The Different Forms of Flowers on Plants of the Same Species

ter of cleisto

cing such flowers, and t

able

cleistogamic flowers in

d with that of th

aceto

ree forms of cle

del

on

ati

os

tions on various othe

ies producing cle

ct flowers rar

remarks on the origin o

h may be drawn from the ob

mber, with the anthers of very small size, containing few pollen-grains, which have remarkably thin transparent coats, and generally emit their tubes whilst still 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. Consequently insects do not visit them; nor if they did, c

e of Ranunculus aquatalis, Alisma natans, Subularia, Illecebrum, Menyanthes, and Euryale, remain closely shut as long as they are submerged, and in this condition fertilise themselves. (8/2. Delpino 'Sull' Opera, la Distribuzione dei Sessi nelle Piante' etc. 1867 page 30. Subularia, however, sometimes has its flowers fully expanded beneath the water, see Sir J.E. Smith 'English Flora' volume 3 1825 page 157. For the behaviour of Menyanthes in Russia see Gillibert in 'Act. Acad. St. Petersb.' 1777 part 2 page 45.-On Euryale 'Gardener's Chronicle' 1877 page 280.) They behave in this manner, apparently as a protection to their pollen, and produce open flowers when exposed to the air; so that these cases seem rather different from those of true cleistogamic flowers, and have not been

Botany' volume 11 1870 page 254, observed plants of Arachis in Brazil, and could never find such flowers. Plantago has been omitted because as far as I can discover it produces hermaphrodite and female flower-heads, but not cleistogamic flowers. Krascheninikowia (vel Stellaria) has been omitted because it seems very doubtful from Maximowicz' description whether th

t that this plant produces true cleistogamic flowers. For Pavonia see Bouche in 'Sitzungsberichte d. Gesellsch. Natur. Freunde' October 20, 1874 page 90. I have added Thelymitra, as from the account given by Mr. Fitzgerald in his magnificent work on 'Australian Orchids' it appears that the flowers of this plant in its native home never open, but they do not appear to be reduced in size. Nor is this the case with the flowers of certain specie

TYLE

AGI

rich

LVULA

sc

HULAR

phul

na

del

THAC

iacan

nth

lacan

racan

mant

el

IAT

mi

lv

AGIN

bap

tag

EPIA

pel

ANUL

cul

pan

ULAC

ton

POS

ndr

CIF

roca

LAC

ol

TIN

anth

ch

VEA

vo

IGHI

icha

ica

ma

nu

YGA

yga

AMIN

ati

NIAC

al

MINO

on

chae

pma

osan

ped

ci

hyr

a vel Ne

icar

yc

act

ndz

ERAC

os

OTYLE

NC

nc

MIN

er

rd

tost

ELIN

mel

EDER

och

HID

mbur

tle

den

lym

her, and next in order in that of the Acanthaceae and Malpighiaceae. A large number, but not all the species, of certain genera, as of Oxalis and Viola, bear cleistogamic as well as ordinary flowers. A sec

ce of an admirable paper by Hugo Von Mohl, whose examination was in some respects much more complete than mine. (8/4.

a ca

The connective expands into a membranous hood-like shield which projects above the anther-cells. These two lower stamens have no vestige of the curious appendages which secrete nectar in the perfect flowers. The three other stamens are destitute of anthers and have broader filaments, with their terminal membranous expansions flatter or not so hood-like as 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 8-10/7000 of an inch in diameter, and therefore of smaller size than the ordinary pollen-grains similarly treated, which have a diameter of 13-14/7000 of an 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 por

leistogamic 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 average number of seeds as some capsules from flowers outside the net which had been fertilised by bees. I have repeatedly seen Bombus hortorum, lapidarius, and a t

by the perfect flowers contained on an average 9.85 seeds; and 17 capsules from the cleistogamic ones contained 9.64 seeds,-an amount of difference of no significance. It is remarkable how much more quickly the capsules from the cleistogamic flowers are developed than those from the perfect ones; for

E-FLOWERED, SINGLE,

lastic 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 scatter the seeds of the sub-aerial ones, as in the other species of Viola. It is remarkable that this plant, according to Delpino, does not produce cleistogamic flowers in one part of Liguria, whilst the perfect flowers are there abundantly fertile (8/7. 'Sull' Opera, la Distribuzione dei Sessi nelle Piante' etc. 1867 page 30.); on the other hand, cleistogamic flowers are produced by it near Turin. Another fact is worth giving as an instance of correlated development: I found on

a hi

ced 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 withered away and aborted. He states that the peduncles of the cleistogamic flowers curve downwards and bury the ovaries beneath the soil. (8/8. These statements are taken from Professor Oliver's exc

la

flowers when growing 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 stamens, 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 delicate

