WHITE— STUDIES OF INHERITANCE IN PISUM. 



563 



the small classes. This is called the reduplication hypothesis. Mor- 

 gan and his students (61,62,73) explain the same facts in a wholly 

 different manner on the basis of the linear arrangement and " linkage " 

 of groups of factors together in the same chromosome, and the occa- 

 sional crossing-over of factors to the opposite or homologous 

 chromosome during the maturation divisions. To the writer, the 

 latter appears to be the more simple interpretation and better sup- 

 ported by the facts. 



14. Bloom. 



With comparatively few exceptions, all varieties of peas have 

 a waxy surface covering on their leaves, stems, pods and other plant 

 parts. The varieties from which this is absent are known as 

 Emeralds and very easily become diseased. Emerald varieties 

 studied by Vilmorin (89) are Emereva, Johnson's British Empire 

 and Pois a brochettes. 



Results from Crossing. 



Glaucous (zvaxy) X glaucous gives glaucous. 

 Glaucous yc emerald in F^ is always glaucous (89, 86, 92). 

 Fo, the following results have been obtained : 



In 



In F3, of 15 Fo glaucous, 5 gave all glaucous, while 10 gave 133 

 glaucous : 32 emeralds. 15 Fo emeralds tested in F3 gave all or 199 

 emeralds. 



Emerald X emerald (89, 92) gave glaucous in F^ which in Eg 

 gave glaucous to emeralds in the ratio of 9:7. Vilmorin crossed 

 Emereva (emerald) with two other emeralds noted above with the 

 same results. The following results were obtained from 2 F^ plants 

 in F2: 



PROC. AMER. PHIL. SOC, VOL. LV, KK, DECEMBER II, I917. 



