258 FERTILITY OF VARIETIES WHEN CROSSED. [Chap. IX. 



other; but only a single head produced any seed, and this one 

 head produced only five grains. Manipulation in this case could 

 not have been injurious, as the plants have separated sexes. No 

 one, I believe, has suspected that these varieties of maize are 

 distinct species; and it is important to notice that the hybrid 

 plants thus raised were themselves perfectly fertile ; so that even 

 Gartner did not venture to consider the two varieties as specifically 

 distinct. 



Girou de Buzareingues crossed three varieties of gourd, which 

 like the maize has separated sexes, and he asserts that their mutual 

 fertilisation is by so much the less easy as their differences arc 

 greater. How far these experiments may be trusted, I know not ; 

 but the 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 conclusion. 



The following case is far more remarkable, and seems at first 

 incredible ; but it is the result of an astonishing number of experi- 

 ments 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 coloured 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 

 coloured flowers, than between those which are differently coloured. 

 Mr. Scott also has experimented on the species and varieties oi 

 Verbascum ; and although unable to confirm Gartner's results on 

 the crossing of the distinct species, he finds that the dissimilarly 

 coloured varieties of the same species yield fewer seeds, in the pro- 

 portion of 86 to 100, than the similarly coloured varieties. Yet these 

 varieties differ in no respect except in the colour of their flowers ; 

 and one variety can sometimes 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 experi- 

 mented 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 the 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 



