Chap. XVI. THE CROSSING OF VAEIETIKS. 79 



investigating the fertility of crossed varieties many source of 

 doTibt occur. Whenever the least trace of sterility between 

 two plants, however closely allied, was observed by Kolreuter, 

 and more especially by Gartner, who counted the exact num- 

 ber of seed in each capsule, the two forms wore at once ranked 

 as distinct species ; and if this rule be followed, assuredly it 

 will never be proved that varieties when crossed are in any 

 degree sterile. We have formerly seen that certain breeds of 

 dogs do not readily pair together ; but no observations have 

 been made whether, when paired, they produce the full 

 number of young, and whether the latter are perfectly fertile 

 inter se ; but, supposing that some degree of sterility weie 

 found to exist, naturalists would simply infer that these 

 breeds were descended from aboriginally distinct species; and 

 it would be scarcely possible to ascertain whether or not this 

 explanation was the true one. 



The Sebright Bantam is much less prolific than any other 

 breed of fowls, and is descended from a cross between two 

 very ditstinct breeds, recrossed by a third sub-variety. But it 

 would be extremely rash to infer that the loss of fertility was 

 in any manner connected with its crossed origin, for it mav 

 with more probability be attributed either to long-continued 

 close interbreeding, or to an innate tendency to sterility 

 correlated with the absence of hackles and siclde tail-feathers. 



Before giving the few recorded cases of forms, which must 

 be ranked as varieties, being in some degree sterile when 

 crossed, I may remark that other causes sometimes inteifere 

 with varieties freely intercrossing. Thus they may differ too 

 greatly in size, as with some kinds of dogs and fowls : for 

 instance, . the editor of the ' Journal of Horticulture, &c.,' ^ 

 says that he can keep Bantams with the larger breeds without 

 much danger of their crossing, but not with the smaller 

 breeds, such as Games, Haraburgs, &g. With plants a 

 difference in the period of flowering serves to keep varieties 

 distinct, as with the various kinds of maize and wheat : thus 

 Colonel Le Couteur ^ remarks, " the Talavera wheat, fiom 

 flowering much earlier than any other kind, is sure to 



» Dec. 18G3, p. 484. ' Oa -The Varieties of Wheat,' p. 66. 



