242 HYBRIDS BIGENEES. [BOOK n. 



themselves, and capable of performing all its vital functions 

 as perfectly as either parent, with the exception of its being 

 unequal to perpetuating itself permanently by seed ; should 

 it not be absolutely sterile, it will become so after a few 

 generations. It may, however, be rendered fertile by the 

 application of the pollen of either of its parents ; in which 

 case its offspring assumes the character of the parent by 

 which the pollen was supplied. This power of hybridising 

 appears to be far more common in plants than in animals ; 

 for, while only a few animal mules are known, there is 

 scarcely a genus of domesticated plants in which this effect 

 cannot be produced by placing the pollen of one species upon 

 the stigma of another. It is, however, in general only 

 between nearly allied species that this intercourse can take 

 place : those which are widely different in structure and 

 constitution not being capable of any artificial union. Thus 

 the different species of Strawberry, of certain tribes of 

 Pelargonium, and of Cucurbits, intermix with abundant 

 facility, there being a great accordance between them in 

 general structure and constitution; but no one has ever 

 succeeded in compelling the Pear to fertilise the Apple or 

 the Gooseberry the Currant. And as species that are very 

 dissimilar appear to have some natural impediment which 

 prevents their reciprocal fertilisation, so does this obstacle, 

 of whatever nature it may be, in general present an insuperable 

 bar to the intercourse of different genera. The stories that 

 are current as to the intermixture of Oranges and Pome- 

 granates, of Roses and Black Currants, and the like, may be 

 set down to pure invention. 



It is, nevertheless, said, that bigeners, that is to say, 

 mules between different genera, have in some few cases been 

 artificially obtained. Kolreuter obtained such between 

 Malvaceous plants ; Gsertner, between Datura and Henbane 

 and Tobacco; Wiegmau, between a Garden Bean and a 

 Lentil ; and there are other cases. But all such productions 

 were as short-lived and sickly as they were monstrous. 



As this power of creating mule plants fertile for two or 

 three generations incontestably exists, it is not to be wondered 

 at, that in wild nature hybrid varieties should be far from 



