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Show 234 ILLEGITIMATE OFFSPRING OF CIIAP. v. row of these plants of the fourth illegitimate genera. tion, thus freely exposed and legitimately fertilised, produced only 3 capsules, containing on an average only 17 seeds. During the ensuing winter aln1ost all these plants died, and the few survivors were n1iserably unhealthy, whilst 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 flower-stalks than some legitimate plants with which they grew in competition; but it should be ob· served that the latter were the product of a cross with a fresh stock,-a circu1nstance which by itself would have added much to their vigour.* 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 1nust have been legitimately fertilised by insects, they yielded capsules, compared with those produced by the surrounding 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 extraordinary degree; more especially ·when the plants are exposed to ordinary conditions of life, instead of being protected in a greenhouse. Equal-styled red variety of P. veris.-Mr. Scott has described t a plant of this kind growing in the Botanic Garden of Edinburgh . . He states that it was highly self-fertile, although insects * For full details of this experiment, see my' Effects of Cross and Self-fertilisation,' 1876, p. 220. t 'Proc. Linn. Soc.' vol. viii. (1864), p. 105. CHAP. V. HETEROSTYLED DIMORPHIC PLANTS. 235 were excluded; and he explains this fact by showing, first, that the anthers and stigma are in close apposition, and that the stamens in length, position and size of ~heir 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. 1\fr. Scott further states that this variety yielded very few seeds when fertilised by either the long- or short-styled common cowslip, and, again, that both forms of the latter, when fertilised by the equal-styled variety, likewise produced very few seeds. But his experiments with the cowslip were few, and my results do not confirm his in any uniform manner. I raised twenty plants from self-fertilised seed sent me by Mr. Scott; and they all produced red :flowers, varying slightly in tint. Of these, two were strictly long-styled both in structul'e and in function; for their reproductive powers were tested by crosses with both forms of the common cowslip. Six plants were equal-styled; but on the same plant the pistil varied a good deal in length during different seasons. This was likewise the case, according to Mr. Scott, with the parent-plant. Lastly, twelve plants were in appearance short-styled; but they varied much more in the length of their pistils than ordinary shortstyled cowslips, and they differed widely frmn the latter in their powers of reproduction. Their pistils had become shortstyled 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 shod pistils, on the following year produced pistils of extraordinary length. The greater number, therefore, of these short-styled plants could not be distinguished in function from the equal-styled variety. The anthers in the six equal-styled and in the apparently twelve short-styled plants were seated high up in the corolla, as in the true short-styled cowslip; and the pollen-grains rese~bled those of the same form in their large size, but were mingled |
