1915] PIETERS—ACHLYA AND SAPROLEGNIA 489 
the haemoglobin had a concentration of 0.025 per cent were oogonia 
formed. Of the drawings, fig. 7 is from fly cultures, the others 
from haemoglobin 0.025 per cent. 
S. MONOICA var. vexans, nN. var. 
This was secured from algal material collected at Sukey Lake, 
near Ann Arbor, Michigan. The vegetative growth, sporangial 
characters, and the formation and shape of gemmae do not differ 
in any particular from those present in S. monoica, S. ferax, or any 
other species of that group except S. mixta, which has weaker 
hyphae. The material was cultivated for nearly a year and a half 
on flies, in agar, and by transfer from a strong culture medium such 
as pea decoction or peptone, into haemoglobin, leucin, peptone, or 
other solution. During all this time no oogonia were produced. 
Toward the end of this time a series of tests was being made with 
several cultures by transferring vigorous mycelium to leucin to 
which various sugars and salts had been added. Among other 
combinations there was used leucin neta levulose oom and in this 
a mycelium out of pea extract produced an abundance of oogonia. 
When these were examined they proved to be indistinguishable 
from the oogonia and antheridia of S. monoica Prings. Rarely an 
oogonium was found on which there was no antheridium, but in 
some solutions this may also be the case with S. monoica. 
The fact that cultures of S. monoica were going on at the same 
time suggested the possibility of contamination. Check cultures 
were made, therefore, by taking mycelium from the dish in which 
the oogonia were formed and growing this on fly. Had the myce- 
lium producing oogonia been that of S. monoica (no. 79¢ of my 
series), plenty of oogonia would have been produced. In fact, no 
oogonia were formed on the fly culture, but a fresh culture from this 
fly through pea decoction into leucin and levulose again produced 
oogonia as before. 
We seem to have here, therefore, the remarkable case of a variety 
of S. monoica having lost sexuality, but recovering it under stimulus 
of this special combination, leucin and levulose in concentration 
M each. 
200 
