumn. 

It ia impossible to look at the above table and doubt 
'lat the legitimate unions between the two forms of the 
[AibovQ nine species of Primula are much more fertile 
"lan the illegitimate unions; although in the latter 
Pmse pollen was always taken from a distinct plant of 
the same form. There is, however, no close corre- 
spondence in the two rows of figures, which give, 
according to the two standards, the difference of fer- 
tility between the legitimate and illegitimate unions. 
Thus all the flowers of P. Sinensis which were illegiti- 
mately fertilised by Hildebrand produced capsules ; 
tiimt these contained only 42 per cent, of the number 
a yielded by the legitimately fertilised capsules. 
1 again, 95 per cent, of the illegitimately fertilised 
lowers of P. Sikkiitiensis produced capsules ; but these 
Wntained only 31 per cent, of the number of seeds in 
I legitimate capsules. On the other band, with 
P. elcUior only 27 per cent, of the illegitimately fer- 
tilised flowers yielded capsules ; but these contained 
nearly 75 per cent, of the legitimate number of seeds. 
It appears that the setting of the flowers, that is, the 
production of capsules whether good or bad, is not 
90 much influenced by legitimate and illegitimate fer- 
[ tilisation as is the number of seeds which the capsules 



50 



HETEIBOSTYLEO DIMORPHIO PLANTS Ciiw. t 



iongijlora* are truly homostyled ; and to these may be 
added, according to Axell, P. striata. Mr. Scott ex- 
perimented on P- Scolica, mollis, and verticUlata, and 
found that their flowers yielded an abundance of seeds 
when fertilised with their own pollen. This shows 
that they are not heterostyled in function. P. Scotiea 
is, however, only moderately fertile when insects are 
excluded, but tliis depends merely on the coherent 
pollen not readily falling on the stigma without their 
aid. Mr. Scott also found that the capsules of P. 
verlieiUaia contained ratlier more seed when the flowers 
were fertilised with pollen from a distinct plant than 
when with their own pollen ; and from this fact he in- 
fers that they are sub-heterostyled in function, though 
not in structure. But there is no evidence that two 
sets of individuals exist, which differ slightly in func- 
tion and are adapted for reciprocal fertilisation ; and 
this ia the essence of heterostylism. The more fact 
of a plant being more fertile with poUen from a 
distinct individual than with its own pollen, is com- 
mon to very many species, as I have shown in my 
work ' On the Efl'ects of Cross and Self-fertilisation,' 



HOTTONIA PALU8TRI8. ^H 

This aquatic member of the PrimulaceEe is CMi- 
spicuously heterostyled, as the pistil of the long-styled 
form projects far out of the flower, the stamens being 
enclosed within the tube ; whilst the stamens of the 
short-styled flower project far outwards, the pistil being 
enclosed. This difference between the two forms has 
attracted the attention of various botanists, and that 



I ilUx Uiuliogiiniie uuoli 



k 



J 



HOTTONIA PALUSTBIS. 



51 



■of Sprengel,' in 1793, who, with his usual sagacity, 
adds that he does not believe the existence of the two 
forms to be accidental, though he cannot explain their 
purpose. The pistil of the long-styled form is more 
than tmce as long as that of the short-styled, with the 
stigma rather smaller, though rougher. H. Mullerf 
gives figures of the stigmatic papilltc of the two forma, 
and those of the long-styled are seen to be more than 
double the length, and much thicker than the papillffi 
of the short-styled form. The anthers in the one form 
do not stand exactly on a level with the stigma in 
the other form ; for the distance between the organs is 
greater in the short-styled than in the long-styled 
flowers in the proportion of 100 to 71. In dried speci- 
mens soaked in water the anthers of the short-styled 
form are larger than those of the long-styled, in the 
ratio of 100 to 83. The pollen-grains, also, from the 
short-styled flowers are conspicuously larger than those 
from the long-styled ; the ratio between the diameters 
of the moistened grains being as 100 to 64, according 
to my measurements, but according to the measure- 
ments of H. Miiller as 100 to 61 ; and his are probably 
the more accurate of the two. The contents of the 
larger pollen-grains appear more coarsely granular 
and of a browner tint, than those in the smaller 
grains. The two forms of Hottonia thus agree closely 
in most respects with those of the heterostyled species 
of Primula. The flowers of Hottonia are cross-fertilised, 
according to Miiller, chiefly by Diptera. 

Mr. Scott J made a few trials on a short-styled plant, 
and found that the legitimate unions were in all ways 
pLore fertile than the illegitimate ; but since the pub- 



'DoB enhlecklc Geheimniss 
.jr Nature,' p. 103. 
[ t 'DieB9fruchtung,'ftn.,p.350. 



t 'Jot. 



52 HETEEOSTYLED DIMOBPHIC PLANTS. Chat. I 

lication of his paper H. Miiller has made much fuller 
eiperimenta, and I give hia results in the following 
table, drawn up in accordance with my usual plan : — 

Taslb 13. ■ 

Bottonia palasira (from II. Malhr). H 



tTitniB of ITDlea. 


Kumiw 


ScHUpar 


long-stTlad form, by pollen of .hort^tyle 
LegitimBte anion 


.] 


« 


.1-4 


Long-atjlfld form, bj- own-form pi>lli:u, from 
distinct plunt. lllegitlmnte unii^D , . 


:} 


I. 


ITS 


Short-itjied form, by pollen of long-stTled.l 
legitimate ooloo i 


30 


66-2 


Short-s»Tl«i form, by own-form pollen, from a\ 


19 


18 7 


The two Icgitimata uaions tog other . . . 


64 


78-8 


T)ie two illegitimate unions together , , , 


37 


48-1 



The most remarkable point in this table is the 
small average number of seeds from the short-styled 
flowers when illegitimately fertilised, and the unusually 
large average number of seeds yielded by the illegiti- 
mately fertilised long-atyled flowers, relatively in both 
cases to the product of the legitimately fertilised 
flowers,* The two legitimate unions compared with 



* IL Miiller eaya ('Die Be- 
fruchlung,' &c.. p. ^52( that the 
long-fltj'lej flowora, wlien illtLriti- 
maiel; feitiliseil, yield aa many 
seeds bb when legitiinfttely fer- 
lillBtid; but by odiling np the 
number of seeila from all ihe oap- 
juIbb pmdueed by tlie two tnelhoila 
of fiittilinaliun, as giveu by liim. 



I arrive at the reiults Bliown la 
Talde 13. The average number 
in the lou ^-styled capaultB. when 
legitimate^ feitilised, is 9I'4, 
Hiid when ill<%ititzuilely fertilised, 
77-5: CI OB 100 to S5. H.Miiller 
agrees with me tliat this ia the 
proper numael of slewing th* 



4P. I. ASDEOSACE. 53 

B two illegitimate togetlier yield aeeds in tlie ratio 
f 100 to 61. 

n. MfiUer also tried the effects of illegitimately fer- 
tilising the long-3tyled aad sliort-styled flowers with 
their own pollen, instead of with that from another 
plant of the same form; and the results are very 
piking. For the capsules from the long-styled 
flowers thus treated contained, on an average, only 
15*7 seeds instead of 77 "5; and those from the 
«hort-styIed 6 '5, instead of 18 -7 seeds per capsule. 
The numher 6-5 agrees closely with Jlr. Scott's result 
from the same form similarly fertilised. 

From some observations by Dr. Torrey, Hottonia 
iafiata, an inhabitant of the United States, does not 
appear to be heterostyled, but is remarkable from pro- 
ducing cleistogamic flowers, as will be seen in the \iiat 
chapter of this volume. 

Besides the genera Primula and Hottonia, Androsace 
Tel Gregoria, vel Aretia) vitaJliana is heterostyled. 
Kr. Scott* fertihsed with their own poUen 21 flowers 
on three ahort-styled plants in the Edinburgh Botanic 
Sardena, and not one yielded a single seed ; hut 
eight of them which were fertilised with pollen from one 
f the other plants of the same form, set two empty 
Capsules. He was able to examine only dried speci- 
mens of the long-styled forms. But the evidence seems 
Bufficient to leave hardly a doubt that Androsace is 
heterostyled. Fritz Miiller sent mo from South Brazil 
■dried flowers of a Statice which he believed to be hete- 
jstyled. In the one form the pistil was considerably 
inger and the stamens slightly shorter than the cor- 
jresponding organs in the other form. But as in the 
jhorter-styled form the stigmas reached upto the anthers 

also TroviniDiu In ' Bot. Zc[fDDg,' 1663, p. 0, on thii plonl 



I 

I 



64 HETEB08TTLED DIMORPHIO PLANTS. Chap. L 

of the same flower, and as I could not detect in the 
dried specimens of the two forms any difTerence in their 
stigmas, or in the size of their pollen-grains, I dare not 
rank this plant as heterostyled. From statements made 
by Vaucher I was led to think that Soldanella alpina was 
heterostyled, but it is impossible that Kemer, who has 
closely studied this plant, could have overlooked the 
fact. So again from other statements it appeared prob- 
able that Pyrola might be heterostyled, but H. Muller 
examined for me two species in North Germany, and 
found this not to be the case. 



HYBRID PRmULA& 



CHAPTER n. 

Htbhoi Fbiuui^. 

The Oxlip a lijbrid Duturallj produceil between Primula leris and 
vulgaris— Tliu diffurcncGS in structurti and function Letweuu Ihe 
two pBreot-specieB — Effeota of oroaaing long-atyled and ehort-stjled 
OlIipB witli ono another and witli the two forma <if botli psrcnt- 
species — djaraoter of the offspring from Oilips flrtificially felf- 
fertilifod and oroes-feitlliaed in a slate of nnlure— Fiiniala elatim 
ahown to be a distinot apeciea^Hjbrjds tetwetn nther heterostjled 
Bpt^oiesof Primula — Supplementary Dote iin spoulaueoual; produced 
hybrids in tlie genus Vutbascum. 

The various species of Primula have produced in a 
fitate of nature throughout Europe an extraordinary 
number of hybrid forma. For instance, Professor 
Kemer has found no less than twenty-five such forma 
in the Alps.* The frequent occurrence of hybrids in 
this genus no doubt has been favoured by most of the 
^cies being heterostyled, and consequently requiring 
cross-fertilisation by insects ; yet in some other genera, 
■peciea which are not beterostyled and which in some 
respects appear not well adapted for hybrid-ferti- 
lisation, have likewise been largely hybridised. In 
certain districts of England, the common oxlip — a 
hybrid between the cowslip (P. veria, vel officinalis) 
id the primrose (P. vulgaris, vel acaulis) — is fre- 
fluently found, and it occurs occasionally almost every- 



• " Die Primolnceen-Baatarten,'* 
■Ofiterr. But. Zeitbolirilt,' Jalir 
187^ Nm. S, 4, and 5. See aUo 
Bodnn on hjbtid Frimulw in 



' Bull. Sue. Bot. da Frunoe,' torn. x. 
1853, p. ITS. Alao in ' Bctud dei 
BotL'Uoea Nut' 1675, p. 331. 



56 



HTBBID rRIMULAS. 



where. Owing to tlie frequency of this intermediate 
hybrid form, and to the existence of the Bardfield 
oxlip (P. daiior), which resembles to a certain exteiit 
the common oxlip, the claim of the three forma to 
rank as distinct species has been discussed oftener 
and at greater length than that of almost any othei 
plant. Linnceus considered P. veris, vulgaris and 
datior to be varieties of the same species, as do some 
distinguished botanists at the present day ; whilst 
others who have carefully studied these plants do not 
doubt that they are distinct species. The following 
observations prove, I think, that the latter view is 
correct ; and they further show that the common oxlip 
is a hybrid between P. verts and vulgaris. 

The cowslip differs so conspicuously in general ap- 
pearance from the primrose, that nothing need here 
be said with respect to their external characters.* 
But some less obvious differences deserve notice. Aa 
both species are heterostyled, their complete fertili- 
sation depends on insects. The cowslip is habitually 
visited during the day by the larger humble-bees 
(viz, Bombus mtiscorum and hortorum), and at night 
by moths, as I have seen in the case of CuculUa. The 
primrose is never visited (and I speak after many 
years' observation) by the larger humble-bees, and 
only rarely by the smaller kinds ; hence its ferti- 
lisation must depend almost exclusively on moths. 
There is nothing in the structure of the flowers of the 
two plants which can determine the visits of such 
widely diiferent insects. But they emit a different 
odour, and perhaps their nectar may have a different 
taste. Both the long-styled and short-styled forma of 



a tiie foriD (if tbu utfisaltg aad p. IGl. 



THE COMMON OXUl'. 



57 



he primrose, when legitimately and naturally ferti- 
lised, yield on an average many more seeds pet capsule 
than the cowslip, namely, in the proportion of 100 to 55, 
When illegitimately fertilised they are likewise more 
fertile than the two forms of the cowslip, as shown by 
the larger proportion of their flowers which set cap- 
siilea, and by the larger average number of seeds which 
the capsules contain. The difference also between the 
number of seeds produced by the long-styled and shorts 
styled flowers of the primrose, when both are illegiti- 
mately fertilised, is greater than that between the 
number produced under similar circumstances by the 
two forms of the cowslip. The long-styled flowers ol 
the primrose when protected from the access of all in- 
sects, except such minute ones as Thrips, yield a con- 
siderable number of capsules containing on an average 
19*28eed3per capsule; whereas 18 plants of the long- 
styled cowslip similarly treated did not yield a single 



The primrose, as every one knows, flowera a little 
earlier in the spring than the cowslip, and inhabits 
slightly different stations and districts. TJie primrose 
generally grows on banks or in woods, whilst the cow- 
slip is found in more open places. The geographical 
range of the two forms is different. Dr. Bromfield re- 
marks* that "the primrose is absent from all the in- 
terior region of northern Europe, where the cowslip is 

iligenous." In Norway, however, both plants range 

the same degree of north latitudcf 

The cowslip and primrose, when intercrossed, he- 



r 



• PhytolngUt,' voL iii. p. 69i. 
t H. Leooq, ' Geograph. BoL da 
rEumpe,' toin. Tiii. IS5S, pp. 141, 
lU. See alsn 'Ann. and Mng oi 
Hu. HUt.' U. 1842, pp. 156. 
fljk Aiao llurtau, ' tlure du 



centre de U France,' 1840, torn. ii. 
p. a7ti. With re«|«ol to tlie rarity 
nf P. terii in weatiirn Bootlaud, 
sec H. (J. Watson, ' CjUle Brilan- 



58 UYBHIB PRIMULAa. Omp. II 

tiAvo like distiDct apocics, fur they are far from 
being miituaUy fertile, Gartner* crossed 27 flowera 
of P. vulgaris with pollen of P. veris, and obtained 
16 capsules; but these did not contain any good 
seed. He also crossed 21 ilowers of P. veris with 
jjollen of P. vulgaris ; and now he got only fiye 
capsules, containing seed in a still less perfect 
condition. Gartner knew nothing about betero- 
atylism; and his complete failure may perhaps be 
accounted for by his having croased together the 
same forms of the cowslip and primrose ; for such 
crosses would have been of an illegitimate as well as 
of a hybrid nature, and this would have increased 
their sterility. My trials were rather more fortunate. 
Twenty-one flowers, consisting of both forms of the 
cowslip and primrose, were intercrossed legitimately, 
and yielded seven capsules {i.e. 33 per cent.), contain- 
ing on an average 42 seeds ; some of these seeds, 
however, were so poor that they probably would not have 
germinated. Twenty-one flowers on the same cowslip 
and primrose plants were also intercrossed illegiti- 
mately, and they likewise yielded seven capsules (or 
33 per cent.), but these contained on an average only 
13 good and bad seeds. I should, however, state that 
some of the above flowers of the primrose were fertilised 
with pollen from the polyanthus, which is certainly a 
variety of the cowslip, as may be inferred from the per- 
fect fertility inter ae of the crossed offspring from these 
two plants. t To show how sterile these hybrid unions 



* ' BiiBtanlerzeugQiig,' 1S49, p. 
721. 

t Mr. SodU bflB disciueed Die 
nature of the polynntlms ('Proa. 
Linn, Soo." ?iiL Bol. 18Gi, p. 
103), and Bnivee at a different 
sonKlnBion; but I do nnt think 
that bid experlmcnls nore eiiHi- 



ciontljr numeroTiB. Tlip liegroe nf 
infertility of a orosa is liable to 
muoli fluotuation. Polleo from 
tlie oowulip st fint nppears latlier 
more eilicient on tlie primrose tliBn 
tbnt of tha polynntliuB ; for 12 
flowera of both fnrma of tha prim- 
rose, fcrliliBid Iffc'iiimately i'- 



THE COMMON OXLIP. 



59 



may remind the reader that 90 per'cent. of the 
flowers o£ the primrose fertilised legitimately with 
primrose-pollen yielded capsules, containing on an 
average 66 seeds ; and that 54 per cent, of the flowers 
fertilised illegitimately yielded capsules containing on 
an average 35'5 seeds per capsule. The primrose, 
especially the shurt-styled form, when fertilised by the 
cowslip, is less sterile, as Gartner likewise observed, 
than is the cowslip when fertilised by the primrose. The 
above experiments also show that a cross between the 
same forms of the primrose and cowslip is much more 
sterile than that between different forms of these two 
species. 
L The seeds from the several foregoing crosses were 
nown, but none germinated except those from the 
Fshort-stylud primrose fertilised with pollen of the 
polyanthus ; and these seeds were the finest of the 
whole lot. I thus raised six plant-s, and compared 
them with a group of wild oxlipa which I had trans- 
planted into my garden. One of these wild oxlipa 
produced slightly larger flowers than the others, and 
this one was identical in every character (in foliage, 
flower-peduncle, and flowers) with my six plants, 
excepting that the flowers of the latter were tinged of 
a dingy red colour, from being descended from the 
^lyanthus. 

■ Wo thus see that the cowslip and primrose can- 
lot be crossed either way except with considerable 
SifSculty, that they differ conspicuously in external 
^pearance, that they differ in various physiological 



illpgitimately with pollen of the 
eowjlip gave Bve OiipHQlaa. contain- 
ing on an average 32 4 seeds ^ 
wUkt 18 flowera b-imiluly furtil- 
lled lij poI^iit)iuB-)inIh^ii yioldoil 
E cbI; fife capsuli^e, Ountaiiung oiilj 



23-6 BteiJs. On the nthir himd, 
tliu Beeds proiluoc^ bj tlie poly- 
antliuB-poUun were muoh tlie 
fiacat o{ the whiile lot, and were 
thu Dolf onM wliioh germiuated. 



60 flYBBID PROTULAS. Csap. IL 

clianictera, tbat they inhabit slightly different stations 
and range differently. Hence those botanists who 
rank thoao pliints as varieties ought to be able to prove 
that they are not as well fixed in character as are most 
species ; and the evidence in favour of such instability 
of character appears at first sight very strong. It 
rests, first, on statements made by several competent 
observers that they have raised cowslips, primroses, and 
oxlips from seeds of the same plant; and, secondly, 
on the frequent occurrence in a state of nature of 
plants presenting every intermediate gradation between 
the cowslip and primrose. 

The first statement, however, is of little value ; 
for, heterostylism not being formerly understood, 
the seed-bearing plants were in no instance" pro- 
tected from tho visits of insects ; and there would 
be almost as much risk of an isolated cowslip, or of 
several cowslips if consisting of the same form, being 
crossed by a neighbouring primrose and producing 
oxlips, as of one sex of a dioecious plant, under similar 
circumstances, being crossed by the opposite sex of 
an allied and neighbouring species. Blr. H, C. Wat- 
son, a critical and most careful observer, made many 
experiments by sowing the seeds of cowslips and of 
various kinds of oxlipa, and arrived at the following 
conclusion,t namely, " that seeds of a cowsHp can 
produce cowslips and oxlips, and that seeds of an oxiip 
can produce cowslips, oxlips, and primroses." This 
conclusion harmonises perfectly with the view that in 

* OnenutlinrHtates ill t|je' FI17- tained en abunilante of sceil, 

tologiat' (v<il. iii. p. 703) tlint he wbich is biiuply iiiipoaBiblc 

overedwitli boll-f;laBBeg sniae C.-OW- Heuoe tliere must have been 

Blipa, piitnruaee, &o.. on whioh he some Blmnge error in these ex- 

eipFTiiiK-nttd. He epei^ifles uU peiimeiiU, which maj he pasat-d 

tlie details of bis esporiment, hat orer as vulaeless. 

does not say that bo artifloially f ' Phjftologist,' U, fp. SIT* 

foilillseJ bia plants; yet he ob- SSi; iii. p. 43. 







I 



THE COMMON OXLIP. 6 1 

all cases, when such results have been obtained, the 
unprotected cowsh'pa have been crossed by prunrosea, 
and the unprotected oxlipa by either cowslips or 
primroses ; for in this latter case we might expect, by 
the aid of reversion, which notoriously coines into 
powerful action with hybrids, that the two paj-ent-fonns 
in appearance pure, as well as many intermediate gra- 
.dations, would be occasionally produced. Nevertheless 
the two following statements offer considerable diffi- 
culty. The Eev. Prof. Henslow • raised from seeds of a 
cowslip growing in his garden, various kinds of oxlips 
and one perfect primrose ; but a statement in the same 
paper perhaps throws light on this anomalous result. 
Prof. Henslow had previously transplanted into his 
'garden a cowslip, which completely changed its ap- 

irsnce during the following year, and now rcisembled 
oxlip. Next year again it changed its character, 

■d produced, in addition to the ordinary umbels, a 
■few single-flowered scapes, bearing flowers somewhat 
smaller and more deeply coloured than those of the 
common primrose. From what I have myself observed 
with oxlips, I cannot doubt that this plant was an ox- 
lip in a highly variable condition, almost Hke that of 
the famous Cytisus adami. This presumed oxlip was 
propagated by offsets, which were planted in different 
parts of the garden ; and if Prof, Henslow took by 
mistake seeds from one of these plants, especially if it 
had been crossed by a primrose, the result would be 
quite intelligible. Another case is still more difficult 
to understand : Dr. Herbertf raised, from the seeds of 
a highly cultivated red cowslip, cowslips, oxlips of 
nurious kinds, and a primrose. This case, if accurately 



62 



niBEID PniMOLAS. 



Cuu. ] 



recoriled, which I much doubtj is explicable only onf-i 
the improbable assumption that the red cowslip was 
not of pure parentage. With species and varietieB 
of many kinds, when intercrossed, one ia sometimes 
strongly prepotent over the other ; and instaacea are 
known* of a variety crossed by another, producing 
offspring which in certain characters, as in colour, 
hairiness, &c., have proved identical with the pollen- 
bearing parent, and quite dissimilar to the mother- 
plant ; but I do not know of any instance of the off- 
spring of a cross perfectly resembling, in a consider-, 
able number of important characters, the father alone.| 
It is, therefore, very improbable that a pure cowslip 
crossed by a primrose should ever produce a primrose 
in appearance pure. Although the facts given by Dr. 
Herbert and Prof. Henslow are difHcult to explain, yet 
until it can be shown that a cowslip or a prLoiroBe, 
carefully protected &om insects, will give birth to at 
least oxlips, the cases hitherto recorded have little 
weight in leading ns to admit that the cowslip and 
primrose are varieties of one and the same species. 

Negative evidence is of little value ; but the follow- 
ing facts may be worth giving : — Some cowslips which 
had been transplanted from the fields into a shrubbery 
were again transplanted into highly manured land. 
In the following year they were protected from insecta,. 
artificially fertilised, and the seed thus procured 
sown in a hotbed. The young plants were afterwi 
planted out, some in very rich soil, some in stiff poor 
clay, some in old peat, and some in pots in the green- 
house ; so that these plants, 765 in number, as well as 
their parents, were subjected to diversified and un- 



.ana. 

wai^^H 

-ardi^^l 



tioation,' chap, xv. 2nil edit fi 



J undtJr DomuH- 



TUE COMMON OXLIP. 



63 



■natural treatment; but not one of tliem presented the 
least variation except in size — ^thoso in the peat at- 
taining almost gigantic dimensions, and those in the 
chiy being muuh dwarfed. 

I do not, of course, doubt that cowslips exposed 
during several successive generations to changed con- 
ditions would vary, and that this might occusionally 
occur in a state of nature. Moreover, from the hiw 
of analogical variation, the varieties of any one species 
of Primula would probably ia some cases resemble 
other species of the genus. For instance I raised a rod 
primrose from seed from a protected plant, and the 
flowers, though still resembling those of the primrose, 
were borne during one season in umbels on a long foot- 
stalk like that of a cowslip. 

With regard to the second class of facts in support 
of the cowslip and primrose being ranked as mere 
varieties, namely, the well-ascertained existence in a 
state of nature of numerous linking forms* :— If it can 
be shown that the common wild oxlip, which is inter- 
mediate in character between the cowslip and prim- 
rose, resembles in sterihty and other essential respects 
a hybrid plant, and if it can further be shown that the 
oxlip, though in a high degree sterile, can be fertilised 
by either parent-species, thus giving rise to still finer 
Lgradational links, then the presence of such Hnking 
forms in a state of nature ceases to be an argument 
f any weight in favour o£ the cowslip and primrose 
teing varieties, and becomes, in fact, an argument on 
I other side. The hybrid origin of a plant in n 
tate of nature can be recognised by four tests : first, 
f its occurrence only where both presumed parent- 



6i 



HYBRID PEIMCLAS. 



Bpecies exist or have recently existed ; and this holds 
good, as far as I caa discover, witli the oxlip ; but the 
P. elaiior of Jacq., which, as we shall presently see, 
constitutes a distinct species, must not be confounded 
with the common oxlip. Secondly, by the supposed 
hybrid plant being nearly intermediate in character 
between the two parent-species, and especially by its 
resembling hybrids aj-tifieinlly made between the same 
two species. Now the oxlip is intermediate in cha- 
racter, and resembles in every respect, except in the 
colour of the corolla, hybrids artificially produced be- 
tween the primrose and the polyanthus, which latter 
is a variety of the cowshp. Thirdly, by the supposed 
hybrids being more or less sterile when crossed inter se ; 
but to try this fairly two distinct plants of the same 
parentage, and not two flowers on the same plant, 
should be crossed ; for many pure species are more 
or less sterile with pollen from the same individual 
plant ; and in the case of hybrids from heterostyled 
species the opposite forms should be crossed. Fourthly 
and lastly, by the supposed hybrids being much more 
fertile when crossed with either pure parent-species 
than when crossed inter se, but still not as fully fertile 
as the parent- species. 

For the sake of ascertaining the two latter pointa, 
1 transplanted a group of wild oxhps into my 
garden. They consisted of one long-styled and 
three short-styled plants, which, except in the co- 
rolla of one being slightly larger, resembled each 
other closely. The trials which were made, and the 
results obtained, are shown in the five following 
tables. No less than twenty different crosses are 
necessary in order to ascertain fully the fertility of 
hybrid heterostyled plants, both inter se and with 
thnir two uarent-sDecics, In this instance 256 floweit 



Chap. U. THE COMMON OXLIP. 6o 

were crossed in the course of four seasons. I may 
mention, as a mere curiosity, that if any one were to 
raise hybrids between two trimorphic heterostyled 
species, lie would have to make 90 distLuct unions 
in order to ascertain their fertility in all ways; 
and as he would have to try at least 10 flowers in 
each case, he would be compelled to fertilise 900 
flowers and count their seeds. This would probably 
exhaust the patience of the most patient man. 



Table 14, 
.0 hettfeen Cfie tofo forms qf the ci 



imaU taim. 

. Bhort-stjied oi- 
* , bj pollen of 
TUtyled oilip : 
HBowais ffrtiliBed, 
7d not pmduce one 



Ltj'timaie union. Ulr-gilimaU unfon. 

Short-slyled oi- Long-stjled oi- 
lip, by poUeD of I lip, by its own 
long-slyled oilip; pollen: 24 fiowers 
10 tiowera fertilised, fertilised, produced 

capenU. I tBlning U, 10, 2% 

I 8, ttnd U seeds, 
I Arwage 116 



Long -styled oi- 
lip, by pollen of 
short-styled oillp: 
lOtlo wen fertilised, 
did not produce one 



'f lite Oxlip crossed with Pollen of huGi forms of Iht 
Cowslip, F, verii. 





Legitimati uiiiDH. 




Ltgitiwiatt mion. 


Short-styled ox- 


Short-styled oi- 


Long -styled oi- 


Long -styled oi- 


Kp, by pollcQ of 


lip, by pollen of 


lip, by pollen of 


lip, by pollen of 




long -styled cow- 




short-styled cow- 










tUiHsl, did not pro- 


fertilised, produced 


fertilised, produced 


ferlilised, produced 












taining 7, 3, and 3 


taining 13 wretohed 


taining 21 and 28 








very tine seoda. 




•"""'""'""• 







i HVBRiD TRIMULAS. 

Table 1G. 
folh/orms o/ihe Oxiip crossed with PtAJen of Ixilh/on 





Primrau, 


P. wlyarU. 


1 


nieij-tinvrta unfcu. 


L^Himal, miott. 


ISejUi'mtlt MNWFL 


LigitimaU HHKM. 


Short-atyleJ w- 


Short-sly led di- 


Long-tljlod 01- 


Long-styled o>. 


lip, by pollen of 


lip, br pollen of 


lip, by pollen of 


lip, by polen o( 


(hort-stjled prim- 


lung-stylBd prim- 


long-ityled prim- 


ihort-rtylad pritn- 




co»b: 89 flowari 






fertiliiri, produced 


fertilised, produced 


fertiliied, pro.luo«i 


fertlll«d, produced 




Bii eapiulei, oon- 


four ospeulos, eoo- 




UlDiDg i Had 12 


tiuBmgl6,aO,5, 10. 


taiiiliigl0,7,5,aad 






19, tai 24 seeda. 


6 wretched seeds. 


2S, and 34 mill. 




Avenge 157. Many 


AvBr«gB7'0. 


Average 28-e. 




of the -eeds rery 
l.oor, some gand- 







Tablx 17. 
I of the Co'BsIip nrosfed with Pollen of bothformt of the OxIip, 





Legilimatc mian. Illegitiinate uniun. 


Lejitiinnte mioa. 


Short -rtyled cow- 


Long.«tyled cow- Long-atyled cow- 


Short-styled cow- 


slip, by pollen of 


slip, by pollen of slip, by pollen of 


slip, by pollen of 


shnrt-atyUd oiHpr 


short-slyied oilip: long-styled oilip : 




8 flowers fertili.ed. 


S Sowen fertilised, B flowers fertilised. 


8 aowera fertilised. 




produced one cap- produced thre* cap 


produced eight cap- 






snlea,coatHiniDg5B, 




•eeJe. 6, anJ 14 seeds. 


38, 31, 44, 33, 28, 




Average 8-3. 


37, and 66 seedL 



Tablb 18. 
[lolh forms of the Primrose crossed with Pollen of holh forms of the Oxiip. 



ntcgitlmaie uiaoa. 


Lfgitimale union. Tlleg!l!mati umon. 


Legitimale imiaa. 


Shorl-at jled prim- 


Long-styled prim- Long-styled prim- 


Short^ilyled prim- 




rose, by pollen of rose, by pollen of 


rose, by pollen of 


jhoM-etyled oilip: 


short-atyled o.llptl long-styled oilip: 


long-atyled oilip 


tj flowers fertilised, 


8 flowers fertilised, 8 flowers fertilised, 




pro J need not one 


produced two cap- produced eight exp- 


produced fonr cap 










and 2 seeds. 7, 12, 20, 23, 7, 16, 


S2, 52, 42, and 49 




and 13 seeds. Ave- 






rage 14-0. 


some bad. ATenge 
48-7. 



TBE COMMON OXUP. 87 

I these fire tables the number of capsules 
s produced) by crossing both forms of the 
oilip in a legitimate and illegitimate manner with ono 
another, and with the two fonns of the primrose and 
cowslip, I may premise that the pollen of two of the 
short-styled oxlips consisted of nothing but minute 
aborted whitish ctills ; but in the third short-styled 
plant about one-fifth of the grains appeared in a sound 
condition. Hence it is not surprising that neither 
the short-atyled nor the long-styled oxlip produced a 
single seed when fertilised with this pollen. Nor did 
the pure cowslips or primroses when illegitimately fer- 
tilised with it ; but when thus legitimately fertilised 
they yielded a few good seeds. The female organs of 
the short-styled oxlips, though greatly deteriorated in 
power, were in a rather better condition than the male 
organs; for though the short-stylod oxlips yielded no 
seed when fertilised by the long-styled oxlips, and 
hardly any when illegitimately fertilised by pure cow- 
slips or primroses, yet when legitimately fertilised by 
tliese latter species, especially by the long-styled 
primrose, they yielded a moderate supply of good 
seed. 

The long-styled oxlip was more fertile than the 
throe short-styled oxlips, and about half its pollen- 
grains appeared sound. It bore no seed when legiti- 
mately fertilised by the short-styled oslipa ; but this 
no doubt was due to the badness of the pollen of 
the latter; for when illegitimately fertilised (Table 
14) by ita own pollen it produced some good seeds, 
though much fewer than self-fertil ised cowslips or 
primroses would have produced. The long-styled ox- 
lip likewise yielded a very low average of seed, as may 
be seen in the third compartment of the four latter 
lablea, when illegitimately fertilised by, and when 



k 



immm, 



70 



ffTBEID PEIMULAa. 



CaAP.4 



7 inchcE 



I in height, which bore umbels of flo' 
the same character as before. This fact led mc 
amine the other plants after they Lad flowered and 
were dug up ; and I found that the flowcr-pedunclea 
of all sprung from an extremely short common scape, 
of which no trace can be fimnd in the pure primrose. 
Hence these plants are beautifully intermediate be- 
tween the oslip and the primrose, inclining rather 
towards the latter ; and we may safely conclude that the 
parent oxlips had been fertilised by the surrounding 
primroses. 

From the various facta now given, there can be no 
doubt that the common oxlip is a hybrid between the 
cowslip (P. verts, Brit. Fl.) and the primrose (P. vul- 
garis, Brit. FL), as has been surmised by several 
botanists. It is probable that oxlips may be produced 
either from the cowslip or the primrose as the seed- 
bearer, but oftenest from the latter, as I judge from ■ 
the nature of the stations in which oxlips are generally 
found,* and from the primrose when crossed by tlie 
cowslip being more fertile than, conversely, the cowshp 
by the primrose. The hybrids themselves are also 
rather more fertile when crossed with the primrose 
than with the cowslip. Whichever may bo the seed- 
bearing plant, the cross is probably between different 
forms of the two species ; for we have seen that legiti- 
mate hybrid unions are more fertile than illegitimate 
hybrid unions. Moreover a friend in Surrey found 
that 29 oxlips which grew in the neighbourhood of 
his house consisted of 13 long-styled anil 16 shorts 
styled plants ; now, if the parent-plants had been 
illegitimately united, either the long- or ehort-styled 
form would have greatly preponderated, as we shall 

• Sre also on thU li'sd llurdwioke's 'Sdonce Ooaoip," 18G7, ppi 



d 



Chap. IL 



THE COMMON OXLIP. 



71 



neieafter see good reason to believe. The ciise of 
the oxlip is interesting; for hardly any other in- 
stance is known of a hybrid spontaneously arising 
in such large numbers over so wide an extent of coun- 
try. The common oxlip (not the P. elalior of Jacq.) 
is found almost everywhere throughout England, where 
both cowslips and primroses grow. In some districts, 
as I have seen near Hartfieid in Sussex and in parts 
of Surrey, specimens may be found on the borders of 
almost every field and small wood. In other districts 
the oxlip is comparatively rai'o: near my omti resi- 
dence I have found, during the last twenty-five years, 
not more than five or six plants or groups of ])Iants. 
It is dilBcult to conjecture what is the cause of this 
difference in their number. It is almost necessary 
that a plant, or several plants belonging to the same 
form, of one parent-species, should grow near the 
opposite form of the other parent-species; and it is 
further necessary that both species should be fre- 
quented by the same kind of insect, no doubt a moth. 
The cause of the rare appearance of the oxlip in 
certain districts may be the rarity of some moth, 
which in other districts habitually visits both the 
primrose and cowslip. 

Finally, as the cowslip and primrose differ in the 
various characters above specified,-— as they are in a 
high degree sterile when intercrossed, — as there is no 
trustworthy evidence that either species, when un- 
crossed, has ever given birth to the other species or 
to any intermediate form, — and as the intermediate 
forms which are often found in a state of nature have 
been shown to be more or less sterile hybrids of the 
first or second generation, — we must for the future 
look at the cowslip and primrose as good and true 
species. 



72 



THE DAEDPIELD OXLIP. 



Primula daiior, Jacq., or the BardGeld Oxlip, is 
founil in England only in two or three of the eastern 
counties. On the Ck)ntinent it has a somewhat dif- 
ferent range from that of the cowslip au J primroBe ; 
and it inhabits some districts where neither of these 
species live.* In general appearance it differs so 
much from the common oxlip, that no one accustomed 
to see both forms in the living state could afterwards 
confound them ; but there is scarcely more than a 
single character by which they can he distinctly de- 
fined, namely, their linear-oblong capsules equalling 
the calyx in Ieugth.t The capsules when mature differ 
conspicuously, owing to their length, from those of the 
cowslip and primrose. With respect to the fertility 
of the two forma when these are united in the four 
possible methods, they behare like the other hetero- 
Btyled species of the genus, but differ somewJiat (see - 
Tables 8 and 12) in the smaller proportion of the il- 
legitimately fertilised flowers which set capsules. That 
P. datior is not a hybrid is certain, for when the two 
forms were legitimately united they yielded the large 
average of 47 ' 1 seeds, and when illegitimately united 
35 '5 per capsule ; whereas, of the four possible unions 
(Table 14) between the two forms of the common ox- 
lip which we know to be a hybrid, one alone yielded 
any seed; and in this case the average number was 
only 11 '6 per capsule. Moreover I could not detect 
a single had pollen-grain in the anthers of the short- 
styled P. elatior : whilst in two short-styled plants of 
the common oxHp all the grains were had, as were 
a large majority in a third plant. As the common 

• For England, eeo Hewett 0, 1S58, p. H2. For the Alps, aee 

Wttteon, ' Cj-liele Britaanica,' vol, ' Ann. fttid Mug, Nat. HLit,' vol. 

a. 18*9, p. 292. For tlie Con- is. 1842. pp. ]56and 515. 

tinent, Bee Leeoci, ' Qungraph. t Babinglon's ' Manual of Brit 

laniiiue do I'Eurapo,' torn. viii. isli tli;laiiy,' IS51, p. 258. 



THE BARDFIELD OXLIP. 



73 



ixlip is a hybrid between the primrose and ctuvslip, it 
IB not surprising that eight long-styled flowers of the 
primrose, fertilised by pollen from the long-styled 
oommon oxlip, produced eight capsules (Tuble 18), 
containing, however, only a low average of seeds ; 
whilst the same number of flowers of the primrose, 
gimilarly fertilised by the long-atyled Bardfleld oslip, 
produced only a single capsule ; this latter plant 
being an altogether distinct species from the primrose. 
Plants of P. datior have been propagated by seed in 
a garden for twenty-five years, and have kept all this 
time quite constant, excepting that in some cases the 
flowers varied a little in size and tint.* Nevertheless, 
Qccoiding to Mr. H. C. Watson and Dr. Bromfiold,t 
plants may be occasionally found in a state of nature, 
in which most of the characters by which this species 
can be distinguished from P. veria and vulgaris fail ; 
but such intermediate forma are probably due to 
hybridisation ; for Kemer states, in the paper before 
referred to, that hybrids sometimes, though rarely, 
arise in the Alps between P. datior and veris. 

Finally, although we may freely admit that Primula 

^ peris, vulgaris, and elatior, as well as all the other 
Species of the genus, are descended from a common 
primordial form, yet from the facts above given, we 
must conclude that these three forms are now as fixed 
in character as are many others which are universally 
ranked as true species. Consequently they have as 
i good a right to receive distinct specific names as have, 
|ifor instance, the ass, quagga, and zebra. 

Mr. Scott has arrived at some interesting results by 



I 



• See Mr. H. DoaWeday ii 



'*G»rdonpr'fl Cbto 



UiiraliaU, ibiil. Rud \< 



t ' PliylolHglBt,' vol. L p. 1001, 



74 



HYBRID PEIMTILAB. 



Chat, U 



crossmg other heteroBtyled species of Primula.* I 
have already alluded to bia fitatement, that in foui 
instances (not to mention others) a species when crossed 
with a distinct one yielded a larger number of seeds 
than the same species fertilised illegitimately with its 
own-form pollen, though taken from a distinct plant. 
It has long boon known from the researches of Koh-eutei 
and Gartner, that two species when crossed reciprocally 
sometimes differ as widely as is possible in their fer- 
tility : thus A when crossed with the pollen of B will 
yield a large number of seeds, whilst E may be crossed 
repeatedly with pollen of A, and will never yield a single 
seed. Now Itr. Scott shows in several cases that the 
same law holds good when two heterostyled species 
of Primula are intercrossed, or when one is crossed 
with a homostyled species. But the results are much 
more complicated than with ordinary plants, as two 
heterostyled dimorphic species can be intercrossed in 
eight different ways. I will give one instance from 
Mr. Scott. The long-styled F. hirsuta fertilised legi- 
timately and illegitimately with pollen from the two 
forms of P. auricula, and reciprocally the long-styled 
F, auricula fertilised legitimately and illegitimately 
with pollen from the two forms of P. hirsuta, did 
not produce a single seed. Nor did the shortr 
styled F. hirsuta when fertilised legitimately and 
illegitimately with the pollen of the two forms of 
F. auricula. On the other hand, the short-styled 
P. auricula fertilised with pollen from the long-styled 
P. hirsrUa yielded capsules containing on an average 
no less than 56 seeds ; and the short-styled F. 
auricula by pollen of the short-styled P. hirsuta 
yielded capsules containing on an average 42 seeds 



'Jonra. Lina. Boo, Bat,' vol. viii. 1 



p. 93 to end. 



F'Ciup. IL HYBRID VERBASCUMa 75 

per capsule. So that out of tlie eight possible unions 
between the two forma of these two species, sis 
were utterly barren, and two fairly fertile. We hare 

,■ seen also the same sort of extraordinary irregularity in ^^ 

^L the results of my twenty different crosses (Tables ^H 

^V 11 to 18), between the two forms of the oxlip, prim- ^H 

^p rose, and cowslip. Mr. Scott remarks, with respect ^H 

I to the results of his trials, that they are very surprising, ^H 

as they show us that " the sexual forms of a species ^H 

manifest in their respective powers for conjunction ^| 



I 



I 



with those of another species, physiological peculiari- 
ties which might well entitle them, by the criterion of 
fertility, to specific distinction." 

Finally, although P. veris and v^ijaris, when crossed 
legitimately, and especially when their hybrid ofispring 
are crossed in this manner with both parent-species, 
were decidedly more fertile, than when crossed in an 
illegitimate manner, and although the legitimate cross 
effected by Mr. Scott between P. aurietda and hirsuia 
was more fertile, in the ratio of 56 to 42, than the 
illegitimate cross, nevertheless it is very doubtful, 
from the extreme irregularity of the results in the 
various other hybrid crosses made by Mr. Scott, whether 
it can be predicted that two heterostyled species are 
generally more fertile if crossed legitimately (i.e. when 
opposite forms are united) than when crossed illegiti- 
mately. 

Supplementary Note on some wUd hybrid Verhiscume. 

In an early part of this chapter I remai'ked that few 
othet instances could be given of a hybrid spontane- 
ously arising in such large numbers, and over so wide an 
extent of country, as that of the common oxlip ; but per- 
haps the number of well-ascertained cases of natunUIj 



76 HYBRID VERBASCUMS. 

produced hybrid willows ia equally great/ Numero 
Mpontaneoua hybrids between several epociea of Ciatua, " 
found near Narbonne, have been carefully described 
by M. Timbal-Lagrare.t and many hybrids between an 
Aceras and Orchis have been observed by Dr. Weddell.t 
In the genus Verbascum, hybrids are supposed to have 
often originated§ in a state of nature ; some of these un- 
doubtedly are hybrids, and several hybrids have origi- 
nated in gardens; but most of these cases requirej as 
Gartner remarks, verificatiim. Hence the following 
case is worth recording, more especially as the two 
species in question, V. ikapsua and li/ehniiis, are per- 
fectly fertile when insects are excluded, showing that 
the stigma of each flower receives its own pollen. 
Moreover the flowers offer only pollen to insects, and 
have not been rendered attractive to them by secret- 
ing nectar. 

I transplanted a young wild plant into my garden 
for experimental purposes, and when it flowered it 
plainly differed from the two species just mentioned 
and from a third which grows in this neighbourhood. I 
thought that it was a strange variety of V. tJiapsm. It 
attained the height (by measurement) of 8 feet ! It 
was covered with a net, and ten flowers were fertilised 
with pollen from the same plant ; later in the season, 
when uncovered, the flowers were freely visited by 
pollen-collecting bees; nevertheless, although many 
capsules were produced, not one contained a single 
seed. During the following year this same plant was 



* Max Wichura, ' Die BiistiiTd- 
befruoLtuug, &c, dei Weiden/ 

isea. 

+ • M(!m. de I'Acad. dBfl Sdenrea 
de TouloQSB,' S" sSrio, torn. t. p. 28 

t "AnafllaB des Bo. Nut' 3* 
s^ie, Bot. toia. xriii. p. U. 



p. n. HYBRID VEHBASCUMS. 77 

left uncovered near plants of V. tliapsus and hjchniiia , 
but again it did not produce a single seed, Foui 
flowers, however, which wore repeatedly fertilised 
with pollen of V. lychnitts, whilst the plant was tem- 
porarily kept under a net, produced four capsules, 
which contained five, one, two, and two seeds ; at the 
same time three flowers were fertilised with pollen of 
Y. ihafsus, and these produced two, two, and three 
seeds. To show how unproductive these seven capsules 
were, I may state that a fine capsule from a plant of 
V. ihapsus growing close by contained above 700 seeds. 
These facts led me to search the moderately-sized field 
whence my plant had been removed, and I found in it 
many plants of V. tJiapsus and hjchnitis as well as 
thirty-three plants intermediate iu character between 
these two species. These thirty-three plants differed 
much from one another. In the branching of the stem 
they more closely resembled V. lychnitis than F. Ihapsus, 
but in height the latter species. In the shape of their 
leaves they often closely approached V. lychniiis, but 
some had leaves extremely woolly on the upper surface 
and decurrent like those of Y. thapsus ; yet the degree 
of wooUiness and of decnrrency did nut always go 
together. In the petals being flat and remaining 
open, and in the manner in which the anthers of the 
longer stamens were attached to the filaments, these 
plants all took more after Y. Jyeltnitia than V. thapsus. 
In the yellow colour of the corolla they all resembled 
the latter species. On the whole, these plants appeared 
to take rather more after V. lychnitts than V. thapsus. 
On the supposition that they were hybrids, it is not an 
anomalous circumstance that they should all have pro- 
duced yellow flowers; for Giirtner crossed white and 
yellow-flowered varieties of Verbascum, and the ofF- 
flpring thiis produced never bore flowers of an inter- 



78 



HTBHID TEHBASCUMS, 



Ohai'. ' 



modiate tint, but either pure white or pure yelloB 
flowers, generally of the latter colour.* 

My obsorvations were made in the antnmii ; so thi 
I was able to collect some half-matured capsulea frori 
twenty of the thirty-three intermediate plants, and 
likewise capsules of the pure Y. lychnitia and thapsug 
growing in the same field. All the latter were filled 
with perfect but immature seeds, whilst the capsules of 
the twenty intermediate plants did not contain one 
single perfect seed. These phinta, consequently, were 
absolutely barren. Prom this fact, — from the one plant 
which was transplanted into my garden yielding when 
artificially fertilised with pollen from V- lychmtis and 
iha^us some seeds, though extremely few in number, — 
from the circumstance of the two piire species growing 
in the same field, — and from the intermediate character 
of the sterile plants, there can be no doubt that they 
were hybrids. Judging from the position in which 
they were chiefly found, I am inclined to believe they 
were descended from V. thapsus as the seed-bearer, and 
V. lyohnitis as the pollen-bearer. 

It ia known that many species of Verbascum, when 
the stem is jarred or struck by a stick, cast off theii 
flowers.f This occurs with Y. thapsus, as I haTe re- 
peatedly observed. The corolla first separates from its 
attachment, and then the sepals spontaneously bend 
inwards so as to clasp the ovarium, pushing off the 
corolla by their movement, in the course of two or 
three minutes. Nothing of this kind takes place with , 
young barely expanded flowers. With Yerbaseum lych-:M 
nitis and, as I believe, Y.pkcenieeum the corolla is not castl 



• ' Brtetanlewengung,' p. 307. 

t This wns fltat oboerved by 
OniTi« do Sorttti Bee Sir J. E. 
Saith'B ' EngiiBli Flora,' 1 824, vol. 
L p. 311; also -Lire of Sir J. K. 



SmiUi,' vol. ii. p. 210. I wu 
griidod to these TefereDoes by tlie 
Bev. W. A. Leighton, who oV 
Berved this eame pkeuomeiioii wMIl 
F, virgalaia. ~ 



Ohap. n. HTBBID VEItBASGUMS. 79 

off, however often and severely the stem may be struck. 
In this carious property the above- described hybrids 
took after V-ihapsus; for I observed, to my surprise, that 
when I pulled off the flower-buds round the flowers 
which I wished to mark with a thread, the slight jar 
invariably caused the corollas to fall off, 

These hybrids are interesting under several points of 
view. First, from the number found in various parts 
of the same moderately-sized field. That they owed their 
origin to insects flying from flower to flower, whilst col- 
lecting pollen, there can be no doubt. Although in- 
sects thus rob the flowers of a most precious substance, 
yet they do gi-eat good ; for, as I have elsewhere 
shown," the seedlings of V, thapsas raised from flowers 
fertilised with pollen from another plant, are more 
vigorous than those raised from self-fertilised flowers. 
But in this particular instance the insects did great 
hama, as they led to the production of utterly barren 
plants. Secondly, these hybrids are remarkable from 
differing much from one another in many of their 
characters ; for hybrids of the first generation, if 
raised from uncultivated plajits, are generally uni- 
form in character. That these hybrids belonged to 
the first generation we may safely conclude, from the 
absolute sterility of all those observed by me in a state 
of nature and of the one plant in my gai'den, excepting 

I when artificially and repeatedly fertilised with pure 
pollen, and then the number of seeds produced was 
extremely small. As these hybrids varied so much, an 
almost perfectly graduated series of forms, connecting 
together the two widely distinct parent-species, could 
easily have been selected. This case, like that of 

} the common oxlip, shows that botanists ought to be 

• ' The Effi-cti of Croas unil Beir-fertilisaUoa,' 187G, p. 89, 



80 



HYBRID VE11BASCUM3. 



eaotious in inferring the Bpecific identity of two fori 
from the presence of intermediate gradations ; 
would it be easy in the many cases in ivhich hybrids are I 
moderately fertile to detect a slight degree of sterility ii 
Bueh plants growing in a state of nature and liable to be 
fertilised by either parent-species. Thirdly and lastly, 
these hybrids offer an excellent illustration of a state- 
ment made by that admirable observer Gartner, namely, 
that although plants which can be crossed with ease 
generally produce fairly fertile offspring, yet well- 
pronounced exceptions to tliis rule occur ; and here we 
have two species of Verbascuin which evidently cross 
with the greatest ease, but produce hybrids which are 
excessively sterile. 



LINUM GKAJIWFLOEUM. 



CHAPTEK III. 

HKrEROSTTLED Diuonrfnc l*i.*)rra — eontiiMed. 

Lionm greniiiSi^rniD, long-Btyled fciim utterly sterile with OKD-farm 
pollen— Liniiia ppienne, turaion of the pietila in tbe tung-atyled 
form alone — Homoetyled species of Liotim — PulmonorU offloiiioliB, 
lingular difference m self-fertility between the Engliah and Oormsn 
long-Btyled plants — PulmonKria aiiguntifalia shown to Ixi a iliHtinol 
species, long-atyled form complelelj eelf-steiilc — Poljgannin fiigo- 
pjrum — Varioos other beteroatyled. genera— Kubiacete — MitfheUa 
repeuB, fcrlility of the Bowers in piiirs - Houstunia — Fajamea, 
remarkable dlffi-reuce in tht> pulli-ii-grBins of the two forms ; tor- 
sion of the Btumena in the ebort-etjlcd form alune ; development 
not as yet perfucC — The bL'tetListylod atruclure in the several 
BubiuoeouB ^anera not duo to descent in oommoii. 

It has long been known" that several species of 

I Linum present two forma, and having ohaerved this 

* fact in L. jlavum more than thirty yeara ago, I was 

f ]ed, after ascertaining the nature of het-eroatylism in 

i Primiila, to examine the first apeciea of Linum which 

' I met with, namely, the beautiful L. ffrandiflarvm. 

This plant exiats under two forma, occurring in about 

f equal numbers, which differ little in structure, but 

I greatly in function. The foliage, corolla, stamens, and 

pollen-grains (the latter examined both distended with 

water and dry) are alike in the two forms (Fig. 4), 

The difference is confined to the pistil ; in the ahort- 

styled form the styles and the stigmas are only about 

half the length of those in the long-styled. A more 



Chap. II 

Ig tte ^MiSe identity of two fonna 
I of iiiliiiiti iTtaT" gradations ; noi 
9 in which hybrids are 
9t ■ slight degree of sterility in 
a of Bktnre and liable to be 
Thirdly and lastly, 
t iUnsti&tion of a state- 
e by Ait adBiiMUe observer Gartner, namely, 
t aUe^li flntts vludi can be crossed vith ease 
~ ~ I Cuify Sezdle ofi^ring, yet well- 

■ to this nJe occnr ; and here we 
» of Tci ba acmn which evidently cross 
«idi ^ gmatesl «a*e, bat prodnw hybrids which are 



CHAPTER IIL 

HBTKROfnTi.ED DjuonPHic PLAs'n — etmtinuad. 

Lisiim grandiflonim, long-sfyled form utterly sterile with own-fonn 
pollen— Liniini peienne, toraioQ of the pibtila in tie long-styled 
form ukiiie — H'liuostyled species of Linum — f utmoDBria offloiiiBliE, 
Kuigulu difference in self-fertility between thii English and German 
long-etyled plants — Piilmonaris angiit.UFolia shown to be a distinct 
Bpeeiea, long-stjied tonn poniplelely self-storilo — Polygonum Eiga- 
pynun — ^Various other heteroBljlad genetB— Eubiaceie — Miltbella 
iBpeDs, fertility of the llowera in puira - Houatonia— Fttrames, 
remarkable diOVreuce in Ihe pr Jlcn-graina of the two fonns ; tot- 
sioQof the BlamenBin the short- stjlcd form alone; deTelupmcnt 
not as yet perfect— The hrteri^tyled atruolure in the several 
Bubisceous genera not doe to dcv-'ent iu oomman. 

It has long been knuwn" that several species of 
Linum present two forms, and Laving observed this 
fact in L. fiavum more than thirty years ago, I was 
led, after ascertaining the nature of beterostylism in 
Primida, to examine the first species of Lioum. which 
I met with, namely, the beautifiil £. grandijlo}-um. 
This plant exists under two forms, occurring in about 
hich differ little in structure, but 
corolla, stamens, ami 
both distended with 
te two forms (Fig. 4). 
pistil ; in the shortr 
igmas are only about 
long-styled. A more 

'Bot Zeitong." 




82 HETEBOBTyLED DIMOEPHIO PLANl-S. Cbap. I 

important distinction is, that the five Btigmas in t 
ehort-sty>ed form diverge greatly from one anotherJ 
and pass out between the filaments of the stamen! 



LoDg-stjIeJ form. Shart^tjUd fori 

and thns lie within the tube of the corolla, 
long-styled form the elongated stigmas stand nearly 
upright, and alternate with the anthers. In this latter 
form the length of the stigmas varies considerably, 
their upper extremities projecting even a little above 
the anthers, or reaching up only to about their middle. 
Nevertheless, there is never the slightest difGculty in 
distinguishing between the two forms ; for, besides the 
difference in the divergence of the stigmas, those of 
the short-styled form never reach even to the bases 
of the anthers. In this form the papilla; on the stig- 
matic surfaces are shorter, darker- coloured, and more 
crowded together than in the long-styled form ; but 
these differences seem due merely to the shortening 
of the stigma, for in the varieties of the long-styled 
form with shorter stigmas, the papillic are more crowded 
and darker-coloured than in those with the I 



the long^^^l 



Ob*p. IlL 



UNUM GOANDrFLOEUM. 



83 



stigmas. Considering tlie slight and variable di£fer- 
encea between the two forma of tliis Linum^it is not 
surprising that hitherto they have been overlooked. 

In 1861 I had eleven plants in my garden, eight of 
which were long-styled, and three Bhort-styltid. Two 
very fine long-atyled plants grew in a bed a hundred 
yards off nil the others, and separated from them by » 
screen of evergreens. I marked twelve flowers, and 
placed on their stigmas a little pollen from the short- 
atyled plants. The pollen of the two forms is, as 
stated, identical in appearance ; the stigmas of the 
long-styled flowers were already thickly covered with 
their own pollen — so thickly that I could not find one 
bare stigma, and it was late in the season, namely, 
September 15th, Altogether, it seemed almost childish 
to expect any result. Nevertheless from my experi- 
ments on Primula, I had faith, and did not hesitate to 
make the trial, but certainly did not anticipate the 
full result which was obtained. The germens of these 
twelve flowers all swelled, and ultimately six fine cap- 
sules (the seed of which germinated on the following 
year) and two poor capsules were produced ; only four 
capsules shanking ofiT. These same two long-styled 
plants produced, in the com-se of the summer, a 
vast number of flowers, the stigmas of which were 
covered with their own pollen ; but they all proved 
absolutely barren, and their germens did not even 
flwell. 

The nine other plants, six long-styled and three 
I ehort-atyled, grew not very far apart in my flower- 
I garden. Four of these long-styled plants produced no 
seed-capsules ; the fifth produced two ; and the remain- 
ing one grew so close to a short-styled plant that 
their branches touched, and this produced twelve cap- 
rales, but they were poor ones. The case was different 



84 UETEROSTYLED DIMOEPiUO PLANTS. Chap. Ul 

with the sliort-atyled plants. The one which grew 
close to the long-styled plant produced ninety-four 
imperfectly fertilised capsules containing a multitude 
of bad seeds, with a moderate number of good ones. 
The two other short-styled plants growing together 
were small, being partly smothered by other plants ; 
they did not stand very close to any long-styled plants, 
yet they yielded together nineteen capsules. These 
facts aeem to ahow that the short-styled plants are more 
fertile with their own pollen than are the long-styled, 
and we shall immediately see that this probably is the 
case. But I suspect that the difference in fertility be- 
tween the two fonns was in this instance in part due to 
a distinct cause. I repeatedly watched the flowers, and 
only once saw a humble-bee momentarily alight on 
one, and then fly away. If bees had visited the several 
plants, there cannot be a doubt that the four long- 
styled plants, which did not produce a single capsule, 
would have borne an abundance. But several times I 
saw small diptera sucking the flowers ; and tnese 
insects, though not visiting the flowers with anything 
like the regularity of bees, would carry a little pollen 
from one form to the other, especially when growing 
near together ; and the stigmas of the short-styled 
plants, diverging within the tube of the corolla, would 
be more likely than the upright stigmas of the long- 
styled plants, to receive a small quantity of pollen if 
brought to them by small insects. Moreover fl-om the 
greater number of the long-styled than of the short- 
styled plants in the gurden, the latter would be more 
likely to receive pollen from the long-styled, than the 
long-styled from the short-styled. 

In 1862 I raised thirty-four plants of this Linum in s 

hot-bed ; and these consisted of seventeen long-styled 

• and seventeen short-styled forn\s. Seed sown later in the 



<kv. hl 



UXUX GRAXDIFLOBCM- 



83 



I 



flower-garden yielded flerenteen Itjng-stT^d »nd tweh-e 
Bhort-styled fonns. These facts justify the statement 
that the tvo fonns ate produced in about equal ntun- 
bers. The thirtv-fonr plants of the first lot were kept 
tmder a net which exelnded all inaects, except soch 
minnte ones as Thrips. I fertilised fonrteen long-strled 
floneis legitimately with pollen from the short-styled, 
and got eleven fine seed-capsnles, which contained on 
an average 86 seeds per capsule, but only 56 appeared 
to be good. It may be nell to state that ten seeds is 
the maximum prodactiou for a ea^enle, and that onr 
climate cannot be very favourahle to this Xorth-African 
plant. Od three occasions the stigmas of nearly a 
hundred flowers were fertilised illegitimately with their 
own-form pollen, taken from separate plants, so as to 
prevent any possible ill effects from close inter-breed- 
ing. Many other flowers were also produced, which, as 
before stated, must have received plenty of their own 
pollen ; yet from all these flowers, borne by the seven- 
teen long-atyled plants, only three capsules were pro- 
duced. One of these included no seed, and the other 
two together gave only five good seeds. It is probable 
that this misemble product of two half-fertile capsules 
from the seventeen plants, each of which must have 
produced at least fifty or sixty flowers, resulted from 
their fertilisation with pollen from tiie short-styled 
plants by the aid of Thrips ; for I made a great 
mistake in keeping the two forms under the same net, 
with their branches often interlocking ; and it is sur- 
prising that a greater number of flowers were not 
accidentally fertilised. 

Twelve short-styled flowers were in this instance 
castrated, and afterwards fertilised legitimately with 
pollen from the long-styled form ; and they produced 
Heven fine capsules. These included on an average 



I 



86 HETEKOSTTLED DIMOEPHIC PLANTS, Chap. ] 

7'6 seeda, but of apparently good seed only 4-3 j 
capsule. At ttree separate times nearly a hundred 
flowers were fertilised illegitimately with their own- 
form pollen, taken from separate plants ; and nu- 
merous other flowers were produced, many of which 
must have received their own pollen. From all these 
flowers on the seventeen short -styled plants only fifteen 
capsules were produced, of which only eleven con- 
tained any good seed, on an average 4'2 per capsule. 
As remarked in the case of the long-styled plants, 
some even of these capsules were perhaps the product 
of a little pollen accidentally fallen from the adjoining 
flowers of the other form on to the stigmas, or trans- 
ported by Thrips. Nevertheless the short-styled planta 
seem to be slightly more fertile with their own pollen 
than the long-styled, in the proportion of fifteen cap- 
sules to three; not can this difference be accounted 
for by the short-styled stigmas being more liable to 
receive their own pollen than the long-styled, for the 
reverse is the case. The greater self-fertility of the 
short-styled flowers was likewise shown in 1S61 by 
the plants in my flower-garden, which were left; to 
themselves, and were but sparingly visited by insects. 

On account of the probability of some of the flowers 
on the plants of both forms, which were covered under 
the same net, having been legitimately fertilised in 
an accidental manner, the relative fertility of the two 
legitimate and two illegitimate unions cannot be 
compared with certainty ; but judging from the 
number of good seeds per capsule, the difference was 
at least in the ratio of 100 to 7, and probably much 
greater. 

Hildehrand tested my results, but only on a single 
short-styled plant, by fertilising many flowers with 
their own-form pollen ; and these did not produce a 



LDfUM GBANDIFLORUM. 



87 



I 



■eed. This confinns my suspicion tliat some of the 
few capsules produced by the foregoing seventeen 
flliort-«tylcd plants were the product of accidental 
legitimate fertilisation. Other flowers on the same 
plant were fertilised by Hildebrand with pollen from 
the long-styled form, and all produced fruit." 

The absolute sterility (judging from the experi- 
ments of 1861) of the long-styled plants with their 
own-form pollen led me to examine into its apparent 
and the resulta are so curious that they are 
worth giving in detail. The experiments were tried 
on plants grown in pota and brought successively 
into the house. 

Mrst. Pollen from a short-styled plant was placed 
on the five stigraas of a long-styled tiower, and these, 
after thii'ty hours, were found deeply penetrated by a 
multitude of pollen-tubes, far too numerous to be 
counted ; the stigmas had also become discoloured 
and twisted. I repeated this experiment on another 
flower, and in eighteen hours the stigmas were pene- 
trated by a multitude of long pollen-tubes. This is 
what might have been expected, as the union ia a 
legitimate one. The converse experiment was likewise 
tried, and pollen from a long-styled flower was placed 
on the stigmas of a short-styled flower, and in twenty- 
four hours the stigmas were discoloured, t"isted, and 
penetrated by numerous pollen-tubes ; and this, again, 
is what might have been expected, as the union was 
s legitimate one. 

ikcondly. Pollen from a long-styled flower was placed 

on all five stigmas of a long-styled flower on a separate 

plant : after nineteen hours the stigmas were dissected, 

I tmd only a single pollen-grain had emitted a tube, 



88 HETEBOSTYI-ED DDIOHPUIC PLANTS. Chaf. IU 

and this was a very short one. To make sure that the 
pollen was good, I took in this case, and in most of 
the other cases, pollen either from the same anther oi 
from the same flower, and proved it to be good hy 
placing it on the stigma of a shoit-styled plant, and 
found numerous poUea-tabes emitted. 

Thirdly. Repeated last experiment, and placed own- 
form pollen on all five stigmas of a long-styled flower ; 
after nineteen hours aad a half, not one single grain 
had emitted its tube. 

Faurthli/. Repeated the experiment, with the same 
result after twenty-four hours. 

Fifthly. Repeated last experiment, and, after leaving 
pollen on for nineteen hours, put on an additional 
quantity of own-form pollen on all five stigmas. After 
an interval of three days, the stigmas were examined, 
and, instead of being discoloured and tnisted, they 
were straight and fresh-coloured. Only one grain had 
emitted a quite short tube, which was drawn out of 
the Btigmatic tissue without being ruptured. 

The following experiments ore more striking : — 

SixtMy. I placed own-form pollen on three of the 
stigmas of a long-styled flower, and pollen from a 
short-styled flower on the other two stigmas. After 
twenty-two hours these two stigmas were discoloured, 
slightly twisted, and penetrated by the tubes of nu- 
merous pollen-grains : the other three stigmas, covered 
with their own-form pollen, were fresh, and all the 
pollen-grains were loose ; but I did not dissect the 
whole stigma. 

Seventhly. Experiment repeated in the same manner, 
with the same result. 

Eujhthly. Experiment repeated, but the stigmas were 
carefully examined after an interval of only five hours 
and a half. The two stigmas ii'ith pollen from a 



■Dbap. UL LINUM gbandiflobum. 89 

K«hort-atyled flower were penetrated by innumerable 
■ -tubes, which were as yet short, and the stigmas them- 
I selves were not at all discoloured. The three stigmas 
I covered with their own-form pollen were not pene- 
I tmted by a single pollen-tuhe. 

I NintMt/. Put pollen of a short-styled flower on a 
single long-styled stigma, and own-form pollen on the 
other four stigmas; after twenty-four hours the one 
Btigma was somewhat discoloured and twisted, and 
penetrated by many long tubes : the other four stigmas 
were quite straight and fresh ; but on dissecting them 
I found that three pollen-grains had protruded very 
short tubes into the tissue. 
L Tenlhly. Eepeated the experiment, with the same 
I result after twenty-four hours, excepting that only two 
r omi-form grains had penetrated the stigmatic tissue 
with their tubes to a very short depth. The one 
stigma, which was deeply penetrated by a multitude 
of tnbea from the short-styled pollen, presente<] a 
conspicuous difference in being much curled, half- 
Bhrivelled, and discoloured, in comparison with the 
other four straight and bright pink stigmas. 

