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Show 396 MEANS OF CROSS-FERTILISATIO:K. CHAP. X. affected, for they grew much more vigorously than the self-fertilised seedlings from the Raggecl Jack planted at the san1o ti1ne and under the sa1ne conditions. Secondly, I placed on several stio·1nas of a long-stylocl cowslii (Prinuda veris) plenty of pollen frmn tho same plant, ancl after twenty-four hours adJod some from a short-styled dark-rod Polyanthus, which is a variety of the cowslip. Fro1n the fio'vvers thus treated thirty seedlings were rais d, and all those without exception bore reddish flowers ; so that tho effect of the plant's own pollen, though placocl on the stig1nas twontyfuur hours previously, was quite destroyed by that of the red variety. It should, however, be observed that these plants are dimorphic, and that the second union was a legitimate one, whilst tho first was illegiti1nate; but flowers illegitimately fertilised with their own pollen yield a moderately fair supply of seeds. vVe have hith rto considered only the prepotent fertilising power of pollen fro1n a distinct variety over a plant's own I ollen,-both kinds of pollen being placed on th sam stig1na. It is a much n1ore re· markable fact that poll n from another individual of the same variety is prepotent over a plant's own pollen, as shown by the superiority of the seedlings raised from a cross of this kind over seedlings fr01n selffertilised flowers. ~rhus in Tables A, B, and C, there are at least fifteen species which arc self-fertile when insects are excluded; and this implies that their stigmas must receive their own pollen ; novortholess, 1nost of the seedlings which were raised Ly fertilising tho noncastrated flowers of these fifto n species with p~llen from another plant wore greatly superior, in he.Igh~ weight, and fertility, to ·the self-fertilised offspnng. * These fifteen species consist of an<l ltdea Limnanthes douglla tii, Brassic.a oleracea, R eseda odoratct Papave1· v' agum, rr rt.s c a1·~• a ocu a a, CHAP. X. PREPOTENT POLLEN. 397 For instance, with Ipomma purpurea every single inte1~crossed plant exceeded in height its self-fertilised opponent until tho sixth generation; and ~o it was with Mimulus ltdeus until the fourth generation. Out of six pairs of erossocl and self-fertilised eabbages, every one of the former was much heavier than the latter. With Papaver vagum, out of fifteen pairs, all but two of the crossed plants were taller than their selffertilised opponents. Of eight pairs of Lupin-us luteus, all but two of the crossed were taller; of eight pairs of Beta vulgaris all hut one ; and of :fifteen pairs of Zea mays all but two were taller. Of fifteen pairs of Limnanthes douglasii, and of seven pairs of Lactuea sativa, every single crossed plant was taller than its self-fertilised opponent. It should also be observed that in these experiments no particular care was taken to crossfertilise the flowers im1nediately after their expansion ; it is therefore almost certain that in many of these cases some pollen from the same flower will have already fallen on and acted on the stigma. There can hardly be a doubt that several other species of which the crossed seedlings are more vigorous than the self-fertilised, as shown in Tables A, B, and C, besides the above :fifteen, must have received their own pollen and that from another plant at nearly the same time ; and if so, the same remarks as those just given are applicable to them. Scarcely any result from my experiments has surprised me so much as this of the prepotency of pollen from a distinct individual over each plant's own pollen, as proved by the greater co~stitutional vigour of the crossed seedlings. The evidence of prepotency is here dedueed from the Beta vulgads, Lupinus luteus, Vandellia nttmmula1·1'jolia, Lac-lpoma. a purpurta, Mimnlus luteus tu.ca sc;r.ii't:a, and Zea. mays. Calceoluria, Verbas~um tlwpsus: |