958 
Journal of Agricultural Research 
Vol. XXXI, No. 10 
foreign and domestic introductions. Several varieties were obtained 
from reliable nurserymen. The wild varieties of the Pacific States 
were obtained through the cooperation of forestry supervisors or 
through personal collection of pits from natural plantings. W. F. 
Wight furnished pits of some of the eastern varieties. 
In Tables I, II, and VIII the following letters are used to indicate 
the difference sources from which the plant material used in this 
study was obtained: 
A A—Arnold Arboretum, Jamaica Plains, Mass. (Seeds and scions.) 
ESC—Author’s collection, Citrus Experiment Station, University of Cali¬ 
fornia. (Seeds and scions.) 
ESK—Kansas Agricultural Experiment Station. (Seed from Albert Dickens.) 
ESO—Oregon Agricultural Experiment Station. (Scions from H. P. Barss.) 
EST—Texas Agricultural Experiment Station. (Seed and scions from H. 
Ness.) 
NB—Luther Burbank Nursery, Santa Rosa, Calif. (Seedlings.) 
NC—Leonard Coats Nursery, Morgan Hill, Calif. (Budded trees.) 
NF—Fancher Creek Nursery (Geo. C. Roeding, manager), Fresno, Calif. 
(Budded trees.) 
NLC—L. R. Cody Nursery, Saratoga, Calif. (Scions.) 
NP—Theodore Payne Nursery, Los Angeles, Calif. (Seeds.) 
NS—Shenandoah Nursery, Shenandoah, Iowa. (Seedlings and budded 
trees.) 
NT—Tribble Brothers Nursery, Elk Grove, Calif. (Root cuttings.) 
UCP—C. A. Parpus through Department of Botany, University of California. 
(Seed.) 
USDA—United States Department of Agriculture, Office of Seed and Plant 
Introduction. (Seedlings and budded trees.) 
USDAF—United States Department of Agriculture, Forestry Service. (Seeds.) 
USDAH—United States Department of Agriculture, San Antonio Experimental 
Farms, Texas. (Buds from H. S. Hastings.) 
USD AM—United States Department of Agriculture, Bureau of Plant Industry, 
Silas C. Mason. (Seed.) 
USD AW—United States Department of Agriculture, Bureau of Plant Industrj^, 
W. F. Wight. (Seeds.) 
The different species were verified by a careful comparison with 
scientific descriptions, and in doubtful cases were further authen¬ 
ticated by submitting material to a botanist who had specialized in 
the genus Prunus. The horticultural varieties were studied critically 
but in many cases could not be positively identified because of their 
failure to fruit. This is especially true of the varieties of P. domes - 
tica. (See Table II.) Italian Prune, German Prune, Heine Claude 
(Green Gage), President, and Bartlett fruited and were apparently 
correctly named. The other varieties in Table II were not authen¬ 
ticated, but the names were used as labeled by nursery. 
THE CROWN-GALL ORGANISM 
The crown-gall organism used in 1913 and 1914 in the inoculations 
on Prunus was isolated from the almond. The organism was re¬ 
isolated in 1914 from Schinus molle , and in 1916 and 1918 from two 
species of Prunus. The cultures used were always in a virulent 
condition, as indicated by the control inoculations, which resulted in 
80 to 100 per cent infection. They were never more than two years 
from isolation. In 1921 a new culture, the last used, was obtained 
from a natural gall found on Prunus besseyi. In all, five different 
cultures have been used, three of which were from artificial galls ’ 
produced by the original culture or by cultures reisolated from them. 