^I could add other experiments ; but those now 
given amply suffice to show that the poUen-graina of 
a short-styled flower placed on the stigma of a long- 
styled flower emit a multitude of tubes after an in- 
terval of from five to six hours, and penetrate the 
tissue ultimately to a great depth ; and that after 
twenty-four hours the stigmas thus penetrated change 
colour, become twisted, and appear half-withered. On 
the other hand, pollen-graina from a long-styled flower 
I placed on its own atigmaa, do not emit their tubes 
K after an interval of a day, or even three days ; or at 
l-most only three or four grains out of a multitude emit 
I tiieir tubes, and these apparently never penetrate the 



I 
I 



80 



HETEBOSTYLED DIMOBPHIO PLANTS. Cuir. UI 



atigmatie tiasiie deeply, and the stigmas tbemselvea 
do not soon become discoloured and twisted. 

Tkis seems to me & remarkable physiological iact. 
The pollen-grains of the two forma are undiatinguish- 
able under the microscope ; the stigmas differ only in 
length, degree of divergence, and in the size, shade of 
colour, and approximation of their papillffi, these latter 
differences being variable and apparently due merely 
to the degree of elongation of the stigma. Yet we 
plainly see that the two kinds of pollen and the two 
stigmaa are widely dissimilar in their mutual reaction 
— the stigmaa of each form being almost powerless on 
their own pollen, but causing, through some myste- 
rious influence, apparently by simple contact (for I 
could detect no viscid secretion), the pollen»grains of 
the opposite form to protrude their tubes. It may be 
said that the two pollens and the two stigmas mutually 
recognise each other by some means. Taking fertility 
as the criterion of distinctness, it is no exaggeration to 
say that the pollen of the long-styled Linum grandi- 
florum (and conversely that of the other form) has been 
brought to a degree of differentiation, with respect to 
its action on the stigma of the same form, correspond- 
ing with that existing between the pollen and stigma 
of species belonging to distinct genera. 

Linum perenne.—'UhJa species is conspicuously he tero- 
Btyled, as has been noticed by several authors. The 
pistil in the long-styled form is nearly twice as long as 
that of the short-styled. In the latter the stigmas are 
smaller and, diverging to a greater degree, pass out 
low down between the filaments. I could detect no 
difference in the two forms in the size of the stigmatic 
papillffi. In the long-styled form alone the stigmatic 
surfaces of the mature pistils twist round, so as to face 
the circumference of the flower; hut to this point I 




■. m. 



LINUM PEHESNE. 



9: 



lall presently return. Differently from what occurs in 
L. grandiflorum, the long-styled flowers have stamens 
hardly more than half the length of those in the short- 
styled. The size of the pollen-grains is rather variable ; 
after some doubt, I have come to the conelusioa that 
there is no uniform difforence bL'tween the gmins in 
the two forms. The long stamens in the short-styled 
form project to some height above the corolla, and 
their filaments are eolouied blue apparently from ex- 
posure to the Ught. The anthers of the longer stamens 
correspond in height with the lower part of the stigmas 
of the long-styled flowers; and the anthers of the 
shorter stamens of the latter correspond in the same 
n height with the stigmas of the short-styled 
powers. 

I raised from seed twenty-six plants, of which twelve 
roved to be long-styled and fourteen short-styled, 
!hey flowered well, hut were not large plants. As I 
^d not expect them to flower so soon, I did not trans- 
Blant them, and they unfortunately grew with their 
ranches closely interlocked. All the plants were 
jovered under the same net, excepting one of each 

* form. Of the flowers on the long-styled plants, twelve 
were illegitimately fertilised with their own-form pol- 
len, taken in every case from a separate plant ; and not 
ons set a seed-capsule : twelve other flowers were legi- 
timately fertilised with pollen from short-styled flowers ; 
and they set nine capsules, each including on an 
average 7 good seeds, ten being the maximum number 
ever produeed. Of the flowers on the short-styled 
plants, twelve were illegitimately fertilised with own- 
form pollen, and they yielded one capsule, including 
only 3 good seeds ; twelve other flowera were legiti- 
mately fertilised with pollen from long-styled flowers, 

■ Aud these produced nine capsules, but one was bad ; 



92 



HETEEOSTYLED DIMOBPHIO PLANTS Chap. Ul. 



the eight good capsules tjontained on an average 8 
good seeda each. Judging from the number of seeda 
per capsule, the ftjrtility of the two legitimate to that 
of the two illegitimate unions is as 100 to 20. 

The numerous flowers on the eleven long-atyled 
plants under the net, which were not fertilised, produced 
only three capsules, including 8, 4, and 1 good seeds. 
Whether these three capsules were the product of acci- 
dental legitimate fertilisation, owing to the branches 
of the plants of the two forms interlocking, I will not 
pretend to decide. The single long-styled plant which 
was left imcovered, and grew close by the uncovered 
short-styled plant, produced five good pods; but it 
was a poor and small plant, 

The flowers borne on the thirteen short-styled plants 
under the net, which were not fertilised, produced 
twelve capsules, containing on an average 5 ■ 6 seeds. 
As some of these capsules were very fine, and as five 
were borne on one twig, I suspect that some minute 
insect had accidentally got under the net and had 
brought pollen from the other form to the flowers 
which produced this little group of capsules. The one 
uncovered shorl^styled plant which grew close to the 
uncovered long-styled plant yielded twelve capsules. 

Erom these facts we have some reason to believe, as 
in the case of L. gi'andifiorum, that the short-styled 
plants are in a shght degree more fertile with their 
own pollen than are the long-styled plants. Anyhow 
we have the clearest evidence, that the stigmas of each 
form require for full fertility that pollen irom the sta- 
mens of corresponding height belonging to the opposite 
form should be brought to them. 

midehrand, in the paper lately referred to, confirms 
my results. He placed a short-styled plant in his 
house, and fertilised about 20 flowera with their own 



I 

I 



P'Chap. ni. LINUM PEBENNE. 93 

pollen, and abuut 30 with pollen from another plunt 
belonging to the same form, and these 50 flowers did 
not Bet a single capsule. On the other hand he ferti- 
lised abont 30 flowers with pollen from the long-styled 
form, and these, with the exception of two, yielded 
capsules, containing good seeda. 

It is a singular fact, in contrast with what occurred 
in the case ot L. grandiflorum, that the pollen-grains of 
both forms of L. ji&enne, when placed on their own- 
form stigmas, emitted their tubes, though this action 
did not lead to the production of seeds. After an 
interval of eighteen hours, the tubes penetrated the 
Btigmatic tissue, but to what depth I did not ascertain. 
[n this case the impotence of the pollen-grains on their 
own stigmas must have been due either to the tubes 
not reaching the ovules, or "to their not acting pro- 
perly after reaching them. 

The plants both of L.perenne and grandiflorum grew, 
as already stated, with their branches interlocked, and 
with scores of flowers of the two forms close together ; 
they were covered by a rather coarse net, through which 
the wind, when high, passed ; and such minute insects 
as Thrips could not, of course, be excluded ; yet we have 
seen that the utmost possible amount of accidental fer- 
tilisation on seventeen long-styled plants in the one 
case, and on eleven long-styled plants in the other, 
resulted in the production, in each case, of three 
poor capsules ; so that when, the proper insects me 
excluded, the wind does hardly anything in the way of 
carrying pollen from plant to plant. I allude to this 
fact because botanists in speaking of the fertilisation 
of various flowers, often refer to the wind or to insects 
as if the alternative were indifferent. This view, ac- 
cording to my experience, is entirely erroneous. When 
the wind is the agent in carrying pollen, either from 





84 



HETEROSTYLED DIMOBPHIC PLANTa. Ch*p. 1 



one sex to the other, or from hermaphrodite to hen 
phrodite, we can recognise structure as manifestly ad4 
apted to its action as to that of insects when these a 
the carriers. We see adaptation to the wind in the ii 
coherence of the pollen, — in the inordinate quantit 
produced (as in the Coniferas, Spinage, &e.}, — in thei| 
(Iiingling anthers well fitted to shake out the pollen,— 
in the absence or small size of the perianth,- 
protrusion of the stigmas at the period of fertilisation,* 
— in the flowers being produced before they are hiddeu 
by the leaves, — and in the stigmas heiug downy or 
plumose (as in the Gramincje, Doclts, Ac), so as to 
secure the chance-blown grains. In plants which are 
fertilised by the wind, the flowers do not secrete nectar, 
their pfillen is too incoherent to be easily collected by J 
insecta, they have not bright-coloured corollas to serve 
as guides, and they are not, aa far as I have seen, 
visited by insects. When insects are the agents of fer- 
tilisation (and this is incomparably the more frequent 
case with hermaphrodite plants), the wind plays no 
part, but we see an endless number of adaptations to 
ensure the safe transport of the pollen by the living 
workers. These adaptations are most easily recognised 
in irregular flowers; but they are present in regulai 
flowers, of which those of Linum offer a good instance, 
as I will now endeavour to show. 

I have already alluded to the rotation of each sepa- 
rate stigma in the long-atyled form of Linum perenne. 
In both forms of the other heterostyled species and in 
the homostylcd species of Linum which I have seen, 
the Btigmatic surfaces face the centre of the flower, 
with the furrowed backs of the stigmas, to which the 
styles are attached, facing outwards. This is the case 
with the stigmas of the long-styled flowers of L. 
perenne whilst in bud. But by the time the flonen ■ 



I 



Chat. nL UXUM F^UUiSK. 99 

hiire expended, tike fire stagnus twist roand so as to 
&ce the cirramfexcnoe, owing to the toision of that 
part of the style wiiicb lies beoeath the stigma. I 

sboald state that the Ave stigmas do not always tam 
round completely, twa or three aometimes being 
only obliquely uctwoiils. Hy obserrAtioos were made 
diuiug October ; and it is not improbable that earlier 
in the season the toraon would have been more com- 
plete ; for after two or three cold and wet days the 
movement was very imperfectly performed. The 
Sowers should be examined shortly after their ex- 
pansion, as their duration is brief; as soon as they 
begin to wither, the styles become spirally twisted 
all together, the original petition of the parts being 
thus lost. 

He who urill compare the structure of the whole 
flower in both forms of L, perenne and grandijlorum, 
and, as I may add, of L.fiavam, will not doubt about 
the meaning of this torsion of the styles in the one 
form alone of L. perenne, as well as the meaning of 
the divergence of the stigmas in the short-styled 
form of all three species. It is absolutely necessary 
as we know, that insects should carry pollen from 
the flowers of the one form reciprocally to those ol 
the other. Insects are attracted by five drops of 
nectar, secreted exteriorly at the base of the sfiimens, 
so that to reach these drops they must insert their 
proboscides outside the ring of broad filaments, be- 
tween them and the petals. In the short-styled form 
of the above three species, the stigmas face the axis of 
the flower; and had the styles retained their original 
upright and central position, not only would the stig- 
mas have presented their backs to the insects which 
sucked the flowers, but their front and fertile surfaces 
would have been separated from the entering insects 



I 



98 HETEIIO&TYLED DIMOKPHIO PLANTS. Ohap. I 

by the ring of broad filaments, and would never bare 
received any poUen. As it is, the stylea diverge 
and pass out between the filaments. After this move- 
ment the short stigmas lie within the tube uf the 
corolla ; and their papilloua surfaces being now turned, 
upwards are necessarily brushed by eveiy entering 
insect, and thus receive the required pollen. 

In the long-styled form of L. grandiflorum, the 
almost parallel or slightly diverging anthers and 
stigmas project a little abuve the tube of the somewhat 
concave flower ; and they stand directly over the open 
space leading to the drops of nectar. Consequently 
when insects visit the flowers of either form (for the 
stamens in this species occupy the same position in 
both forms), they will get their foreheads or proboscidea 
well dusted with the coherent pollen. As soon as they 
visit the flowers of the long-styled form they will 
ve pollen on the proper surface of the 
. stigmas ; and when they visit the sbott- 
styled flowers, they will leave pollen on the upturned 
stigmatic surfaces. Thus the stigmas of both forms 
will receive indifferently the pollen of both forms ; 
but we know that the poUen alone of the opposite form 
causes fertilisation. 

In the case of L. perenne, affairs are arranged more 
perfectly ; for the stamens in the two forms stand at 
different heights, so that pollen from the anthers of 
the longer stamens will adhere to one part of an 
insect's body, and will afterwards be brushed off by 
the rough stigmas of the longer pistils ; whilst pollen 
from the anthers of the shorter stamens will adhere to 
a different part of the insect's body, and will afterwards 
be brushed off by the stigmas of the shorter pistils ; 
and this is what is required for the legitimatu fertilisa- 
tion of both forms. The corolla of L. perenne is more 



4 



Chap, III. 



LIKUM PEKENNE. 



expanded th&a that oi L.^t-andijlorum, aoi the atigmaa 
of the long-styled form do nut diverge greatly iiom 
one another; nor do tlie stamens of either form. 
Hence insects, especially rather small ones, will not 
insert their proboscides between the stigmas of the 
long-styled form, nor between the anthers of either 
form (Fig. 5), but will strike against them, at nearly 
right angles, with the backs of their head or thorax. 
Now, in the long-styled flowers, if each stigma did 

I'ig. 5. 




not rotate on its a3ds, insects in yisitiug them would 
strike their heads against the backs of the stigmas ; a^ 
it is, they strike against that surface which is covered 



• 1 neglected to get rtrawiogB 
maJofioin fresh flowarBnftlie two 
furmg. Bat Mr Fitch baa mada In the pro^iti 
the abate eketah of u longatylcd j-iarta. 
Uower from driod Bpecimoas aad 



88 HETEBOSTTLED DIMOEPHIO PLANTa Oaip. m | 

with papilliE, witli their heads already charged with J 
pollen from the stamens of corresponding height' < 
borne by the flowers of the other form, and legitimate 
fertilisation is thus ensured. 

Thus we can understand the meaning of the torsion 
of the styles in the long-styled flowers alone, as well 
as their divergence in the ahort-styled flowers. 

One other point is worth notice. In botanical works 
many flowers are said to be fertilised in the bud. This 
statement generally rests, as far as I can discover, on 
the anthers opening in the bud; no evidence being 
adduced that the stigma is at this period mature, or 
that it is not subsequently acted on by pollen brought 
from other flowera. In the case of CejJialanlhera 
{frandiflora I have shown* that precocious and partial 
self-fertilisation, with subsequent full fertilisation, is 
the regular course of events. The belief that the 
flowers of many plants are fertilised in the bud, that 
is, are perpetually seK-fertilised, is a most effectual bar 
to understanding their real structure. I am, however, 
far from wishing to assert that some flowers, during 
certain seasons, are hot fertilised in the bud ; for I 
have reason to believe that this is the case. A good 
observer,t resting his belief on the usual kind of 
evidence, states that in Linum Austriasum (which is 
heterostyled, and is considered by Planchon as a variety 
of X. peretiiie) the anthers open the evening before 
the expansion of the flowers, and that the stigmas ars 
then almost always fertiKsed. Now we know positively 
that, so far from Linum perenne being fertilised by its 
own pollen in the bud, its own pollen is as powerless 
on the stigma as so much inorganic dust. 

Linum fiavum. — The pistil of the long-styled fona 

• -Fertilianlion of Orchida,' t ' Etu.iea sur la G6igr. Bot, 

p. 108.— 2Dd edil. 1877, p. Ml. H. Leooq, 185(1, torn. v. p. 3Bo. 



I 



IP. IIL LINUM FLAVUM. 99 

of this species is nearly twice as long as that of 
the short-styled; the stigmas are longer and the 
papillte coarser. In the short-styled form the stigmas 
diyerge and pass out between the filaments, as in the 
previons species. The stamens in the two forms differ 
in length; and, what is singular, the anthers of the 
longer stamens are not bo long as those of the other 
form ; so that in the short-styled form hoth the stigmas 
and the anthers are shorter than in the long-styled , 
form. The pollen-grains of the two forms do not differ 
in size. As this species ia propagated hy cuttings, 
generally all the plants in the same garden helong to 
the same form. I have inquired, but have never heard 
of its seeding in this country. Certainly my own plants 
never produced a single seed as long as I possessed 
only one of the two forms. After considerable search 
I procured both forms, but from want of time only a few 
experiments were made. Two plants of the two forma 
were planted some way apart in my garden, and were 
not covered by nets. Three flowers on the long-styled 
plant were legitimately fertilised with pollen from the 
short-styled plant, and one of them set a fine capsule. 
No other ca2>sules were produced hy this plant. Three 
flowers on the short-styled plant were legitimately 
fertiHsed with pollen from the long-styled, and all 
three produced capsules, containing respectively no 
less than 8, 9, and 10 seeds. Three other flowers on 
this plant, which had not been artificially fertilised, 
produced capsules containing 5, 1, and 5 seeds; and 
it is quite possible that pollen may have been 
brought to them by insects from the long-styled plant 
growing in the same garden. Nevertheless, as they 
did not yield half the number of seeds compared 
with the other flowers on the same plant which had 
been artificially and legitimately fertilised, and as the 



100 HETEBOaTYLED DIMOBPHIO PLANTS. Ohap. I 

Bhort-styled plants of the two previons specie 
rently evince some aligKt capacity for fertilisation with 
their own-form pollen, these three capsules may have 
been the product of self-fertilisation. 

Besides the three species now described, the yellow- 
flowered L. coryrnbiferum is certainly heterostyled, 
as is, according to Planchou," L. salsoloides. This 
botanist is the only one who seems to have inferred 
that heterostylism might have some important func- 
tional bearing. Dr. Alefeld, who has made a special 
study of the genus, saysf that about half of the sixty- 
five species known to him are heterostyled. This is 
the case with L. Irigynuin, which differs so much from 
the other species that it has been formed by him into 
a distinct genus. t According to the same author, 
none of the species which inhabit America and the 
Cape of Grood Hope are heterostyled. 

I have examined only three homostyled species, 
namely, L. usitatisiimum, angustifolium. and eatharti- 
sum. I raised 111 plants of a variety of the first-named 
species, and these, when protected under a net, all 
produced plenty of seed. The flowers, according to 
H. Muller,§ are frequented by bees and moths. With 
respect to L. caiharticum, the same author shows that 
the flowers are so constructed that thoy can freely 
fertilise themselves ; but if visited by insects they 
might be cross-fertilised. He has, however, only once 
seen the flowers thus visited during the day ; but it 



1 
t 



• Honker's ' LondoD Journal oC 
BotftnT,' 1848, vol. vii. p, 174. 

t "Sot. Zeilung,' Sep. IS*, 
1S63, p. 2ei. 

} It IB not tmprohHbfa thut thu 
allied genus, Hugnnia, ia hetGro- 
3tyl<:<l. for one epei^ioB ia Biiid 
by FlBneiion (Hootet'8 ' Loudon 



Jnornal of Botanj," 1848, vol. L 
»ii. p. 525) to ba provided wiA 1 
" gtaminibua esSBrtis;'' anotluff | 
vith " atylia atnmiuibua lougiorl 
bus," and anotlier baa "ataiiiiiui 
S, mnjoIl^ atylnskmgGauperantin.' 

g 'Die Bcrrucbluiif; dei IJln- J 
men.' in., p. I6S. 



PULMONABIA OFFICINALIS. 



101 



may be suspected tliat they are frequented duriQg 
the night by small moths for the sake of the five 
minute drops of nectar secreted. Lastly, L. Lemsii 
is said by Planchon to bear on the same plant flowers 
with stamens and pistils of the same height, and 
others with the pistils either longer or shorter than 
the stamens. This case formerly appeared to me an 
extraordinary one ; but I am now inclined to believe 
that it is one merely of great variability." 



PULMOSARIA (BOIIAGINE^). 

Pidmonaria ojieinalis. — Hildebrand has published t 
a full account of this heteroatyled plant. The pistil 
of the long-styled form is twice as long aa that of the 
Bhort^styled ; and the stamens differ in a corresponding, 
though converse, manner. There is no marked dif- 
ference in the shape or state of surface of the stigma 
in the two forms. The pollen-grains of the short- 
styled form are to those of the long-styled as 9 to 7, 
or as 100 to 78, in length, and aa 7 to 6 in breadth. 
They do not differ in the appearance of their contents. 
The corolla of the one form differs in shape from that 
of the other in nearly the same manner as in Primula ; 
but besides this difference the flowers of the short- 
Btyled are generally the larger of the two. Hilde- 
brand collected on the Siebengebirge, ten wild long- 
styled and ten short-styled plants. The former bore 
289 flowers, of which 186 (i.e. 64 per cent.) had set 
fruit, yielding 1-88 seed per fruit. The ten short- 
atyled plants bore 373 flowers, of which 262 (i.e. 



• Plunchon, in Uijoter's ' Iion- 
I Alia Journal of liolunj,' ISiS, vnl. 
»iL p. 175. Soe OQ IhlB aubjecl 
* H (iraj, in ' American Jouniul p. 13. 



uxvi. Sept. 18G3, 
Bot. ZeituDg,' 18G5, Jun. la 



I 



102 HETEBOSTYLED DIJIOBPHIO PLANXS. Cair. I 

70 per cent.) had set fruit, yielding 1'8G seed pe*' 
fruit. So that the short-styled plants produced many 
more flowers, and these set a rather larger proportion 
of fruit, but the fruits themselves yielded a slightly 
lower average number of seeds than did the long- 
styled plants. The results of Hildebrand's experiments 
on the fertility of the two forms are given in the fol- 
lowing table : — 

Tablb 19. 
Pulmonaria officinalis (from Ilildehrand), 





ATertiga 

o(Sc^ 
petFrutl, 


-.■^rri.&.'^r""'*"";} " 1 '» 1 '■»» 


Lon?-slrIfld flowers, 1* by onrn-pollen,; 
aod 16 bj pollen of other plant of same 
form. I Uegiti male union . . . .] 


30 








Short-stfled flowen, by pollen of loDg-1 
styled. Legitimate union ... J 


18 U 1 1-57 

1 


Short-slTled flowers, 11 by own pollen,] 
14 by polUu of other plant of same 
form, illegitimnte oniuD ... .J 


25 









In the summer of 1864, before I had heard of Hilde- 
brand's experiments, I noticed some long-styled plants 
of this species (named for me by Dr. Hooker) growing 
by themselves in a garden in Surrey; and to my 
surprise about half the flowers had set fruit, several 
of which contained 2, and one contained even 8 seeds. 
These seeds were sown in my garden and eleven 
seedlings thus raised, all of which proved long-styled, 
in accordance with the usual rule in such eases. Two 
years afterwards the plants were left uncovered, no 



I 
I 



, 10 W 



rOBAi". m. FULMONAKIA OFFICmALIS. 

other plant of the s 



103 



f grtrdui 



1 genus grown 
and the flowers were visited by many bees. They set 
&n abundance of seeds ; for instimee, I gathered from n 
single plant rather less than half of the seeds which it 
had produced, and they numbered 47. Therefore this 
illegitimately fertilised plant must have produced aboul 
100 seeds ; that is, thrice aa many as one of the wild 
long-styled plants collected on the Siebengebirge bj- 
Hildebrand, and which, no doubt, had been legitimately 
fertilised. In the following year one of my plants 
was covered by a net, and even under tliesa un- 
favourable conditions it produced spontaneously a 
few seeds. It should be observed that as the flowers 
stand either almost horizontally or hang considerably 
downwards, pollen from the abort stamens would be 
' likely to fall on the stigma. We thus see that the 
EngiisU long-styled plants when illegitimately ferti- 
lised were highly fertile, whilst the German plants 
similarly treated by Hildebrand were completely 
sterile. How to account for this wide discordance in 
onr resnlta I know not. Hildebrand cultivated hia 
plants in pots and kept them for a time in the house, 
whilst mine were grown out of doors ; and he thinks 
that this difference of treatment may have caused 
the difference in our results, Eut this docs not appear 
to me nearly a sufficient cause, although his plants 
were slightly less productive than the wild ones growing 
on the Siebengebirge, My plants exhibited no ten- 
dency to become equal-styled, so as to lose their proper 
long-styled character, as not rarely happens under 
cultivation with several hetcrostyled species of Pri- 
mula ; but it would appear that they had been greatly 
affected in function, either by long-continued cultiva- 
tion or by some other cause. We shall see in a 
future chapter that heterostyled plants illegitimately 



I 



104 HETEEOSTYLED DIMOltpmO PT-AJTrS. CHiP. m 

iertiliscd during several successive generations some- 
times become more self-fertile ; and this may have 
been the case with my stock of the present species 
of Fulmonaria ; but in this case we must assume 
that the long-styled plants were at first sufficiently 
fertile to yield some seed, instead of being absolutely 
self-sterile like the German plants. 

Pidinonaria an^Ms/t/o^ta.— Seedlings of this plantj 
raised from plants groiving wild in the Isle of Wight, 
were named for me by Dr. Hooker. It is so closely 
allied to the last species, differing chiefly in the shape 
and spotting of the leaves, that the two have been con- 
sidered by several eminent botanists — ^for instance, 
Bentham — as mere varieties. But, as we shall presently 
see, good evidence can bo assigned for ranking them 
as distinct. Owing to the doubts on this head, I tried 
whether the two would mutually fertilise one another. 
Twelve short-styled flowers of P. anguslifolia were 
legitimately fertilised with pollen from long-styled 
plants of P. offidnalis (which, as we have just seen, are 
moderately self-fertile), but they did not produce a 
single fruit. Thirty-six long-styled flowers of P. 
angustifdia were also illegitimately fertilised during 
two seasons with pollen from the long-styled P. 
officinalis, but all these flowers dropped off unim- 
pregnated. Had the plants been mere varieties of 
the same species these illegitimate crosses would 
probably have yielded some seeds, judging from my 
success in illegitimately fertilising the long-styled 
flowers of P. officinalis ; and the twelve legitimate 
crosses, instead of yielding no fruit, would almost 
3ertainiy have yielded a considerable number, namely, 
about nine, judging from the results given in the fol- 
lowing table (20). Therefore P. officinalis and angusti- 
folia appear to be good and tliatinct species, in 



I 



PULMOJIAEIA ANGlTSTrFOLIA. 105 

conformity with other important functional differences 
between them, immediately to be degcribed. 

The long-styled and short-styled flowers of P. angua- 
tifolia differ from one another in structure in nearly 
the same manner as those of P, officinalis. But in the 
accompanying fignre a alight bulging of the corolla 

Fig. 6. 




in the long-styled form, where the anthcra are seated, 
has been overlooked. My son William, who examined 
a large number of wild plants in the Isle of Wight, 
observed that the corolla, though variable in size, was 
generally larger in the loug-styled flowers than in the 
short-styled ; and certainly the largest corollas of all 
were found on the long-styled plants, and the smallest 
on the short-styled. Exactly the reverse occurs, ac- 
cording to Hildebrand, with P. officinalis. Both the 
pistils and stamens of P. angustifolia vary much in 
length ; so that in the short-styled form the distance 
between the stigma and the anthers varied from 119 
to 65 divisions of the micrometer, and in the long- 
^tyled from 115 to 112. From an average of seven 



106 HETEHOSTYLED DIMORPHIC PLANTS. Chap. Ul 

measurements of each form tlie distance between these 
organs in the long-styled is to the same distance in 
the short-styled form as 100 to 69 ; so that the atigma 
in the one form docs not stand on a level with tlie 
anthers in the other. The long-styled pistil is some- 
times thrice as long as that of the short-styled ; but 
from an average of ten measurements of both, its 
length to that of the short-styled was as 100 to 56. 
The stigma varies in being more or less, though 
slightly, lobed. The anthera also vary much in 
length in both forms, but in a greater degree in the 
long-styled than in the short-styled form; many in 
the former being from SO to 63, and in the latter 
from 80 to 70 divisions of the micrometer in length. 
From an average of seven measurements, the short- 
styled anthers were to those from the long-styled as 
100 to 91 in length. Lastly, the pollen-grains from 
the long-styled flowers varied between 13 and 11 "5 
divisions of the micrometer, and those from the short- 
styled between 15 and 13. The average diameter of 
25 grains from the latter, or shorl>-styled form, was 
to that of 20 grains from the long-styled as 100 to 
91. We see, therefore, that the pollen-grains from 
the smaller anthers of the shorter stamens in the long- 
styled form are, as usual, of smaller size than those 
in the other form. But what is remarkable, a larger 
proportion of the grains were small, shrivelled, and 
worthless. This could be seen by merely comparing 
the contents of the anthers from several distinct plants 
of each form. But in one instance my son found, by 
counting, that out of 193 grains from a long-styled 
flower, 53 were bad, oi 27 per cent. ; whilst out of 
265 grains from a short-styled flower only 18 were 
bad, or 7 per cent. From the condition of the pollen 
in tlie long-styled form, and from the extreme varia- 



I'ULMONARIA ANGUSTIFOLIA. 



107 



bility of all the organs in botli forms, we may perhaps 
suspect that the plant is undergoing a change, and 
tending to become dioscious. 

My son collected in the Isle of Wight on two occa- 
sions 202 plants, of which 125 were long-styled and 
77 short-styled ; so that the former were the more 
numerous. On the other hand, out of 18 plants raised 
by me from seed, only 4 were long-styled and 14 
short-styled. The short-styled plants seemed to my 
son to produce a greater number of flowers than the 
long-styled ; and he came to this conclusion before a 
similar statement had been published by Hildebrand 
with respect to P. officirkaUs. My son gathered ten 
branches from ten dilferent plants of both fonns, and 
found the number of flowers of the two forms to be as 
100 to 89, 190 being short-styled and 169 long-styled. 
With P. officinalis the difference, according to Hilde- 
brand, is eyen greater, namely, as 100 flowers for the 
short-styled to 77 for the long-styled plajits. The 
following table shows the results of my experi- 
meuta : — 

Table 20. 
I' ulmunaria angual^fvlia. 



..,.,..,..„.., 




Number 

Frniu 
prWa,rf. 


Avwnge 
NunHsrol 

BwdB 
per f-niit. 


Long-«lTled flowers, by pollen of short- 
rtylei Legilim«e unioD . . . . 


18 


8 


2-[l 


Long.Mityled fiowerg, by awn-form pollen. 


18 


» 


• 


ShDii-BtTled flowers, b; pollen of long- 
rtjlri. Legitimate union . . . . 


,. 


15 


a-eo 


Sbort-«tyl«d flowers, by own-form pollen. 
Ul^ifflate naiuu 


" 


7 


1-88 



108 HETEBOBTTLED DIMOHPHIC PLANTS. Cnju-. 1 

We aes in this table tliat the fertility of 
legitimate unions to that of the two illegitimate 
together is as 100 to 35, judged by the proportion of 
flowers which produced fruit ; and as 100 to 32, judged 
by the average number of seeds per &uit. But the 
small number of fruit yielded by the 18 long-styled 
flowers in the first line was probably accidental, and 
if 30, the difference in tne proportion of legitimately 
and illegitimately fertilised flowers which yield fruit 
really greater than that represented by the ratio of 
100 to 35. The 18 lon^-styled flowers illegitimately 
fertilised yielded no seeds, — not even a vestige of 
Two long-styled plants which were placed under a net 
produced 138 flowers, besides those which were arti- 
ficially fertilised, and none of these set any fruit ; nor 
did some plants of the same form which were pro- 
tected during the next summer. Two other long- 
styled plants were left uncovei-ed {all the short-styled 
plants having been previously covered up), and 
humble-bees, which had their foreheads white with 
pollen, incessantly visited the flowers, so that their 
stigmas must have received an abundance of irollen, 
yet these flowers did not produce a single fruit. We 
may therefore conclude that the long-styled plants 
are absolutely barren with their own-form polh 
though brought from a distinct plant. In this re- 
spect they differ greatly from the long-styled English, 
plants of P. officinalis which were found by me to 
be moderately self-fertile ; but they agree in their 
behaviour with the German plants of P. o^iciTiaJi* 
experimented on by Hildebrand. 

Eighteen short-styled flowers legitimately fertilised 
yielded, as may be seen in Table 20, 15 fruits, each 
an average 2 " 6 seeds. Four of these fruita 
ined the highest possible number of seeds, namely 



I 
I 



CuAi>. III. PULMONARLA ANGUSTIFOLIA. 109 

4, and four other fruits contained each 3 seeds. The 
12 iUegitimately fertilised short-styled flowers yielded 
7 fruits, including on an average 1 ' 8C seed ; and one 
of these fruits contained the maximum number of 
4 seeds. This result is very surprising in contrast 
with the absolute barrenness of the long-styled flowers 
when illegitimately fertilised ; and I was thus led to 
attend carefully to the degree of self-fertility of the 
short-styled plants. A plant belonging to this form and 
covered by a net bore 28 flowers besides those which 
had been artificially fertilised, and of all these only 
two produced a fruit each including a single seed. This 
high degree of aelf-sterility no doubt depended merely 
on the stigmas not receiving any pollen, or not a suffi- 
cient quantity. For after carefully covering all the 
long-styled plants in my garden, several short-styled 
plants were left exposed to the visits of humble-bees, 
and their stigmas will thus have received plenty of 
short-styled pollen; and now about half the flowers, 
thus illegitimately fertilised, set fruit. I judge of this 
proportion partly from estimation and partly from 
■having examined three large branches, which had borne 
31 flowers, and these produced 16 fruits. Of the fruits 
produced 233 were collected (many being left un- 
gathered), and these included on an average 1'82 
seed. No less than 16 out of the 233 fruits included 
the highest possible number of seeds, namely 4, and 
31 included 3 seeds. So we see how highly fertile 
these short-styled plants were when illegitimately fer- 
tiliHed with their own-form pollen by the aid of bees. 

The great difference in the fertility of the long and 
short-styled flowers, when both are illegitimately fer- 
tilised, is a unique case, as far as I have observed with 
het«rostyled plants. The long-styled flowers when thus 
fertilised are utterly barren, whilst about half of the 



110 



HETEROSTYLED DIMOBPHIO PLANTS. Chap. ] 



short-styled ones produce capsules, and these include a 
little above two-thirda of the number of seeds yielded 
by them when legitimately fertilised. The sterility of 
the illegitimately fertilised long-styled flowers ia prob- 
ably increased by the deteriorated condition of their 
pollen ; nevertheless this pollen was highly efficient 
when applied to the stigmas of the short-styled flowera. 
^V'ith several species of Primula the shori>styled 
flowers are much more sterile than the long-styled, 
when both are illegitimately fertilised ; and it is a 
tempting view, as formerly remarked, that this greater 
sterility of the short-styled flowers is a special adapta- 
tion to check self-fertilisation, as their stigmas are 
eminently liable to receive their own pollen. This view 
ia even still more tempting in the case of the long- 
styled form of JAnum ffrandi/tomm. On the other 
hand, with Pidmonaria anguatifoUa, it is evident, from 
the coroUa projecting obliquely upwards, that pollen 
is much more likely to fall on, or to be carried by 
insects down to the stigma of the short-styled than of 
the long-styled flowers; yet the short-styled instead 
of being more sterile, as a protection against self-ferti- 
lisation, are far more fertile than the long-styled, 
when both are illegitimately fertilised. 

Pulmonaria azurea, according to Hildebrand, is not 
heteroatyled.* 

Prom nn eanmiiiBtiDn of dried flowers of Ajnsinckia ipeetabUU, 
Bent me by Prof. Asa Gray, I formerly thought that this plant, 
a member of the Eoragines, was heterostyled. The pistil 
varies to an extraordinary degree in length, being in some 
specimens twice as long as in others, and the point of insertion 
of the stamens likewise varies. But on raising many plants 
from eeod, I Boon became convinced that the whole case was 
one of mere variability. The first-formed flowers are apt (a 



I 
I 



' Dlo OeBcLleolitei-Verlheilung bti den Pflnnran,' 1SC7, p. 37, 



Chap. in. POLYOONUM FAGOPYEUU. 



Ill 



have siamona somewhat arrested in development, with very 
little pollen in their anthers ; and in ench Bowers the stigma 
projeeta above the anthers, wliilst generally it stanils below anti 
Bometimes on a level with them. I could detect no diiForence 
In the size of the pollen^ain or in the straoture of the stigma 
in the plants which differed raoat in the above rospect-s; and alt 
of them, when protected from the access of inaects, yielded 
plenty of seeds. Again, from statements made hy Vaucher, and 
&am a hasty inspection, I thought at lirst that the allied 
Anchwa arvengis and£c'j!um vulgaiewere heterostyled, bnt soon 
saw my error. From information given me, I examined dried 
flowers of another member of the Boragincw, AmeJiia hinpidis- 
tima, coUecfed from several sites, and though the corolla, to- 
gether with the included oi^na, differed much in length, there 
was no sign of heterostylism. 



Polygonum FAGorvRUM (Polygonace^). 

Hildebrand has slionii that this plant, the common 
Buck-wheat, ia heterostyled.* In the long-styled form 
(Fig. 7), the three stigmas project considerably above 
the eight short stamens, and stand on a level with the 
anthers of the eight long stamens in the short-styled 
form; and so it ia conversely with the stigmas and 
Htamena of this latter form. I could perceive no differ- 
ence in the stmctuie of the stigmas in the two forms. 
The pollen-grains of the short-styled form are to those 
of the long-styled as 100 to 82 in diameter. This plant 
ia therefore without doubt heterostyled. 

I experimented only in an imperfect manner on 
the relative fertility of the two forms. Short-styled 
flowers were dragged several times over two heads 
of flowers on loug-atyled plants, protected under a net, 
which were thus legitimately, though not fully, ferti- 
lised. They produced 22 seeds, or II per flower-head. 

Three flower-heads on long-styled plants received 



' Dio Gcficliloolilcr-Vevtliuitung,' So., 1867, p. 3i. 



112 HETEE08TYLED DIMOBPHIO PLANTS. Chap. IlL 

pollen in the same manner from other long-styled 
plants, and were thus illegitimately fertilised. They 
produced 14 seeds, or only 4' 66 per flower-head. 

Two flower-heads on short-styled plants received 
pollen in like manner from long-styled flowers, and 
were thus legitimately fertilised. They produced 8 



seeds, or 4 per flower-bead. 




Four heads on short-styled plants similarly received ' 
pollen from other sJiort-styled plants, and were thus 
illegitimately fertilised. They produced 9 seeds, or 
2 ■ 25 per fiower-head. 

The results from fertilising the Bower-heads in the 
above imperfect manner cannot he fully trusted ; but 
I may state that the four legitimately fertilised flower* 



'. in. POLYGONUM FAQOPTBUM. 113 

heads yielded on an average 7 "50 seeds per head; 
whereas the seven illegitimately fertilised heada 
yielded less than half the number, or on an average 
only 3 "28 seeds. The legitimately crossed seeds from 
the long-styled flowers were finer than those from the 
illegitimately fertUiaed flowers on the same plants, in 
the ratio of 100 to 82, as shown by the weights of an 
equal number. 

About a dozen plants, including both forma, were 
protected under nets, and early in the season they pro- 
duced spontaneously hardly any seeds, though at this 
■period the artificially fertilised flowers produced an 
abundance ; but it is a remarkable fact that later in 
the season, during September, both forms became 
highly self-fertile. They did not, however, produce 
so many seeds as some neighbouring uncovered plants 
which were visited by insects. Therefore the flowers 
of neither form when left to fertilise themselves late 
in the season without the aid of insects, are nearly so 
sterile as most other heterostyled plants. A large 
number of insects, namely 41 kinds as observed by H. 
Miiller," visit the flowers for the sake of the eight 
drops of nectar. He infers from the structure of the 
flowers that insects would^ie apt to fertilise them both 
illegitimately as well as legitimately; but he is mis- 
taken in sujiposing that the long-styled flowers cannot 
spontaneously fertilise themselves. 

Differently to what occurs in the other genera 
hitherto noticed. Polygonum, though a very large 
genus, contains, aa far as is at present known, only a 
single heterostyled species, namely the present one. 
H. Mflller in his interesting description of several 



' Die B«£nichluui;,' la, p. ITS, and ' Natura,' Jbd. 1, ISTj, p. IG6. 



114 HETEBOSTYLED DIMOHPHIC PLANTS. Cbat. i 

other species sbows that P. histttrla is so strongly pro- 

terandroTia (the anthers generally falling off before the 
stigmas lire mature) that the fluwera must be cross- 
fertilised by the mauy insects which visit them. Othei 
species bear much less conspicuous flowers which se- 
crete little or no nectjir, aud consequently are rarely 
visited by insects ; these are adapted for self-fertilisa- 
tion, though still capable of cross-fertilisatioiL Ac- 
cording to Delpino, the Polygonacea? are generally 
fertilised by the wind, instead of by insects as in the 
present genus. 



Leucossia Bcrnkttiajja (Thyme li^). 



Ab Pro£ Asa Gray has esprossed his belief* tLat tlijs epeciei 
and L. acaminat", as well ae some Bpeciea in the allied genna 
Drymispermuin, are dimorpliio or heterostyled, I procured 
from Kew, through the kiudnesB of Dr. Hooker, two dried 
flowerB of the former epeciBH, an inhabitant of the Friendly 
Islanda in tlie Pacific. Tlio pistil of the long-styled form is to 
that of the shorf^styled as 100 to 86 in length; the stigma 
projects juat above the throat of the corolla, and ia eurronnded 
by five anthers, the tips of wliich reach up almost to its base; 
and lower down, within the tubular corolla, five other and 
rather smaller anthers are seated. In the ehort-styled form, 
the stigma stands some way do^ the tube of the corolla, nearly 
oa a level with the lower antherB of the other form: it differs 
remarkably from the stigma of the long-styled form, in being 
more papillose, and iu being longer in the ratio of 100 to 60. 
The anthers of tlie upper stamens iu the short-atyled form are 
supported on free filaments, aud project above the throat of the 
ooroUa, whilst the anthers of the lower stamens are seated in 
the throat on a level with the uppt r stamens of the other form. 
The diametors of a considerable number of grains from both set* 
of anthers in both forms were measured, but they did not differ 
in any ttustwortliy degree. The moan diameter of twenty-two 



I 



' CflAP. m. MENYANTHES TEIFOLIATA, 



115 



I 
I 

I 



grains fram tliB short-styled flower was to thai of twenty-four 
grains from the long-styled, as 100 to 99. The authors of 
the upper stamens in the short-styleii form appeared to ha 
poorly developed, and oontainod a considerftbie number of 
BhriTeUed grains which were omitted in striking the almve 
average. Notwithstanding the fact of the pollen-grains from 
the two forms not difering in diameter in any appreciahla 
d^ree, there can hardly be a doubt from the great difference iu 
the two forma in the length of the pistil, and efipecially of the 
stigma, together with its more papillose condition in the short- 
styled form, that the present species is truly heierostylod. This 
case resembles that of Linum yrandijiorum, in which the sole 
diflerence tietween the two forms consists in the length of the 
pistils and stigmas. From the great length of the tubular 
corolla of Lencosmia, it is clear that the flowers are cross- 
ferMlised by large Lepidoptera or by honey-sucking birds, and 
the position of the stamens in two whorls one beneath the 
other, which is a character that I have not seen in any other 
heterostyled dimorphic plant, prolmbly serves to smear the 
ioserted organ thorougWy with pollen. 



Mkbtanthkh 



{Gkstiankjb). 



This plant inhabits marshes : my son 'William gathered 247 
flowers from so many distinct plants, and of these 110 were 
long-styled, and 137 short-styled. The pistil of the long-styled 
form is in length to that of the short^styled in the ratio of about 
3 to 2. Tlie stigma of the former, as my son obsorved, is deci- 
dedly larger than that of the short-styled ; but in both forms it 
"^^re much in size. The stamens of the sbort'Styled are almost 
double the length of those of the long-styled ; so that their 
anthers stand rather above the level of the stigina of the long- 
s^led form. The anthers also vary much in size, but seem 
oftfin to I* of lai'ger size in the short-styled flowers. My son 
made with the camera nrnny drawings of the pollen-grains, 
ftnd those from the short-styled flowers were in diameter in 
nearly the ratio of 100 to 84 to those from the long-styled 
flowers. I know nothing about the capacity for fectilisatjon in 
the two forms; but shoii-styled plants, living by themselves in 
the gardens at Ebw, have produced an abundance of cftpsulee, 
yet the seeds have never germinated ; and this looks as if tha 
ahort^styled form was sterile with its own pollen. 



116 HETEBOSTTLED DIMOBPHIO PLANTS. Chap. 1 

LDfHANIHEHUM IbDICTJH (GeNTUNBS). 

This plant is mentioned by Mr. Thwaitoa in hia Enumeratiim 
of the Plants of Ceylon as presenting two forms ; and he was bo 
kind Hfl to Bend me specimens preserved in spirits. The pistil 
of the long-styled form is nearly thrice as long (i.e. as 11 to 5) 
as that of tbe short-Btjled, and is very much thinner in the 
ratio of about S to 5. The foliaceons stigma is more expanded. 
and twice as large as that of the short^tyled form. In the 
latter the stamens are about twice as long as those of the long- 
Btyled, and their anthers are larger in the ratio of 100 to 70. 
Tlio pollen-grains, after having been long kept in Bpirita, were 
of the same shape and size in both forms. The ovules, accord- 
ing to Mr. Thwaites, are equally numerous (viz. from 70 to 80) 
in the two forms. 

ViLLARBIA [SP. ?] (QbHTIANB^). 

Fritz Miiller eent me from South Brazil dried flowers of this 
aquatic plant, which is closely alUed to Limnanthemum. In the 
long-styled form the stigma stands some way above the anthere, 
and the whole pistil, together with the ovary, is in length to 
that of the short^atyled form as about 3 to 2. In the latter 
form the anthers stand above the stigma, and the style is very 
short and thick; but the pietil varies a good deal in length, 
the stigma being either on a level with the tijM of the Beijals 
or considerably beneath them. The folioceous stigma in 
lbs long-styled form is larger, with the eipansions running 
farther down the style, than in the other form. One of the most 
remarkable differeneea between the two forma is that the anthers 
of the longer atamens in the short-styled flowers are conspicu- 
ously longer than those of the shorter stamens in the long-styled 
flowers. In the former the sub-triangular pollen-grains are 
larger; the ratio between their breadth (measured from one 
angle to the middle of the opposite side) and that of the groins 
from the long-styled flowers being about 100 to 75 Fritz 
Miiller also informs me that the pollen of the sbort-styled 
flowers has a bluish tint, whilst that of the long-atyled is yeUow. 
When we treat of Lyihrum sidicaria we shall find a strongly 
marked contrast in the colour of the pollen in two of the forms 

The throe genera, Menyanthea, Limnanthemum, and Villarsiu, 
now described, constitute a well-marked sub-tribe of the Gen- 
tiane^. All the species, as far as at present known, are heton); 
ityled, and all inhabit aquatic or sub-aquatic stations. 



rOaAP. IIL 



COEDIA. 



117 



I 



FORSYTHIA 811 BP EMS A (OLEAOE*). 

Professor Asa Gray states that tbe plants of tliis species grow- 
ing in the Botanic Gardens at Cambridge, U.S., are ehort-stjled, 
but that Sielrold and Zniccarini doscribe tlie long-styled form, 
and give figures of two forms; so that there can he little doubt, 
as he remarhs, about the plant being dimorphic' I therefore 
applied to Dr. Hooker, who sent me a dried flower from Japan, 
another from China, and another from the Botanic Gardens at 
Kew, The first proved to be long-atyled, and the other two 
Bhort-styled. In the loeg-etyled form, the pistil is in length 
to that of the short^yled as 100 to 38, the lobes of the etigma 
being a little longer (as 10 to S), hut narrower and leas diver- 
gent. This last character, however, may be only a temporary 
one. There seems to be no difference in the papillose condition 
of the two stigmas. In the short-styled form, the stamens are 
in length to those of the long-styled as 100 to 66, but tho anthers 
are ahorter in the ratio of 87 to 100 ; and this is mmsual, for 
when there is any difference in size between the anthers of the 
two forms, those from the longer stamens of tlie short-styled are 
generally tho longest. The pollen-grains from the shortr^tyled 
flowers are certainly larger, bnt only in a slight degree, than 
those from the long-styled, namely, as 100 to 94 in diameter. 
The short-styled form, which grows in the Gardens at Kew, has 
never there produced fruit. 

Fanytkia viridissima appears likewise to be heterostyled ; for 
Professor Asa Gray says that althongh the long-styled form 
alone grows in the gardens at Camtiridge, U.S., the published 
flguree of this species belong to the short-styled form. 



GoBDiA [bp.?] (Cobdiack«). 

Fritz Miiller sent me dried specimetis of tliis shrub, which he 
belieyeH to he heterostyled; and I have not much doubt tliat 
this is tho case, though the usual characteristic differences are 
not well pronounced in the two forms. Linum gTandijiorum 
■hows us that a plant may be heterostyled in function in the 
highest degree, and yet the two fonns may have stamens of 
equal length, and pollen-grains of equal sij;e. In the present 
■pedes of Conlia, the stamens of both forms are of nearly criii;il 

• 'The American NiitimJi=l,' July 1873, p. 122. 



118 HETEn08TYl,ED DIMOBPmC PLANTS. Obap. lU 

k'Qgth, tlioEo of the Bliort-st; led l«ing rather the loDgest; aud 
the Buthers of both are Reiit^ in the mouth of the corolla. Nor 
could I detect any difference iu the sisie of the pollen-grain b, 
when dry or after being soaked in water. The stigmaa of the 
long-etjled form ntand clear above the antherB, and the whole 
pistil is longer than that of the ahort-stylod, in about the ratio 
of 3 to 2. 

The stigmas of the Bhort-atjle<l form are seated beneath the 
anthers, and they are considerably shorter than those of the 
long'Etyled form. This latter diSerence is the moat important: 
one of any i«tweeii the two forms. 



GiLU (Ipomopsib) roLOHELLA y 



;*). 



(rOLKMONI- 



Professor Ana Gray remarlcs with respect to this plant 
tendency to dimorphism, of which there are traces, or perhaps 
rather incipient manifestations in various portions of the genus, 
is most marked in U. wii/regata.''* He sent me some dried 
flowers, and I proenred others from Kow. They differ greatly 
in size, some being nearly twice as long as others (vi 
17), 80 that it was not possible to compare, except by ealculati( 
the absolute length of the organs from different planta 
over, the relative position of the stigmas and anthers is voriaUst , 
in some long-styled flowers the stigmas and anthers were ex- 
serted only just beyond the throat of the corolla; whilst in 
others they were exserted as much as ^ of an inch, I suspect 
also that the pistil goes on growing for some time after the 
anthers have dehisced. Meverthelesa it ie posHit)Ie to class the 
flowers under two forms. In some of the long-ety!cd, the length 
of pistil to that of the short-Btyled was a.s 100 to 82; but this 
result was gained by reducing the size of the corollas to the 
same ecala In another pair of flowers the difference in length 
between the pistils of the two forms was certainly greater, but 
they were not actually measured. In the short^tyled flowors 
whether large or smalt, the stigma is seated low doivn within 
the tube of the corolla. The papillie on the long-styled stigma 
are longer than those on the short-siyled, ia tha ratio of 100 to 
40. The fllameats in some of tlw shnrt-stylod flowers were, to 
those of the long-styled, as 100 to 25 in length, the free, or 



I 



'Pruc. AniericiiQ Acad, of Aits nnJ Scioneca,' Juno H, 1870, p. 373 



r^BAP. III. FHLOX SU3ULATA. 1 19 

nnattiiched portiun being ulone measured ; but tMs ratio can- 
not be trusted, owing to the great variability of the stamens. 
The mean diameter of eleven pollea-graina from long-stjled 
flowers, and of twelve from the short-styled, was eiaotly the 
same. It follows from these Beyoral etftteraents, that the dif- 
ference in length and state of surface of the Btigmos in the 
flowers is the sole reliable eyidonce that tliis species is hetero- 
styled; for it would be rash to trust to the difl'erence in the 
length of the pistils, seeing how variable they are. I should 
have left the case altogether doubtful, had it not been for the 
observations on the following species; and these leave little 
doubt oa my mind that the present plant is truly heterostyled. 
Professor Gray informs me that in another species, O. corcmopi- 
folia, belonging to the same sectii>n of the genns^ he can see no 
sign of dimorphism. 

GlLIA (LepTOSIPHOK) MICEiKTHA. 

A few flowers sent me from Kew had been somewhat injured, 
BO that I cannot say anything positively with respect to the 
position and relative length of the organs in the two ibrms. 
But their stigmas difiered almost exactly in the same manner as 
in the last species ; the papillae on the Iong-ety!ed stigma being 
longer than those on the short-styled, in the ratio of lOO to 42, 
My son mcasnred nine pollen-gzuius from the long-styled, and 
the same number from the shortrstyled form ; and the mean 
diameter of the fonnor was to that of the latter as 100 to 81. 
Oonsidcring this difference, as well as that between the stigmas 
of the two forms, there can be ao doubt that this species is 
heterostyled. So probably is Oi/Ca nwlkauUs, which likewise 
belongs to the Leptosiphon section of the genus, for I hear from 
Professor Asa Gray that in some individuals the stylo is very 
long, with the stigma more or less exserted, whilst in others it 
is deeply included within the tube; the anthers being alwayi> 
seated in the throat of the corolla. 

Phlox subulata (Polbiioniaob«). 
Professor Asa Gray informs me that tlie greater number of 
the species in tliis genus have a long pistil, with the stigma 
more or less exserted ; whilst several other species, especially the 
annnals, liave a short pistil seated low down within the tube o[ 
(he corolla. In all the species the anthers ore arranged one 



120 UETEKOSTYLED DIMOKPHIO PLA^TTS. Coaf. iM 

below the other, the uppermost just protruding from the throM' 
of tho corolla. In Phlox subiiliitu alone he has "seen both long 
and short styles; and here the ehort^Btjled plant has (irreHpeo- 
tiva of this character) been described as a distinct species (P. 
niBoHs, P. Hentzii), and is apt to hare a pair of otuIgs in each 
ceil, while the long-styled F. aubulala rarely ahowa more than 
one,"* Some dried flowers of both forms were sent me bj him, 
and I received others from Eew, but I have failed to make 
out whether the Hpecies ia heterostjled. In two flowers of 
nearly equal size, the pistil of the long-styled, form was twice as 
long as that of the short^tjled ; hut in other cases the differ- 
ence was not nearly so great. The stigma of the long-styled 
pistil stands neorly in the throat of the corolla; whilst in the 
short-stjled it ia placed low down— sometimes very low down 
in the tube, for it varies greatly in position. The stjgma is 
more papillose, and of greater ieugth (in one instance in tha 
ratio of 100 to 67), in the short-styled flowers than tn thA 
long-styled. My son measured twenty pollen-grains from « 
short-styled flower, and nine from a long-styled, and the 
former were in diameter to the latter as 100 to 93; and this 
diflarence accords with the behef that the plant is heter»- 
styled. But the grains from the short-styled varied much in 
diameter. He afterwards meoflured ten grains from a distinct 
long-styled flower, and ten from another plant of the same form, 
and these grains differed in diameter in the ratio of 100 to 90. 
The mean diameter of these two iota of twenty grains was to 
that of twelve grains from another short^tyled flower as 100 to 
7S : here, then, the grains from the short-styled form were c(m- 
aiderably smaller than those from the long-styled, which is the 
reverse of what oocurred in the former instance, and of what iB 
the general rule with heterostyled plants. The whole case ia 
perplexing in the highest degree, and will not he imderstood 
until experunenta are tried on living plants. The greater length, 
and more papillose conditioa of the stigma in the short^styled 
than in the long-styled flowers, looks as if the plant was hetero- 
styled ; for we know that with some species — for instance. Lea- 
cosmia and certain EuhiacefB— the stigma is longer and more 
papillose ia the short-styled form, though the reverse of this 
holds E'X"i in Gilia, a member of the same family with Phlox. 
The similar position of the anthers in the two forms is some- 



I 



'Pfoo. AtDBriosn Aoad. of Arte and Sciences,' Jane U. 1870, p. 218. 



EEYTHROXYLUM. 



121 



wliat opposed to the present epecios being hoterostylcJ ; as ia 
the great difFerenfo in the length of the pistil in several shurt- 
Btyled flowers. But the extraordinary vaiiability in diameter of 
the pollen-graina, and the fact that in one set of flowere the 
grains from the long-styled flowers were lai^ei than those from 
the short-styled, is strongly opposed to the belief that Phlox 
luiiihta is heterostyled. Possiljly this species was once hetero- 
styled, but is now becoming siib-dicecions ; the short-styled 
plants haTJng been rendered more feminine in nature. This 
would account for their oyaries nsually containing more ovules, 
and for the variable condition of their pollen-grains. Whether 
the long-styled plants are now changing their nature, as would 
appear to be the case from the variability of tlieir pollen-grains, 
and are becoming more masculine, I will not protend to con- 
jecture; tliey might remain as hermaphrodites, for the co- 
existence of lierraaphrodite and female plants of the same 
species is by no means a rare event. 



ErYTHBOSYIUM [bP. ?] (EnYTBBOXYLIDffi). 

Fritz Miiller sent rae from South Brazil dried flowers of this 
tree, tc^ether with the accompanying drawings, wMch sliow thf 
two forms, m^uiGed about five times, with the petals removed 

Fig. 8. 




long-itf ted form. Shait^tjM fona 

From » ikelch by Frili MilUcr, magnified five tian. 

Eetthtioxtlon [«p. ?J 



122 HETEEOSTVLED DIMOEPHIO PLANTS. Chap. ] 

In the long-RtjIed form the stigmas projeot above the anthera, " 
and the stales are ncarlj twice as long as those of the ehort- 
Btjled form, in whicb the stigmas stand heneuth the anthers. 
The stigmas in many, hut not in all the short-styled flowers are 
larger than those in the long-styled. The anthers of the short- 
styled flowers stoind on a leTal with the stigmiw of the other 
form ; but the stamens are longer hy only one-fourth or ono-flftli 
of their own length than those of the long-styled. Consequently 
the anthers of the latter do not stand on a level with, tint rather 
above the stigrans of the other form. Differently from what 
occurs in the following closely allied genus, Sethin, the stamens 
are of nearly eqiial length in the flowers of the same fonn, Xhe 
pollea-grainB of the short-styled flowers, measured in their drj' 
stiite, are a little larger than those &om the long-styled flowers 
in about the ratio of 100 to Wi.' 

SeTOIA AOCMUJATA (ERYTintOSTUDA), J 

Mr. Thwoites pointed out several years agof that this plaaS 
exists under two forms, which he designated as forma tti/losa et^ 
sl'iminai i and the flowers sent to me by him are clearly hetero- 
styled. In the long-styled form the pistil is nearly twice as 
long, and the stamens half as long as the corresponding organs 
in the shon-styled form. The stigmas of the long-stjled seem 
rather smaJer than those of the short-styled. All the stamens 
in the short-styled flowers are of nearly equal length, whereas 
in long-styled they differ in length, being alternately a little 
longer and shorter; and this difibrence in the stamens of the 
two forms is protiabiy related, as we shall hereafter see in 
the case of the short-styled flowers of Lythritm mlicarla, to the 
manner in which tosecta can best transport pollen from the 
long-styled flowers to the stigmas of the short-etjled. The 
pollen-grains from the short-styled flowers, though variable in 
size, are to those of the long-styled, as far as I ooold make out, 
as lUO to y3 in their longer diameter. Stthia obiutifoiia is 
heterostyiod like S. ucuminatn. ■ 

* F. Mailer remarlia ia hia list- numbera; bat the aapkla and p(jMl~ 
tettoiiiulhatlbefliwera.of nhuh olteo Viiry lioiii 5 to T ; tlia sta- 
tu: (MrefuUj eiamiiiod luuny edk- niLngfnmi 10 lo 11, and tlie pi^tilB 
LimenB, ate oiLtiously viiruible fiian 3 t<i 4. 
in tliB nuoibar »f tliur pnrtB t ■ Ennmeratio Plniitariim Ziy 
S BipaU anil jH-tda, 10 BtumciiB ItiiuD,' 1804, p. S4. 
and A piutilu Bca tlie presailiiig 



^GIPHILA ELATA. 



I 



CBATOXlfLON FOHMOBCa (HyPEBlOIHKfi). 

Mr. TliiEelton Dyer remarks that this tree, an inhabilftnt of 
Malacca and Borneo, appears to be hetcroatyled.* He sent me 
dried flowers, and the diffeieiuM between the two forms is con- 
Bpicuous. In the long-atjled form the pistila are in length to 
those of the sliort-atyled as 100 to 40, with their globular 
Btigmas about twice as thick. These eland just above tjie numer- 
ous anthers and a little beneath the tips of the petals. In the 
sbort-stylcd form the anthers project high a'ove the piKtils, the 
Btigmas of which diverge between the three bundles of etamena, 
and stand only a little above the tips of the sepals. The 
stamens in this form are to those of the long-styled as 100 to &fi 
in length ; and therefore they do not diflbr so much in length 
as do the pistils. Ten polion-graina from each form were 
measured, and those from the sliort-stylod wore to those from 
the long-styled as 100 to 86 in diameter, 'ibis plant, therefore 
is in ail respects a woU-charactcrisod hetcrcatjled apeuies. 



^GIPHILA ELATA (VEEBBNACEffi). 

Ur. Benthom was so kind as to send me dried flowers of this 
species and of M, Tnollia, both inhabitants of South America. 
The two forms differ conspicuously, as the deeply bifid stigma 
of the one, and the anthers of the otJier project far above the 
mouth of the corolla. In the long-styled form of the present 
Biiocies, tjie style is twice and a half as long as that of the short- 
styled. The divergent stigmas of the two forma do not differ 
much in length, nor as far as I could perceive in their papilhe. 
Is the long-styled flowers the fUiunents adhere to the corolla 
close up to the anthers, which are enclosed some way down 
within the tnl>e. In the shorb-siyled flowers the filaments are 
free above the point where the anthers are seated in the othej' 
form, and they project from the corolla to an equal height with 
that oF the stigmas in the long-styled flowers. It is often 
difficult to measure with accuracy pollen- grains, which have 
long been dried and then soaked in water; but they here 
manifestly differed greatly in size. Those from the shorl^etyled 
flowers were to those from the long-styled in diameter iL 



' Journal uf Botany,' London, 1872, p. 2i 



12-1 HETEEOSTYLED DIMORPHIG PLANTS. CUAr. I. 

about tlis ratio of 100 to 62. The two foi-ms of ^, i 
preaent a like diSbrcnc« ia tlia length of tlioii piatils and 1 



JEGIFHILA OBDUaATA. 

Flowers of this biish were Bent me from St. Catharina in 
Brozil, bj Fritz Miiller, and were named for mo at Kew. Tliey 
appeared at first sight graniilj hoterostyled, as the stigma oJ 
the loDg-atyled form projects far out of the corolla, whilst the 
anthers are seated halfway down within the tube; whereas in the 
short^atjled form the anthers project from the corolla and the 
Btigma is enclosed in the tube at nearly the same level with the 
anthers of the other form. The pistil of the long-styled is to 
that of the short-styled as 100 to 60 in length, and the Btigmae, 
taken by themselves, as 100 to 55. Nevertheless, this plant 
cannot bo heteiostyled. The anthers in the long-styled form 
are brown, tough, and fleshy, and less than half the length 
of those in the shori^atyled form, strietly as 44 to 100 ; and 
what is much more important, they were in a rudimentai? 
condition in the two flowers esamined by me, and did not 
contaia a eingle grain of pollen. In the short-styled form, the 
divided Btigma, which as we have seen is much shortened, 
is thicker and more fleshy than the stigma of the long- 
styled, and is covered with small irregular projections, formed 
of rather large cells. It had the appearance of having suf- 
ft;red from hypertrophy, and ia probably incapable of fertili- 
sation. If this be so the plant is dicecioiis, and judging from 
the two species previously described, it probably was once 
heterostyled, and has since been rendered dicecious by the 
pistil in the one form, and the stamens in the other having 
beeome functiouJess and rednccd in size. It is, however, 
possible that the flowers may be in the same state as those of 
the common thyme and of several other Labiate, in which 
females and hermaphrodites regularly co-exist. Fritz Miiller, 
who thought that the present plant was heterostyled, as I 
did at first, informs me that he found bushes in several places 
growing quite isolated, and that these were completely Blerile; 
whilst two plants growing close together were covered with 
fruit This fact agrees better with the belief that the species is 
diiBcions than that it consists of hermaphrodites and females; 
for if any one of the isolated plants had been an hermaphrodite, 
it would probably have produced some truii 



I 



4 



MITCHELLA EEPEN8. 



EOBIACEJI. 



TluB great natural family contains a much larger 
number of beteroatyled genera than any other one, as 
yet known. 

Mitchdla repens. — Prof. Asa Gray sent me several 
living plants collected when out of flower, and nearly 
lialf of these proved long-styled, and the other hall 
short-styled. The white flowers, which are fragrant 
and which secrete plenty of nectar, always grow in 
pairs with their ovaries united, so that the two together 
produce "a berry-like double drupe."* In my first 
series of experiments (1864) I did not suppose that 
this curious arrangement of the flowers would have any 
influence on their fertility ; and in several instances 
only one of the two flowers in a pair was fertilised ; 
and a large proportion or all of these failed to produce 
berries. In the ensuing year both flowers of each 
pair were invariably fertilised in the same manner ; 
and the latter experiments alone serve to show the 
proportion of flowers which yield berries, when legiti- 
mately and illegitimately fertilised; but for calcu- 
lating the average number of seeds per berry I have 
used those produced during both seasons. 

In the long-styled flowers the stigma projects just 
above the bearded throat of the corolla, and the 
anthers are seated some way down the tube. In the 
short-styled flowers these organs occupy reversed posi- 
tions. In this latter form the fresh pollen-grains are 
a little larger and more opaque than those of the long- 
styled form. The results of my experiments are given 
in the following table. 



1 N. Uiiitcd Stalea,' IKHS, 



126 UETEBOSTYLED DDIOHPHIC PLANTS. Ch*p. m. ^ 
Table 2L. 
Milchdla repent. 



N«u™ ot DuloiL 


Nmnber of Namlwr of Hwaber at 

pjdtsof lirupHpm- BODdSHdi 

Floneisfcr- daced during per Drupe io 

laimd daring thcjwomd ill lUe Dmpat 

8«*,n. j Itw-S^on^ 


Long-«tjled flowers, by poIIoD oft q o A.r 


Long-stylei flowers, by oun-form \ 1 o 1 a I q <i 
pollen. Ulegitimflle uaiott . J; ^ | 3 [ 32 


Short-Btyled flowers, by pollen ofll o 1 i , , 
loDg-slyled. LsgitimaW union. I[ "1 | ' 


Short-styled Bowers, by own-forml' n 1 n 1 ^ n 
pollen. Ulegitimnte union . .|, ^ | 20 


'leti:;':^'"™"." .""':"":)! " | 'O ■'■■' 


Xl.^two.Ugltl..e_.nlo.sto.j! H | 3 j .. 



It follows from this table that 88 per cent, of tha 
paired flowers of botli forma, when legitimately fer- 
tiliaed, yielded double berries, nineteen of whicli con- 
tained on an average 4'4 seeds, with a maximum in 
one of 8 seeds. Of the illegitimately fertilised paired 
flowers only 18 per cent, yielded berries, six of which 
contained on an average only 2'1 seeds, with a maxi- 
mum in one of 4 seeds. Thus the two legitimate 
unions are more fertile than the two illegitimate, 
according to the proportion of flowers which yielded 
berries, in the ratio of 100 to 20; and according to 
the average number of contained seeds as 100 to 47. 

Three long-styled and three short-styled plants were 
protected under separate nets, and they produced alto- 
gether only 8 berries, containing on an average only 



4 



IP. IIL BORRKRIA. 127 

l"5 seed. Some additional beriiea were produced 
whicli coutaiued no seeds. The plants thus treated were 
therefore excessively steide, and tlieir sligLt degree of 
fertility may bo attributed in part to the action of the 
many individuals of Thrips which haunted the flowers. 
Mr. J. Scott ijiforms me that a single plant (probably 
a long-styled one), growing in the Botanic Gardens at 
Edinburgh, which no doubt was freely visited by in- 
BCcta, produced plenty of berriea, but how many ol 
them contained seeds was not observed. 



