60 
writer to be pathogenic to Betula lenta (Mycologia 11: 113-117, 
1919), B. lutea, and B. papyrifera. B. popultfolia is also probably 
susceptible and good cankers have been found on trees of this 
species north of Hollis, Long Island, but no perithecia have yet 
been observed. 
Genetics and Plant Breeding 
Investigations on the Laws of Heredity and Variation in Plants 
Hardiness and geographic distribution. By ORLAND E, WHITE 
Data on some genetic aspects of the cold-resisting ability or 
hardiness of herbaceous perennials and woody plants and 
geographic distribution have been collected for a number of 
years. A preliminary paper covering this study was published 
in the January, 1926, issue of the Brooklyn Botanic Garden 
RECORD. 
The Genetic Analysis of Peas (Pisum). By ORLAND E. WHITE 
and Dorotnuy I. NEFF 
Investigations on inheritance and variation in several hundred 
varieties of field and garden peas have been carried on in 1925, 
as in previous years. These varieties, collected from all over 
the world where peas are grown, include both wild and cultivated 
types, varieties, and species. Many have very peculiar and 
little known characters. Through crossing these various kinds, 
and studying the inheritance of the characters by which they 
differ, a better understanding of the laws underlying inheritance 
and variation and their relation to environment is obtained. 
Year by year, the inheritance of characters previously not 
investigated is worked out and their relations to the already 
known facts determined. In this manner, more light on the 
problems of inheritance in general is secured. 
Accounts of these studies have been published and referred to 
in previous years. The series ‘Inheritance Studies in Pisum’? 
now consists of five numbers. Studies have been completed 
during 1925 for two more numbers. One of these deals with a 
very extended study of the inheritance of height in peas and its 
relation to other characters. The other study involves foliage 
and cotyledon characters. Four types of foliage color were 
