WHITE— STUDIES OF INHERITANCE IN PISUM. 533 



Darbishire (19) regards the shape and constitution of the starch 

 grain, the water absorptive capacity of the seed and the shape of 

 seed (round, smooth or wrinkled) as four separately inherited 

 characters. This deduction is based on a series of observations on 

 crosses of round and wrinkled varieties which demonstrated the F^ 

 nature of the starch grains, as regards shape and constitution, and 

 the water absorptive capacity of the seeds to be intermediate be- 

 tween the two parents used. Although round smooth, the F^ seeds 

 had about equal proportions of simple and compound starch grains- — 

 and the latter instead of having on the average 6 particles per single 

 grain as in the wrinkled parent averaged only 3 particles. Five 

 seeds each of 48 F^ plants were used instead of F„ seeds for deter- 

 mining segregation phenomena. Sixteen plants were pure round- 

 seeded segregates and had starch grains of the ancestral round 

 parent type. Twenty plants were heterozygotes and had pure round, 

 heterozygote round and wrinkled seeds. Only the round seeds were 

 examined. Out of each of the 20 lots of 5 seeds, at least one had 

 starch grains similar to the F^ and in several cases all were similar 

 to the F^ seeds as regards shape and degree of compoundness. 

 The homozygote rounds were easily distinguished from the other 

 rounds. The heterozygote round seeds, while either roundish or 

 irregular in shape, varied greatly in the proportion of compound to 

 simple grains they possessed. In 2 cases, where countings were 

 made, one gave 203 compound and 305 simple, while the other had 

 only 28 compound out of 304 counted. The degree of compound- 

 ness of the starch grains varied in different seeds, some being many 

 particled and some seeds with only few-particled grains. No prog- 

 eny test of the correctness of the determination of homozygous and 

 heterozygous rounds by observation of their starch was made, but 

 the results were checked up by the approximation to the ratio of 2 

 heterozygote : i homozygote seed. The 12 plants with wrinkled 

 seeds had the wrinkled ancestor type of starch grain, except in two 

 or three seeds out of 45 examined, in which a few simple grains 

 were observed. 



As regards water absorptive capacity, F2 peas with round com- 

 pound starch grains and F^ peas with long simple grains both had the 

 same absorptive capacity as the F^ pea with both kinds of starch 