BOBKERIA, NOV. 8P. NEAB VALERIAN0IDE8 (RvBIACEJE). 
Fritz Mullur sent me seeds of this plant, which is 
extremely abundant in St. Catharina, in South Brazil ; 
and ten plants were raised, consisting of five long- 
styled and five short-styled. The pistil of the long- 
styled flowers projects just beyond the mouth of the 
corolla, and is thrice as long as that of the short- 
styled, and the divergent stigmas are likewise rather 
larger. The anthers in the long-styled form stand 
low down within the corolla, and are quite hidden. 
In the short-styled flowers the anthers project just 
above the mouth of the corolla, and the stigma stands 
low down within the tube. Considering the great 
difference in the length of the pistils in the two forms, 
it is remarkable that the pollen-grains differ very little 
in size, and Fritz Miiller was struck with the same 
fact. In a dry state the grains from the short-styled 
flowers could just be perceived to be larger than those 
from the long-styled, and when both were swollen by 
immersion in water, the former were to the latter in 
diameter in the ratio of 100 to d'2. In the long-styled 
flowDTB beaded hairs almost fill up the mouth of the 
corolla and project above it ; thoy therefore stand 
above the anthers and beneath the stigma. In the 



128 HETEBOBTYLED DIMOBPHIO PLANTS. Chap. ] 

Bhort-atyled fluwera a similar brush of hairs is situated 
low down within the tubular corolla, above the stigma 
and beneath the anthers. The presence of these beaded 
hairs in both forms, though occupying such different 
positions, shows that they are probably of considerable 
fanctional importance. They would serve to guard the 
stigma of each form from its own pollen ; but in 
accordance with Prof. Kemer's view* their chief use 
probably is to prevent the copious nectar being stolen 
by small crawling insects, which could not render any 
service to the species by carrying pollen from one form 
to ^he other. 

The flowers ore so small and so crowded togetlier 
that I was not willing to expend time in fertilising 
them separately ; but I dragged repeatedly heads ol 
short-styled flowers over three long-styled flower-heada, 
which were thus legitimately fertilised ; and they pro- 
duced many dozen fruits, each containing two good 
seeds. I fertilised in the same manner three heads 
on the same long-styled plant with pollen from another 
long-styled plant, ao that these were fertilised illegiti- 
mately, and they did not yield a single seed. Nor did 
this plant, which was of course protected by a net, 
bear spontaneously any seeds. Nevertheless another 
long-styled plant, which was carefully protected, pro- 
duced spontaneously a very few seeds; so that the 
long-styled form is not always quite sterile with its 
own pollen. 

FaEAMEA [SP. ?] (RUBIACE^}. 
Fritz JluUer has fully described the two forms of this ' 
remarkable plant, an inhabitant of South Brazil.f In | 



n 



• 'Die Sohutzraittel der Blii- 
llicii B^geii uabecufene Gaotc,' 
1876, p. 37. 



t 'BoiZe[tnng,'Bept. 10,1868, 



Chap. Ill, FAKAMEjV. 129 

the long-styled form the pistil projects above the 
corolla, and is almost exactly twice as long as that of 
the short-sty led, which is included within the tube. 
The former is divided into two rather short and broad 
stigmas, whilst the short-styled pistil is divided into 
two long, thin, sometimes much curled stigmas. The 
stamens of each form correspond in height or length 
with the pistils of the other form. The anthers of 
the short-styled form are a little larger than those 
of the long-styled ; and their pollen-grains are to 
those of the other form as 100 to 67 in diameter. 
But the pollen-grains of the two forms differ in a 
much more remarkable manner, of which no other 



Fig. 9. 




itytcil form. Lung-styled fon 



I 'qII en -grains, magnilipd ISU 



limes, by Frill JUuller, 
FiEliXEA. [sp. ?]. 

lustaijce is known; those frum the short-styled flowers 
being covered with sharp points ; the smaller ones 



130 HETEE08TYLED DIMORrmC PI.ANTa CBiP. Ill \ 

from the long-styled being quite smootli. Fritz Mullei 
remarks that this difference between the poUen-grainB 
of the two forma is evidently of service to the plant ; 
for the grains from the projecting stamens of the ahort- 
Btyled form, if smooth, would have been liable to ba 
blown away by the wind, and would thus have been 
lost ; but the little points on their surfaces cause them 
to cohere, and at the same time fiivour their adhesion 
to the hairy bodies of insects, which merely brush 
against the anthers of these stamens whilst visiting 
the flowers. On the other hand, the smooth grains 
of the long-styled flowers are safely included within 
the tube of the corolla, so that they cannot be blown 
away, hut are almost sure to adhere to the proboscis of 
an entering insect, which is necessarily pressed close 
against the enclosed anthers. 

It may be remembered that in the long-styled form 
of liinum perenne each separate stigma rotates on its 
own axis, when the flower is mature, so as to turn its 
papillose surface outwards. There can be no doubt 
that this movement, which is confined to the 
styled form, is effected in order that the proper sur 
face of the stigma should receive pollen brought by 
insects from the other form. Now with Faramea, as 
Fritz MuUei shows, it is the stamens which rotate on 
their axes in one of the two forms, namely, the short- 
styled, in order that their pollen should be brushed off 
by insects and transported to the stigmas of the other 
form. In the long-styled flowers the anthers of the 
short enclosed stamens do not rotate on their axes, 
but dehisce on their inaer sides, as is the common 
rule with the RuhiacefB ; and this is the best position 
for (he adherence of the pollen-grains to the proboscis 
of an tnteriug insect. Fritz Miiller therefore infers 
that as the plant became heterostyled, and as the 



I 

4 
4 



EUBIACE& 



131 



stamens of the sliort-atyled form increased in length, 
they gradually acquired the highly beneficial power 
of rotating on their own axes. But he has further 
shown, by the careful examination of many flowers, 
that this power has not as yet been perfected ; and, 
consequently, that a certain proportion of the pollen 
is rendered useless, namely, that from the anthers 
which do not rotate properly. It thus appears that 
th& development of the plant haa not as yet been com- 
pleted ; the stamens liave indeed acquired their proper 
length, but not their fullandperfect power of rotation." 
The several points of difference in structure between 
the two forms of Faramea are highly remarkable. 
Until within a recent period, if any one had been 
shown two plants which differed in a uniform manner 
in the length of their stamens and pistils, — in the 
form of their stigmas, — in the manner of dehiscence 
and slightly in the size of their anthers,— and to an 
extraordinary degree in the diameter and structure of 
their pollen-graing, ha would hove declared it impos- 
sible that the two could have belonged to one and the 



ScTEttiA (Hpecios unDamed in the liorliariiim at Kcw) 

(EcBIACEiE). 

I owe to the kiadnesa of Fi-itis Miiller (lri»l flowers of this 
plant &am St. Catliarinn, in Brazil In the loag-styled form the 
Btigma stands in the month of the corolla, above the aotlicrs, 



• FriU MOIler gives nniitlipr 
inslmwe of tlie syant af ntisolulo 
peifeotion in tbelloweraof anotlier 
memlier or tbe BuliioceiB, nanielj, 
Potoqueria frtigrant, whiali is 



coidaace iritll (be novtiirnnl hatiili 
of tiieso Insects, mfiat of the flowen 
open odI; duiing Lhu night; bill 
some open in Ihe day, and (he 
pollen nt' niich flnwers is Tobbed, ea 
itiillcr hoa often i 



4 



t for eroag-fertillautidii bj tba hui utile- btes and other inB»-tB, 



ajeney 



titotha. (Soe 'But. wilhout an; Ixmcftt being tliua 



Zi-itung,' leCH, No. 17.) In a 



ant'eir£<l ud (lie plant. 



132 HETEKOBTYLED DniOETHIO PLANTS. CHiP. ] 

which latter aro enclosod wiihin the tulie, but only a short way 1 
down. In the short-styled form the anthers are placed in tha 
month of the corolla above the stigma, which occupie§ the sama 
position as the anthers in the other form, l>eing eeated only a 
short way down the tube. Therefore the pistil of the long-atyled 
form does not exceed in length that of the short-styled i: 
nearly so great a degree as in many other Enbioccce. Nevei>> | 
theleas there is aconeiderable difference iu the sizeof the pollen- I 
grains in the two forme ; for, as Fritz Muller infenus me, thoM I 
of the short-styled aro to those of the long-styled as 100 to li 
75 in diameter. 



HOUSTOSIA 

Prof, Aao Gray has been 



(Ettbiaoe*). 



a kind as to send me an al>stract ol 
3 observations made by Dr. Bothroek on this plant. The 
pistil is esserfed in tlie one form and the stamens in tha 
other, as has long been observed. The stigmas of the lon^ 
styled form are shorter, stouter, and far more hispid than in 
the other form. The etigmatio hairs or papillte on the former 
are -04 mm., and on the lattor only "023 mm. in length. In the 
short-styled form the anthera are larger, and the pollen-grains, 
when distended with water, are to those from the long-styled 
form as 100 to 72 in diameter. 

Selected capsules from some long-styled plants growing in 
the Botanic Gardens at Cambridge, U.S., near where plonta 
of the other form grew, contained on an average 13 seeds; 
but those plants must have been subjected to unfavoTirabla 
conditions, for some long-styled plants iu a state of nature 
yielded an average of 21 ■ 5 seeds per capsule. Some shortrstyled 
plants, which had been planted by themselves in the Botanic 
Gardens, where it was not likely that they would have been 
visited by insects that had previously visited long-styled plants, 
produced capsules, eleven of which were wholly sterile, but one 
contained 4, and another 8 seeds. So that the short-styled 
form seems to be very sterile with its own pollen. Prof. Asa 
Gray informs me that the other North American BpecisH of this 
genus are likewise heterostyled. 



4 



Oldbnlasdl* [sp. 7] (Eubiacbs). 

Mr, J. Soott sent me from India dried flowers of a heter* 

ityled species of this genns, which is closely allied to the last ' 



oeap. m. 



EUBIACIiLffl, 



133 



The pistil in Uie long-styled flowers is longer Ijy about a qnartei 
of its lengtj), and the Btamens Bhortei in a1)0ut the same pro- 
portion, thim the corresponding organa in the short-styled 
flowers. In the latter the antliere are longer, and tlie divergent 
stigmas decidedly longer and apparently thinner than in the 
long-atjled form. Owing to the state of the Kpecimeas, I could 
not decide whether tlie stigmatic papilto were longer in the 
one form than in the other. The pollen-grains, distended with 
water, from the short-styled flowers were to those from the long- 
styled as 100 to 78 in diameter, as dednood from the mean of 
ten meoBurementB of each kind. 



Hedyotis [ap. ?] (EcBiACEs). 

Fritz MQIkr sent me from St. Catharina, in Brazil, dried flowers 
of a small dehcato epedea, which grows on wet sand near the 
edges of fresh-water pools. In the long-stylod form the stigma 
projects ftboTe the corolla, and stands on a level with the pro- 
jecting anthers of the shortr^tylod form; but in the latter the 
stigmas stand rather beneath the level of the anthers in the 
other or long-styled form, these being enclosed within the tul>e 
of the corolla. The pistil of the long-styled form is nearly thrice 
as long as that of the short-styled, or, speaking strictly, as 
100 to 39 ; and the papillie on the stigma of the former are 
broader, in the ratio of 4 to 3, but whether longer than those of 
the Bhort>«tyled, I conid not decida In the short-styled form, 
the anthers are rather larger, and the pollen-grains are to those 
from the long-styled flowers, as 100 to 88 in diameter. Fritz 
Miiller sent me a second, small-sizod species, which ia likewise 
heterostyled. 



COOOOOITBELIIM [SP. ?] (RtiBIACBS), 

Fritz Miiller also sent me dried flowers of tliis plant from 
St. Catharina, in Brazil. The exaerted stigma of the long-styled 
form stands a httle above the level of the e)Eserted anthers of the 
Bhort-styled form ; and the enclosed stigma of the latter also 
stands a little above the level of the enclosed anthers in the long- 
styled form. The pistil of the long-atyled is about twice aa long 
OS that of the short-styled, witli its two stigmas considerably 
longer, more dirorgent, and more curled. Fritz Miiller informs 



134 HETEEOSTYLED DIMOKPHIO PLANTa Cbav. 1 

me that he could detect no differonco in the size of the 
ETttinB in the two fonna. Nevertheless, there can be m 
that this plant is hoterostylod. 



LiPOSTOMA [bP. ?] (TtOBIAOEa). 

Dried flowers of this plant, wliich grows in small wet ditehea 1 
in St. Catharina, in Brazi!, were likewise sent me by Fritz 
Miiller. In the long-styled form the eiserted stigma stands 
rather atove the level of the esserted anthers of the other fon 
whilst in (he short-styled form it stands on a level with tho 
anthers of the other farm. So that the want of strict corta- 
spondenco in height between the stigmas and anthers in the two , 
forma is reversed, compared with what occurs in Hedyotia. Tha ■ 
long-styled pistil is to that of the ahort-styled an 100 to 36 ii 
length; and its divergent stigmas are longer by folly one-third 
of their own length than those of the short-styled form. In the 
latter the anthers are a little larger, and the pollen-graina ore 
as 100 to 80 in diameter, ooiaparod with those from the long- 
styled form. 



Cinchona miohantha (En 



«). 



Dried specimens of both forms of this plant were sent me from 
Kew.* In the long-styled form the apex of the atigma standa 
just beneath the bases of tha hairy lobes of tho corolla; whilst 
the summits of the anthers are seated about halfway down 
the tube. Tlie pistil is in length as 100 to 33 to that of the 
short^styled form. In the latter the anthers occupy the BamB 
position as the stigma of the other form, and they are con- 
siderably longer than those of the long-styled form. As the 
summit of the stigma in the abort-styled form stands beneath 
the bases of the anthers, which are seated halfway down tho 
corolla, the style has been extremely shortened in this form' 
its length to that of the long-styled being, in the apecimena 
examined, only as &'3 to lOOl The stigma, also, in the short- 
Btyled form is very much shortfir than that in the long-styled, 
in the ratio of 67 to 100. The poUon-graina from the short- 



4 
4 



• My Bttciition was railed 1o 
Ulis plnnt by s drawinf; onpied 
fmm Howiirii'a • Quintal ugia,' Tab. 



3, given by Mr. Markhun In 1: 
' Travoln in Pern,' p. 5S0. 



Chap. III. EUBIACE^. 135 

styled flowers, after having been soaked in water, wero rather 
larger— in about the ratio of 100 to 91 — than those from the long- 
atjled flowers, and they were more triangular, with the angles 
more prominent. As all the graina from the ehort-styled flowers 
were thus characterised, aaid as they had been left in water for 
three days, I am conTinced that this diflorence in shape in the 
two sets of grains cannot be accounted for by unequal distension 
with water. 

Besides the seYeral Itubiaceous genera already mentioned, 
Fritz Miiller informs me that two or three species of Psychotria 
and Itudyea erUinlha, natives of St Catharina, in Brazil, are 
heterostyled, as is Manettia bicolor. I may add that I formerly 
fertilised with their own pollen several flowers on a plant of 
this latter species in my hothouse, but they did not set a single 
fruit. From Wight and Amott'a description, there seems to bo 
httle doubt that Knoxia in India is heterostyled ; and Asa Gray 
is convinced that this is the case with Biodia and Spermococe 
in the Uaitod States. Lastly, from Mr. W. W. Bailey's descrip- 
tion,* it appears that the Mexican Bouuar'lia ktantha is hetcro- 
styled. 

Altogether we now know of 17 heterostyled genera 
in the great family of the Rubiaceje ; though mora 
information is necesaary witli respect to some of them, 
more especially those mentioned in the last para- 
graph, before we can feel absolutely safe. In the 
' Genera Plantarum,' by Bentham and Hooker, the 
Rubiaceie are divided into 25 tribes, containing 337 
genera; and it deserves notice that the genera now 
known to be heterostyled are not grouped in one or 
two of these tribes, but are distributed in no less than 
eight of them. From this fact we may infer that 
most of the genera have acquired their heterostyled 
structure independently of one another ; that is, they 
have not inherited this structure from some one or 
evon two or three progenitors in common. It fuithci 

• ' Bull, of the Torrcy Dot. Club,' 1S70, p. lOti. 



136 HETEBOSTYLED DDfOBPHIC PLANTS. Gbap. Ill 

deseryes notice that in the homo6tyIed genera, as I 
am informed by Professor Asa Gray, the stamens are 
either exserted or are included within the tnbe of the 
corolla, in a nearly constant manner; so that this 
character, which is not eyen of specific yalne in the 
heterostyled species, is often of generic yalne in other 
members of the family. 



LTTHRUM SALICAEIA. 



CHAPTER IV. 

Uetebostvled TamoitrHia Plaht& 

Lythmm Btilicaria— DeacriptioD of the tlires forms — Tlieir power nad 
oomplei matiDer of fertilking oua onotliur — Eighteen differeal 
uoiona posaible — M[d-atjled Conn eminently feminine in natuie — 
LyttunuD GmifErl lilcewise trimorpliio — !■. tliymifulia dimorphic — 
L. hyBBopirolln homoBtjled — Nesica veiticilliita liimorpliio — Lager- 
itnemia, nature doubtful — Oislis, trimoipliio spcaioa of — 0. Vuldi- 
Tioua — 0. Regiielli, the illegitinmite auiona quits barrcti— O. spe- 
tiota — O. Benidtivn — Uomoatylcd spcoiea of Oxalis— FuntederiiL, 
the one monocotyledonuus genus known to incluile heteiDBtyled 



In tlie previous chapters various lieterostyled dimor- 
phic plants have been described, and now we come to 
heterostyled trimorphic plants, or those which present 
three forma. These have been observed in three 
families, and consist of species of Lylhrum and of the 
allied genus Nestea, of Oxalis and Pontederia. In 
their manner of fertilisation these plants offer a more 
remarkable case than can be found in any other plant 
or animal. 

L^hrum BoJicaria, — The pistil in each form differs 
from that in either of the other forms, and in each 
there are two sets of stamens different in appearance 
and function. But one act of stamens in each form 
corresponds with a set in one of the other two forms. 
Altogether this one species includes three females or 
female organs and three seta of male organs, all as 
distinct from one another as if they belonged to dif- 
ferent species; and if imaller functional differencoB 



138 HErEBOSTYLED TKIMOBPHIO PLANTa Oha*. 1 

are considered, there are five distinct sets of male&l 
Two of tlie three hermaphrodites must coexist, and 
pollen must be carried by insects reciprocally from 
to the other, in order that either of the two should be 
fully fertile; but uulesa all three forms coexist, two 
sets of stamens will bo wasted, and the organisation of 
the species, as a whole, will be incomplete. On the 
other hand, when all three hermaphrodites coexist, and 
poUeu is carried from one to the other, the scheme 
is perfect ; there is no waste of pollen and no false co- 
adaptation. In short, nature has ordained a most com- 
plex marriage-arrangement, namely a triple union 
between three hermaphrodites, — each hermaphrodite 
being in its female organ quite distinct from the other 
two hermaphrodites and partially distinct in its male 
organs, and each furnished with two sets of males. 

The three forma may be conveniently called, from 
the unequal lengths of their pistils, the long-styled, mid' 
styled, and short-styled. The stamens also are of unequal 
lengths, and these may be called the longest, mtd-lenglh, 
and shortest Two sets of stamens of different length are 
found in each form. The existence of the three forms 
was first observed by Vaucher," and subsequently more 
carefully by Wirtgeu ; but these botanists, not being 
guided by any theory or even suspicion of their func- 
tional differences, did not perceive some of the most 
curious points of difference in their structure. I will 
first briefly describe the three forms by the aid of the 
accompanying diagram, which shows the fiowers, six 
times magnified, in their natural position, with their 
petals and calyx on the near side removed. 



I 

I 



• ' Hial Phva. des Plttntes mid desaon Fuimen," ' VerhMwl \ 
d'Enrope,' tom. ii. IS41, p. 371. des oRturhist, Vereins fUr pn 
Wirtgeu," TJcber Lyihrum ealicaria KUbliiI.' 5. Jfthrgang, 1818, S 



LYTMKUM SALICARIA. 
Fig. 10. 




Ulsgnim of the Dowen of the three rormi of Lylhrum xiliairia, id their luliiral 
(wltioD, with the petuls und cnl^x reinuved on the neai lidei enUrged »L> tiinus. 

The dntleJ liDes with the arrows ihow the directiooi In which [KiUaD miul be 
■rried tu each stigma to eniara full It^nilitf. 



140 HETEEOSTYLED THrMORPHIO PLANTS. Chap. I 

Lotiff-atyJed form.— This form can be at once r 
nised by the Icngtii of the pistil, which is (including 
the ovarium) fully one-tLird longer than that of the 
mid-styled, and more than thrice as long as that of the 
ghort-styled form. It is so disproportionately long^-that 
it projects in the bud through the folded petals. It 
stands out considerably beyond the mid-length sta- 
mens; its terminal portion depends a little, but the 
stigma itself is slightly upturned. The globular stigma 
is considerably larger than that of the other two forma, 
with the papillte on its surface generally longer. The 
six mid-length stamens project about two-thirds the 
length of the pistil, and correspond in length with the 
pistil of the mid-styled form. Such correspondence 
in this and the two following forms is generally very 
close ; the difference, where there is any, being usually 
in a slight excess of length in the stamens. The six 
shortest stamens lie concealed within the calyx ; their ' 
ends ore turned up, and they are graduated in length, I 
BO as to form a double row. The anthers of these sta- ■ 
mens are smaller than those of the mid-length ones. 
The pollen is of the same yellow colour in both seta. 
H. Miiller" measured the pollen-grain in all three , 
forms, and bia measurements are evidently more trust- | 
worthy than those which I formerly made, so I will 
give them. The numbers refer to divisions of the \ 
micrometer equalling gj^ mm. The grains, distended . 
with water, from the mid-length stamens are 7— 7^, 
and those from the shortest stamens 6-64 in diameter, 
or as 100 to 86. The capsules of this form contain 
Du an average 93 seeds : how this average was ob- 
tained will presently be explained. As these 
when cleaned, seemed larger than those from th' 



• ■ Dio Bi^ftufbtuug (ler Llurnen,' 1B73, p. 103 



Chap. IV. 



LYTHKUM BALICAEIA. 



141 



Btyled or ehort-styled forma, 100 of them were placed 
in a good balance) and by the doublG method of weigh- 
ing were fonnd to equal 121 seeds of the mid-styled or 
142 of the short-atyled ; ao that five long-styled seeds 
very nearly equal six mid-styled or seven short-styled 
Beeds. 

Mid-styled form. — The pistil occupies the position 
represented in the diagram, with its extremity consi- 
derably upturned, but to a variable degree; the 
stigma is seated between the anthers of the longest 
aoid the shortest stamens. The six longest stamens 
correspond in length with the pistil of the long-styled 
form ; their filaments are coloured bright pink ; the 
anthers are dork-colotired, but from containing bright- 
green pollen and from their early dehiscence theyappear 
emerald-green. Hence in general appearance these 
stamens are remarkably dissimilar from the mid-length 
stamens of the long-styled form. The six shortest sta- 
mens are enclosed within the calyx, and resemble in 
all respects the shortest stamens of the long-styled 
form ; both these sete correspond in length with the 
short pistil of the short-styled form. The green pol- 
len-grains of the longest etamens are 9-10 in dia- 
meter, whilst the yellow grains from the shortest 
stamens are only 6 ; or as 100 to 03. But the pollen- 
grains from different plants appeared to me, in this 
case and others, to be in some degree variable in size. 
The capsules contain on an average 130 seeds; bat 
perhaps, as we shall see, this is rather too high an 
average. The seeds themselves, as' before remarked, 
are smaller than those of the long-styled form. 

Short-styled forta. — The pistil is here very short, not 
one-third of the length of that of the long-styled form. 
It is enclosed within the calyx, which, differently from 
that in the other two forms, does not enclose any an- 



142 HETEHOSTTLED TKIMOEPHIO PLANTS. Oa*P. ITl 

thers. The end of tlie pistil is generally bent upwards I 
at right Angles. The six longest stamens, with their 
pink filaments and green pollen, resemble the corre- 
sponding stamens of the mid-styled form. But accord- 
ing to H. Muller, their pollen-grains are a little larger, 
viz. 9i-10^, instead of 9-10 in diameter. The six 
mid-length stamens, with their uncoloured filaments 
and yellow pollen, resemble in the size of their pollen- 
groins and in all other respects the corresponding 
stamens of the long-styled form. The difference in 
diameter between the grains from the two sets of 
anthers in the short-styled form is as 100 to 73. 
The capsules contain fewer seeds on an average than 
those of either of the preceding forms, namely 83 '5;* 
and the seeds are considerably smaller. In this latter 
respect, but not in number, there is a gradation 
parallel to that in the length of the pistil, the long- 
atyled having the largest seeds, the mid-atyled the 
next in size, and the short-styled the smallest. 

Wo thus see that this plant exists under three 
female forms, which differ in the length and curva- 
tuie of the style, in the size and state of the stigma, 
and in the number and size of the seed. There are 
altogether thirty-six males or stamens, and these can 
be divided into three sets of a dozen each, differing 
from one another in length, curvature, and colour of 
the filaments — in the size of the anthers, and especially 
in the colour and diameter of the pollen-grains. Each 
form bears Lalf-a-dozen of one kind of stamens and 
half-ardozen of another kind, but not all three kinds. 
The three kinds of stamens correspond in length with 
the three pistils : the correspondence is always between 
half of the stamens in two of the forms with the pistil 
of the third form. The following table of the diameters 
of the poUen-grains, after immersion in water, from 



CffiP. IV. LYTHBUM SALIOAEIA. 143 

both sets of stamens in all three forms is copied from 
H. MuUor; they are arranged iu the order of their 



Pollen-grains from longest stam 


ens of ihoi't-stylca fo 




mid-styled 


„ mid-length stan 


lenfl of long-styled 




short-styled 


„ „ eh->rtMt et™ 


lens of lang-Btyled 


.. 


mid-styleJ 



61 



We here see that .the largest pollen-grains come from 
the longest stamens, and the least from the shortest ; 
the extreme difference in diameter between them 
being as 100 to 60. 

The average number of seeds in the three forms was 
ascertained by counting them in eight fine selected 
capstiles taken from plants growing wild, and the 
result was, as we have seen, for the long-styled (neg- 
lecting decimals) 93, mid-stjled 130, and short-styled 
83. I should not have trusted in these ratios had I 
not possessed a number of plants in my garden which, 
owing to their youth, did not yield the full comple- 
ment of seed, but were of the same age and grew 
under the same conditions, and were freely visited by 
bees. I took six fine capsules from each, and found 
the average to be for the long-styled 80, for the mid- 
styled 97, and for the short^styled fil. Lastly, legiti- 
mate unions effected by me between the three forms 
gave, as may be seen in the following tables, for the 
long-styled an average of 90 seeds, for the mid-styled 
117, and for the short-styled 71. So that we have 
good concurrent evidence of a difference in the average 
production of seed by the three forms. To show that 
the unions effected by me often produced theu' full 
effect and may be trusted, I may state that one mid- 
styled capsule yielded 151 good seeds, which is the 
same number as in the finest wild capsule which 1 



I 



144 HETEROBTVLED TBIMOEPHIC PLANTS. Cb4P. IT 

examined. Sume artificially fertilised short- and long- 
styled capsules produced a greater number of seoda than 
was ever observed by me in wild plants of the same 
forms, but then I did not examine many of the latter. 
This plant, I may add, offers a remarkable instance, how 
profoundly ignorant we are of the life-conditions of a 
species. N'aturally it grows " in wet ditches, watery 
places, and especially on the banks of streams," and 
though it produces so many minute seeds, it never 
spreads on the adjoining land ; yet, when planted in my 
garden, on clayey soil lying over chalk, and which ia ao 
dry that a rush cannot be found, it thrives luxuriantly, 
grows to above 6 feet in height, produces aelf-sowa 
seedlings, and (which ia a severer test) is as fertile as 
in a state of nature. Nevertheless it would be almost 
a miracle to find this plant growing spontaneously on 
such land aa that in my garden. 

According to Vaiicher and Wirtgen, the three forms 
coexist iu all pacts of Enrope. Some friends gathered 
for mo in North Wales a number of twiga from 
separate plants growing near one another, and clas- 
sified them. My son did the same in Hampshire, and 
here ia the result : — 

Table 22. 



I 



j JflOg-stylod. Mlil-Blj-led. 1 Shiirt-slylaL 


Tot«!. 


North Wales ■ ■ ■ 1 »5 1 »? 1 Ti 


264 
129 


XoUl ... 148 1 135 no 


393 



If twice or thrice the number had been collected, 
the three forms would probably have been found 
nearly equal ; I infer this from considering the above , 
figui'es, and from my aon telling me that if he had 



Ohap. IV. 



LTTHRUM BALIOAKIi. 



145 



collijctecl in another spot, he felt sure that the mid- 
Btyled plants would have been in excess. I several 
timca sowed small parcels of seed, and raised all three 
forms ; but I neglected to record the parent-form, 
excepting in one instance, in which I raised from 
short-styled seed twelve plants, of which only one 
tunied out long-styled, four mid-styled, and seven 
short-styled. 

Two pknts of each form were protected from the 
aocesa of insects during two successive years, and in the 
autumn they yielded very few capsules and presented 
1 remarkable contrast with the adjoining uncovered 
plants, which were densely covered with capsules. In 
18C3 a protected long-styled plant produced only five 
poor capsules ; two mid-styled plants produced together 
the same number ; and two shorts-styled plants only a 
single one. These capsules contained very fow seeds ; 
yet the plants were fully productive when artificially 
fertilised under the net. In a state of nature the 
flowers are incessantly visited for their nectar by hive- 
and other bees, various Diptera and Lepidoptera.* The 
nectar is secreted all round the base of the ovarium ; 
but a passage is formed along the upper and inner 
side of the flower by the lateral deflection (not repre- 
sented in the diagram) of the basal portions of the 
filaments ; so that insects invariably alight on the pro- 
jecting stamens and pistil, and insert their proboscides 
along the upper and inner margin of the corolla. We 
can now see why the ends of the stamens with their 
anthers, and the ends of the pistils with their stigmas. 



* H. SlUUer givea a liat of tJie 
•ppoita, ■ Die liefniclitung det 
tiluDMiD,' p. ms. It ajiptu-s that 



146 HETEKOSTYLED TRIMOBPHIO PL.VKTS. Omr. IVl 

are a little upturned, so that they may he brushed by I 
the lower hairy surfaces of the insects' bodies. The 1 
shortest stamens which lie enclosed within the calyx of J 
the long- and mid-styled forms can be touched only by 1 
the proboscis and narrow chin of a bee ; hence they I 
have their ends more upturned, and they are graduated I 
in length, so as to fall into a narrow file, sure to be 
raked by the thin intruding proboscis. The anthers of 
the longer stamens stand laterally farther apart and are 
more nearly on the same level, for they have to brush 
against the whole breadth of the insect's body. In 
very many other fiuwera the pistil, or the stamens, or 
both, are rectangularly bent to one side of the flower, 
This bending may be permanent, as with Lythrwm 
and many others, or may be effected, as in Dictam- 
nus fraxtneSa and others, by a temporary movement, 
which occurs in the case of the stamens when the 
anthers dehisce, and in the case of the pistil when 
the stigma is mature ; but these two movements do 
not always take place simultaneously in the same 
flower. Now I have found no exception to the rule, 
that when the stamens and pistil are bent, they bend 
to that side of the flower which secretes nectar, even 
though there be a rudimentary nectary of large size 
on the opposite side, as in some species of CarydaHs. 
When nectar is secreted on all sides, they bend to 
that side where the structure of the flower allows the 
easiest access to it, as in Lyikrum, vai'iuus Papilio- 
naccK, and others. The rule consequently is, that 
when the pistils and stamens are curved or bent, the | 
stigma and anthers are thus brought into the path- 1 
way leading to the nectary. There are a few cases 
which seem to be exceptions to this mle, but they are 
not so in truth ; for instance, in the Gloriosa lily, the 
stigma of the grotesque and rectangularly bent pistU 



CUAP. IV. 



LTTHKUM 8ALICABIA. 



147 



is brought, not into any pathway from the outside 
towards the nectar-aecreting recesses of the Sower, bat 
into the circular route which insects follow in proceed- 
ing from one nectary to the other. In Scrophularia 
aquatiea the pistil is hent downwards from the mouth 
of the corolla, but it thus strikes the polleu-duated 
breast of the wasps which habitually visit these ill- 
Bceuted flowers. In all those cases we see the supreme 
dominating power of insects on the structure of flowers, 
especially of those which have irregular corollas. 
Flowers which are fertilised by the wind must of 
course be excepted ; but I do not know of a single 
instance of an irregular flower which is thus fertilised. 
Another point deserves notice. In each of the three 
forms two seta of stamens correspond in length with 
the pistils in the other two forms. When bees suck the 
flowers, the anthers of the longest stamens, bearing tbs 
green pollen, are rubbed against the abdomen and the 
inner sides of the hind legs, as is likewise the atigma of 
the long-styled form. The anthers of the mid-length 
stamens and the stigma of the mid-styled form are 
rubbed against the under side of the thorax and be- 
tween the front pair of legs. And, lastly, the anthers 
of the shortest stamens and the stigma of the short- 
styled form are rubbed against the proboscis and chin ; 
for the bees in sucking the flowers insert only the front 
part of their heads into the flower. On catching bees, I 
observed much green pollen on the inner sides of the 
hind legs and on the abdomen, and much yello« 
pollen on the under side of the thorax. There was 
also pollen on the cliin, and, it may be presumed, on 
the proboscis, but this was difficult to observe. 1 had, 
however, independent proof that pollen is carried on 
the proboscis ; for a small branch of a protected short- 
Btyled plant (which produced spontaneously only two 



148 HETEEOSTYLED TKDIOEPHIC FL4NTS. Chap. IV. 1 

capsules) was accidentally left during seyeral days I 
pressing against tlie net, and bees were seen inserting , 
their prabost'ides tlirough. tlie meshes, and in conse- 
quence numerous capsules were formed on this one 
small branch. From these several facta it follows that 
insects will generally carry the pollen of each form iiom 
the stamens to the pistil of corresponding length ; and 
we shall presently see the importance of this adapta- 
tion. It must not, however, be supposed that the be(!8 
do not get more or less dusted all oyer with the several 
kinds of pollen ; for this could be seen to occur with 
the green pollen from the longest stamens. Moreover 
a caae will presently be given of a long-styled plant 
producing an abundance of capsules, though grow- 
ing quite by itself, and the flowers must have been 
fertilised by their own two kinds of pollen ; but 
these capsules contained a very poor average of seed. 
Hence insects, and chiefly bees, act both as general 
carriers of pollen, and as special carriers of the right 
sort. 

Wii'tgen remarks* on the variability of this plant in 
the branching of the stem, in the length of the bractese, 
size of the petals, and in several other characters. The 
plants which grew in my garden had their leaves, ' 
which differed much in shape, arranged oppositely, 
alternately, or in whorls of three. In this latter case 
the stems were hexagonal ; those of the other plants 
being quadrangular. But we aio concerned chiefly, 
with the reproductive organs: the upward bending of 
the pistil is variable, and especially in the short-styled 
form, in which it is sometimes straight, sometimes 
slightly curved, but generally bent at right angles. 
The stigma of the long-styled pistil frequently haa 



LYTHRUM BALtCARLL 



149 



longer papillie or is rougher tlian that of the niid- 
atyled, and the latter than that of the short-styled ; 
but this character, though fixed and uniform in the 
two fonns of Frimttla verts, &c., is here variable, for 
I have seen mid-styled stigmaa rougher than tlioss 
of the long-styled.* The degree to which the longest 
and mid-length stamens are graduated in length and 
hare their ends upturned is variable ; sometimes all 
are equally long. The colour of the green pollen in 
the longest stamens is variable, being sometimes pale 
greenish -yellow ; in one shoit-styled plant it was almost 
white. The grains vary a little in size : I examined 
one short-styled plant with the grains above the 
average size ; and I have seen a long-styled plant with 
the grains from the mid-length and shortest anthers of 
the same size. We here see great variability in many 
importjmt characters; and if any of these variations 
were of service to the plant, or were correlated with 
useful functional differences, the species is in that 
state in which natural selection might readily do much 
for its modification. 



On the Power of Mutual Fertilisation between the three 
Forms. 

Nothing shows more clearly the extraordinary com- 
plexity of the reproductive system of this plant, than 
the necessity of making eighteen distinct unions in 
order to ascertain the relative fertilising power of the 



* T lie plants vhich I observod 
grew m my garden, anil prolably 
Turitd ralber mure tlian IhuBS 
growing in a. Blsto of nature. II. 
MUller lina deaoriboii tbe Etigmos 
of all thiMt foiLiis with great aire, 



nod ho eppeare to have found (be 
Btigiimtlo pajiillie differing con. 
stanilj io leugtli nod atmctiire in 
the three furiiiB, btiug longest in 
the loDg-stjIed (orm. 



150 HETEEOSTYLED TKIMOBPniO PLANTS. CsAf. IV ] 

three forma. Thus the long-styled form ha 
tilised with pollen from its o\vn two kinds of anthers, 
from the two in the mid-styled, and from the two in 
the ahort-styled form. The same process hiis to be 
repeated with the mid-styled and short-styled forma. 
It might have been thought sufficient to have tried on 
each stigma the green pollen, for instance, from either 
the mid- or short-styled longest stamens, and not 
from both ; but the result proves that this would 
have been insufficient, and that it was necessary to 
try all six kinds of pollen on each stigma. As in 
fertilising flowers there will always he some failures, 
it would have been advisable to have repeated each o( 
the eighteen unions a score of times; but the labour 
would have been too great; as it was, I made 22!) 
unions, i.e. on an average I fertilised above a dozen 
flowers in the eighteen different methods. Each flower 
was castrated ; the adjoining buds had to be removed, 
so that the flowers might be safely marked with 
thread, wool, &c.; and after each fertilisation the stigma 
was examined with a lena to see that there was suffi- 
cient pollen on it. Plants of all three forma were 
protected during two years by large nets on a frame- 
work ; two plants were used during one or both years, 
in order to avoid any individual peculiarity in a par- 
ticular plant. As soon as the flowers had withered, 
the nets were removed ; and in the autumn the cap- 
sules were daily inspected and gathered, the ripe 
' i being counted under the microscope, I have 
given these details that confidence may be placed 
in the following tables, and as some excuse for two 
blunders which, I believe, were made. These blunders 
are referred to, with their probable cause, in two 
foot-notes to the tables. The erroneous numbers, how- 
ever, are entered in the tables, that it may not be sup- 



QW- I 

up- ^m 



LYTUHUM SALIOASIA. 



151 



poaeil that I have in any one instance tampered with 
the results. 

A few words explanatory of the three tables must be 
giren. Each is devotad to one of the three forms, and 
is divided into six compartments. The two upper ones 
in each table show the number of good seeds resulting 
from the application to the stigma of pollen from the 
two sets of stamens which correspond in length with 
the pistil of that form, and which are borne by the 
other two forms. Such unions are of a legitimate 
nature. The two next lower compartments show the 
result of the application of pollen from the two sets of 
stamens, not corresponding in length with the pistil, 
and which are borne by the other two forms. These 
unions are illegitimate. The two lowest compartments 
show the result of the application of each form's own 
two kinds of pollen from the two seta of stamens be- 
longing to the same form, and which do not equal the 
pistil in length. These unions are likewise illegiti- 
mate. The term own-form pollen here used does not 
mean pollen from the flower to be fertilised — for this 
was never used — but from another flower on the same 
plantj or more commonly from a distinct plant of the 
same form. The figure (0) means that no capsule was 
produced, or if a capsule was produced that it contained 
no good seed. In some part of each row of figures in 
each compartment, a short horizontal line may be seen ; 
the unions above this line were mads in 1862, and 
below it in 1SG3. It b of importance to observe this, 
as it shows that the same general result was obtained 
during two successive years ; but more especially be- 
cause 1863 was a very hot and dry season, and the 
plants had occasionally to be watered. This did not pre- 
vent the full complement of seed being produced 6om 
the more fertile unions ; but it rendered the less fertile 



152 HETEROSTYLED TEIMOEPHIC PLANTS. Chap. ItI 

ones even mote sterile than tkey otherwise would hare 
been. I have seen striking instances of thia fact in 
making illegitimate and legitimate unions with Pri- 
mula ; and it is well known that the conditions of life 
must be highly favourable to give any chance of suo- i 
cess in producing hybrids between species which are 
crossed with difSculty. 



Table 23. — Long-itylcd Fonn. 



L 




JL 


Ltg<UtaaU 


UB/W. 


LegitlmaU union. 


13 flowen fartilised by the longetl 


13 flowers fertilised hy the longeit 


•lamens of the mid 


-ityled. These 


stumens of the ehurt-ttyled. TheM 


>t»ineiii equal in le 


ugth the piBtil 


Btnmens equal in Uogth tha pistil 


ofthelong-iljled. 




of the loag-etyled. 


Product of good seed in each rap- 


Product of good seed la each cap- 


aule. 






38 


53 


l.'>9 IM 


81 





43 119 








m poor seed. 96 








103 99 








131 









45 






il 




114 


•AS per «Dt. of 


these flonera 


84 per cent, of these fiovren 


yielded capsules. Ea 


ch capsule coa- 


yieldeil capsules. Each capsule con- 


tained, on an atel'age, 51-2 aeeda. 


tained, on an average, 107-3 seed*. 


111. 




IV. 


IlUgitimali 


uni'on. 


JlUgUimtOe union. 


U floweri fertilia 


ed by the short- 


12 flowen, fertilised hy the mi* 


e>t Btameos o! the n 


id-styled. 


length stamens of thp short-alylei 







20 





























— 


"o 









Too sterile for a 


ny average. 


Too sterile for any ayerage. 



LYTHItUM SALICAEIA, 



Table 23.— Lonj-B^fei fora—coniinuerf. 


V. 

niegitirmiU anion. 
15 flowen fertilised by own-form 
mid-leDgth Btameos. 


VL 
lU^gitimale unioa. 
15 flowers fertilised byown-fonn 
ihortest stamens. 


a — 

10 

as 








4 — 

3 

4 







Too Bterile for aa; oversee. 


Too stcrila for any nTeraga. 



Besides the alwve experiments, I fertilised a consi- 
derable nomber of long-styled flowers with pollen, 
taken Ly a camel's-hair brush, from both the mid- 
jength and shortest stamens of their own form : only 
5 capsules were produced, and these yielded on an 
average 14' 5 seeds. In 1863 I tried a much better ex- 
periment; a long-styled plant was grown by itself, 
niiles away from any other plant, so that the flowers 
could have received only their own two kinds of pol- 
len. The flowers were incessantly visited by bees, and 
their stigmas must have received successive applica- 
tions of pollen on the most favourable days and at the 
most favourable hours: all who have crossed plants 
know that this highly favours fertilisation. This plant 
produced an abundant crop of capsules; I took by 
chance 20 capsules, and these contained seeds in 
number as follows : — 



154 HBTEEOSTYLED TBIMOEPHrC PLANTS. Chap. 3 



This e 



1 average of 21 -5 secda per capsule. A«" 



we know that the long-styled form, when standing 
near plants of the other two forma and fertilised by 
insects, produces on an average 93 seeds per capsule, 
we see that tliis form, fertilised by its own two pollens, 
yields only between oiie-fourth and one-fifth of the full 
number of seed. I have spoken as if the plant had re- 
ceived both its own kinds of pollen, and this is, of 
course, possible ; but, from the enclosed position of the 
shortest stamens, it is much more probable that the 
stigma received exclusively pollen from the mid- 
length stamens ; and this, as may be seen in com- 
partment V. in Table 23, is the more fertile of the two 
self-unions. 





I^BLV n.-Mid-st!/Jed Fm-m. 


I. 


1 

Legilmatt union. ■ 


13 flowen 
length stam 
These BtHme 
piatil of the 


fertilised bj the mid- 
ns of the long-atjied, 

na eqaril ia leagth tha 

mid-atyled. 


12 flowera fcrtlliMd by tha mid- 
Icnitth stamen, of the sliort-stylod, 
TheM Btamezis eqnnl ia leagth the 
pistil of tha mid-stj-led. 


Product of 


good seed in each cap- 
sule. 

132 


Product of gnod seed in each cap. 


133 


112 109 


140 


60 


130 U3 


147 


151 


■=, 1 


lOS 


IIB 


100 145 1 


133 


138 


33 12 


144 





— 141 
104 


92 per cent, of tha flowera (pro- 
hablj 100 per cent.) jlelded cap- 
■ulea. Each citpsule contaised, oa 


100 per cent, of the flowers yielded 
capsules. Each capanle contained, 
on anSTerage, 108-0 seeds; or, ei- 
cluding capsules with less th.m 20 
weds, the average ia U6-7 soedi. 



A 



m^m 



rCuAP IV. LYTHEUM SALIC.VEIA. 155 

Table 24. — Mid-styled Form — amfinued. 



HI. 


IV. 


niegilimate union. 
13 flowers fertiliaed by Ihe shon- 
ut sUimeDS of tbe toDg-stjIed. 


Illegitimate union. 
15 flowers fertilised by the long 
est stamens of the short-styled. 


83 12 

— 
4* 

45 


115 113 
14- 29 
6 17 
2 113 

9 79 
— 128 
132 


M per cent, of the flowers yielded 
mpsnlan. E»ch oapaule contained, 
on BD nFerags, 47-4 seeds; or, a- 
Binding cnpgules with less thiin ^0 
leedi, tbe average is 60 ■ 3 seeds. 


93 per cent, of the flowers yielded 
capsules. Each capsule contnined, 
on an aveinge, 69-5 seedsi or, ei- 
cludinK ca|.iuies with less than 20 
seeds, tiie average is 102-8. 


V. 


VL 


12 flowers fertilised by awD-furm 
tongest itmnens. 


llleaitimale union. 
12 flowers fertilised by own-form 


03 
9 Q 
63 










130?» 


Eielnding the capsule with 136 
ued.1, 26 per cent, of the flowers 
yielded cHpsoles, and each cnpsula 
eontfllned,Dn an average, 51-a seeds; 


Mot ooe flower yieldod a capsule. 


er,ei:cludingcapsQliis with tesji than 
SO seeds, the average u T7'5. 





* I hare Imrilly n doubt tliat 
tliii result nf ISCuBedainootitpart- 
ment V. was ilue to a gross error. 
Tbe flowers to be fertiliaod by 
thtiii own longest sttunaua were 
flnt mnrked bj *■ white thrend," 
and thcst! Iiy tlie mid-lenicth 
■lamena of tbe long-styled form 
bj " while ailk .-■■ a fiowLT fertilised 
in tbe lator ninnnL'T nonlil have 
yielded about 136 seiils, and it may 
be abserved tlial one such pod lb 



missing. v!x. at the bottom of 
oonipartment L Therefora I have 
hurdly imy doubt tiint I fertiliMid 
a fliiwer niurkeii with " while 
tiireail ' a» if it had lieen marked 

rith " white silk." Wil" 

■) the capsole whloli y 
set'ds, in the same colun 
that which jioldod 136, I do 
at it know what to think. I 
enduHVonred to prevent pollen 
djoppiug from an upper to a lowui 



Besidea the experiments in tlie abore table, I ferti- 
lised a considerable number of mid-styled flowcra with 
pollen, taken by a carael's-hair brush, from both the 
longest and shortest stamens of their own form ; only 
5 capsules were producedj and these yielded on an 
average ll^O seeds. 

Table i5.—ShoTt-$tyli-d Form. m 



n. 

Legiiimate uniW 
13 flowers fmilbed bj the short- 
est stamons of tha mid^tjled. 
These stamens equal ia length tha 
pistil of the shorl-ttjled. 




HETEBOSTTLED TEIMOnPinC FLAJJTB. Chap. 



1 



Legitinale Miion. 

nrs feTtilised br the shtrrt- 

nena of the long-styled. 

stamens equal in length the 

irtheshort-atvled. 



83 percent, of tha flowers fielded 
capsules. Each capsaln co ' ' ' 
ea an arerage, 81*3 seedi. 



o 1 pet cpnt. of the flowen jEcIdad 
capsules. Each capsula caataiiiad. 
"" in average, 64 '6 seedi. 



lUegHimate union, 
lowers fertilised by the Long^ 
.mens of tha mid-styled. 



i 



flower, and I tried to remomber to 
wipu the pinoera curerully after 
each feitilisotioo : but in mftkiiig 
eighteen diffurt^nt unions, soiae- 
times on windy days, and pestei«d 
by beea und flits buKzinj; ubont, 
■ome fen errors could banlly be 
avoided. One day 1 bad to keep 
a tbiid man by me all (be time ta 
piGTOQt tbo axa Tiaitlng tbe an- 



ODToreil plnnU, for in a few 
Beooiida' time tlioy might hava 
done irttpariible njiDcliiet IE wai 
also extremely difBcuit toezcloda 
minnto Uiptera from the net. Ia 
1S62 [ made the great mistake of 
placing a. mid-etyle'l end long- 
etyled under the aime huge net ' 
111 ISG^ I Bvoided Uiia error. 



I 



Chap. IV. LTTUEUM BALICABIA. 157 

Table 95. — Short-sti/led Form— continued. 



lOegitimaU union. 
10 Eowera fflrtiliaed bj ovni'torm 
longest itameiu. 



Besides the experiments in the tahle, I fertilised a 
number of flowers without particular care with their 
own two kinds of pollen, but they did not produce a 
single capsule. 

Summary ofilte Eesvlts. 

Lonff-styled/orm.—Tweatj-six flowers fertilised le- 
gitimately by the stamens of corresponding length, 
borne by the mid- and short-styled forma, yielded 61'5 
per cent, of capsules, which contained on an average 
89-7 seeds. 

Twenty-six long-styled flowers fertilised illegiti- 
mately by the other stamens of the mid- and short- 
atyled forms yielded only two very poor capsules. 

Thirty long-styled flowers fertilised illegitimately by 
their own-form two sets of etomens yielded only eight 
very poor capsules ; but long-styled flowers fertilised 



* I Bnspect til 

ferUliWKl ttliB floviur lu ouuiparir 

ment VI. with pollon from the 
BbortAit HlftmeQB uf Che lung-utj'lLiI 
(iirm, and it wuulci tlion Uave 
jielded sliout Ul Btt'ila. FJowt:r3 



by niistata I to be thna fertUiBcd vert mBrlied 
Kitb black silk ; those vith pollen 
fnim tLo mid-lciigth etB.mi:uii at 
the ehort-Btyled with blaok thread ; 
and tliVri piobnblj the iniitnkc 



158 HETEBOSTYIXD TRQIOEPHIC PLANTS. Chap. XV 

by beea with pollen from their own gtameos produced 
mimeroos capsules contaming on an aveiage 21*5 

seeds. 

Mid-sli/led form. — Twenty-four flowers legitimately 
fertilised by the stamens of corresponding length, 
borne by the long and short-styled forms, yielded 96 
(probably 100) per cent, of capsules, which contained 
(excluding one capsule with 12 seeds) on an average 
117-2 seeds. 

Fifteen mid-styled flowers fertilised illegitimately 
by the longest stamens of the short-styled form yielded 
93 per cent, of capsules, which (excluding four cap- 
sules with less than 20 seeds) contained on an average 
102-8 seeds. 

Thirteen mid-styled flowers fertilised illegitimately 
by the mid-length stamens of the long-styled form 
yielded 54 per cent, of capsules, which (excluding 
one with 19 seeds) contained on an arerage 60-2 seeds. 

Twelve mid-styled flowers fertilised illegitimately 
by their own-form longest stamens yieldect 25 per 
cent, of capsules, which (excluding one with 9 seeds) 
contained on an average 77-5 seeds. 

Twelve mid-styled flowers fertilised illegitimately 
by their own-fonn shortest stamens yielded not a 
single capsule. 

Short-ityled form. — Twenty-five flowers fertilised 
legitimately by the stamens of corresponding length, 
borne by the long and mid-styled forms, yielded 72 
per cent, of capsules, which (excluding one capsule 
with on]y 9 seeds) contained on an average 70'8 
seeds. 

Twenty short-styled flowers fertilised illegitimately 
by the other stamens of the long and mid-styled forms 
yielded only two very poor capsules. 

Twenty short-styled flowers fertilised illegitimately 



J 



CUAP. IV. 



LTTHKDM BALICABIA. 



159 



by their own stamens yielded only two poor (or per- 
haps three) capsules. 

If we take all sis legitimate unions together, and 
all twelve illegitimate unions together, we get the fol- 
lowing results : — 

Tablb 26. 



N.liirc of Unl„n. 


Nnmber 


or Capnumi 




tilUcd. 


Tht rii legitimatel 

DDiODI .... 1 


75 


.e 


96 -28 


71-89 


Th. twelre illegiti-\l . 
nifllanoium . ,/ 


as 


44'7a 


11-03 



Therefore the fertility of the legitimate unions to that 
of the illegitimate, as judged by the proportion of the 
fertilised flowers which yielded capsules, is as 100 to 
33 ; and judged by the average number of seeds per 
capsule, as 100 to 46, 

From this summary and the several foregoing tables 
we see that it is only pollen from the longest stamens 
which can fully fertilise the longest pistil ; only that 
from the mid-length stamens, the mid-length pistil; 
and only that from the shortest stamens, the shortest 
pistil. And now we can comprehend the meaning of 
the almost exact correspondence in length between 
the pistil in each form and a set of six stamens 
in two of the other forms ; for the stigma of each 
form is thus rubbed against that part of the insect's 
body which becomes charged with the proper pollen. 
It is also evident that the stigma of each form, 
fertilised in three different ways with pollen from 
the longest, mid-length, and shortest stamens, is acted 
on very differently, and conversely that the pollen from 



160 HETEKOSTYLED TEIMOBPHIO PLANTS. Chap. IV. 

the twelve longest, twelve mid-length, and twelve 
shortest stamens acts very differently on each of the 
three stigmas ; so that there are three sots of female 
and of male organs. Moreover, in most cases the six 
stamens of each set differ somewhat in their fertilising 
power from the six corresponding ones in one of the 
other forms. We may further draw the remarkable 
conclusion that the greater the inequality in length 
between the pistil and the set of stamens, the pollen 
of which is employed for its fertilisation, by so much 
is the sterihty of the union increased. There are no 
exceptions to this rule. To understand what follows 
the reader should look to Tables 23, 24, and 25, and 
to the diagram Fig. 10, p. 139. In the long-styled form 
the shortest stamens obviously differ in length from 
the pistil to a greater degree than do the mid-length 
stamens ; and the capsules produced by the use of 
pollen from the shortest stamens contain fewer seeds 
than those produced by the pollen from the mid- 
length stamens. The same result follows with the 
long-styled form, from the use of the pollen of the 
shortest stamens of the mid-styled form and of the 
mid-length stamens of the short-styled form. The 
same mle also holds good with the mid-styled and 
short-styled forma, wben illegitimately fertilised with 
pollen from the stamens more or less unequal in 
length to their pistils. Certainly the difference in 
sterility in these several eases is slight ; but, as far as 
we are enabled to judge, it always increases with the 
increasing inequality of length between the pistil and 
the stamens which are used in each case. 

The correspondence in length between the pistil in 
each form and a set of stamens in the other two forma, 
is probably the direct result of adaptation, as it is of 
high service to the species by leading to full and 



LYTHEUM SALICAEIA. 



16] 



I 
I 



legitimate fertilisation. But the rule of tlie increased 
sterility of the illegitimate unions according to the 
greater inequality in length between the pistils and 
stamens employed for the union can be of no serrice. 
With some heterostyled dimorphic plants the dif- 
ference of fertility between the two illegitimate unions 
appears at first sight to be related to the facility of 
self-fertilisation ; so that when from the position of 
the parts the liability in one form to self-fertilisation 
19 greater than in the other, a union of this kind 
has been checked by having been rendered the 
more sterile of the two. But this explanation does 
not apply to Lythrum ; thus the stigma of the long- 
styled form is more liable to be illegitimately fer- 
tilised with pollen from its own mid-length stamens, 
or with pollen from the mid-length stamens of the 
short-styled form, than by its own shortest stamens 
or those of the mid-styled form ; yet the two former 
imions, which it might have been expected would 
have been guarded against by increased sterility, 
are much leas sterile than the otlier two unions 
which are much less likely to be effected. The 
same relation holds good even in a more striking 
manner with the mid-styled foira, and with the short- 
styled form as far as the extreme sterility of all its 
illegitimate unions allows of any comparison. We 
are led, therefore, to conclude that the rule of in- 
creased sterility in accordance with increased in- 
equality in length between the pistils and stamens, 
is a purposeless result, incidental on those changes 
through which the species has passed in acquiring 
certain characters fitted to ensure the legitimate 
fertilisation of the three forms. 

Another conclusion which may be drawn from 
Tables 23, 24, and 25, even from a glance at tbem. 



162 BETEBOSTTLEl) TRIMOBPHIC PLASTS. Our. IT. 

IB that the mid-styled form difTera &om both tlie 
others in iU much higher capacity ibr fertilisation 
in vorioos ways. Not only did the twenty-four flowers 
legitimately fertilised by the stamens of corresponding 
lengths, all, or all but one, yield capsoles rich in 
' teed ; bnt of the other four illegitimate onions, that 
by the longest stamens of the short-styled form was 
highly fertile, thongh less so than the two legitimate 
unions, and that by the mid-length stamens of the 
long-styled form was fertile to a considerable degree ; 
the remaining two illegitimate onions, namely, with 
this form's own pollen, were sterile, but in different 
degrees. So that the mid-styled form, when fertilised 
in the six different possible methods, evinces five 
grades of fertility. By comparing compartments III. 
and VI. in Table 24 we may see that the action of 
the pollen from the shortest stamens of the long-styled 
and mid-styled forms is widely different; in the one 
case above half the fertilised flowers yielded capsules 
containing a fair number of seeds ; in the other case 
not one capsule was produced. So, again, the green, 
large-grained pollen from the longest stamens of 
the short-styled and mid-styled forma (in compart- 
ments IV. and V.) is widely different. In both these 
cases the difference in action is so plain that it cannot 
be mistaken, hut it con be corroborated. If we look 
to Table 23 to the legitimate action of the shortest 
stamens of the long- and mid-styled forms on the 
short-styled form, we again see a similar but slighter 
difference, the pollen of the shortest stamens of the 
mid-styled form yielding a smaller average of seed 
during the two years of 1862 and 18G3 than that from 
the shortest stamens of the long-styled form. Again, 
if we look to Table 28, to the legitimate action on 
the long-flfyleJ form of the green pollen of the tw» 



le tw»^H 



LYTHEUM SALICABLA, 



163 



Beta of longest atamena, we shall find exactly the same 
result, viz. that the pollen from the longest stamens of 
the mid-styled form yielded during both years fewer 
seeds than that from the longest stamens of the 
short-styled form. Hence it is certain that the two 
kinds of pollen produced by the mid-styled form are 
less potent than the two similar kinds of pollen pro- 
dnced by the corresponding stamens of the other two 
forms. 

In close connection with the lesser potency of the 
two kinds of pollen of the mid-styled form is the fact 
that, according to H, MiiUer, the grains of both are 
a little less in diameter than the corresponding grains 
produced by the other two forms. Thus the grains 
from the longest stamens of the mid-styled form are 
9 to 10, whilst those from the corresponding stamens 
of the short-styled form are 9^ to lOJ in diameter. 
So, again, the grains from the shortest stamens of the 
mid-styled are 6, whilst those from the corresponding 
stamens of the long-styled are 6 to 6J in diameter. 
It would thus appear as if the male organs of the 
mid-styled form, though not as yet rudimentary, were 
tending in this direction. On the other hand, the 
female organs of this form are in an eminently efficient 
state, for the naturally fertilised capsules yielded a 
considerably larger average number of seeds than 
those of the other two forms— almost every flower 
which was artificially fertilised in a legitimate manner 
produced a capsule — and most of the illegitimate 
unions were highly productive. The mid-styled form 
thus appears to be highly feminine in nature ; and al- 
though, as just remarked, it is impossible to consider 
its two well-developed sets of stamens which produce 
an abundance of pollen as being in a rudimentary 
condition, yet we can hardly avoid connecting as 



164 HETEEOSTYLED TBIMOEPHIO PIANTS. Chap. 1 

balanced the higher e£Qciency of the female orgj 
in this form with the lesser efficiency and leaser t 
of its two kinds of pollen-grains. The whole easel 
appears to mo a very curious one. 

It may be observed ia Tables 28 to 25 that some 
of the illegitimate unions yielded during neither year 
a single seed ; but, judging from the long-styled plants, 
it is probable, if such unions were to be effected re- 
peatedly by the aid of insects under the most fayour- 
able conditions, some few seeds would be produced ia 
every case. Anyhow, it ia certain that in all twelve 
illegitimate unions the pollen-tubes penetrated the 
stigma in the course of eighteen hours. At first I 
thought that two kinds of pollen placed together on 
the same stigma would perhaps yield more seed than 
one kind by itself ; but we have seen that this ia not 
90 with each form's own two kinds of pollen ; nor is it 
probable in any ease, as I occasionally got, by the use 
of a single kind of pollen, fully as many seeds as a 
capsule naturally fertilised ever produces. Moreover 
the pollen from a single anther is far more than suffi- 
cient to fertilise fully a stigma ; hence, in this as with 
so many other plants, more than twelve times as much 
of each kind of pollen is produced as is necessary to 
ensure the full fertilisation of each form. From the 
dusted condition of the bodies of the bees which I 
caught on the flowers, it is probable that pollen of 
various kinds is often deposited on all three stigmas ; 
but from the facts already given with respect to 
the two forms of Primula, there can hardly be a 
doubt that pollen from the stamens of corresponding 
length placed on a stigma would be prepotent over 
any other kind of pollen and obliterate its effects, 
— even if the latter bad been placed on the stigma 
some hours previously. 



LTl-HBUM GK^FFERI. 



165 



I 



Finally, it has now been shovro that Lythrum mUcaria 
presents the extraordinary case of the same species 
bearing three females, different in structure and func- 
tion, and three or even five sets {if minor differences 
are considered) of males ; each set consisting of half- 
a-dozen, which likewise diffor from one another in 
structure and function. 



Lythrum Grmffei-i. — I have esamined nimierona dried flowers 
of this BpecieB, each from a separate plant, eent me from Eew. 
Like L. saliraria, it is trimorpMc, and the three forms appa- 
tentlj occur in about equal numbers. In the long-etyled form 
the pistil projects about one-third of the length of the calyx 
beyond its mouth, and is therefore relatively much shorter than 
in L. ealiairia ; the globose and hirsute Btigma is larger than 
that of the other two fonns ; the sis mid-length stamens, which 
are graduated in length, have their anthers stauding dose above 
mud close beneath the mouth of the calyx; the six shortest 
Btomens rise rather aboTO the middle of the calyx. In the mid- 
styled form the stigma projects just above the mouth of the 
calyx, and stands almost on a level with the mid-length stamens 
of the long and short-atyled forms; its own longest stamens 
project well alove the mouth of the calyx, and stand a little 
above the level of the stigma of the long-styled form. In short, 
without entering on further details, there is a close general 
correspondence in structure between this species and £. salicaria, 
but with some differences in the proportional lengths of the 
parts. The fact of each of the three pistils having two sete of 
stamens of corresponding lengths, borne by the two other forms, 
comes out conspicuously. In the mid-styled form the pollen- 
grains from the longest stamens are nearly double the diameter 
of those firom the shortest stamens; so that there is a greater 
difference in this respect than in L. salicaria. In the long- 
Btyled form, also, the difference in diameter between the pollen- 
grains of the mid-length and shortest stamens is greater than 
in i. Ba'icariQ. Tliese comparisons, however, must be received 
with caution, as they were mode on specimens soaked in water 
after having been long kept dry. 

Lytkntm thjmi/oUa.— This form, according to Taucher,* it 



'Hiat, Pliyg. <!ca Plnntua d'Europe,' i 



L(lMI),pp.3(19, 371. 



ICG HETEKOSTYLED TltmOEPHIO PLANTS. Cuiw. Ifl 

dimorphic, like Primula, and therefore preeents onlf two formftl 
I received two dried flowers from Kew, which coDsistsd of tha 
two forms ; in one the etigma projected far beyond the c»1yx, in 
the other it was inclnded within the calji ; in this latter form 
the etjle was only one-fourth of the length of that in the other 
form. Tliero are only six Etomens ; thsRO are somewhat grada- 
ated in length, and their ontliera in the short-stjled form stand 
a little above the stigma, hut yet hy no moans equal in lengith 
the pistil of the long-styled form. In the latter the stamens 
are rather ehorter than those iu the other form. The six 
stamens nltemato with the petals, and therefore correspond 
homologically with the longest stamens of L, salkana and L. 
Or^fferi. 

LythTum hyssqpi/olia.^Tli'ia species is said by Toucher, but I 
believe erroneoUBly. to be dimorphic. I have examined dried 
flowers from twenty-two separate plants irom various localities. 
Bent to me by Mr, Hewett C. Watson, Professor Babington, and 
others. Those were all essentially ahke, so that the species 
cannot be het^rostyled. The pistil varies somewhat in length, 
but when unusually long, the stamens are hkewise generally 
long; in the bud the stamens are short; and Vancher was 
perhaps thus deceived. There are from sis to nine stamens, 
graduated in length. The three stamens, which vary in being 
either present or absent, corrospond with the six shorter stamens 
of L. aaliaiTia and with the eii which are always absent in L. 
thymifdlia. The stigma is included witMn the calyx, and stands 
in the midst of the anthers, and would generally be fertilised 
by them ; but as the stigma and anthers are upturned, and as, 
according to Vauctier, there is a passage left in the upper side 
of the flower to the nectary, there can hardly be a doubt that 
the flowers are visited by insects, and would occasionally bo 
cross-fertilised by them, as surely as the flowers of the short- 
styled L. saikaria, the pistil of which and the corresponding 
stamens in the other two forms closely reEemt)Ie those of L. hya- 
soinfolia,. According to Vaucher and Locoq,* this species, whicb. 
is an annual, generally grows almost solitarily, whereas thai 
three preceding species are social ; and this fact alone wotdcl , 
almost have convinced me that L. hyss'tpifdlia was not heten>«- 
Btyled, as such plants cannot habitually live isolated any bettat 
than one Bes of a dicecious species. 



% 



' Gifograph. Bot. de I'Europi?,' Una. vi. IS57, p. 157. 



cuiP. :v 



LAGEESTKCEMIA INDICA. 



167 



We thus SCO that withiu tbis genuB some species are hetero- 
atyled and trimorpMc ; one apparently heterostyled and diroor- 
pliic, and one homoatjled. 

A'eSiTO vcrticitlala.—! raised ft number of plants from seed 
B^nt mo by Professor Asa Gray, and they presented tbree forms. 
Tiieso differed from one anotber in tbe proportional lengths ot 
tbeir organs of fructification and in all respects, in very nearly 
the same way as tbe tbree forms of Li/thrum Grmferi. Tbe 
green pollen-grains irom the longest stamens, measured along 
their longer aiis and not distendod with water, were ,J3ii of *n 
inch in length ; tboso from tbe mid-length stameus ^ and 
those from tbe shi)rtest stamens ^ of an inch. So that the 
largest pollen-grains are to the smaUest in diameter as 100 to 
65. This plant inhabits swampy gronud in the United States. 
According to Fritz Mtiller,* a species of tbis genus in St. Catha- 
rina, in Southern Brazil, is homostyled. 

