540 WHITE— STUDIES OF INHERITANCE IN PISUM. 



the wild P. clatiiis seeds are intermediate in size between them and 

 the small Chinese peas and such wild peas as P. humile and P. 

 quadratum. Size and weight of pea is to some extent associated 

 with size of plant and pods, though small dwarf plants such as Lax- 

 tonian bear relatively large pods and seeds. Delicate-stemmed plants 

 such as Benton, P. quadratum, P. humile, Abysinnian Black, P. 

 Jomardl, Velocity, Express and many of the Hindu and Chinese 

 varieties do not bear large seeds or large pods. Pods and seeds of 

 small, intermediate or of large size may be associated with tall or 

 large, robust-stemmed plants. 



In crosses, Bateson (i) finds that small and large seeds gen- 

 erally give intermediates in F^ and Fo, although he has seen one 

 cross suggesting segregation. Macoun (57.5) crossed two peas of 

 about equal size (Black-eyed Marrowfat and White-flowered 

 Mummy) and in Fo secured the parental types and intermediates as 

 well as seeds very much smaller than any of the common culti- 

 vated varieties. The latter bred comparatively true in F3. Vil- 

 morin (90) states large size of seed to be dominant to small size. 

 Tschermak (81, 86) has gone into the subject with customary Teu- 

 tonic thoroughness, but has published his results only in part. In 

 general, he finds the F^ generation of large X small seed to have 

 seeds of intermediate weight, though nearer in weight to the small- 

 seeded parent. In Fo, a continuous series between the two parents 

 was obtained, with a great scarcity of the two grandparental types. 

 Repeated experiments with large numbers always gave the same 

 results, though in a few cases seeds still smaller than those of the 

 small-seeded grandparent appeared. In Fo, at least one of the Fo 

 intermediates remained constant. 



In back-crosses of the F^ with the small parent, the F^ seeds were 

 small to possibly still smaller than the small parent, while the same 

 Fj back-crossed with the large-seeded parent gave intermediates, 

 occasionally some seeds of which were larger than the F^ of (large 

 X small) itself. 



As an illustration of his actual results, large P. sat. (ave. wght. 

 0.3305 gm.)X small P. arv. (ave. wght. 0.08649) i^i F^ gave inter- 

 mediates, ave. wght. 0.1648 gm., which in Fo gave a continuous series 

 which Tschermak classified in 4 groups — those with seeds averaging 



