HYBRIDISING AND CROSS-BREEDING. 1 29 



tion has taken place, which in different genera requires very 

 different periods as in Nicotiana two hours, in Malva and 

 Hibiscus three, in Dianthus five or six, &c. the application of 

 the native pollen has no effect. The fruit is not more perfect, 

 the seeds more numerous or different in their nature, nor is 

 any superfoetation effected ; but the small number of seeds is 

 precisely such as would have been generated by the simple 

 hybrid fecundation. Two kinds of seeds were, however, pro- 

 duced in Nicotiana rustica impregnated with N. paniculata, by 

 dusting half of the stigma with the strange pollen before the 

 expansion of the corolla, and the remainder after a lapse of 

 twenty hours ; and the conditions of the experiment were va- 

 ried till the pure type vanished entirely, and merely the usual 

 bastard type made its appearance. The account of the experi- 

 ments is very interesting, but too long for extraction. 



A mixture of pure and hybrid seeds can only take place 

 when the strange pollen is applied first, and the native pollen 

 before the intrusive has affected the whole of the ovary, either 

 by impregnating the ovules or destroying their vitality, or before 

 the surface of the stigma has undergone such a change as to 

 make impregnation impossible ; or in the case where the native 

 pollen is first applied in extremely small quantity, and the 

 intrusive pollen after a very short interval. 



The occurrence, however, as said above, of the pure and 

 bastard type from the seed of the same plant is extremely rare, 

 and can only happen under very peculiar circumstances ; but 

 even a threefold produce is not absolutely without example, the 

 successive impregnation of Nicotiana paniculata with N. quad- 

 rivalvis and N. Langsdorfii having given rise to three types ; 

 three plants proving the pure species, four the hybrid N. 

 paniculato-Langsdorfii, and a single individual N. paniculato- 

 quadrivalvis. A repetition of the experiment produced merely 

 the latter hybrid form. 



An important deduction arises from these exceptional cases. 

 Even in this compound fecundation there is no confusion of 

 types, but the hybrids are exactly such as would have arisen 

 from a simple impregnation with the pollen of one allied 

 species. In the course of a long series of experiments, seeds 

 have occurred very rarely containing more than one embryo ; * 



* Mr Thwaites has found a compound embryo in the genus Fuchsia. 

 Two forms were grafted together, one possessing the character of F. fulgent, 

 the other of F. magellanica. It is clear, however, from his account, that 

 they did not arise from a union of pure species. The seedlings were too 

 varied to allow of such a supposition. See Ann. of Nat. Hist., 2d series, 

 vol. i. p. 163. 



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