Lagtrsiraimia Indlca. — This plant, a member of the Lythracee, 
may perhaps be heterostyled, or may formerly have been so. It 
is remarkable from the extreme Tariabihty of its stamens. On 
a phint, growing in my hothouse, the flowers included from 
nineteen to twenty-nine short stamens with yellow pollen, 
■which correspond ia position with the shortest stamena of 
Lytbrum; and from one lo five (the latter number being the 
commonest) very long stamens, with thick flesh-coloured fila- 
ments and green pollen, corresponding in position with the 
longest stamens of Lythrum. In one flower, two of the long 
stamens produced gi'een, wbiie a third produced yellow pollen, 
although the filaments of all three were thick and flesh-coloured. 
In an anther of another flower, one cell contained green and 
the otlier yellow pollen. The green and yellow pollen-grains 
from the stamena of different length are of tbe same size. 
The pistil is a little bowed upwards, with the stigma seated 
between the anthers of the short aud long stamens, so that 
this plant was mid-styled. Eight flowers were fertilised with 
green pollen, and six with yellow pollen, but not one sot fruit 
This latter &ct by uo means proves that tbe plant is hetero- 
styled, afl it may belong to the class of self-sterile species 
Anotber plant growing in the Botanic Gardens at Calcutta, as 
Mr- J. Scott informs me, was long-atyled, and it was equally 



V 



'DoLZciil 



,-lSC8, p. 112. 



168 HETEHOSTYLED TBDflOEPHIO PLANTS. Chap. 1 

sterile with its own pollen; whilst a long-atyled plant c 
L. Tegina, though growing bj itself, produced fruit, I examined 
dried flowers from two plimta of L. parviflora, both of whioli 
were long-atyled, and tbey diffored from L. Jndiai in having 
eight long BtamenB with thick filaments, and a crowd of shorter 
stamens. Thus the evidence whether L. Jndica is hetero- 
styied is coriouBly conflicting: the unequal nombei' of the short 
and long stamens, their eitreme variability, and especially the 
fact of their pollen-grains not differing in size, are strongly 
opposed to this belief; on the other hand, the difference in 
length of the pistils in two of the plants, their sterility with. 
their own pollen, and the difi'erence in length and structure of 
the two seta of stamens in the same flower, and in the colour of 
their pollen, favour the belief. We know that when plants of 
any kind revert to a former condition, they are apt to be highly 
variable, and the two halves of the same organ sometimes diSer 
mnch, OS in the case of the above-described anther of tb6u 
Lagerstnmnia ; we may therefore suspect that this species wa> J 
once heterostyled, and that it still retains traces of its former 
state, together with a tendency to revert more completely to it. 
It deserves notice, as bearing on the nature of Lagcrstrcemift, 
that in Lyihrttm ^j.isopi/oIiajWhichisahomostyled species, some 
of the shorter stamens vary in being either present or absent; 
and that these same atamena are altogether absent in L. thymi' 
folia. In another genus of the Lytbracefe, namely Cuphea, three' J 
species raised by me from seed certainly were horaostyled;. 
nevertheless their stamens consisted of two seta, differing io.J 
length and in the colour and thickness of their filaments^ but I 
not in the size or colour of their pollen-grains ; so that they ■% 
thus far rusemblod the stamens of Lagerstrcemia. I fonnd l^ta 
Cuphea purpurea was highly fertile with its own pollen when J 
artificially aided, but sterile when insects were eiclnded.* 

* Mr. Sponco iiifnrmB mo tliat 
in eeveml species of tha geuua 
Mollia (Tiliancn) whi^h ho col- 
lected in South America, the 
BtamanH of the five oatcr cohorts 
hare pnrptieh tilaiuenta and green 
pDllen, whilst the stnmena of the 
five inner cohorts haTe yellow 
PdUdu. He therefore iiispeoted 
that thosB BiHiaies miglit pmve 
to be bcteroittylod niid trimnr- 



OxALis (Gerahiace^). 
Ill 1863 Mr. Roland Trimen wrote to me fram the 
Cape of Good Hope that lie had there found speciea of 
Oxalis which presented three forms ; and of theae he 
enclosed drawings and dried specimens. Of one species 
he collected 43 flowers from distinct plants, and they 
consisted of 10 long-styled, 12 mid-styled, and 21 
short-styled. Of another species he collected 13 flowers, 
consisting of 3 long-styled, 7 mid-styled, and 3 short- 
styled. In 1866 Prof. Hildebrand proved* by an ex- 
amination of the specimens in several herbaria that 20 
species are certainly heterostyled and trimorphic, and 
51 others almost certainly so. He also made some in- 
teresting observations on living plants belonging to 
one form alone ; for at that time he did not possess 
the three forms of any living species. During the 
years 1864 to 1868 I occasionally experimented on 
Oxalia upeciosa, but until now have never found time 
to publish the results. In 1871 Hildebrand published 
an admirable paperf in which he shows in the case of 
two species of Uxalis, that the sexual relations of the 
three forms are nearly the same as in Lythrum soli- 
carta. I will now give an abstract of his observa- 
tions, and afterwards of my own less complete ones. 
I may premise that in all the species seen by me, the 
gtigmas of the five straight pistils of the long-styled 
form stand on a level with the anthers of the longest 
ntamena in the two other forms. In the mid-styled 



nppermoat uithora. Tho n 
■t^ens ore graduiited in length, 
and the p(ilIeQ-gtHL]iB bom ths 
longcBt and ahortant ones did Dot 
it any matkod difTereiine in 
ter. Therefore tb^cspei'iea 
>t appear to be be(t;[QBt;led. 



diameter 



* 'Monatabcr. der Akad. der 
WisB. Bsrliii,' 186ti, pp. S52, 372. 
I[q glvea drawings of the there 
forms lit p. 42 of hia •GesohloLhfcr- 
VerthiilunK.' 4o„ 1887. 

+ 'Bot. Zaitimg,' 1871, pp. 41G 
nnd 432. 



170 HETEHOSTYLED TBIMORPHIO PLiSTS. Caw. ITa| 

form, tlie stigmas pass out between the filamen 
the longest stamona (as in the short-styled form of 
Linum); and they stand rather nearer to the upper 
anthera than to the lower ones. In the short-stylgd 




form, the stigmas also pass out between the filaments 
nearly on a level with the tips of the sepals. The 
anthera in thia latter form and in the mid-styled rise 
to the same height as the corresponding stigmas in the 
other two forms. 

Oxalis Valditiana. — Thia species, an iuhabitant of 
the west coast of Sonth America, bears yellow flowers. ' 
Hildehrand states that the stigmas of the three foima 
do not differ in any marked manner, but that the pistil 
of the ahort-styled form alone is destitute of hair& 
The diameters of the pollen-grains are as follows :- 



the loDEtst 


sUa 


nsof 


>hort-st}-[«d . 




mld-l* 


gth 


„ 


T. 




l0Dg«, 




EDS of 


■Did-stfled . 




shortes 


t 


„ 


„ 




mU-le 


gth. 


amen 


s of long-.lj!ea 




Jiortt 




„ 


n 





Chap. IV. 0XALI8 VALDIVIANA. 171 ^H 

Therefore the extreme difiFerence in diameter is as 8-5 ^H 
to 6, or as 100 to 71. The reaults of Hildebrand's ei- ^M 
periments are given in the following table, drawn np ^H 
in accoi-dance with my usual plan. He fertilised each ^H 
form with pollen &om the two sets of anthers of the ^^| 
some flower, and likewise fi'^om flowers on distinct ^^| 
plants belonging to the same form; but the effects ^H 
of these two closely allied kinds of fertilisation differ ^H 
so little that I have not kept them distinct. ^H 

Tablb ^M 
OxalU Valdividna (Jrom Eildebrand). ^| 


M«lur« i.1 Union. 


Flonen 
tonlilbeJ. 


r^^i«, 


Homlw 


LoBgrttjled form, by pollen of loDgesi; 
ibimeus of sliort-btyled. Legilimato 


28 


2B 


11-9 




LoDg-Btjrlad fonti, by pollen of longest, 
■tarnen* of mid-styled. Legitimate 


21 


2! 


120 




Long-Jtyled form, by pollen of own andj 
own-form mid-length stamens. Illagiti- 
matsunien j 


40 




5-5 


Long-styled form, by pollen of own >i>di 
mate union | 


Jii 





" 


sUrnena of shoit-atyled. Illegitimate 


lij 


■ 


I 






• 


» 







i ^ 



^V 172 HETEEOSTYLED TEIMOBrmc PLANTS Chip. IV 

^V Table ZT-contimmi. 

^m OxalU Valdiviana {from Bildtbrand). 


^H KilBnrfCnion. 


°5 


Hnmbsr 

or 


Knmbei 

Seedapar 

CapMle. 


^H Mid-«t;Wrorm,b7i>oll<Ddfm|d-leagthsta-1 


„ 


38 


„.3 


^m Mid-Etyled furm, by pollen of tni<l-l?ngth { 
^1 jlnmens of ehort-Btyled. Usltiu^itej 


23 


23 


,., 1 






^H Mid^tjied foi'm, bf pollen of Dim madl 


53 





4 




H Mid-styled foTO, by polUn nf own .ndl 
^H own-forniahiirtaitsUmona. Illegitimate 


30 


■ 


6 




^ Mid-styled form, by pollen of «h<irte^t 
■tameos of long-stjled. lUegitinute 


16 


° 







Mid-styled form, by pollen uf longest sta.\! . . 
mensufshorl^stjled. Ulegitimnto union/j '" 


« 


a-5 


Short-elylod form, by pollen of ahottMtstfl-V „ 
mem of long-styled. Legitimate onion ./ 


18 


ll'O 


men.ormid-etyU'^ Ugitimate DBion . } ^^ 


10 


„. 


^m Shnrt-stjied form, by pollen of own and 
^^ own-form longest slameiia. Illegitimate 


21 





' g 




^ Shoit-stjled form, by pollen of own audi' 
mate union ) 





■ 1 


Short-styled form, bj pollen of longest >ta-l , 
mensofmld-stjled. 11 legitimate anion/ * 


» 


- 1 


Short-etyled form, by pollen of mid -length j 


3 





- 1 


^ 




I :i 



OXALIS EEGNELLL 



We here have the i 



orkable result that every one 



I 



of 138 legitimately fertilised flowers on the three forma 
yielded oapsulea, containing on an average 11 ■ 33 seeds. 
Whilst of the 255 illegitimately fertilised flowers, only 
6 yielded capsules, which contained 3 '83 seeds on an 
average. Therefore the fertility of the six legitimate 
to that of the twelve illegitimate imions, as judged 
by the proportion of flowers that yielded capsules, is 
as 100 to 2, and as judged by the average number of 
seeds per capsule as 100 to 34. It may be added that 
some plants which wore protected by nets did not 
spontaneously produce any fruit ; nor did one which 
was left uncovered by itself and was visited by bees. 
On the other hand, scarcely a single flower on some 
uncovered plants of the three forms growing near 
together failed to produce fruit. 

OxaJia Re^nelll. — This species bears white flowers 
and inhabits Southern Brazil. Hildebrand says that 
the stigma of the long-styled form is somewhat larger 
than that of the mid-atyled, and this than that of the 
ahort-styled. The pistil of the latter is clothed with a 
few hairs, whilst it is very hairy in the other two 
forms. The diameter of the pollen-grains from both 
seta of the longest stamens equals 9 divisions of the 
micrometer, — that from the mid-length stamens of the 
long-styled form between 8 and 9, and of the short- 
atyled 8, — and that from the shortest stamens of both 
sets 7. So that the extreme difference in diameter is 
as 9 to 7 or as 100 to 78. The experiments made by 
Hildebrand, which are not so numerous as in the last 
case, are given in Table 28 in the same manner as 
before. 

The results ore nearly the same as in the lost case, 
but more striking ; for 41 flowers belonging to the 
three forms fertilised legitimately all yielded capsules. 



^V L71 HETEBOBTTLED TBIMOEFHia PLANTS. Ckap. ]^^^^| 

^g OiMlb Beg^Ali (from mUtbra.,d). ^^| 


^1 NMar* of DdIdo. 


SuMia 

FIg-ers 
tenrlliul. 


IJCWluod. 


mm 


^H LoDg-Btrled rorm, bf pollen of Inngest sIh-1 
^H mem of abort-etylad. Legitimate iiniun J 


• 


6 


10-1 ^^1 


^H Long-styled rnnn, bj polka af toDgest sU-\ 
^H mena of miJ-^tjIed. tegitimau tmloa / 


5 


S 


10-e ^^1 


^H LoDg-Btyled form, bj pollen of own mid-| 
^H length stsmena. illcgitimste union . | 







- 1 


^H Long-itjled form, hy poliea of own Bhort-I 


1 





' % 


^1 Mid-atyled form, by pollen of mid-lengthita-l 
^H mens of short-styled. Legitimate nnionj 


9 


9 


10-4 


^B Mi J^tyled form, by pollen of mid-length sta-l , , 
B mensoflong-etjled. Legitimate union. /| 


10 


10-1 


^H Uid-styled form, by pollen of own loDgestl . 
■ ,t,mW IllegilTatennlon . f .|| « 







^H Uid-Btyled form, by pollen of dwd shortestt „ 
■ stamens, lllegitim.l. union . . ./j = 







^H Mi^-atylcd form, by pollen of longest sta-) 
^H mens of short-styled. lUegilimate anionj 









^H Sbort-styledrorm,bypolleDofBhcrteat sta-l 
^■~ mensofmid-stjled. Legitimate onion. J 


9 


9 


10-8 


^H Sbort-styled form, by pollen of shortest sta-) 
^H mens of long-styled. Legitimate anion. J 


^ 


o 


9-5 


^H Sborl-atjled form, by pollen of own mid-\ 
^H length stamens. Illegitimate union .j 


12 








^H Sbort-etylod form, by pollen of own long-1 
^M estftaniens. lUegitimiae unicn . .J 


S 








^H Short-styled form, by pollen of mid-length 1 
^1 stamens of long-styled. Illegitimate] 


■ 








^1 


L A 



OXALIS SFECIOSA. 



175 



containing oa an average 10 '31 seeds; whilst 39 
flowers fertilised illegitimately did not yield a single 
capsule or seed. Therefore the fertility of ttie six 
legitimate to that of the several illegitimate unions, 
as judged both by the proportion of flowers which 
yielded capsules and hy the average number of con- 
tained seeds, is as 100 to 0. 

Oxcdia speciosa. — This species, which bears pink 
flowers, was introduced irom the Cape of Good Hope. 
A sketch of the reproductive organs of the three 
forms (Fig. 11) has already been given. The stigma 
of the loug-styled form (with the papilla} on its sur- 
face included) is twice as large as that of the short- 
styled, and that of the mid-styled intermediate in size. 
The pollen-grains from the stamens in the three forms 
are in their longer diameters as follows : — 



e iungest Etameaa of short-stjled. 

nid-lesglh „ „ 

longest btamens of miil-stylHl . 



Diid-leDgih si 



. of long-styled , 



Therefore the extreme difference in diameter is as 
16 to 11, or as 100 to 60; but as the measurements 
were taken at different times, they are probably only 
approximately accurate. The results of my experiments 
in fertilising the three forma are given in the following 
table. 



l76 hetebostyled tbimobphic plants. ciur. i^^^h 
Tabu 29. ^^| 


1 Maraber 


Bamber 

Capinlrt 
prudoad. 


SF 


LoDE-atyled furm, br polleD of iDDgestj 
Blatuepi of ibort-ityled. UgitimaU 


IS 


15 


57-4 




Ung-8tyUd form, by pollen at longest 
.tamenji of mid-.tyled. Legitimate 




3 


590 




Long-styled form, by pollen of own-forml! -, 
mid-length atamena. Ulegilimiite union/ 


S 


42'5 


Long-styled form, by pollen of own-forml 
tborteat stumeus. illegitimate union .J 










Ung.«(yled forni, by pollen of abortotl 
itameua of mid-atjled. lllegitimato 












Long-Styled form, by pollen of mid-lengtb 
stamen* of short-styied. Illegitimate 


12 


5 


30-0 


Mid-atyled form, b^ pollen of mid-length] 
■tamena of long-styled. Legitimate 


3 


3 


S3'e 




Mid-styled form, by pollen of mid-length 1 
atameni of aborC-ityled, Legitimate 


4 


^ 


5a-3 




Hid-styled form, by miied pollen froml 

both own-farm longest and ahortestf 9 
wamen^ Illegitimate nnion . . .\^ 


2 


19 


Mid^tyled form, by pollen of longostl 
stamens of short-styled. IllegitiniaM 


12 


1 


B 




k_ J 



Ohaf. IV. OXALIS BrEGIOSA. 17" ^^| 


»-■— '■"•- i^™™ 


Gtpgtilo 1 Seals per ^H 
prudu^nL Ogsolii ^^H 


»s:r.?^?^.fft^sr 




■' 


67 




";^r.fz.-s-i^S£ 


3 


3 


G4 3 




Sb.*..,W,.™.b„.„...,....f.™| 


5 


1 


e 


^'£!SS^=;S;ll;;;Lz*=} 


3 


D 


D 


■ss^ssm 


13 


» 





^'rr./"zjXfi".."Usj 


7 








■^si^iTij'^si'^sa;) 


ID 


1 


M 


We here see tliat thirty-six flowers on the three ^H 
* forms legitimately fertilised yielded 30 capsules, these ^^| 
containing on an average 58'36 seeds. Ninety-fiTo ^H 
flowers illegitimately fertilised yielded 12 capsules, ^H 
containing on an average 28 '58 seeds. Therefore the ^^| 
fertility of the six legitimate to that of the twelve ^H 
illegitimate unions, as judged by the proportion of ^H 
flowers which yielded capsules, is as 100 to 15, and ^H 

100 to 49. This plant, in comparison with the two ^H 
South American species previously described, produces ^H 



178 HETEBOSTTLED TRniOBPHIC PLANTS. Coaf TV. 

many more seeds, and the iUegitimately fertilised 
Bowers are not quite so sterile. 

Oxalis rosea. — Hildebracd possessed in a living state 
only the long-styled form of this trimorphic Chilian 
species." The polleu-grains from the two sets of J 
anthera diSer in diameter as 9 to 7 '5, or aa 100 to 83. 1 
He has further shown that there is an analogous , 
difference between the grains from the two sets <rf 
anthers of the same flower in five other species of Oxalis, 
besides those already described. The present species 
differs remarkably from the long-atyled form of the 
three species previously experimented on, in a mnch 
larger proportion of the flowers setting capsules when 
fertilised with their own-form pollen. Hildebrand fer- 
tilised GO flowers with pollen from the mid-length 
stamens (of either the same or another flower), and 
they yielded no less than 55 capsules, or 92 per cent. 
These capsules contained on an average 5 "62 seeds; 
but we have no means of judging how near an approach 
this average makes to that from flowers legitimately 
fertilised. He also fertilised 45 flowers with pollen 
from the shortest stamens, and these yielded only 17 
capsules, or 31 per cent., containing on an average 
only 2 '65 seeds. We thus see that about thrice as 
many flowers, when fertilised with pollen from the 
mid-length stamens, produced capsules, and these • 
contained twice as many seeds, as did the flowers 
fertilised with pollen from the shortest stamens. 
It thus appears (and we find some evidence of ' 
the same fact with 0. iipectosa), that the same rule ■ 
holds good with Oxalis as with Lr/lhrum salicaria; | 
namely, that in any two unions, the greater the in- 
equality in length between the pistils and stamens, or. 



Ucrlln/ 1866, p. 873. 




OXALIS, OTHEB BFBCIIIS OF 



179 



I 
I 

I 
I 



which is the same thing, the greater the distance of 
the stigma from the anthers, the pollen of which ia 
used for fertilisation, the less fertile ia the union, — 
whether judged hy the proportion of flowers which 
set capsules, or by the average number of seeds per 
capsule. The rule cannot be explained in this case 
any more than in that of Lythrum, by supposing 
that wherever there is greater liability to self-fertilisa- 
tion, this is checked by the union being rendered more 
sterile ; for exactly the reverse occurs, the liability to 
self-fertilisation being greatest in the unions between 
the pistils and stamens which approach each other the 
nearest, and these are the more fertile. I may add 
that I also possessed some long-styled plants of this 
species : one was covered by a net, and it set sponta- 
neously a few capsules, though extremely few com- 
pared with those produced by a plant growing by 
itself, but exposed to the visits of bees. 

With most of the species of Oxalis the short-styled 
form seems to be the most sterile of the three forms, 
when these are illegitimately fertilised ; and I will add 
two other cases to those already given. I fertilised 
29 short-styled flowers of 0. eompressa with pollen from 
their own two sets of stamens (the pollen-grains of 
which differ in diameter as 100 and 83), and not one 
produced a capsule. I formerly cultivated during 
several years the short-styled form of a species pur- 
chased under the name of 0. Bowii (but I have some 
doubts whether it was rightly named), and fertilised 
many flowers with their own two kinds of pollen, 
which differ in diameter in the usual manner, but 
never got a single seed. Oq the other hand, Hilde- 
brand says that the short-styled form of 0. Deppei, 
growing by itself, yields plenty of seed ; hut it is not 
positively known that this species is heteroatyled ; and 



^m mtrodu 



180 HETEEOSTYLED TEOIOKPIUO PLANTS. Chap. IT 

the polleQ-graios £rom the two sets of anthers do not 
differ in diameter. 

Some facts commiinicated to me by Fritz Mallei 
afford excellent evidence of the utter sterility of one 
of the forma of certain trimorphic species of Oxalis, 
when growing isolated. He has seen in St Catharina, 
in Brazil, a large field of young augar-cano, many 
acres in extent, covered with the red blossoms of one 
form alone, and these did not produce a single seed. 
His own land ia covered with the shott-styled form of 
a white-flowered trimorphic species, and this is equally 
sterile ; but when the three forms were planted near 
together in his garden they seeded freely. With two 
other trimorphic species he flnda that isolated plants 
are always sterile. 

Fritz Mailer formerly helieved that a species of 
Oxalis, which is so abundant in St. Catharina that it 
borders the roads for miles, was dimorphic instead of 
trimorphic. Although the pistils and stamens vary 
greatly in length, as was evident in some specimens 
sent to me, yet the plants can be divided into two 
sete, according to the lengths of these organs. A 
large proportion of the anthers are of a white colour 
and quite destitute of pollen ; others which are pale 
yellow contain many bad with some good grains ; and 
others again which are bright yellow have apparently 
sound pollen ; but he has never succeeded in finding 
any fruit on this species. The stamens in some of 
the flowers are partially converted into petals. Fritz 
Muller after reading my description, hereafter to be 
given, of the illegitimate offspring of various hetero- 
styled species, auspecte that these plants of Oxalis 
may be the variable and sterile offspring of a single 
form of some trimorphic species, perhaps accidentally 
introduced into the district, which hna since iH^en 



I 



Ceap. IV. 0XALI8, HOMOSTYLED SPECIES. 181 

propagated asexually. It is probable that thia kind 
of propagatioa would be mueh aided by there beiug 
Qo expenditure in the production of seed. 

Oxalis {Siopkytum) sensitive. — This plant is ranked 
by many botanists as a distinct genus. Mr. Tliwaitea 
sent me a number of flowers preserved in spirits from 
Ceylon, and they are clearly trimorphic. The style 
of the long-styled form is clothed with many scattered 
haiis, both simple and glandular; such hairs are much 
fewer on the style of the mid-styled, and quite ab- 
sent from that of the short-styled form ; so that this 
plant resembles in this respect 0, Yaldiviana and 
RegneUi. Culling the length of the two lobea of 
the stigma of the long-styled form 100, that of 
the mid-stylod is 141, and that of the short-styled 
164. In all other cases, in which the stigma in this 
genus differs in size in the three forms, the differ- 
ence is of a reversed nature, the stigma of the long- 
styled being the largest, and that of the short-styled 
the smallest. The diameter of the poUon-grains from 
the longest stamens being represented by 100, those 
from the mid-length stamens are 91, and those from 
the shortest stamens 84 in diameter. This plant is 
remarkable, as we shall see in the last chapter of 
this volume, by producing long-styled, mid-styled, 
and flhort-atyled cleistogamic flowers. 

Soniostijled Species of Oxalis. — Although the majority 
of the species in the large genus Oxalis seem to be 
trimorphic, some are homostyled, that is, exist under 
a single form ; for instance the common 0. acelo- 
stUa, and according to Hildebrand two other widely 
distributed European species, 0. atrieta and comtculala. 
Pritz Muller also informs me that a similarly consti- 
tuted species is found in St. Catharina, and that it is 



182 HETEEOSTYLED TBIMOEFHIC PLANTS. Cbap. IV 

quite fertile with ita own poUen when insects are ex- 
cluded. The stigmas of 0. strtcta and of another homo- 
styled species, viz. 0. tropiBoloides, commonly stand on 
a level with the upper anthers, and both these species 
are likewise quite fertile when insects are excluded. 

With respect to 0. acetoseUa, Hildebrand says that in 
all the many specimens examined by him the pistil 
exceeded the longer stamens in length. I procured 
108 flowers from the same number of plants growing in 
three distant parts of England ; of these 86 had their 
stigmas projecting considerably above, whilst 22 had 
them nearly on a level with the upper anthers. In 
one lot of 17 flowers from the same wood, the stigmas in 
every flower projected fully as much above the upper 
anthers as these stood above the lower anthers. So 
that these plants might fairly be compared with the 
long-styled form of a heterostyled species ; and I at 
first thought that 0. ocetaeeRa was trimorphic. But 
the case is one merely of great variability. The 
pollen-gi'ains from the two sets of anthers, as observed 
by Hildebrand and myself, do not differ in diameter. 
I fertilised twelve flowers on several plants with pol- 
len from a distinct plant, choosing those with pistils 
of a different length ; and 10 of these (i.e. 83 per cent,) 
produced capsules, which contained on an average 7-9 
seeds. FoTirteen flowers were fertilised with their own 
pollei:, and 11 of these (i.e. 79 per cent.) yielded cap- 
sules, containing a larger average of seed, namely 9'2. 
These plants, therefore, in function show not the 
least sign of being heterostyled, I may add that 18 
flowers protected by a net were left to fertilise them- 
selves, and only 10 of these (i.e. 55 per cent.) yielded 
I, which contained on an average only 6'3 seeds. 
So that the access of insects, or artificial aid in placing 
pollen on the stigma, increases the fertility of the 





PONTEDEBIA. 



183 



r flowers ; and I found that this applied i 

' those having shorter pistils. It should 

I bered that the flowers hang downwards, so that those 

with short pistils would be the least likely to receive 

their own pollen, unless they were aided in some 



I 



I 



Finally, as Hildebrand has remarked, there is no 
evidence that any of the heterostyled species of Oxalis 
are tending towards a dioecious condition, as Zuccarini 
Mid Lindley inferred from the differences in the re- 
productive organs of the three forms, the meaning of 
which they did not understand. 

POHTEDEBIA [SP. ?] (POSTEDEEIACE^.) 

Fritz Muller found this aquatic plant, which is al- 
lied to the Liliaceie, growing in the greatest profusion 
on the banks of a river in Southern Brazil." But only 
two forms were found, the flowers of which include 
three long and three short stamens. The pistil of the 
long-styled form, in two dried flowers which were sent 
me, was in length as 100 to 32, and its stigma as 100 
to 80, compared with the same organs in the short- 
styled form. The long-styled stigma projects conside- 
rably above the upper anthers of the same flower, and 
stands on a level with the upper ones of the short-styled 
form. In the latter the stigma is seated beneath both it3 
own sets of anthers, and is on a level with the anthers 
of the shorter stamens in the long-styled form. The 
anthers of the longer stamens of the short-styled form 
are to those of the shorter stamens of the long-styled 
form as 100 to 88 in length. The poUen-grains distended 



L 



184 HETEB08TYT.ED TEtMOHPHIC PLANTS. Chaf. IV. 

with water from tlie longer stamens of the short-styled 
form are to those from the shorter stamena of the same 
form as 100 to 87 in diameter, as deduced from ten 
measurementB of each kind. We thus see that the 
organs in these two forms differ from one another 
and are arranged in an analogous manner, as in the 
long and short-atyled forms of the trimorphic species 
of Lythrum and Oxalis. Moreover, the longer stamens 
of the long-styled furm of Pontederia, and the shorter 
ones of the ahort-styled form are placed in a proper 
position for fertilising the stigma of a mid-styled form. 
But Fritz Miiller, although he examined avast numher 
of plants, could never find one belonging to the mid- 
styled form. The older flowers of the long-styled 
and short-styled plants had set plenty of apparently 
good fruit ; and this might have heen expected, as 
they could legitimately fertilise one another. Al- 
though he could not find the mid-styled form of 
this species, he possessed plants of another species 
growing in his garden, and all these were mid-styled ; 
and in this case the pollen-grains from the anthers of 
the longer stamens were to those from the shorter sta- 
mens of the same flower as 100 to 86 in diameffir, as 
deduced from ten measurements of each kind. These 
mid-styled plants growing by themselves never pro- 
duced a single fruit. 

Considering these several facts, there can hardly be 
a doubt that both these species of Pontederia are 
heterostyled and trimorphic. This case is an interest- 
ing one, for no other Monocotyledonous plant is known 
to be heterostyled. Moreover, the flowers are irregular, 
and alt other heterostyled plants have almost sym- 
metrical flowers. The two forms differ somewhat in 
ths colour of their corollas, that of the short-styled 
being of a darker blue, whilst that of the long-styled 



' Chap. IV. 



PONTEDEHIA. 



185 



teniia towards violet, and no other such case is known. 
Lastly, the three longer stamens alternate with the 
three shorter ones, whereas in Lytlirum and Oxalia 
the long and short stamens belong to distinct whorls. 
With respect to the absence of the mid-styled form in 
the ease of the Pontederia which grows wQd in Southern 
Brazil, this would probably follow if only two forms 
had been originally introduced there ; for, as we shall 
hereafter see from the observations of Hildebrand, 
Pritz Miiller and myself, when one form of Oxalis is 
fertilised exclusively by either of the other two forms, 
the offspring generally belong to the two parent- 
forms. 

Fritz MiiUer has recently discovered, as he informs 
me, a third species of Pontederia, with all three forms 
growing together in pools in the interior of S. Brazil ; 
80 that no shadow of doubt can any longer remain 
about this genus including trimorphic species. He 
sent me dried flowers of all three forms. In the long- 
styled form the stigma stands a little above the tips of 
the petals, and on a level with the anthers of the 
longest stamens in the other two forms. The pistil is 
in length to that of the mid-styled as 100 to 56, and 
to that of the short-styled aa 100 to IC. Its summit is 
rectangularly bent upwards, and the stigma is rather 
broader than that of the mid-styled, and broader in 
about the ratio of 7 to 4 than that of the short-styled. 
In the mid-styled form, the stigma is placed rather 
above the middle of the corolla, and nearly on a level 
with the mid-length stamens in the other two forms ; 
its Bommit is a little bent upwards. In the short- 
Btyled form the pistil ia, aa we have seen, very short, 
and differs from that in the other two forms in being 
straight. It stauda rather beneath the level of the 
anthers of the shortest stamens in the long-styled and 



166 HBTBBOSTYLED TBIHOBPHIC PLANTS. Cup. IT. 

mid-Btyled forms. The tliree anthers of each set of 
■tamcna, moie especially those of the shortest stameDs, 
are placed one bonoath the other, and the ends of the 
filaments are howed a little upwards, so that the pollen 
from all the anthers would be effuctivcdy brushed ofE 
by the proboscis of a visiting insect. The relative 
diameters of the pollen-grains, after having been long 
Soaked in water, are given in the following list, 
measured by my son Francis. 



UofiiyM form, from tht miil-length ituneru . . 


. 13- 


(Average of 20 measnroraenU.) 




from th. shortest Hamena . . . 


9- 






lIU-.t7l«l form, from tho longest Blamen. . . . 


. 16- 






„ „ l^om th« ahorteat stamens . . . 


. B- 








. !*■ 






from the mld-leogtb Btameni , 


. 13- 



•' 



(20 me^suremedta.) 

We have here the usual rule of the grains from the 
longer stamens, the tubes of which have to penetrate 
the longer pistil, being larger than those irom the 
stamcua of less length. The extreme difference in 
diameter between the grains from the longest stamens 
of the mid-atyled form, and from the ahoitest stamens 
of the long-stylod, is as 16 ■ 4 to 9 ■ 0, or as 100 to 55 j 
and this is the greatest difference observed by me in 
any heterostyled plant. It is a singular fact that the 
grains from the corresponding longest stamens in the 
two forms differ considerably in diameter ; as do those 
in a lesser degree from the corresponding mid-length 
stamens in the two forms ; whilst those from the cor^ 
responding shortest stamens in the long- and mid- 
styled forms are almost exactly equal. Their in- 
equality in the two first cases depends on the graini 



I Cbap. it. 



PONTEDEBIA. 



187 



in both sets of onthers in the short-styled form being 
smaller than those from the corresponding anthers in 
the other two forma ; and here we have a case parallel 
with that of the mid-styled form of Lythrum salicaria. 
In this latter plant the pollen-grains of the mid-styled 
forms are of smaller size and have less fertilising power 
than the corresponding ones in the other two forms ; 
whilst the ovarium, however fertilised, yields a greater 
number of seeds ; so that the mid-styled form is alto- 
gether more feminine in nature than the other two 
forms. In the case of Poatederia, the ovarium in- 
cludes only a single ovule, and what the meaning of 
the difference in size between the pollen-grains from 
the corresponding seta of anthers may be, I will not 
pretend to conjecture. 

The clear evidence that the species just described is 
heterostyled and trimorphic is the more valuable as 
there is some doubt with respect to JP. cordata, an in- 
habitant of the United States, Mr. Leggett suspects* 
that it is either dimorphic or trimorphic, for the 
pollen-grains of the longer stnmena are "more than 
twice the diameter or than eight times the mass of 
the grains of the shorter stamens. Though minute, 
I these smaller grains seem as perfect as the larger 
f ones." On the other hand, he says that in all the 
[ mature flowers, " the style was as long at least as 
I the longer stamens ;" " whilst in the young flowers 
L it was intermediate in length between the two sets of 
I stamens ;" and if this be so, the species can hardly be 
|-lLeterostyled. 

• 'BuU, nf the Torrej BolnaLal Club,' 1875, vol. ri. p. €2. 



ILLEGITIMATE OFFSPBING OF 



iLLEGITiaATE OrPBPhUNQ OF HETEROSTTLEn pLAHTB, 

lllegltimnte 'jffapring fromill three forms of Ljthnim aaiooria— Tb* 
dworftJ btiitiirc and atprility, Bome utterly bnrren. some fertile — 
Oialia, traosmLoiiiiD of form (o tlie Icgitimntu and illegitimuta 
Beedlinga^Friniala Siuonsia, iUegitimata offiipriTig in BOme degwe 
dwarfed nod infertile — Equal-iitjled vaiiitlea of P. 8iriem<ia, auri- 
cula, fBrboaa, end elatior — P. vulgariH, red-flowered variety, illegi- 
timate seeiUinga aterile — P. Tens, illegitimate [ilaota raised during 
several HUCoesniTe ^nertitions, tlielr d narfed atatnre and ateriiitj — 
Equal-BtjrleJ Tiirietie* of P. variB— TransmiBsloo of form by FolJ 
mouatia and Polygonum — Concluding remBrkb — Close p 
between illegltiniatu fertUiiiBtion and liybriditsm. 

We have hitherto treated of the fertility of the flowers 
of beterostyled plants, when legitimately and illegiti- 
mately fertilised. The present chapter will be devoted 
to the character of their offspring or seedlings. Those 
raised from legitimately fertilised seeds will be here 
called legitimate seedlings or plants, and those from 
illegitimately fertilised seeds, UlegUimate seedlings or 
•plants. They differ chiefly in their degree of fertility, 
and in theb powers of growth or vigour, I will begin 
with trimorphic plantsj and I must remind the reader 
that each of the three forms can be fertilised in six 
diflferent ways ; bo that all three together can be ferti- 
lised in eighteen different ways. For instance, a 
long-styled form can be fertilised legitimately by the 
longest stanrens of the mid-styled and ahort-atyled 
forms, and illegitimately by its own-form mid-length 
and shortest stamens, also by the mid-length stamens 
of the mid-3tyled and by the shortest stamens of the 
short-styled form ; so that the long-atyled can be ferti-_ 




J 



*p. V. HETEEOSTrLED THllIOEFniO PLANTS. 189 

iiaed legitimately in two ways and illegitimately in 
four ways. The same holds good with respect to the 
mid-styled and short-styled ibrms. Therefore with 
trimorphic species six of the eighteen unions yield 
legitimate offspring, and twelve yield illegitimate 
offspring. 

I will give the results of my experiments in detail, 
partly because the obaervatious are extremely trouble- 
some, and will not probably soon be repeated — thus, I 
was compelled to count under the microscope above 
0,000 seeds of Lr/thrum scUicaria — but chiefly because 
light is thus indirectly thrown on the important suh- 
I ject of hybridism. 



Lythrum balicaria. 

Of the twelve illegitimate uuious two were com- 
', pletely barren, so that no seeds were obtained, and of 
I course no seedlings could be raised. Seedlings were, 
however raised from seven of the ten remaining il- 
legitimate unions. Such illegitimate seedlings when 
in flower were generally allowed to be freely and 
legitimately fertilised, through the agency of bees, by 
other illegitimate plants belonging to the two other 
forms growing close by. This is the fairest plan, and 
was usually followed ; but in several cases (which 
will always be stated) illegitimate plants were ferti- 
lised with pollen taken from legitimate plants be- 
longing to the other two forms ; and this, as might 
have been expected, increased their fertility. Lythrum 
galiearia is much affected in its fertility by the nature 
of the season ; and to avoid error from this source, 
OS far as possible, my observations were continued 
during several years. Some few experiments were 
tried in 1803. The summer of 1864 was too hot and 



190 



ILLEOnTMATE OFFSPKINO OP 



dry, and, though the plants i 



lopiously mtteied^ 



some few apparently suffered in their fertility, whilst 
others were not in the least affected. The years 
1865 and, especially, 1866, were highly favourable. 
Only a few observations were made during 1867. 
The results are arranged in classes according to the 
parentage of the plants. In each case the average 
number of seeds per capsule is given, generally taken 
from ten capsides, which, according to my experience, 
is a nearly sufBciont number. The maximum num- 
ber of seeds in any one capsule is also given ; and 
this is a usefiil point of comparison with the nor- 
mal standard — that is, with the number of seeds 
produced by legitimate plants legitimately ferti- 
lised. I will give likewise in each cose the minimum 
number. When the maximum and minimum differ 
greatly, if no remark is made on the subject, it may 
be understood that the extremes are so closely con- 
nected by intermediate figures that the average is a 
fair one. Large capsules were always selected for 
counting, in order to avoid over-estimating the infer- 
tility of the several illegitimate plants. 

In order to judge of the degree of inferiority in 
fertility of the several illegitimate plants, the follow- 
ing statement of the average and of the maximum 
number of seeds produced by ordinary or legitimate 
plants, when legitimately fertilised, some artificially 
and some naturally, will serve as a standard of com- 
parison, and may in each case be referred to. But I 
give under each experiment the percentage of seeds 
produced by the illegitimate plants, in comparison 
with the standard legitimate number of the same 
form. For instance, ten capsules from the illegitimate 
long-styled plant (No. 10), which was legitimately 
and naturally fertilised by other illegitimate jdant^ , 



I 



fXfcAP.V. HETEBOSTYLED THIMOBPttIC PLANTS. 191 

contained on an averago 44*2 seeds; whereas the 
capaulea on legitimate long-styled plants, legitimately 
and naturally fertilised by other legitimato plants, 
contained on an average 93 seeds. Therefore thia 
illegitimate plant yielded only 47 per cent, of the 
fall and normal complement of seeds. 

Standard Nuinber of Seeds producedhy Legitimate Plants 
of the three Forms, when legitimately feriilised, 

Long^tyled form : average number of seeds in each 
capsule, 93 ; maximum number observed out of twenty- 
three capsules, 159. 

Mid-styled form : average number of seeds, 130 ; 
I maximum number observed out of thirty-one capsules, 
^ 151. 

Short-styled fonn : average number of seeds, S3 ■ 5 ; 
but we may, for the sake of brevity, say 83 ; maximum 
number observed out of twenty-five capsules, 112. 



I Classes I. and IL Illegitimate Plants raised from 

Long-styled Parents fertilised irnth pollen from the 
mid-length or the shortest stamens of other plants of 
the same form. 

From this union I raised at different times three 
lots of illegitimate seedlings, amounting altogether to 
56 plants. I must premise that, from not foreseeing 
the result, 1 did not keep a memorandum whether the 
eight plants of the first lot were the product of the 
mid-length or shortest stamens of the same form ; but 
I have good reason to believe that they were the pro- 
duct of the latter. These eight plants were much more 
dwarfed, and much more sterile than those in the other 
I two lots. The latter were raised from a long-styled 



192 



ILLEQITIMATB OFFSPEINO OF 



Our. T. 



plant growing qnite isolated, and fertilised by the 
agency of bees with its own pollen ; and it ia ^most 
certain, from the relative position of the organs of 
fructification, that the stigma under these circmn- 
stances would receive pollen from the mid-length 
stamens. 

All the fifty-six plants in these three lots proved long- 
styled ; now, if the parent-plants had been legitimately 
fertilised by pollen from the longest stamens of the 
mid-styled and short-styled forma, only about one- 
third of the seedlings would have been long-styled, 
the other two-thirds being mid-styled and short-styled. 
In some other trimorphic and dimorphic genera we 
shall find the same curious iact, namely, that the long- 
styled form, fertilised illegitimately by its own-form 
pollen, produces almost exclusively long-styled seed- 
lings,* 

The eight plants of the first lot were of low stature : 
three which I measured attained, when fuUy grown, the 
heights of only 28, 29, and 47 inches ; whilst legitimate 
plants growing close by were double this height, one 
being 77 inches. They all betrayed in their general 
appearance a weak constitution ; they flowered rather 
later in the season, and at a later age than ordinary 
plants. Some did not flower every year ; and one plant, 
behaving in an unprecedented manner, did not flower 
until three years old. In the two other lots none of 
the plants grew quite to their full and proper height^ 
as could at once be seen by comparing them with the 
adjoining rows of legitimate plants. In several plants 
in all three lots, many of the anthers were either 
shrivelled or contained brown and toiigh, or pulpy 



Ch*p. V. HETEEOBTYLED TEIMOEFHIC PLANaS. 193 

matter, without any good pollen-grains, and they never 
shed their contents ; they were in the stats designated 
by Grartnet • as contaLescent, which term I will for the 
future use. In one flower all the anthers were conta- 
bescent excepting two which appeared to the naked 
eye sound ; but under the microscope about two-thirds 
of the pollen-graina were seen to be small and shrivelled. 
In another plimt, in which all the anthers appeared 
sound, many of the pollen-grains were shrivelled and 
of unequal sizes. I counted the seeds produced by 
seven plants (1 to 7) in the first lot of eiglit plants, 
probably the product of parents fertilised by their 
own-form shortest stamens, and the seeds produced by 
three plants in the other two lots, almost certainly the 
product of parents fertilised by their own-form mid- 
length stamens. 

Flant 1. Tliis long-styled plant was allowed during 1863 to 
be freely and legitimately fertiLised by an adjoining illegitimate 
mid-styled plant, but it did not yield a single seed-capsula It 
waa then rcnioTed and planted in a remote place close to a 
brother long-sfjlod plant No. 2, eo that it must haye been freely 
though illegitiioately fertilised; under these circumstanceB it 
did not yield during 16(il and 1865 a single capsule. I should 
here state that a legitimate or ordinary long-atyled plant, when 
growing isolated, and freely though illegitimately fertilised by 
insects with its own pollen, yielded an immense niLmber of 
capsules, which contained on an average 21 '5 seeds. 

Fl'int 2 This long-styled plant, after flowering during 1863 
close \o an illegitiinate mid-styled plant, produced less than 
twenty capsules, which contained on an average between four 
and five seeds. Wben subsequently growing in company with 
Na 1, by which it will have been illegitimately fertilised, it 
yielded in 1SC6 not a single capsule, but in 1865 it yielded 
twenty-two capsules i the best of tliese, fifteen in niunber, were 
examined; eight contained no seed, and the remaining seven 
contained on an averse only three seeds, and these seeds wore 

• 'BeitrageiurKenntniaB dcr Bi^tinohtung,' 1844, p. 116. 



194 



ILLEGITIMATE 0FF8PBISQ OF Ca»p. T. 



I 



BO smail and shriTQllod that I doubt whether the7 would hare 
germinated. 

Plants 3 and i. These two long-st/Ied planls, after being 
freelj and logitimatel; fortiliRod during IUGS hj the same iile- 
gitiioate mid-etylod plant as in the lost case, were as miserahlj 
alerile as No. 2. 

Plant 5. TliiB long-gtyled plant, after flowering in 1863 flosa 
to an illogitiffliite mid-etyfed plant, yielded only four capsules, 
which altogether included only five seeds. During 186i, 18G5, 
and,lSC6, it was surrounded either by illegitimate or legitimate 
plants of the other two fonos ; but it did not yield a single 
capsule. It waa a superfluouB experiment, but I likewise arti- 
ficially fertillBed in a legitimate manner twelye flowers ; but not 
one of these produced a capsule; so that this plant was almost 
absolutely barren. 

Plant 6. This long-stjled plant, after flowering during the 
farourabls year of lSt36, surrounded by illegitimate plants of 
the other two forma, did not produce a single capsule. 

Plant 7. This long-styled plant was the most fertile of the 
eight plants of the first lot. During ltj6'i it was surroonded by 
illegitimate plants of various parentage, many of which were 
highly fertile, and must thus hove been legitimately fertilised. 
It produced a good many capsules, ten of which yielded an 
average of 313' 1 seeds, with a maximum of i7 and a minimum 
of 22; so that this plant produced 39 per cent, of the fall 
number of seeds. During lb64 it was surrounded by legitimate 
and illegitimate plants of the other two forms; and nine 
capsules (one poor one being rejeefed) yielded an average of 
41 '9 seeds, with a maximum of 56 and a minimum of 28; so 
that, under these favourable circumstances, this plant, the most 
fertde of the first lot, did not yield, when legitimately fertilised, 
qtute i5 per cent, of the full complement of seeds. 

In tLe second lot of plants in the present class, 
descended from the long-styled form, almost certainly 
fertilised with pollen from its oiva mid-length stamens, 
the plants, as already stated, were not nearly so dwarfed 
or so sterile as in the first lot. All produced plenty 
of capsules. I counted the number of seeds in only 
three plants, viz. Nos. 8, 9, and 10, 




ICbap. V. HETEB08TYLED TRIMOKPHIC PLANTS. 



195 



I 



I 



iwi 8. This plant was allowed to lie freely fertilised in IBGi 
by legitimate and illegitimate plants of tlie other two forms, 
and ten capsules yielded on an average 41 ■! seeds, tritk a 
maximum of 73 and a raininium of 11. Hence this plant pro- 
duced only 44 per cent, of the full complement of seeds. 

Fhmt 9. This long-styled plant was allowed in 1865 to be 
freely feitiUsed by illegitimate plants of the other two fonna, 
most of which were moderately fertile. Fifteen capsules yielded 
on an average 57 ' 1 seeds, with, a maximum of 86 and a minimum 
of 23. Hence the plant yielded 61 per cent, of the full comple- 
ment of seeds. 

Flaiit 10 This long-styled plant was frcoly foriilisod at the 
same time and in the same manner as the last. Ten capsules 
yielded an average of 44'2 seeds, with a maximum of GU and a 
minimum of 25; hence this plant yielded 47 per cent, of the 
full complement of seeds. 

The nineteen long-3tyled plants of the third lot, of 
the same parentage aa the last lot, were treated dif- 
ferently ; for they flowered during 1867 by themselvea 
so that they must have been illegitimately fertilised 
by one another. It has already been stated that a 
legitimate long-styled plant, growing by itself and 
yisited by insects, yielded an average of 21 -5 seeds 
per capsule, with a Diasimnm of 35; but, to judge 
feirly of its fertility, it ought to have been observed 
during successive seasons. We may also infer from 
analogy that, if several logittmate long-styled plants 
were to fertilise one another, the average number of 
■eeds would be increased ; but how much increased 
I do not know ; hence I have no perfectly fair standard 
of comparison by which to judge of the fertility of the 
three following plants of the present lot, the seeds of 
vhich I counted. 



flant 11. This long-styled plant produced a large crop of 
npsulee, and in this respect was one of the moat fertile of 
the whole lot of nineteen plants. But the average from ten 



196 



ILLEGITlilATZ OFFSPBDJQ OF 



Cbap. T 



capHiiles was onl; 359 seeds, with a nuuimom of 60 and a 
mfnim 'nn of 8. 

Plant 11 This long-etjied plant produced Terj few capsnlee; 
and tea jielded an average of only 154 seeds, with a maximmn 
of 30 and a minioKUn of 4. 

riunl 13. This plant offers an anomalous case; it flowered 
profiisely, yet produced very few capenlea ; but these con- 
tained nnmerouB seeds. Ten capeulee yielded an avem^ of 
71'9 seeds, with anusiiniun of 95 and a minimnm of 29. Con- 
sidering that this plant was ill^timate and illegitinmtcly fer- 
tilised by its brother long-styled BeedJings, the average and the 
masimiun are so remarkably high that 1 cannot at all under- 
stand the case, We should remember that the aTsrage fiw a 
legitimate plaut legitimately fertilised is 93 seeds. 



Class III. IJlegitimate Plants raised from a Short- 
styled Parent fertilised with pollen from ovm-form 
mid-length stamen. 

I raised from this union nine plants, of which eight 
were short-styled and one long-styled ; so that there 
seems to be a strong tendency in this form to repro- 
duce, when self-fertilised, the parent-form; but the 
tendency is not so strong as with the long-styled. 
These nine plants never attained the full height of 
legitimate plants growing close to them. The anthers 
were contabcscent in many of the flowers on several 
plants. 

Finn! 14. This short-styled plant was allowed daring 18C5 to 
be freely and legitimately fertilised by ill^timate plants de- 
scended from self-fertilised mid-, long- and short-styled plants, 
Piffeen capsules yielded an average of 28'3 seeds, with a 
mazimiun of 51 and a minimum of 11; hence this plant 
produced only 33 per cent, of the proper number of seeds. The 
seeds themselves were small and irregular in shapa Although 
so sterUe on the female side, none of the anthers were conta- 
besoent. 

Plunt 15. This sliorfrstyled plimt, treated like the last duiing 



I 



p. T. HETEKOSTYLED TEOIOEPHIO PLANTS. 107 

the same year, yiolJed an average, from fifteen capsules, of 27 
■eeds, with a maximum of 4'J and a miBimum of 7. But two 
poor capsules may ba rejected, aud then the avcrago rises to 
83-6. with the same masimnm of 49 and a minimum of 20; 80 
that this plant attained 33 per cent, of the normal standard of 
fertility, and was rather more fertile than the last, jct many of 
the anthers wore contabescent. 

F/ajit 16. This ehort-styled plant, treated like the two last, 
yielded from ten capsules an averago of 77'8 seeds, with a 
maiimum of 97 and a minimum of 60; so that this plant 
produced 94 per cent, of the full number of seeds. 

J'l:in( 17. This, the one long-styied plant of the same parents 
age as the lust threo plants, when freely and legitimately ferti- 
lised iu the same manner as the last, yielded an average from 
ten capsules of 76-3 rather poor seeds, with a maxinium of 88 
and a minimum of 57. Hence this plant produced B2 per cent, 
of the proper number of seeds. Twelve flowers enclosed tn a 
net were artificially and legitimately fertilised with pollen from 
a legitimate short-styled ploat; and nine capsules yielded an 
average of 82 ' 5 seeds, with a maximum of 9S and a minimum 
of 51; so that its fertility was increased by the action of 
pollen from a legitimate plant, but still did not reach the normal 
standard. 

Clab3 IV. Illegitimaie Plants raised from a Mid-styled 
Pa/rent fertilised with pollen from ovm-form longest 
stamms. 

After two triala, I succeeded in raising only four 
plants from this illegitimate union. These proved to 
be three mid-styled and one long-styled ; but from so 
small a number we can hardly judge of the tendency 
in mid-styled plants when self-fertilised to reproduce 
the same form. These four plants never attained their 
full and normal height; the long-styled plant had 
Beyeral of its anthers contabescent. 

Plant 18. Tliis mid-styled plant, when freely and legitimately 
fertilised during 1865 by illegitimate plants descended from 
self-fertilised long-, short-, and mid-styled plants, yielded an 
average from ten capsules of 102"G seeds, with a 



I 

I 
I 



198 



aLEGlTIMiTE OFFSPBKG OF 



liil and a luinimiun of 63: henco this plant diJ not prodiii 
quite 80 per cent, of the Dormol nmnlwr of seeds. TweWs 
flowers were artificially and legitimatolf fortllified witU pollen 
from a legitimate long-stylod plant, and yielded firam nina 
capsules an average of 116'1 soeils, wliicli were finer than 
in the pievious cose, with a maiimnin of 135 and a miDimnm 
of 76 ; so that, as with Plant 17, pollen from a legitimate 
plant increased the fertility, but did not bring it up to the full 
standard. 

Plant 19. This mid-styled pinnt. fertilised in the same manner 
and at the sume period as the last, yielded an averse from 
t«n capsules of 734 seeds, with a maiimum of B7 nnd a mini- 
mnm of 64 : hence this plant produced only 56 per cent, of the 
full number of seeds. Thirteen flowers were artificially and 
legitimately fertilised with pollen from a legitimate long-styled 
plant, and yielded ten capsules with an aycrage of 95'(i eeeda; 
80 that the application of pollen from a legitimate plant added, 
oa in the two previous cases, to tlio fertility, but did not bring 
it op to the proper standard. 

Plant 20. This long-styled plant, of the same parentage with 
the two last mid-styled plants, and (roely fertilised in the same 
manner, yielded an average from ten capsules of 69 6 seeds, 
with a umximnm of 83 and a mininiiim of 52 : hence this plant 
produced 75 per cent, of the fiLll number of seeita. 

Class V. Illegiiimaie Plants raised from a SJutrt-sti/hd 
Parent fertilised with pollen from the mid-length 
stainens of the long-styled form. 
In the four previous classes, plants raised from tlie 
three forms fertilised with pollen from either the longer 
or shorter stamens of the same form, hut generally not 
from the same plant, have been described. Six other 
illegitimate unions are possible, namely, between the 
three forms and the stamens in the other two forma 
which do not correspond in height with their pistils. 
But I succeeded in raising plants from only three of 
these six unions. From one of them, forming the pre- 
sent Class v., twelve plants wore raised ; these con- 
sisted of eight short-styled, and four long-styled plants, 




■. V. HKTEEOSTTLED TEIMOEPmC PI^NTS. 19D 

I with not one mid-styled. These twelve plants never 
attained quite their full and proper height, but by no 
means deserved to be (Milled dwarfs. The anthers in 
some of the flowers were contabescent. One plant was 
remarkable from all the longer stamens in every flower 
and from many of the shorter ones having their 
anthers in this condition. The pollen of four other 
plants, in which none of the anthers were contabe- 
scent, was examined ; in one a moderate number of 
grains were minute and shrivelled, but in the other 
three they appeared perfectly sound. With respect tu 
the power of producing seed, five plants (Nos. 21 to 
25) were observed : one yielded scarcely more than 
half the normal number ; a second was slightly infer- 
tile; but the three others actually produced a larger 
average number of seeds, with a higher maximum, 
than the standard. In niy concluding remarks I shall 

■ Ivcur to this fact, which at first appears ine^iplicable. 

Plant 21. This ahort-styled plant, freely and legitimately 
fertilieed during 1865 by iJlegitimato plants, descended from 
Belf-fertilised long-, mid- and ahort-styled parents, yielded an 
average from ten capBules of 43 seeds, with a masimiun of C3 
and a minimum of 26 : hence this plaat, which was the ouo 
with all its longer and many of its shorter stamens contabescent, 
produced only 52 per cent, of the proper number of seeds. 

Pla?U 22. ThiB short-Btyled plant produced perfectly sound 
pollen, as viewed under tJie microscope. During 1866 it was 
freely and legitimately fertilised by other ill^timato plants 
belonging to the present and the following class, both of which 
include many highly fertile plants. Under these circamstancos 
it yielded from eight capsules an average of 100*5 seeds, with 
a maximiuu of 123 and a minimum of 86 ; 8o that it producuu 
121 per cent of seeds in compaiison with the normal standanL 
During 1864 it was allowed to be freely and legitimately ferti- 
lised by legitimate and illegitimate plants, and yielded an 
average, from eight capsules, of 104 '2 seeds, with a maximum 
of 125 and a minimum of UO; consequently it exceeded tba 
normal standanl, producing 125 per cent, of seeds, lu this 



2(* 



II-LEGITIMATB OFP8PKING OF 



Obat. V 



I 



ruM, uH III Homo previons caAos, polloa froni legitimate pl&nts 
adilal in ft atnall degree to tbe fertility of the plant; and tlie 
tortilitjr would, purhaps, imve been Etill greater bad not the 
Bumiuer of ICl lioen vory hot and certainly nnfavoniuble to 
iKMue of the plnnts of Lythnim. 

I'lanl 23. TIiIb ehort-styled plant produced perfectly sonnd 
|N)llun, During I8<)6 it was freely and legitimately fertilised by 
Ills other illogititnute plants apecifled under the hist experi- 
ment, and eight capHulos yielded an average of 113 '5 seeds, 
with a laaiiiuum of 1.3 and a minimum of 93. Henco this 
plant oxcociddU the normal standard, producing no less tlian 136 
por eont, ofwodM. 

i'taiil 2-1. Thia long-styled plant produced pollen which 
teemed under the microscope sound; but some of the grains 
did not dwoll wlion placed in water. During 1864 it waa 
I ogltimatojy fertilised by legitimate and illegitimate plants is 
the Mtiiie inannor as Plant 23, hut yielded an average, from ten 
(uipmileit. of only 55 seeds, with a maximum of 88 and a mini- 
niiini er'J4, thus attaining 69 per cent, of the normal fertility. 
This low degree of fertility, I preaame, was owing to the un- 
fitvoiirablo BOftson ; for during 1866, when legitimately fertilised 
by illegltiiiLato plants in the manner described under No. 22, it 
yieUlod an itvurage, from eight capsulos, of 83 seeds, with a 
maximum of 120 and a minimum of 67, tlius producing 88 per 
conti of the nornial number of seeds. 

I'hinl 'i'). The imllen of this long-stylod plant contnined a 
moderate uumbur of poor and shrivelled grains; and this is a 
surprising eircumstance, as it yielded an extraordinary number 
of seeds. During 1866 it was freely and legitimately fertiliseii 
by illegitimate plants, as described under No. 22, and yielded 
an average, from eight capsules, ofl'JQ- 5 seeds, with a maximum 
of 149 and a minimum of 84. Hence this plant exceeded 
tho normal standard, producing no less than 131 per cent, of 



Class VI. Illegitimate Plants raited from Mid-styled 
Parents ferfilised with pollen from the skoriesl 
Btamens of the long-styled form. 

I raised from this union twenty-five plants, whicb 
proved to bo seventeen long-styled and eight mid- 



I 



p. V. HETEBOBTTLED THIMOHPHIC PLANTS. 201 

' Ityled, but not one short-styled. None of these plaDta 
were in the least dwarfed. I examined, during the 
highly favourable season of 186(ij the pollen of four 
plants : in one mid-atyled plant, some of the anthers of 
the longest stamens were eontabescentj but the pollen- 
grains in the other anthers were mostly sound, as 
they were in all the anthers of the shortest stamens ; 
in two other mid-styled and in one long-styled plant 
many of the poUen-graius' were small and shrivelled ; 
and in the hitter plant as many as a fifth or sixth part 
appeared to be in this state. I counted the seeds in 
five plants (Nos. 26 to 30), of which two were mode- 
itely sterile and three fully fertile. 

FlanC 26. This mid-styled plant was freely and legitimafely 
fertilised, dimng the rather nnfavourttble year 1864, by nuraer- 
ons BnTrounding legitimate and illegitimtit« plants. It yielded 

. average, from t^n capEulea, of 83 '5 seeds, with a maximam 

110 and a minimum of 61, thus attaining 64 per cent, of the 
Bonnal fertility. During the highly faTonrable year 186G, it 
was freely and legitimately fertilised by illegitimate plants 
belonging to the preeent Class and to Class V., and yielded 
an average, from eight capsules, of 86 seeds, with a maximum 
of 109 and a minimum of 61, and thus attained 66 per cent 
of the normal fertility. This was the plant with some of the 
anthers of the longest stamens contabescent ae above mentioned. 

Plant 27. This mid-styM plant, itertilised during 1864 in the 
same manner aa the last, yielded an average, from ten capsules, 
of 99'4 seeds, with a maximum of 122 and a minimum of 511, 
thus attaining to 7C per cent, of the normal fertility. If the 
season had been more fovoimible, its fertility would probably 
have been somewhat greater, bat, judging from the last eipcri- 
nent, only in a slight degree. 

Plant 28. This mid-styled plant, when legitimately fertilised 
during the favourable season of 1866, in the manner described 
nnder No. 26, yielded an average, from eight capsules, of 89 
seeds, with a maximum of 1 19 and a minimtun of 69, thus pro- 
ducing 68 per cent, of the full numlwr of seeds. In the pollen 
of both sets of anthers, nearly as many grains were small and 
shrivelled as sound. 



202 ILLEGITIMATE OFFSPRING OF Chap. V. 

Plant 29. This long-etyled plant waa Intimately fortiliBed 
during the imfaTourable eeasoD of I8&1, in the inaDDOi described 
tinder No. 2(i, and yielded an average, from tea capsulos, o( 
Bl'6seeds, with a mnximum of 132 and n minimum of 47, thus 
attaining to 91 per cent, of the normal fertility. During tha 
highly favourable eeason of 1866, when fertilised in the manner 
described under No. 26, it yielded an aTerage, from nine cap- 
Eules (one poor capsule having been excluded}, of 100 seeds, 
with a masimom of 121 and a mluimum of 77. This plant thus 
exceeded the normal standard, and produced 107 per cent (^ 
seeds. In both sets of anthers there were a good many bad and 
shrivelled pollen-grains, but not eo many as in the last-described 
plant. 

Flant 30. This long-styled plant was legitimately fertilieed 
during 1866 in the manner described under No. 26, and yielded 
an average, from eight capeales, of 94 seeds, with a maximum 
of 106 and a minimum of 66 ; bo that it exceeded the normal 
standard, yielding 101 per cent of seeds. 

Plant 31. Some fiowera on this long-etyled plant were arti- 
ficially and legitimately fertilised by one of its brother illegiti- 
mate mid-Btyled plants ; and five capsules yielded an average of 
90*6 seeds, with a maximum of 97 ond o minimum of 79. 
Hence, as far as can lie judged from so few capsules, this plant 
attained, under these favourable cireumstanceB, 98 per cent of 
the normal standard. 



Class VII. lUegitimaie Plants raised from Mid-stylei 
FaretUs fertilised with pollen from the longest stamenB 
of the short-styled form. 

It was shown in the last chapter that the union from 
which these illegitimate plants were raised is far more 
fertile than any other illegitimate union ; for the mid- 
styled parent, when thus fertilised, yielded an average 
(all very poor capsules being excluded) of 102'8 seeds, 
with a maximum of 130 ; and the seedlings in the 
present class likewise have their fertility not at all 
lessened. Forty plants were raised ; and these attained 
their full height and were covered with seed-capsules 




I Chap. V. HETEROSTYLED TBIMOKrHIC PLANTS. 



203 



I 



I 



Nor did I observe any contabesceut anthers. It de- 
serves, alao, particular notice that these phinta, differ- 
ently from what occurred in any of the previous classes, 
consisted of all three forms, namely, eighteen ahort- 
Btyled, fourteen long-styled, and eight mid-styled 
plants. As these plants were so fertile, I counted the 
seeds only in the two tbUowing cases. 

Plant 32. This mid-Htyled plant was fireely and legitimately 
fertilised during the unfavourable year of 1864, by numerous 
surrounding legitimate and illegitimat* plants. Eigkt cap- 
Bulea yielded an average of 127-2 Geeds. with a maximum of 144 
and a minimum of 96; so that tliiij plant attained 98 j)er cent, 
of tho normal standard. 

Plant 33. Tliia short-styled plant was fertilised in 
manner and at the some time with the last; and ten capsules 
yielded an average of 113-9, with a maximum of 137 and a 
minimum of 90. Bence this plant produced no less than 137 
per cent of seeds in compuisoa with the normal Etondard. 

Oonduding Eemarhs on the Ukgitimate Offspring of ihe 
three forms ofLythrum salicaria. 

From the three forms occurring in approximately 
equal numbers in a state of aatufe, and from the re- 
sults of sowing seed naturally produced, there is reason 
to believe that each form, when legitimately fertilised, 
reproduces all three forms in about equal numbers. 
Now, we have seen (and the fact is a very singular 
one) that the fifty-six plants produced from the 
long-styled form, illegitimately fertilised with pollen 
from the same form (Class I. and II.), were all long- 
styled. The short-atyled form, when self-fertilised 
(Class III.), produced eight short-styled and one long- 
styled plant; and the mid-styled form, similarly treated 
(Class IV,), produced three mid-styled and one long- 
■tyled offspring ; so that these two forms, when ille- 




204 



ILLEGITIMAXB OFFSPBDJG OF 



gitimately fertilised with pollen from the same form, 
evince a strong, but not exclusive, tendency to repro- 
duce the parent-form, AVIien the short-stj led form 
was illegitimately fertiliseil by the long-styled form 
(Class v.), and again when the mid-styled was illegiti- 
mately fertilised hy the long-styled (Class VI.), in 
each case the two parent-forms alone were reproduced. 
Aa thirty-seven plants were raised from these two 
uniona, we may, with much confidence, believe that it 
is the rule that jtlants thus derived usually consist of 
both parent-forms, but not of the third form. When, 
however, the mid-styled form was illegitimately fer- 
tilised by the longest stamens of the short-styled 
(Class VII.), the same rule did not hold good ; for the 
eeedlinga consisted of all three forms. The illegiti- 
mate union from which these latter seedlings were 
raised is, as previously stated, singularly fertile, and 
the seedlings themselves exhibited no signs of sterility 
and grew to their full height. From the consideration 
of these several facts, and from analogous ones to be 
given under Oxalis, it seems prohahle that in a state 
of nature the pistil of each form usually receives, 
through the agency of insects, jwllen from the stamens 
of corresponding height from both the other forms. 
But the case last giveij shows that the application of 
two kinds of pollen is not indispensable for the pro- 
duction of all three forms. Hildehrand has suggested 
that the cause of all three forms being regularly and 
naturally reproduced, may be that some of the flowers 
lire fertilised with one kind of pollen, and others 
on the same plant with the other kind of pollen. 
Pinally, of the three forms, the long-styled evinoea 
somewhat the strongest tendency to reappear amongst 
the offspring, whether both, or one, or neither of the 
parents are long-atyled. 




} ClIAT 



V. HETEROSTYLED TRDIOnpmC PLANTS. 



205 



Tablb 30. 

' Tal.mlaled resulte of the fertility of the forgoing ill^'timata 

plants, when legitimately fertilised, generally hy illegitimate 

plants, as desci-ibed ondor each experimeat Plants 11, 12 

and 13 are escladed, as they were illegitimately fertilised. 

Hornud Standard i/ Fertitity af the three forms, loftcn leifHimatt'j/ 

and juUurally fertilised. 



Form. 


"'SS 


Ni.niLertQ 




Lnng-stjleJ . . . . 
Uid-Etfled .... 
Short-st/led . . . 


'L 


;:: 


No lecord was bf^t, ni 
all Tery pc.„r cap.ala 
were reje,:t«L 



ILAU I, and U.— Illegitimate Plants raised frtmt long styled 
Parents fertilistd vnth poll n from own-form mid-ltrngih w 
lAorlist stametis. 







1 




A..r.g.s.n,. 












KumberDrn^L 












X^r 


S'n.=. 


CMp.ulf, 


UjfpTroiiU.gB 














-Pllttt I . . 


