1915] PIETERS~ACHLYA AND SAPROLEGNIA 487 
the botanical laboratories of the University of Michigan, of unknown 
source, but doubtless from around Ann Arbor. 
Hyphae stiff, medium thick, forming a dense zone about the fly. 
Among these are large, coarse, branched hyphae attaining a length 
of 10-15 mm. or sometimes more; sporangia cylindrical, dischar- 
ging and forming secondary sporangia asin A. prolifera, but develop- 
ing in pea agar or in pea extract when this is absolutely quiet; 
oogonia on short lateral branches which are about as long as the 
diameter of the oogonia, rarely at the ends of long hyphae, but 
nearly always on the basal portions of strong hyphae, near the body 
of the fly, never intercalary; round or slightly oval in shape; 
oogonium wall smooth, not pitted, oospores 4-10, averaging about 
25 w in diameter, excentric; antheridia always present, of diclinous 
origin, partly clasping the oogonia, never clavate nor wrapped about 
the oogonia; gemmae produced in chains by the breaking up of the 
large hyphae, cylindrical, sometimes slightly branched or with one 
or more protuberances at one or both ends. 
This species is peculiar in the fact that besides the zone of 
delicate hyphae which usually surrounds the fly, there were also a 
number of very long, thick hyphae. These commonly extended 
for several millimeters beyond the thick tuft of hyphae and spread 
out on the surface of the liquid, later becoming densely filled 
with protoplasm and breaking up into chains of gemmae as shown 
in fig. 2. 
Oogonia are produced quite regularly on flies and are always 
clustered near the body of the fly, but so far, with one exception, I 
have been unable to secure oogonia in artificial media. In one test 
a sterilized pea on which the fungus was growing was left in an open 
dish of distilled water. Bacterial decay set in slowly, the water 
was changed from time to time, and the fungus kept on growing 
vigorously, eventually forming oogonia. In no solution of haemo- 
globin or leucin, with or without salts or sugars, have oogonia with 
oospores appeared, though empty oogonia have been occasionally 
formed in haemoglobin. In one case penetration of the oogonium 
was observed (fig. 3), but whether fertilization takes place is not 
known. This species shows affinities with A. DeBaryana Humphrey 
in the excentric oospores and smooth unpitted oogonia, but the 
