254 
WILLIAM J. ROBBINS 
Though the dry weight of the mycehum was not determined (as 
each culture showed complete digestion), the amount of mycelium 
formed in all cultures, with the exception of that in the medium 
lacking iron, was noticeably less than in the full nutrient solution. 
The mycelium was least in the culture lacking all nutrients and in 
the culture lacking nitrogen. The growth in the culture lacking 
potassium differed in appearance from that in the other cultures in 
consisting of a large number of small bunches of mycelium, and not a 
continuous fluffy mass. 
Certain differences were noted between the two sets of cultures 
in the relation of fruiting to digestion. All the cultures of the set 
containing 50 cc. of solution completed digestion before fruiting. 
In the set in which 500 cc. of solution was used, the full nutrient cul- 
ture, and the cultures lacking phosphorus, sulphur, and iron, fruited 
before completing digestion, while the cultures lacking magnesium, 
nitrogen, and potassium did not. It will be noted from the results 
of these experiments, which are summarized in Table VIII, that at 
room temperature Pemcillium camembertii digests 0.2 g. of starch 
in 50 cc. of modified Richaids's solution in 9 days. A deficiency of 
iron, sulphur, magnesium, and phosphorus has little effect on the time 
required for digestion. A lack of nitrogen, on the one hand, and of 
all nutrients, on the other hand, has approximately the same effect, 
tripling the time as compared to that of the full nutrient culture in 
which .2 g. of starch in 50 cc. of solution is used, and increasing the 
time from sixteen to nineteen times when 4 g. of starch is contained 
in 500 cc. of solution. 
Table VIII 
Mediui 
Time for Digestion in Days 
50 Cc. of Solution 500 Cc. of Solution 
.4 Percent of Starch .8 Percent of Starch 
Starch only 
Full nutrient 
Full nutrient minus nitrogen. . . 
Full nutrient minus potassium. . 
Full nutrient minus phosphorus 
Full nutrient minus magnesium. 
Full nutrient minus sulphur. . . . 
Full nutrient minus iron. ...... 
The digestion in the absence of potassium is exceedingly slow. 
It was believed at first that here was a relation between potassium 
