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 : 



(i) 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 



