83 
Saunders, Pasadena, Cal., sent us plants of Jris unguicularis. 
Nine different species or varieties of wild Iris were collected in 
California and other places. Three species were purchased from 
C. G. Van Tubergen, Ltd., Holland. 
Forest Pathology 
By ArruurR HarMount GRAVES 
Breeding Work With the Chestnut 
As usual, the research work with the chestnut has been carried 
on in collaboration with the Office of Investigations in 
Pathology, Bureau of Plant Industry, U. S. D. A. As an ex- 
ample of the close interconnection of the various branches of 
plant science, this year the heading for this report might just as 
” since nearly all of the work has con- 
lPorest 
well be “ Forest Genetics 
sisted of breeding together the Japanese and American chestnuts. 
However, the original source of all the evil, the cause of the 
tremendous losses we are trying to remedy, is the parasitic fungus, 
Hendothia parasitica, and it is on account of such organisms. that 
the science called plant pathology has come into being 
It is well known that the Japanese chestnut, Castanea crenata, 
is usually a low, round-headed tree, and this statement applies also 
to the hairy Chinese chestnut, C. mollissima, while the native 
American species is characterized by a straight, tall trunk, at least 
when growing in the forest. As regards susceptibility to the bark 
disease, the Japanese tree shows marked resistance amounting in 
many cases to near-immunity. On the other hand, the American 
species is extremely susceptible to the disease, and it is this vulnera- 
bility that has resulted in the almost total disappearance of the 
chestnut as a forest tree from our American woodlands. We 
say “almost total’: there are some counties in West Virginia, 
Tennessee, North Carolina, and Georgia, where a small percentage 
of trees is still uninfected ' with the bark disease. The tremendous 
economic value of the American chestnut and the irreparable loss 
which its passing means to the American people have been set 
forth in my report of 1920. 
1Gravatt, G. F. and Gill, L. S. Chestnut blight. U. S. Dept. Agr. 
Farmers’ Bull. 1641. November, 1930. 
