The Different Forms of Flowers on Plants of the Same Species

g from all three form

nd sterility, some utte

form to the legitimate a

mate offspring in some deg

of P. Sinensis, auricul

red variety, Illegitim

ants raised during severa

d stature an

d varieties

form by Pulmonar

ding r

een illegitimate ferti

f fertility, and in their powers of growth or vigour. I will begin with trimorphic plants, and I must remind the reader that each of the three forms can be fertilised in six different ways; so that all three together can be fertilised in eighteen different ways. For instance, a long-styled form can be fertilised legitimately by the longest stamens of the mid-styled and short-styled forms, and illegitimately by its own- form and mid

and will not probably soon be repeated- thus, I was compelled to count under the microscope above 20,000 seeds

m sali

ased their fertility. Lythrum salicaria is much affected in its fertility by the nature of the season; and to avoid error from this source, as far as possible, my observations were continued during several years. Some few experiments were tried in 1863. The summer of 1864 was too hot and dry, and, though the plants were copiously watered, 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 t

d 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 (Number 10), which was legitimately and naturally fertilise

BY LEGITIMATE PLANTS OF THE THREE

style

of seeds in e

rved out of twenty-

tyled

umber of

erved out of thirt

styled

83.5; but we may, for the

rved out of twenty-

YLED PARENTS FERTILISED WITH POLLEN FROM THE MID-LENGTH

id-length or shortest stamens of the same form; but I have good reason to believe that they were the product of the latter. These eight plants were much more dwarfed, and much more sterile than those in the other two lots. The latter were raised from a long-styled

ld 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 fact, namely, that the long-styled form, fertilised illegitimately by its own-form

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 tough, or pulpy matter, without any good pollen-grains, and they never shed their contents; they were in the state designated by Gartner as contabescent, which term I will for the future use. (5/2. 'Beitrage zur Kenntniss der Befruchtung' 1844 page 116.) In one flower all the anthers were contabescent excepting two which appeared to t

ANT

lace close to a brother long-styled plant Number 2, so that it must have been freely though illegitimately fertilised; under these circumstances it did not yield during 1864 and 1865 a single capsule. I should here state tha

AN

y growing in company with Number 1, by which it will have been illegitimately fertilised, it yielded in 1866 not a single capsule, but in 1865 it yielded twenty-two capsules: the best of these, fifteen in n

S 3 A

ly fertilised during 1863 by the same illegitimate mid-styled p

AN

64, 1865, and 1866, it was surrounded either by illegitimate or legitimate plants of the other two forms; but it did not yield a single capsule. It was a superfluous experi

AN

urable year of 1866, surrounded by illegitimate plants

AN

of which yielded an average of 36.1 seeds, with a maximum of 47 and a minimum of 22; so that this plant produced 39 per cent of the full number of seeds. During 1864 it was surrounded by legitimate and illegitimate plants of the other two forms; and nine capsules (one poor one b

llen from its own mid-length stamens, the plants, as already stated, were not nearly so dwarfed or so sterile as in the fi

ANT

the other two forms, and ten capsules yielded on an average 41.1 seeds, with a maximum of 73 a

AN

wo forms, most of which were moderately fertile. Fifteen capsules yielded on an average 57.1 seeds, with

NT

as the last. Ten capsules yielded an average of 44.2 seeds, with a maximum of 69 and

lant, growing by itself and visited by insects, yielded an average of 21.5 seeds per capsule, with a maximum of 35; but, to judge fairly of its fertility, it ought to have been observed during successive seasons. We may also infer from analogy that, if several legitimate long-styled pla

ANT

as one of the most fertile of the whole lot of nineteen plants. But the average

NT

les; and ten yielded an average of only 15.4 s

NT

, with a maximum of 95 and a minimum of 29. Considering that this plant was illegitimate and illegitimately fertilised by its brother long-styled seedlings, the average and

M A SHORT-STYLED PARENT FERTILISED WITH

is form to reproduce, when self-fertilised, the parent-form; but the tendency is not so strong as with the long-styled. These nine plants nev