Roxbur

species; but no perfect ones were produced. Mr. Scott informs me that in India it bears perfect flowers only during the cold season, and

, according to D. Muller, Michalet, Von Mohl, and Hermann Muller, with V. elatior, lancifolia, syl

are produced; and so it is with V. biflora. The same author states that he has seen in the case of V. alba flowers intermediate in structure between the perfect and c

grains probably fall out of the cells on the stigma, instead of protruding their tubes whilst still enclosed, as in the other species. In V. hirta all five stamens are likewise antheriferous; the petals are not so much reduced and the pistil not so much modified as in the following species. In V. nana and elati

aceto

essively fine points, were seen by me stretching upwards from the lower anthers towards the stigmas, which they had not as yet reached. My plants grew in pots, and long after the perfect flowers had withered they produced not only cleistogamic but a few minute open flowers, which were in an intermediate 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,

lla produce cleistogamic flowers (8/10. 'Monatsbericht der Akad. der Wiss. zu Berlin' 1866 page 369.); and I

iophytum)

extremely minute, barely visible scales, which adhere firmly to the rounded bases of the shorter stamens. Their stigmas are much less papillose, and smaller in about the ratio of 13 to 20 divisions of the micrometer, as measured transversely from apex to apex, than the stigmas of the perfect flowers. The styles are furrowed longitudinally, and are clothed with simple as well as glandular hairs, but only in the cleistogamic flowers produced by the long- styled and mid-styled forms. The anthers of the longer stamens are a little smaller than the corresponding 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, pr

a nummul

iverge much at their lower ends and are only 5/700 of an inch (.181 millimetres) in their longer diameter. They contain but few pollen-grains, and these emit their tubes whilst still within the anther. The pistil is 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 generally 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 the

lowers apparently include four anthers instead of two as above described. The plants, moreover, of V. sessiflora produce subterrane

ia sp

(8/12. 'Bulletin Soc. Bot. de France' tome 7 1860 page 468.) They there produce flowers not offering any peculiarity in structure, excepting that their cor

s col

ording to Von Mohl, with the cleistogamic flowers of other Leguminosae. Five of the stamens are destitute of anthers, and alternate with the five thus provided. The two cells of the anthers are minute, rounded and separated from one another by connective tissue; they contain but few pollen-grains, and these have

minut

ey 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 4.1 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 Mr. Bentham O. parviflo

us nis

and 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 as the true cleistogamic

ted into a tube and their pistils are hook-shaped. In three of the genera, namely Vicia, Amphicarpaea, and Voandzeia, the cleistogamic flowers are produced on subterranean stems. The perfect flowers of Voandzeia, which is a cultivated plant, are said never to produce fruit

iens

t 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 descriptions. Mr. Bennett found on the banks of the Wey that the plants which bore cleistogamic flowers alone were t

s noli-m

, but not, so far as I could see, those of the cleistogamic flowers; and a provision of this kind would here have been useless, as the grains can never be transported by insects. The flowers of I. balsamina are visited by humble-bees (8/15. H. Muller 'Die Befruchtung' etc. page 170.), and I am almost sure that this is the case with the perfect flowers of I. noli-me-tangere. From the perfect flowers of this latter species covered with a net eleven spontaneously self-fertilised cap

rotund

e 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

the cleistogamic ones appear only during the hot season. According to Torrey and Gray, the North American species of Helianthemum, when growing in poor soil, produce only cleistogamic flowers. The cleistogamic flowers of Specularia perfoliata are highly remarkable, as they are closed by a tympanum formed by the rudimentary corolla, and without any trace of an opening. The stamens vary from 3 to 5 in number, as do the sepals. (8/17. Von Mohl 'Botanische Zeitung' 1863 pages 314 and 323. Dr. Bromfield 'Phytologist' volume 3 page 530, also remarks that the calyx of the cleistogamic flowers is usually only 3-cleft, while that of the perfect flower is mostly 5- cleft.) The collecting hairs on the pistil, which play so important

short sack formed of the membranous spathe, without any opening or fissure." There is only a single fertile stamen; the style is almost obsolete, with the three stig

du Museum' tome 3 1843 pages 35-38, 82-86, 589, 598.) The style is absent or rudimentary; 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, accord

s. 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 stamens 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 tra

fonius an

enus Hordeum it has been shown by Delpino that the majority of the flowers are cleistogamic, some of the others expanding and apparently allowing of cross-fertilisation. (8/23. 'Bollettini del Comizio agrario Parmense.' Marzo e Aprile 1871. An abstract of this valuable paper is given in 'Botanische Zeitung' 1871 page 537. See also Hildebrand on Hordeum in 'Monatsbericht d. K. Akad Berlin' October 1872 page 760.) I hear fr

