37O IMPREGNATION OF THE SEED. CHAP. VII. 



Many experiments of a similar nature were tried 

 on other plants also ; from which it appeared that 

 improved varieties of every fruit and esculent plant 

 may be obtained by means of artificial impregna- 

 tion, as they were obtained in the cases already 

 stated. Whence Mr. Knight thinks that this pro- 

 miscuous impregnation of species has been intended 

 by nature to take place, and that it does in fact 

 often take place, for the purpose of correcting 

 such accidental varieties as arise from seed, and of 

 confining them within narrower limits. All which 

 is thought to be countenanced from the considera- 

 tion of the variety of methods which nature em- 

 ploys to disperse the pollen, whether by the elastic 

 spring of the anthers, the aid of the winds, or the 

 instrumentality of insects. 



But although he admits the existence of vegetable 

 hybrids, that is, of varieties obtained from the in- 

 termixture of different species of the same genus, 

 yet he does not admit the existence of vegetable 

 mules, that is of varieties obtained from the inter- 

 mixture of the species of different genera ; in at- 

 tempting to obtain which he could never succeed, 

 in spite of all his efforts. Hence he suspects that 

 where such varieties have been supposed to take 

 place, the former must have been mistaken for the 

 latter. It may be said, indeed, that if the case 

 exists in the animal kingdom, why not in the ve- 

 getable kingdom ? to which it is perhaps difficult to 



