WHITE— STUDIES OF INHERITANCE IN PISUM. 519 



light on seed coat color and pattern inheritance through making all 

 sorts of crosses, back-crosses, reciprocal crosses and so on, his num- 

 bers in most cases have been lamentably small, consequently the 

 approximation to the expected ratios on which the factor represen- 

 tations are based has not been close, and such ratios as 2 : i where 

 3 : 1 were expected are comparatively common. 



The above interpretations account for practically all the experi- 

 mental data on seed coat color in Pisitui. There are no data, so 

 far as I am aware, opposed to these interpretations, barring the 

 smallness of the numbers by which the poor approximation to ex- 

 pected ratios is explained. 



2. Cotyledon Color. 



Varieties and species of Pisum as regards the cotyledon color of 

 the ripe seed may be divided roughly into two classes — those with 

 green cotyledons and those with yellow cotyledons. Between the 

 extremes of these two classes, there are all gradations of cotyledon 

 color from the darkest green through light green, yellowish green, 

 green piebald with yellow spots, light yellow, bright yellow and dark 

 orange yellow. Each of these classes is characteristic of a certain 

 group of varieties, each variety possessing and breeding true to one 

 of the above colors and to no other. Environment may alter the 

 color generally characteristic of a variety so as to place it in another 

 class. Some varieties are altered by common environmental changes 

 much more than are others. Mendel (60), Hurst (42), Lock (55), 

 Bateson (i), Darbishire (21), Tschermak (80, 81) and White (98) 

 have all discussed this color variation in cotyledons both in relation 

 to environment and to heredity. 



Green Cotyledon. — Green cotyledon color varies from dark green 

 in such varieties as Wisconsin Blue and Alaska to light green or 

 yellowish green as is characteristic of Telephone, Blue Prussian and 

 Duke of Albany. As first noted by Hurst (42) green wrinkled peas 

 are always a shade lighter and tend to be more yellowish than the 

 green smooth-seeded varieties. \'arieties such as Scotch Beauty and 

 other smooth-seeded dark greens do not fade to yellow upon ex- 

 posure to moisture and light as easily as the wrinkled varieties or 

 such smooth varieties as Express. Dark greens give the best results 