a oryz

when these were pressed the fluid moved about, giving a similarly 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 1/50 of an inch in length or about one-third of the length of those in the perfect flowers. One of the three anthers dehisces before the two others. Can this have any relation with the fact that in some other species of Leersia only two stamens are fully developed? (8/25. Asa Gray 'Manual of Botany of the United States' 1856 page 540.) The anthers shed their pollen on the st

in a large tub of water in my greenhouse behaved on one occasion in a very different manner. They protruded two very large much-branched panicles; but the florets never opened, though these included fully developed stigmas, and stamens supported on long filaments with large anthers that dehisced properly. If these florets had opened for a short time unperceived by me and had then closed again, the empty anthers would have been left dangling outside. Nevertheless

nnsylvania resembled the European ones in their concealed manner of fructification. There can therefore be little doubt that this plant generally propagates itself throughout an immense area by cleistogamic seeds, and that it can hardly ever be invigorated by cro

ARKS ON CLEIST

currence, in some instances, on the same plant of a series of gradations between the cleistogamic and perfect flowers. But that the former owe their origin wholly to arrested development is by no means the case; for various parts have been specially modified, so as to aid in the self-fertilisation of the flowers, and as a protection to the pollen; for instance, the hook-shaped pistil in Viola and in some other genera, by which the sti

ared, leaving a simple open passage into the ovarium. It is also interesting to note the complete loss of trifling points 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 Malpighia

ly through the air towards the stigma. I have observed the emission of the tubes from the pollen-masses whilst still within the anthers, in three widely distinct Orchidean genera namely Aceras, Malaxis, and Neottia: see 'The Various Contrivances by which Orchids are Fertilised' 2nd edition page 258.) It is, however, a wonderful sight to behold the tubes directing themselves 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

rge supply of seeds with little consumption of nutrient matter or expenditure of vital 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 none 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-cell of Oxalis acetosella contained from one to two dozen pollen-grains; we will say 20, and if so the whole flower can have produced at most 400 grain

which it may be presumed serves to protect them from being devoured by birds or other enemies. But this advantage is accompanied by the loss of the power of wide dissemination. 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, Linaria, Commelina, and at least three genera of Legu

f seed, has been in part determined by the perfect flowers 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 wind; and there seems no reason why their perfect flowers should fail to be fertilised more frequently than those in any other anemophilous genus. In contrast with what we here see with respect to the large proportion of the perfect flowers being irregular, one genus alone out of the 38 heterostyled genera described in the previous cha

cases as that of Salvia cleistogama not having produced perfect flowers during five years in Germany (8/31. Dr. Ascherson 'Botanische Zeitung' 1871 page 555.), and of an Aspicarpa not having done 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 that as a general rule the perfect flowers produced by cleistogamic plants are sterile; but it has been shown under the head of the several species that this is not the case. The perfect fl

fer from a wide-spread analogy. But of such invigoration I have only a small amount of direct evidence: two crossed seedlings of Ononis minutissima were put into competition with two seedlings raised from cleistogamic flowers; they were at first all of equal height; the crossed were then slightly beaten; but on

favourable conditions, but still retain their fertility unimpaired. Linnaeus 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. Asa Gray has seen flowers on exotic plants in the Northern United States which never expanded and yet fruited. With certain English plants, which bear flowers during nearly the whole year, Mr. Bennett found that those produced during the winter season were fertilised in the bud; whilst with other species 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 Lysimachia vulgaris if fully exposed to the sun expand properly, 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

land of Russia. 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 development 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 are 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 corol

n been already transported habitually by insects or by the wind from flower to flower, we may assume that the process of separation did not commence and was not completed for the sake of the advantages to be gained from cross-fertilisation. The sole motive for the separation of the sexes which occurs to me, is that the production of a great number of seeds might become superfluous to a plant under changed conditions of life; and it might then be highly beneficial to it that the same flower or the same individual should not have its vital powers taxed, under the struggle for l

o the same form are united the union is an illegitimate one and more or less sterile. 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 h

DE

thac

campe

ox

ata. -mollis

, Dr.,

ma n

icar

ia spec

length of sta

sa ar

ce vita

in different for

ac

hispid

r., on Salvi

s buf

a oryz

lep

the c

la sco

Primula

ofessor, on P

ria gr

n of the tubes f

M., on r

s fulva. flowers fertilise

tiation of the sexes. on the

agi

cowslip an

rer

ffect of temperature

dia le

n Draco

W., on Prim

., on primros

la el

ria per

rt, on sexu

at, the

a pal

ula co

mine

ssor, on Rhamn

tle

mis

na mic

rs. list of genera

aulis. -

lum. polle

ros

. pist

in size in the sexes

yda

us av

ommon. short-

ylon f

., on Planta

tost

a pur

ed plants. prepotency of pollen. insects fertilising flowers. Cephala

n Pulmonaria

a arb

lnut. Polygonaceae. pollen-grains. Thymus serpyll

us bar

on Eriophorum

us frax

od

nd sub-dioe

ospe

H., on Prim

halum Mo

glica. - r

, M., on Cr

a oryz

ton, on Salv

ylon f

m vul

den

ea re

emum a

um angus

um. pollen

us Eur

ia offi

ry

pollen-

, Mr., on

ensa. stamens.