ANT

hort-styled plants. Fifteen capsules yielded an average of 28.3 seeds, with a maximum of 51 and a minimum of 11; hence this plant produced only 33 per cent of t

NT

a minimum of 7. But two poor capsules may be rejected, and then the average rises to 32.6, with the same maximum of 49 and a minimum of 20; so that th

NT

psules an average of 77.8 seeds, with a maximum of 97 and a minimum of

NT

imum of 88 and a minimum of 57. Hence this plant produced 82 per cent of the proper number of seeds. Twelve flowers enclosed in a net were artificially and legitimately fertilised with pollen from a legitimate short-styled pla

OM A MID-STYLED PARENT FERTILISED WITH

ng-styled; but from so small a number we can hardly judge of the tendency in mid-styled plants when self-fertilised to reproduce the s

ANT

and a minimum of 63: hence this plant did not produce quite 80 per cent of the normal number of seeds. Twelve flowers were artificially and legitimately fertilised with pollen from a legitimate long-styled plant, and yielded from nine capsule

NT

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 capsu

NT

ertilised in the same manner, yielded an average from ten capsules of 69.6 seeds, with a maximu

RT-STYLED PARENT FERTILISED WITH POLLEN FROM T

were raised; these consisted of eight short- styled, and four long-styled plants, with not one mid-styled. These twelve plants never attained quite their full and proper height, but by no means deserved to be called 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 contabescent, was e

ANT

and short-styled parents, yielded an average from ten capsules of 43 seeds, with a maximum of 63 and a minimum of 26: hence this plant, w

NT

ds, with a maximum of 123 and a minimum of 86; so that it produced 121 per cent of seeds in comparison with the normal standard. During 1864 it was allowed to be freely and legitimately fertilised 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 90; consequently

NT

illegitimate plants specified under the last experiment, and eight capsules yielded an average of 113.5 seeds, with a maxi

NT

but yielded an average, from ten capsules, of only 55 seeds, with a maximum of 88 and a minimum of 24, thus attaining 59 per cent of the normal fertility. This low degree of fertility, I presume, was owing to the unfavourable season; for during 1866,

NT

ary number of seeds. During 1866 it was freely and legitimately fertilised by illegitimate plants, as described under Number 22, and yielded an average, from eigh

-STYLED PARENTS FERTILISED WITH POLLEN FROM

lants: in one mid-styled plant, some of the anthers of the longest stamens were contabescent, 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

ANT

0 and a minimum of 64, thus attaining 64 per cent of the normal fertility. During the highly favourable year 1866, it was freely and legitimately fertilised by illegitimate plants belonging to the present Class and to Class 5, and yielded an

NT

, with a maximum of 122 and a minimum of 53, thus attaining to 76 per cent of the normal fertility. If the season had been more fa

NT

26, yielded an average, from eight capsules, of 89 seeds, with a maximum of 119 and a minimum of 69, thus producing 68 per ce

NT

g to 91 per cent of the normal fertility. During the highly favourable season of 1866, when fertilised in the manner described under Number 26, it yielded an average, from nine capsules (one poor capsule having been excluded), of 100 seeds, with

nt

Number 26, and yielded an average, from eight capsules, of 94 seeds, with a maximum of 106

nt

led plants; and five capsules yielded an average of 90.6 seeds, with a maximum of 97 and a minimum of 79. Hence, as far as can

-STYLED PARENTS FERTILISED WITH POLLEN FROM

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. Nor did I observe any contabescent anthers. It deserves, also, particular not

ANT

erous surrounding legitimate and illegitimate plants. Eight capsules yielded an average of 127.2 seeds, w

NT

and ten capsules yielded an average of 113.9, with a maximum of 137 and a minimum of 90. Hence

EGITIMATE OFFSPRING OF THE TH

rent-form. When the short-styled form was illegitimately fertilised by the long-styled form (Class 5), and again when the mid-styled was illegitimately fertilised by the long-styled (Class 6), in each case the two parent-forms alone were reproduced. As thirty-seven plants were raised from these two unions, we may, with much confidence, believe that it is the rule that plants thus derived usually consist of both parent-forms, but not of the third form. When, however, the mid-styled form was illegitimately fertilised by the longest stamens of the short-styled (Class 7), the same rule did not hold good; for the seedlings consisted of all three forms. The illegitimate 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 f

when legitimately fertilised, generally by illegitimate plants, as described under eac

