574 
ADRIAN J. PIETERS 
The Value of Phosphates 
No attempt was made to determine the need of the fungus for 
inorganic nutriment. This would have been difficult, if not impossible, 
with peptone as the source of nitrogen, as the peptone itself contains 
a large percentage of total salts. An analysis of the Witte peptone 
used showed 2.78 percent total salts and a qualitative test revealed 
the presence of phosphates, sulphates, chlorides, and of potassium, 
sodium, magnesium, calcium, aluminum, and of ferric iron (K3(Fe- 
Cu)6), so that it was manifestly impossible to exclude the presence of 
all of these salts except the one wanted for a particular experiment. 
However, the tests in which certain salts were added to the culture 
medium showed that with an abundant supply of phosphates Sapro- 
legnia developed a greater capacity for the production of oogonia 
than when other salts were added, and this irrespective of whether 
potassium, sodium, or calcium phosphate weie used. This result is 
in general agreement with the conclusions of Klebs, that the phosphates 
favored the production of oogonia, though Kauffman secured as good 
results from some of the other salts as from the phosphates. 
In Achlya prolifera the increase in growth due to the phosphates 
was marked, but in this case the mycelium may have carried over 
sufficient reserve material to produce a vigorous growth in the peptone- 
sucrose solution, and thus prevented the formation of oogonia. 
Summary 
1. There is no constant and necessary relation between vegetative 
growth and sexual reproduction when the food offered exceeds the 
minimum concentration necessary for the given species. 
2. The minimum concentration of food necessary varies with the 
species but lies, in general, in the neighborhood of o.i percent peptone 
for the production of both sporangia and oogonia. 
3. While growing vegetatively a mycelium may develop tendencies 
that may affect the number and character of the reproductive organs 
produced under subsequent and different conditions. 
4. Of the carbohydrates used maltose and levulose are especially 
useful for vegetative growth and the latter has an especial value for 
the production of oogonia. 
5. Sucrose is probably not used by species of Saprolegnia or of 
Achlya unless it is first inverted by some other agency. 