Long-Styled 











g 


































:; 6 






:; 


Oorl 

361 

57-1 


73 
86 


23 
11 
23 


Oorl 


.. 10 








■w-a 


ee 


25 


47 



I 



Clabs ITL—lllegitimafe Phi 


,Uti 


iW/r.4i 


Short-slylid Purentt 


ftrtilUedwUh pollen f 


mo 


vn-furm 


hortesi slamrn: 


t\<a.i\i . , 


Short-rtyW 


2S-I1 




51 




„ 


33 






















77-; 




97 




BO 


in 


,. " . . 


LnDE-itflcl 


7iia 




88 




57 


B3 



20C ILLEGITIMATB OFFSPBING OF Chap. V 

Table 30— eonii'nuoii. 

Class TV. — lUegitvnate Plants raised from. Mid-styled Parenti 

fertilised with pollen from own-fctrm longest stamens. 



























Numbof 


crruDi. 


Form. 
















C-iU.. 


CMMle. jotUwN«.L»l 


E'liint 


B 


WiJ^tyleJ. 


ia2'6 


131 


63 


80 


,. 


y . . 




73'4 


87 


fl* 


66 




u . . 


Long-btyled 


SB'fi 


83 


53 


75 



Clabs V. — Itlr-i/itimate Plants raisi-d from Short-sly/I'd Pitrenii 
fertilised with pollen from the mid-lemjlh stameiis of tkt lonrj- 
stytedform. 



Pl« 


t2I . . 


ShDit-»t]-]ed 


43-0 


63 


26 


53 








100-5 


123 


8U 


lai 




23 . . 




113-5 


123 


P3 


13fi 


" 


23 \ '. 


Long-stjlol 


82-0 
123-5 


120 
149 


67 
84 


131 



Clabs VT. — Illegitimate Pliinia raised from Mid'Siyled Farxitt 
fertilised with pollen from the shortest stiimens of the long- 
elyledform. 



PI 


ntaa . . 


MiJ-Btyloa. 


86-0 


109 


61 


6S 




, 27 . . 

, 28 , . 


" 


99-4 
89-0 


122 
119 


53 
69 


70 
68 






Uag-»iyled 


100-0 


121 




107 














101 




, 31 . . 




so-s 


87 


79 


SB 



!f.A8B Vil. — lllegilimale Plants raised from Mid-styled Fareati 
fertilised viith pollen from the lonyest stamens of (A« ihort- 
Hyledform. 



I 



lOHiP.V. HETEBOBTYLED TRIUORPHIU PLANTS. 207 

lessened fertility of most of these illegitimate 
plants is in many respects a highly remarkable phe- 
nomenon. Thirty-three plants in the seven classes 
were subjected to varions trials, and the seeds care- 
fully counted. Some of them were artificially ferti- 
lised, but the far greater number were freely fertilised 
(and this is the better and natural plan) through the 
agency of insects, by other illegitimate plants. In the 
right-hand, or percentage column, in the preceding 
table, a wide difference in fertility between the plants 
in the first four and the last three classes may be per- 
ceived. In the first four classes the plants are de- 
scended from the three forma illegitimately fertilised 
with pcUen taken from the same form, but only 
rarely from the same plant. It is necessary to observe 
this latter circumstance; for, as I have elsewhere 
abown," most plants, when fertilised with their own 
pollen, or that from the same plant, are in some 
degree sterile, and the seedlings raised from such 
unions are likewise in some degree sterile, dwarfed, 
and feeble. None of the nineteen illegitimate plants 
in the first four classes were completely fertile ; one, 
however, waa nearly so, yielding £f6 per cent, of the 
proper number of seeds. From this high degree of 
fertility we have many descending gradations, till we 
reach an absolute zero, when the plants, though bear- 
ing many flowers, did not produce, during successive 
years, a single seed or even seed-capsule. Some of the 
most sterile plants did not even yield a single seed 
when legitimately fertilised with pollen from legiti- 
mate plants. There is good reason to believe that the 
first seven plants in Class I. and II. were the offspring 



208 ILLEGITIMATE OFFSPBING OF Chap. V, 

of a long-styled plant fertilised with pollen from ifa 
own-form shortest stamens, and these plants were the 
most sterile of all. The remaining plants in Class I. 
and II, were almost certainly the product of pollen 
from the mid-length stamens, and although very ste- 
rile, they were less so than the first set. None of the 
plants in the first four classes attained their full and 
proper stature; the first seven, which were the most 
sterile of all (as already stated), were by far the most 
dwarfed, several of them never reaching to half their 
proper height. These same plants did not flower at so , 
early an age, or at so early a period in the season, aa 
they ought to have done. The anthers in many of i 
their flowers, and in the flowers of some other plants I 
in the first six classes, were either contabescent or in- 
cluded numerous small and shrivelled pollen-grains, I 
Aa the suspicion at one time occurred to me that the I 
lessened fertility of the illegitimate plants might be 1 
due to the poUea alone having been affected, I may I 
remark that this certainly was not the case ; for several j 
of them, when fertilised by sound pollen from legiti- 1 
mate plants, did not yield the full complement of I 
seeds ; henee it is oei-tain that both the female and 1 
male reproductive organs were affected. In each of I 
the seven classes, the plants, though descended from | 
the same parents, sown at the same time and in the 1 
same soil, differed much in their average degree of ] 
fertility. 

Turning now to the fifth, sixth, and seventh class<!S, 
and looking to the right-hand column of the table, wo 
find nearly us many plants with a percentage of 8ee(^ 
above the normal standard as beneath it. Aa with 
most plants the number of seeds produced varies much, J 
it might be thought that the present case was one j 
merely of variability. But this view must be rejected, I 



I 



f Chap. V. HET-EBOSTYLED TBIMOBPHIC PLANTS. 209 

as far as the leas fertile plants in these three classes 
Hre concerned : first, because none of the plants in 
Class V. attained their proper height, which shows 
that they were in some manner affected; and, secondly, 
because many of the plants in Classes V. and VI. pro- 
duced anthers which were either contabescent or in- 
cluded small and shrivelled pollen-grains. And as in 
these cases the male organs were manifestly deterio- 
rated, it is by far the most probable conclusion that 
the female organs were in some cases likewise affected, 
and that this was the cause of the reduced number of 
Beeds. 

With respect to the six plants in these three classes 
which yielded a very high percentage of seeds, the 
thought naturally arises that the normal standard of 
fertility tor the long-styled and short-styled forms 
(with which alone we are here concerned) may have 
been fixed too low, and that the six illegitimate plants 
are merely fully fertile. The standard for the long- 
Btyled form was deduced by counting the seeds in 
twenty-three capsules, and for the short-styled form 
from twenty-five capsules. I do not pretend that this 
ia a sufficient number of capsules for absolute accu- 
racy ; hut my experience has led me to believe that a 
very fair result may thus he gained. As, however, the 
maximum number observed in the twenty-five capsules 
of the short-styled form was low, the standard in this 
case may possibly be not quite high enough. But it 
should be observed, in the case of the illegitimate 
plants, that in order to avoid over-estimating their in- 
fertility, ten very fine capsules were always selected ; 
aud the years 1865 and 18fi6, during which the plants 
in the three latter classes were experimented on, were 
highly favourable for seed-production. Now, if this 



210 



II.LEOITISIATE OFFSPKETO OF 



CMtr. T. 



plan of tfiloritiof; very fine capmiles during &TCMuablB 
maunnm liif] IfKni followed for obtaining tiie i 
atiin'Iur'lii, iintUnul of taking, during Taiioos t 
tlin llirit cupNiiloN which cumc to band, the stuidaiili 
Would iiiidoiilitodly huve been considerably higber; 
ftud tliiiM tlio fa<;t of tlio six foregoing plants iq>peaiii^ 
to yiold nil iitiiiiUiirully liigh percentage of seeds may, 
jMirliuiM, Iw oxpluinod. Oil this view, these plants are, 
in fnot, niBroly fully furtile, and not fertile to an ab- 
n')nnnl dogroo. NovorthelcBS, as characters of all 
kinds are liable to variation, especially with organisms 
unimtnrully trcatfld, anil as iu the four first and more 
■t^irilu cliuwcii, tlio plants derived from the same pa- 
ruuta and treated in the same manner, certainly did 
vary niiioli in sterility, it is possible that certain plants 
ill tliu lattor und more fertile closes may have varied 
NU IU to have atiquinsd an abnormal degree of fertility. 
iJiit it Mhoiilil be noticed that, if my standarda err in 
U^iig too luw, the sterility of all the many sterile 
plaiits in tho several classes will have to be estimated 
by 10 much tho higher. Finally, we see that the ille- 
gitimate ))luiit« iu the four first classes are all more or 
loss sterile, some being absolutely barren, with one 
ulono almost completely fertile ; in the tiiree latter 
(^luMHOK, Home of tho plants are moderately sterile, 
wliilst others are fully fertile, or possibly fertile in 
excess. 

The laat point which need here be noticed is that, 
as far iia the means of comimrison serve, some degree 
of relationship generally exists between the infertility 
of the illegitimate union of the several parent-forms 
and that of their illegitimate offspring. Thus the 
two illegitimate unions, from which the plants in 
Classes VI. and VII. were derived, yielded a fail 
amount of seed, and only a few of these plants are in 



I 



Chap. V. HETEROSTYLED TRIMOEPHIC PLANTS. 211 

auy degree sterile. On the other hand, the illegiti- 
mate unions between plants of the same form always 
yield very few seeds, and their seedlings are very 
sterile. Long -styled parent-plants when fertilised 
with pollen frtnn their own-form shortest stamens, ap- 
pear to be rather more sterile than when fertilised with 
their own-form mid-length stamens ; and the seedlings 
from the former union were much more sterile than 
those from the latter union. In opposition to this re- 
lationship, short^styled plants illegitimately fertilised 
with pollen from the mid-length stamens of the long- 
styled form (Class V.) are very sterile ; whereas some 
of the offspring raised from this union were far from 
being highly sterile. It may be added that there is a 
tolerably close parallelism in all the classes between 
the degree of sterility of the plants and their dwarfed 
stature. As previously stated, an illegitimate plant 
fertilised with pollen from a legitimate plant has its 
fertility slightly increased. The importance of the 
several foregoing conclusions will be apparent at the 
close of this chapter, when the illegitimate unions be- 
tween the forms of the same species and their illegiti- 
mate offspring, are compared with the hybrid unions 
of distinct species and their hybrid offspring. 

OxALia. 

No one has compared the legitimate and illegiti- 
mate offspring of any trimorphic species in this genus. 
Hildebrand sowed illegitimately fertilised seeds of 
Oxalis Vcddiviana' but they did not germinate ; and 
this fact, as he remarks, supports my view that an 
illegitimate union resembles a hybrid one between 



'Bo[. Zoitutig.' 1871, p. 1 



212 ILLEGITIIIATE OFFSPEINa OP CHii 

twn distiuct speciea, for the seeds in this latter c 

are often incapable of germination. 

The follawing obserrations relate \o the Qatnre of the forou 
which appear among the Intimate seedlings of Oxula Valdiviatia. 
Hildebraiid raised, as described in the paper just referred to, 
211 seedlingx from all six Intimate unions, and the three forms 
appeared among the ofispring from each union. For instance, 
long-styled plants were legitimately fertilised with jrallen from 
the longest stamens of the mid-styled form, and the seedlings 
consisted of 15 long-styled, 18 mid-styled, and 6 short-styled. 
We here see that a few short-styled plants were produced, though 
neither parent was short-styled; and so it was with the other 
legitimate unions. Out of the above 211 seedlings, 173 belonged 
to the same two forma as their parents, and only 38 belonged 
to the third form distinct from either parent. In the case of 
0. BeiinelH, the result, as observed by flildebrand, was nearly 
the same, but mure striking : all the offspring from four of the 
logitimato unions consisted of the two parent-forms, whilst 
amongst the seedlings from the other two legitimate unions the 
third form appeared. Thus, of the 43 seedlings from the six 
legitimate unions, 35 belong;od to the same two forms as their 
parents, and only 8 to the third form. Fritz Miiller also raised 
in Brazil seedUngs from long-styled plants of 0. BegnelU legiti- 
mately fertilised with pollen from the longest stamens of the 
mid-styled form, and all these belonged to the two parent- 
forms.' Lastly, seedlings were raised by me from long-styled 
plants of 0. spedosa legitimately fertiUsed by the short^styled 
form, and from the latter reciprocally fertilised by the loi^ 
styled; and these consisted of 33 long-styled and 26 shoitr 
styled plants, with not one mid-styled form. There can, thrae- 
fore, be no doubt that the legitimate offspring from any two 
forms of Osalis tend to belong to the same two forms Bs their 
parents ; but that a few seedlings belonging to the third form 
occasionally make their appearance ; and this latter fiu^t, as 
Hildebrand remarks, may be attributed to atavism, as some of 
their progenitors will almost certainly have belonged to tha 
third form, 

^Vhen, however, any one form of Oxalia is fertiliaed illtBitf" 1 



' ■ JciiBlsohe ZBilaohrift.' &a. Ilund vl 1871, p. 73. 



t 



} tlHAP. V. HETEHOSTTLED DIMORPHIC PLANTS. 213 

matelf with pollen from the same form, the seedlings appear to 
belong inTariablj to this form. Thus Hildebrand states" that 
long-Htyled plants of 0. tosea growing by themselves have been 
propagated in Gennany year after year by seed, and have always 
prodaeed long-styled phrnts. Again, 17 seedlings vpere raised 
from mid-styled plants of u. htdi/saroides growing by themselves, 
and these were all mid-styled. So that the forms of Ozalie, 
when iliegitimately fertilised wth their own pollen, behave like 
the long-styled form of Lythmm ealicariii, which when thus fer- 
tilised always produocd with me loog-styled afikpring. 



PrIMDLA SlNENSia. 

I raised during I"ebruary 1862, from some long- 
styled plants illegitimately fertiliaud with pollen from 
the same form, twenty-seven seedlings. These were 
all long-styled. They pruved fully fertile or even 
fertile in excess; for ten flowers, fertilised with pollen 
from other plants of the same lot, yielded nine c-op- 
sulea, containing on an average 39-7d seeds, with a 
maximum in one capsule of 66 seeds. Four other 
flowers legitimately crossed with pollen from a legiti- 
mate plant, and four flowers on the latter crossed with 
pollen from the illegitimate seedlings, yielded seven 
capsules with an average of 53 seeds, with a maximum 
of 72. I must here state that 1 have found some 
difficulty in estimating the normal standard of fer- 
tility for the several unions of this species, as the 
results difl'cr much during successive ye^irs, anil 
the seeds vary so greatly in size that it is hard to 



214 



ILLEGITIMATE 0FF8PBING OF 



decide which ought to be considered good. In order 
to avoid over-estimating the infertility of the several 
illegitimate unions, I have taken the normal standard 
as low as possible. 

From the foregoing twenty-seven illegitimate plants, 
fertilised with their own-form pollen, twenty-five seed- 
ling grandchildrea were raised ; and these were all 
long-styled; so that from the two illegitimate gene- 
rations fifty-two plants were raised, and all without 
exception proved long-styled. These grandchildren 
grew vigorously, and soon exceeded in height two 
other lota of illegitimate seedlings of different parent- 
age and one lot of equal-styled seedlings presently to 
be described. Hence I expected that they would have 
turned out highly ornamental plants ; but when they 
flowered, they seemed, as my gardener remarked, to 
have gone back to the wild state ; for the petals were 
pale-coloured, narrow, sometimes not touching each 
other, flat, generally deeply notched in the middle. 
but not flexuous on the margin, and with the yellow 
eye or centre conspicuous. Altogether these flowera 
were strikingly different from those of their pro- 
genitors; and this, I think, can only be acconnted 
for on the principle of reversion. Most of the anthers 
on one plant were contabescent. Seventeen flowera 
on the grandchildren were illegitimately fertilised 
with pollen taken from other seedlings of the same 
lot, and produced fourteen capsules, containing on an 
average 29 '2 seeds; but they ought to have con- 
tained about 35 seeds. Fifteen flowers legitimately 
fertilised with pollen from an illegitimate short-styled 
plant (belonging to the lot next to be described) pro- 
duced fourteen capsules, containing an average of 4G 
seeds ; they ought to have contained at least 50 seeds. 
Hence these grandchiMren of illegitiimite descent ap> 



descent Bp> ^^H 



CUAP. V. DETEROSTVLED DIMORPHIC PLANTS. 



215 



pear to have lost, though only ia a very slight degree, 
their ftill fertility. 

We will now turn to the short-styled form : from a 
plant of this kind, fertilised with its own-form pollen, 
I raised, during February 1862, eight seedlings, sevea 
of which were short-styled and one long-styled. They 
grew slowly, and never attained to the full stature of 
ordinary plants ; some of them flowered precociously, 
and others late in the season. Pour flowers on these 
9hort-styled seedlings and four on the one long-styled 
seedling were illegitimately fertilised with their own- 
form pollen and produced only three capsules, con- 
taining on an average 23 '6 seeds, with a maximum 
of 29 ; but we cannot judge of their fertility from so 
few capsules ; and I have greater doubts about the 
normal standard for this union than about any other ; 
but I believe that rather above 25 seeds would be a 
fair estimate. Eight flowers on these same short-styled 
plants, and the one long-styled illegitimate plant 
were reciprocally and legitimately crossed ; they pro- 
duced five capsules, which contained an average of 
28 '6 seeds, with a maximum of 36. A reciprocal 
cross between legitimate plants of the two forms 
would have yielded an average of at least 57 seeds, 
with a possible maximum of 74 seeds ; so that these 
illegitimate plants were sterile when legitimately 
crossed. 

I succeeded in raising from the above seven short- 
styled illegitimate plants, fertilised with their own- 
form pollen, only six plants — grandchildren of the 
first union. These, like their parents, were of low 
stature, and had so poor a constitution that four died 
before flowering. With ordinary plants it has been 
a rare event with me t« have more than a single plant 
iie out of a large lot. The two grandchildren which 



210 



ILLEGITIMATE OFFSPRING OF 



liveJ and flowered were' short-styled; and twelve of 
their flowera wore fertilised with their own-form pollen 
and produced twelve capsules containing an average 
of 28 2 seeds ; so that these two plants, though be- 
longing to BO weakly a set, were rather more fertile 
than their parents, and perhaps not in any degree 
sterile. Four flowers on the same two grandchildren 
were legitimately fertilised by a long-styled illegiti- 
mate plant, and produced four capsules, containing 
only 32-2 seeds instead of about 64 ueeds, which is 
the normal average for legitimate short^styled plaata 
legitimately crossed. 

By looking back, it will be seen that I raised at 
first fi'om a short-styled plant fertilised with its own- 
form pollen one long-styled and seven ahort-styled 
illegitimate seedlings. These seedlings were legiti- 
mately intercrossed, and from their seed fifteen plants 
were raised, grandchildren of the first illegitimate 
union, and to my surprise all proved short-styled. 
Twelve short-styled flowera borne by these grand- 
chihlren were illegitimately fertilised with pollen 
taken from other plants of the same lot, and produced 
eight capsules which contained an average of 21 -8 
seeds, with a maximimi of 35. These figures are 
rather below the normal standard for such a union. 
Six flowers were also legitimately fertilised with pollen 
from an illegitimate long-styled plant and produced 
only three capsules, containing on an average 23-6 
seeds, with a maximum of 35, Such a union in the 
case of a legitimate plant ought to have yielded an 
average of 64 seeds, with a possible maximum of 73 
seeds. 

Summary on the Transmission, of Farm, Oonaiitution. 
and Fertility of the Illegitimate Offspring of Primvia 
Sinensis, — In regard to the long^styled plants, their 



!■. V, HETEKOSTyLED DIMOKPHIC PLANTS. 



217 



illegitimate offspring, of which fifty-two were raised in 
tho course of two generations, were all long-styled." 
Tliese plants grew vigorously; hut the flowers in one 
instance were small, appearing as if they had reverted 
to the wild state. In the first illegitimate generation 
they were perfectly fertile, and in the second their 
fertility was only very slightly impaired. With 
Tespect to the short-styled plants, twenty-four out of 
twenty-five of their illegitimatB offspring were short- 
styled. They were dwai-fed in statui'e, and one lot of 
grandchildren had so poor a constitution that four out 
of six plants perished before flowering. The two sur- 
vivors, when illegitimately fertilised with their owu- 
form pollen, were rather less fertile than thoy ought 
to have heen ; but their loss of fertility was clearly 
shown in a special and unexpected manner, namely, 
when legitimately fertilised by other illegitimate 
plants : thus altogether eighteen flowers were fertilised 
in this manner, and yielded twelve capsules, which 
included on an average only 28*5 seeds, with a 
maximum of 45. Now a legitimate short-styled plant 
would have yielded, when legitimately fertilised, an 
average of 64 seeds, with a possible masimnm of 74. 
This particular kind of infertility will perhaps be best 
appreciated by a simile : we may assume that with 
mankind six children would be born on an average frora 
an ordinary marriage ; but that only three would be 
bom from an incestuous marriage. According to the 
L*nalogy of Primula Sinensis, the children of such 



" Dr. Hildebrand, who Drel sliort-styled. From a flltorf-slylB.! 

eallLtl allention tu thU subject plant itiegitinutuljrc'riiliiied 

(• BoL Zeitung ■ 18ii4, p. .5), niavi ita own uolion !"■ "i"™! f""' 

fhim a ilmitw UJegitiiDiite uqidd p)Hats,ofwhio)i 

aeveiilct'D planta, of whiuli fuur- Bt)liL-d u.id llinx' 
leeii were ioiigctjlcj uiiJ lliitjo 



iJiuD he raised Cuarteea 



218 



ILLEGITIMATE OFJSPBINQ OF 



incestuous marriages, if they continued to manr i 
cestuouwy, would have tlieir sterility only slightly 
increased ; but their fertility would not be restored by 
a proper marriage; for if two children, both of in* 
cestuous origin, but in no degree related to each 
other, were to marry, the marriage would of course bo 
strictly legitiiuate, nevertheless they would oot give 
birth to more than half the full and proper number 
of children. 



Equal-itgleii variety o/Fi imula SinejisU. — As any Tarifttion in 
the etractureof the reproductiTeoi^nB, combined with changed 
fuDction, is a rare eveut, the following cases are worth giving 
in detail. My attcatiou was first called to the subject by ob- 
serving, in lUG'i, a long-et;led plant, descended frmn a self- 
fertiliEed long-atyled parent, which bad Bome of its flowei's in an 
anomalous state, namely, with the stamens placed low down in 
the corolla as in the ordinary long-styled form, but with the 
pistils so short that the stigmas Ktood on a level with the anthers. 
These stigmas were nearly as globular and as smooth as in the 
shoit-styled form, instead of being elongated and rough as in 
the long styled form. Here, then, we have combined in the 
same flower, the short stamens of the long-styled form with a 
pistil closely resembling that of the short-stylod form. But 
the atruoture varied much even on the same mnbel ; for in two 
flowers the pistil was intermediate in length between that of 
the long and that of the short-styled form, with the stigma 
elongated as in the former, and smooth as in the latter; and in 
three other flowers the stmeture was in all respects lite that of 
the long-styled form. These modifications appeared to me so 
remarkable that I fertilised eight of the flowers with their own 
poUen, and obtained five oapsniee, which contained on an aver- 
age 43 seeds; and this number shows that the flowers had 
become abnormally fertile in comparison with those of ordinary 
)ong-«tyled plants when self-fertilised. I was thus led to ex- 
amine the plants in several small collections, and the result 
showed that the equal-styled variety was not rare. 

In a state of nature the long and short-styled forms would no 
doubt occiu" in nearly equal nombera, els I infer from the analogy 
of the other hettroKfyted ^jiccicsof Primula, and from Imvia" 



f Obap. V. HETEKOSTYLED DIMORFUIC PLANTS. 

Table 3L 
Piimula Siiensii, 



.„..,o.„.,r,„ 


Lgnamflcd 


ShgrMtJled 


^°:f,ig',"' 


Mr. HorwooJ 








17 


Mr. Dock 









fiastoD 




ta 


15 


Chichester 




9 


3 


Holwood 




12 





fligh Kims 










We=lerhiim 




5 







1:1 


7 





ToUl 


131 


61 


43 



I 
I 



raised tho Itto forme of the present Bpocies in oxacUy the Bame 
number from flowers wiuch had been k;iitimulely crossed. Tho 
preponderance in the above table of the long-styled form over 
the short^styled (in the proportion of 134 to 51) results from gar- 
deners generally collecting seed froia self-fertilised flowers ; and 
the long-atyled flowers produce spontaneously much more seeii 
(as shown in the first chapter) than the short-styled, owing to the 
anthers of the long-styled form being placed low down in the 
corolla, so that, when the flowers fall off, the anthers are dragged 
over the stigma; and we now also know that long-styled plants, 
when self-fertiUsed, very generally reproduce long-styled off- 
Bpnng. From the consideration of this table, it occurred to 
me in the year 1862, that almost all the plants of the Chinese 
primrose cultivated in England would sooner or later become 
long-styled or equal-styled; and now, at the close of 1876, 1 
have had 6ve small collections of plants examined, and almost 
tH consisted of long-styled, with some more or less well-cha- 
lacterised equal-styled phtnte, but with not one ahort-styled. 

With refpect to the equal-styled plants in the table, Mr. Hor- 
wood raised from purchased seeds four plants, which he re- 
membered wore certainly not long-styled, but either short or 
equal-Btyled, probably the latter. These four plants were kept 
ieparate and allowed to fertjlise themselves; from their seed the 
Boveuteen plania in the table were raised, all of which proved 
eqnal-etyled. The stamens stood low down in the corolla as in 
the long-atyled form; an^t the stigmas, wliich were globular and 



220 



ILLEGITIMATE OFFSPRIKG OP Chap. T, 



smooth, were cither completely surrounded by the anthers, or 
stood close above them. M; son William made drawings for 
mo, by the aid of tlie cftmera, of the pollen of one of the aboTB 
equal-Btyled plants ; and, in accordance with tliD position of the 
stamens, the grains resembled in their small size those of the 
loug-styled form. Ho also exaznined pollen from two equal-stylel 
plants at Gouthampton ; and in both of them the grains dif- 
fered extremely in size in the same anthers, a large nnmbor 
being small and shrirelled, whilst many were fully as large as 
those of the ahort-styled form and rather more globular. It is 
probable that the large size of these grains was due, not to their 
having asBumed the character of the short-styled form, but to 
monstrosity; for Mai Wiehura has ohsetred pollen-graina of 
monstrous size in certain hybrids. The vast number of the 
small shrivelled grains in the above two cases explains the fact 
tliat, though equal-atjled plants ore generally fertile in a high 
degree, yet some of them yield few seeds. I may add tljot my 
son compared, in 1875, the grains from two white-fiowered 
plants, in both of which the pistil projected above the anthers, 
but neither were properly long-styled or equal-styled; and in 
the one in which the stigma projected most, the groins were 
in diameter to those in the other plant, in which the stigma pro- 
jected lesB, as 100 to 88; whereas tlie differenM between the 
grains from perfectly oharaeterised long-styled and short-styled 
plants is as 100 to 67. So that these two plants were in an 
intermediate condition. To return to the 17 plants in the first 
line of Table 31 : from the relative position of their stigmas and 
anthers, they could hardly fail to fertilise themselves; and ac- 
cordingly four of them spontaneously yielded no less than IBO 
capsules ; of these Mr. Horwood selected eight tine capsules for 
Bowing; and they included on an average &1'S seeds, with a 
maximum of 72. He gave me thirty other capsules, takeu 
by hazard, of which twenty-seven contained good seeds, aver- 
aging 35-5, with a masJTOiim of 70; but if six poor cap- 
sules, each with less than 13 seeds, be excluded, the average 
rises to 42-5. These are higher nimabers than could be ex-' 
pected from either well-characterised form if self-fertilised ; and 
tliis high degree of fertility accords with the view that the 
male organs belonged to one form, and the female organs par- 
tially to the other form; so that a self-union in die case of the 
e<iiial-6tyled variety is in fact a legitimate union. 
The seed saved from the above seventeen self- fertilised equot 



Chap. V. HETEEOSTYLED DIMOHPHIC PLANTS. 



221 



Btyled plants prodnced Biiteen plants, whicli all proved equal- 
styled, and resembled their pBrents in all the aboTe-s]vecitied 
respects. The stamens, however, in one plant were seated higher 
lip the tube of the corolla than ia the true long-styled form ; 
in another plant almost all the anthers were contahescent These 
sisteon plants were the grandchildren of the four original plants, 
winch it is helieved were eqnal-styled ; bo that tliis abnormal 
condition was faithfully transmitted, prohahly through three, 
and certainly through two generations. The fertility of one of 
these grandchildren was carefully oliserved ; six flowers were 
fertilised with pollen from the same flower, and produced six 
capsules, containing on aa average 68 seeds, with a maxiniuni 
of ij2, and a minimum of 40. Thirteen capsules spontaneously 
self'fertilised yielded an average of 53 ■ 2 seods, with the astonisli- 
ing maiimum in one of 97 seeds. In no legitimate union has 
so high an average as 68 seeds been ohserved by me, or nearly 
so high a maiimum as S2 and 97. Tbese plants, therefore, not 
only have lost their proper heterostyled structure and peculiar 
functional powers, hut have acquired an abnormal grade of fer- 
tihty — ^unless, indeed, their high fertility may be accounted for 
by the stigmas receiving pollen Ironi the circumjacent anthers 
at exactly the most fiivourable period. 

With respect to Mr. Duck's lot in Table 31, seed was saved 
from a single plant, of whieii the form was not oliserved, 
and this produced nine equal-styled and twenty long-styled 
plants. The equal-styled resembled in all respects those pre- 
viously describeil ; and eight of their capsules spontaneously 
Belf-fertiUsed contained on an average 44-4 seeds, with a 
maximum of 61 and a minimum of 23. In regard to the 
twenty long-styled plants, tlie pistil in some of the flowers did 
not project quite so high as in ordinary long-styled flowers; 
and the stigmas, though properly elongated, were smooth; so 
that we have here a slight approach in structure to the pistil of 
the shorl^styled form. Some of these long-styled plants also 
^ approached the eqnal-styled in function ; for one of them pro- 
duced no less than fifteen upontaneously relf-fertilised capsules, 
and of these eight contained, on an average, 31 7 seeds, with 
a maximam of 61. This average would be rather low for a 
long-styled plant artiflciallj fertiUsed with its ovm pollen, but 
is high for one spontaneously self-fertilised. For instance, 
thirty:foiir capsules produced by the illegitimate grandctiildron 
long-styled plant, spontaneously self-fertilised, containwt 



ILLEGITLttATE OFFSPBING OF 



Chat. 1 



on an average on); O'l seeds, irith & nuuiiiinin of 46, So 
seeds indiacjiminately saved from the foregoing twenty-miie 
eqiial-Btyled and long-atjled plants produced aiteen BeedlingR, 
}^ndchi1drea of the origiiuil plant belonging to Mr. Dock ; anil 
these consisted of fourteen equal-Ht;1ed and two long-st;led 
plants ; and I mention this fact as an additional instance of the 
transmission of the equal-styled Tariety. 

The third lot in the table, namely the Baston plants, are the 
last which need be mentioned. The long and short-styled plants, 
and the fifteen equal-styled plants, were desceaded from two 
distinct slocks. The latt«r were derived from a sit^le plant, 
which the gardener is positive was not long-atjled ; hence, pro- 
bably, it was equal-styled. In all these fifteen plants the anthen, 
occapying the same position as in the long-styled form, closely 
surrounded the stigma, which in ono instance alone was slightly 
elongated. Notwithstanding this position of the stigma, the 
Bowers, as the gardener assorod me, did not yield many seeds ; 
and this difference from the forgoing cases may perhaps have 
been caused by the pollen being bad, as in some of the South- 
ampton equal-styled plants. 



Conclusions mth respect to the equal-styled variety t 
P. Sinensis. — That this is a variation, and not a third a 
distinct form, aa in the trimorphic genera Lytkntm aa4j 
Oxalis, is clear ; for we have seen its first appearance 
in one out of ft lot of illegitimate long-styled plants ; 
and in the case of Mr. Duck's seedlings, long-atyled 
plants, only slightly deviating from the normal stAte, 
as well as equal-styled plants were produced from theuj 
same self-fertilised parent. The position of the sta 
mens in their proper place low down in the tube of th^ 
corolla, together with the small size of the pollen- 
grains, show, firstly, that the equal-styled variety ia a * 
modification of the long-styled form, and, secondly, that 
the pistil ia the part which has- varied most, aa indeed 
was obvious in many of the plants. This variation is 
of frequent occurrence, and ia strongly inherited when 
it haa once appeared. Tt would, however, have pofr i 



uth- I 

do^^H 
incct^^H 
rled 

lien- ^^ 



Chap. V. HETEItOSTYLED DIMOEPHIC PLANTS. 



223 



Boaaed little interest if it had consisted of a mere 
change of structure ; but this is accompanied by modi- 
fied fertility. Its occurrence apparently stands in 
close relation with the illegitimate birth of the parent 
I plant ; but to this whole subject I shall hereafter 



Altlitragh I made no experiments on the illogitimafe offspring 
of this species, I refer to it for two reasoDB ;— First, because 
I Lave observeii two equal-styled plants in wliich the pistil 
reeembled in all reapecta that of the long-stjled form, whilst 
the stamens had become elongated as in the short-styled form, 
so that the stigma was almost Gurrounded b; the anthers. The 
pollen-grains, however, of the elongated stamens resembled in 
their amall size those of the shorter etamens proper to the long* 
Btyled form. Hence these plants hnve become oqual-styled by 
the increased length of the stamens, instead of, aa with P. 
' Sineneu, by the diminished length of the pistil. Mr. J. Scott 
K observ^ five other plants in the same state, and he shows * that 
W one of them, when self-fertilised, yielded more seed than an 
I ordinary long- or short-styled form would have done when 
similarly fertiUsed, but that it was far inferior in fertility to 
either form when legitimately crossed. Hence it appears tbat 
the male and female organs of this equal-stylcd variety have 
been modified in some special manner, not only in structure 
but in functional powers. Ibis, moreover, is shown by the 
singular lact that t»th the long-styled and short-styled plants, 
fertilised with pollen from the equal-styled variety, yield a 
lower avenge of seed than when these two forms are fertilised 
with their own pollen. 

The second point which deserves notice is that florists alwaj-g 
throw away the long-styled plants, and save seed exclusively 
_from the short-styled form. NeverthelesB, as Mr. Scott mils 
informed by a man who raises this upecies extensively in Scot- 
land, aljout one-fourth of tlie seedlings appear long-sty]c<l ; so 
that the short-styled form of the Auricula, when fertilised by 
Q pollen, does not reproduce the same form in so large a 
I proportion as in the case o( J'. Sinensis. We may furtlier infer 

• "Jounuil Proc Linn. Son.' viii, (IS64) p. 91. 



224 



ILLEGITIMATE OFFSPHING OF 






that the ehort-Btyled form la not renderod quite sterila liy a' 
long course of fertilisation, with pollen of tlie Eame form ; but as 
tliere would always be Boine linbility to an oocaaioDal cross with 
the other fonn, we cannot toll how long eclf-fertilisatioii has 
been continued. 

FRiiini.A FAntNDsA. 
Mr. Sn>tt BfiyE * that it is not at all nncommon to find eqonl-' 
Btyled plants of this heterostyled species. Judging from the 
size of the pollen-grains, these plants owe their stmctiire, as in 
the CORO of F. aurimln, to the abnormal elongation of the 
stamens of the long-styled form. In accordance with this Tiew, 
they yield less seed when crossed with the long-styled form 
than with the short-styled. Bat thoy differ in an anomaloua 
manner from the eqtutl-styled plants of P. auricula in being 
extremely sterile with their own pollen. 

Pbimtila elatiob. 
It was shown in the first chapter, on the authorilj of 
Herr Breitenbach, that equal-styled flowers are occasionally 
found on this species whilst growing in a state of nature ; and 
this is the only instance of such an oociuTence known to me, 
with the exception of some wild plants of the Oxlip — a hybrid 
between P. veris and volgaris — which were eqnal-styled. Herr 
Breitenbach's case is rcmarkatile in another way; for equal- 
styled flowers were found in two inslauees on plants whioh bore 
both long-styled and short-styled flowers. In every othe^ 
instance these two forms and the equal-styled Toriety hare beat' 
prodnoed by distinct plants. 

Primula vclqabib, Brit. FL 

Var. acaulis of Linn, and P. aeaulis of Jacq. 

Var. rubra. — Mr. Scott etatest that tliia variety, wMchd 
grew in tlie Botanic Garden in Edinljiirgh, was ( 
sterile when fertilised with pollen from the conimoa^ 
primrose, as well aa from a white variety of the samA 1 

' viii. (I8«), p. US. 



4 
4 




rCBAP. V. HETEEOSTYLED DIMOHPHIC PLANTS. 



225 



I 
I 



Bpecies, but that some of the planta, when artifliiklly 
fertilised with their own pollen, yielded a moderate 
supply of seed. He was so kind as to send me some 
of these self-fertilised seeds, from which I raised the 
plants immediately to be described. I may premise 
that the results of my experiments on the seedlings, 
made on a large scale, do not accord with those by 
Mr. Scott on the parent-plant. 

First, in regard to the transmission of form and 
colour. The parent-plant waa long-styled, and of a 
rich purple colour. From the self-fertilise J seed 23 
planta were raised ; of these 18 were purple of dif- 
ferent shades, with 2 of them a little streaked and 
freckled with yellow, thus showing a tendency to 
reversion ; and 5 were yellow, but generally with a 
brighter orange centre than in the wild flower. All 
the planta were profuse flowerers. All were long- 
Btyled ; but the pistil varied a good deal in length 
even on the same plant, being rather shorter, or con- 
siderably longer, than in the normal long-styled form ; 
and the stigmas likewise varied in shape. It is, 
therefore, probable that an equal-styled variety of the 
primrose might he found on careful search; and I 
have received two accounts of plants apparently in this 
condition. The stamens always occupied their proper 
position low down in the corolla ; and the pollen- 
grains were of the small size proper to the long-styled 
form, but were mingled with many minute and 
shrivelled grains. Tho yellow-flowered and the purple- 
flowered plants of this first generation were fertilised 
under a net with their own jwllen, and the seed sepa- 
rately sown. From the former, 22 plants were raised, 
and all were yellow and long-styled. From the latter 
or the purple-flowered plants, 24 long-styled planta 
were raised, of which 17 were purple and 7 yellow. 



ILLEGITIMATE OFFSPRING OF 



In this last i 



! have 8 



i of r 



I instance ( 

colour, without the possibility of any cross, to the grand- 
parents or more distant progenitors of the plants in 
question. Altogether '23 plants in the first generation 
and 46 in the second generation were raised ; and the 
whole of these 69 illegitimate plants were long-styled ! 

Eight purple-flowered and two yellow-flowered planta 
of the Srst illegitimate generation were fertilised in 
various ways with their own pollen and with that of 
the common primrose ; and the seeds were separately 
counted, hut as I could detect no difference jn fertility 
between the purple and yellow varieties, the result* 
are run together in the following table. (See next 
page.) 

If we compare the figures in this table with those 
given in the first chapter, showing the normal fertility 
of tlie common primrose, we shall see that the illegiti- 
mate purple- and yellow-flowered varieties are very 
sterile. For instance, 72 flowers were fertilised with 
their own pollen and produced only 11 good capsules ; 
but by the standard they ought to have produced 48 
capsules ; and each of these ought to have contained 
on an average 522 seeds, instead of only 11-5 seeds. 
When these plants were illegitimately and legiti- 
mately fertilised with pollen from the common prim- 
rose, the average numbers were increased, but were far 
from attaining the normal standards. So it was when 
both forms of the common primrose were fertilised 
with pollen from these illegitimate plants; and this 
shows that their male as well as their female organs 
were in a deteriorated condition. The sterility of these 
plants was shown in another way, namely, by their not 
praducing any capsules when the access of all insects 
(except such minute ones as Thrips) was prevented; 
for under these circumstances the common long-styled - 



CflJP. V. HETEEUSTYLED DIMORPHIC PLANTS. 227 ^M 

lASLB 32. H 
Primula vulgaris, ^M 




'1 


ll 
1 




l.i 

111 


If 


Purple- and jeUgw-flovrered illegi- 
timste loQg-slyled plants, illegi- 
timale!;/ furlilbed with polleD 
from the sama pLmt .... 


72 




11-5 


26 


- 


PurplB- uid jellow-flowered illegj. 
tim«te loBg-iljled plHOM, iilegi- 
timely fsrlilLed with pollen 
from tho commgn long-ttjied 
primroM 

Or, if tho ton poopost capsules, 
including lou ihim 15 Mods, bo 
rejected, wo got. . . . . 


72 
73 


39 
'9 


31-4 
4Q-6 


63 
6j 


3 


Purplo- nad yeltaw-flowcrod illcgi- 
timato loDg-et7l«d plants, le.,i- 
th,uiteli/ fertiliood with poliea 
trom the commao shurl-sty led 
primrom 

Or, if the two poere:.t cauales, 
Inclnding less than 15 BoedB, be 
rejected, we get 


26 

36 


18 


38-4 


60 
bo 


9 
IS 


priinroM, ale-jit-niatel;/ fertilisod 
with pollon from tho iong-eljried 
il leg] timato purple- and jel low- 
flowered plant! 

Or, if the throe puorest capenle^ 
bo rejected, we gel . .... 


20 


14 


15-4 

iB-9 


46 
46 


e 


The ehort-ityled form of thocotninon 

with pollen from thslong-»tylo.l 
ilUgltimnte purple- nnU jeliow- 
fliiivctod pkuu 


10 


e 


SO'S 


61 


primrose produces a considerable number of capsules. ^H 
There can, therefore, be no doubt that the fertility of H 



228 



nXEOITIMATE OFF8PBD!« OP 



Uii^ae pUnta was gre&tlj impaired. The loas is not 
eorreUted with the colour of the flower ; and it was to 
ascertain this point that I made Bo many experiments. 
Afl the parent-plant growing in Edinburgh was foimd 
by Mr. Scott to oo in a high d^ree sterile, it may 
hare transDiifted a similar tendency to its ofll^pritig, 
independently of their iliegitimate birth. I am, how- 
ever, inclined to attribute sonte weight to the illegiti- 
macy of their descent, both &oni the analogy of other 
cases, and more especially from the fact that when the 
plants were legUinteUdy fertilised with pollen of the 
common primrose they yielded an average, as may be 
seen in the table, of only 5 more seeds than when 
illeffitimatdy fertilised with the same pollen. Now we 
know that it is emiEently characteristic of the illegiti- 
mate offspring of Primtda Sinensis that they yield but 
few more seeds when legitimately fertilised than when 
fertilised with their own-form pollen. 



i\ 



Pbimola vebis, Brit. Fl. 

Var. o§ieinalis of Linn,, P. officinalis of Jacq. 

Seeds from the short-styled form of the cowslip 
fertilised with pollen from tke same form germinate 
so badly that I raised from three successive sowings 
only fourteen plants, which consisted of nine shorts 
styled and five long-styled plants Hence the shorts 
styled form of the cowslip, when self-fertilised, does not 
transmit the same form nearly so truly as does that 
of P. Sinensis. From the long-styled form, always 
fertilised with its own-form pollen, I raised in the 
first generation three long-styled plants, — from their 
seed 53 long-styled grandchildren, — from their seed 
4 long-styled great-grandchildren, — from their seed 
20 long-styled great-great-grandchildrcn.^aiid lastly. 



I Chap. V. HETEROSTYLED DIMORPHIC PLANTS. 



223 



I 
I 



from their seed 8 long-styled and 2 short-styled great- 
great-great-grandchildren. In this last generation 
shortrstylcd plants appeared for the first time in the 
course of the six generations, — the parent long-styled 
plant which was fertilised with pollen from another 
plant of the same form heing counted as the first 
generation. Their appearance may be attributed to 
atavism. From two other long-styled plants, fertilised 
with their own-form pollen, 72 planta were raised, 
which consisted of 68 long-styled and 4 short-styled. 
So that altogether 162 plants were raised from ille- 
gitimately fertilised long-styled cowslips, and these 
consisted of 156 long-styled and 6 shorl^styled plants, 

We will now turn to the fertility and powers of 
growth possessed by the illegitimate plants. From 
a short-styled plant, fertilised with its own-form 
pollen, one short^styled and two long-styled plants, 
and from a long-styled plant similarly fertilised three 
long-styled plants were at first raised. The fertility 
of these six illegitimate plants was carefully obserred ; 
but I must premise that I cannot give any satisfactory 
standard of comparison as far as the number of the 
flceda is concerned ; for though I counted the seeds 
of many legitimate plants fertilised legitimately and 
illegitimately, the number varied so greatly during 
successive seasons that no one standard will serve well 
for illegitimate unions made diu:ing different seasons. 
Moreover the seeds in the same capsule frequently 
differ BO much in size that it is scarcely possible 
to decide which ought to be counted as good seed. 
There remains as the best standard of comparison the 
proportional number of fertilised flowers which pro- 
duce capsules containing any seed. 

First, for the one illegitimate short-styled plant. 
In the course of three seasons 27 (lowers were illegiti- 



230 



ILLEGITIMATE OFFSPBINO OF 



nifttely fertilised with pollen from the same plant, and 
they yielded only a single capsule, which, howeyer, con- 
tained a rather large number of seeds for a union of 
this nature, namely, 23. As a standard of comparison 
I may state that during the same three seasons 44 
flowers borne by legitimate short-styled plants were 
self-fertilised, and yielded 2ti capsules; so that the 
fact of the 27 flowers on the illegitimate plant having 
produced only one capsule proves how sterile it was. 
To show that the conditions of life were favourable, 
1 will add that numerous plants of this and other 
species of Primula all produced an abundance of 
capsules whilst growing close by in the same soil with 
the present and following plants. The sterility of the 
above illegitimate short-styled plant depended on 
both the male and female organs being in a deterio- 
rated condition. This was manifestly the case with 
the pollen ; for many of tlie anthers were shrivelled 
or coutabescent. Nevertheless some of the anthers 
contained pollen, with which I succeeded in fertilising 
some flowers on the illegitimate loug-styled plants 
immediately to be described. Four flowers on this 
same short-styled plant were like*vise legiiimatdy fer- 
tilised with pollen from one of tlie following long- 
styled plants ; but only one capsule was produced, 
containing 26 seeds ; and this is a very low number 
for a legitimate imion. 

With respect to the five illegitimate long-styled 
plants of the first generation, derived from the above 
self-fertilised short-styled and long-styled parents, 
their fertility was observed during the same three 
years. These five plants, when self-fertilised, differed 
considerably from one another in their degree of 
fertility, as was the case with the illegitimate long- 
styled plants of Lythrum salicaria ; and their fertUiiy 



Kkaf. V. HETEEOSTYLED DIMORPHIC PLANTS. 



231 



' varied much according to the season, I may premise, 
as a standard of comparison, that during the same 
years 56 flowers on legitimate loug-atyled plants cf 
the same age and gro^vn in the same soil, were fer- 
tilised with their own pollen, and yielded 27 capsules; 
that is, 48 per cent. On one of the five illegitimate 
long-styled plants 36 flowers were self-fertilised in 
the course of the three years, but they did not produce 
a single capsule. Many of the anthers on this plant 
were contabescent ; but some seemed to contain 
sound pollen. Nor were the female organs quite 
impotent ; for I obtained from a legitimaie cross one 
capsule with good seed. On a second illegitimate 
long-styled plant 44 flowers were fertilised during the 
same years with their own pollen, but they produced 
only a single capsule. The third and fourth plants 
were in a very slight degree more productive. The 
fifth and last plant was decidedly more fertile ; for 
42 self-fertilised flowers yielded 11 capsules. Alto- 
gether, in the course of the three years, no less than 
160 flowers on these five illegitimate long-styled 
plants were fertilised with their own pollen, but they 
yielded only 22 capsules. According to the standard 
above given, they ought to have yielded 80 capsules. 
These 22 capsules contained on an average 15 ■ 1 seeds. 
I believe, subject to the doubta before specified, that 
with legitimate plants the average number from a 
union of this nature would have been above 20 seeds. 
Twenty-four flowers on these same five illegitimate 
long-styled plants wore legitimately fertilised with 
pollen from the above-described illegitimate short- 
Btyled plant, and produced only 9 capsules, which is 
an extremely small number for a legitimate union. 
These 9 capsules, however, contained an average of 38 
apparently good seeds, which is as large a number as 



L 



232 



ILLEGITIMATB 0FF8PEIK0 OF 



ClIAP. 1 



legitimate plants sometimes yield. But this high aver- 
age was almost certainly falae ; and I mention the caso 
for the sake of ahowing the difficulty of arriving at a 
fair result ; for this average mainly depended on two 
capsules containing the extraordinary numbers of 7J 
and 5C seeds ; these seeds, however, though I felt 
bound to count them, were so poor that, judging from 
trials made in other cases, I do not suppose that one 
would have germinated ; and therefore they ought not 
to have been included. Lastly, 20 flowers were legiti- 
mately fertilised with pollen from a legitimate plant, 
and this increased their fertility; for they produced 
10 capsules. Yet this is but a very small proportion 
for a legitimate union. 

There can, therefore, be no doubt that these &■ 
long-styled plants and the one short-styled plant 
the first illegitimate generation were extremely aterili 
Their sterility was shown, as in the case of hybri(" 
in another way, namely, by their flowering profusely, 
and especially by the long endurance of the flowers. 
For instance, I fertilised many flowers on these plants, 
and fifteen days afterwards (viz. on March 22nd) I 
fertilised numerous long-styled and short-styled flowers 
on common coivslips growing close by. These latter 
flowers, on April 8th, were withered, whilst most of the 
illegitimate flowers remained quite fresh for several 
days subsequently ; so that some of these illegitimate 
plants, after being fertilised, remained in full bloom 
for above a month, 

We will now turn to the fertility of the 53 illegi 
mate long-styled grandchildren, descended from the 
long-styled plant which was first fertilised with its 
own pollen. The pollen in two of these plants included 
K multitude of small and shrivelled grains. Never- 
theless they were not very sterile; for 25 flowers, fe^, 



cea 

ion ^^ 

'i 



p. T. HEl-EHOSTYLED DIMOEPHIC PLANTS. 



233 



" tiliaed with their own pollen, produced 15 capsulea, 
containing an average of 16 '3 seeds. As already 
stated, the probable average with legitimate plants 
for a union of this nature ia rather above 20 seeds. 
These plants were remarkably healthy and vigorous, 
as long as they were kept under highly favourable 
conditions in pots in the greenhouse ; and such treat- 
ment greatly increases the fertility of the cowslip. 
When these same plants were plained during the next 
year (which, however, was an unfavourable one), out 

I of doors in good soil, 20 self-fertilised flowers pro- 

I liuced only 5 capsules, eontaiuing extremely few and 
wretched seeds. 

Four long-styled great-grandchildren were raised 
from the self-fertilised grandchildren, and were kept 
under the same highly favourable conditions in the 
greenhouse; 10 of their flowers were fertilised with 
own-form pollen and yielded the large proportion of 6 
capsules, containing on an average 18' 7 seeds. From 
these seeds 20 long-styled great-great-grandchildren 
were raised, which were likewise kept in the greenhouse. 
Thirty of their flowers were fertilised with their owo 
pollen and yielded 17 capsules, containing on an aver- 
age no less than 32, mostly fine seeds. It appears, 
therefore, that the fertility of these plants of the fourth 
illegitimate generation, as long as they were kept 
under highly favourable conditions, had not decreased, 
but had rather increased. The result, however, was 
widely different when they were planted out of doors 
in good soil, where other cowslips grew vigorously and 
were completely fertile ; for these illegitimate plants 
now became much dwarfed in stature and extremely 
sterile, notwithstanding that they were exposed to the 
Tisits of insects, and must have been legitimately fer- 

l tilised by the surrounding legitimate planta. A whole 



2a4 ILLEGITIMATB OFFSPBINQ OP 

row of these plants of the fourth illegitimate g 
tioD, thus freely exposed and legitimately fertilised, 
produced only 3 capsules, containing on an average 
only 17 seeds. During the ensuing winter almost all 
these plants died, and the few survivors were miserably 
unhealthy, wliilst the surrounding legitimate plants 
were not in the least injured. 

The seeds from the great-great-grandchildren were 
sown, and 8 long-styled and 2 short-styled plants of 
the fifth illegitimate generation raised. These whilst 
still in the greenhouse produced smaller leaves and 
shorter fiower-atalks than some legitimate plants with 
which they grew in competition ; hut it should be ob- 
served that the latter were the product of a cross with 
a fresh stock, — a circumstance which by itself would 
have added much to their vigour." When these ille- 
gitimate plants were transferred to fairly good soil 
out of doors, they became during the two following 
years much more dwarfed in stature and produced very 
few flower-stems ; and although they must have been 
legitimately fertilised by insects, they yielded cap- 
sules, compared with those produced by the surround- 
ing legitimate plants, in the ratio only of 5 to 100! 
It is therefore certain that illegitimate fertilisation, 
continued during successive generations, affects the 
powers of growth and fertility of P. veris to an extra- 
ordinary degree ; more especially when the plants are 
exposed to ordinary conditions of life, instead of being 
protected in a greenhouse. 

Equal-styled red vitrieiy of P. veris. — Mr. Scott has described f 
ft plant of this kind growing in the Botanic Garden of Edin- 
burgh, He states that it waa highly self-fertile, although insects 

• Pot fnU detaila of tliig ei- 
perinieiit, ace my ' EtTecta of Cmis 
ind Se)f-rL'rtili8atiim,' 1876, p. 220. 



f Okw. Y. HETEBOSTYLED DDIOHPfflO PLANTS. 



235 



I 

I 



were excluded ; and he eiplains this fact by stowing, first, that 
the anthers and stigma, are in dose apposition, and that the 
BtameiiB in length, position and eiza of their pollen-grains 
resemble those of the short-styled form, wliilst the piatil re- 
sembles that of the long-stjled form both in length and in the 
Bttuctui'e of the stigma. Hence the self-union of this Tarioty ia, 
in fact, a legitimate union, nnd consequently is highly fertile. 
Mr. Scott further states that this yariety yielded very few seeds 
when fertilised by either the long- or short-stylal common 
oowshp, and, again, that both forms of the latter, when fertilised 
by the eqiial-styled variety, likewise produced very few seeds. 
Bnt hia eiperiments with the cowslip wore few, and my results 
do not confirm his in. any uniform manner. 

I raised twenty plants from self-fertilised seed sent me by Sir. 
Scott; and thoy all produced red flowers, varying slightly in 
tint Of these, two were strictly long-styled both in structure 
and in function ; for their reproductive powers were tested by 
orofisea with both forms of the common cowslip. Sis plants 
were equal-styled ; but on the same plant the pistil varied a 
good deal in length dining different seasons. This was likewise 
the case, according to Mr. Scott, with the pacent-plaat. Lastly, 
twelve plants were in appearance short-styled ; but they varied 
much more in the length of their pistila than ordinary short- 
Btyled cowshps, and they differed widely from the latter in 
their powers of reproduction. Their pistils had become short- 
styled in Btmcture, wliilst remaining long-styled in fuuctisn. 
Short^tyled cowslips, when insects are excluded, ore extremely 
barren : for instance, on one occasion six fine plants produced 
(mly about 50 seeds (that is, less than the product of two good 
cBpsulea), and on another occasion not a single eapsnle. Now, 
when the above twelve apparontiy short-styled seedlings were 
Bimilarly treated, nearly all produced a great abundance of 
oapsu^ui, containing numerous seeds, which germinated to- 
markably well Moreover three of these plants, which during 
tiie first year were furnished with quite short pistils, on the 
following year produced pistils of extraonlinury length. The 
greater munber, therefore, of these short-styled plants could not 
be distinguished in function from the equal-styled variety. The 
anthers in the six equal-siyled and in the apparently twelve 
Bbort-styled plants were seated high up in the corolla, as in the 
true short-styled cowslip; and the pollen-grains resembled 
those of the same form in their bu'ge size, but were mingled 



236 



ILLEGITIMATE OFFSFEINa OY 



Chap. T 



with a few shrivelled Btainsi In function this pollen w»a 
identit^al with that of the short-fityled cowalip; for ten loi^ 
staled flowere of the cocamon cowslip, legitimately feitiliBed 
with pollen from a true equal-styled v&rietj. prodnccd six cap- 
nnles, containing oa an average 3i-4 seeds; whilst eeyen 
Bales on a short-styled cowBlip ill^timately fi-rtiliEcd wil 
pollen from the equal-styled Tariety, yielded an avarago of 
14-6 seeds 

As the equol-stylod plants differ from one another in tlieir 
powers of reproduction, and as this is an important Bnbjeot, 
I will gire a few details with respect to five of them. First, an 
equal-Gtyled plant, protected &om insects (as was done in all 
the following coses, with one stated exception), Bpontaneoualy 
produced nomerous capsules, five of which gave an average of 
4i'8 i;eeds, with a maximum in one capsule of 57. But sis 
capsules, the product of fertilisation with pollen from a short- 
styled cowshp (and this is a Ic^tioiate onion), gave an aTer^e 
of 28 ' 5 Beads, with a maximum of 49; and this is a much lower 
average than might have been expected. Secondly, nine cap- 
snles from another equal-styled plant, which had not been 
protected from insects, but probably was eelf-fertihsed, gave an 
average of 45 * 2 seeds, with a maximum of 58. Thirdly, another 
plant which hod a very short pistil in 1S65, produced spon- 
taneously many capsules, six of which contained an average rf 
33 ' d seeds, with a maximum of 3Sl In 18C6 this same plant 
had a pistil of wonderful length ; for it projected quite atova 
the anthers, and the stigma resembled that of the long-styled 
form. In this condition it produced S]xintanooiiEly a yaat 
number of fine capsules, six of which contained almost exactly 
the same average number as before, viz. 34-3, with a moximnm 
of 38. Four flowera on this plant, legitimately fertilised with 
pollen from a ahort-stjled cowslip, yielded capsules with an 
average of 30-2 seeds. Fourthly another shortr^led plant 
spontaneously produced in 1865 an abundance of capsules, ten 
of which contained an average of 35 ■ 6 seeds, with a rnaTiTn um 
of 54. In 18G6 this same plant had become in all respects lon^ 
styled, and ten capsules gave ahnost exactly the same average 
as before, viz, 35 ■! seeds, with a maximum of 47. 
flowers on this plant, legitimately fertilised with polli 
a short-styled cowslip, produced six capsules, with the hi) 
average of 63 seeds, and the high mariTnnig of 67. ] 
flowera were also fertilised with pollen from a long-styled 



cap- . 

cap-^^ 

onll^H 

their ^^^ 



Chap.T. HETEEOSryLED DIMOEPHIO PLASTS. 



237 



I 



slip (this being an illegitimate union), and produced eeven 
capsules, containing an average of 24 '4 seeds, with a masimuni 
of 32. The fifth and last plant remained in the same condition 
during both years : it had a pistil rather longer than that of the 
true ehort-styled form, with the stigma smooth, as it ought to 
bo in this form, but abnormal in ehaiie, like a much-elongated 
inverted cone. It produced spontaneously many capsules, five 
of which, in 1B65, gave an average of only 15-6 seeds; and in 
186G ten capsules still gave an average only a little higher, liz. 
of 22'1, with a maximum of 30. Sixteen flowers were fertiliBed 
with pollen from a long-styled cowslip, and produced 12 cap- 
sules, with an average of 24 9 seeds, and a maximum of 42. 
Eight flowers were fertilised with pollen from a Bhort-styled 
cowslip, but yielded only two capsules, containing 18 and 23 
seeds. Hence this plant, in function and partially in structure, 
was in on almost exactly intermediate state between the long- 
styled and short^tyled form, but inclining towards the short- 
styled ; and this accounts for the low average of seeds which it 
produced when spontaneously self-fertiliBod. 

The foregoing five plants thus differ much from one another in 
the nature of theii fertihty. In two individuals a groat difference 
in the length of the pistil during two succeeding years made no 
difference in tiia mimbsr of Eecds produced. Ab aU five plaata 
possessed the male o^ans of the short-styled form in a perfect 
atate, and the female organs of the long-styled form in a more 
or less complete state, they spontaneously produced a sniprising 
number of capsules, which generally contained a large average 
of remarkably fine seeds. With ordinary cowslips, hgitimatdy 
fa-tilisfd, I once obtained from plants cultivated in the green- 
house the high ayerage, from seven capsules, of 68 ■ 7 seeds, with 
It maximum in one capsule of 87 seeds ; but from plants grown 
out of doors I never obtained a higher average than 41 seeds, 
Kow two of the equal-slyled plants, grown out of doors and 
spontaneously siyyerMisei/, gave averages of 44 and 45 seeds; 
bnt this high fertihty may perhaps be in part attribnted to the 
stigma receiving pollen from the Burroimding anthers at exactly 
(he right period. Two of these plants, fertilised with pollen 
from a short-styled cowslip {and this in fact is a legitimate 
■onion), gave a lower average than when self-fertilised. On the 
other hand, another plant, when similarly fertilised by a eowshp, 
yielded the unusually high average of 53 seeds, with a maximum 
ijf IJ7. Lastly, as we liavo ju.st seen, one of these plants was in 



ILLEGITIMATE 0PP8PBISO OP 



Chaf, V. 



an almost oiacllj iittermedjato condition in its female ot^ans 
Iwtween the long- and ehort-etyled forms, and conseiinently, 
wben Belf-fertilised, yielded a low average of eeed. If we add 
together all the esperimenta which I made on the eqnal-sfyled 
plants, 41 Bpontanooiialy Belf-fertilised capsules (izLsects having 
been exclnded) gave an avera^ of 34 seeds, which is exactly the 
same number ad the pareatr-planl yielded in Edinborgh. ThXrty- 
four Sowers, fertilised with pollen &om the short^tyled cowslip 
(and this is an analogous union), produced 17 capsules, contain- 
ing an average of 33 8 seeds. It is a rather singnlar circton- 
stanoe, for which I cannot account, that 20 flowers, artificially fer- 
tilised on one occasion with pollen from the same plants yielded 
only ten cajwulea, containing the low average of 26-7 seeds. 

As boaring on inheritance, it may be added that 72 seed- 
lings wore raised from one of the red-flowered, strictly eqnal- 
stjled, self-fertilised plants descended from the similarly c!ia- 
lacteriaed Edinburgh plant. These 72 plants were there- 
fore grandcliildren of the Edinburgh plant, and they all bore, 
as in the first generation, red flowers, with the exception of 
one plant, which reverted in colour to the common cowslip. 
In regard to structure, nine plants were truly long-styled 
and hod their stamens scatM low down in the corolla in the 
proper position ; the remaining 63 plants were equal-styled, 
though the stigma in about a dozen of them stood a little below 
the anthers. We thus see that the anomalous combination in the 
same flower, of the male and female eeiual organs which properly 
exist in the two distinct forms, was inherited with much force. 
Thirty-six seedlings were also raised from long and slioit-etyled 
common cowslips, crossed with pollen from tiie equal-styled 
variety. Of these plants one alone was equal-styled, 20 were 
short-styled, but with the pistil in three of them rather too 
long, and the remaining 15 "were long-styled. In this casi 
have an illustration of the difCetence between simple inheritance ( 
and prepotency of transmission ; for the equal-styled variety, \ 
when self-fertiiised, tranBmita its character, as we have just ) 
seen, with much force, but when crossed with the common 
cowslip cannot withstand the greater power of transmisEion i 
of the latter. 

FoLUONAniA. 
I have little to say on this genua I obtained seeds of P. q^ i 
xnalis from a garden where the long-stylod form alone grew, . 



I 



I 



HETEROSTYLED PLANTS. 239 

and loised 11 Bsedlings, whicli were nil long-etjled. These 
plants were named for me by Dr. Hooker, Tliey differed, oa I139 
been Hhown, from the plants belonging to this spocica which in 
Germany were oiperimBiited on by Hildebrand;* for he found that 
the long-styled form was abaolut«ly starile with its own pollen, 
whilst my long-atyled Eeedlinga and the parent-plants yielded a 
fidr supply of seed when self-fertilised. Plants of the long- 
styled form of Pulmonaria angustifolia were, hke Hildebrand's 
plants, absolutely sterile with their own pollen, bo that I could 
never procure a single sjed. On the other hand, the shott- 
styled plants of this species, differently from those of P, nffi- 
dnnlis, were fertile with their own pollen in a quite remarkable 
degree for a heterostyled plant. From seeds carefully self-fer- 
tilised I raised IS plants, of which 13 proved short-stjiod and 
6 long-styled. 

POLYQOSDM FAGOPTKDM, 

From flowers on long-styled plants fertilised ill^itimately 
with pollen from the same plant, 49 seedlings were raised, and 
these consisted of 45 long-styled and 4 short-styled. Prom 
flowers on short-styled plants illegitiiaately fertilised with pollen 
from the same plant 33 seedlings were raised, and these con- 
sisted of 20 short-styled and 13 long-styled. So that the usual 
role of illegitimately fertihsed long-styled plants tending much 
more strongly than short^styled plants to reproduce their own 
torra here holds good. The illegitimate plants derived from, 
both forms flowered later than the legitimate, and were to the 
latter in height as G9 to 100. But as these illegitimate plants 
were descended from parents fertilised with their own pollen, 
whilst the legitimate plants were descended from parents crossed 
with pollen from a distinot individual, it is impossible to know 
how much of thefr difference in height and period of flowering, 
le due to the illegitimate birth of the one set, and how much 
to the other set being the product of a cross between distinct 
plants. * 

I Conduding Bemarlcs on the Ulegiiimate Offspring of 
Heterostyled TrimorpMc and Dimorpliie Plants. 
It is remarkable how closely and in liow many points 
I illegitimate unions between the two or three forms of the 

• ZJot. Zuitnng,' 1SG5, p. 13. 



240 



ILLEGITIMATE OFFSPEING OF 



same heterostyled species, together witli their illegiti 
mate ofbpriug, resemble hybrid uiiiuns between distinof 
Bpecies together with their hybrid offspriag. In botltJ 
cases we meet with every degree of sterility, from very I 
slightly lessened fertility to absolute barrenness, what J 
not even a single seed-capsule is produced. In botlil 
cases the facility of effecting the first union is mucli 
influenced by the conditions to which the plants are 
exposed.* Both with hybrids and illegitimate plants 
the innate degree of sterility is highly variable in 
plants raised from the same mother-plant. In both 
cases the male organs are more plainly affected than 
the female ; and we often find contabeacent anthers 
enclosing shrivelled and utterly powerless pollen- 
grains. The more sterile hybridsj as Max Wichnra 
has well shown,! are sometimes much dwarfed in 
stature, and have bo weak a constitution that they are 
liable to premature death ; and we have seen exactly 
parallel cases with the illegitimate seedlings of Lythrum 
and Primula. Many hybrids are the most persistent 
and profuse flowerers, as are some illegitimate plants. 
When a hybrid is crossed by either pure parent-form, 
it is notoriously much more fertile than when crossed 
inter se or by another hybrid ; so when an illegitimate 
plant is fertilised by a legitimate plant, it is more 
fertile than when fertilised inter se or by another ille- 
gitimate plant. When two species are crossed and 
t!wy produce numerous seeds, we expect as a general 
rule that their hybrid offspring will be moderately 
fertile ; but if the parent species produce extremely-] 
few seeds, we expect that 'the hybrids will be very J 



• Thia has be«ii remarted 1)J 
manyexptrimeniiilislsin effecdng 
DTOEBes between distiDct apeciwt; 
aod in regard tn illcgitimati) 
unioDH I have siren iu thu first 



ohaptoT ti striking iUoatmtion il 

tlieeasu o! FrimiUa vmt. 

t ' Die Bastardliefruulilung b 
PQiinzcnrciab,' 1865. 



HETEROSTYLED PLANTS. 



