HYBRIDISM 243 



Verbascum when intercrossed produce less seed, than 

 do either coloured varieties when fertilised with pollen 

 from their own coloured flowers. Moreover, he asserts 

 that when yellow and white varieties of one species are 

 crossed with yellow and white varieties of a distinct 

 species, more seed is produced by the crosses between 

 the similarly coloured flowers, than between those 

 which are differently coloured. Yet these varieties of 

 Verbascum present no other difference besides the mere 

 colour of the flower ; and one variety can sometimes be 

 raised from the seed of the other. 



From observations which I have made on certain 

 varieties of hollyhock, I am inclined to suspect that 

 they present analogous facts. 



Kolreuter, whose accuracy has been confirmed by 

 every subsequent observer, has proved the remarkable 

 fact, that one variety of the common tobacco is more 

 fertile, when crossed with a widely distinct species, 

 than are the other varieties. He experimentised on 

 five forms, which are commonly reputed to be varieties, 

 and which he tested by the severest trial, namely, by 

 reciprocal crosses, and he found their mongrel offspring 

 perfectly fertile. But one of these five varieties, when 

 used either as father or mother, and crossed with the 

 Nicotiana glutinosa, always yielded hybrids not so 

 sterile as those which were produced from the four 

 other varieties when crossed with N. glutinosa. Hence 

 the reproductive system of this one variety must have 

 been in some manner and in some degree modified. 



From these facts ; from the great difficulty of ascer- 

 taining the infertility of varieties in a state of nature, 

 for a supposed variety if infertile in any degree would 

 generally be ranked as species ; from man selecting 

 only external characters in the production of the most 

 distinct domestic varieties, and from not wishing or 

 being able to produce recondite and functional differ- 

 ences in the reproductive system ; from these several 

 considerations and facts, I do not think that the very 

 general fertility of varieties can be proved to be of uni- 

 versal occurrence, or to form a fundamental distinction 



