8 
of the crosses have proved to be remarkably free from covered 
kernel smut for a period of several years. On the other hand, the 
susceptible parent in each cross has always given a large number 
of infected plants. In one of the crosses the F, plants have 
proved to be quite susceptible, almost as many individuals being 
infected as in the case of the susceptible parent. In the other 
cross, however, the F, plants have all shown a high degree of 
resistance, relatively few plants being infected. The results 
suggest that different factors are involved in the two series, 
but additional studies are necessary before the problems can be 
cleared up. 
Some studies have been made on the head smut (Sorosporium 
reiianum) of sorghum and corn. This fungus is particularly 
interesting because of its occurrence on both of these crops. 
In the experiments rather low percentages of infection on sorghum 
have been obtained, while on the other hand there has been a very 
severe infection of maize, at least in some of the experiments. 
The results indicate that the smut collected on corn is not 
capable of infecting sorghum and likewise that the smut collected 
on sorghum is incapable of infecting corn. 
Cryptogamic Herbarium.—Very marked progress was made in 
mounting the specimens of the Bubak collection. Practically all 
of these, with the exception of the higher Basidiomycetes, have 
been mounted and distributed in the herbarium. This work has 
involved a great expansion of our storage facilities. Only a few 
specimens have been added to the cryptogamic herbarium during 
the year, namely, a total of 205, of which 200 were purchased 
and five received in exchange. 
Forest Pathology 
By ARTHUR HARMOUNT GRAVES 
. Chestnut Bark Disease Investigations.—As stated in the 
a for 1924 (pp. 42-43), experiments were begun in that year 
in collaboration with the Laboratory of Forest Pathology, 
United States Department of Agriculture, to determine the 
causes and conditions for the development of vigorous shoots 
from the bases of chestnut trees apparently killed by the blight. 
One series of experiments was concluded in August, 1925, and 
