334 PLANT HYBRIDIZATION BEFORE MENDEL 



in thousands of specimens, one can almost always observe that hardly 

 any two are alike. Some revert to the form of the pollen-parent, others 

 to that of the pistil-parent, a third group occupies a central position. 

 Between these are placed the others, in the most motley variety of 

 staminate and pistillate characteristics and in almost every graduation of 

 mutual intermixture." (ed. 1910, p. 27; ed. 1889, p. 25.) 



"Many and prominent authors have pointed out the significance of 

 hybrids for establishing the nature of fertilization. With the same right, 

 we may use them in trying to penetrate into the mystery of specific char- 

 acter. And then they clearly prove to us that this character is fundamen- 

 tally not an indivisible entity. The characteristics of a hybrid {of the 

 first generation) are as sharply defined and as constant, and on the whole 

 of the same order, as those of the pure species, and the frequent specific 

 name, 'hybridus,' might go to prove that even the best systematists felt 

 this agreement." (ed. 1910, p. 28; ed. 1889, p. 26.) 



De Vries remarks, with considerable acumen, that the combina- 

 tion in a hybrid, of two, three, or more species, is not in itself a 

 matter of importance. The species entity concept was discarded 

 by him for the unit-character concept, already as early as 1889. 

 There is no reason other than a purely practical one, why any 

 limit need be put to the number of species entering into the hy- 

 brid composition ; why, 



". . . in fact, there should not be combined in one hybrid character- 

 istics which have been taken from an unlimited series of allied species. 

 But this is of small importance, the chief point being the proposition that 

 the character of a pure species, like that of hybrids is of a compound 

 nature." (ed. 1910, pp. 27-8; ed. 1889, pp. 24-6.) 



Further on he says : 



"The process of fertilization, In Its essence, does not consist therefore 

 in the union of two sexes, but In the mixing of the hereditary characters 

 of two individuals of different origin, or at least such as have been sub- 

 jected to different external conditions." (ed. 1910, p. 31 ; ed. 1889, p. 29.) 



Further comment on the subject of the existence of hereditary 



characters as factorial units or unit factors Is as follows: 



"Let us regard the individual hereditary factors as independent units, 

 which can be combined with each other in different proportions into the 

 individual character of a plant." (ed. 1910, p. 31 ; ed. 1889, p. 29.) 



"In the preceding paragraphs we have seen how the single hereditary 

 characters occur as independent units in the experiments of hybridization 

 and crossing, and how they can be attained in almost every degree. In 

 the same way evidently, we miist think of those units as independent in 

 the ordinary process of fertilization as well." (ed. 1910, p. 33; ed. 1889, 



p. 31-) 



"Seemingly elementary, the specific character Is actually an exceed- 

 ingly complex whole. It is built up of numerous individual factors, the 

 hereditary characters. The more highly differentiated the species, the 

 higher is the number of the component units. By far the most of these 



