538 WHITE— STUDIES OF INHERITANCE IN PISUM. 



Round smooth, colored flowers = AALI2RR, 

 Round smooth, white flowers = aaLoLoRR, 

 Indent, colored flowers = AAL0L2RR, 



Wrinkled, white flowers = aaLoL^rr. 



Excepting the two exceptional cases mentioned under crossing 

 results, all the data are in conformity with the interpretation and 

 the formulas given, and the various results given from crossing 

 may all be obtained through combinations of these four genetic 

 types of varieties. The two exceptional cases need further con- 

 firmation, as one at least is doubtful as to fact. 



Satisfaction is the only wrinkled pea with the aaL^L^rr formula 

 so far studied, while the other varieties are numerously represented 

 in the studies of Bateson, and Tschermak. Tschermak (86) gives 

 the formulas for seven smooth round or indent with colored flowers 

 and five smooth round, white flowered varieties with which he ex- 

 perimented. In his formulas, A and L^ are separate factors, but 

 since they appear always to be associated it is simpler to regard 

 them as one. 



4. Seed Shape. 



Though only slightly studied, except as regards the two or more 

 factors controling cotyledon shape (round smooth, angular wrinkled, 

 indent), seed shape is known to be determined in part by still other 

 sets of factors, which are not associated with those of cotyledon 

 form and indent. Hurst (42) suggests that angularity, square- 

 ness, flattened sides (flat peas) and deep dents on the sides (not 

 indent) are directly determined by the pressure of the peas of a pod 

 against one another and by the constriction of the pod itself. Gen- 

 erally speaking, he thinks the roundest peas have plenty of room in 

 the pod, while the most wrinkled angular peas are tightly packed 

 together. Irregularity in shape may be caused by a struggle for 

 growth room among the peas of the same pod, and thus alter their 

 hereditary tendency to roundness. Lock (54) in the F. of certain 

 crosses between varieties with narrow pods and round seeds and 

 varieties with wide pods and flat seeds, found as a rule that flattened 

 seeds were associated with wide pods and cubical or spherical seeds 

 with narrow pods. In exceptional cases, wide pods had round or 