241 



' sterile. But there ai'e marked exceptions, as shown 
by Gartner, to these rules. So it ia with illegitimate 
unions and illegitimate offspring. Thua the mid- 
styled form of Lythrum salicaria, when illegitimately 
fertilised with pollen from the longest stamens of 
the short-styled form, produced an unusual number 
of seeds ; and their illegitimate offspring were not at 
all, or hardly at all, sterile. On the other hand, the 
illegitimate offspring from the long-styled form, ferti- 
lised with pollen from the shortest stamens of the same 
form, yielded few seeds, and the illegitimate offspring 
thus produced were very sterile ; but they were more 
sterile than might have been expected relatively to the 
difficulty of effecting the union of the parent sexual 
elements. No point is more remarkable iu regard to 
the crossing of species than their unequal reciprocity. 
Thus species A will fertilise B with the greatest ease ; 
but B will not fertilise A after hundre<^ of trials. We 
have exactly the same case with illegitimate unions ; 
for the mid-styled Lythrum salicaria was easily ferti- 
lised by pollen from the longest stamens of the short- 
etyled form, and yielded many seeds ; but the latter 
form did not yield a single seed when fertilised by the 

. longest stamens of the mid-styled form. 

Another important point is prepotency. Gartner 
has shown that when a species is fertilised with pollen 
. from another species, if it be afterwards fertilised with 
its own pollen, or with that of the same species, this 
is 80 prepotent over the foreign pollen that the effect 
of the latter, though placed on the stigma some time 
previously, is entirely destroyed. Exactly the same 
thing occurs with the two forma of a heterostyled 
species. Thus several long-styled flowers of Primula 
veris were fertilised illegitimately with pollen from 
another plant of the same form, and twenty-ftiur houi's 



242 ILLEGITIMATE OFFfiPBING OF Cbiv. '«■ 

afterwards legitimately with pollen from a short-styled 
dark-red pDlyanthus which is a yariety of P. veria; 
and the result was that every one of the thirty seed- 
lings thus raised bore flowers more or less red, show- 
ing plainly how prepotent the legitimate pollen from 
a short-styleil plant was over the illegitimate pollen 
from a long-atyled plant. 

In all the several foregoing points Ihe parallelism is 
wonderfully close between the effects of illegitimate 
and hybrid fertilisation. It ia hardly an exaggeration 
to assert that seedlings from an illegitimately fer- 
tilised heterostyled plant are hybrids formed within 
the limits of one and the same species. This conclu- 
sion is important, for we thus learn that the difficulty 
in sexually uniting two organic forms and the sterility 
of their offspring, afford uo sure criterion of so-called 
specific diatinctuess. If any one were to cross two 
varieties of the same form of Lythrum or Primula for 
the sake of ascertaining whether they were specifically 
distinct, and he found that they could be united only 
with some difllculty, that their offspring were extremely 
sterile, and that the parents and their offspring re- 
sembled in a whole series of relations crossed species 
and their hybrid offspring, he might maintain that hia J 
varieties had been proved to be good and true species j-j 
but he would be completely deceived. lu the s 
place, as the forms of the same trimorpbic or dimorphi 
heterostyled species are obviously identical in genei 
structure, with the exception of the reproductiva« 
organs, and as they are identical in general constitti- J 
tion (for they live under precisely the same condfr< J 
tions), the sterility of their illegitimate unions t 
that of their illegitimate offspring, must depend e 
cluaively on the nature of the sexual elements a 
on their incompatibility for uniting in a partlcula 



HETEROSTYLED PLANTS. 



243 



I 



manner. And as we have just seen that distinct species 
when crossed resemble in a whole aeries of relations the 
forms of the same species when illegitimately united, 
we are led to conclude that the sterility of the former 
must likewise depend exclusively on the incompatible 
nature of their sexual elements, and not on any general 
difference in constitution or structure. We are, indeed, 
led to this same conclusion by the impossibility of de- 
tecting any differences sufficient to account for certain 
species crossing with the greatest ease, whilst other 
closely allied species cannot be crossed, or can be crossed 
only with extreme difBculty. We are led to this con- 
clusion still more forcibly by considering the great 
difference which often exists in the facihty of crossing 
reciprocally the same two species ; for it is manifest in 
this case that the result must depend on the nature of 
the sexual elements, the male element of the one 
species acting Ireely on the female element of the 
other, but not so in a reversed direction. And now we 
see that this same conclusion is independently and 
strongly fortified by the consideration of the illegiti- 
mate unions of trimorphie and dimorphic heterostyled 
plants. In so complex and obscure a subject as hybrid- 
iam it ia no slight gain to arrive at a definite conclu- 
aiou, namely, that we must look exclusively to func- 
tional differences in the sexual elements, as the cause 
of the sterility of species when first crossed and of 
their hybrid offspring. It was this consideration which 
led me to make the many observations recorded in this 
chapter, and which in my opinion make them worthj 
of publication. 



OONCLUDIKG llEMABKS 



CHAPTER YL 

CONCLCDINO BkIURKS OK HETKEOSTTLCri PLAHTa. 






ontely i 



— S-imniBry of tbt 
.A illigitimatelj ter- 
o( anthers and 



tiliaad plaDta — Diiinieler of the pullen-gi 

structuru of Btis'nUi in ^^ difibrcnt forma — AfGnitiea of the gencn 
vhirh incliids heteroatyled BpectoB — Nature of the tdviiolagei 
derived froai htteioatjlLnn — Tho menna by wLich pISiiifB heoame 
hetcroatyled— TransmiBBion of form— Bqnal-gty led TttrieliM 
hetcrnstjltid planla — Fmal remarks. 

In the foregoing chapters all the heterostyled plants 
known to me have been more or less fully described..] 
Several other cases have been indicated, especially by. 
Professor Asa Gray and Kubn,' in which the indi- 
viduals of the same species differ in the length of 
their stamens and pistils ; but as I have been often de- 
ceived by this character taken alone, it seems to me 
the more prudent course not to rank any species as 
heterostyled, unless we have evidence of more impor- 
tant differences between the forma, as in the diameter 
of the pollen-grains, or in the structure of the stigmi 
The individuals of many ordinary hermaphrodite plants 
habitually fertilise one another, owing to their male 
and female organs being mature at different periods, 
or to the structure of the parts, or to self-aterility, &c. 
and so it is with many hermaphrodite animals, for 
instance, land-snails or earth-worms ; but in all these 
cases any one individual can fully fertilise or be ferti 



I 



IP. Vt ON HETEBOSTYLED PLANTS. 245 

f lised by any other individual of the same species. This 
is not so with heterostyled plants ; a long-styled, mid- 
styled or short-styled plant cannot fully fertilise or 
be fertilised by any other individual, but only by 
one belonging to another form. Thus the essen- 
tial character of plants belonging to the heterostyled 
class is that the individuals are divided into two or 
three bodies, like the males and females of dioecious 
plants or of the higher animals, which exist in approxi- 
mately equal numbers and are adapted for reciprocal 
fertilisation. The existence, therefore, of two or three 
bodies of individuals, differing from one another in the 
above more important characteristics, offers by itself 
good evidence that the species is heterostyled. But 
absolutely conclusive evidence can be derived only 
from experiments, and by finding that pollen must be 
applied from the one form to the other in order to 
ensure complete fertility. 

In order to show how much more fertile each form 
is when legitimately fertilised with pollen from the 
other form (or in the case of trimorphic species, with 
the proper pollen from one of the two other forms) 
than when illegitimately fertilised with its own-form 
pollen, I will append a Table (33) giving a summary 
of the results in all the eases hitherto ascertained. 
The fertility of the unions may be judged by two 
standards, namely, by the proportion of flowers which, 
when fertilised in the two methods, yield capsules, and 
by the average number of seeds per capsule. When 
there is a dash in the left-hand column opposite to 
the name of the species, the proportion of the flowers 
which yielded capsules was not recorded. 

The two or three forms of the same heterostyled 
species do not differ from one another in general habit 
',e, as sometimes, though rarely, happens with 



^^r 216 CONCLUDING BEMARKS Cbaf. VI ^^H 

^m Table ^^| 
^V FtrtiUly Iff Hie LegUimale Dniont takm togtther. compartd tnU ^^^| 
■ that o/lhc llhgitimaU Union, togtO.gr. ITu firtUity i^ Ot ^^H 
^H Legitiinats L'nio7ia,a» fudged by balk ttanilarda, is (alien at 100. ^^^H 


^K Nu» of BpKlu. 


lUcgitlmate Unlnu. T 


C^a!». 






69 
27 
60 
84 

100 
80 
S5 
74 
72 
71 
68-4 




35 
20 

33 
2 

15 


65 
75 

64 

43 
15 
31 

48 
44 
68 
61 
69 

ao 



S3 
47 




^1 K vulgaria 

^B P. Sicetub (xeoood trud) 

^H P. SiDBUsli. (Hlldehruid} 

^M P. tnriculii (Scott) 

^1 P. Sikkimemi. „ 

^M P. GOTtU»ldflS „ 

^M p. isirolucrita „ 

^M P. farinosa 

^H Aremgsofthinineitwdesof Ptimaln . 

^P HottoBlii piluitrb (H. Milller) 

^ Unnrn grandiflorum (the diffecenca probably) 
1. much greater) J 

L. perenno 

L. peronne (Hildebr.ind) 

Pnlmauaria officiniilia (German eloi'k, Hildc-1 
brand). J 


MUchella repeni 

Bomria, Broiillaa ip 

Poljgonam fegnpjriim 

^m Ijihtum salicad* 

^K Oialia Valdiviaoa (Hililebraad) 

^B 0. Reguellj „ 

^H 0. tp«ciDaa 


^M the two sexes of dicecious plants. Nor does the caiys. ^^M 
^H differ, but the corolla sometimes dilTers slightly in shape, ^^H 
^1 owing to the different position of the anthers. In Bor- ^^| 

^V In Pulmonaria there is a sliaht difference in the size of ^^1 



Chap. VL 



ON EETEEOSTYLED PLANTS. 



247 



the cjorolla, and in Pontederia in its colour. In the re- 
productive organs the differences are much greater and 
more important. In the one fonn the stamens may be 
all of the same length, and in the other graduated in 
length, or alternately longer and shorter. The fila- 
raenta may differ in colour and thicltness, and are 
sometimes nearly thrice aa long ia the one form as in the 
other. They adhere also for very different proportional 
lengths to the corolla. The anthers sometimes differ 
much iu size in tho two forms. Owing to the rotation 
of the fllamentSj the anthers, when mature, dehisce to- 
wards the circumference of the flower in one form of 
Faramea, and towards the centre in the other form. The 
pollen-grains sometimes differ conspicuously in colour, 
and often to an extraordinary degree in diameter. 
They differ also somewhat in shape, and apparently in 
their contents, as they are unequally opaque. In the 
short-styled ibrm of Faramea the pollen-grains are 
covered with sharp points, so aa to cohere readily to- 
gether or to an insect ; whilst the smaller grains of the 
long-styled form are quite smooth. 

With respect to the pistil, the style may be almost 
thrice as long in the one form as in the other. In 
Oxalis it sometimes differs in hairiness in the three 
forms. In Linum the pistils cither diverge and pass 
out between the filaments, or stand nearly upright and 
parallel to them. The stigmas in the two forms often 
differ much in size and shape, and more especially in 
the length and thickness of their papillie; so that 
the surface may be rough or quite smooth. Owing to 
the rotation of the stylos, the papillose surface of 
the stigma is turned outwards in one form of Linum 
perenne, and inwards in the other form. In flowers of 
the same age of Primula veris the ovules are larger in 
the long-styled than in the short-styled form. The 



CONCLUDIKa BBHABKS 

Beedfl produced by the two or three fomis often differ 
in number, and sonietiines in size and weight ; thus, 
five Boeds from the long-atyled form of Lythrvm soli- 
carta (M^ual in weight six from the miil-styled am! 
seven fr<jm iho ahort-styled form. Lastly, short-atyled 
plants of Ptihnonaria officinalis bear a larger number 
of fiowere, and these set a larger proportional number 
of fruit, which however yield a lower average number 
of seed, than the long-styled plants. AVith hctero- 
atyled plants wo thus see in how many and in what 
important characters the forms of the same undoubted 
epecies often differ from one another— characters which 
with (irdinary plants would be amply sufScient to dis- 
tinguish species of the same genus. 

As tlie pollon-graina of ordinary species belonging 
to the same genua generally resemble one another 
closely in all respects, it is worth while to show, in the 
following tjible (34), the difference in diameter be- 
tween the grains from the two or three forms of the 
same heterostyled species in the forty-three cases in 
which this was ascertained. But it should be observed 
that some of the following measurements are only 
approximately accurate, as only a few grains were 
measured. In several cases, also, the grains had been 
dried and wore then soaked in water. Whenever they 
weto of an elongated shape their longer diameters 
were measured. The grains from the short-styled 
plants are invariably ]a,rger than those from the long- 
styled, whenever there is any difference between them. 
The diameter of the former is represented in the table 
by the number 100. 

We here see tbatj with seven or eight exceptions 
out of the forty-tliree cases, the pollen-grains from one 
form are larger than those from the other form of the 
same species. The extreme difference is as 100 to B5j 



iK>a^H 



ON HETEBOSTYLED PLANTS. 



Bdative DiameUr qf (he Pdlen-grainefrom Ihe/orm* qf the >c 



Seteroityled Specif t 
represenCed hy 100. 



those from llie short-i't/lfd form heitig 



Dtmoi-ph 
From tlie Lon^- 



Eottoniu ml tuti'is (H . &1 III 1 er) 
n {"10 . 
„ perennr(diiimeter' 



■iiibl«). 



■'';jlOO(?} 



r Pulman 



I 



officio nli 

PolfganDTn fHgopjrmn. 
Luncoiiniii BuTDCttiiills 
fgiphila «1aU . . . 
Uanyantbeg tHrolJRU . 
LimouithflTnam ludictitr 
VilUnlii(ip.;). . . 



iJia 



Id dU[Pi!tPr of ih? pallen-grAliK 
two ieU of in ilien In Uu Uim 

I^tbram ullcana . . . 

N«M» Terticlllata . . . 

OiallB Valdiviaoi (Hildebrai 
„ Kegnelli. . . . 

„ MiuitiTa 
PDDt«dBria(i']i.?) . . 



Cordis («p.?) . . . 
Oilii pnlchells . . . 

„ micrantha , , , 
Selhin apumfnata . . 
Erythrojyluni(ap.?) . 
Crntoifloa formosom . 
MitchtflU repon«, pile 

gmios of Iho long-etjled 

alittU emalUr. 
Borreria (sp. ?).... 
F„™m<«L<.p.?) .... 
Suleria(sp.?) (Frill MdlieO 
IfouEtoniii ctcrulea . . . 
Oldeulnndia (Ep. ?) . . . 
Hedj-otia (.p. ?).... 
CoococjpiBlum (»p.?) (F.l 

Milller) , . , , / 
Lipo.toma(.p.?) . . . 
Cinchona micinntlia . . 



Oialia rossa, long^tylKi foml „, 

(Hildebmnd) . . .| "■' 

„ compressa, ibort-gtjledr „ 

Paatederia (sp.?) short-itjlBdl g^ 



and we ahouhl bear in mind that in tlio case of 
spheres differing to this degree in diameter, their 
contents differ in the ratio of six to one. With all 
the species in which the grains differ in diameter, 
there is no exception to the rule that those from the 



250 



CONOLUDINQ 






antliera of the short-styled form, the tubes of wliici 
have to penetrate the longer pistil of the long-styled 
form, are larger than the grains from the other form. 
This curious relation led Delpino* (as it formerly did 
me) to believe that the larger size of the grains in 
the short-styled flowers is connected with the greater 
supply of matter needed for the development of their 
longer tubes. But the case of Linum, in which 
the grains of the two forms are of equal size, whilst 
the pistil of the one is about twice as long as that 
of the other, made me from the first feel very 
doubtful with respect to this view. My doubts have 
since been strengthened by the eases of Limnanthe- 
mum and Coccocypselum, in which the grains are of 
equal size in the two forms ; whilst in the former 
genus the pistil is nearly thrice and in the latter 
twice as long as in the other form. In those species 
in which the grains are of unequal size in the two 
forms, there is no close relationship between the de- 
gree of their inequality and that of their pistils. 
Thus in Piilmomiria q^einaHa and in Erythroxy- 
lum the pistil in the long-styled form is about 
twice the length of that in the other form, whilst in 
the former species the pollen-grains are as 100 to 
78, and in the latter as 100 to 93 in diameter. In 
the two forms of Suteria the pistil differs but little 
in length, whilst the pollen - grains are as 100 tn 
75 in diameter. These cases seem to prove that the 
difference in size between the grains in the two 
forms is not determined by the length of the pistil, 
down wiiich the tubea have to grow. That with 
plants in general there is no close relationship b 



I' Opera, ]il DlBtrlbuzlone dd Seeai aeUe Pionlc^' 



lip betwewi^^W 



I Chap. VI. ON HETEKOSTTLED PLANTS. 



251 



I 



the slzfl of the pollen-grains and the length of the 
pistil is manifest : for instance, I found that tlie dis- 
tended grains of Datura arhorea were "0024^ of an 
inch in diameter, and the pistil no less than 9 25 
inches in length ; now the piatil in the small flowers 
of Polygonum fagopyrum is Tery short, yet the larger 
pollen-grains from the short styled plants had exactly 
the same diameter as those from the Datura, with its 
enormously elongated pistil. 

Notwithstanding these several considerations, it is 
difficult quite to give up the belief that the pollen-grains 
from the longer stamens of heterostyled plants have 
become larger in order to allow of the development of 
longer tubes ; and the foregoing opposing facts may 
possibly be reconciled in the following manner. The 
tubes are at first developed from matter contained 
within the grains, fur they are sometimes exserted 
to a considerable length, before the grains have 
touched the stigma ; but botanists believe that they 
afterwards draw nourishment from the conducting 
tissue of the pistil. It is hardly possible to doubt 
that this must occur in such cases as that of the Da- 
tura, in which the tubes have to grow down the whole 
length of the pistil, and therefore to a length equal- 
ling 3,806 times the diameter of the grains (namely, 
■00243 of an inch) from which they are protruded. 
I may here remark that I have seen the pollen-grains 
of a willow, immersed in a very weak solution of honey, 
protrude their tubes, in the course of twelve hours, to 
a length thirteen times as great as the diameter of the 
grains. Now if we suppose that the tubes in some 
heterostyled species are developed wholly or almost 
wholly from matter contained within the grains, while 
in other species from matter yielded by the piatil, we 
can see tliat in the former case it woiild be necessary 



252 



OONCLUDIXQ BEMABKS 



iLint the grains of tlie two forms shoulJ differ in size 
relatively to the length of the pistil which the tubes 
have to penetrate, but that in the hitter case it would 
not be necessary that the grains should thus differ. 
Whether this espUnation can be considered satisiao j 
tory must remain at present doubtful. ] 

There ia another remarkable difference between the 
forms of several heteroatyled species, namely in the 
anthers of the short-styled flowers, which contain the 
larger pollen-grains, being longer than those of the 
long-styled flowers. This ia the case with Hottonia 
piduatris in the ratio of 100 to 83. With Limnan- 
themam Jndienm the ratio is as lOt) to 70. With the 
allied Menyanthes the anthers of the short-styled form 
are a little and with Villarsia conspicuously larger 
than those of the long-styled. With PtUmonaria 
angudifolia they vary much in size, but from an 
average of seven measurements of each kind the ratio 
is as 100 to 91. In six genera of the Rubiacefe there 
is a similar difference, either slightly or well marked. 
Lastly, in the trimorphic Pontederia the ratio ia 100 
to 88 ; the anthers from the longest stamens in the 
short-styled form being compared with those from the 
shortest stamens in the lung-styled form. On the 
other hand, there is a similar and well-marked differ- 
ence in the length of the stamens in the two forma 
of Forsythia suspensa and of lAnum Jlavum ; but i 
these two cases the anthers of the short-styled flowers \ 
are shorter than those of the long-styled. The rel»* \ 
tive size of the anthers was not particularly attended \ 
to in the two forms of the other heterostyled plants I 
but I believe that they are generally equal, as is 1^ 
certainly the cose with those of the common primrose-fl 
aud cowslip. 

The pistil differs in length in the Ih'o forms of every j 



ON HETEKOSTYLED PLANTS. 



253 



I 
I 



plant, and although a similar difference 
is very general with the stamens, yet in the two 
forms of Linum grandijlorum and of Cordia they are 
equal. There can hardly be a doubt that the rela- 
tive length of these organs is an adaptation for the 
safe transportal by insects of the pollen from the one 
form to the other. The exceptional cases in which 
these organs do not stand exactly on a level in the two 
forms may probably be explained by the manner in 
which the flowers are visited. With most of the 
species, if there is any difference in the size of the 
stigma in the two forms, that of the long-styled, what- 
ever its shape may be, is larger than that of the shorts 
Btyled. But here again there are some exceptions to 
the rule, for in the short-styled form of Leucosmia 
Bumettiajia the stigmas are longer and much narrower 
than those of the long-styled ; the ratio between the 
lengths of the stigmas in the two forms being 100 to 60. 
In the three Eubiaceoua genera, Faramea, Houstonia 
and Oldenlandia, the stigmas of the short-styled form 
are likewise somewhat longer and narrower ; and in 
the three forms of OxcUis senaiiiva the difference is 
strongly marked, for if the length of the two stigmas 
of the long-styled pistil be taken as 100, it will be 
represented in the mid- and short-styled forms by 
the numbers 141 and 1G4. As in all these cases the 
stigmas of the short-styled pistil are seated low down 
within a more or less tubular corolla, it is probable 
that they are better fitted by being long and narrow 
for brushing the pollen off the inserted proboscis of 
an insect. 

With many beterostyled plants the stigma differs 
in roughness in the two forms, and when this is the 
case there is no known exception to the rule that the 
papillie on the stigma of Ibe long-atyled form are longer 



254 



CONCLUMNO EEMAEKS 



and often thicker tbau tbose on tliat of the shoi 
Btyled. For instance, the papilhfi on the long-styied 
stigma of Sottoiiia paluairis are more than twice the 
length of those in the other turm. This holds good 
even in the ease of Souatonia ccerulea, in which the 
stigmas ate much shorter and stouter in the long- 
styled than in the short-styled form, for the paplllie 
on the former compared with those on the latter are 
as 100 to 58 in length. The length of the pistil 
in the long-styled form of Linum grandijlorum variea 
much, and the stigmatic papillie vary in a eorra- 
spending manner. From this fact I inferred at first 
that in all cases the difference in length between tlie 
stigmatic papillie in the two forms was one merely of 
correlated growth ; but this can hardly be the true or 
general explanation, as the shorter stigmas of the 
long-styled form of Houstonia have the longer papillie. 
It is a more probable Tiew that the papillte, which 
render the stigma of the long-styled form of Tarions 
species rough, serve to entangle effectually the large- 
sized pollen-grains brought by insects from the short- 
styled form, thus ensuring its legitimate fertilisation. 
This view is supported by the fact that the poUen- 
grains from the two forms of eight species in Table 
34 hardly differ in diameter, and the papillie on their 
stigmas do not differ in length. ' 

The species which are at present positively or 
almost positively known to be hoterostyled belong, as 
shown in the fullowing table, to 38 genera, widely dis- 
tribnted throughout the world. These genera are 
included in fourteen Families, most of which are very 
distinct from one another, for they belong to nine of 
the several great Series, into which phanerogamie- 
plants have been divided by Bcntham and Hooker. 



i 



4 



I. ON HETEKOSTVLED PLANTS. 

Tadlb 35. 
Lial of Oenera including Heleroslyled Speaiea. 



Erythi-oiylum. EryihrgiyUa 



BouYBidU. 
Uunettii. 
Uedyutia. 



I 

I 



Farsmea. 
Ptjchotria. 



DlCOTTtEDOSB. 



Cordi*. 
Pnlmoniiria. 

Thymelaa. 


Cordiae. 

li.ragin™. 

Verbebnc«B 

ThymelcHj. 


ilosoani\.t,Dosa. 
Funtcderia. PoatsJerlao 



In some of these liimilies the heterostyled condition 
must have been acquired at a very remote period. 
Thus the three closely allied genera, Menyauthea, 
Limnanthemum, and Villaraia, inhabit respectively 
Europe, India, and South America. Heterostyled 
species of Hedyotis are found in the temperate regions 
of North and the tropical regions of South America. 
Trimorpliic species of Oxalis live on both sides of 
the Cordillera in South America and at the Cupe of 
Good Hope. In these and some other cases it is not 
probable that each species acquired its heterostyled 
structure independently of its close allies. If they 
did not do so, the three closely connected genera of 
the MenyanthcK and the several trimorphic species of 
Oxalis must have inherited their structure from a 
common progeuilor. But an immense lapse of time 
will have been necessary in all such cases for the 
modified descendants of a common progenitor to have 



256 



OONCLDDING BKMABK8 



spread frum a single centre to such widely remote and 
separated areus. The family of the Rubiacese contains 
not fur short of as many heterostyled genera as all 
the other thirteen families together; and hereafter 
no doubt otUt-r Rubiaceous genera will be found to] 
be heterostyled, although a large majority are homo- 
styled. Several closely allied genera in this family J 
probably owe their heterostyled structure to descent | 
in common ; but as the genera thus cbaracterbed are [ 
distributed in no less than eight of the tribes into \ 
which this family has been divided by Bentham and ' 
Hooker, it is almost certain that several of them ' 
must have become heterostyled independently of 
one another. What there is in the constitution or 
structure of the members of this family which favours 
their becoming heterostyled, I cannot conjectura 
Some iamilies of considerable size, such as the Bo- j 
ragineffi and VerbenaccEe, include, as far aa is at j 
present known, only a single heterostyled genus. 
Polygonum also is the sole heterostyled genua in its. 
family ; aud though it is a very large genus, no other ] 
species except P. fagopyrum is thus characterised. We 
may suspect that it has become heterostyled within 
a comparatively recent period, as it seems to be leas 
strongly so in function than the species in any other 
genus, for both forms are capahle of yielding a con- 
siderable number of spontaneously self-fertilised seeds. I 
Polygonum in possessing only a single heterostyled 1 
species is an extreme case; hut every other genus of I 
considerable size which includes some such species 1 
likewise contains homostyled species. Lythrum in- 
cludes trimorphic, dimorphic, and homostyled s 

Trees, bushes, and herbaceous plants, both large 
and small, bearing single flowers or flowers in dense 



spi 



Itea or heads, have been rendered heterostyled. 



ON HETEROSTYLED PLANTS. 



257 



I 
I 



Bo have plants which inhabit alpine and lowland sites, 
dry land, marshes and water.* 

When I first began to experimentiae on hetero- 
gtyled plants it was under the impreaaion that they 
were tending to become dioecious ; but I was soon forced 
to relinquish this notion, as the long-styled plants of 
Primula which, from possessing a longer pistil, larger 
stigma, shorter stamens with smaller pollen-grains, 
seemed to be the more feminine of the two forms, 
yielded fewer seeds than the short-styled plants which 
appeared to be in the above respects the more mascu- 
line of the two. Moreover, triraorphic plants evidently 
come under tho same category with dimorphic, and 
the former cannot be looked at as tending to become 
dioecious. With Li/thrum aalioaria, however, we have 
the curious and unique case of the mid-styled form 
being more feminine or less masculine in nature than 
the other two forma. This is shown by the large 



• Out of the 38 genera koowa 
to Inoluda hehTOBtjIed 8p<^cie»^ 
about eiKlit. or 21 per oeat,, are 
more or !e^ aJiualic ia their 
habila. I whb at tirst Btmck with 
this fuot, foi I naB not then BWaru 
how lurge a ptoportiun of or- 
dinury plantB inhabit eunh ata- 
tiona, Htterostyltd plonta may 
be Bald ia one sense to have their 
■exes separated, as the forms must 
mutually fertilise one another. 
Tbetefore it seemed north while 
to asoertain what proportion ot 
flle genera in the Linneitii oIobbcb, 
HuniBolB, DimoLS and Poty< 
nmia, contained spevica wliieh 
Mve "in water, iuar:ihoa. bogs or 
watery places." In Sir W. J. 
Hooker's ■ Britiah Flora' (4ih 
edit. 1833) these tbrve Linnean 
Bluaes Inolado 40 genera, 17 of 



whioh (i.e. JS per OQnt.) cootnin 
EpeoieB inhnbiting the juat-apeci- 
fii'd stiitionit. So that 43 peroQiit. 
of those Britiah pi an la nhiob 
have their BeitiB Bepanited aru 
mnre or \uia aqniitio iu thetr 
habits, wliercas only 21 per oent. 
of heteroslyltd plants have snch 
babila. I may add that tlie ber- 
DnLpliroditu classes, ^in Monan- 
dria to GynandriiL iiiolusive, con- 
lain 447 t^enura, of whi<.'h 113 are 
aquatic in the above BonHO, or only 
15 per cent. It lliuB appears, as 
far as ean be judged from such 
imperfect dnla, that there is some 
oriQUection bi^twean the sepBiBtion 
of the sPleB in plants and the 
wiitary nature of tho sites »bii.'h 
they inhabit ; but thut tliia does 
not bold good wltb LelertNityled 



258 



CONCLUCUfa BEMABKS 



number of seeila which it yields in whateyer i 
it may be fertilised, and by its pollen (the grains of 
which are of smaller size than those from the corre- 
sponding stamens in the other two forms) when 
applied to the stigma of any form producing fewer 
seeds than the normal number. If we suppose the 
process of deterioration of the male organs in the mid- 
styled furm to continue, the final result would be the 
production of a female plant ; and Lythram salicaria 
would thon eonsist of two heterostyled hermaphrodites 
and a female. No such case is known to exist, but it 
is a possible one, as hermaphrodite and female forms 
of the same species are by no means rare. Although 
there is no reason to believe that heterostyled plants 
are regularly becoming diteeioua, yet they offer sin- 
gular facilities, as will hereafter be shownj for such 
conversion ; and this appears occasionally to have been 
effected. 

We may feel sure that plants have been rendered 
heterostyled to ensure cross-fertilisation, for we now 
know that a cross between the distinct individnala of 
the same species is highly important for the TJgour and 
fertility of the offspring. The same end is gained by 
dichogamy or the maturation of the reproductive ele- 
ments of the same flower at different periods, — by 
diceciousness — self-sterility — the prepotency of pollen 
from, another individual over a plant's own pollen, — and 
lastly, by the structure of the flower in relation to the 
visits of insects. The wonderful diversity of the means 
for gaining the same end in this case, and in many 
others, depends on the nature of all the previous 
changes through which the species has passed, and on 
the more or less complete inheritance of the successive 
adaptations of each part to the surrounding conditions. 



ON HETEBOSTYLED PLANTS. 



259 



I 



Plants wLich aro abeady well adaoted by the structure 
of their flowers for cross-fertilisanon by the aid of 
inaecta often possess an irregular corolla, which has 
been modelled in relation to their visits ; and it would 
have been of little or no use to such plants to have 
become heterostyled. We can thus understand why 
it 13 that not a single species is heterostyled in such 
great families as the Legmniuosre, Labiata;, Scrophu- 
lariaccfe, Orehiden?, &c., all of which have irregular 
flowers. Every known heterostyled plant, however, 
depends on insects for its fertilisation, and not on the 
wind ; bo that it is a rather surprising fact that only 
one genua, Pontederia, has a plainly irregular corolla. 
Why some species are adapted for cross-fertilisation, 
whilst others within the same genus are not so, or 
if they once were, have since lost such adaptation 
and in consequeuce are now usually sclf-fertiliaed, I 
have endeavoured elsewhere to explain to a certain 
lijnited extent." If it be further asked why some 
species have been adapted for this end by being made 
heterostyled, rather than by any of the above specified 
means, the answer probably lies in the manner in 
which heterostylism originated, — a subject immedi- 
ately to be discussed. Heterostyled species, however, 
have an advantage over dichogamous species, as all 
the flowers on the same heterostyled plant belong to 
the same form, so that when fertilised legitimately by 
insects two distinct individuals are sure to intercross. 
On the other hand, with dichogamous plants, early or 
late flowers on the same individual may intercross ; 
and a cross of this kind does hardly any or no good. 
Whenever it is profitable to a species to produce a 



'71w Efibcta of OruH itnd Self-forlilisatioD,' 1 



J. p. ML 




260 



CONCLUDING BEMABKB 



large number of seeja and this obviously is a very 
common case, heterostyled will have an advantage 
over dicecious plants, as all the individuals of the 
former, whilst only half of the latter, that is the 
femalea, yield seeds. On the other hand, hctero- 
styled plants seem to have no advantage, as far as 
or OSS-fertilisation is concerned, over those which are 
sterile with their own pollen. They lie indeed under 
a slight disadvantage, for if two self-sterile plants 
grow near together and far removed from all other 
plants of the same species, they will mutually and 
perfectly fertilise one another, whilst this will not be 
the case with heterostyled dimorphic plants, unless 
they chance to belong to opposite forms- 
It may be added that species which are trimorphic 
Dave one slight advantage over the dimorphic ; for if 
only two individuals of a dimorphic species happen 
to grow near together in an isolated spot, the chances 
are even that both will belong to the same form, and 
in this ease they will not produce the full number of 
vigorous and fertile seedlings; all these, moreover, 
will tend strongly to belong to the same form as their 
parents. On the other hand, if two plants of the same 
tiimorphic species happen to grow in an isolated spot, 
the chances are two to one in favour of their not be- 
longing to the same form ; and in this case they wUl 
legitimately fertilise one another, and yield the full 
complement of vigorous offspring. 



Tlie Means h 



which Plants may ha 
Eeterosiyled. 



■e Veen rendered 



This is a very obscure subject, on which I can t 
little light, but which is worthy of discussion. It I 



ON hetehosttled plants. 



261 



been shown tliat heterostyled plants occur in fourteen 
natural families, dispersed throughout the whole vege- 
table kingdom, and that even within the family of the 
Bubiaceie they are dispersed in eight of the tribes. We 
may therefore conclude that this structure has been 
ftcc[uired by various plants independently of inheritance 
from a common progenitor, and that it can be acquired 
without any great difBeulty — that is, without any very 
anusual combination of circumstances- 
It is probable that the first step towards a species 
becoming heterostyled is great variability in the length 
of the pistil and stamens, or of the pistil alone. Such 
variations are not very rare : with Amsinckia spectahilis 
and Nolana proslraia these organs differ so much in 
length in diffureut individuals that, until experiment- 
ing on them, I thought both species heterostyled. 
The stigma of Gesneriu petiduUna sometimes protrudes 
far beyond, and is sometimes seated beneath the 
anthers; so it is with Oxalis acdosella and various 
other plants. I have also noticed an extraordinary 
amount of difference in the length of the pistil in cul- 
tivated varieties of Primula verts and vulgaris. 

As most plants are at least occasionally cross-fer- 
tilised by the aid of insects, we may assume that this 
waa the case with our supposed varying plant ; but 
that it would have betin beneficial to it to have been 
more regularly cross-fertilised. We should bear in 
mind how important an advantage it has been 
proved to be to many plants, though in different 
degrees and ways, to be cross-fertilised. It migb. 
well happen that our supposed species did not vary 
in function in the right manner, so" as to become 
either dichogamous or completely self-sterile, or in 
Btructute so as to ensure cross-fertilisation. If it had 



I 




262 CONCLUDING BEUAKKS 

thus yaried, it would never havo been rendered hctero' 
styled, aa this stute would then have beon superfluous. 
But the parent-species of our several existing hetero- 
styled plants may have been, and probably were (ju<' 
ing from their present constitution) in some degi 
self-sterile ; and this would have made regular en 
fertilisation still more desirable. 

Now let us take a highly varying species with most 
or all of the anthers exacrted in some individuals, and 
in others seated low duwn in the corolla ; with the 
stigma also varying in position in like manner. Insects 
which Tisited such flowers would have different parts 
of their bodies dusted with pollen, and it would be a 
mere chance whether this were left on the stigma of 
the next flower which was visited. If all the anthers 
could have been placed on the same level in all the 
plants, then abundant pollen would have adhered to 
the same part of the body of the insects which fre- 
quented the flowers, and would afterwards have been 
deposited without loss on the stigma, if it likewise 
stood on the same unvarying level in all the flowers. 
But as the stamens and pistils are supposed to have 
already varied much in length and to he still varying, 
it might well happen that they could be reduced much 
more easily through natural selection into two sets of 
different lengths in different individualsj than all to 
the same length and level in all the individuals. We 
know, from innumerable instances, in which the two 
sexes and the young of the same species differ, that 
there is no difiiculty in two or more sets of individuals 
being formed which inherit different characters. In 
our particular case the law of compensation or balanoe- 
ment (which is admitted by many botanists) would 
tend to cause the pistil to be reduced in those in<" 



ero- 



ON HETEROSTYLED PLANTS. 



263 



I Tiduals in which the stamens were greatly developed, 
I and to be increased in length in those which hud their 
stamens but little developed, 

Now if in our varying species the longer stamens 
were to be nearly equalised in length in a considerable 
body of individuals, with the pistil more or less reduced ; 
and ill another body, the shorter stamens to be simi- 
larly equalised, with the pistil more or less increased in 
length, cross-fertilisation would be secured with little 
loss of pollen; and this change would be so highly 
beneficial to the species, that there is no difficulty in be- 
lieving that it could be effected through natural selec- 
tion. Our plant would then make a close approach in 
etructure to a heteroatyled dimorphic species ; or to a 
trimorphio species, if the stamena were reduced to two 
lengths in the same flower in correspondence with that 
of the pistils in the other two forms. But we have not 
as yet even touched on the chief difficulty in under- 
standing how heteroatyled species could have origi- 
nated, A completely self-sterile plant or a dicho- 
gamous one can fertilise and be fertilised by any 
other individual of the same species; whereas the 
essential character of a heterostyled plant is that an 
individual of one form cannot fully fertilise or be fer- 
tilised by an individual of the same form, but only 
by one belonging to another form. 

H. Miiller has suggested* that ordinary or homo- 
styled plants may have been rendered heterostyled 
merely through the effects of habit. Whenever pollen 
from one set of anthers is habitually applied to a pistil 
of particular length in a varying species, he believes 
tt at last the possibility of fertilisation in any other 



' Die BeCrucUtunK der DlumBO,' p. Ul. 



2ti4 COSCLUDINQ BEMARSS < 

manner will be nearly or completely lost, 
led to this view by observing that Diptera frequently 
carried poileu from the long-styled flowers of Hottonia 
to the stigma of the same form, and that this ille- 
gitimate vmioQ was not nearly so sterile aa the corre- 
sponding union in other heterostyled speciea. But 
this conclusion is directly opposed by some other 
cases, for instance by that of Linum grandifioram ; 
for here the long-styled form ia utterly barren with 
its own-form pollen, although from the position 
of the anthers this pollen ia invariably applied to 
the stigma. It is obvious that with heterostyled 
dimorphic plants the two female and the two male 
organs differ in power ; for if the same kind of pollen 
be placed on the stigmas of the two forms, and again 
if the two kinds of pollen be placed on the stigmas of 
the same form, the results are in each case widely dif- 
ferent. Nor can we see how this differentiation of the 
two female and two male organs could have been 
effected merely through each kind of pollen being. 
habitually placed on one of the two stigmas. ■ 

Another view seems at first sight probable, namely, 
that an incapacity to be fertilised in certain ways haa 
been specially acquired by heterostyled plants. We 
may suppose that our varying species was somewhat 
sterile (as is often the case) with pollen from its own 
stamens, whether these were long or short ; and that 
such sterility was transferred to all the individuals 
with pistils and stamens of the same length, so that 
these became incapable of intercrossing freely ; but 
that such sterility was eliminated in the case of the 
individuals which differed in the length of their pistils 
and stamens. It is, however, incredible that so peculiar 
B form of mutual infertility should have been specially 



Ubaf. VL 



ON HETEHOSTYLED PLANTS. 



265 



acquired unless it were highly beneficial to the Bpecies : 
and although it may be beneficial to an individual 
plant to be sterile with its own pollen, cross -fertiliaa- 
tion being thus ensured, how can it be any advan- 
tage to a plant to be sterile with half its brethren, 
that is, with all the individuals belonging to the 
same form ? Moreover, if the sterility of the unions 
between plants of the same form had been a special 
acquirement, we might have expected that the long- 
Btyled form fertilised by the long-styled would have 
been sterile in the same degree as the shortrstyled 
fertilised by the short-styled ; but this is hardly ever 
the case. On the contrary, there is sometimes the 
widest difference in this respect, as between the two 
illegitimate unions of Pidmoaaria angvstifolia and of 
Bottonia palustris. 

It is a more probable view that the male and female 
organs in two sets of individuals have been by some 
means specially adapted for reciprocal action ; and 
that the sterility between the individuals of the same 
set or form is an incidental and purposeless result. 
The meaning of the term " incidental " may be illus- 
trated by the greater or less difficulty in grafting or 
budding together two plants belonging to distinct 
species ; for as this capacity is quite immaterial to the 
welfare of either, it cannot have been specially ac- 
quired, and must be the incidental result of differ- 
ences in their vegetative systems. But how the 
sexual elements of heterostyled plants came to differ 
from what they were whilst the species was homo- 
styled, and how they became co-adapted in two sets of 
individuals, are very obscure points. We know that 
in the two forms of our existing heterostyled plants 
the pistil always differs, and the stamens generally 
diffuT in length; so does the stigma in structure, 



266 



CONCLUDIKG EEMABES 



the anthers in size, and the polIen-graiiiB in diameter. 
It appears, thfrefore, at first sight probable that 
organs which differ in auch important respects could 
act on one another only in some manner for which 
they had been specially adapted. The probability of 
this riew is supported by the curious rule that the 
greater the difference in length between the pistils 
and stamens of the trimorphic species of Lythrum and 
Ozalis, the products of which are united for reproduc- 
tion, by so much the greater is the infertility of the 
union. The same rule applies to the two illegitimate 
unions of some dimorphic species, namely. Primula 
vulgaris and FidmojMria angustifolia ; but it entirely 
fails in other cases, as with Rottonia palustrig and 
Linvm grandijlorum. We shall, however, best perceive 
the difficulty of understanding the nature and origin 
of the co-adaptation between the reproductive organs 
of the two forms of heterostyled plants, by consider- 
ing the case of lAnum ffrandijlorum : the two forms of 
this plant differ exclusively, as far as we can see, in 
the length of their pistils ; in the long-styled form, 
the stamens equal the pistil in length, but their 
pollen has no more effect on it than so much in- 
organic dust; whilst this pollen fully fertilises the 
short pistil of the other form. Now, it is scarcely 
credible that a mere difference in the length of the 
pistil can make a wide difference in its capacity for 
being fertilised. We can believe this the less because 
with some plants, for instance, Amainckia speciabilis, 
the pistil varies greatly in length without affecting 
the fertility of the individuals which are intercrossed. 
Ho again I observed that the same plants of Primvla 
verts and wigaris differed to an extraordinary degree 
in the length of their pistils during successive seasons ; 
Qevertheless tlicy yielded during these seasons exactly 



on HETEBOSTYLED PI,ANT8. 



267 



I 



th.e same average number of seeda wlien left to fertilise 
themselves spontaneously under a net. 

We must therefore look to the appearance of inner 
or hidden constitutional differences between the indi- 
viduals of a varying species, of such a nature that the 
male element of one set is enabled to act efficiently 
only on the female element of another set. We need 
not doubt about the possibility of variations in tho 
constitution of the reproductive system of a plant, for 
we know that some species vary so as to be completely 
aelf-sterile or completely self-fertile, either in an appa- 
rently spontaneous manner or from slightly changed 
conditions of life. Gartner also has shown" that the in- 
dividual plants of the same species vary in their sexual 
powers in such a manner that one will nnite with a 
distinct species much more readily than another. But 
what the nature of the inner constitutional differences 
may be between the sets or forma of the same varying 
species, or between distinct species, is quite unknown. 
It seems therefore probable that the species which 
hiive become heterostyled at first varied so that two 
or three sets of individuals were formed differing in 
the length of their pistils and stamens and in other 
co-adapted characters, and that almost simultaneously 
their reproductive powers became modified in such a 
manner that the sexual elements in one set were 
adapted to act on the sexual elements of another set ; 
and consequently that these elements in the same set 
or form incidentally became ill-adapted for mutual 
interaction, as in the case of distinct species. I have 
elsewliere shown f that the sterility of species when 



■ Gailner, ' BiiBlarderzBugnQg Plnnla under DomestioatioQ,' 2iid 

Im Pii-innnrBioh,' liM'J, p. Iti5. edit. vol. ii. p. li;9; -Tbe Effectaor 

t -Onpa of Sprites,' tHlioilit CpaB!iHiid8elf-rHiti]iBatiuD,'p.4e3. 

|lk SIT :' Variation of AuimulHiiiid II may be weU bare to reioaik 



268 C0NCi,UDrNG 

first crossed and of tlieir hybrid offspring nrnst alao ' 
be looked at as merely an incidental result, following 
from the special oo-adaptation of the sexual elements 
of the same species. We can thus understand the 
striking parallelism, which has been shown to exist 
between the effects of illegitimately uniting hetero- 
styled plants and of crossing distinct species. The 
great difference in the degree of sterility between the i 
various heterostyled species when illegitimately fer* 
tilised, and between the two forms of the same species 
when similarly fertilised, harmonises well with the 
view that the result is an incidental one which follows 
from changes gradually effected in their reproductiye 
systems, in order that the sexual elements of the dis- 
tinct forma should act perfectly on one another. 

Transmiasion of the Two Forms fcy Seterostyled Plants. 
— The transmission of the two forms by heterostyled 
plants, with respect to which many facts were given in 
the last chapter, may perhaps be found hereafter to 
throw some light on their manner of development, 
Hildebrand observed that seedlings from the long- 
styled form of Primula Sinensis when fertilised with 
pollen from the same form were mostly long-styled, 
and many analogous cases have since been observed 
by me. All the known cases are given in the two 
following tables. 



that, jnilging &om tha remrttb- 
abls power vitli vhicb abruptly 
ohnngL'd conditions of life e.ot uq 
the reprodnctive Bj'Bti^m of moat 
orgnnidms, it u probable that tiie 
Dlutie a>lnptatiuD of (he nalt.' tu the 



female elemenla in the two torma vf 
tlie same heteroRtjted spraiu, or 
in all (be individuals of the same 
ordinajy specif 8, conld be v^nired 
oqI; under long^continued nearlj 
.unilbnn oonditiona of life. 



4 
4 

4 



^M CifAP. VI. ON HETEROSTYLED PLANTS. 


2G9 ^M 


Table 3C. 




■ 


Kalwe of the Oppring from Ilkgilim'ttely feHilised DimorpJ.io ^^M 
Plants. ^H 


— 


H 


Off»prlat 


IjiEg-styled form, furtilisad by 
p . 1 , QwD-form polkQ during five 

duosd 


156 


6 


(Short-styled form, fcrtilised bj' 
" '■ ' '\ own-form pollen, produced . , 


5 


6 


Long-styled form, fertilwed by 






duced 


69 





Sliort-Btyled form, rertili.wd br 

own-form polUn, 1b Bnld to 

Primula BuricuU .J prodace dnrlng soccesBiTE 

generntioos oftapring in about 

ths tbllowicg pruportians . 


25 


75 


Long-fltyled form, fertilised by 

PrimuUSineusl. . . ^""/X '^ealtn"^ ^^ 
pucce$sLve generations, pro- 
duced 


sa 





(LoDij-atyled form, fertilised by 

„ . . own-form pollen (Hilde- 

1 bnndj, produced. . . .| 


14 


3 


" ■ 'X own-formpollen, produced J 


1 


2* 


p.w..„. .»...«-.f :;:s X'pS'^t^'O 


" 


» 


-''>»- »-rH'"sKX'"Si'';) 


45 


1 


fShort-styied fiirin, fertilised }>j\ 
" " \ own-form pollen, produced .J 


13 


20 


1 d 



■ 270 


CONCLUDCvQ QE&IARES Chap. ^^H 


■ 


Taslb ^^^H 


^V Ifatunofthe 




■ 


PlanU. 


^1 




KliBbet 


NomhEr NombBT 






ctLoQg- 


of MM- 


of Short- 


H 




CUbprtig. 


Kfiei 


o^X^ 


B 


jLong>«tyled fann, ferlilEsed, 








^1 I.Tliiniiii ulicflria 


j hj own-fonn pollen, pro- 
ISbort-stjled rorm, fmaiwli 


56 





'■ 


■ 


j hj- own-ftrn, pollen, pro- 
5horl-<tjled fVirm, fcrLilise^l] 


I 





1 




by pollen from mid-leagll! | 






8 ^H 


1 


Btameaa of Inag - styled 
foTiD, produced , . .] 






■ 


^H 


/Mid^tjledforin.fcrtili-ed bj| 






°l 


^H 


\ own-form pollen, produced /i 




^1 


Mid-styled form, fertilised hy 












°l 




men- of long-styled form. 1 " 




^H 


Pfo^""!! J 






^H , 


/Mid-«tjlBd form, fenili^ea Ly 




^^1 




1 polUa from longeaC eta- ,, 


3 


"I 




j mens of sborl-stjled form, '* 


^M 


( P'oducad j 






H 


Long-styled form, fertili^^i! 




H 


^1 Omhi r<,Ma . 


by own-form pollen, pro- ■ 
doced otfepriog in the 
ratio of ..... 


100 





°l 


H „ Itdj^rolda 


(Miri-i^tylea form, fertilised byl 
\ own-foim pollen, prodneed/ 





IT 


J 


L 1 



Chap. VL ON HETEEOSTYLED PLANTS. 



271 



We see in these two tables tbat the offspring from 
A form illegitimately fertilised with pollen from 
another plant of the same form belong, with a few 
exceptions, to the same form as their parents. For 
instance, out of 162 seedlings from long-styled plants 
of Primula verts fertilised during five generations in 
this manner, 156 were long-styled and only 6 short- 
Btyled. Of 69 seedlings from P. vulgaris similarly 
raised all were long-atyled. So it was with 56 seedlings 
from the long-styled form of the trimorpnic lA/thrum 
scdicaria, and with numerous seedlings from the long- 
styled form of Oxalis rosea. The offspring from the 
short-styled forma of dimorphic plants, and from both 
the mid-styled and short-atyled forms of trimorphic 
plants, fertilised with their own-form pollen, likewise 
tend to belong to the same form as their parents, but 
not in so marked a manner as in the case of the long- 
styled form. There are three cases in Table 37, in 
which a form of Lythriim was fertilised illegitimately 
with pollen from another form; and in two of these 
cases all the offspring belonged to the same two forms 
as their parents, whilst in the third case they belonged 
to all three forms. 

The cases hitherto given relate to illegitimate unions, 
but Hildebrand, Fritz Miiller, and myself found that 
a very large proportion, or all of the offspring, from a 
legitimate union between any two forms of the tri- 
morphic species of Oxalis belonged to the same two 
forms. A similar rule therefora holds good with unions 
which are fully fertile, as with those of an illegiti- 
mate nature which are more or less sterile. When 
some of the seedlings from a beterostyled plant belong 
to a different form from that of its parents, Hildebrand 
accounts for the fact by reversion. For instance, the 
long-styled parent-plant of Primula verts, from which 



272 



CONCLUDING BEMABKS 



Caip. 1 



the 162 illegitimate seedlings in Table 36 were derived J 
in the course of five generations, wa^ itself no douMl 
derived from the union of a long-styled and a short- ■ 
styled parent; and tho 6 short-styled seedlings may be 
attributed to reversion to their short-styled progeni- 
tor. But it is a surprising fact in this case, and in 
other similar ones, that the number of the offspring 
which thus reverted was not larger. The fact is ren- 
dered still more strange in the particular instance of 
P. verts, for there was no reversion until four or five 
generations of long-styled plants had been raised. It 
may be seen in both tables that the long-styled form 
transmits its form much more faithfully than does the 
short-styled, when both are fertilised with their own- 
form pollen ; and why this should be so it is difficult 
to conjecture, unless it be that the aboriginal parents 
form of most heterostyled species possessed a pistil 
which exceeded its o^ti stamens considerably in 
length." I will only add that in a state of nature 
any single plant of a trimorphic species no doubt pro- 
duces all three forms ; and this may be accounted for 
either by its several flowers being separately fettilised 
by both the other forms, as Hildebrand supposes; ori 
by pollen from both the other forms being deposited | 
by insects on the stigma of the same flower. 

Equal-styled varieties, — The tendency of the di- 
morphic species of Primula to produce equal-styled 
varieties deserves notice. Cases of this kind have 



* II inny be suapetied tlmt this 
TTM Ibe case with Primulii, jodg-- 
ing from the leiijilh or tbe pistil 
in Beveriil alli^ Keneia (aee 
Mr. J. Scott, ' JournRl Lini 



state of nature nilli eome floirert ' 
on tlie Bnme plant long-atjie-l, 
othcn eliort-s^liid nnd others 
eqoal-Btyled ; and the long-etjled 
fatal greiitly preponderated i 



Bot' vol. viii. IBfii, p. 851. .Hew namLer; thera being 61 of thii 



UreitfiitiDobroandi 






if Primid'i rfah'or growing i: 



if tlie ehori-atyled and 



r 



ON HETEROSTYLED PLANTS, 



273 

been observed, as shown in the last chapter, in no leas 
than six species, namely, P. veris, vvlgaria, Sinensii, 
auricula, farinosa, and datior. In the case of P. veris, 
the stamens resemble in length, position and size 
of their pollen-graina the stamena of the ahort-styled 
form; whilst the pistil closely resembles that'of the 
long-styled, but aa it varies much in length, one proper 
to the short-styled form appears to have been elongated 
and to have assumed at the same time the functions 
of a long-atyled pistil. Consequently the flowera are 
capable of spontaneous self-fertilisation of a legiti- 
mate nature and yield a full complement of seed, or 
even more than the niunber produced by ordinary 
flowers legitimately fertilised. With P. Sinensis, on 
the other hand, the stamens resemble in all respects 
the shorter ones proper to the long-styled form, whilst 
the pistil makes a near approach to that of the ahort- 
styled, but as it varies in length, it would appear as 
if a long-styled pistil had been reduced in length and 
modified in function. The flowers in this case aa in 
the last are capable of spontaneous legitimate ferti- 
lisation, and are rather more productive than ordinary 
flowers legitimately fertilised. With P. aurmda and 
farinosa the stamens resemble those of the short-styled 
form in length, but those of the long-styled in the 
size of their pollen-grains ; the pistil also resembles that 
of the long-styled, so that although the stamens and 
pistil are of nearly equal length, and consequently 
pollen is spontaneously deposited on the stigma, yet 
the flowers are not legitimately fertilised and yield 
only a very moderate supply of seed. We thus see, 
firstly, that equal-styled varieties have originated in 
various ways, and, secondly, that the combination of 
the two forms in the same flower differs in complete- 



274 



CONCLUDING BEHABES 



Chap. ^ 



ness. With P. elaitor some of the flowers on the Bam( 
plaut have become equal-fityled, instead of all 
them 03 in the other species. 

Mr. Scott has auggested that the equal-styled varie- 
ties arise through reversion to the former homostyled 
condition of the genua. This view is supported by 
tUe remarkable fidelity with which the equal-styled 
variation ia transmitted after it has once appeared. I 
have shown in Chupter XIII. of my 'Variation of 
Animals and I'lants under Domestication,' that any 
cause which disturbs the constitution tends to in- 
duce reversion, and it is chiefly the cultivated 
species of Primula which become equal-atyled. Ille- 
gitimate fertilisation, which ia an abnormal process, 
ia likewise an exciting cause ; and with illegitimately 
descended long-styled phints of P. Sinensis, I have 
observed the first appearance and subsequent stages 
of this variation. With some other plants of P. 8i- 
n-ensie of similar parentage the flowers appeared 
to have reverted to their original wild condition. 
Again, some hybrids between P. veris and vulgaris 
were strictly equal-styled, and others made a near 
approach to this structure. All these facts support 
the view that this variation results, at leaat in part, 
from reversion to the original state of the genus, 
before the species had become heterostyled. On the 
other hand, some considerations indicate, as previously 
remarked, that the aboriginal parent-form of Primula 
had a pistil which exceeded the ataraens in length. 
The fertility of the equal-styled varieties has been 
somewhat modified, being sometimes greater and some- 
times less than that of a legitimate union. Another 
view, however, may be taken with respect to the origin 
of the equal-styled varieties, and their appearanoe 



I 



may 



be compared with that of hermaphrodites amongi 



ciup. VI. ON hetebobtyijED plants. 



275 



animals which properly have their sexes separated; 
for the two sexes are combined in a monstrous her- 
maphrodite in a somewhat similar manner as the 
two sexuiil forms are combined in the same flower of 
an equal-atyleJ variety of a heterostyled species. 

Final remarks. — The existence of plants which have 
been rendered heterostyled is a highly remarkable 
phenomenon, as the two or three forms of the same 
undoubted species differ not only in important points 
of structure, but in the nature of their reproductive 
powers. As far as structure is concerned, the two 
sexes of many animals and of some plants differ to an 
extreme degree ; and in both kingdoms the same 
species may consist of males, females, and hermaphro- 
dites. Certain hermaphrodite cirripedes are aided in 
their reproduction by a whole cluster of what I have 
called complemental males, which differ wonderfully 
from the ordinary hermaphrodite form. With ants 
we have males and females, and two or three castes of 
sterile females or workers. With Termites there are, 
as Fritz Miiller has shown, both winged and wingless 
males and females, besides the workers. But ia none 
of these cases is there any reason to believe that the 
several males or several females of the same species 
differ in their sexual powers, except in the atrophied 
condition of the reproductive organs in the workers of 
social insects. Many hermaphrodite animals must 
unite for reproduction, but the necessity of such 
union apparently depends solely on their structure. 
On the other hand, with heterostyled dimorphic 
Npecies there are two females and two sets of males, 
and with trimorphic species three females and three 
seta of mules, which differ essentially in their sexual 



•JIG 



CONCLUDING RFWATtKH 



CUAF. TU 



powers. Wo shall, perhaps, best perceive the complea 

liiiil extraordjoary nature of the marriage arrangements 
of a trimorphic plant by the following illustration. 
Let ua suppose that the individuals of the same species 
of ant always lived in triple communities ; and that 
in one of these, a large-sized female (differing also in 
other characters) lived with six middle-sized and six 
small-sized males ; in the second community a middle- 
sized female lived with six large- and six small-sized 
males ; and in the third, a small-sized female lived 
with six large- and six middle-sized males. Each of 
these three females, though enabled to unite with any 
male, would be nearly sterile with her own two sets of 
males, and likewise with two other sets of males of the 
same size with her own which lived in the other two 
communities ; but she would be fully fertile when 
paired with a male of her own size. Hence the thirty- 
six males, distributed by half-dozens in the three com- 
munities, would be divided into three sets of a dozen 
each ; and these sets, as well as the three females, 
would differ from one another in their reproductive 
powers in exactly the same manner as do the distinct 
species of the same genus. But it is a still more 
remarkable fact that young ants raised from any one 
of the three female ants, illegitimately fertilised by a 
male of a different size would resemble in a whole 
series of relations the hybrid offspring from a cross 
between two distinct species of ants. They would be 
dwarfed in stature, and more or less, or even utterly 
barren, Naturalists are so much accustomed to behold 
great diversities of structure associated with the two 
sexes, that they feel no surprise at almost any amount 
of difference ; but differences in sexual nature have 
been thought to be the very touchstone of specific 
distinction. We now see that such sexual difference 



i 

i 
4 



Chap.vl on heterostyled plants. 277 

— ^the greater or less power of fertilising and being 
fertilised — may characterise the co-existing individuals 
of the same species, in the same manner as they 
characterise and have kept separate those groups of 
individuals, produced during the lapse of ages, which 
wo rank and denominate as distinct species. 



DltEClOUS ASD 



I 



CHAPTEE TIL 

PoLTOAHOCa, DllECIOUS, AMD 6TN0-t>IQ90I01TS Fl-AVn 

Tbe ooateiBJon in varioua nays of herni:iphn>dite into dtixcloUB pl«nlfl 
— Heloroatylad pLiutB rondureri diasoitiuB — KubfBi»ffi — VerbeiiBOea 
^PoljgwuouB and snb-di^Erious jjlaiita — Euodjidiu — Fragnrla— 
The two BuWromia nf tuth BOios of KtminnnB and EpigKO — Hei — 
tiyno-ditei'lDus plan te— Thy mDe, ditference in fertltity of the her- 
nutphioiliti: and female iudividuala — Satureia — MaoDer in whioh 
the two forma probably origiiiBted — Scubiosa tind otber gyuo- 
diracioua plants— Difft^rence in the aiia of the ooralla in tlie fomu 
of polygumouB, ditetious, and gyno-JicBdona plants. 

TuEKE are several groups of plants in wliicli all tbe 
species are dicecious, and these exhibit no rudimento 
in the one aes of the organs proper to the other. 
About the origin of such plants nothing is known. It 
is possible that they may be descended from ancient 
lowly organised forms, which had from the first their 
sexes separated ; so that they have never existed as 
hermaphrodites. There are, however, many other 
groups of species and single ones, which from being 
allied on all sides to hermaphrodites, and from ex- 
hibiting in the female flowers plain rudiments of 
male organs, and conversely in the male flowers rudi- 
ments of female organs, we may feel sure are descended 
from plants which formerly had the two sexes com- 
bined in the same flower. It is a cui-ious and obscure 
problem how and why such hermaphrodites have been 
rendered bisexual. 

If iu some individuals of a species the stazoeDgj 
alone were to abort, females and hermaphrodites would.l 



I Chap. VIL 



rOLYGAMOUS PLANTS. 



279 



^1 tio: 



be left existing, of wliich many instances occur ; and 
if the female organs of the hermaphroditewere after- 
wards to abort, the result would be a dicecious plant. 
Conversely, if we imagine the female organs alone to 
abort in some individuals, males and hermaphrodites 
would be left ; and the hermaphrodites might after- 
wards be converted into females. 

In other cases, aa in that of the common Ash-tree 
mentioned in the Introduction, the stamens are rudi- 
mentary in some individuals, the pistils in others, 
others again remaining as hermaphrodites. Here the 
modification of the two sets of organs appears to have 
occurred simultaneously, as far as we can judge from 
their equal state of abortion. If the hermaphrodites 
were supplanted by the individuals having separated 
96X68, and if these latter were equalised in number, a 
Btriotly dioecious species would be formed, 

There is much difBeulty in understanding why her- 
maphrodite plants should ever have been rendered 
dioecious. There would be no such conversion, unless 
pollen was already carried regularly by insects or by the 
wind from one individual to the other ; for otherwise 
every step towards diceciousness would lead towards 
sterility. As we must assume that cross-fertilisation 
was assured before an hermaphrodite could be changed 
into a dicecious plant, we may conclude that the con- 
version has not been effected for the sake of gaining 
the great benefits which follow from cross-fertilisa- 
tion. We can, however, see that if a species were 
Bubjected to unfavourable conditions from severe com- 
petition with other plants, or from any other cause, the 
production of the male and female elements and the 
maturation of the ovules by the same individual, might 
prove too great a strain on its powers, and the separa- 
tion of the sexes would then be highly beneficial. 



2S0 DKECIOUS ASD Cuif. 

This, liowGvor, would be effected only under the 
tingeney of a reduced number of seeds, produced by 
the females alone, being sufficient to keep up the 
stock. 

There is another way of looking at the subject which 
partially romoveB a difficulty that appears at first sight 
insuperable, namely, that during the conversion of an 
hermaphrodite into a dicecions plant, the male organs 
must abort in some individuals and the female organs 
in others. Yet aa all are exposed to the same con- 
ditious, it might have been expected that those 
which varied would tend to vary in the same man- 
ner. As a general rule only a few individuals of a 
species vary simultaneously in the same manner ; and 
there is no improbability in the assumption that 
some few individuals might produce larger seeds 
than the average, better stocked with nourishment. If 
the production of such seeds were highly beneficial to 
a species, and on this head there can be little doubt,* 
the variety with the large seeds would tend to in- 
crease. But in accordance with the law of compensa- 
tion we might expect that the individuals which prt)- 
duced such seeds would, if living under severe con- 
ditions, tend to produce less and less pollen, so that 
their anthers would be reduced in size and might ulti- 
mately become rudimentary. This view occurred to 
me owing to a statement by Sir J. E. Smith f that 
there are female and hermaphrodite plants of Serratvia 
tincioria, and that the seeds of the former are larger 
than those of the hermaphrodite form. It may also 
be worth while to recall the case of the mid-styled 
furm of Li/thrum mlicaria, which produces a larger 

t ' Trdofl. I,uin. Sou.,' vol xiil 



ClFAP. VIL 



POLYGAMOUS PLANTS 



281 



number of aeeds than the other fonns, and has some- 
what smaller pollen-grains which have less fertilising 
power than those of the corresponding stamens in the 
other two forms; but whether the larger number of 
seeds is the indirect cause of the diminished power 
of tlie pollen, or vice veisd, I know not. As soon 
as the anthers in a certain number of individuals be- 
came reduced in size in the manner just suggested or 
from any other cause, the other individuals would have 
to produce a larger supply of pollen ; and such in- 
creased development would tend to reduce the female 
organs through the law of compensation, so as ulti- 
mately to leave them in a rudimentary condition ; 
and the species would then become dicecious. 

Instead of the first change occurring in the femalo 
organs we may suppose that the male ones first varied, 
BO that some individuals produced a larger supply of 
pollen. This would be beneficial under certain cir- 
cumstances, such as a change in the nature of the 
insects which visited the flowers, or in their be- 
coming more anemophilous, for such plants require an 
enormous quantity of pollen. The increased action of 
the male organs would tend to affect through compen- 
sation the female organs of the same flower ; and the 
final result would be that the species would consist of 
males and hermaphrodites. But it is of no use con- 
sidering this case and other analogous ones, for, as 
stated in the Introduction, the co-existence of male 
and hermaphrodite plants is excessively rare. 

It is no valid objection to the foregoing views that 
changes of such a nature would be eS'ected with ex- 
treme slowness, for we shall presently see good reason 
to believe that various hermaphrodite plants have 
become or are becoming dicecious by many and ex- 
cessively small steps. In the case of polygamous 



L 



282 DKECIOIIS AND Chap. VI 

species, which exist aa males, females and hermaphrc 
(lites, the latter would have to be supplanted before 
the species could become strictly dioecioiis ; but the 
extinction of the hermaphrodite form would probably 
nut be difScult, aa a complete separation of the sexes 
appears often to be in some way beneficial. The males 
and females would also have to be equalised in 
number, or produced in some fitting proportion for the 
effectual fertilisation of the females. 

There are, no doubt, many unknown laws which 
govern the suppression of the male or female organs 
in hermaphrodite plants, quite independently of any 
tendency in them to become monoacious, dicecious, or 
polygamous. We see this in those hermaphrodites 
which from the rudiments still present manifestly 
once possessed more stamens or pistils than they 
now do, — even twice as many, aa a whole verticil has 
often been suppressed. Robert Brown remarks* that 
" the order of reduction or abortion of the stamina 
in any natural family may with some confidence be 
predicted," by observing in other members of the 
family, in which thoir number is complete, the oi'der 
of the dehiscence of the anthers ; for the lesser per- 
manence of an organ is generally connected with its 
lesser perfection, and he judges of perfection by 
priority of development. He also states that when- 
ever there is a separation of the sexes in an her- 
maphrodite plant, which bears flowers on a simple 
spike, it is the females which expand first ; and this 
he likewise attributes to the female sex being the 
more perfect of the two, but why the female should 
be thus valued he does not explain. 



a. Linn. 800.' vol. lii. p. 08. Ot ' MiaoellaQMnia Worfc^' vdl 



1 



POLYQAMOUB PLANTS. 



