i86 PLANT HYBRIDIZATION BEFORE MENDEL 



Nageli comments truly on the meagre range of information 

 which many investigators possessed, proceeding either from obser- 

 vations of supposed hybrids in nature, or from conclusions derived 

 from their own scanty experiments, which : 



". . . on account of their incompleteness, and frequently on account of 

 their inexactness, were unavailable for new theory." (4c, p. 190.) 



He then pertinently remarks : 



"The knowledge of hybridization would in recent times have made 

 more progress, if many observers, instead of beginning anew, had made 

 use of the results of the first-two-named German investigators fKolreuter 

 and Gartner], who applied the labor of their lives to the solution of this 

 problem." (4c, p. 190.) 



Here Nageli strikes at a weak point not only in the science of 

 his own day, but of a later time. Resting upon the experiments 

 of Mendel, investigators have too frequently overlooked the sug- 

 gestions to be found in the work of the pre-Mendelian students of 

 hybridization. Concerning the then existing state of the knowledge 

 of crossing, he says : 



"No field of knowledge is less complete ; and continued, critically con- 

 ducted experiments are in the highest degree desirable, but they can 

 have scientific value only when they rest upon the knowledge ot what 

 has already occurred ; when they either verify the already determined 

 laws through new facts, or modify, extend or limit them ; in the latter 

 case, however, showing the conditions under which these modifications 

 appear." (4c, p. 190.) 



Nageli indulges in a gleam of wit at the expense of those who 

 felt no quarrel over the species question so far as hybridization 

 was concerned, but who relied upon the rule, that at least only 

 species of the same "genus" could hybridize, and that therefore 

 those species which possessed the capacity to cross must be united 

 in the same "genus." He remarks : 



"if I say that all wines belong to the genus 'liquid' it does not follow 

 therefrom that every liquid has to be a kind of wine, and that everything 

 that is not a wine must on this account also be no liquid." (4c, p. 192.) 



In order to assist in obtaining a picture of the status of hybrid 

 theory at the time of the publication of Mendel's paper, it will 

 not be without interest to note the substance of the series of nine 

 conclusions given by Nageli in his paper "Die Bastardbildung 

 im Pflanzenreiche" (4c), presented before the Akademie der Wis- 

 senschaften at Munich, December 15, 1865. It will be noted that 

 most of these so-called "rules" bear generally upon what plants 



