44 



mental treatment, was 1.38 per cent., with a maximum in one 

 case, m 1920, of 7.07 per cent, due possibly to the effect of low 

 temperatures prevailing- in late fall when pollination and fertiliza- 

 tion took place. In all about ten different mutant types appeared, 

 one of which, called Nubbin, has never before been observed in 

 Dr. Blakeslee's cultures. The mutant form called Microcarpic, 

 when selfed gave rise to albinos in the Mendelian ratio of three 

 albinos to one normal green plant. A preliminary report on these 

 experiments was presented at the Boston (Cambridge) meeting of 

 the Botanical Society of America, December 28, 1922. Further 

 studies are necessary in order to establish whether or not the re- 

 sults obtained may, without question, be attributed to the influence 

 of the radium rays. 



Genetic studies on peas, by Dr. White, were resumed in the 

 fall and the inter-relations of the hereditary factors already dis- 

 covered in the genus are being worked out. The factor A (pro- 

 ducing rose or salmon-pink flowers) has been found when asso- 

 ciated in the same plant with Factors la and P,- (factors for an- 

 thocyanin pod coloring) to give reddish-pink pods in place of the 

 ordinary green pods. When the factor B (which modifies the 

 expression of A and gives reddish purple flowers') is present, in 

 addition to the factors mentioned above, the pods are dark purple 

 in color. Purple tinged pods have been produced on white flow- 

 ered plants from crosses involving in part a purple-pod ancestry. 

 Green-podded segregates from a similar ancestry have also given 

 purple-podded plants. A summary of Dr. White's work on the 

 genetics of peas has recently been incorporated in a chapter on 

 Breeding Vegetables (pp. 236-241) in an agricultural textbook 

 entitled Breeding Crop Plants, by Professors Hayes and Garber 

 of the University of Minnesota. 



Upon his return from South America, Dr. White was elected 

 editor of the genetics section of Botanical Abstracts, and during 

 the latter part of the year he has devoted considerable time to this 

 work. 



Dr. Benedict, Resident Tnvestigator, has continued his investi- 

 gations on the variation of the Boston fern and related forms of 

 Nephrolepis. During 1922 particular attention has been paid to 

 (1) reversions of tertiary and higher sports of Boston fern; (2) 