s. - elatior. - ve

us exc

m cru

mula vulgaris and veris. hybrid Verbascums. prepotency of pollen

tia

niac

um syl

ia pen

opifolia. - micrantha. -

t on Men

sa Lil

n hybrid

roposes the term heter

Lin

rnettiana an

hia su

pulc

ronop

subu

ella

styled

ros

nym

s lanc

ea re

x o

ago m

s and Ny

iens

er

gamic f

oecious

on Nepeta

Strawbe

yot

d Professor, on

on flowers self-fertil

., on hybri

mately fertilised plants. diameter of pollen-grains. size of anthers, structure of stigma. list of genera. advantages derived from Heterostylism.

, pollen

or, introduces the

lorets of th

la Si

grandi

per

ria off

azu

num fa

al

plants becom

rd

species o

r., on C

rd

is. relative fertility. ant

nia co

car

d Pri

ran

rici

s offic

ifolium

edlings. Primula Sinensis, in some degree dwarfed. equal-styled varieties. Primula vulgaris. transmission of form and colour. seedl

ece

s of. - balsamina. - fu

ans

s buf

de, on Mal

Primula. on use of hairs within the corolla. size of coroll

on Monochor

ox

rimula lo

henin

s producing differently formed seeds. heterostyle

ndica. - parvif

us nis

on the co

s and p

la el

Aust

hyssop

am

oecious

osa s

a od

oides. polle

., Ponteder

two, compared with that of the two illegitimate i

d W.A., on the co

cum vi

n, polle

osip

inata. - Burne

the Gl

dicum. pollen-g

ia sp

n Fragari

ula veris, vulga

um. various experiments. pistils and stamens. sterile with its own-form pollen. - Lewisii. - per

ost

chia v

m Grae

sopif

lica

rtilisation betwee

y of r

ffspring from

ing rem

tyled

ed

ymif

ighi

tia b

the c

., on Primu

go lan

xwell, on cleis

on Krasch

Mr., on

ea re

nopodium -

rrea de,

ndz

ca. - hirsuta

es. - tr

n Oxalis a

ia sp

lla. -

of the same species. Trifolium and Arachis. cleistogamic flowers.

pidota. -

, M., o

ria vag

erry

., on Vio

on pollen of

ra

eria f

sa

al

ted

s Reg

mis

tior. - villosa. Hottonia palustris. table of relative fertility of. Linum catharticum. Polygonum fagopyrum. Lythrum salicaria. on the origin of heterostylism.

sot

a gle

rt

verti

riability in length

tag

nlan

ace

or, on ovules o

ol

ula co

. - minutissima

num v

corniculata. - Deppei. - hedysaroides. - homostyled species. - incarnata. - Regnelli. - ro

the Bar

he c

e and function between

s of c

en the cowslip

bap

pollen-g

illegitimate and h

vo

i. - nivalis

salsoloides. L. Le

lanceolat

moni

s, relative

yan

gona

rta. - fagopyru

-grains. size of a

eria f

e, the

. - longiflora. - mollis. - Scotica. - Sibirica. - Sikkimensis. - Sinensis. relative fertility. long-styled. short-styled. transmission of form, constitution and fertility. equal-styled variety. - stricta. - veris. difference in structure between the two forms. degrees of fert

ulgaris,

la vul

cho

hers. - azurea. - officinali

lus aqu

rets, t

size of corolla. - fr

us crist

hers. stigmas. number

a eri

the c

ia tu

leistogama.

ia hor

is. - atro-purp

n Primula farinosa. homostyled Primulae. hybrids. length of pistil. Hottonia palustris. Androsace vit

laria a

ula ti

minata. -

J.E., on

Verba

ula ti

ic

ula

ella a

ria per

Mr., o

rma

n Hottonia

ria gr

ry, the

ula

te

lym

Dr., on C

d, origin

n ovules of Limn

a acu

ospe

mel

orus. - serpyl

M., on hybrids

, on Hotton

he two forms of h

on Androsac

nu

mularifolia.

ythrum salicaria. - thymifolia. Ilex aquifo

f. - lychnitis. - phoenic

urn

ci

sia. a

ta. - ionodium. - lancifolia. - mirabilis. - nana. pollen-grains of. -

ndz

ut,

cowslips, primr

la el

hybrids between A

, Mr., on

hybrid willows.

n Lythrum

W., on P

nard, on