HYBRIDIZATION. 7G3 



Hybrids rarely produce fertile seeds for many generations, 

 and hence, cannot be generally perpetuated with any certainty 

 by them ; if they should be of a woody nature, however, they 

 may be readily propagated by budding, grafting, &c. Hybrids 

 may be rendered fertile by the application of the pollen of one 

 of their parents ; the offspring in such a case resembles closely 

 the parent from which the pollen was obtained. By the suc- 

 cessive impregnation of hybrids through three, four, or more 

 generations with the pollen of either of their parents, they 

 revert to their original male or female type; thus, when the 

 hybrid is successively impregnated by the pollen of its male 

 parent, it reverts to the male type ; and M^hen with that of the 

 female, to the female type. The influence of the latter is, 

 however, more gradual. 



Hybrids rarely occur in -vvild plants. This arises chiefly from 

 the following causes ; thus, in the first place, the stigma is more 

 likely to be impregnated with the pollen from the anthers 

 immediately surrounding it, than by that of others remote from 

 it ; and secondly, the stigma has a sort of elective affinity or 

 natural preference for the pollen of its own plant, so much so, 

 indeed, that Gaertner found, that if the natural pollen and that 

 of another species be applied to the same stigma at the same 

 time, the latter remained inert, and the former alone fecundated 

 the ovules ; and, moreover, that when the natural was apphed a 

 short period subsequently to the foreign pollen, the seeds thus 

 produced never formed hybrids. Hybrids appear to be produced 

 more frequently in wild plants when the sexes are in separate 

 flowers, and more especially when such flowers are on different 

 plants. Recent investigations show that hybrids are far more 

 common amongst wild plants than the above observations 

 indicate. 



Hybrids are, however, frequently produced artificially by 

 gardeners applying the pollen of one species to the stigma of 

 another, and in this way, important and favourable changes are 

 effected in the characters of our flowers, fruits, and vegetables. 

 Such are not, however, commonly true hybrids, but simple cross- 

 breeds. 



Eecent investigations would appear to show, that a similar 

 law as regards hybridation occurs in the Cr}'ptogamia as in the 

 Phanerogamia. Thus, Thuret has succeeded in fertilizing the 

 spores of Fucus vesiculosus wdth the spermatozoids of Fucus 

 serratus, an allied species ; but he failed in his attempts to 

 fertilize the spores of one genus of the Melanosporeous Algse 

 by the spermatozoids of another. No other direct evidence 

 has at present been adduced as to the hybridization of Crypto- 

 gamous plants, but there can be but little doubt, that hybrid 

 Ferns are sometimes produced when a number of species are 

 cultivated together, for it has been noticed, that under such 



