Different Forms of Flowers on Plants of the Same Species

Page 116

216 ILLEGITIMATE OFFSPRING OF CHAP. v. 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 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 illegiti­mate plant, and produced four capsules, containing only 32 · 2 seeds instead of about 64 seeds, which is the norro.al average for legitimate short-styled plants legitimately crossed. By looking back, it will be seen that I raised at first from a short-styled plant fertilised with its own­form pollen one long-sty led and seven short-sty led illegiti1nate seedlings. These seedlings were legiti­mately intercrossed, and from their seed fifteen plants were raised, grandchildren of the first illegitimate union, and to n1y surprise all proved short-styled. Twelve short-sty led flowers borne by these grand­children were illegitimately fertilised with pollen taken from other plants of the sa1ne 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 such a union. Six flowers were also legitimately fertilised with pollen from an illegitimate long-sty led 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 Transmissiofb of Form, Constitution, and Fertility of the Illegitimate Offspring of Primu~a Sinensis.-ln regard to the long-sty led plants, theu CHAP. V. HETEROSTYLED DIMORPHIC PLANTS. 217 illegitimate offspring, of which fifty-two were raised in the course of two generations, were all long-styled.* These plants grew vigorously; but 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 respect to the short-styled plants, twenty-four out of twenty-five of their illegitimate offspring were short­styled. 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 own­form 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 fertiliseu, an average of 64 seeds, with a possible maximum 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 from an ordinary marriage ; but that only three would be born from an incestuous marTiage. According to the analogy of P·rimula Sinensis, the children of such * Dr. Hildebrand, who first c~lled at~ention to this subject ( Bot. Ze1tung,' 1864, p. 5), raised from a similar illegitimate union seventeen plants, of which four­teen were long-styled and three short-styled. From a short-styled plant illegitimately fartili:Jed with its own pollen be raised fourteen plants, of which eleven were short­styled and three long-styled.