CROSS IMPREGNATION. 265 



with similar phenomena happening- in the animal 

 kingdom. In the latter it is only nearly allied species 

 which hybridise. The mule and hinno are hybridal 

 varieties of the horse and ass ; but of this there are 

 but few exactly similar examples among plants. 

 Among- the latter, family affinities only can be 

 affected by the pollen of each other. Attempts have 

 been made to show that many of our species are only 

 amalgamations of others ; and that all intermediate 

 species between the first and the last of a genus, are 

 only adventitious creations ; yea more, that the 

 varied vegetable king-dom originated from a few 

 Fuel that first sprung up in the waters, and after- 

 wards spread over the face of the earth. But this 

 view is wholly visionary ; being applicable to varieties 

 of plants only, not to species. 



Animal hybrids have a peculiar characteristic, viz. 

 that though the progeny from the cross partake of 

 the form and muscular powers of both sire and dam, 

 they, with very few exceptions, are denied the power 

 of reproduction. Real hybrids have been raised 

 between two species of Verbdscum many years ago 

 by Mr. Haworth, and lately between two species of 

 Digitalis by professor Henslow and Mr. Denson. 

 The hybrids of Digitalis were barren, and in this 

 resembled those of animals, but among varieties of 

 species, some of which, from the monstrous fulness 

 of the flower, are indeed sterile, yet in general they 

 are prolific, and consequently capable not only of 

 perpetuating themselves, but of being multiplied into 



