PLANT HYBRIDIZATION BEFORE MENDEL 197 



of hybrids — a rather clear, complete,, and searching review of the 

 fundamental matters in respect to hybridization, as they were 

 realized and generally understood at that time. 



In view of the considerable attention at one time aroused by 

 Nageli's theory of the idioplasm, and the fact that it is interesting 

 historically as a presentation of a theory thought to be possibly 

 operative in the case of amphimixis, it seems desirable to intro- 

 duce at this point a presentation of Nageli's contribution to the 

 theory of the factors in development (Mechanisch-physiologische 

 Theorie der /\bstammungslehre). (41, pp. 822, 1884.) It is hoped 

 that the historical value of the contribution, theoretically speak- 

 ing, as being one of the last of the unitary theories of descent 

 propounded before the discovery of Mendel's investigations, will 

 make amends for the quantity of the material necessarily intro- 

 duced. 



Nageli considers that the substance containing the "Anlagen" 

 (the "Plasmasubstanz") consists of different modifications of 

 albumins, the molecules of which are united in molecular groups 

 of crystalline form, which he calls "micellae," soluble and in- 

 soluble forms commingled, forming a half-fluid, slime-like mass. 

 This organization he designates as the "stereoplasm," of which 

 he considers that only the smaller portion represents the actual 

 "Anlagen" or factors. 



From what Nageli calls the "Anlage-plasm^" i.e., the gene- 

 protoplasm, there is a definite movement of a developmental 

 character, leading to a cell-complex of greater or less size, such 

 as a certain leaf, root, etc. This protoplasmic series Nageli desig- 

 nates briefly as the "idioplasm," as distinguished from the re- 

 maining "stereoplasm." (^i, p. 23.) Crossing, or rather amphi- 

 mixis, is considered to be the cause of bringing the factors of 

 lesser S'trength into development. Crossing especially is supposed 

 to be one of the causes for the development of the "Anlagen" 

 (factor-rudiments) of lesser potency, that is to say, those still in 

 process either of origination, or of disappearance. Latent Anlagen^ 

 come more easily into development through amphimixis than 

 through sexual modes of propagation, (ib., p. 24.) Differences in 



1 The German word "Anlagen" being practically untranslatable will 

 be used henceforth without further comment, for "rudiments of factors," 

 etc. 



