Chaf. X. PREPOTENT POLLEN. 399 



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 self- 

 fertilised opponents. Of eight pairs of Lupinus luteus, 

 all but two of the crossed were taller ; of eight pairs 

 of Beta vulgaris all but one ; and of fifteen pairs of Zea 

 mays all but two were taller. Of fifteen pairs of Lim- 

 nanthes douglasii, and of seven pairs of Lactuca saliva, 

 every single crossed plant was taller than its self-fer- 

 tilised opponent. It should also be observed that in 

 these experiments no particular care was taken to cross- 

 fertilise the flowers immediately 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 

 constitutional vigour of the crossed seedlings. The 

 evidence of prepotency is here deduced from the com- 

 parative growth of the two lots of seedlings ; but we 

 have similar evidence in many cases from the niucn 

 greater fertility of the non-castrated flowers on the 

 mother-plant, when these received at the same time their 

 own pollen and that from a distinct plant, in comparison 

 with the flowers which received only their own pollen. 



From the various facts now given on the spontaneous 

 intercrossing of varieties growing near together, and on 



