546 
ADRIAN J. PIETERS 
S. mixta produced oogonia readily in 0.05 percent haemoglobin and 
Kauffman that S. hypogyna produced oogonia readily under similar 
conditions. Preliminary tests showed that S. ferax behaves like the 
above species and in all subsequent work haemoglobin, either alone 
or with salts and sugars, was used as the transfer solution when it was 
desired to test for oogonia. Unfortunately commercial haemoglobin 
is not of uniform purity and it sometimes happened that a solution 
made up to 0.05 percent was stronger or weaker than expected and thus 
either encouraged unusual growth or the formation of sporangia. 
Either event worked disadvantageousl}^ for the production of oogonia. 
The different tests could not of course be carried on at the same 
time and hence were subject to variations in temperature. Klebs 
showed that a temperature of 18° C. was favorable for the production 
of oogonia in S. mixta but under the conditions prevailing in the 
laboratories of the University of Michigan such temperatures are 
almost impossible to maintain. The room temperature is generally 
20° C. and above, temperatures at which oogonia are not readily 
produced. Some tests were therefore carried on in the basement of a 
private house while others were conducted in a small closet built in 
from a window in the botanical laboratory and opening to the out- 
side by a swinging window. By doing the work in the winter and by 
using an electrically heated incubator, fairly satisfactory temperatures 
could be maintained but not exact enough to reach any conclusions 
as to the optimum temperatures for reproduction. The following 
record will, however, show the difference between the number of 
oogonia produced at lower and at higher temperatures. Mycelia 
Table VI 
Saprolegnia ferax. Mycelium Out of Media Under Column i. Transferred to Haemo- 
globin and to Haemoglobin and Salts at Different Temperatures. 
Average Number of Oogonia in 25 Square Millimeters 
I 
2 
3 
4 
5 
Medium 
20°-23° C. 
Haemoglo- 
bin o.osj^ 
140-18° c. 
Haemoglo- 
bin o.o5^c 
200-23° c. 
Haemoglo- 
bin 0.05^, 
Salts 0.15;^ 
14O-180 c. 
Haemoglo- 
bin 0.05^, 
Salts 0.15^ 
Peptone 2% 
13 
19 
15 
5 
21 
70 
67 
176 
51 
59 
15 
5 
4 
15 
198 
142 
157 
163 
155 
Peptone 1% 
Peptone 0.1% + Knop's Sol. 0.05%. 
Peptone 0.2% + sucrose 1% 
Peptone 0.1% + sucrose 0.1% 
