44 THE ORIGIN OF SPECIES 



forms experimented on are ranked by Sageret, who 

 mainly founds his classification by the test of infertility, 

 as varieties, and Naudin has come to the same conclu- 

 sion. 



The following case is far more remarkable, and seems 

 at first incredible; but it is the result of an astonishing 

 number of experiments made during many years on nine 

 species of Verbascum, by so good an observer and so 

 hostile a witness as Gartner; namely, that the yellow and 

 white varieties when crossed produce less seed than the 

 similarly colored varieties of the same species. 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 colored flowers than between those 

 which are differently colored. Mr. Scott also has experi- 

 mented on the species and varieties of Verbascum; and 

 although unable to confirm Gartner's results on the cross- 

 ing of the distinct species, he finds that the dissimilarly 

 colored varieties of the same species yield fewer seeds, in 

 the proportion of 86 to 100, than the similarly colored 

 varieties. Yet these varieties differ in no respect except 

 in the color of their flowers; and one variety can some- 

 times be raised from the seed of another. 



Kolreuter, whose accuracy has been confirmed by 

 every subsequent observer, has proved the remarkable 

 fact, that one particular variety of the common tobacco 

 was more fertile than the other varieties, when crossed 

 with a widely distinct species. He experimented on five 

 forms which are commonly reputed to be varieties, and 

 which he tested by the severest trial, namely, by recip- 

 rocal crosses, and he found their mongrel offspring per- 



I 



