60 



DE. E. E. GATES— CONTEIBIJTION TO A 



as well as structural characters. Particular races of Oe^iothera grown under different 

 conditions of culture may be so unlike as scarcely to be recognizable, or indeed they 

 may be wholly unrecognizable if the conditions of their cultivation are very diverse. 

 These facts serve to emphasize the point of view that heredity and variation represent 

 the two sides of a single process, namely the interaction of the organism with its 



f 



environment in every stage of ontogeny. 



Several races of 0. LamarcMana from various sources show constant differences 

 from the form of DeVries's cultures, though some of them at least produce mutants 

 analogous to those of DeYries. The differences between these O. JLcmiarchkma 

 races are largely in the foliage, and they appear to be chiefly of a quantitative sort. 

 The race of PeYries itself shows a considerable range of fluctuation, particularly in 

 the crinkling of the leaves and the method of branching. O. LamarcMana is thus a 

 polymorphic species, containing several elementary species. 



It is shown that in O. LamarcMana and nearly all the mutants, tbree distinct leaf-types 

 succeed each other in the ontogeny of the rosettes. This necessitates great care in 

 comparing only corresponding stages of the various forms, a precaution which is 

 especially urgent in comparing liybrids with their parent types. The mutant O. gigas 

 usually does not show this succession of leaf- types, the young rosettes merely showing a 

 succession of leaves of the same type but of increasing size. One race, however, 

 received from the Botanic Garden at Palermo under the name 0. cognata, whose adult 

 rosette was identical with O. gigas, in my cultures of 1911 passed through stages 

 apparently analogous to those of the other mutants. 



One remarkable feature of the Oenothera mutants is the way in which the differing 

 characters of leaf, stem, and flower remain together and refuse to be separated and 

 redistributed by crossing as in Mendclian hybrids. The differences are not in single 

 characters but affect every part of the plant, most of the former showing recognizable 



peculiarities from a very early stage right through their ontogeny. Put many of the 



4J 



forms are more easily recognizable in certain stages than in others. Thus O. hrecistylis 

 shows marked peculiarities in the young seedlings, the mature rosettes are difficult to 

 distinguish from 0. LamarcMana, but the adult plants are easily recognized by their 

 bracts, sepals, and styles. 



r 



O. groMcliJlora, like the O. Lamai^chiana forms, passes through several distinct 

 stages in its rosette ontogeny, but under ordinary conditions of culture usually omits 

 entirely the very characteristic adult stage of its rosette, and not infrequently the 

 rosette stage is omitted altogether under the same conditions of culture in which it is 

 produced in the 0. LamarcMana forms. 



A large number of geographic races of 0. biennis from Korth America have been grown. 

 They differ chiefly in leaf -characters, but their behaviour in crossing is not yet known. 



My cultures of O. muncata from many sources show that, especially in Canadian 

 forms, a dimorphism exists which is comparable with the twin hybrids first observed by 

 DeVrics in crosses between O. hiennis and O. LamarcMana. These twin forms are 

 respectively broad- and narrow-leaved, and they were observed in cultures from wild 

 seeds collected in Nova Scotia, New Brunswick, and Manitoba. This indicates that the 