F THE THREE FORMS, WHEN LEGITI

n 1:

ge number of se

mum number in

mum number in

No record was kept as a

ect

No record was kept as a

ect

: No record was kept as

ect

.30. Co

FROM LONG-STYLED PARENTS FERTILISED WITH POLLE

umber (name

n 2:

ge number of se

number of seeds

number of seeds

of seeds, expressed as th

nda

tyled : 0

yled : 4.5

yled : 4.5

yled : 4.5

d : 0 or 1 : 2

tyled : 0

led : 36.1 :

led : 41.1 :

led : 57.1 :

led : 44.2 :

OM SHORT-STYLED PARENTS FERTILISED WIT

yled : 32.6 : 49 : 20 : 38. 16 : Short-styled : 77.8 :

ROM MID-STYLED PARENTS FERTILISED WIT

. 19 : Mid-styled : 73.4 : 87 : 64 : 56

T-STYLED PARENTS FERTILISED WITH POLLEN FROM

23 : 86 : 121. 23 : Short-styled : 113.5 : 123 : 93 : 136. 24 : Long-s

-STYLED PARENTS FERTILISED WITH POLLEN FROM

8 : Mid-styled : 89.0 : 119 : 69 : 68. 29 : Long-styled : 100.0 : 121 : 77 : 107.

-STYLED PARENTS FERTILISED WITH POLLEN FROM

4 : 96 : 98. 33 : Short-styl

of Cross and Self- fertilisation in the Vegetable Kingdom' 1876.) None of the nineteen illegitimate plants in the first four classes were completely fertile; one, however, was nearly so, yielding 96 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 bearing 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 legitimate plants. There is good reason to believe that the first seven plants in Class 1 and 2 were the offspring of a long-styled plant fertilised with pollen from its own-form shortest stamens, and these plants were the most sterile of all. The remaining plants in Class 1 and 2 were almost certainly the product of pollen from the mid-length stamens, and although very sterile, they were less so than the first set. None of the plants in the first four classes attained their full and pro

ely of variability. But this view must be rejected, as far as the less fertile plants in these three classes are concerned: first, because none of the plants in Class 5 attained their proper height, which shows that they were in some manner affected; and, secondly, because many of the plants in Classes 5 and 6 produce

d, in the case of the illegitimate plants, that in order to avoid over-estimating their infertility, ten very fine capsules were always selected; and the years 1865 and 1866, during which the plants in the three latter classes were experimented on, were highly favourable for seed-production. Now, if this plan of selecting very fine capsules during favourable seasons had been followed for obtaining the normal standards, instead of taking, during various seasons, the first capsules which came to hand, the standards would undoubtedly have been considerably higher; and thus the fact of the six foregoing plants appearing to yield an unnaturally high percentage of seeds may, perhaps, be explained. On this view, these plants are, in fact, merely fully fertile, and not fertile to an abnormal degree. Nevertheless, as characters of all kinds are liable to

very sterile. Long-styled parent-plants when fertilised with pollen from their own-form shortest stamens, appear 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 relationship, short-styled plants illegitimately fertilised with pollen from the mid-length stamens of the long- styled form (Class 5) are very sterile; whereas some of the offspring raised from this union were far from being highly sterile.

