Physiology of the Saprolegniaceae . 369 
No haemoglobin solutions were carried through satisfactorily, so that 
the results on these are omitted. 
F. Saprolegnia mixta , De Bary (form). This can also be considered as 
a form of De Bary’s plant, differing from it on fly cultures by the large but 
comparatively few oogonia with many oospores, and by not more than 
1-2 per cent, of its oogonia having antheridia, as well as in the somewhat 
different appearance of the vegetative zone. 
The original culture came from a jar of Elodea obtained in a pool near 
the Huron River, Ann Arbour, November 9, 1905. The culture from a single 
zoospore was made January 1. The cultures were made in the following 
solutions, containing *05 per cent, leucin and -i per cent, of the inorganic 
salts. Examinations were made during the first ten days 
(a) Leucin -i per cent, solution, without salts. Only a few oogonia 
were found, and these had no antheridia. 
(e) Leucin and potassium phosphate. Oogonial initials were present, 
but no oospores. 
(d) Leucin and calcium nitrate. Several oogonia only were seen, with 
no antheridia. 
(e) Leucin and potassium nitrate. Oogonia scattered, with many 
oospores each, a few with antheridial filaments. 
(/) Leucin and calcium phosphate. No oogonia formed ; gemmae 
finally appeared. 
(g) Leucin and potassium sulphate. Oogonia scattered, large ; about 
2 , 5 per cent, with antheridial filaments both androgynous and diclinous. 
(, h ) Leucin and sodium chloride. Several oogonia and a few antheridial 
filaments. 
(i) Leucin and magnesium sulphate. A few large oogonia with many 
spores, some with antheridia. 
Cultures with NaH 2 P 0 4 , Na 2 HP 0 4 , and (NH 4 ) 3 P 0 4 formed gemmae 
only ; with NPI 4 N 0 3 and Rb(OH) 2 they remained vegetative altogether. 
A few cultures were also made with haemoglobin, using a *i per cent, 
solution, the salts as before : — 
(a) Haemoglobin and peptone. Oogonia scattered, no antheridia. 
(d) Haemoglobin and calcium nitrate. Oogonia abundant, no anthe- 
ridia. 
(e) Haemoglobin and potassium nitrate. Oogonia abundant ; about 
25 per cent, with antheridia, both androgynous and diclinous, sometimes 
from the oogonial stalk directly under the oogonium. 
L. Saprolegnia , sp. As no oogonia were obtained in the cultures of 
this species, it was impossible to determine it. Under all the conditions 
which influenced the production of sexual organs in the species so far 
mentioned, this one remained either vegetative or produced abundant 
gemmae. In very few instances were sporanges or zoospores seen, the 
