ly 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 Gaertner 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 are greater. How far these
experiments may be trusted, I know not; but the forms experimentised on,
are ranked by Sagaret, who mainly founds his 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 astonishing number of experiments
made during many years on nine species of Verbascum, by so good an observer
{271} and so hostile a witness, as Gaertner: 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
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.

Koelreuter, 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