Chap. VIII. 
FERTILITY OF MONGRELS. 
271 
and so hostile a witness, as Gartner: namely, that yellow 
and white varieties of the same species of 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 simi¬ 
larly coloured flowers, than between those which are 
differently coloured. Yet these varieties of Yerbascum 
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 reci¬ 
procal 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 
