PLANT HYBRIDIZATION BEFORE MENDEL 183 



Regarding the possibility of securing a cross in any given 



case, Wichura remarks (p. 84) : 



". . . Only such species can be united in a' hybrid, which agree in rela- 

 tively many characters, and correspondingly in many life conditions. 

 Experience teaches the same thing in the familiar rule, that hybrid 

 combinations only occur between species of the same genus, or different, 

 yet nearly related, genera." 



He comes to a generalization of genetic value in the following 



statement (p. 85) : 



"It is known that families die out after a few generations whose mem- 

 bers carry in themselves the germ of a disease, and who mate only among 

 themselves; and variety breeders know very well that all diverging char- 

 acters of animal and plant species may be intensified when, in successive 

 fertilization, the precaution is taken that only similarly divergent in- 

 dividuals mate with one another." 



25. Kegel on Hybridization. 



The views of Regel (5) on hybridization, also illustrate in an 

 interesting manner the general attitude of the hybridists of the 

 time on the subject of the products of crossing: 



"The hybrid plant always originates through sexual intermingling of 

 two parent species, actually different from each other. Plant forms which 

 have originated through mutual fertilization of different varieties of 

 one and the same species are not real hybrids, but are frequently falsely 

 regarded as such." (5, p. 59.) 



Regel designates the former as "true," and the latter as "false" 

 hybrids. 



This point of view has, of course, long since been completely 

 superseded by the point of view expressed by the term "the hybrid 

 condition," with respect to such and such characters possessed by 

 the plant. Regel carried on experiments in 1846, in the crossing 

 of Calceolarias, in which he found that, in respect of the essential 

 characters, the hybrids occupied an intermediate position between 

 the two parents. 



26. Carl Wilhelm von Ndgeli and the Hybrid Question. 



In 1865 Carl von Nageli (4c) presented a survey of the work 

 of the earlier hybridizers. The occasion for the discussion, he says, 



". . . presented itself to me from an investigation of the signification 

 of the intermediate forms occurring in nature between many species." 

 (4c, p. 187.) 



The theme of hybridization, he says, is of importance because 

 ". . . it sheds light upon reproduction, in so far as it is the question 