AL

s of Oxalis Valdiviana, but they did not germinate (5/4. 'Botanische Zeitung' 1871 page 433 footnote.); and this fact, as he remarks, supports my view

parents, and only 38 belonged to the third form distinct from either parent. In the case of O. Regnelli, the result, as observed by Hildebrand, was nearly the same, but more striking: all the offspring from four of the legitimate 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 belonged to the same two forms as their parents, and only 8 to the third form. Fritz Muller also raised in Brazil seedlings from long-styled plants of O. Regnelli legitimately fertilised with pollen from the longest stamens of the mid-styled form, and all these belonged to the two parent-forms. (5/5. 'J

ar by seed, and have always produced long-styled plants. (5/6. 'Ueber den Trimorphismus in der Gattung Oxalis: Monatsberichte der Akad. der Wissen. zu Berlin' 21 June 1866 page 373 and 'Botanische Zeitung' 1871 page 435.) Again, 17 seedlings were raised from mid- styled plants of

IM

la Si

ds, with a maximum in one capsule of 66 seeds. Four other flowers legitimately crossed with pollen from a legitimate 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 I have found some difficulty in estimating the nor

ut 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 flowers were strikingly different from those of their progenitors; and this I think, can only be accounted for on the principle of reversion. Most of the anthers on one plant were contabescent. Seventeen flowers on the grandchildren were illegitim

ong-styled seedling were illegitimately fertilised with their own-form pollen and produced only three capsules, containing 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 shor

ve more than a single plant die out of a large lot. The two grandchildren which lived and flowered were short-styled; and twelve of their flowers were fertilised with their own-form pollen and produced twelve capsules containing an average of 28.2 seeds; so that these two plants, though belonging to so weakly a set, were rather more fer

o my surprise all proved short-styled. Twelve short-styled flowers borne by these grandchildren 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 maximum of 35. These figures are rather below the normal standard for su

SION OF FORM, CONSTITUT

FFSPRING OF Pr

respect to the short-styled plants, twenty-four out of twenty- five of their illegitimate offspring were short-styled. They were dwarfed in stature, and one lot of grandchildren had so poor a constitution that four out of six plants perished before flowering. The two survivors, when illegitimately fertilised with their own-form pollen, were rather less fertile than they ought to have been; 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

VARIETY OF Pri

were nearly as globular and as smooth as in the short-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-styled form. But the structure varied much even on the same umbel: 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

. Preponderance of long-styl

ame of owne

Long-sty

Short-st

equal-styl

ood : 0

k : 20

: 30 :

er : 12

: 42 :

ms : 16

am : 1

om purchased see

134 :

ers generally collecting seed from self-fertilised flowers; and the long-styled flowers produce spontaneously much more seed (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-fertilised, very generally reproduce long-st

rivelled, whilst many were fully as large as those of the short-styled form and rather more globular. It is probable that the large size of these grains was due, not to their having assumed the character of the short-styled form, but to monstrosity; for Max Wichura has observed pollen-grains of monstrous size in certain hybrids. The vast number of the small shrivelled grains in the above two cases explains the fact that, though equal-styled plants are generally fertile in a high degree, yet some of them yield few seeds. I may add that my son compared, in 1875, the grains from two white-flowered 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 grains were in diameter to those in the other plant, in which the stigma projected less, as 100 to 88; whereas the difference between the grains from perfectly characterised long-styled and short-styled plants is as 100 to 57. S

equal-styled; so that this abnormal condition was faithfully transmitted, probably through three, and certainly through two generations. The fertility of one of these grandchildren was carefully observed: six flowers were fertilised with pollen from the same flower, and produced six capsules, containing on an average 68 seeds, with a maximum of 82, and a minimum of 40. Thirteen capsules spontaneously self-fertilised yielded an average of 53.2 seeds, with the astonish

igmas, though properly elongated, were smooth; so that we have here a slight approach in structure to the pistil of the short-styled form. Some of these long-styled plants also approached the equal-styled in function; for one of them produced no less than fifteen spontaneously self-fertilised capsules, and of these eight contained, on an average, 31.7 seeds, with a maximum of 61. This average would be rather low for a long-styled plant artificially fertilised with its own pollen, but is high for one spontaneously self-fertilised. For instan

gardener is positive was not long-styled; hence, probably, it was equal-styled. In all these fifteen plants the anthers, occupying the same position as in the long-styled form, closely surrounded the stigma, which in one instance alone was slightly elongated.

