Band XVI Heft 3M Oktober 1916 



Sorting and blending of "unit characters" 



in the zygote of Oenothera with twin and 



triplet hybrids in the first generation). 



By Geo. F. Atkinson. 



Department of Botany, College of Arts and Sciences 

 Cornell University, Ithaca, N. Y. 



Source and characters of the parent species. 



(Eingegangen am 1. Dezember 1914.) 



During the summer of 1909 I became interested in a few of the 

 variations presented by the common evening primrose^) in the vicinity 

 of Ithaca, N. Y. Several individuals, wliich I passed almost daily, forced 

 themselves upon my attention because the mid veins of the leaves and 

 the stems of some individuals were red, while other individuals had 

 white veins and green stems. Since I had never made a critical study 

 of the genus Oenothera, these color characters were the only differen- 

 tial features of wliich I was conscious at that time. Cross pollinations 

 were made between two individuals during that season, and seeds were 

 saved in the autumn. Since I was in Europe the follo^\dng summer 

 (1910), the seeds were not planted until the spring of 1911. They 

 were sown in seed pans, and when the seedlings were a few weeks 

 old they were transplanted to flats, and later (during June) were trans- 

 planted to the garden. 



During the seedling stages, in the seed pans and also in the flats, 

 there were no perceptible differences which could not be ascribed to 



^) Paper read before the American Philosophical Society at the annual general 

 meeting at Philadelphia, Pa., April 23—25., 1914. 



*) These species are a part of the great complex of forms sometimes spoken of 

 as the "biennis alliance", in which there are probably 100 or more different species 

 f\j in North America. 



05 

 UJ 



Induktive Abstammungs- und Vererbungslehre. XVI. 2^3 



