Chap. VIII. STEKILITY, 249 



that close interbreeding lessens fertility, and, on the 

 other hand, that an occasional cross with a distinct in- 

 dividual or variety increases fertility, that I cannot doubt 

 the correctness of this almost universal belief amongst 

 breeders. Hybrids are seldom raised by experimen- 

 talists in great numbers ; and as the parent-species, or 

 other allied hybrids, generally grow in the same garden, 

 the visits of insects must be carefully prevented during 

 the flowering season : hence hybrids will generally be 

 fertilised during each generation by their own indi- 

 vidual pollen ; and I am con viced that this would be 

 injurious to their fertility, already lessened by their 

 hybrid origin. I am strengthened in this conviction 

 by a remarkable statement repeatedly made by 

 Gartner, namely, that if even the less fertile hybrids 

 be artificially fertilised with hybrid pollen of the same 

 kind, their fertility, notwithstanding the frequent ill 

 effects of manipulation, sometimes decidedly increases, 

 and goes on increasing. Now, in artificial fertilisation 

 pollen is as often taken by chance (as I know from my 

 own experience) from the anthers of another flower, as 

 from the anthers of the flower itself which is to be 

 fertilised ; so that a cross between two flowers, though 

 probably on the same plant, would be thus effected. 

 Moreover, whenever complicated experiments are in 

 progress, so careful an observer as Gartner would have 

 castrated his hybrids, and this would have insured in 

 each generation a cross with the pollen from a distinct 

 flower, either from the same plant or from another plant 

 of the same hybrid nature. And thus, the strange fact of 

 the increase of fertility in the successive generations 

 of artificially fertilised hybrids may, I believe, be ac- 

 counted for by close interbreeding having been avoided. 

 Now let us turn to the results arrived at by the third 

 most experienced hybridiser, namely, the Hon. and 



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