CT TO THE EQUAL-STYLED

self- fertilised parent. The position of the stamens in their proper place low down in the tube of the corolla, together with the small size of the pollen-grains, show, firstly, that the equal-styled variety is a modification of the long- styled form, and, secondly, that the pistil is the part which has varied most, as indeed was obvious in many of the plants. This variation

la aur

to the long-styled form. Hence these plants have become equal-styled by the increased length of the stamens, instead of, as with P. Sinensis, by the diminished length of the pistil. Mr. J. Scott observed five other plants in the same state, and he shows that one of them, when self- fertilised, yielded more seed than an ordinary long- or short-styled form would have done when similarly fertilised, but that it was far inferior in fertility to either form when legitimately crossed. (

one-fourth of the seedlings appear long-styled; so that the short-styled form of the Auricula, when fertilised by its own pollen, does not reproduce the same form in so large a proportion as in the case of P. Sinensis. We may further infer that the short

la fa

of the pollen-grains, these plants owe their structure, as in the case of P. auricula, to the abnormal elongation of the stamens of the long-styled form. In accordance with this view, they yield less se

la el

h an occurrence known to me, with the exception of some wild plants of the Oxlip-a hybrid between P. veris and vulgaris-which were equal-styled. Herr Breitenbach's case is remarkable in another way; for equal-st

ulgaris,

LINN. AND P. a

. R

the plants, when artificially fertilised with their own pollen, yielded a moderate supply of seed. (5/10. 'Journal of the Proceedings of the Linnean Society' 8 1864 page 98.) He was so kind as to send me some of these self- f

er, 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 be 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. The yellow-flowered and the purple-flowered plants of this first generation were fertilised under a net

ays with their own pollen and with that of the common primrose; and the seeds were separately counted, but as I could

2. Primul

plant experimented o

ber of flower

mber of caps

ge Number of se

Number of seeds

Number of seeds

yled plants, ILLEGITIMATELY fertilised with poll

lants, ILLEGITIMATELY fertilised with pollen from the

luding less than 15 seeds, be reject

plants, LEGITIMATELY fertilised with pollen from the

luding less than 15 seeds, be reject

fertilised with pollen from the long-styled illegitimate

apsules be rejected, we ge

fertilised with pollen from the long-styled illegitimate p

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 producing any capsules when the access of all insects (except such minute ones as Thrips) was prevented; for under these circumstances the common long-styled primrose produces a considerable number of capsules. There can, therefore, be no doubt that the fertility of these plants was greatly impaired. The loss is not correlated with the colour of the flower; and it was to ascertain this point that I made so many experiments. As the parent-plant growing in Edinburgh was found by Mr. Scott t

veris, B

of Linn., P. of

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-grandchildren,-and lastly, from their seed 8 long-styled and 2 short-styled great-great-great-grandchildren. In this last generation short-styled plants appeared for the first time in the course of the six generations,-the parent long-styled plant which was

s was carefully observed; but I must premise that I cannot give any satisfactory standard of comparison as far as the number of the seeds 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

lowers on the illegitimate plant having produced only one capsule proves how sterile it was. To show that the conditions of life were favourable, I 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 deteriorated condition. This was manifestly the c

quite impotent; for I obtained from a LEGITIMATE 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. Altogether, 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 doubts 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 were legitimately f

rofusely, and especially by the long endurance of the flowers. For instance, I fertilised many flowers on these plants, and fifteen days afterwards (namely on March 22nd) I fertilised numerous long-styled and short- styled flowers on common cowslips growing c

ilised with their own pollen, produced 15 capsules, containing an average of 16.3 seeds. As already stated, the probable average with legitimate plants for a union of this nature is rather above 20 seeds. These plants were remarkably healthy and vigorous, as long as they were kept under highly favourable conditions

, containing on an average 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 ster

lf would have added much to their vigour. (5/11. For full details of this experiment, see my 'Effects of Cross and Self- fertilisation' 1876 page 220.) When these illegitimate 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

