PLANT HYBRIDIZATION BEFORE MENDEL 95 



cerning hybridization was that a fertile cross was of itself proof 

 that the two parents were of the same species, while sterile off- 

 spring constituted conclusive evidence that they were of different 

 species. This view was held, as Herbert says : 



"without suggesting any alteration in the definition of the term 

 'species,' but leaving it to imply what it had before universally signified 

 in the language of botanists." 



Again he says : 



"Having, in fact, the same fundamental opinion, that the production 

 of a fertile intermixture designated the common origin of the parents, I 

 held also, what experience has in a great measure confirmed, that the 

 production of any intermixture amongst vegetables, whether fertile or 

 not, gave reason to suspect that the parents were descended from one 

 common stock, and showed that they were referable to one genus ; but 

 that there was no substantial and natural difference between what bota- 

 nists had called species, and what they had termed varieties, the distinc- 

 tion being merely in degree, and not absolute ; so that, without first re- 

 forming the terms used in botany, and ascertaining more precisely what 

 was meant by a species, those who argued on the subject were fighting 

 the air." (2c, p. 337.) 



Herbert's entire freedom from any slavish adhesion to the 

 species idea with respect to hybrids is plainly stated. 



"Further experiments have shown," he says, "that the sterility or fer- 

 tility of the offspring does not depend upon original diversity of stock; 

 and that, if two species are to be united in a scientific arrangement on 

 account of a fertile issue, the botanist must give up his specific distinc- 

 tions generally, and entrench himself within the general." (2c, p. 337.) 



"In fact there is no real or natural line of difference between species 

 and permanent or descendible variety, as the terms have been applied 

 by all botanists ; nor do there exist any features on which reliance can 

 be placed to pronounce whether two plants are distinguishable as species 

 or varieties. Any person, who attends to the subject, will perceive that 

 no botanist has laid down any precise rules by which that point of in- 

 quiry can be solved, and that the most variable, contradictory and un- 

 substantial features have been taken by different persons, and by the 

 same person on different occasions, to uphold the distinctions they pro- 

 posed to establish ; the truth being that such distinctions are quite arbi- 

 trary, and that, if two plants are found capable of inter-breeding, when 

 approached by the hand of man, they are as much one as if they were 

 made to intermix more readily and frequently by the mere agency of the 

 wind, or assiduity of insects, and are nT)t separable with more truth by 

 any positive difference, than the varieties which cannot be prevented 

 from crossing with each other when in the same vicinity." (2g, p. 341.) 



It was the view of Herbert that fertility in hybrids depended 

 much upon circumstances of climate, soil and situation. He finally 

 concludes that experiments had made it almost certain 



"that the fertility of the hybrid or mixed offspring depends more upon 



