PLANT HYBRIDIZATION BEFORE MENDEL 137 



among which he enumerates prolonged cultivation, removal from 

 one set of climatic and soil conditions to another, and hybridiza- 

 tion. 



The thought of the time did not clearly distinguish a differ- 

 ence between the nature of the changes brought about by the 

 external environment, and those arising from sexual fertiliza- 

 tion. Both were generally assumed to be equally heritable. Culti- 

 vation long continued was considered to have been especially 

 potent in bringing about variation. In Verlot's words : 



"it is especially with plants cultivated for a great number of years, 

 with those the introduction of which is so ancient that it is lost in the 

 night of time, that one finds profound and multiplied modifications." 

 (6, p. 4.) 



He further voices the then prevailing view regarding the rela- 

 tion between culture and variations : 



"if we compare," he says, "a species in its spontaneous condition with 

 the same species cultivated, transported, that is to say, most often into 

 conditions of climate, soil, etc., completely different from those in which 

 it lived before, we shall be struck by seeing that, in our gardens, this 

 latter will show derivations of type more numerous than in the wild 

 state. We shall infer from this fact the consequence that the faculty of 

 varying, which is proper to the plant, augments with culture, if we 

 observe then that the plants cultivated in our gardens which have varied 

 the most, as for example the dahlias, the roses, the camellias, the rhodo- 

 dendrons, the potato, etc., are not borrowed for the most part from our 

 flora, nor from one of the neighboring floras, but on the contrary come 

 from distant countries, where they grow under conditions often abso- 

 lutely different from those in which we cultivate them, we shall con- 

 clude that, the more a species is depatriated, the more easily it will 

 vary." (6, p. 30.) And again, "the more plants are cultivated, the greater 

 their variations are and, by the same token, the easier they are to fix. 

 We will possibly be contradicted, but we do not hesitate to consider, 

 once more, long practised culture as one of the most favorable antece- 

 dents to the rapid fixation of variations," (6, p. 38.) 



It now seems probable that the increased variation manifested 

 by wild plants, when brought into cultivation, is due to the re- 

 moval of the restrictive influences of competition, rather than 

 to any actual increase in the range of heritable variability itself. 



Verlot cites, as examples of the changes supposedly wrought 

 by culture, the changes brought about in the roots of such plants 

 as beet and parsnip ; in the production of dwarf plants ; in vari- 

 ous modifications of general habit, such as fastigiate, pyramidal 

 and weeping variations in trees ; in the appearance of variations 

 with laciniate or otherwise modified leaves ; in the varieties with 



