RELATION BETWEEN VEGETATIVE VIGOR AND REPRODUCTION 573 
in which the following salts were added to the peptone and sugar, 
magnesium sulphate, potassium nitrate, and di-hydrogen* potassium 
phosphate, each salt being present in 1/600 molecular. A third series 
was like the second except that mono-hydrogen potassium phosphate 
was substituted for the di-hydrogen. The two series containing salts 
were steiilized at 110°, 115°, and 125° C. These solutions and tem- 
peratures were selected because they represent the conditions of the 
foregoing experiments and not for the purpose of making a detailed 
study of the reactions involved; quantitative determinations of the 
amount of invert sugar present in each lot after being sterilized for 
30 minutes were made by Mr. R. B. Harvey, PhC. Of the solutions 
sterilized at 110° C. those with peptone and sugar alone and with the 
mono-hydrogen phosphate showed no inversion, while in that with 
the di-hydrogen phosphate 1.2 percent of the sucrose had been in- 
verted. Sterilized at 115° C. the peptone-sugar solution and the 
solution containing mono-hydrogen potassium phosphate showed a 
trace of inversion, not enough to express in percentage, while in that 
containing the di-hydrogen 1.9 percent of the sucrose had been in- 
verted. When the temperature at which the solution was sterilized 
went up to 125° C. 1.2 percent of the sucrose had been inverted in the 
solution containing peptone and sucrose only, 0.6 percent in that 
containing mono-hydrogen potassium phosphate, and 4.7 percent in 
that with di-hydrogen potassium phosphate. The fact that more 
inversion took place when the di-hydrogen potassium phosphate was 
used is interesting because this was used in practically all of the 
solutions made up for the experiments with Saprolegnias. On the 
whole the results correspond to those obtained by Deerr: at 110° C. 
there was no inversion, while at the higher temperatures an increasing 
amount of sucrose was inverted and when salts, including the di- 
hydrogen potassium phosphate were used a considerable amount of 
invert sugar was present before the solution was inoculated. Invert 
sugar was therefore available but varied in amount in different solu- 
tions and under different conditions. 
We may conclude that S. ferax does not contain invertase and 
cannot make use of sucrose. In sterilized culture media, however, 
there is sure to be more or less invert sugar present owing to the 
inversion caused by heating and by the presence of salts. What has 
been shown to be true of 5. ferax is equally true of the other Sapro- 
legniaceae so far as they have been studied by the writer. 
