WHITE— STUDIES OF INHERITANCE IN PISUM. 539 



cubical seeds and when an Fg from them was grown, both wide and 

 narrow pods were obtained, thus showing them to be heterozygous 

 for pod width. 



Observations of my own on over two hundred varieties, and 

 crosses between several of them, in general, confirm Lock's ob- 

 servation as to the association of round or cubical peas with 

 narrow pods and flat (whether angular wrinkled, or roundish angu- 

 lar and smooth)' with wide pods. The diameter of the pod, how- 

 ever, is not necessarily to be regarded as a character which modifies 

 the expression of the factors for seed shape, since it can well be 

 that some of the factors which determine seed shape are coupled or 

 partially coupled with those determining pod diameter. In the 

 former case the seed and pod characters under discussion would be 

 regarded simply as different expressions of the same factor. 

 Wrinkled peas are practically always flat or cubical, but smooth 

 peas may be cubical with rounded edges (drvmi-shaped), bean 

 shaped, flat and rectangular with rounded corners, conical (if end 

 pea in the pod) and spherical. Bean-shaped peas are characteristic 

 of one variety (Bohnenerbse of Haage & Schmidt), but occasion- 

 ally a single typical bean-shaped seed appears among a crop of 

 round seeds. When planted, only round seeds are produced, so 

 the variation, in the latter case, is largely due to special environ- 

 mental conditions of some sort. 



5. Seed Dimension and Weight. 

 These two characters are mutually dependent upon each other. 

 Greater size generally means increased weight, though not neces- 

 sarily so, especially when the composition of the seed, either chem- 

 ical or morphological, is altered. Both round and wrinkled pea 

 varieties have large and small seeds. The smallest seeds are found 

 in some of the western Chinese varieties introduced into the United 

 States by our Department of Agriculture, though several of the wild 

 species have seeds of about the same size. The so-called wild P. 

 arvense types of Europe and several forms of P. elat'ms have com- 

 paratively large seeds. Some of the largest seeded pea varieties are 

 French Giant Gray Sugar, Champion of England, White-eyed Mar- 

 rowfat, and Black-eyed Marrowfat. As compared with the latter, 



