526 



WHITE— STUDIES OF INHERITANCE IN PISUM. 



shire and others are simple, oval or potato-shaped and of large size 

 with well-marked hilum centers and distinct lines of stratification. 

 Darbishire (19), and Kappert (48) found small round grains asso- 

 ciated with the larger oval ones, and occasionally these are divided 

 by a single split or fissure which cannot be increased in size through 

 the action of diastase and ptyalin (48). Kappert (48) also has 

 observed these longitudinal fissures with short side splits occasionally 

 among the large oval grains. The size of the starch grains vary 

 considerably in different cell layers of the same seed, the smallest 

 being found in the outer layers, where the protoplasm is most dense. 

 Measurements of starch grains, given in the following table, show a 

 considerable variation, though the data are too scant to be of much 

 weight. 



Darbishire divides the length by the breadth X 100 and secures 

 the breadth-length index (in Eclipse 66.14) or the breadth in terms 

 of per cent, of length. The breadth-length index for Laxton's 

 Vorbote is 67.8-69.1 and for Emerald Gem starch grains 74.3 (48), 

 indicating that starch grains of some smooth-seeded varieties are 

 less oval than others. The long oval starch grains are characteristic 

 of the early as well as of the late stages of seed development. 



According to Denaifife (23), Halsted, Darbishire (19), Kappert 

 (48) and others, round smooth peas take up less water upon ger- 

 mination than wrinkled peas. Darbishire found the average absorp- 

 tive capacity (or the amount of water an immersed dry pea would 

 take up in twenty-four hours, expressed as percentage of weight of 

 the dry pea) of 12 Eclipse peas to be 86 per cent. Kappert found as 

 regards absorptive capacity so much variation in the seeds even 

 of the same sort on the same plants that he regards the methods 

 used by Denaiffe and Darbishire as extremely inexact. Kappert 

 gives the water loss of air dry seeds of smooth-seeded peas in 



