45 
added by purchase. We also secured seventy specimens of 
Ustilagineen Europas, issued by H. Zillig. Nine specimens were 
received from the Museum of the University of Cluj, Rumania, 
on exchange. Dr. Herman Poeverlein of Speyer, Germany, sent 
us one hundred and twenty-eight specimens of rust on exchange. 
Forest Pathology 
By ARTHUR HARMOUNT GRAVES 
Chestnut Bark Disease Investigations 
In the work of 1925, the results of which have been published 
elsewhere (Science 63: 164-105. 1926; and Phytopathology 16: 
615-621. 1926), it was definitely established, through the data 
resulting from inoculation work, that the roots of the chestnut 
are more resistant to the blight fungus than the trunk, branches, 
or basal shoots. The cause of this greater resistance of the roots 
was referred hypothetically to the known greater quantity of 
tannin in the root tissues, the published statement being as fol- 
lows: “In view of previous work indicating an inhibitory effect 
of tannin on the growth of fungi, it is suggested that the greater 
resistance of the root tissues may be due, at least in part, to their 
ereater content of tannin compounds or of substances associated 
with tannin.” (Phytopath. 16: 620.) 
However it is possible that the comparative lack of air, as well 
as other external factors which are materially different in the 
ground and in the atmosphere, may produce a retarding effect on 
the growth of the fungus in the tissues of the host below the 
fila 
surface of the soil. 
During the past summer, in order to test the effect of these 
external factors, three series of inoculations were made, in each 
case on an equal number of roots, and trunks or shoots of the 
same tree. In each series, after inoculation, the roots were 
treated in a different way, as follows: 
Series I. Left exposed to the air. 
Series II. Covered with soil. 
Series III. Covered with dead leaves. 