283 



Plants under cultivation or changed conditions of 
life frequently become sterile ; and the male organs 
are mucli oftener affected than the female, thougli the 
latter alone are sometimes affected. The sterility of 
the stamens is generally accompanied by a reduction 
in their size ; and we may feel sure, from a wide-spread 
analogy, that both the male and female organs would 
become rudimentary in the course of many genera- 
tions if they failed altogether to perform their proper 
functions. According to Gartner,* if the anthers on 
a plant are contabescent (and when thia occurs it is 
always at a very early period of growth) the female 
organs are sometimes precociously developed. I 
mention this case as it appears to be one of com- 
pensation. So again is the well-known fact, that 
plants which increase largely by stolons or other such 
means are often utterly barren, with a large proportion 
of their poUen-graina in a worthless condition. 

Hildebrand has shown that with hermaphrodite 
plants which are strongly proterandrous, the stamens 
in the flowers which open first sometimes abort ; and 
this seems to follow from their being useless, as no 
pistils are then ready to be fertilised. Conversely 
the pistils in the flowers which open last sometimes 
abort; as when they are ready for fertilisation all the 
pollen has been shed. He further shows by means of 
a series of gradations amongst the CompositaJ,! that 
a tendency from the causes just specified to produce 
either male or female florets, sometimes spreads 
to all the florets on the same head, and sometimes 



,. H auw.ot 

of tho Btorilitj of plants from 
[■a hns bei n Jiscuased 



chnp. iviii. — 2Dd edit vol. ii. 
pp. HS-Sa, 

t ' Ilebcr die OeBChlei:lila¥er' 
Mltoisse bei den Coinpoulen,' 
latiS, p. 89. 



284 DHECIOUS A>"0 Chap. VII 

even to the whole plant ; and in this Inttcr case the 
species becomes dioecious. In those rare instances men- 
tioned in the Introduction, in which some of the indi- 
viduals of both moncecious and hermaphrodite plants 
are proterandrous, others being proterogynous, their 
conversion into a dioecious condition would probably be 
much facilitated, as they already consist of two bodies 
of individuals, differing to a certain extent in their 
reproductive functions. 

Dimorphic heterostyled plants offer still more 
strongly marked facilities for becoming dicecioua ; for 
they likewise consist of two bodies of individuals in 
approximately equal numbers, and what probably ia 
more important, both the male and female organs 
differ in the two forms, not only in structure but in 
function, in nearly the same manner as do the repro- 
ductive organs of two distinct species belonging to 
the same genus. Now if two species are subjected to 
changed conditions, though of the same nature, it is 
notorious that they are often affected very differently ; 
therefore the male organs, for instance, in one form of 
a heterostyled plant might be affected by those un- 
known causes which induce abortion, differently from 
the homologous but functionally different organs in 
the other form ; and so conversely with the female 
organs. Thus the great dilficulty before alluded to is 
much lessened in understanding how any cause what- 
eyer could lead to the simultaneous reduction and 
ultimate suppression of the male organs in half the 
individuals of a species, and of the female organs in 
the other half, whilst all were subjected to exactly the 
same conditions of life. 

That such reduction or suppression has occurred 
in some heterostyled plants is almost certain. The 
Uubiacete contain more heterostyled genera than any 



POLYGAMOUS PLANTS. 



'285 



otiier family, and from tlieir wide distribution we may- 
infer tliat many of them became beterostyled at a re- 
mote period, 80 that there will have been ample time for 
some of the speciea to have been since rendered di(»- 
cious. Asa Gray informs me that Coproama is dioecious, 
and tliat it is closely allied through Nertera to Mitch* 
ella, which as we know is a heteroatyled dimorphic 
species. In the male flowers of Coprosma the stamens 
are exserted, and in the female flowers the stigmas ; 
80 that, judging from the affinities of the above three 
genera, it seems probable that an ancient short^styled 
form bearing long stamens with large anthers and 
large pollen-grains (as in the case of several Eubia- 
ceous genera) has been converted into the male Co- 
proama; and that an ancient long-styled form with short 
stamens, small anthers and small pollen-grains has 
been converted into the female form. But according 
to Mr, Meehan," Mitchella itself is dioecioua in some 
districts ; for he says that one form has small sessile 
anthers without a trace of pollen, the pistil being 
perfect; while in another form the stamens are perfect 
and the pistil rudimentary. He adds that plants 
may be observed in the autumn bearing an abundant 
crop of berries, and others without a single one. 
Should these statements bo confirmed, Mitchella will 
be proved to be beterostyled in one district and 
diiBcious in another. 

Asperula is iikewiae a Eubiaceous genua, and from 
the published description of the two forms of A. seo- 
paria, an inhabitant of Tasmania, I did not doubt that 
it waa heteroatyled ; but on examining some flowers 
Bent me by Dr. Hooker they proved to be dicecious. 
The male flowers have large anthers and a very small 



L 



Froo. A<.'1k!, of Sclenoee ot PhUodelphiB.' Jul; 29, II 



i, p. 183, 



288 DICECIOUS AND Chap. VII, 

ovarium, surmounted by a mere vestige of a stigma 
without any style ; B'liilst the female flowers possess 
a large ovarium, the nntkera being rudimentary and 
apparently quite destitute of pollen. Considering 
how many Kubiaceous genera are heterostyled, it is a 
reasonable suspicion that this Asperula is descended 
from a hetfirostyled progenitor ; but wa should be 
cautious on this head, for there is no improbability in 
a homostyled Eubiaceou8 plant becoming dicecious. 
Moreover, in an allied plant, Galium eruciatum, the 
female organs have been suppressed in most of the 
lower flowers, whilst the upper ones remain hermaph- 
rodite ; and here we have a modification of the sexual 
organs without any connection with heterostylism. 

Mr. Thwaites informs me that in Ceylon various 
Eubiaceous plants are heterostyled ; but in the casa 
of Discospermum one of the two forms is always 
barren, the ovary containing about two aborted ovules 
in each loculua ; whilst in the other form each loculus 
contains several perfect ovules ; so that the species 
appears to be strictly dicecious. 

Most of the species of the South American genua 
.^giphila, a member of the Verbenaceffi, apparently 
are heterostyled ; and both Fritz Muller and myself 
thought that this was the case with ^. dbdurata, so 
closely did its flowers resemble those of the heterostyled 
species. But on examining the flowers, the anthers of 
the long-styled form were found to be entirely desti- 
tute of pollen and less than half the size of those in 
the other form, the pistil being perfectly developed. 
On the other hand, in the shorl^styled form the stig- 
mas are reduced to half their proper length, having 
also an abnormal appearance ; whilst the stamens are 
perfect. This plant therefore is dioecious ; and wo 
may, I think, conclude that a short-styled progenitor. 



POLYGAMOUS PLANTS, 



287 



bearing long staraena exaerted beyond the corolla, 
baa been converted into the male; and a long-styled 
progenitor witb fully developed stigmas into the fe- 
male. 

From the number of bad pollen-grainB in the small 
anthers of the short stamens of the long-styled form 
of Pvimonaria angustifolia, we may suspect that this 
form is tending to become female; but it does not 
appear that the other or short-styled form is becoming 
more masculine. Certain appearances countenance 
the belief that the reproductive system of PMox svhu- 
lata is likewise undergoing a change of some kind. 

I have now given the few cases known to me in 
which heterostyled plants appear with some consider- 
able degree of probability to have been rendered 
dicecious. Nor ought we to expect to find many such 
cases, for the number of heterostyled species is by no 
means large, at least in Europe, where they could 
hardly have escaped notice. Therefore the number of 
dicecious species which owe their origin to the trans- 
formation of heterostyled plants is probably not so 
large as might have been anticipated from the facilities 
which they ofifer for such conversion. 

In searching for cases like the foregoing ones, I have 
been led to examine some dicecious or sub-dioecious 
plants, which are worth describing, chiefly ae they 
show by what fine gradations hermaphrodites may 
pass into polygamous or dicecious species. 



PolygamouB, Viaeeious and Svh-duBcious Plants. 

FAionymua 'Biiropxus (Celaatrineie). — The spindle-tree 
is described in all the botanical works which I have 
consulted as an hermaphrodite. Asa Gray speaks of 
the flowers of the American species as perfect, whilst 



288 DICECIOUB AND Ciup. VU 

ihoee in the allied genus Celostms are said to be 
" polygamo-diascioTis." If a number of bushes of our 
Bpindle-tree be examined, about half will be found to 
have stamens equal in length to the pistil, vrith well- 
developed anthers; the pistil being likewise to all 
appearance well developed. The other half have a 
perfect pistil, with the stamens short, bearing rudi- 
mentary anthers destitute of pollen; so that these 
bushes are females. All the flowers on the same plant 
present the same structure. The female corolla is 
smaller than that on the poUenifenma bushes. The 
two forms are shown in the accompanying drawings. 



rig. 13. 




Hermaiihrodlti! or male. FemaU. 

Euosyncs ZutiapxTm. 

1 did not at first doubt that this species existed 
under an hermaphrodite and female form ; but we shall 
presently see that some of the bushes which appear 
10 be hermaphrodites never produce fruit, and these 
are in fact males. The species, therefore, is poly- 
gamous in the sense in which I use the term, and tri- 
oicous. The flowers are frequented by many Diptera 
and some small Hymenoptera for the sake of the 
nectar secreted by the disc, but I did not see a single 
bee at work ; nevertheless the other insects sufficed to 



FOLTGAMOUS PLANTS. 



289 



fertilise effectually female bushes growing at a dia- 
tunce of even 30 yards &oni any polleniferoua bush. 

TliQ email anthers borne by the short stamens of 
the female flowers are well formed and dehisce pro- 
perly, but I could never find in them a single grain 
of pollen. It is somewhat difficult to compare the 
length of the pistils in the two forms, as they vary 
somewhat in this respect and continue to grow after 
the anthers are mature. The pistils, therefore, in old 
flowers on a polleniferous plant are often of consider- 
ably greater length than in young flowers on a female 
plant. On this account the pistils from five flowers 
from so many hermaphrodite or male bushes were 
compared with those fi-om five female bushes, before 
the anthers had dehisced and whilst the rudimentary 
ones were of a pink colour and not at all shrivelled. 
These two sets of pistils did not differ in length, or if 
there was any difference those of the polleniferous 
flowers wore rather the longest. In one hermaphrodite 
plant, which produced during three years very few 
and poor fruit, the pistil much exceeded in length 
the stamens bearing perfect and as yet closed an- 
thers ; and I never saw such a case on any female 
plant. It is a surprising fact that the pistil in the 
male and in the semi-sterile hermaphrodite flowers 
has not been reduced in length, seeing that it per- 
forms very poorly or not at all its proper function. 
The stigmas in the two forma are exactly alike ; and 
in some of the polleniferous plants which never pro- 
duced any fruit I found that the surface of the stigma 
was viscid, ho that pollen-grains adhered to it and had 
exserted their tubes. The ovules are of equal size 
in the two forms. Therefore the most acute botanist, 
judging only by atmcture, would never have auspectetj 



I 



290 DICECIOUS AND Cii*p. VII 

that some of the bushes were in fanction exclusively 
males. 

Thirteen bnahea growing near one another in a 
hedge consisted of eight females quite destitute of 
pollen and of five hormaplirodites with well-developed 
anthers. la the autumn the eight females were well 
covered with fruit, excepting one, which bore only a 
moderate number. Of the five hermaphrodites, one 
bore a dozen or two fruits, and the remaining four 
bushes several dozen ; but their number was as nothing 
compared with those on the female bushes, for a single 
branch, between two and three feet in length, from 
one of the latter, yielded more than any one of the 
hermaphrodite bushes. The difference in the amount 
of fruit produced by the two sets of bushoe is all the 
more striking, as from the sketches above given it is 
obvious that the stigmas of the poUeniferous flowers 
can hardly fail to receive their own pollen ; whilst the 
fertilisation of the female flowers depends on pollea 
being brought to them by flies and the smaller 
Hymenoptera, which are far from being such efficient 
carriers as bees. 

I now determined to observe more carefully daring 
successive seasons some bushes growing in another 
place about a mile distant. As the female bushes 
were so highly productive, I marked only two of them 
with the letters A and B, and five poUeniferous bushes 
with the letters to G-. I may premise that the 
year 1865 was highly favourable for the fruiting of all 
the bushes, especially for the poUeniferous ones, some 
of which were quite barren except under such favour- 
able conditions. The season of 1864 was unfavourable. 
Id 1863 the female A produced " some fruit ;" in 1864 
only 9 ; and in 1865, 97 fruit. The female B in 1863 
was " covered with fmit ;" in 1S64 it bore 28 ; and in 



1 



FOLTGAJIOUS PLANTS. 



291 



1865 " innumerable very fine fruits." I may add, 
that three other female trees growing close by were 
observed, but only during 1863, and they then bore 
abundantly. With respect to the polleniferoua bushes, 
the one marked C did not bear a single fruit dining 
the years 1863 and 1864, but during 1865 it produced 
no leas than 92 fruit, which, however, were very poor. 
I selected one of the finest branches with 15 fruit, and 
these contained 2U seeds, or on an average 1-33 per 
fruit. I then took by hazard 15 fruit from an adjoin- 
ing female bush, and these contained 43 seeds ; that 
is, more than twice aa many, or on an average 2 -86 
per fruit. Many of the fruits from the female bushes 
included four seeds, and only one had a single seed ; 
whereas not one fruit from the polleniferoua bushea 
contained four seeds. Moreover when the two lots of 
seeds were compared, it was inanifeat that those from 
the female bushes were the larger. The second 
polleniferous bush, D, bore in 1863 about two dozen 
fruit, — in 1864 only 3 very poor fruit, each containing 
a single seed, — and in 1865, 20 equally poor fruit. 
Lastly, the three polleniferous bushes, E, F, and G, 
did not produce a single fruit during the three years 
1863, 1804, and 186;5. 

AVe thus see that the female bushes differ somewhat 
in their degree of fertility, and the polleniferoua ones 
in the most marked manner. We have a perl'eet 
gradation from the female bush, B, which in 1865 was 
covered with " innumerable fruits," — through the 
female A, which produced dnring the same year 97, — 
through the polleniferoua bush 0, which produced 
this year 92 fruits, these, however, containing a very 
low average number of seeda of araall size, — through 
the bush U, which produced only 20 poor fruit, — to 
the three bushes, E, F, and G, which did not this 



'192 



DI(ECI0U8 AKD 



year, or duriiig tlia two previous years, produce a 
single fruit. If these latter buahos and tlie more 
fertile female ones were to supplunt the others, the 
spindle-tree would be as strictly dicecioua in function 
aa any plant in the world. This caae appears to me 
very interesting, as showing how gradually an herma- 
phrodite plant may be couTerted into a dioecious one.' 
Seeing how general it is for organs which are 
almost or quite functionleas to be reduced in size, it is 
remarkable that the pistils of the poUeniferous plants 
should equal^ or even exceed in length those of the 
highly fertile female plants. This fact formerly led 
me to suppose that the spindle-tree had once been 
heterostyled ; the hemiuphrodite and male plants hav- 
ing been originally long-styled, with the pistils since 
reduced in length, but with the stamens retaining 
their former dimensions; whilst the female plant had 
been originally short^styled, with the pistil in its pre- 
sent state, but with the stamens since greatly reduced 
and rendered rudimentary. A conversion of this kind 
is at least possible, although it is the reverse of 
that which appears actually to have occurred with 
some Rubiaceous genera and jEgiphila ; for with these 
plants the short-styled form has fjecome the male, and 
the long-styled the female. It is, however, a more 
simple view that sufficient time has not elapsed for the 



' Apfording to Fritz 



[Qllcr 



ClinmixBoit 
Bontbeni Brazil is in oearl; tlie 
BsmQBtatB aaourEuoiiynins. TLe 
oyuli» art equally dtTunped in tlie 
two forms, to the female tbe pistil 
ie perfeot, nliiUt the rnitlicia &rt> 
entirely destitute of pollun. In 
the pnlltnifiirDua form, the pitttii 
li short uud tlie Btigiuita never 



separate ttoat one another, so 
Ihut, altliongh Iheir surfaoeB are 
covereil witli fairly wfll-dKVclo]icd 
pnpUltB, they cannot be (i:rtUiaed. 
lliece latter plants do not com- 
monly yield any Eruif, and am 
therefore in function mftlea. Nevcr- 
Ibetcss, on one oocaaioQ Frili 
MatleiFouiidflL'wersofthiskiudiD 
which the xtigmsB had ^ptirnte4 
and ihoy foJuL-od buiuc fruil. 



' CuAr. VII. POI.YGAJIOVS PLAXTS. 293 

reduction of the pistil in the male and hermaphrudite 
flowers of our Euonymus ; though this view does not 
account for the pistils in the poUeniferous flowers 
being sometimes longer than those iu the female 
flowers. 

Fragaria vesoa, Virginiana, Gliiloensia, t£v. (Rosacea?). 
— A tendency to the separation of the sexes iu tho 
cultivated strawberry seems to be much more strongly 
marked in the United States than in Europe ; and 
this appears to be the result of the direct action of 
climate ou ttke reproductive organs. In the best ac- 
count which I have seen,* it is stated that many of the 
varieties in the United States consist of three forms, 
namely, females, which produce a heavy crop of fruit, — 
of hermaphrodites, which " seldom produce other than 
a very scanty crop of inferior and imperfect berries," 
— and of males, which produce none. The most skilful 
cultivators plant " seven rows of female plants, then 
one row of hermaphrodites, and so on throughout the 
field." The males bear large, the hermaphrodites 
mid-sized, and the females small flowers. The latter 
plants produce few runners, whilst the two other forms 
produce many ; consequently, as has been observed 
both in England and in the United States, the poUeni- 
ferous forms increase rapidly and tend to supplant 
the females. We may therefore infer that much more 
vital force is expended in the production of ovules 
and fruit than in the production of poUen. Another 

I species, the Hautbois strawberry {F. datior), is more 
Btrictly dicecious; but Lindley made by selection an 
hennaphrodite stock.f 
Ehamnus cai}tarlieits (Rharaneie). — This plant is well 
; 



' Hr. Leonard Wraj in ' Gard. informntiou on this aubjeol, a 

Cliri'n.' 1861, p. 71B. 'VBrUti.ai uaiii-r Domett inilioi 

t Tor icfereooca nnJ TurlLur <:lt:>p. x. 2ii'.l edit. vul. i. p. i(Tri. 



I 



J 



294 



DICECIOUS AND 



CiiiP. VU 



knoivfl to bo (liuecious. 3Iy son \\'iUiam fuiind the 
two sexes growing in about equal numberB in the Isle 
of Wight, aud sent me specimens, together with obser- 
vations OR them. Each sex consists of two sub-forms. 
The two forms of the male differ in their pistils: 
in some plants it is quite small, without any distinct. 
stigma; in others the piatil is much more developed, 
with the papillce on the stigmatic surfaces moderately 
large. The ovules in both kinds of males are in an 
aborted condition. On my mentioning this case to Pro- 
fessor Caspary, he examined several male plants in 
the botanic gardens at Konigsberg, where there were 
no females, and sent me the accompanying drawings. 

Fig, 13. 




-styled m»1e. 

ItUAMNUS CATUABTICDS. (FrDI 

In the English plants the petals are not so greatly 
reduced as represented in this drawing. My son ob- 
served that those males which had their pistils mode- 
rately well developed bore alighly larger flowers, and, 
what is very remarkable, their pollen-grains exceeded 
by a little in diameter those of the males with greatly 
reduced pistils. This fact is opposed to the belief that 
the present species was once heterostyled ; for in this 
case it might have been expected that the shorter- 
styled plants would have had larger pollen -grains. 

In the female plants the stamens are in an ex- 
tremely rudimentary condition, much more so lUan 



POLYGAMOUS PLASTS. 296 

the pistils in the males. The pistil variea consi- 
derably in length in the female plants, so that they 
nitiy be iliviiled into two anb-forms according to tlia 



I 




i 



RHAlUrUB CATIFAKTICUa. 

length of this organ. Both the petals and sepals are 
decidedly smaller in the femalus than in the malts ; 
and the sepals do not turn downwards, as do those of 
the male flowers when mature. All the flowers on the 
same male or same female bush, though subject to 
some variability, belong to the same sub-form ; and 
as my son never experienced any difficulty in decid- 
ing under which class a plant ought to be included, 
he believes that the two sub-forms of the same sex 
do not graduate into one another. I can form no 
satisfactory theory how the four forma of this plant 
originated. 

Bliamims laneealatus exists in the United States, 
as I am informed by Professor Asa Gray, under two 
hermaphrodite forms. In the one, which may be called 
the short-styled, the flowers are sub-solitary, and in- 
clude a pistil about two-thirds or only half as long as 
that in the other form; it has also shorter atigmaa. The 
Btaniens are of equal length in the two forms ; but the 
anthers of the short-styled contain rather less pollen, 
far as I could judge from a few dried (lowers. My 



J 



29G 



UltEClOUB AND 



Bou compared the pollen-grains from the two forms, 
antl those from tlie long-styled flowers were to those 
from the short-styled, on an average from ten measure- 
ments, a^ 10 to 9 in diameter ; so that the two her- 
maphrodite forms of this species resemble in this 
respect the two miile forms of R. caiharticus. The 
long-atyled form is not ao common as the short-styled. 
The latter is said by Asa Gray to be the more fruitful 
of the two, as might have been expected from it« 
appearing to produce less pollen, and from the grains 
being of smaller size ; it is therefore the more highly 
feminine of the two. The long-styled form produces 
a greater number of flowers, which are clustered to- 
gether instead of being sub-solitary ; they yield some 
fruit, but as just stated are less fruitlHil than the other 
form, so that this form appears to be the more mas- 
culine of the two. On the supposition that we have 
here an hermaphroilite plant becoming dioecious, there 
are two points deserving notice; firstly, the greater 
length of the pistil in the incipient male form ; and 
we have met with a nearly similar case in the male 
and hermaphrodite forms of Euonymus compared with 
the females. Secondly, the larger size of the pollen- 
grains in the more masculine flowers, which perhaps may 
be attributed to their having retained theii normal size ; 
whilst those in the incipient female flowers have been 
reduced. The long-styled form of R.lanceolaias seema 
to correspond with the males of S. cathartieus which 
have a longer pistil and larger pollen -grains. Light 
will perhaps be thrown, on the nature of the forms 
in this genua, as soon as the power of both kinds of 
pollen on both stigmas is ascertained. Several other 
Biiccics of Khamnus are said to be dioecious" or suV 



► Locoq, ' Gc'ogr. Dot.' torn. v. ISSC, pp. i20-26. 



f Obap. VIT. 



POLYGAMOUS PLANTS. 



297 



dicBcioiis. On the other hand, S..frangvla. is an ordi- 
nary hermaphrodite, for my son found a large number 
of bushes all bearing an equal profusion of fruit. 

Epigma repens (Ericaceic). — This plant appears to 
be in nearly the same state as Skamnus oatkarliem. 
It is described byAaaGray* as existing ander four 
forms. (1) With long style, perfect stigma, and sliort 
abortive stamens. (2) Shorter style, but with stigma 
equally perfect, short abortive stamens. These two 
female forms amounted to 20 per cent, of the speci- 
mens received from one locality in Maine; but all 
the fruiting specimens belonged to the first form. 
(3) Style long, as in Ko. 1, but with stigma imperfect, 
stamens perfect. (4) Style shorter than in the last, 
stigma imperfect, stamens perfect. These two latter 
forms are evidently males. Therefore, as Asa Gray 
remarks, " the flowers may be classified into two kinds, 
each with two modifications ; the two main kinds 
characterised by the nature and perfection of the 
stigma, along with more or less abortion of the 
stamens ; their modifications, by the length of the 
style," Mr. Meehan has described f the extreme 
variability of the corolla and calyx in this plant, and 
shows that it is dicecious. It ts much to be wished 
that the pollen-grains in the two male forms should 
be compared, and their fertilising power tried on the 
two female forms. 

Jlex aquifolium (Aquifoliace«). — In the several 
works which I have consulted, one author alonej says 
that the holly is di<Bciou3. During several years I 



"AmerioaDJoiimRlorSaience.' delplila,' H&y ISGS. p. 193. 
July 18Tii. ALn'The Anicricaa ; Voucher, 'Hint. Ph;i.(loi 

NarumliBt,' 1876, p. 190. Plantus d'Europe.' 1841, U.m. U, 

f -'Vtrix.tiaDBinSjiigKa repent," p. II. 
Pn>^. Aca I. Nat. ijuc of Phi la- 



k 



298 GYNO-DIfECIOUS PLANTS. Chap. 

have examined many plants, but have never found 
one that was really hermaphrodite. I mention this 
genus because the stamens in the female flowers, al- 
though qiiit« destitute of pollen, are but slightly and 
sometimes not at all shorter than the perfect stamens 
in the male flowers. In the latter the ovary is small 
and the pistil is almost aborted. The filaments of the 
perfect stamens adhere for a greater length to the 
petals than in the female flowers. The corolla of 
the latter is rather smaller than that of the male. 
The male trees produce a greater number of flowers 
than the females. Asa Gray informs me that I. opaca, 
which represents in the United States our common 
holly, appears (judging from dried flowers) to be in a 
similar state ; and so it is, according to Vaucher, with 
several other but not witi all the species of the genus. 

Qyno-dueciou3 Plants. 

The plants hitherto described either show a tendency 
to become dioMiioua, or apparently have become so 
within a recent period. But the species now to be 
considered consist of hermaphi-odites and females 
without males, and rarely show any tendency to 
be dioecious, as far as can be judged from their 
present condition and from the absence of species 
having separated sexes within the same groups. 
Species belonging to the present class, which I have 
called gyno-dicecious, are found in various widely 
distinct families ; but are much more common in the 
Labiatce (as has long been noticed by botanists) than 
in any other group. Such cases have been noticed 
by myself in Thymus stiyyUwm and vulgaris, Saturaa 
hortensia. Origanum vulgare, and Mtn/lta hirsuta ; and 
by others in Nej)ela glachoma, Meu/hu vulgaris and 




m 



I 



,VII. GTNO-DICECIODB PLANTS. 2S9 

oquaHea, and Prunella vvlgaria. In these two latter 
Bpeciea the female form, according to H. Mtiller, ia 
infrequent. To theae must be added Dracocepkalvm 
Moldavicum, Melissa officinalia and cUnipodium, and 
Syesopus officinalis.' In the two last-nanaed plants the 
female form likewise appears to be rare, for I raised 
many seedlings of both, and all were hermaphrodites. 
It has already been remarked in the Introduction that 
andro-dicecious species, aa they may be called, or those 
which consist of hermaphrodites and males, are ex- 
tremely rare, or hardly exist. 

Thymus serpyUum. — The hermaphrodite plants pre- 
sent nothing particular in the state of their reproduc- 
tive organs ; and so it is in all the following cases. The 
females of the present species produce rather fewer 
flowers and have somewhat smaller corollas than the 
hermaphrodites ; so that near Torquay, where this 
plant abounds, I could, after a little practice, distin- 
guish the two forms whilst walking quickly paat them. 
According to Vancher, the smaller size of the corolla 
is common to the females of most or all of the above- 
mentioned LabiatiB. The pistil of the female, though 
somewhat variable in length, is generally shorter, 
with the margins of the stigma broader and formed 
of more lax tissue, than that of the hermaphrodite. 
The stamens in the female vary excessively in length ; 
they are generally enclosed within the tube of the 



• H. MBller, ■ Die Befrnnhtraig 
derBlamen,' 1873; sad* Naturu,' 
\tn:i, p. IHl. Vkuchor, • PlnatcB 
d'Europe^' b^m. iii. p. 611. For 
DmcooepliBlum, Sohimper, as 
quoted bv BrHiin, 'AniiulB and 
Stag, at' Nat. UisL' Ziid serias, voL 
Xviii. 1856, p. 380. Leonq, -(jeo. 
gniphle BoLile rt:iiro|)e,'tt)m viii. 
-- 33, 38. 44, d:c. Uutli VBiiclm 



and IiMoq wefe mwtiilten in Ihink. 
ing tlint BDvemI or tbu pljiiiti 
naiuvd JD the It^it are dicoeiniui, 
Thej appear to hiive aasuiued tliat 
the hermapbrndtte fonn was n 
male ; pernapB they were de- 
ceived bj the pifltii out bccomiujf 
full; developed and of propel 
lenglh untd sume lima altar Um 
Biitlierii liuTL- deltieoi'd. 




300 GYNODICECIODS PLANTS. Chap. TIL | 

curoUa, and their anthers do not contain any sound 
pollen; but after long search I fonnd a single plant 
with the stamens moderately esserted, and their 
anthers contained a very few fuU-aized grains, together 
with a multitude of minute empty ones. In some 
females the stamens are extremely short, and their 
minute anthers, though divided into the two normal 
cells or loculi, contained not a trace of pollen : in 
others again the anthers did not exceed in diameter 
the filaments which supported them, and were not 
divided into two loculi. Judging from what I have 
myself seen and from the descriptions of others, all 
the plants in Britain, Giermany, and near Mentone, 
are in the state just described ; and I have never 
found a single flower with an aborted pistil. It is, 
therefore, remarkable that, according to Delpino,* this 
plant near Florence is generally trimorphic, consisting 
of males with aborted pistils, females with aborted 
stamens, and hermaphrodites. 

I found it very difficult to judge of the proportional 
number of the two forms at Torquay. They often 
grow mingled together, but with large patches con- 
sisting of one form alone. At first I thought that the 
two were nearly equal in number ; but on examining 
every plant which grew close to the edge of a little 
overhanging dry cliff, about 200 yards in length, 1 
found only 12 females ; all the rest, some hundreds 
in number, being hemaaphrodites. Again, on an 
extensive gently sloping bank, which was so thickly 
covered with this plant that, viewed from the distance 
of half a mile it appeared of a pink colour, I could 
not discover a single female. Therefore the her- 

* 'Si]ll'Opora,liiDiBlnbiizione U. MOlixr, •THc Be^rwt.tang, 
dei Scfi«i Delia Finnte, &0.' 1867, 4cV p. 3-J7. 
p. 7. With respect lo GermaDr, 



Cu*r. VII. GTNO-DICECIOUS PLANTS. SOI 

maphroilites must greatly exceed in uumber the 
females, at least in the locftlities examined by me. 
A very dry station apparently favours the presence 
of the female form. With some of the other above- 
named Labiatse the nature of the soil or climate 
likewise seems to determine the presence of one or 
both forms ; thus with Nepeia glechoma, Mr. Hart found 
in 1873 that all the plants which he examined near 
Kilkenny in Ireland were females ; whilst all near 
Bath were hermaphrodites, and near Hertford both 
forms were present, but with a preponderance of her- 
maphroditea. ■ It would, however, be a mistake to 
suppose that the nature of the conditions determines 
the form independently of inheritance; for I sowed 
in the same small bed seeds of T. serjyllmn, gathered 
at Torquay from the female alone, and these produced 
an abundance of both forms. There is every reason 
to believe, from large patches consisting of the same 
form, that the same individual plant, however much 
it may spread, always retains the same form. In two 
distant gardens I found masses of the lemon-thyme 
(T. eitriodorus, a var. of T. aerpt/Uwn), which I was 
, informed bad grown there during many years, and 
every flower was female. 

With respect to the fertility of the two fonns, I 
marked at Torquay a large hermaphrodite and a largo 
female plant of nearly equal sizes, and when the seeds 
were ripe I gathered all the heads. The two heaps 
were of very nearly equal bulk ; but the heads from 
the female plant numbered IGt), and their seeds 
weighed 8'7 grains; whilst those from the her- 
maphrodite plant numbered 2UU, and their seeds 
weighed only 4' 9 gmins ; so that the seeds from the 



k 



'N'«tiiro,' Jiinu iS7:t, p. 1 



302 



GTNO-DICECIOUS PLANTB. 



female plant were to those from the hermaphrodite 
as 100 to 56 in weight. If the relative weight of 
the aeeda from an equal number of flower-heads from 
the two forms be compared, the ratio b as 100 for the 
female to 45 for the hermaphrodite form. 

77jyn»ws wilgarii,— The common garden thyme re- 
sembles in almost every respect T. serpi/Uum. The 
same slight differences between the stigmas of the 
two forms could be perceived. In the females the 
stamens are not generally quite so much reduced as 
in the same form of T. terpijlhm. In some specimeng 
sent me from Mentone by Mr. Moggridge, together 
with the accompanying sketches, the anthers of the 




female, though small, were well formed, but they con- 
tained very little pollen, and not a single sound grain 
could be detected. Eighteen seedlings were raised 
from purchased seed, sown in the same small bed ; 
and these consisted of seven hermaphrodites and 
eleven females. They were left freely exposed to 
the visits of bees, and no doubt every female flower 
was fertilised ; for on placing under the micro- 
scope a large number of stigmas from female plants. 



Chap. VTI GTNO-DHECIOUB PLANTS. S03 

not one could be found to wLich pollen-graioB of 
thyme did not adhere. The eeeda were carefully 
collected from the eleven female plants, and they 
weighed 98 '7 grains; and those from the seyen her- 
maphrodites 36 -5 grains. This gives for an equal 
number of plants the ratio of 100 to 58 ; and we 
bere see, as in the last case, how much more fertile 
the females are than the hermaplirodites. These two 
lots of seeds were sown separately in two adjoining 
beds, and the seedlings from both the hermaphro- 
dite and female parent-plants consisted of both forms. 
Satureia horiensis, — Eleven seedlings were raised in 
separate pots in a hotbed and afterwards kept in the 
green-house. They consisted of ten females and of 
a single hermaphrodite. Whether or not the condi- 
tions to which they had been subjected caused the great 
excess of females I do not know. In the females the 
pistil is rathec longer than that of the hermaphrodite, 
and the stamens are mere rudiments, with minute 
colourless anthers destitute of pollen. The windows 
of the green-house were left open, and the flowers 
were incessantly visited by bumble and hive bees. 
Although the ten females did not produce a single 
grain of pollen, yet they were all thoroughly well 
fertilised by the one hermaphrodite plant, and this 
is an interesting fact. It should be added that no 
other plant of this species grew in my garden. The 
seeds were collected from the finest female plant, 
and they weighed 78 grains ; whilst those from the 
hermaplirodite, which was a rather larger plant than 
the female, weighed only 33 '2 grains ; that is, in the 

I ratio of 100 to 43. The female form, therefore, is very 
much more fertile than the herninphrodite, as in the two 
last cases ; but the hermaphrodite was necessarily self- 
fertilised, and this probably diminished its fertility. 



I 



J 



304 



GYNO-DKECIOUS PLANTS. 



I 



We may now consider the probable meana by which 
so many uf the Labiatffi have been separated into tno 
tonus, aud the advantages thus gained. H. MiilJer" 
Buppciaea that originally aome individuala varied so as 
to produce more coospicnoua flowers ; and that insecta 
liabitually visited these first, and then dusted with 
(heir pollen visited and fertilised the less conspicuoiis 
flowers. The production of pollen by the latter plants 
would thus be rendered euperfluous, and it would be 
advantageous to the species that their stamens should 
abort, so as to save useless expenditure. They would 
thus be converted into females. But another view may 
be suggested : as the production of a large supply of 
seeds evidently is of high importance to many pl^ts, 
and as we have seen in the three foregoing cases 
that the females produce many more seeds than the 
hermaphrodites, increased fertility seems to me the 
more probable cause of the formation and separation of 
the two forms. From the data above given it follows 
that ten plants of T/it/mus serpylium, if half consisted 
of hermaphrodites and half of females, would yield 
seeds compared with ten hermaphrodite plants in the 
ratio of 100 to 72. Under similar circumstances the 
ratio with Satureta lioriensis (subject to the doubt from 
the self-fertilisation of the hermaphrodite) would be as 
too to 60, Whether the two forms originated in cer- 
tain individuals varying and pro<lucing more seed than 
usual, and consequently producing less pollen; or in 
the stamens of certain iniSividuala tending from some 
unknown cause to abort, and consequently producing 
more seed, it is impossible to decide; but in either 
case, if tho tendency to the increased production of 
(eed were ateadily favoured, the result would be llio 

• ' Dii' Befniclitnng tier Bluraen." pp. Slit, 386. 



ti 






Chap. VII. GYNO-DKEGIOUS PLANTS. 305 

oomplete abortion of the male organs. I shall pre- 
sently discuBs the cause of the smaller size of the 
female corolla. 

Soihiosa fir i!ensis(DvpsacBSB).— It has been shown by H. Mill! er 
that this speciea exists in Geimiui; tmder an tiermaphrodite nnd 
fflamle form,* In my neighbourhood (Kent) the female plants 
do not nearly equal in nnmbor the henuaphrodit^a. The atiimens 
of the femalee Tary much in their degree of abortion ; in Rome 
plants they are quite short and produce no pollen; in others 
they reach to the mouth of the corolla, but their anthers ore not 
half the proiwr size, never dehisce, and contain but few pollen- 
grains, these being colourless and of small diameter. The ber- 
maphroditfl flowers are strongly proterandons, and H. Miiller 
shows that, whilst all the stigmas on the same flower-head are 
mature at nearly the some time, the stamens dehisce one after 
the other; so that there is a great escessof pollen, which serves 
to fertilise the female plants. As the production of pollen by 
one set of plants is thus rendered superfluous, their male organs 
have become more or leas completely alwrted. Should it be 
hereafter proved that the female plants yield, as is probable, 
more seeds than the henuapbrodites, I should be inclined to 
extend the same view to this plant as to the Labiata). I have 
also observed the existence of two forms in our endemic S. 
lUcciM, and in the exotic S. uiTii-parpurea. In the latter plant, 
differently to what occurs in S. amensts, the female flowers, 
especially the larger circumferential ones, are smaller than those 
of the hermaphrodite form. According to Lecoq, the female 
flower-heods of 8. inKum are likewise smaller than those of 
what he calls the male plants, but which are probably her- 
maphrodites. 

I'lchiiim vulynra (Biiragineae).— The ordinary hermaphrodite 
form appears to tie protorandrous, and nothing more need be said 
about it. The female differs in having a much smaller corolla 
anil shorter pistil, but a well-developed stigma. The stamens 

and fenutsfl co-uxlAt^ it is, iion- 
efer, posaifale tliat ho may linva 
been ileoeLvedby tbeflDWBrat>eiQg 
BO stiongly p^ltennd^□□a. From 
wlial I,eonq eays, S. laeciia liku- 
wise ii|)!».ir» to ucaur uojer t«» 
li'irmaplirmlitaa focmn in France. 



306 



GYNO-DKECIODB PLANTS. 



Chap, \ri. 



k 



are short ; Iba anthers do not contain an; Bonnd poUen-grmns, 
but in their place yellow incoherent cells which do not Bwell 
iu water. Some plants nere in an intermediate condition; that 
ia, hail one or two or three Btamecs of proper length with pei^ 
feet anthers, the other stamens being mdimentory. In one such 
plant half of oue anther contained green perfect pollen -grains, 
and the other hsif yellowish-green imperfect grains. Both forms 
produced seed, but I neglected to observe whether in oqunl 
numbers. As I thought tliat the state of the anthers might !« 
duo to some fungoid growth, 1 examined them both in the bud 
and mature state, but could iiad no trace of mycelium. In 1862 
many female plants were found ; and in 1864, 32 plants were 
oolleoted in two localities, exactly half of which were hermaphro- 
dites, fourteen were leraales, and two in an intermediate con- 
dition. In 1866, 15 plants were colloofed in another locality, 
and those consisted of four hermaphrodites abd eleven females. 
I may add that this season was a wet one, which shows that the 
abortion of the stamens can hardly be due to the dryness of the 
sites where the plants grew, as I at one time thought pro- 
bable. Seeds from an hemmphrodita were sown in my garden, 
and of tho 23 seedhugs raised, one belonged to the intermediate 
form, all the others l)eing hermaphrodites, though two or three 
of them had unusually short stamens. I have consulted several 
botanical works, but liave found uo record of this plant varying 
in the manner here described. 

J'lantatjo lanceolata (Plantaginere), — Dolpino states that this 
plant presents in Italy three forma, which graduate from an 
anemopbilous into an entomophilous condition. According to 
H. Miiller,* there are only two forms in Germany, neither of 
whioh show any special adaptation for insect fertilisation, and 
both appear to bo hermaphrodites. But I have found in two 
localities in England female and hermaphrodite forms existing 
together ; and the same fact has been noticed by others.t The 
females ore Iobb frequent than the hermaphrodites ; their stamens 
are short, and their anthers, which are of a brighter green 
whilst young than those of the other form, dehisce properly, yet 
contain either no pollen, or a small amount of imperfect graina 
of variable size. All the flower-heads on a plant belong t 

• -Die Btfnichtuns.' An., p. 342. 

t Mr. C. W. CnK'kur in 'The 

Cionleiicr'aCbroaiolu,' ISlA, p. 294. 



OaiP. VIL SIZE OF THE COBOLLA. 



307 



the same form. It is well known that this species is Btrongl; 
proterogjaouB, and I found that the protruding atigmae of both 
the hermaphrodite and female flowers were penetrated by pollen- 
tubes, whilst their own anthers were immature and had not 
escaped out of the hud. Flautaijo m:dia does not present two 
forms; but it appears from Asa G-ray's description,* that such 
ia the case with foor of the North American species. The co- 
rolla does not properly expand in the short-etamened form o( 
these plants. 

Cnicui, tierraMa, Eriophornm. — In the Composita, Cni'cus 
paluslriK and acauia are said by Sir J. E. Smith to exist as her- 
maphrodites and females, the former being the more frequent. 
"With Sej-mtulii tinetoria a regular gradation maybe followed 
firom the hermaphrodite to the female form ; in one of the latter 
plants the stamens were bo tall that the anthers embraced the 
style as in the hermaphrodites, but they contained only a few 
grains of pollen, and these in an aborted condition ; in an- 
other female, on the other hand, the anthers were much more 
reduced in size than is usual. Lastly, Dr. Dickie him shown 
that with Eriophorara iingusti/oliwii (Cyperaceffi) hermaphro- 
dite and female forms exist ia Scotland and the Arctic regions, 
both of which yield seed, t 

It is a curious fact that in all the foregoing poly- 
gamous, dicecioua, and gyno-dicecioua plants in which 
any difference has been observed in the size of the 
corolla in the two or thiee forma, it ia rather larger in 
the females, which have their atamena more or less or 
quite rudimentary, than in the hermaphrodites or males. 
This holda good with Euonymus, Rhamnus cathartiens, 
Ilex, Fragaria, all or at least most of the before-named 
Labiate, Seabioaa atro-pwrpurm, and Echium vidgare. 
60 it is, according to Von Mohl, with Cardamine 



I 



L 



'Manonl of tbe Butany of 
N. United Slater' 2Dd tdii 
J, p. Ilti9. Bee tiao ' Aoierioan 
Journal of Soisnce,' Nov. 1862, 
■■" ml Pkv, Atnerioiia 
ul (icioucu,* t>i:t. 11, 



t Sir J. E. Smitb, ■ Tmna. 
Litin. Soo.' to). liii. p. 599. 
Dr. Dickie, ' Jonrnnt Una. Sua 
But.' vol. Ix. 1865, p. ItiL 




308 



SIZE OF THE COBOLLA. 



Chap. ■VTI. 



arnara, Geraniwn siflvatusum, Myosotis, and Salvia, 
On tLe other band, aa Von Molil remarks, when a 
plant produces hermaphrodite flowers and others 
which are males owing to the more or less complete 
abortion of the female organs, the coroUas of the 
moles are not at all increased in size, or only excep- 
tionally and in a slight degree, as in Acer. " It seems 
therefore probable that the decreased size of the female 
corollas in the foregoing cases is due to a tendency to 
abortion spreading from the stamens to the petals. We 
Bee how intimately these organs are related in double 
flowers, in which the stamens are readily converted 
into petals. Indeed some botanists believe that petals 
do not consist of leaves directly metamorphosed, but of 
metamorphosed stamens. That the lessened size of the 
corolla in the above case ia in some manner an indirect 
result of the modification of the reproductive organs ia 
supported by the fact that in BJuimnus cathartifniB not 
only the petals but the gieen and inconspicuous sepals 
of the female have been reduced in size ; and in the 
strawberry the flowers are largest in the males, mid- 
sized in the hermaphi'odites, and smallest in the fe- 
males. These latter cases, — the variability in the size 
of the corolla in some of the above species, for instance 
in the common thyme, — together with the fact that it 
never differs greatly in size in the two forms— make 
me doubt much whether natural selection has come 
into play ;— that b whether, in accordance with H. 
Hnller's belief, the advantage derived from the pol- 
leniferous flowers being visited first by insects haa 
been sufllcient to lead to a gradual reduction of the 
corolla of the female. We should bear in mind that ag 
the hermaphrodite is the normal form, its corolla had 



'Bit. Zut 



iig.' lS03,p, 32a 



OHiP. Vn. SIZE OF THE COROLLA. 309 

probably retained its original size/ An objection to 
the above view should not be passed over ; namely, that 
the abortion of the stamens in the females ought to 
have added through the law of compensation to the 
size of the corolla ; and this i>erhaps would have oc- 
curred, had not the expenditure saved by the abor- 
tion of the stamens been directed tfl the female repro- 
ductive organs, so as to give to this form increased 
fertility, ^ ___^ 



* It doea not nppear to me 
thnt Ketner'fl viev ('Die Soliutz- 
mitttl des PoIIodb,' 1873, p. 5(i) 
■xji be acRi'pied in the present 
eoM's, nnmely that the larger 



males nerves to protect their pollen 
frriiii rain. In the j;etiQS Thyjiiua, 
for inBtaniB, the abnttad Bntliera 
of tlie famale ara much better 
priitected tlinn tbc> ptufaot ones uf 
I 111: lii^nnaplirodita. 



CLEISTOGASIIC FLO'.VEBS. 



CHAPTEa vm. 

CLBisroOAiiio FLOWisa. 

Q«nernl ohHTutor of clelBtnifainic flawerE-^LIst of the genera pn>lnotng 
aooh flowera, and Iboir diatribntion in the ttgeteble serieB— Viola, 
dee?ri]]tioii of the cleistognniic Sowers iu tLe £e?er.il flpeciea, their 
fertility minpared witli thut of tlio [jBifett flowera^-Oialu 
acrloBflla— O. uinBitlnt. thn-e foims of oleintogamii! flowio-a — Van- 
de 1 lia — Ooonis — I eq patiena — Dnwem — M iaceUaneous obBervatiuns 
on various othi-rcleistogaiiiio plaata — Ain-mnpliilous Bpet^ieu produc- 
ing tlfeiTstogiiiiiip flowtra — Leemia. perfect flowtra isrelj developed 
— Summary and coni'lildiiig remarka on th« origin of oieistouumio 
flowera -The oliief mn.'liiBiouH which nuij bo drawn from the 
obauivatiooa iu tbia volume. 

It was known even before the time of Limueua that 
certain plants produced two kinds of flowers, ordi- 
nary open, and minute closed ones ; and this fact 
formerly gave rise to warm controversies aiwat the 
sexuality of plants. These closed flowers have been 
appropriately named cleistogamic by Dr. Kulm." 
They are remarkable from their small size and from 
never opening, so that they resemble buds ; their petals 
are rudimentary or quite aborted ; their stamens are 
often reduced in number, with the jinthers of very 
small size, containing few pollen-grains, which have 
remarkably thin transparent coats, and generally emit 
their tubes whilst stUl enclosed within the anther- 
cells ; and, lastly, the pistil is much reduced in size, 
with the stigma in some cases hardly at all developed. 
These flowers do not secrete nectar or emit any odour ; 
from their small size, as well as from the corolla being 
rudimentary, they are singularly inconspicuous. Coii« 

• ■ Uut. Zciifung,' 1307, p. 65. 



CLBISTOGAMIC FLOWEBS. 



3U 



Bequently insects do not visit them ; nor if they did, 
could they find an entrance. Such flowers are therefore 
invariably self-fertilised ; yet they produce an abund- 
ance of seed. In several cases the young capsules 
bury themselves beneath the ground, and the seeds 
are there matured. These flowers are developed before, 
or after, or simultaneously with the perfect ones. 
Their development seems to be largely governed by 
the conditions to which the plants are exposed, for 
during certain seasons or in certain localities only 
cleistogamic or only perfect flowers are produced. 

Dr. Kuhn, in the article above referred to, gives a 
list of 44 genera including species which bear flowers 
of this kind. To this list I have added some genera, 
and the authorities are appended in a foot-note. I 
have omitted three names, from reasons likewise given 
in the foot-note. But it is by no means easy to de- 
cide in all cases whether certain flowers ought to be 
ranked as cleistogamic. For instance, Mr. Bentham 
informs me that in the South of France some of the 
flowers on the vine do not fully open and yet set 
fruit ; and I hear from two experienced gardeners that 
this is the case with the vine in our hot-houses ; but 
as the flowers do not appear f« be completely closed it 
would be imprudent to consider them as cleistogamic. 
Tho flowers of some aquatic and marsh plants, for 
instance of Banuncultts aquatilis, Alisnia naiaTia, 
Subularia, Illecebrum, Menyanthes, and Euryale,* 
remain closely shut as long as they are sub- 
merged, and in this condition fertilise themselves. 



* Delpino/BairOperaJeDietri- 
iiioDcdei Seasi nelle Piantii,' &!!• 
[ .JB67, p. 30. Subnlujiii. banevor, 
I MaLetiiiieg baa ita tloneni full; 
L npanili'd beiimCli the watei, see 
[ Bir J. E. BiuUh, ■ Englkh FI>j[»,' 

2! 



?ul. iii 1S2S, p. 157. For tlie 
betiKvuiurolMeDftiQtheeiti Rii»<i ■ 
BeoGilliiiett in'Aot. A«ul. St. Vt- 
tere>i,,' 1777, part ii. p. 45.— On 
Eurykle, ' (>oidi;Dei'i Cl'ruHicle, 
1877, i>. ^80. 



312 



CLEIBTOGAUIC KLOWEBa Chap. VUL 



They beliave in tbU maoner, apparently as a protec- 
tiun to their pollen, and produce open flowers when 
expi>9uJ to the air; so that these cases seem rather 
different from those of true cleiatogamic flowers, and 
have nut been included in the list. Again, the flowers 
of sunie plants which are produced very early or very 
late in the season do not properly expand ; and these 
might perhaps be considered as incipiently cleisto- 
gamic ; but as they do not present any of the remark- 
able peculiarities proper to the class, and as I have 
not found any full record of such cases, they are not 
entered in the list. When, however, it is believed oh 
fairly good evidence that the flowers on a plant in iti 
native country do not open at any hour of the day or 
night, and yet set seeds capable of germination, these 
may fairly be considered as cleistogamic, notwitli- 
standing that they present no peculiarities of struc- 
ture. I will now give &a complete a list of the genera 
containing cleistogamia species as I have been able 
to collect. 

Table 38. 
List of Oenem inchidiay Chisto'jamic Species (rhiejfy after Kuh"V 



a 

il 



faitrlchjam (Dorni^Defl!). 
Ciuciita (CoDvolrularesL'). 
ScTDphularia (Scrn|ihulnriDes). 

Vuidtllia " 

Cry phiacHD thus (Ac-iDthacex). 

ErHathemum 

" I bavp tinilttrilTrir.iliam and 
Arnthia framlhe list, becau/se Vdd 
Miihl Ba<ra (' B.'t. ZoitunK,' t8ij3. 
p. 312) tlial tJi^ Qoncr-HtoiiiB 
mprely drair tlis Hotvini b neatb 
tlie groun'l, nnil thnt tlietie lio not 
Kiipenr to be proutrly ileiBtogamic. 
CorreR cte Mello C'J'mm»l Linii. 
SiJO Dot.' vol. li. 1870, p. 254) 
sWjved pluiita uf Aracliia m 



L&miam (Labia tic]. 

Siilvia 

Oiybaphoa (Nydiginew). 

BroKll, ani! could never fliid sncli 
flowera. Plgmtagohasboenoniilti-d 
bonuae as f.ir as I can discoTer it 
pr.iduc'ea liermaplirwlite and fe- 
male flnwer-beada, but not eleia- 
toj^mie flowera. K raacheninifcowh 
(vel StallariB) hoa been omittal 
liaoauae it aaema verj doubtful 
frnra Maximnwii-z" des ' "' 



iL.,Lcr t 



■r Jlowf 



vlikb 



CLEISTOGAMIC FLOWEES. 



Table 38 — crmifnued 



DICOTTIJ'.DOm. 

Uj-ctaginia (N)-etBgiilB«)- 
bLipelia (Aaclepiods). 
Specular IB (CampaDiilsceiE). 



Polygala (PolygaW). 
Impaliena (DslsinniBea), 
Olalis (OeraDiaceB!). 
ODoDis (LeguiniaoBie). 



Jnncna (Juucea). 
Leersia (GramineK), 
Honleum „ 

Ciyptostachji „ 
CotDiuelina (Commetineii'). 
Mgnothoria (Pontederaciw), 
Schgmburgkia (Orchidea). 
CaltUta „ 

EpiJfudrpa 
ThelyniitrB 



UkiD no petals or very aaaW onea, 
mil barren slHiiioiia or uune, hth 
elelHtogaiuio ; ihe uppof lieima- 

phrodit- " — ""' *- 

" ' " ! iruit. anil 

a gTamSiiea, aa Babin^n 
romarkaCBritiBli Bi.tany," 1851, 
p. SI) ''gLorter aud lunger petula 
ttonmpiuiy an imperfectiuD uf the 

I have added to the Vtat tbe fol- 
loningi'aBiw: SoTiralAcanthweo, 
for which tcs J. Si-ott in ' Juurnal 
of Bnt.' (London), new eeriea, yol. 
L 1S72, p. 161. With leapect to 
BalvU Bee Dr. AEoheiiOD in ' Bot. 
Zeitung,' 1871. p. SSS. For O^y- 
biiphua tad Nyctagioia aee Aea 

IQray in 'American Natutaliat,' 
Hot. Ih73, p, ftfg. From Dr. 
Torrey'l account uf Eoltonia 
ihfiala (' Bull, nf Tonty BoUn. 
Club,- i«1. 11. June 1871) it \a 
■MtnifE'Bt that thla plant |irixiuMd 
Ink) clcinlo^iuaia ilunwx. I'oi 



Pnvooia Bee Boaohtf in ' Sitiuugn- 
bariuhtH d. QewUsoh. N.itur. 
Fraunde,' Oit. 20, 1874, p. 90. I 
bars added Thelymitr»,a;i froin Ibu 
aoitniiit giveu by Mr. FitKt'^iald in 
bis maguifiueiit norli on 'Aoslni- 
liiinOtchida' it ttppariB that tlio 
flowera of this pluot in its nalira 
home never open, but they do nut 
appear to bo rudnced in aixe. Nur 
is this the case with the flowers n( 
certain species uf Epidpiidroii, 
Cuttlej'a, &(!. (aie aeoaud editii.ii 
of my ■ FerlilibiitinD of Orchidb.' 
p. 147), whiob nithout expandiii|{ 
piodni B oapsulea. It U therefore 
doubtful whether these Drchideiu 
ig-lit tu ha%e been in>^lllded in Cl.c 



liHt. Piomwhat Duval-J( 
about CryptiiHtacbys Ii 
t'oe. Bot.de France,' totn.s. i 
p. 1115, Ibis plant appcaiB to 



BuiL 




31-i 



CLEISTOGAMIC FLOWERS. 



The firat point that strikes us in considering tliis list 
of 55 genera, is that they are very widely distributed 
in the vegetable series. They are more common in the 
family of the Leguminosfe than in any other, and next 
in order in that of the Acanthacese and Malpighioct 
A large number, but not all the species, of certain 
getera, as of Oxalis and Viola, bear cleistogamic aa 
well as ordinary flowers, A second point which de- 
serves notice is that a considerable proportion of thai 
genera produce more or less irregular flowers ; this is 
the case with about 32 out of the 55 genera, but to this 
subject I shall recur. 

I formerly made many observations on cleistogamic 
flowers, but only a few of them are worth giving, since 
the appearance of an admirable paper by Hugo vou 
Mohl,* whose examination was in some respecf-s much 
more complete than mine. His paper includes also an 
interesting history of oar knowledge on the subject, 

Viola eantJta. — The calyx of the cleistogamic flowers 
differs in no respect from that of the perfect ones. Th( 
petals are reduced to five minute scales ; the lower oni 
which represents the lower lip, is considerably larger 
than the others, but with no trace of the spur-like 
nectary; its margins are smooth, whilst those of the 
other tour scale-like petals are papillose. D. MiUler of 
Upsala says that in the specimens which he observed 
the petals were completely aborted.! The stamens are 
very small, and only the two lower ones are provided 
with anthers, which do not cohere together as in the 
perfect flowers. The authors are minute, with the two 
cells or loculi remarkably distinct; they contain very 
little pollen in comparison with those of the perfect 

n th<> Itrst fiilt K'.d 



I 



• -Bol. Zeituug,' 1SG3, p. 309- paper ronta' 

E8. Biiliafi.Ph)rvii 

t IbiJ. 1857, p. 730. Tliis gamlc Uowur 



I CuAF. Ynt 



315 



flowers. The connective expands into a membranous 
hood-like shield which projects above the anther-cells. 
These two lower stamens have no vestige of the curions 
appendages which secrete nectaj in the perfect flowers. 
The three other stamens are destitute of anthers and 
have broader filaments, with their terminal membran- 
ous expansions flatter or not so hood-like aa those of 
the two antheriferous stamens. The pollen-grains have 
remarkably thin transparent coats ; when exposed to 
the air they shrivel up quickly ; when placed in water 
they swell, and are then f gj^ of an inch in diameter, 
and therefore of smaller size than the ordinary pollen- 
grains similarly treated, which have a diameter of 
SooV "^^ ^° inch. In the cleistogamic flowers, the 
pollen-grains, as far as I could see, never naturally fall 
out of the anther-cells, but emit their tubes through a 
pore at the upper end. 1 was able to trace the tubes 
from the grains some way down the stigma. The pistil 
ia very short, with the style hooked, so that its ex- 
tremity, which is a little enlarged or funnel-shaped 
and represents the stigmaj is directed downwards, 
being covered by the two membranous expansions of 
the antheriferous stamens. It is remarkable that there 
is an open passage from the enlarged funnel-shaped 
extremity to within the ovarium ; this was evident, as 
Blight pressure caused a bubble of air, which had been 
drawn in by some accident, to travel freely from one 
end to the other : a similar passage was observed by 
Michalet in V. alba. The pistil therefore difl'ers con- 
siderably from that of the perfect flower ; for in the 
latter it is much longer, and straight with the excep- 
tion of the rectangularly bent stigma ; nor is it per- 
forated by an open passage. 

The ordinary or perfect flowers have been said by 
aome authors never to produce capsules ; bat this is an 



I 

I 
I 




I 

L 



CLEISTOGAMIO FL0WEB8. Caxe. VIIL 

error, though oa\j a small proportion of them do so. 
This appears to de|)end in some cases on their anthers 
not containing even a trace of pollen, but more gene- 
rally on bees not visiting the flowers. I twice covered 
with a net a group of flowers, and marked with threads 
twelve of them which had not as yet expanded, Tliis 
precaution is necessary, for though as a general nde 
the perfect flowers appear considerably before the 
oleistogamic ones, yet occasionally some of the latter 
are produced early in the season, and their capsules 
might readily be mistaken for those produced by the 
perfect flowers. Not one of the twelve marked perfect 
flowers yielded a capsule, whilst others under the net 
which had been artificially fertilised produced five 
capsules ; and these contained exactly the same aver- 
age number of seeds as some capsules from flowers 
outside the net which had been fertilised by bees. I 
have repeatedly seen BoiTihiis hortorum, lapidariuB, and 
a third species, as well as hive-bees, sucking the 
flowers of this violet : I marked six which were thus 
visited, and four of them produced fine capsules ; the 
two others were gnawed off by some animal. I 
watched Bombus hortorum for some time, and when- 
ever it came to a flower which did not stand in a con- 
venient position to be sucked, it bit a hole through the 
Bpni-like nectary. Such ill-placed flowers would not 
yield any seed or leave descendants ; and the plants 
bearing them would thus tend to be eliminated through 
natural selection. 

The seeds produced by the oleistogamic and perfect 
flowers do not differ in appearance or number. On 
two occasions I fertilised several perfect flowers with 
pollen from other individuals, and afterwards marked 
some cleistogamic flowers on the same plants ; and the 
result was l!i;if 14 cnpsules produced by the perfect 



I 




f Ohav. Vm. VIOLA. 317 

flowers contained on an average 9-S5 seeila; and 17 
capsules from the cleistogamie ones contained 9 "64 
Boeds,^ — an amount of difference of no significance. It 
is remarkable how much more quickly the capsules 
&om the cleistogamie flowers are developed than those 
from the perfect ones ; for instance, several perfect 
flowers were cross-fertilised on April 14th, 1863, and a 
month afterwards (May 15th) eight young cleistogamie 
flowers were marked with threads ; and when the two 
sets of capsules thus produced were compared on 
June 3rd, there was scarcely any difference between 
them in size. 

Viola odorata (white-flowered, single, cultivated va- 
riety). — The petals are represented by mere scales as 
in the last species ; but differently from in the last, 
all five stamens are provided with diminutive anthers. 
Small bundles of pollen-tubes were traced from the 
five anthers into the somewhat distant stigma. The 
capaulea produced by these flowers bury themselves 
the soil, if it be loose enough, and there mature them- 
selves." Lecoq says that it is only these latter cap- 
sules which possess elastic valves ; but I think this 
must be a misprint, as such valves would obviously be 
of no use to the buried capsules, but would serve to 
Bcatter the seeds of the sub-aerial ones, as in the other 
species of Viola. It is remarkable that this plant, ac- 
cording to Delpino,t does not produce cleistogamie 
flowers in one part of Liguria, whilst the perfect flowers 
are there abundantly fertile ; on the other hand, 
cleistogamie flowers are produced by it near Turin. 
Another fact is worth giving as an instance of corre- 

• VaochBTBayaCHiBt. Pl.yB i!ea torn. v. ISSB, p. 18(1. 
Planles d'Europe torn, iii, 18*4, f ' Sull' Upflra,!B Ui4ribnzir>no 

ti SOU) that V. hirla anil e<Mina dei Seta Delle Pianto,' Ae., IHUT, 

Ikewise bury tlieir capBulefl. — p. 31), 
Bee also X-eooq, ' Gcbgreph. BnL' 



L 



818 CLEtSTOGAMIC FLOWEES. Chap. TiH 

luted development : I found on a purple variety, 
ui'ter it bad produced its perfect double flowers, and 

wliilat the white single variety was bearing its cleisto- 
gamic flowers, many bud-like bodies which from their 
position on the plant were certainly of a cleistogamic 
nature. They consisted, as could be seen on bisecting 
them, of a dense mass of minute scales closely folded 
over one another, exactly like a cabbage-head in 
miniature. I could not detect any stamens, and in the 
place of the ovarium there was a little central column. . 
The doubleness of the perfect flowers had thus spread J 
to the cleistogamic ones, which therefore were ren- ■ 
dered quite sterile. I 

Viola hirta.— The five stamens of the cleistogamic 
flowers are provided, as in the lost case, with small 
anthers, from all of which pollen-tubes proceed to the 
Btigma. The petals are not quite eo much reduced 
as in V. canina, and the short pistil instead of being 
hooked is merely bent into a rectangle. Of several 
perfect flowers which I saw visited by hive- and humble- 
bees, six were marked, but they produced only two 
capsules, some of the others having been accidentally 
injured, M. Monnier was therefore mistaken in this 
case as in that of V. odorata, in supposing that the 
perfect flowers always witliered away and aborted. He 
states that the peduncles of the cleistogamic flowers 
curve downwards and bury the ovaries beneath the 
soil.* I may here add that Fritz Miiller, as I hear 
from his brother, has found in the highlands of South- 
ern Brazil a white-flowered species of violet which 
bi?ars subterranean cleistogamic flowera. 

■ These Btateimnita are tabon lo tlie euppoBcd starllity of the 

from Protetsor Oliver's oica!lent pirfeot flowera in tliis gsniu eea 

BTticle ia tho ' Nat. Hial. Keview,' alto Timbal-lingrave iu * Bol 

July I8ti2, p. 23S. WUli ixBpeut Ztituiig,' 1854, p. 771 



Cbip. VIIL 



319 



I 



Viola naito.-— Mr. Scott sent me seeds of this Indian 
species from the Sikkim Ter&i, from which I raised 
many plants, and from these other seedlings during 
several successive generations. They produced an 
abundance of cleistogamic flowers during the whole of 
each summer, but never a perfect one. When Mr. Scott 
wrote to me his plants in Calcutta were behaving simi- 
larly, though his collector saw the species in flower in 
its native site. This case is valuable as showing that 
we ought not to infer, as has sometimes been done, 
that a species does not bear perfect flowers when grow- 
ing naturally, because it produces only cleistogamic 
flowers under culture. The calyx of these flowers is 
sometimes formed of only three sepals ; two being 
actually suppressed and not merely coherent with the 
others; this occurred with five out of thirty flowers 
which were examined for this purpose. The petals are 
represented by extremely minute scales. Of the sta- 
mens, two bear anthers which are in the same state as 
in the previous species, but, as far as I could judge, 
each of the two cells contained only from 20 to 25 de- 
licate transparent pollen-grains. These emitted their 
tubes in the usual manner. The three other stamens 
bore very minute rudimentary anthers, one of which 
was generally larger than the other two, hut none of 
them contained any pollen. In one instance, however, 
a single cell of the larger rudimentary anther in- 
cluded a little pollen. The style consists of a short 
flattened tube, somewhat expanded at its upper «nd, 
and this forms an open channel leoiling into th'i 
ovarium, as described under V. fanina. It is slightly 
bent towards the two fertile anthers. 

Viola Baxbarffhiana. — This 8[»ecieii Ixiri in my liiil>- 
house during two years a multitude of <;lnint*jj(aiiil» 
Bowers, which resembled in all niwjxMili iluM» nt IIm 



820 CLEIBTOGASnO FLOWERS. Chap. VTII. 

laat Bpeciea ; but no perfect ones were produced, llr. 
Scott informs me that in India it bears perfect flowers 
only during the cold season, and that these are quite 
fertile. During the hot, and more especially during 
the rainy season, it bears au abundance of cleisto- 
gamic flowers. 

Many other species, besides the five now described, 
produce cleistogamic flowers ; this is tbe case, accord- 
ing to D. Muller, Michalet, Von Mohl, and Hermann 
Mailer, with V. elaiior, lanci/oUa, sylvaiica, pcdustrin, 
mirahUis, bicolor, ionadiwm., and biftora. But V. tricolor 
does not produce them. 

Michalet asserts that V. pcdustris produces near 
Paris only perfect flowers, which are quite fertile ; but 
that when the plant grows on mountains cleistogamic 
flowers are produced ; and so it is with V. hifiora. 
The same author states that he has seen in the case 
of V. aiha flowers intermediate in structure between 
the perfect and cleistogamic ones. According to M. 
Boisduval, an Italian species, V. Ruppii, never bears 
in France " des fleurs bien apparentes, ce qui no I'em- 
pache pas de fructifler." 

It is interesting to observe the gradation in the 
abortion of the parts in the cleistogamic flowers of 
the several foregoing species. It appears from the 
statements by D. Miiller and Von Mohl that in V. mi- 
rabilis the calyx does not remain quite closed ; aU Ave 
stamens are provided with anthers, and some pollen- 
grains probably fall out of the cells on tbe Btignia, 
instead of protruding their tubes whilst still enclosed, 
as in the other species. In V. Mrla all five sta- 
mens are likewise antheriferous ; the petals are nut 
so much reduced and the pistil not so much modified 
as in the following species. In V. nana and eluiior 
only two of the stamens properly bear anthers, bat 



J 



r Chat. VIII. 



