WHITE— STUDIES OF INHERITANCE IN PISUM. 567 



certain of her crosses is due to heterozygosis in' the sense of East 

 and Hayes (27). 



16. Pod Color. 



As regards color of unripe pods, varieties of peas may be classi- 

 fied into three groups — green-podded, yellow-podded and purple- 

 podded. 



Green-podded varieties are the most common and are typical of 

 all the wild species. Green pods are never associated with yellow 

 foliage. 



Yellozv-podded varieties often have bright yellow pods associa- 

 ted with yellow flower-bearing axes, green stems and fohage. All 

 yellow-foliaged varieties, such as Goldkonig and Gold von Blocks- 

 berg, have yellow or yellowish green pods. All yellow-podded 

 varieties known to me have yellow cotyledons, although segregates 

 have been obtained with yellow pods, yellow foliage and green 

 cotyledons. 



Purple-podded varieties such as Nero and Purple-podded Field 

 Pea have colored flowers and gray seed coats. Tschermak (86) 

 cites Vilmorin as saying that weak purple pigmentation has been 

 found in pods on white-flowered plants. Lock (56), Tschermak 

 (86) and Fruwirth (34) have found considerable variation among 

 different pods of the same plant, some pods being wholly purple, 

 while others are purple splashed with green in various degrees. 

 Plants with all purple pods are also found. Fruwirth attempted to 

 secure by selection a stable pure green-podded race from the green 

 and purple-splashed podded plants. Ten generations gave entirely 

 negative results. Strains having only purple pods were secured in 

 these same experiments by planting seeds of wholly purple pods. 

 Fruwirth regards the appearance of these true breeding purple- 

 podded strains as bud mutations. 



Results from Crossing. 



Green pod X green pod always gives green pod (pure varieties). 



Green pod X yellow pod gives in F^ all green-podded progeny. 

 In Fo Mendel secured approximately 3 green-podded plants : i yel- 

 low-podded. Tschermak's results involving crosses of yellow pod 



