574 WHITE— STUDIES OF INHERITANCE IN PISUM. 



non-parchmented pods makes a decided difference in the number of 

 chenille plants that are obtained in crosses. Seeds of purple red 

 flower segregates are said to rarely cohere, even though the plants 

 are sblw (abc). 



It seems to the writer, however, that these results are more 

 plausibly and simply interpreted as partial coupling or linkage of the 

 factor S with either Bl or W, it being impossible to tell which until 

 further data are obtained. The amount of crossing over is shown 

 by the following grouping of the Fo progeny and that of certain 

 heterozygote families in F3 : 



The percentage of plants with emerald foliage is much lower 

 than that expected on a 3 : i ratio, and as chenille seeds and emerald 

 foliage are coupled, this also brings down the per cent, of chenilles 

 below the theoretical expectancy. Emeralds in the writer's experi- 

 ence as grown from seed kindly sent by P. Vilmorin, succumb much 

 more easily to disease than the general run of glaucous varieties and 

 perhaps this accounts for the low per cent, of emeralds obtained in 

 Vilmorin's hybrid generations. The relation of flower color to 

 free and chenille seeds is not clear on the present scant data, though 

 the evidence does not favor the idea of partial coupling between one 

 of the color factors and chenille, so far as the writer can dis- 

 cover. The approximation between the obtained frequencies 

 (152 RpF:48 RpA:5i WF:6 WA) and those theoretically ex- 

 pected (144:48:48:16) indicate either independent inheritance or 

 at most very loose coupling. 



20. Pod Diameter. 



Both pod diameter and pod length in peas present the same com- 

 plex mixture of environmental and genetic variations as is found in 

 such characters as time of bloom, productivity and height. Several 

 of the wild varieties have the smallest and most narrow pods 

 (0.8-0.9 cm.) while the sugar peas have the longest and widest 



