136 PROPAGATION OF PLAK-TS. 



mental faculties to assist in impressing and perpetuating 

 the male or other sexual characteristics, as in the animal 

 kingdom. 



As I have shown in the case of the Abutilons, sexual 

 affinity presents wide variations, which can only he defi- 

 nitely determined by actual experiments upon the plants 

 themselves. No theory will explain why the pollen of a 

 plant cannot fertilize its own ovules, while it has an 

 affinity for, and is potent upon, those of another closely 

 allied plant. If the pollen from several different varieties 

 or species is applied simultaneously to the same stigma, 

 it is quite evident that only one kind will be potent, and 

 that one from the plant possessing the greatest sexual 

 affinity with the plant pollinated. 



It is generally supposed that in all the higher orders 

 »f plants the ovule must be fertilized in order to secure 

 perfect and fertile seed, but there are some few in- 

 stances on record where seeds are supposed to have been 

 produced in the absence of fertilization, or, as it has been 

 termed, by Parthenogenesis. Prof. Asa Gray thinks it 

 does sometimes occur among Dioecious plants. A cen- 

 tury ago (1786) Lazaro Spallanzani, published his ob- 

 servations on the fecundation of plants, and claimed 

 to have found pistillate blossoms of the Hemp producing 

 fertile seed in the absence of pollen. A half century later 

 Drs. Charles Naudin and Joseph Decaisne are said to have 

 confirmed the fact by raising seedlings from Euphor- 

 biaceous plants, also from the common Bryony, which 

 were kept from all access of pollen. While I am not 

 disposed to question the statements of such high botan- 

 ical authorities, or to attempt to offset their experiments 

 with those of my own, still I think there is room for a 

 doubt in this matter, and especially when we take into 

 consideration the present undetermined boundaries of 

 species. 



The question arises, may not the pollen of some other 



