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Show 238 HYBRIDISM. [CHAP. VIII. derived from hostile witnesses, who i_n ~11 other ca.ses consider fertility and sterility as safe critenons of specific distinction. Gartner kept during several years .a dw~rf kind of maize with yellow seeds, a~d ~ tall van~ty With red seeds, growing near each other In his garden, and althouO'h these plants have separated sexes, they never naturall0 crossed. I-Ie then fertilised thirteen flo'Yers of the one ~ith the pollen of the. other; but only a single head produced any seed, and this one head produced only five grruns. Manipulation in this case could not have been injurious, as the plants have separated. s~xes. No. one, I believe has suspected that these varieties of maize are distinct species ; an~ it is important to notice that ~~1~ hybrid plants thus Tais~d were themselves perfectly fertile, so that even Gartner did not venture to consider the two varieties as specifically distinot. . . 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. ~-low far these exper~ments may be trusted, I know not, but the fo:ms expmimentised 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 se~ms at first quite incredible·' but it is the re.s ult of an astonish- ing 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 yellow and white varieties of the same species of Verbascun1 when intercrossed produce less seed, than do eith~r coloured varieties when fertilised with pollen froin their own coloured flowers. Moreover, he asserts that wh~n yellow and white varieties of one species are crossed with :yellow and white varieties of a distinct species, more seed 1s produced by the crosses between the same coloured flowers, than between those which are differently coloured. Yet these varieties of V erbascum present no other di:ffer~nce besides the mere colour of the flower ; and one varwty can sometimes be raised from the seed of the other. . From observations which I have made on certam CH.lP. VIII.] FERTILITY OF MONGRELS 239 varieties of hollyhock, I am inclined to suspect that they present analogous facts. lColreuter, :whose accuracy has been confirmed by every subsequent .observer, has proved the remarkable fact? that one vanety of the common tobacco is more fertile, when cro~se~ with a widely distinct species, than are. the other varieties. He experimentised on five forins whiCh are commonly reputed to be varieties and whicl~ he tested by the severest. trial, namely, by reciprocal cro~ses, and he found their mongrel offspring perfectly fertile. But one of these five varieties, ·when used either a.s father or moth~r, and cros~ed with the Nicotiana glntin? sa, always Jielded hybnds not so sterile as those whJCh were produced from the four other varieties when crossed w~th N. gl~tinosa. Hence the reproductive systmn ?f this one vanety must have been in some manner and In some degree modified. . ~rom t~ese f~~ts ; from . th.e great difficulty of ascertalning the Infertihty of varieties in a state of nature for a supposed variety if infertile in any degree would g~nerally be ranked as species; from man selecting only external ?hara~te~s in the production of the most distinct domestic variet~es, and from. not wishing or being able. to prod.uce recondite and functional differences in the reproductive system ; from these several considerations and fact.s, .I do not think that the very general · fertility of varieties can be proved to be of universal occurrence or to f~rm a fundamental distinction between varieties ~nd species. T~e general fertility of varieties does not seem to. me sufficient to overthrow the view which I have taken ~Ith ;espect to the, very general, but not invariable, steril- 1 Yo .first crosses and of hybrids, namely that it is not a sp~Cial ~ndowment, but is incidental on slowly acquired mfodhificat1ons, lll:ore especially in the reproductive svstems o t e forms whiCh are crossed. " .f!'!!brids and Mongrels compared, independently of their ferpil~ty .-In~~pendentl y of the question of fertility, the offsprin~ of species ~hen crossed and of varieties when crossed may e compared In several other respects. Gartner, whose |