321 



H aometimes one or even two of the others are tliiia pro- 
H Tided, Lastly, in V. canina never more than two of 
H the stamens, as far as I have seen, bear anthers ; the 
H petals are much more reduced than in V. hirta, and 
H according to D, Miiller are sometimes quite absent. 
H Oseaiia aeetosella. — The existence of cleistogamic 
■ flowers on this plant was discovered by Michalet." 
K They have been fully described by Von Mohl, and I 
K c£in add hardly anything to his description. In my 
H specimens the anthers of the five longer stamens were 
H nearly on a level with the stigmas ; whilst the smaller 
B and less plainly bilobed anthers of the five shorter 
H stamens stood considerably below the stigmas, so that 
their tubes had to travel some way upwards. Ac- 
cording to Michalet these latter anthers are some- 
times quite aborted. In one case the tnhes, which 
ended in excessively fine points, were seen by me 
stretching upwards from the lower anthers towards 
the stigmas, which they had not as yet reached. My 

t plants grew in pots, and long after the perfect flowers 
had withered they produced not only cleistogamic hut 
a few minute open flowers, which were in an inter- 
mediate condition between the two kinds. In one of 
these the pollen-tubes from the lower anthers had 
reached the stigmas, though the flower was open, 

»The footstalks of the cleistogamic flowers are much 
shorter than those of the perfect flowers, and are so 
much bowed downwards that they tend, according to 
"Von Mohl, to bury themselves in the moss and dead 
leaves on the ground, Michalet also says that they 
are often hypogean. In order to ascertain the nnm- 

Iber of seeds produced by these flowers, I marked eight 
of then] ; two failed, one cast its seed abroad, and the 
• ■ Dull. Soo. Dol. Je FmiiOL',' Mm. vU. iS«0. .. (U5. 



822 



CLEISTOGAHIO FLOWEBB. 



remaining £ve contained on an average lO'O seeda 
per capsule. This is rather above the average 9'2, 
which eleven capsules from perfect flowers fertilised 
with their own pollen yielded, and considerably above 
the average 7'9, from the capsules of perfect flowers 
ft'rtilised with pollen from another plant; but this 
latter result must, I thini, have been accidental. . 

Hildebrand, whilst searching various Herbaria, ob*J 
served that many other species of Osalis besides 0, 1 
acetosdla produce cleistogamic flowers ; • and I hear \ 
from him that this is the case with the heterostyled 
trimorphic 0. incamata from the Cape of Good Hope. 

Osealia (Biophi/tum) aenaitiva. — This plant is ranked 
by many botanists as a distinct genua, but as a sub- 
genus by Bentham and Hooker. Many of the early 
flowers on a mid-styled plant in my hot-house did not 
open properly, and were in an intermediate condition 
between cleistogamic and perfect. Their petals varied 
from a mere rudiment to about half theii proper size ; 
nevertheless they produced capsules. I attributed 
their state to unfavourable conditions, for later in the 
season fully expanded flowers of the proper size ap- 
peared. But Mr. Thwaites afterwards sent me from 
Ceylon a number of long-atyled, mid-styled, and short- 
styled flower-stalks preserved in spirits ; and on the 
same stalks with the perfect flowers, some of which were 
fully expanded and others still in bud, there were 
small bud-like bodies containing mature pollen, but 
with their calyces closed. These cleistogamic flowers 
do not differ much in structure from the perfect ones 
of the corresponding form, with the excjption that 
their petals are reduced to extremely minute, barely 
risible scales, which adhere firmly to the rounded 



' Monatebericht der Kkad. der Wias, 



in,' IS6S. p. :{69. 



J 



Chap. VUL 0XALI8. 323 

bases of the shorter stamens. Their stigmas are much 
less papillose, and smaller in about the ratio of 13 to 
20 divisionH of the micrometer, as measured trana- 
versely from apex to apux, than the stigmas of the 
perfect flowers. The styles are furrowed longitudinally, 
and are clothed with simple as well as glandular baira, 
but only in the cleistogamic flowers produced by the 
luug-styled and mid-styled forms. The anthers of the 
longer stamens are a little smaller than the correspond- 
ing ones of the perfect flowers, in about the ratio of 
11 to 14. They dehisce properly, but do not appear 
to contain much pollen. Many pollen-grains were 
attached by short tubes to the stigmas ; but many 
others, still adhering to the anthers, had emitted 
their tubes to a considerable length, without having 
come in contact with the stigmas. Living plants 
ought to be examined, as the stigmas, at least of the 
long-styled form, project beyond the calyx, and if 
visited by insects (which, however, is very improbable) 
might be fertilised with pollen from a perfect flower. 
The most singular fact about the present species is 
that long-styled cleistogamic flowers are produced by 
the long-styled plants, and mid-styled as well as 
short-styled cleistogamic flowers by the other two 
forms ; so that there are three kinds of cleistogamic 
and three kinds of perfect flowers produced by this 
one species 1 Most of the hcterostyled species of 
Oxalis are more or less sterile, many absolutely so, if 
llegitimately fertilised with their o*Tn-form pollen. 
It is therefore probable that the pollen of the cleisto- 
gamic flowers has been modified in power, so as to act 
their own stigmas, for they yield an abundance of 
ds. We may perhaps account for the cleistogamic 
flowers consisting of the three forms, through the prin- 
ciplu of uorfflatcd growth, by which the cleistognnjin 



824 



CLEISTOGASIIC FLOWEE8. CHiP.Tni 



llowurs of tho double violet have been rendered 
duuble. 

VandeRia numnudari/oHa. — Dr. Kulm has collected ' 
all the uoticps with respect to cleistogamic flowers in 
this genus, and has described from dried specimeiiB 
those produced by an Abyssinian species. Mr. Scott 
stnt me from Calcutta seeds of the above common 
Indian weed, from which many plants were success- 
ively raised during several years. The cleistogamic 
fluwera are very small, being when fully mature under 
^ of an inch (1-27 mm.) in length. The calyx does 
not open, and within it the delicate transparent :orolla 
remains closely folded over the ovarium. There are 
only two anthers instead of the normal number of four, 
and their filaments adhere to the corolla. The cells of 
the anthers diverge much at their lower ends and are 
onlyy^of an inch ('181 mm.) in their longer diameter. 
They contain but few pollen -grains, and these emit 
their tubes whilst still within the anther. The pistil 
ia very short, and is surmounted by a bilobed stigma. 
As the ovary grows the two anthers together with the 
shrivelled corolla, all attached by the dried pollen- 
tubes to the stigma, are torn off and carried upwards 
in the shape of a little cap. The perfect flowers gene- 
rally appear before the cleistogamic, but sometimes 
simultaneously with them. During one season a large 
number of plants produced no perfect flowers. It has 
' been asserted that the latter never yield capsules ; but 
this is a mistake, as they do so even when insects are 
excluded. Fifteen capsules from cleistogamic flowers 
on plants growing under favourable conditions con- 
tained on an average 64-2 seeds, with a maidmum of 
87 : whilst 20 capsules from plants growing mni'b 



■ DiiL Zcitung,' 18G7, p. C5. 



0NUNI8. 



3'J5 



crowded yielded an average ot' only 48. Sixteen oap- 
flulea from perfect flowers artificially crossed with pollen 
&om another plant contained on an average 93 aeeds, 
with a masimum of 137. Thirteen capsules liom aelf- 
fertiliaed perfect flowers gave an average of 62 seeds, 
with a maximom of 135. Therefore the capsules from 
the cleistogainic flowers contained fewer seeds thuu 
those from perfect flowers when cross-fertilised, and 
slightly more than those from perfect flowers self- 
fertilised. 

Dr. Kuhn believes that the Abyssinian V. Bessiflora 
does not differ specifically from the foregoing species. 
But its eleistogamic flowers apparently include four 
anthers instead of two as above described. The plants, 
moreover, of Y. aesaifiora produce subterranean runners 
which yield capsules ; and I never saw a trace of such 
runners in V. nummularifolia, although many plants 
were cultivated. 

Linaria ipuria. — Michalet says* that short, thin, 
twisted branches are developed from the buds in the 
^Is of the lower leaves, and that these bury them- 
selves in the ground. They there produce flowers 
not offering any peculiarity in structure, excepting 
that their corolhis, though properly coloured, are de- 
formed. These flowers may be ranked as eleistogamic, 
BB they are developed, and not merely- dra^vn, beneath 
the ground. 

Ononia colutimee. — Plants were raised from seeds sent 
me from Northern Italy. The sepals of the eleisto- 
gamic flowers are elongated and closely pressed to- 
gether; the petals are much reduced in size, colour- 
ess, and tolded over the interior organs. The fila- 
ments of the ten stamens are united into a tube, and 



i, isco, p. i(;8. 



CLEIBTOGAUIO FLOWEBS. Chaf. VIII 

this U not the case, according to Von Mohl, with the 
oleistogamic Sowers of other Leguminosx, Five ol 
the stamens are destitute of anthers, and alternate with 
the five thus provided. The two cells of the antbers 
are minute, rounded and separated from one anothei 
by connective tissue; they contain but few pollen- 
grains, and these have extremely delicate coala. The 
pistil is hook-«haped, with a plainly enlarged stigma, 
which is curled down, towards the anthers ; it there- 
fore differs much from that of the perfe-ct flower. 
During the year 1867 no perfect flowers were pro- 
duced, but in the following year there were both 
perfect and oleistogamic ones. 

Ononis mimiiisaima. — My plants produced both per- 
fect and clcistogamic flowers ; but I did not examine 
the latter. Some of the former were crossed with 
pollen from a distinct plant, and six capsules thus ob- 
tained yielded on an average 3-66 seeds, with a maxi- 
mum of 5 in one. Twelve perfect flowers were marked 
and allowed to fertilise themselves spontaneously under 
a net, and they yielded eight capsules, containing on 
an average 2*38 seeds, with a maximum of 3 in one. 
Fifty-three capsules produced by the cleistogamic 
flowers contained on an average 41 seeds, so that 
these were the most productive of all ; and the seeds 
themselves looked finer even than those from the 
crossed perfect flowers. According to Blr. Bentham 
0, parmfiora likewise bears cleistogamic flowers ; and 
he informs me that these flowers are produced by all 
three species early in the spring ; whilst the perfect 
(mes appear afterwards, and therefore in a reversed 
order compared with those of Viola and Oxalis. Some 
of the species, for instance Ononis columnas, bear a 
fresh crop of cleistogamic flowers in the autumn. 

LatJiynts vissoha npparently offurs a case of the first 



•I 




IMPATIENB. 



3^7 



► Stage in the production of cleiatogamic floners, for on 

I plants growing in a state of natiire, many of the flowers 

I never expand and yet produce fine pods. Some of 

the buds are so large that they seem on the point of 

>' expansion ; others are much smaller, but none so small 

I aa the true cleistogamic flowers of the foregoing 

I flpeciea, Aa I marked these buds with thread and 

examined them daily, there could he no mistake about 

their producing fruit without having expanded. 

Several other Leguminous genera produce cleisto- 
gamic flowers, OS may be seen in the previous list ; hut 
.much does not appear to be known about them. Von 
Mohl says that their petals are commonly rudimentary, 
that only a few of their anthers are developed, their 
filaments are not united into a tube and their pistils 
are hook-shaped. In three of the genera, namely Vicia, 
Amphicarpffia, and Voandzeia, the cleiatogamic flowers 
are produced on subterranean stems. The perfect 
flowers of Voandzeia, which is a cultivated plant, are 
said never to produce &uit ;■ but we should remember 
how often fertility ia aS'ected by cultivation. 

Impatieiu fvlva. — Mr. A. W. Bennett haa published 
an excellent deacription, with figures, of this plant.t 
He shows that the cleistogamic and perfect flowers 
differ in structure at a very early period of growth, so 
that the existence of the former cannot be due merely 
to the arrested development of the latter, — a conclusion 
which indeed follows from most of the previous de- 
scriptions. Mr. Bennett found on the banks of the Wey 
that the plants which hore cleiatogamic flowers alone 
were to thoee bearing perfect flowers as 20 to 1 ; but 



• CotTwi Ae MbUo ('Jounrnl African plant, which U BOinotiine* 

timi. Buo. Dot.' vol. Ki. ISfO. p. oultimiteJ in Brarii, 

S50 pnrticularly sttouded to the t * Jnumul Lina. Soc. BoI.'tdI 

ILiwcring kud fruiting of [bis liii. 1B72, p. 147. 



328 C1.EIST0QAMIC FLOWERS. Ciiai-. \1U. 

\\a iiliouKl ictuembcr that this ia a naturalised species. 
The in?rfeot flowers are usually barren in England ; but 
Prof. Asa Gray writes to me that after midsummer in 
tito United Statcss some or many of them jiroduca 
ciipsulcs. 

Impatieni noli-m«4anflere. — I can add nothing of im- 
portiince to Von Jlohl's description, excepting that 
one of the rudimentary petals shows a vestige of a 
nectary, as Mr. Bennett likewise found to be the case 
with I.fidva. As in this latter species all five stamens 
produce some pollen, though small in amount ; a 
single anther contains, according to Von Molil, not 
more than 50 grains, and these emit their tabes 
while still enclosed within it. The pollen-grains of the 
perfect flowers are tied together by threads, but not, 
80 as far 03 I could see, those of the cleistogaraic 
flowers ; and a provision of this kind would here liave 
been useless, &s the grains can never be transported 
by insects. The flowers of /. hahamna are visited by 
humble-bees,' and I am almost sure that this is the 
case with the perfect flowers of/, noli-'me-tanyere. From 
the perfect fiowers of this latter species covered with 
a net eleven spontaneously self-fertilised capsules were 
produced, and these yielded on an average 3 ■45 seeds. 
Some perfect flowers Tvdth their anthers still containing 
an abundance of pollen were fertilised with pollen from 
a distinct plant ; and the three capsules thus produced 
contained, to my surprise, only 2, 2, and 1 seed. As 
I. hahamina is proterandrous, so probably is the pre- 
sent species ; and if so, cross-fertilisation was eflected 
by me at too early a period, and this may accotint for 
the capsules yielding so few seeds. 

Drosera rotundi/olia. — The first flower-steois i 




CLEISTOGAMIO FLOWEHS. 



329 



were thromi up by some plants in my green-house 
bore only cleistogamic flowers. The petals of small 
Bize remained permanently closed over the repm- 
ductiye organs, but their white tips could just bj 
813611 between the almost completely closed sepala. 
The pollen, which was scanty in amount, but not so 
scanty as in Viola or Oxalis, remained enclosed 
within the anthers, whence the tubes proceeded and 
penetrated the stigma. As the ovarium swelled the 
little withered corolla was carried upwards in the 
form of a cap. These cleistogamic flowers produced 
an abundance of seed. Later in the season perfect 
flowers appeared. With plants in a state of nature the 
flowers open only in the early morning, as I have been 
informed by Mr. Wallis, who particularly attended to 
the time of their flowering. In the case of D. Anglica, 
the still folded petals on some plants in my green- 
house opened juat sufficiently to leave a minute 
aperture ; the anthers dehisced properly, but the 
pollen-grains adhered in a mass to them, and thence 
emitted their tubes, which penetrated the stigmas. 
These flowers, therefore, were in an intermediate con- 
dition, and could not be called either perfect or 



A few miscellaneous observations may bo added 
with respect to some other species, as throwing light 
on our subject. Mr. Scott states ' that Erantkemum 
ajtibiffuum bears three kinds of flowers, — large, con- 
spicuous, open ones, which are quite sterile, — others 
of intermediate size, which are open and moderately 
fertile — and lastly small closed or cleistogamic ones, 
which are perfectly fertile. Ruellia tuherosa, likewise 
one of the Acanthacete, produces both open and cleis- 

■ Jnnrnsl of Balnnf,' London, now aeries, vol. i. 1872, pp. lGl-4. 



330 CLEISTOGAMIO FLOWERS, CuAr. VIII. 

togainic flowers ; the latter yield from 18 to 24, whilst 
the former only from 8 to 10 seeds ; these two kinds of 
flowers are produced simultaneously, whereas in severai 
other members of the family the cleistogamic onea 
appear only_ during the hot season. According to 
Totrey and Gray, the North American species of He- 
lianthemum, when growing in poor soil, produce only 
cleistogamic flowers. The cleistogamic flowers of 
Speoularia perfoliata are highly remarkable, aa they 
are closed by a tympanum formed by the rudi- 
mentary corolla, and without any trace of an open- 
ing. The stamens vary from 3 to 5 in number, 
as do the sepals.* The collecting hairs on the pistil, 
which play so important a part in the fertilisation 
of the perfect flowers, are here quite absent. Dra. 
Hooker and Thomson statet that some of the Indian 
species of Campanula produce two kinds of flowers ; 
the smaller ones being borne on longer peduncles 
with differently formed sepals^ and producing a more 
globose ovary. The flowers are closed by a tym- 
panum like that in Specularia. Some of the plants 
produce both kinds of flowers, others only one kind ; 
both yield an abundance of seeds. Professor Oliver 
adds that he has seen flowers on Campanula colorala 
in an intermediate condition between cleistogamic and 
perfect ones. 

The solitary almost sessile cleistogamic flowers pro- 
duced by Monochoria vaginalis are differently protected 
from those in any of the previous cases, namely, within 
" a abort sack formed of the membranous spathe, 

• Von Mohl, 'Bot. Zeitiing,' of the perfett flower ia mosOj 

1803, pp. 314 imd 323. Dr. Broro- 5-cleft. 

fl-'ld (' PhjtologiBt,' vol. iiL p. t 'Journal Lion. Soc' vol, iL 

530} also remarks that the crIjx 1857, p 7. Seo also Prnfessm 

of tUe clfiatogtttnic flowpra is Oliver in ■ Nat. Hlot, BcTiow 

aenall; only S-clcft, wliile that 1SU2, p. 2d0. 



d 



CLEISTOGAMIC PLOWEKS. 



33J 



i-witbout any opening or fissure." There is only a 

Miugie fertile stamen; the style is almost obsolete, 

Vwith the three stigmatic surfaces directed to one side. 

Both the perfect and cleistogamic flowers produce 

seeds,* 

The cleiatogamio flowers on some of the Jlal- 
pighiaceie seem to be more profoundly modified than 
those in any of the foregoing genera. According to 
A. de Juasient they are differently situated from the 
perfect flowers ; they contain only a single stamen, 
instead of 5 or 6 ; and it is a strange fact that this 
particular stamen is not developed in the perfect 
flowers of the same species. The style is absent or 
nidimentary ; and there are only two ovaries instead 
of three. Thus these degraded flowers, as Jussieu 
remarks, " laugh at our classifications, for the greater 
number of the characters proper to the species, to the 
genus, to the family, to the class disappear." I may 
add that their calyces are not glandular, and as, 
according to Kemer,} the fluid secreted by such 
glands generally serves to protect the flowers from 
crawling insects, which steal the nectar without aiding 
in their cross-fertilisation, the deficiency of the glands 
in the cleistogamic flowers of these plants may perhaps 
be accounted for by their not requiring any such 
protection. 

As the Aaclepiadous genus Stopelia is said to pro- 
c dace cleistogamic flowers, the following case may be 
l-'worfli giving. I have never heard of the perfect flowers 
met Soya carnosa setting seeds in this country, but some 
Jeapsules were produced in Mr. Farrer's hot-house ; 



' Dr. Kirk, 'Jnurn. Lino. 8 
I Tiii. lew, p, 147. 
\ 'AroLiTcadu Mos^am,' b 
a. I843,pp. 35 -38,82-86, 588.3 



t 'DiuScUalzmittclderBliithon 
geg«n aaberafeae Go^li-,' 18JiJ, 
p. 25. 



33-2 



CI,EI8TOGAMI0 FL0WEE8. CuAt VII 



ftud tlie gardener detected that they were the product 
of minute bud-like bodies, three or four of which 
could sometimes be found on the same umbel with the 
perfect flowers. They were quite closed and hardly 
thicker than tbeir peduncles. The sepals presented 
nothing particular, but internally and alternating 
with them, there were five small flattened heart-shaped 
papillae, like rudiments of petals ; but the homological 
nature of which appeared doubtful to Mr. Bentham 
and Dr. Hooker. No trace of anthers or of stamena 
could be detected ; and I knew from having examined 
many cleistogamic flowers what to look for. There 
were two ovaries, full of ovules, quite open at their 
upper ends, with their edges festooned, but with no 
trace of a proper stigma. In all these flowers one of 
the two ovaries withered and blackened long before 
the other. The one perfect capsule, 3^ inches in 
length, which was sent me, hod likewise been de- 
veloped fi-om a single carpel. This capsule con- 
tained an abundance of plumose seeds, many of which 
appeared qmt« sound, but they did not germinate 
when sown at Kew. Therefore the little bud-like 
flower which produced this capsule probably was aa 
destitute of pollen as were those which I examiued. 

Junaua hu/onius and Sordeum. — All the species 
hitherto mentioned which produce cleistogamic 
flowers are entomophilouB ; but four genera, Juncus, 
Hordeum, Cryptostachys, and Leeraia are anemophi- 
lous, Juncus hufonius ia remarkable' by bearing in 
parts of Eussia only cleistogamic flowers, which con- 
tain three instead of the six anthers found in the 
perfect flowers. In the genus Hordeum it has been 



'■' '"*l^ 



■. Yllt LEEBSIA. 333 

shown by Delpino" that the majority of the flowers are 
cleiatogamic, some of the others expanding and ap- 
parently allowing of cross-fertilisation. I hear from 
Fritz Miilier that there is a grass in Southern Brazil, 
in which the sheath of the uppermost leaf, half a 
metre in length, envelopes the whole panicle ; and 
this sheath never opens until the self-fertilised seeds 
are ripe. On the roadside some plants had been cut 
down, whilst the cleiatogamic panicles were develop- 
ing, and these plants aftenvards produced free or un- 
enclosed panicles of small size, bearing perfect flowers. 
Leereia oryzaidsa. — It has long been known that 
this plant produces cleistogaraic flowers, but these were 
first described with care by M. Duval-Jonve.t I pro- 
cured plants from a stream near Keigate, and cultivated 
them for several years in my green-house. The cleia- 
togamic flowers are very small, and usually mature 
their seeds within the sheaths of the leaves. These 
flowers are said by Duval-Jouve to be filled by slightly 
viscid fluid ; but this was not the case with several 
that I opened ; but there was a thin film of fluid 
between the coats of the glumes, and when these were 
pressed the fluid moved about, giving a singularly 
deceptive appearance of the whole inside of the flower 
being thus filled. The stigma is very small and the 
filaments extremely short ; the anthers are less than 
■^ of an inch in length or about one-tliird of the 
length of those in the perfect flowers. One of the 
three anthers dehisces before the two others. Can 
I thifl have any relation with the fact that in some other 



' ' Bollstdiii del Cniiiizio agra- 
tk) Farmense.' Marzn e AprilH, 
1871. AnabBtnictonbUTBjmble 

G peril giteu in 'BoL ZEJtuni;,' 
71. p. 037. Seciil=oHiIJoUmud 



oiiUordenni,ia'MDnaUl*rielit d. 
K. Akiid. 8erlio,'Ocl. 1872, p. 760, 
t 'Kail. EkiL Soc de Fmnco, 
Coin. I. 1863, p. 194. 



334 



CLEISTOQAMIO FLOWEES. Chap VUB 



epecies of Leeraia only two stamens are fally dfr-* 
viiiupeil?* The antherB shed their pollen on the 
stigma ; at loast in one instance this was clearly the 
case, and by tearing open the anthers under water_ 
the grains were easily detached. Towards the apex o " 
the anther the grains are arranged in a single row ana 
lower down In two or tliree rows, so that they could h 
wjiinted ; and there were about 35 in each cell, or 70'1 
in the whole anther ; and this is an astonishingly small I 
number for an anemophilous plant. The grains havsJ 
very delicate coats, are spherical and about -7^55 
an inch ("0181 mm.), whilst those of the perfect flowei 
are about t-^'^q of an inch ("0254 mm.) in diameter. 

M. DuFat-Jouve states that the panicles very rareljl 
protrude from their sheaths, but that when this do€ 
happen the flowers expand and exhibit well-developei 
ovaries and stigmas, together with full-sized antheif 
containing apparently sound pollen ; nevertheles 
flowers are invariably quite sterile. Schreiber had pce^^ 
viously observed that if a panicle is only half protruded, 
this half is sterile, whilst the still included half is 
fertile. Some plants which grew in a large tub of 
water in my green-house behaved on one occasion in a ~ 
very different manner. They protruded two verj 
large much-branched panicles ; but the florets nevel 
opened, though these included fully developed stig- 
mas, and stamens supported on long filaments with 
large anthers that dehisced properly. If these florets 
had opened for a short time imperceived by me and 
had then closed again, the empty antheis would 
have been left dangling outside. Nevertheless they 
yielded on August 17th an abundance of fine ripi 
aeeds. Here then we have a near approach to tha 



• Am Gtay, ' Maniml of Hot. of United Stitca," ISflC, p, 54a 



A. 335 

aingle case aa yet kuown' of this grass produciDg in a 
state of nature (in Grermany) perfect flowers which 
yielded a copious supply of fruit. Seeds from the eleis- 
togamic flowers were sent by me to Mr. Scott in 
Calcutta, who there cultivated the plants in vai'ioiia 
ways, but they never produced perfect flowers. 

In Europe Leersia oryzoides is the sole representa,- 
tive of its genus, and Duval-Jouve, after esamLning 
several exotic species, found that it apparently is the 
sole one which bears cleistogamic flowers. It ranges 
from Persia to North America, and specimens from 
Pennsylvania resembled the European ones in their 
concealed manner of fmctification. There can there- 
fore be little doubt that thia plant generally propa- 
gates itself throughout an immense area by cleisto- 
gamic seeds, and that it can hardly ever be invigorated 
by cross-fertilisation. It resembles in this respect 
those plants which are now widely spread, though they 
increase solely by asexual generation.! 

Concluding Remarks on Gleistogamio Flowers. — That 

these flowers owe their structure primarily to the 

arrested development of perfect ones, we may infer 

from such cases as that of the lower rudimentary petal 

in Viola being larger than the others, like the lower 

lip of the perfect flower, — from a vestige of a spur in 

L tiie cleistogamic flowers of Impatiens, — from the ten 

lumens of Ononis being united into a tube,— and 

Mother such structures. The same inference may be 

drawn from the occurrence, in some instances, on the 

same plant of a series of gradations between the 

cleistogamic and perfect flowers. But that the former 

[_0W6 their origin wholly to arrested development is 

* I}r. Aaolieraan, 'Hot. Zcituiig,' eases In ray 'Variation niiikr 
ifil- n MH. DomeBticiitioii,' ck ivUi.— iuJ 

i^ilil. vol. ii. p. 153. 



I 
I 



336 COSCLDDIHG BBMAEK3 Cbap.TIIi 

by no means the case ; for various parta have been 
specially modified, so as to aid in the self-fertiJisatiou 
of the flowers, and as a protection to the pollen ; for 
instauoe, the hook-shaped pistil in Viola and in some 
other genera, by which tho stigma is brought close 
to tlie fertile anthers, — the radimentary corolla of 
Specularia modified into a perfectly closed tympanum, 
and the sheath of Monocboria modified into a closed 
sack, — the excessively thin coats of the pollen-grains, 
— the anthers not being all equally aborted, and other 
such cases. Moreover Mr. Bennett has shown that 
the buds of the cleistogamic and perfect flowers of 
Impatiens differ at a very early period of growth. 

Tho degree to which many of the most important 
organs in these degraded flowers have been reduced 
or even wholly obliterated, is one of their most re- 
markable peculiarities, reminding us of many parasitic 
animals. In some eases only a single anther is left, 
and thia oontaiiis but few pollen-graina of diminisheJ 
size ; in other cases the stigma has disappeared,, 
leaving a simple open passage into the ovarium. Itj 
is also interesting to note the complete loss of trilli 
jwints in the structure or functions of certain parts, 
which though of service to the perfect flowers, are of 
none to the cleistogamic ; for instance the collecting 
hairs on the pistil of Specularia, the glands on the 
calyx of the MalpighiaeeEe, the nectar-secreting ap- 
pendages to the lower stamens of Viola, the secretion 
of nectar by other parts, the emission of a sweet odour, 
and apparently the elasticity of the valves in the 
buried capsules of Viola odarata. We here see, 
throughout nature, that as soon as any part or 
character becomes superfluous it tends sooner or latepj 
to disappear. 

Aiiother peculiarity in these flowers is that thi 



i 



ON CLEIBTOQAMIC FLOWERS. 



337 



I 



pollen-grains generally emit their tubus whilst etilL 
enclosed within the anthers ; but this is not so re- 
markable a fact as was formerly thought, when the 
caae of Asclepias was alone known.* It is, liowever, 
a wonderful sight to behold the tubes directing them- 
selves in a straight line to the stigma, when this 
is at some little distance from the anthers. As 
soon as they reach the stigma or the open passage 
leading into the ovarinm, no doubt they penetrate it, 
guided by the same means, whatever these may be. 
as in the case of ordinary flowers. I thought that 
they might be guided by the avoidance of light : some 
pollen-grains of a willow were therefore immersed in 
an extremely weak solution of honey, and the vessel 
was placed so that the light entered only in one di- 
rection, laterally or from below or from above, but tho 
long tubes were in each case protruded in every 
jmssible direction, 

As cleistogamic flowera are completely closed they 
are nec^sarily self-fertilised, not to mention the 
absence of any attraction to insects; and they thus 
differ widely from the great majority of ordinary 
flowers. Delpino believcBt that cleistogamic flowers 
Iiave been developed in order to ensure the production 
of seeds under climatic or other conditions which tend 



* Tlie coBb of ABtik'pias was de- 
■ori^Niil by li. BrowD. Baillon as- 
lerta (' Adaae'iuia,' torn ii. IS62. 
p. 58) that with man; planlB thd 
tubas are emitltd I'roni pollan- 
graine whicb have not eoiue into 
.-untaat with thu stigma ; and that 
thtj' ma J be seen ad vanomg hoH- 
zonlally tliruugh the air towards 
Ibe stii;ms. I have obBorvE^ the 
•ulnaiDa of the tnbsB boiu the 



pollen-masaeB wliilst still within 
tlie anthers, in three widely diatioot 
Orohidean genera naniely Aceraa, 
Molaxia, and Neottia : see ' The 
Varioua CoiilrivanciB by which 
Orchids are Feitiliaed,' 2nd edit. 
p. 238. 



338 



CONCLUDING BEMABKS 



to prevent the fertilisation of the perfect flowera. I d 
not doubt that this holds good to a certain limi ted extenQ 
but the production of a large supply of seeds with litt' 
consumption of nutrient matter or expenditure of vita! ' 
force is probably a far more efficient motive power. 
The whole flower is much reduced in size; but what 
is much more important, an extremely small quantity 
of pollen has to be formed, as Done is lost through the 
action of insects or the weather ; and pollen contains 
much nitrogen and phosphorus. Von Mohl estimated 
that a single cleistogamic anther-i;eLl of Oxalis aceto- 
sdla contained from one to two dozen pollen-graina ; 
we will say 20, and if so the whole flower can have 
produced at most .400 grains ; with Impatiens the 
whole number may be estimated in the same manner 
at 250 ; with Leersia at 210 ; and with Viola tiana at 
only 100. These figures are wonderfully low com- 
pared with the 213,600 pollen-graina produced by a 
flower of Leontodon, the 4,863 by an Hibiscus, or the 
3,654,000 by a Pieony.* We thus see that cleisto- 
gamic flowers produce seeds with a wonderfully small' 
expenditure of pollen ; and they produce as a general 
rule quite as many seeds as the perfect flowers. 

That the production of a large number of seeds i 
necessary or beneficial to many plants needs no evi*^ 
dence. So of course is their preservation before they 
are ready for germination ; and it is one of the many 
lemarkable peculiarities of the plants which bear 
cleistogamic flowers, that an incomparably larger pro- 
jjortion of them than of ordinary plants bury their 
young oTiiries in the ground ; — an action which it 
may be presumed serves to protect them from beiiu 



1 niyEirc-cUd 



f CHAr. VIII. ON CLEISTOGAMIO FLOWERS. 



339 



I 

I 



devoured by birds or other enemies. But tiiia advan- 
tage ia accompanied by the loss of the power of wide 
diasemination. No less than eight of the genera 
in the list at the beginning of this chapter include 
species which act in this manner, namely, several 
kinds of Viola, Oxalis, Vandellia, Linaiia, Commelina, 
and at least three genera of Leguminoaa?. The seeds 
also of Leersia, though not buried, are concealed in 
the moat perfect manner within the aheaths of the 
leaves. Cleistogamic flowers possess great facilities 
for burying their young ovaries or capsules, owing to 
their sntall size, pointed shape, closed condition and 
the absence of a corolla ; and we can thus understand 
how it is that so many of them have acquired tliis 
curious habit. 

It has already been shown that in about 32 out of 
the 55 genera in the list just referred to, the perfecl 
flowers are irregular ; and this implies that they Lave 
been specially adapted for fertilisation by inaecta. 
Moi-eover three of the genera with regular flowers are 
adapted by other means for the same end. Flowers 
thus constructed are liable during certain seasons to 
be imperfectly fertilised, namely, when the proper 
insects are scarce ; and it is difficult to avoid the 
belief that the production of cleiatogamic flowers, 
which ensures under all circumstances a full supply 
of seed, has been in part determined by the perfect 
flowera being liable to fail in their fertilisation. But 
if this determining cause be a real one, it must be of 
subordinate importance, as four of the genera in the 
list are fertilised by the ivind ; and there seems no 
reason why their perfect flowers should fail to be 
fertilised more frequently than those in any other 
anemophiloua genus- In contnist with what we here 
Bee with respect to the large proportion of the perfect 



CONOLUUING EEMARK8 



I 



310 

(lowers being irregular, one genua alone out of tlie 38 
heterostyled genera described in the previous chapters 
bears such flowers ; yet all these genera are absolutely 
dependent on insects for their legitimate i'ertiliaation, 
1 know not bow to account for this difference in the 
proportion of the plants bearing regular and irregular 
flowers in the two classes, unless it be that the hetero- 
styled flowers are already so well adapted for cross-fer- 
tilisation, through the position of their stamens and 
pistils and the difference in power of their two or . 
three kinds of pollen, tbat any additional adaptation; 
namely, through the flowers being made irregularj 
has been rendered superfluc 

Although cleistogamic flowers never fail to yield 
a largo number of seeds, yet the plants bearing them 
usually produce perfect flowers, either simultaneously 
or more commonly at a different period ; and thes 
are adapted for or admit of cross-fertilisation. From 
the cases given of the two Indian species of Viola 
which produced in this coimtry during several yea 
only cleistogamic flowers, and of the numerous plantd 
of Vandellia and of some plants of Ononis whidTl 
behaved during one whole season in the same r 
it appears rash to infer from such cases as that of 
Salvia deistogama not having produced perfect flowers 
during five years in Germany," and of an Aspicarpa 
not having dono so during several years in Paris, that 
these plants would not bear perfect flowers in their 
native homes. Von Mohl and several other botanists 
have repeatedly insisted tbat as a general rule the 
perfect flowers produced by cleistogamic plants are 
sterile ; but it has been shown under the h>;ad of t 
several species that this is not the case. The j 



' liot Zeit; 1871, p. nss 



■ C«AP. VIII. ON CLEI3T0GAJIIC FLOWEKt 



S41 



■lowers of Viola are indeed sterile unless they are 

Iviaited by bees ; but when thus Tiaited they yield the 

KfuU number of seeds. As far as I have been able to 

discover there ia only one absolute exception to the 

rule that the perfect flowers are fertile, namely, that 

of Voandzeia ; and in this case we should remember 

that cultivation often affecta injuriously the repro- 

fductive organs. Although the perfect flowers of 

f Leersia eometimes yield seeds, yet this occurs so 

I rarely, as far as hitherto observed, that it practically 

L forms a second exception to the rule. 

As cleistogamic flowers are invariably fertilised, and 
' as they are produced in large numbers, they yield 
altogether a much larger supply of seeds than do 
the perfect flowers on the same plant. But the latter 
flowers will occasionally be cross-fertilised, and their 
ipring will thus be invigorated, as we may infer 
[. from a wide-spread analogy. But of such invigoration 
I I have only a small amount of direct evidence : two 
crossed seedlings of Ononis minvtissima were put into 
competition with two seedlings raised from cleisto- 
gamic flowers ; they were at first all of equal height ; 
the crossed were then slightly beaten ; but on the fol- 
lowing year they showed the usual superiority of their 
class, and were to tlie self- fertilised plants of cleisto- 
gamic origin as 100 to 88 in mean height. With 
Vandeilia twenty crossed plants exceeded in height 
twenty plants raised from cleistogamic seeds only by 
a little, namely, in the ratio of 100 to 94. 

It is a natural inquiry how so many plants belong- 
ing to varioiis very distinct families first came to have 
Itlie development of their flowers arrested, so as ulti- 
mately to become cleistogamic. That a passnge from 
the one state to the other is far from difRcidt is shown 
by the many recorded cases of gradations between the 



o 

Iti 
■ 
: 

a 

t 

J: 



L 



342 CONCLtmraQ BEMABE8 Chap. VIM 

I wo statea on the snme plant, in Viola, Oxalis, Biophj^^ 
tiim. Campanula, &c. In the several apeciea of Viola 
the varioiia parts of the flowers have also been modified 
in very different degrees. TJjose plants nhich in their 
own country produce flowers of full or nearly full size, 
but never exjMind (as with Thelymitra), and yet set 
fruit, might easily be rendered cleiatogamic, Laihyrua 
niasdia seemfl to be in au incipient transitiounl state, 
as does Drosera Anglica, the flowers of which are not 
[wrfectly closed. There is good evidence that flowers 
sometimes fail to expand and are somewhat reduced 
in size, owing to exposure to unfavourable conditions, 
but still retain their fertility unimpaired. Linnffius 
observed in 1753 that the flowers on several plants 
brought from Spain and grown at Upsala did not 
show any corolla and yet produced seeds. Aaa 
Gray has seen flowers on exotic plants in the North- 
ern United States which never expanded and yet 
fruited. With certain English plants, which bear 
flowers dnring nearly the whole year, Mr. Bennett 
found that those pro<luced during the winter season 
were fertilised in the bud ; whilst with other speciea 
having fixed times for flowering, but " which had 
been tempted by a mild January to put forth a few 
wretched flowers," no pollen was discharged from the 
anthers, and no seed was formed. The flowers of 
Lygimaehia vulgaris if fully exposed to the sun expand 
jiroperly, while those growing in shady ditches have 
smaller corollas which open only slightly ; and these 
two forms graduate into one another in intermediate 
stations. Herr Bouche's observations are of especial 
interest, for ho shows that both temperature and the 
amount of light affect the size of the corolla; and he 
gives measurements proving that with some plants 
the corolla is (liminished by the increasing cold and 



M 



I 

I 



[ CLEISTOGAMIC FLOWEES. 



343 



daikness of the clianging season, whilst with others 
it is diminished by the increasing heat and light.* 

The belief tliat the first step towards flowers being 
pondered cleistogamic was due to the conditions to 
which they were exposed, is supported by the fact 
of various plants belonging to this class either not pro- 
ducing their cleistogamic flowers under certain condi- 
tions, or, on the other hand, producing them to the 
complete exclusion of the perfect ones. Thus some 
species of Viola do not bear cleistogamic flowers when 
growing on the lowlands or in certain districts. Other 
plants when cultivated have failed to produce perfect 
flowers during several successive years ; and this is 
the case with Juncus bufoniua in its native land uf 
Bussia. Cleistogamic flowers are produced by some 
species late and by others early in the season ; and this 
agrees with the view that the first step towards their de- 
.velopment was due to climate ; though the periods at 
which the two sorts of flowers now appear must since 
have become much more distinctly defined. We do not 
know whether too low or too high a temperature or the 
amount of light acts in a direct manner on the size of 
the corolla, or indirectly through the male organs being 
first affected. However this may be, if a plant were 
prevented either early or late in the season from fully 
expanding its corolla, with some reduction in its size, 
but with no loss of the power of self-fertilisation, then 
natural selection might well complete the work and 



* PortliealnteiueDtbyLLnnnus. 
tee UoLl iu ' Hot. Zeitiuig.' 18U3, 
p. n'27. Abb Gray, 'Ameiican 
Jouiuul of Bcience,' 2ud siTieii, 
voL illLi, IBiiS, p. 105. Beniu-U 
in 'N«ture,' Nov. 186D. p. 11. 
Tbe Bev. U. Uenalow alao says 
(■ G&rJeaor'H Ctiroiiicle,' ls77, p. 



p. 543) " Ihat nlien the .mtumn 
draws on, anil hiibitually in waltir 
for hucli t>r iiur wild fiowcn ae 
bl(iBaomaUliBt£«Bsciii,"theflowert 
ars belf-fertilised. On LysiniQ- 
oliio, U. Miali'r. ■Nature/ fiBjit 
187a, p. 433. Bouche, ■SiteuiiB.. 
bprLht dor Qcaell. Nulurfuncu. 
FcuiuiJe ■ Oct. 1874,11. 9U. 



ai4 



GENEBAL C0SCXUSI0S8. 



tcnJer it strictly clc^istogamic. The raiiotis oigans 
^oiild also, it is probable, be modified by the pecnliai 
coaditions to which tbey are subjected witliin a com- 
pletely closed flower ; also by the principle of corre- 
lated growth, and by the tendency in all reduced 
organs finally to disappear. The result would be the 
production of cleistogamic flowers such as we now 
see them ; and these are admirably fitted to yield 
copious supply of seed at a wonderfully small cost 
the plant. 

I will now sum up very briefly the chief conclusii 
which seem to follow from the observations given 
this volume. Cleistogamic flowers aflTord, as just 
Htuted, an abundant supply of seeds with little ex- 
peuditure ; and we can hardly doubt that they have 
had their stnicture modified and degraded for this 
special purpose ; perfect flowers being still almost al- 
ways produced so as to allow of occasional cross-fertilisa- 
tion. Hermaphrodite plants have often been rendered, 
monoecious, dioecious or polygamous ; but as the sepor. 
ration of the sexes would have been injurious, had notj 
pollen been already transported habitually by in- 
sects or by the wind from flower to flower, we may 
assume that the process of separation did not coi 
mence and was not completed for the sake of 
advantages to be gained from cross-fertilisation. Tl 
sole motive for the separation of the sexes whii 
occurs to me, is that the production of a great number 
of seeds might become superfluous to a plant nnder 
changed conditions of life ; and it might then be highly 
beneficial to it that the same flower or the same indi- 
vidual should not have its vital powers taxed, under 
the struggle for life to which all organisms are sub- 
jected, by producing both pollen and seeds. With 



i 




GENEEAL UO»ULUSIONS. 



S45 



I 



respect to the plants belonging to the gyno-dioecious 
sub-class, or thoso which co-exist as hermaphrodites 
and females, it has been proved that they yiehl a 
much larger supply of seed than they would have 
done if they had all remained hermaphrodites ; and wa 
may feel sure from the large number of seeds pro- 
duced by many plants that such production is often 
necessary or advantageous. It is therefore probable 
that the two forma in this sub-class have been sepa- 
rated or developed for this special end. 

Various hermaphrodite plants have become hetero- 
styled, ami now exist under two or three forms; and 
we may confidently believe that this has been effected 
in order that cross-fertilisation should be assured, 
For the full and legitimate fertilisation of these plants 
pollen from the one form must be applied to the 
stigma of another. If the sexual elements belonging 
to the same form are united the union is an illegiti- 
mate one and more or less eterile. With dimorphic 
species two illegitimate unions, and with trimorphic 
species twelve are possible. There is reason to believe 
that the sterility of these unions has not been specially 
acquired, but follows as an incidental result from the 
sexual elements of the two or three forms having been 
adapted to act on one another in a particular manner, 
so that any other kind of union is inefficient, like 
that between distinct species. Another and still i 
remarkable incidental result is that the seedlings 
from an illegitimate union are often dwarfed and 
more or less or completely barren, like hybrids from 
the union of two widely distinct species. 





INDEX. 



Boreiiu <Hi cowslip anil primiiMe, S7 

Bomria, 127 

Uoutbe on Panmia, 313; effect of 

tduperuture and light on uorollu, 

342 
lloavardin leiaalha. 135 
Bmuti nn Dracoeephalum, 399 
Breitenbach, W, on PrimtUa elatior, 

3i. 273 
BromSetd, Dr.. on primroBe snd 

oiJWBiip, 57; PriimHa elatior, 73; 

Specularia per/tiliafa, 3;<0 
Broun, Bobert, ou seiual oliangea, 

282 
Buokwhcat, tha oomnioa, til 



Oallha paluOrlti. 13 ^^1 

Cantpanula eolorata, 330 ^^| 

CnrdatniM ataara, 3l)7 
Caapnjy, Prof., on Jihamiiiu calhar- 

limn. 29i 
CaUieya, 313 
Chamiitoa. 292 
Oinehana inicratilia, 134 
Cleiatogumio flowers. 310; list of 

gauenv. 312 ; on tlieir uripn, 343 
Onieut aaaaliK, 307 
' jxUHttrU, 307 
CoBcoq/jiteluia, 133 ; ptilleD-graim 

of, 2SU 
Cuprorma, 235 
Cordia, 117; pistil of, 253 
OorolJo, difft-ienoe in size in tbo 

seioa of tlie name aiKH:!^-!*, 307 

30a 



O-rydalit, 146 

Gori/liii aveltana, 10 

OowBlip, the eiimiiion, 14 ; sliort- 

nnd long-Btyled, I9-'22, 56-71 
Oraloxylon formonan, 123 
Citiaker, C. W., on Plaatago laneto- 

lala, 3UG 
CnjpUalachgt, 313, 332 
Cuyhra purpurea, ItiS 



^ant^iemaot ambigawn. 329 
friDpAoruTn angiuJi/oUttm, jj(17 
ErytliTOxylura, 121 1 pollca-grams' 

250 
SSutiiymm EuTopmu, 287-293 

Eiiryale, 3t I 



Q. 

Durwin, Cbarlea. on reprodactiTe 
organs andei caltiTBtiun, 7; in- 
tercmseed plantB, 30 ; prepoleiii.-y 
of pallen, Mi; ingects fertiliBing 
Honera, TO; OejitalaalheTa graa- 
dillora, 98; Epidejidnm anA Cat- 
Vega, 313; Duuiber of pollen- 
giaina, 338 

— — -, W., oD Pidmimana anoHtti- 
fnlia, 105, 107 

Dnfuni artorea, 2S1 

Delpioo, plants TGrtilii-ed by tlio 
wind, 10; on the wulnut, 10; 
Folygonaeai, 114 ; piillen-gruina, 
250; Thf/mvM wrjiiiUuni, 290; 
dused or oleititijgBmic flowere, 
311,337; I'iolu wiurata, 317 

Dianlhui baTbaliu, 3i> 

Dickie, Dr., on £Wopionim anguiti- 
/oliutn, 307 



73 

Draeoeephiilam Moldaviaim, 299 
Drotra Anqlica. 329, ^2 

Tvtunilifolia, 328 

Dnyal-JoQVBi M., on Oryplutladiyii, 

313; Leeriia urytoida. 333, it34 
^_ Dyer, Thiselt'in, on Saltia Hur- 



0,t. 307 



Fnromeo, 128; pollen-grainB of, 1 W 
FitzgenUd, Mr., on TlidymUra, :il3 
Fonytltia atapeiiia, 117; etninuiig, 

252 
— — tiiridtitima, 1 17 
Fragaria Chiloetuu, 293 
(lattor, 293 



Fraxiims acvcltior, 1 



Gnliam crudalum, 2Sfi 

Ga-rtrier ou tUe Htiirillty of union* 
between diBtinot Bpeciea. 20; J'ri- 
ntula valgarii uxd verit, 58, Ci:'; 
hybrid KerftMsunu, 76. 77, 80 : 
prepottnw) of pollen, 241; varin- 
tiou in the sexual powers i-f 
pltiLitd, 207 ; oontKbeBoentuntheiD, 
193, 283 

aratianeiE, 115 

OeTtxniaeans, 163 

Qeramam lylvalieam, SOS 

Getneria pendalina, 201 

Oilia aggngata, 116 

ermmopifolia, 1 19 

mieranlha, 1 19 

nudimulit, 1 1 B 

pwiflWia. 118 

(iUlibert on MenyanOiet, 311 

GljtrioBB LQy. ti.e, lie 

Qodron od lijbrid Primiilai, 55 

Grey, Prof, Asa, prupoBca the t«rm 
heterogone or heierogoaomi, 2 ; on 
Linum. 101: Le'loosmia Bur- 
titliiaaa luid asumJNiila, 114; 
Fortuihia tuj^ma, 117; G'lia 
pnyUlla, Mi: U. mivKOpifiiia, 



]I9: Phlox autm^ilo, IIQ; .VII- 
rkoflo reiieni, 123 1 liclcrriHtjIoil 
plSDts, S41 : Ooproinna, U85 ; Hw 
oiiymui, 2S7; JUamNlu latieeo- 
lilM, 205, 2SI] : h'pigioa rtpeiw, 
2m: llrx DORM, »)(<: Plant<>[ri> 
■udfa, 3<i7; O/vboiAiuaud Nyeta- 
„''ni'a, 3l!i: Imtatitm/idva,ii2S: 
LeetMia, 'ASi ; olaistogumic flowon, 



Hurt, Mr., on Sepela gleehomn, 301 
HnutUiia Btrawbi^iy.'tlic 293 
Hedijolit. 133 
Henalow, Rev. Prof,, on hybriii PrJ- 

Hinalow, Hot, G., on Bowera »Blf- 

ffrtilisfd dutiiig the winter, 'liiS 

Horbert, Dr., on hybrid Primldai, 

ei 

Heteroetyled plsnta. illegitimate ofT- 
springof, 1S8-243; eBHeutlal clia- 
rvctor of, ZH; mciunsry of tlie 
diflbrencea of fertility between 
legitimately and illegitimately fer- 
tiltaed plunts, 246; diameter ••! 
polleii-giniiia, 249 ; BizeoFsiitlierK, 
Btructure of Btigmit, 252; liat of 
eenetB. 2SS; adtontages daririd 
from HetemBtylism, S^iS; means 
by wLich plants bocame lietero- 
s^lad, 26U : tntnamisBioii of form, 
268: eiiuftl-Btyled vuieties, 272; 
final reniacks, 275 

dimorphio plants, ll-5i, 81- 

i;w 

triuinrfiliio planla, 137-187 

Ilibim-vt, poUen-graitia, B3S 
Hildebiand, Prof., lutioducps tlie 
word " iieteroBtyled," 2 ; on tlia 
niv-lloreta of tile Gmpo'tta; 5, (i : 
i'r/iniJo Sinentii, 38, «-13, 192, 
21 T ; Unom gmndlfiorum, S6, 87 : 
L. jieremie, 92; Fvhaonaria offi- 
einalii. 101-103, 1(17, 2:19; P. 
acureii, IIU ; i'oly_ioaam fagopy- 
luiii. ill: Oxalu, i(i!), 171-174, 
nn 182, 2I1-21M, 3:;2: lirrma. 



phrodite pUnti beroniing i 

Bexual, 2S3: Hordeuni. 333 
Hnjiiostyled apocies of Primula, 41 
}lfl<>ker. Dr., on Campanula. 330 
SiinUum, 332 
I Holbma it^ala, 53, S13 
paiurfrii, 50; relative fertility, 

52; aotlifrEi uf, 252; papilln - 

Btlgma. 251 
HoatiOhia candfo, 132, 254 
Iloua camona, 831 
Hybrid Frimulai, 55-71 
Hndrangea, S, 7 



I 



Itisc aqw/uldin, 2!J7 

opaca. 208 

IllegitiiiialaoIfapriTigofhptcrostjlt^ 
plants. 188; Lyihrum talfairia. 
dwarfed slature acd irterility. 192; 
Oxalis, tmnsmiaaion of foiin to 
seedlingH, 212 ; Primida Slnemit, 
in some degree dwBj-fed, 215; 
equaUtyled yarieties, 218-223; 
FtiaiiJti valgarlt, 224 ; Imn*- 
nusaion of ftirni and colour, 22.j : 
seedlings, 227; P. verit. 228; 
dwarfed stature and sfordity, 
229-234; equal^tjled vnrieliisi, 
234-. 238; mrallcliam bot'veoci 
illegitimate icrtilisntiun and hy- 
bridism, 242 

Itlec^iram, 31 1 

/iHfuili'nu, pollen -giaim of, 3:1ft 

fcalnamino, S2S 

/'ilea, 327 

uoli-^ne~tangeTe, 



Jughtnt regia. 10 
Jussiou, A. du, 01 



Keraor, Prof., on raj-llnrets, 

cuid, 43; liylirid JbrniHof J'li'niHin, 
S3, 73; on Uae of buiia witliln 



I 



^H 849 ^^M 


^^M KIBE. 


«EnA>iTah^ ^^1 


^H tlie corolla, 128: eize of coral kin 


Linum AnetTiaatm, ff7 ^^^^H 


^^1 nule Aiveis, 303 ; u»e of glandB 


calliurlieam, 100 ^^^H 


^^H as a proteoti'in to flower)'. 3:^1 
^M Kiik, fir., on lfon»3Aorta caffi'io/fo, 


cnnftn^t/'eruin, 100 ^^^^H 


fiaoum, 81, 98 : atamena. Z^>i ^^H 


^H 331 


grand'iftirwn. 61 ; varioiia ex- ^^^| 


^H K>ioz/a. l:!e 






atomens. 1253, 254 ; sterile wltli ita ^^H 




own-form polluii, 264, 1!66 ^^^1 


^^H Knhii, Dr., on iji^istogamic flowora, 


Leicmi, 101 ^^H 


^H 3, 310, Bll: list of plunts pro- 


Mrenne, 90; torainTi of the ^^H 

BtyW 95: bog-styled lunn, 97; ^^M 




^B S : htleiraBtyled pkmt^ 244 ; Van- 


adgmo, 247 ^H 






^^B tetaflora, d!£5 






w,iialis>lmwn. 100 ^^H 


^H 


Lipotlojaa. 134 ^^H 




LytinuKiia vutgarli, 4, 342 ^^H 


^H £a[r<!r<friim(a /nil/oa, 167 


L^i;>rum (7r«f:W, 165 ^^M 
hy„opi/3{a. 168 ^H 


^H puTBifiara, 108 


^B ' rtginm, Itjg 


lolicurfu, 110. 137: powor of ^^M 


^H XolApnunitKiIia, 326,342 


matuBl fertili^tion between the ^^M 


^^H Leroq, H., on the aonimDii maple, 


three fonne, 143-157; auimnarj ^^M 


^^H 12; (iowalips end primrosea, 57; 


of reanlte, 157-163; illegitiuutlc ^^M 


^H i'nmulit Oaliur, Tl : Linum A ai- 


offspring from tlis three fiiriii:!, ^^H 


^H Iriaatm, 98 : Lylhmm hyaopi- 


im-2:>3 : i-Dn«ladin<^ muurk> i>d, ^^H 
21)3-^211; inid-eltlt^ form. ^11, ^^M 


^V /o2ia, ICS: AAomnw. 296: gyi.o- 


^™ difljeiuus plants, ZH9: Ssn6i™ 


257, 253, 2SU ; e^e-h, 248 ^H 


■Hcci'M, SOS ; VioJa odaraia. 317 


Ihymi/olia, IGS ^^H 






gnima i if. 838 




L^gi^'tt, Air., Paalederia cordaUi, 

^m 187 

^^^b L^timnle uniona, BUnimBry on tile 


^H 




JVuneflJa Ai'n'I'^r, 133 ^^M 


^H thatoftlietwoille^-itimal'iiiiiV''- 


BlapU', Ihe eomnion, 12 ^^M 


^H (nubi, 46-49: fertUity iT, eom- 


Blnralmll, W„ on Primula dulLr, ^^M 




tLthtera, Dr. Htuwt;!!, on <.ldBt(>- ^^H 


^H Leigliton, BeT. W, A., on the co^- 




fiiimio flowers, 3 ^^H 


^H UrgMm,7S 


Miixliuowicz on fnucicnte/Inio/n ^^M 


^H lnontodon. pnllen-sraine, 338 


^^M 


H L«^te»>ho», no 


SU-ehnn. Ur.. on ilUcUla, 2SSi ^H 




JUclixa dmfDWi/iin, 2U!t ^^M 




^H Lily, tlie (ilorioai, I4<-. 




Klello. C>rrea ite, on AnuUi., 312 ^H 


loD-eniiiia,250: ai.Uiura. £Si 


7«a>kit«'a, 327 ^H 


Lhutrla t,mri<t. S2S 


MfNtAa «wit'«>, 293 ^^| 


Llndley ou JTragaria tinlior. 303 


AiriuKi. 208 ^^1 


Linnnua on Frimv!a terii, culgiirii, 


JV.'>.yn„f!U, 31 1 ^^H 


^m_ and elalhr. 56 


^H I«imm anjiuli/Miiia. IW 


Iri/olM.i. 113 ^^H 



HileMla. idS 

repma, 123 

Holil, H. von 
wnwlip, 1-1 ; , 



lUe 



le ufcnrotlB in tUa 
aine (i)ieciBa, 307, 
'MH; TrifatiwmtLndAnuAU.'M'i; 
L-lristoijamic tlnweta, 814. 342; 
llxaiis aotlai^la, 321; Inpalietit 
iuili-me-langere,!i20: Spetailaria 
jur/aliata, 331) 

MvUia tepiilala. IGS 

nwefimi. lliH 

Mmiiiier, M.. on C/oIo. 313 

Afon'i'iorfa vaglnalit, 330 

Miilborr;, tlie, HI 

MUller, U., mi Viola eaniaa, 314 

IilUller, Fritx, on pollen of the VU- 
lunia. ll(j; Far^imea, I28-13U; 
rotoquaiafragram, 131 ; Nena, 
IBT; Uailu,l80,lSl: PtmledfTia, 
lNi)-t86; ttealia A^rKt, 212; 
CVinmiwoa, 292 

Mliller, H., on ibo frfqnency of 
vUitB by iosecta to tlio i'niWW- 
/er» and Cnmjimii*, 5 : on ilitihrt- 
piroy, ID ; on AtiOuipltora and 
Bmahjiliuii sucking tlio oowalip, 
22; /V;m«ii(Jn(ior, 32 : P. vfUnui, 
49: i/"r(c»i<'n jKtfturw<.Sl: UiMu 

..f rtlalim rorldity of, S2, 53 ; 
LinUBi ealhartieum, Il)U; TrJy- 
if iin'oii /uirofiyrum, 1 13 ; T/iilhiHin 
rnliBBTia. 145 ; <>n tlie ori^la of 
hoterD.-ilyliam, 203; od tlie La- 
hiala:. 2KI,30i; Th-fonatrpylUnt, 
3uUr*oW™uan'eB«'<,S0a: i'lim- 
iailo Umrmlula, 306; dze <if oo- 



n the tv 






BpeoieH, 308; Impatievi bnhn. 
in.Tia, 328; Ly'lmadUu, 343 
Uffwolit, 30S 



A'epefti pferfioma, 301 

An.i'ii nertirvnitdi, 1G7 
WJniio pnulTi'la, vnriobility in 
lengtii of BtBomus aud pLstil, 2i;i 
X^l.igini'a. 313 



(IhlmJandia. 132 

Oleoofai, 117 

OUver. Prof., on ovules of Frimla 

TCrM.1T Kiota, 318; Cantpaiiula 

onUvnta, 330 
OnoRu sofumnA 825 

nii«titiniina. 326, 341 

panrifiora, 326 

Orfqanam ntfgare, 298 
(ixaligaexlo»eaa.l8l.lS2. pistil nf, 

2 I : cldHtogamiu llnw. a, 321 ; 

{nlleB-gnuns, ;-l3t4 

B'TDtf, 179 

eonpmta, 179 

rniimlata, 181 






179 



tyiaro'AeK, 213 
liomortyled spcciea, tsl 

iuKamata, 322 

— - Hairuai. 173-17S, 212 

• rni^H. 178, 213 

— ~ (SiOjihytum) tantdina. 



181, 



r<^D« 



322 : sti^'ma, 21 

— rpKima, l(i9, 175, 218 

— *tnV*i, 181, 182 
etjoi'do, 182 
iDiana, 173-172. 211.212 

OiHp, tlio BurdKell, 32, 72 

, Ihe pommon, 55 ; ilifforanocs 

in alructuTouHi function betwi!pa 
tbe twoptmnt-tipeeiM. 56 : offdcu 
oferoeiiiu^, 60; n hflirid betwoin 
Uio ojwsbp nnd priuiniHe. 7U 
Oiylnfhui. 313 ^ 



PiEony, pollon-i^ins if, 333 'I 

PftTHlleliaiutielweonill.'eiliinalniiid 

hylirid rartillBstiOD, 123:1 
Pnmmi'o, 313 
rUoxHrnUii, 120 

ntralit, 120 

«uiaii/o. 119, 287 

Pianclion on LinvmtalmJoiart. 100; 



A 



^H I^DEX. ^^M 


^^B TOLLEM-CItAIKa. 


EBTHU. ^^^1 


^H Pallen-gniiuE. nlulivo ilUraetcr of. 


tilitvoftlietwofonn&S?; lengUi ^^| 


^H 249 


of pistil, 2G6 ^^M 


^M Potyanlhui, 18 


I'rimnla mlgarii,vaT. rubra. 224-228 ^^^1 
Prandia vulguri>. 299 ^^M 






riyeholria. 136 ^H 




FvlnoHaria amjiurfi/oZio, 101, 239; ^^H 


^H J^ms, 2S1 


niilhers, 252, 287 ^^H 




aiHr«a, 110 ^^M 


BizeofaDtheiB, 2.!>2 


■ — - ogieimHi. 101, 238 ; number nl ^^H 


amiata, 187 


floweia, 2481 pistil, 250 ^^H 


J'lHiogueria franmitt, 131 
^_ Primrose, (he oomm.in. 31, 57-^7 1 








^H 


^H 14; BummHry on, 15-19 ; liomo- 




^^1 r.trlcd gpouUi, 49 




^H • auriatla, 30, 43, 4g, 74, 223 


Eflj-llorels, their use, 5. 6 ^H 


^H ciqnal-Btjried vtuietica, 273 


Bhamuui ealhiiHieui, 294, 307: siM ^^H 


^H ._ oirfUA'iiiM, 44 


of corolla, 308 ^^M 


^H (inta. 49 


/m<.gala, 297 ^H 


^H elatioT, Jaoq^ 32 j relativs fflr- 




^H tility of the two forms, 33, 47; 




^H i>otahjbri({.72, 73; tiqual-BtylBU 


Jtubiaeea, 12.% 131-1X0; dw o< ^^M 


^B w. < 224, 273 


anthere, 252; stignuu. 2.'f» ; ^H 


^H farim^ 45 ; equal-stjled vm. 


number of heteroslyled gGutra ^^H 


^M ^4, 273 


284, 285 ^^1 


^B Mnila, 74 


n,^d,j€a fTiaMa. l.U ^H 


^H - 'ii.KDlucTafa,45 


Kiie, the conmoii, !1 ^^^1 




Kw,Uia luberoKi, 329 ^H 


^H moi/u, 4il. 50 




^m scdicx. 49, 50 




^H S.t.Hca, 19 


^^H 




s,.:o.-<.. 308 ^H 


^H S(ne™<>, 22, 30, MS ; rolfllWe 


(t/eubifriinKi, 840 ^^H 


^H 'lertilJly, 39-43, 47, 49; In.ii;- 




^r Btyled,2l3; ibort-Blykil. 215; 


Satureia liorlmtU, 303, 301 ^^H 




Beabliaa arvsnaie. 305 ^^H 


atul ferCltity, 2tG; euiml-.tv-lod 


Qtro-pur/iursu. 305, 3U7 ^^| 


variety. 218-223, 273, 274 


ntooi'Mt, 305 ^^1 


Uri^la. 50 


Scott, J , on PWinub a>(r>nJ.^ SO, ^H 


verii, 14; ilifforenoe id atruo- 


43, 223; f. n.,i!^r£(. 34; (rar. ^H 


^H lure between Die two forms, 15 ; 


n.6rn), 224 i P. SikMmtwii*. 44 ; ^H 


^H degreea of fertility wlieo lof^ti- 






Primu^E, 19,50; hybri.la,74,75: ^^H 


^B 25-.H2: fertility poueiBed byille- 


length of plat^L 272,- BolUy7,in ^^M 


^H gitimRts I>lllu^ 228-234 ; equal- 
^B styled red vuriaty. 231-238; long- 




^H Dtylod, 211 : loDgtli of piaiil, 2(il, 




^H 2tl6 






iug tliruti kin<[s nf dowers, 320 ^^M 


^V o/Uuta, 49 


Senphtdaria aquatiat. 147 ^^M 


^^B ■ B*ton»-(8 (var, aeavlu Linn.), 

^H 31 : polleii-graina, 85 ; ri'lative fer- 


Itermtvla Uneloria. 280. 3U7 ^^H 





352 



INDEX. 



BLTUIA. 

Selhia obtusffoHa, 122 

Bmithf Sir J. E., cm the carrot, 8 ; 
hybrid Ver}>a8cum8, 76, 78; Ser- 
rattUa tinrloria, 280; C^tctM, 
H07; Suhularia, 'Ml 

StUdandla alpina^ 54 

Spe^tUaria per/olintUy 330 

Speiico, Mr., on MoUia^ 168 

Spermacoce, 135 

Sprengel on Hottonia paluatrUy 51 

SteLlaria gramineay 313 

Btrawborry, the Uautbois, 293 

Suhularia^ 311 

Suteria, 131 



T. 



Thelymitra, 313 

Thomson, Dr., on Campanula, 330 
Thrum-eyed, origin of term, 14 
Thwaites, Mr., on ovules of Lim- 

nanthemum Indicum^ 116 ; Sethia 

acuminata, 122 ; Discospermum, 

286 
Thymdia, 114 
Thymns citriodoniSy 301 

serpyllum, 299, 301, 302, 304 

vulrjarUt 302 

Timbal-Lap:rave, M., on hybrids in 

genus Cuius, 76 
Torrey, Dr., on Hottonia inflata, 

63, 313 
Transmission of tlie two forms of 

heterostyled plants. 268-270 
Treviranus on Androsace vital- 

liana, 53; Linum, 81 



V. 



VandeDia nummularifoUa, 324 

— -^ sessiflora^ 325 

Viiucher on the carrot, 8; Solda- 
nella alpina, 54; Lythrum sali- 
carta, 138, 144; L. thymifoUa, 
165; Hex aqui/oUumt 297; on 



WBAT. 

LalAatfe, 299; Viola hirta and 

eollina, 31 7 
Ferbcwcum, wild hybrids of, 75-80 

hjchnitis, 30, 76-78 

phcenieeum, 78 

ihapsm, 76-79 

mV^a^um, 78 

- Vibwmumy 6, 7 
Ftcta, 327 

ViUarsia, 116; anthers, 252 
Fto^i alba, 31.5, 320 

/>uv>/or, 320 

bifltn-a, 320 

canina, 314, 321 

coUina, 317 

«fZa<ior, 320 

hirta, 318, 320 

ionodiumj 320 

lancifolia, 320 

mirclbilis, 320 

nana, 319, 320 ; poUon-CTaini 

of, 338 

odorata, 317, 336 

palustriSf 320 

Rozburghiana, 319 

Ruppii, 320 

sylvatica, 320 

tricolor^ 4, 320 

Voandzeia, 327 



W. 

Walnut, the, 10 

Watson, H. C, on cowslips, prim- 
roses, and oxllps, 57, 60, 63; 
Primula datior^ 72, 73 

Weddell, Dr., on iiybrids between 
Acerax and Orchis, 76 

Wetterhan, Mr., on Corylus, 10 

Wichura, Max, on hybrid willows, 
76 ; sterile hybrids, 240 

Wirtgen on I/y thrum salicaria, 138, 
144, 148 

Wooler, W., on Polyanthus, 1 8 

Wray, Leonard, on Fragaria, 293 



J 



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