CHESTNUT BARK DISEASE. 429 
oat-juice agar favors a vigorous aerial mycelial development, 
especially for E. gyrosa. The bean-juice agar is somewhat 
intermediate in both respects. On any of these media, E. gyrosa 
is much less likely to exude spore masses in abundance than the 
variety parasitica. Perhaps this accounts for the ease with 
which the variety propagates itself in nature. The chief cultural 
differences of the two are as follows: 
(1) Var. parasitica fruits more abundantly, and exudes the 
sticky spore masses much more conspicuously, than does 
Endothia gyrosa. (2) The variety fruits earlier than the species, 
as determined by the exuding spore drops. (3) The variety has 
less evident, smaller, or more embedded fruiting bodies than the 
species, in which they are often elevated, distinct pustules, 
rarely hidden by the exuding spore mass. (4) The species 
develops a much more luxuriant aerial mycelium (except pos- 
sibly on potato agar) than does the variety. (5) The species has 
its aerial mycelium more generally and more highly orange col- 
ored, especially on oat-juice agar, than does the variety. 
The more minute and variable differences of the two on the 
three media are as follows: On the potato-juice agar var. 
parasitica forms chiefly an embedded growth, which, while white 
at first, soon becomes rather deeply colored, and produces numer- 
ous obscure or embedded fruiting bodies, which exude small, 
colored, sticky spore drops rather thickly over the surface of 
the agar. Finally, a slight surface growth of a flavus mycelium 
sometimes develops. The species differs in having at first a 
slightly more evident growth of mycelium, and finally having 
usually fewer, but larger, spore masses. The color of the em- 
bedded growth is variable, usually darker than in the variety, 
sometimes blackish, as if from bacterial contamination, but 
possibly due to variation in the composition of the medium. 
On the Lima bean-juice agar var. parasitica produces fewer, 
but larger, fruiting bodies and spore drops than on the potato- 
juice agar, while its aerial mycelium is more evident, and varies 
from albus to sulphureus in color. The species makes a.much 
more evident aerial growth than the variety, while its fruiting 
pustules are decidedly fewer, larger, more elevated and distinct, 
and exude spores less abundantly. The color is much more evi- 
dent than in the variety, though variable even in the same tube, 
running from albus through sulphureus and flavus to even 
