270 
HYBKIDISM. 
. Chap. VIII. 
species were invariably fertile when intercrossed. But 
it seems to me impossible to resist the evidence of the 
existence of a certain amount of sterility in the few 
following cases, which I will briefly abstract. The evi¬ 
dence is at least as good as that from which we believe 
in the sterility of a multitude of species. The evidence 
is, also, derived from hostile witnesses, who in all other 
cases consider fertility and sterility as safe criterions 
of specific distinction. Gartner kept during several 
years a dwarf kind of maize with yellow seeds, and a 
tall variety with red seeds, growing near each other in 
his garden; and although these plants have separated 
sexes, they never naturally crossed. He then fertilised 
thirteen flowers of the one with the pollen of the 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. 
Giron 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 are greater. How far 
these experiments may be trusted, I know not; but the 
forms experimentised on, are ranked by Sagaret, who 
mainly founds liis classification by the test of infertility, 
as varieties. 
The following case is far more remarkable, and seems 
at first quite incredible; but it is the result of an asto¬ 
nishing number of experiments made during many years 
on nine species of Verbascum, by so good an observer 