RED VARIETY OF

the stamens in length, position and size of their pollen-grains resemble those of the short-styled form, whilst the pistil resembles that of the long-styled form both in length and in the structure of the stigma. Hence the self-union of this variety is, in fact, a legitimate union, and consequently is highly fertile. Mr. Scott further s

tyled in structure, whilst remaining long-styled in function. Short-styled cowslips, when insects are excluded, are extremely barren: for instance, on one occasion six fine plants produced only about 50 seeds (that is, less than the product of two good capsules), and on another occasion not a single capsule. Now, when the above twelve apparently short-styled seedlings were similarly treated, nearly all produced a great abundance of capsules, containing numerous seeds, which germinated remarkably well. Moreover three of these plants, which during the first year were furnished with quite short pistils, on the following year produced pistils of extraordinary length. The greater number, therefore, of these short-styled plants could not be dis

projected quite above the anthers, and the stigma resembled that of the long-styled form. In this condition it produced spontaneously a vast number of fine capsules, six of which contained almost exactly the same average number as before, namely 34.3, with a maximum of 38. Four flowers on this plant, legitimately fertilised with pollen from a short-styled cowslip, yielded capsules with an average of 30.2 seeds. Fourthly another short-styled plant spontaneously produced in 1865 an abundance of capsules, ten of which contained an average of 35.6 seeds, with a maximum of 54. In 1866 this same plant had become in all respects long-styled, and ten capsules gave almost exactly the same average as before, namely 35.1 seeds, with a maximum of 47. Eight flowers on this plant, legitimately fertilised with pollen from a short-styled cowslip, produced six capsules, with the high average of 53 seeds, and the high maximum of 67. Eight flowers were also fertilised with pollen from a long-styled cowslip (this being an illegitimate union), and produced seven capsules, containing an

n out of doors I never obtained a higher average than 41 seeds. Now two of the equal- styled plants, grown out of doors and spontaneously SELF-FERTILISED, gave averages of 44 and 45 seeds; but this high fertility may perhaps be in part attributed to the stigma receiving pollen from the surrounding anthers at exactly the right period. Two of these plants, fertilised with pollen from a short-styled cowslip (and this in fact is a legitimate union), gave a lower average than when self-fertilised. On the other hand, another plant, when similarly fertilised by a cowslip, yielded the unusually high average of 53 seeds, with a maximum of 67. Lastly, as we have just seen, one of these plants was in an almost exactly intermediate condition in its female organs

amens seated 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 sexual organs which properly exist in the two distinct forms, was inherited with much force. Thirty- six seedlings were also raised from long and short-styled common cowslips, crossed with pollen from the equal-styled variety.

MON

/13. 'Botanische Zeitung' 1865 page 13.); for he found that the long-styled form was absolutely sterile with its own pollen, whilst my long-styled seedlings and the parent-plants yielded a fair supply of seed when self-fertilised. Plants of the long-styled form of Pulmonaria angustifolia were, like Hildebrand's plants, absolutely sterile with their ow

num fa

that the usual rule of illegitimately fertilised long-styled plants tending much more strongly than short-styled plants to reproduce their own form here holds good. The illegitimate plants derived from both forms flowered later than the legitimate, and were to the latter in height as 69 to 100. But as these illegitimate plants were descended from parents f

TIMATE OFFSPRING OF HETEROSTYLED

erile hybrids, as Max Wichura has well shown, are sometimes much dwarfed in stature, and have so weak a constitution that they are liable to premature death (5/15. 'Die Bastardbefruchtung im Pflanzenreich' 1865.); 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 illegitimate plant. When two species are crossed and they 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 sterile. But there are marked exceptions, as shown by Gartner, to these rules. So it is with illegitimate unions and illegitimate offspring. Thus the mid- styled form of Ly

gma some time previously, is entirely destroyed. Exactly the same thing occurs with the two forms 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-four hours afterwards legitimately with polle

of the same trimorphic or dimorphic heterostyled species are obviously identical in general structure, with the exception of the reproductive organs, and as they are identical in general constitution (for they live under precisely the same conditions), the sterility of their illegitimate unions and that of their illegitimate offspring, must depend exclusively on the nature of the sexual elements and on their incompatibility for uniting in a particular manner. And as we have just seen that distinct species when crossed resemble in a whole series 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 detecting any differences sufficient to account for certain species crossing with the greatest ease, whilst other closely allied species cannot be crossed,