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THE AMERICAN NATURALIST [Vol. XLIX 



it becomes more or less a superfluity to study any partic- 

 ular species of Oenothera from the genetical and morpho- 

 logical standpoint, since it is the genus as a whole which 

 manifests the peculiar features, which have brought it so 

 much into the foreground of biological controversy during 

 the past decade. This is on the whole a satisfactory situa- 

 tion as it enables us to cut the perplexing gordian knot 

 involving the controverted origin of 0. lamarckiana. 

 The mutation hypothesis of De Vries accordingly turns 

 not upon the finding of new herbarium specimens which 

 may throw light upon the origin of a particular species 

 but upon the much larger question of the genetical status 

 of the genus CEnothera as a whole. This question can be 

 settled only by consideration of the Onagraceas as a whole 

 and of other families of the Angiosperms, which present 

 similar reproductive peculiarities. 



Before proceeding however to the discussion of the 

 facts recorded above in their relation to the mutation 

 hypothesis of De Vries, based on the conduct of 0. lamarck- 

 iana in cultures, it will be necessary to make some brief 

 reference to other studies carried on in the laboratories of 

 plant morphology of Harvard University, which will be 

 published elsewhere, either at the present time or at a 

 later period. Obviously of great importance in the pres- 

 ent connection is a comparison of the conditions of spo- 

 rogeny found among the lower plants, the Bryophyta, the 

 Pteridophyta and Gymnosperms, which are not character- 

 ized by enormous multiplication of species, with the 

 sporogenic features of the Angiosperms in which the 

 multiplication of species has run riot. Further compari- 

 son of liverworts, belonging to the Marchantiales, Antho- 

 sperms, manifesting similar sporogenic and specific pecu- 

 liarities, is both pertinent and necessary, in the present 

 connection. 



It will be convenient to deal first summarily with the 

 sporogenic conditions found in the lower forms of the 

 Embryophyta from the Bryophyta to the Gymnosperms. 

 In the present connection a considerable number of spe- 



