74 BULLETIN 380, U. 8. DEPARTMENT OF AGRICULTURE. 
are much more severely attacked in the Chekiang Province than 
either in Chihli, Shansi, or Shensi. Could the greater humidity of 
central China be of assistance to a more vigorous development of 
this destructive fungus?” 
COMPARISON OF HOST RELATIONS. 
It will be seen from the above description of the host relations of 
the various species that while some other members of the genus 
(EZ. gyrosa, e. g.) may have slight parasitic tendencies, E'ndothia 
parasitica alone is an active parasite. The contrast is still more 
striking in the section of the genus to which Z’. parasitica belongs, 
for Z. fluens and E. fluens mississippiensis, which resemble FE’. para- 
sitica so closely in their morphological characters, and to a less 
degree on culture media, and are common on Castanea, are almost 
purely saprophytic. This fact is established by the work of Ander- 
son (2), Clinton (18), and others, and by two years’ field observa- 
tions and several thousand inoculations made by the writers and 
their colleagues. 
The host relations of the parasite are equally striking. Although 
Endothia parasitica is so pathogenic on Castanea dentata that this 
tree has been practically exterminated over several hundred square 
miles of its natural range and its extinction is threatened, the fungus 
has been only occasionally found as even a weak parasite on the 
closely related genus Quercus, and never, to the writers’ knowledge, 
on Fagus. 
During the course of this work the writers have been continually 
impressed with the possibilities of a physiological study of /. para- 
sitica and one or more closely related species which might throw 
some light on the fundamental question of the nature and cause of 
parasitism. No other case is known to the writers of a virulently 
parasitic fungus and a closely related purely saprophytic one which 
will grow readily and fruit on a large variety of artificial media, 
which are readily distinguishable on those media, and remain con- 
stant for hundreds of generations. 
SUMMARY. 
The pathological and economic importance of this group of fungi 
was first recognized when the chestnut-blight fungus was discov- 
ered in New York in 1904. 
This organism was first referred to the genus Diaporthe, but 
was later shown to belong to the genus Endothia. 
The specific identity, relationships, and native home of this para- 
site were at first uncertain. Some pathologists considered it a native 
organism which was attracting attention and causing injury chiefly 
