No. 597] 



IX II Eli It AX CE STUDIES IN PISUM 533 



yellow, yellow, light yellow, dark green, green, light green, 

 and yellowish green, when these varieties are all grown 

 under approximately the same conditions. Any one can 

 distinguish between dark' ureen and dark yellow, but one 

 well acquainted with the color of cotyledons in Pi.su in 

 would have difficulties in distinguishing between light yel- 

 lowish greens and light yellows. The classification made 

 is admittedly arbitrary, though based on the same sort of 

 acquaintanceship with these colors as that of a nursery- 

 man with varietal differences in bulbs or varietal charac- 

 ters in leafless nursery trees. The point which it is de- 

 sired to emphasize by the foregoing remarks is that these 

 shades of cotyledon color are distinctly varietal charac- 

 ters, and are always characteristic of the respective vari- 

 eties when these varieties are all grown together under 

 any one of the several specific 3 environments in which the 

 pea cultures at the Brooklyn Botanic Garden have been 

 grown. 



The Kelation of Environment to Cotyledon Color 

 One other perplexing factor enters into the study of 

 cotyledon color in Pisam — the difficulty of being certain 

 that all varieties under observation mature their seed 

 under as nearly as possible identical environments, a 

 factor that many geneticists experimenting with other 

 plant forms are prone to neglect. Some varieties of peas 



2 S.P.I, stands for Office of Foreign Seed and Plant Introduction, U. S. 



