166 HYBRIDISM. Chap. XIX. 



and trimorphic plants, when illegitimately fertilised, that is, 

 by pollen taken from stamens not corresponding in height 

 with the pistil, differs much in degree, up to absolute and 

 utter sterility ; just in the same manner as occurs in crossing 

 distinct species. As the degree of sterility in the latter case 

 depends in an eminent degree on the conditions of life being 

 more or less favourable, so I have found it with illegitimate 

 unions. It is well known that if pollen of a distinct species 

 be placed on the stigma of a flower, and its own pollen be 

 afterwards, even after a considerable interval of time, placed 

 on the same stigma, its action is so strongly prepotent that it 

 generally annihilates the effect of the foreign pollen ; so it is 

 with the pollen of the several forms of the same species, for 

 legitimate pollen is strongly prepotent over illegitimate 

 pollen, when both are placed on the same stigma. I ascer- 

 tained this by fertilising several flowers, first illegitimately, 

 and twenty-four hours afterwards legitimately, with pollen 

 taken from a peculiarly coloured variety, and all the seedlings 

 were similarly coloured ; this shows that the legitimate 

 pollen, though applied twenty-four hours subsequently, had 

 wholly destroj'ed or prevented the action of the previously 

 applied illegitimate pollen. Again, as, in making reciprocal 

 crosses between the same two species, there is occasionally a 

 great difference in the result, so the same thing occurs with 

 trimorphic plants ; for instance, the mid-styled form of 

 Lythrum salicaria could be illegitimately fertilised with the 

 greatest ease by pollen from the longer stamens of the short- 

 styled form, and yielded many seeds ; but the short-styled form 

 did not yield a single seed when fertilised by the longer 

 stamens of the mid-styled form. 



In all these respects the forms of the same undoubted 

 species, when illegitimately united, behave in exactly the 

 same manner as do two distinct species when crossed. This 

 led me carefully to observe during four years many seedlings, 

 raised from several illegitimate unions. The chief result is 

 that these illegitimate plants, as they may be called, are not 

 fully fertile. It is possible to raise from dimorphic species, 

 both long-styled and short-styled illegitimate plants, and 

 from trimorphic plants all three illegitimate forms. These 



