| OCR Text |
Show 306 UNIFORM COLOUR OF r.rHE FLOWERS CHAP. Vlll. valuable experin1ents on hybrid Abutilons, that the union of brothers and sisters, parents and children, and of other near . relations is highly injurious to the fertility of the offspring. In one case, moreover, seedlinD'S fro1n such near relations possessed very weak b . constitutions.* This same observer also found t three plants of a Bignonia growing near together .. l-Ie fe~·tilised twenty-nine flowers on one of them w1th then own pollen, and they did not set a single capsule. Thirty flowers were then fertilised with pollen from a distinct plant, one of the three growing together, and they yielded only two capsules. Lastly, five flowers were fertilised with pollen from a fourth plant growing at a distanee, and all five produced. capsules. It seems therefore probable, as Fritz M iiller suggests, that the three plants growing near together were seedlings from the same parent, ancl that from being closely related they had little power of fertilising one another.t Lastly, the ft-.,ct of the intercrossed plants in Table A not exceeding in height the self-fertilised plants in a greater and greater degree in the later generations, is probaLly the result of their having become 1nore and more closely inter-related. Uniform Colour of the Flowers on Plants, self f ertilised and grown under si,milar conditions for se'veral Generations.- At the commencen1ent of 1ny experiments, the parent-plants of Min~ulus luteus, Ipom cea purp~t:ea, D1:ardhus caryophyllus, and P etunia violacea, ra1sed from purchased seeds, varied greatly in the colour ------- * 'J enait::che Zeitschrift fiir Naturw. ;' B. vd., pp. 22 and 45, 1872; ancl 1873, pp. 441- 450. t 'Bot. Zeitung,' 1868, p. 626. t Some n·markable ca~ es nre giveu in my 4 Variation un :er Domestic:.tion' ( chnp. xvii: 20~ e:dit. vol. 2, p. 121 ) of ll ybrJds o Gladiolus nnd Cistus, any 0110 of which could be fertilised by poll~n from any other, but nut by ItS owu pollen. CHAP. VIII. ON SELF-FERTILISED PLANTS. 307 of their flowers. This occurs with many plants which have been long cultivated as an ornament for the :flower-garden, and which have been propagated by seeds. The colour of the flowers was a point to which I did not at first in the least attend, and no selection whatever was practised. Nevertheless, the flowers p~oduced by the self-fertilised plants of the above four species became absolutely uniform in tint, or very nearly so, after they .had been grown for some generations under closely similar conditions. The intercrossed plants, which were n1ore or less closely inter-related in the later generations, and which had been likewise cultivated all the tin1e under similar conditions, beca1ne more uniform in the colour of theit· flowers than were the original parent-plants, but much less so than the self-fertilised plants. When self-fertilised plants of one of the later generations were crossed with a fresh stock, and seedlings thus raised, these presented a wonderful contrast in the diversified tints of their flowers compared with those of the self-fertilised seedlings. As such cases of flowers becoming uniformly coloured without any aid from. selection seem to me curious, I will give a full abstract of my observations. Mimulus lute~ts.-.A .. tall variety, bearing large, almost white flowers blotched with crimson, appeared amongst the intercrossed and self-fertilised plants of the third and fourth generations. This variety increased so rapidly; that in the sixth generation of self-fertilised plants every single one consisted of it. So it was with all the many plants which were raised, up to the last or ninth self-fertilised generation. Although this variety first appeared amongst the intercrossed plants, yet from their offspring being intercrossed in each succeeding generation, it never prevailed. amongst X 2 |
