10 OBSERVATIONS UPON MULING AMONG PLANTS. 



mules appear to become less fruitful as they recede from their 

 original stock — a fact exactly contrary to what is exhibited by 

 varieties. Tiie more fruitful hybrids retain their typical form 

 after many generations, such as Aquilegia atropurpureo-cana- 

 densis, &c. ; the greater part, however, yield forms deviating 

 more or less from the normal type, the variations being chiefly 

 confined to the flower. Hippeastrum Johnsoni {regio-vittatum) 

 was observed by Mr. Herbert, when fertilized with its own 

 pollen, to have less beautiful and smaller blossoms. Differences, 

 however, of general habit, or of other especial organs, occa- 

 sionally take place. In cases where impregnation is not effected 

 with their own pollen, mules are often capable of fertilization 

 with the parent pollen, for which in general they exhibit a 

 greater elective affinity than for their own, and the same may 

 sometimes be said of certain pure species. Of the two kinds of 

 pollen, that from the male and that from the female parent, the 

 greater elective affinity appears to reside with that parent to 

 which the hybrid bears the closest resemblance. The impreg- 

 nation of fertile mules with their own pollen is a very fruitful 

 source of florists' varieties, as well as that of the female parent 

 with the pollen of the mule. 



When the hybrid is impregnated by the original male parent, 

 the result is much the same as in simple hybrids self- fertilized, 

 both in respect of the types produced and the degree of fertility. 

 Various forms are raised from one capsule, and the different in- 

 dividuals do not present the same degree of susceptibility for 

 impregnation. Different capsules, too, offer very different re- 

 sults. When these mules are in turn self-impregnated, either 

 naturally or artificially, they are commonly more fruitful than 

 they were after the first impregnation. As might be expected, 

 the seedlings approach nearer to the paternal type : when the 

 original simple mules in their second generation and the pa- 

 ternal hybrids of the second degree exhibit a return to the type 

 of the maternal ancestor, such a return is never perfect, but only 

 partial. 



The tendency of varieties to return to the maternal type 

 seems to be a peculiarity general to the vegetable kingdom, 

 especially if left to themselves, free from the trammels of culti- 

 vation. This return, however, in the second generation of 

 simple hybrids, or of paternal mules of the second degree, is 

 always effected by fructification, and not by any other mode of 

 propagation. It seems also more easy than the approach to the 

 paternal type, though in neither case does it take place to a 

 considerable extent, nor does it take place in all genera, and 

 when it does occur the produce is less fertile. Mr. Herbert 

 believed that such deviations from the normal type might arise, 

 when the proper pollen was insufficient for impregnation, from 



