O4 
and May series showed more rapid recovery and growth, includ- 
ing some flowering, than the July and September series. Poor 
survival of both treated and untreated plants of Iris halophila 
and the Southern iris was obtained in April and May. This be- 
havior corresponds to the normal failure of these iris to respond 
to transplanting at that season. The final analysis of these re- 
sults will require observations next season. 
These investigations offer considerable promise because methyl 
bromide fumigation is now the recommended method for cradi- 
cating Japanese beetle larvae from nursery stock intended for 
shipment outside of the quarantine areas. Since the dosage of 
methyl bromide (21% Ibs.) is the same for Japanese beetle and iris 
thrips control, a knowledge of the tolerance of iris to this chemical 
will have a two-fold value. 
Student Volunteers 
Miss Olga Jonelunas and Miss Georgianna Jurasek, students in 
Hunter College, volunteered their services in connection with 
some of the experimental work. 
CHESTNUT BREEDING WorK IN 1941 * 
By ARTHUR HARMOUNT GRAVES 
This work has as its main object the development, through 
breeding, of a timber type of chestnut, resistant to the blight or 
bark disease. This disease has killed practically all the mer- 
chantable chestnut timber in the United States, throughout the 
natural range of this tree, involving a loss of many millions of 
dollars. The disease is caused by a fungus, Endothia parasitica. 
Since the Japanese chestnut (Castanea crenata) is compara- 
tively resistant to the blight, we crossed this with the American 
species, C. dentata, aiming to combine the height growth of the 
American with the disease resistance of the Japanese. The 
Japanese trees are rather low in stature, and could never replace 
the American chestnut as timber grees. The first crosses from 
which we now have trees growing were made in 1931, so that 
these Japanese-American hybrids have now completed their tenth 
*A more detailed account will be published in a forthcoming issue of the 
Bulletin of the Torrey Botanical Club. 
