RELATION BETWEEN VEGETATIVE VIGOR AND REPRODUCTION 54 1 
the second place to weigh the myceHa. Any insoluble substances 
would introduce an element of error by adhering to the fungus hyphae. 
When pea extract was used this was prepared by sterilizing about six 
peas with a hundred cubic centimeters of distilled water. If carefully 
sterilized, the peas did not break up. Any flasks in which the peas 
had broken up were discarded for these experiments, as the loose 
starch grains would surely adhere to the fungus and increase the 
weight. Peptone was used as a source of both nitrogen and carbon 
and in a few cases haemoglobin was used. Asparagin and leucin 
were tried but the growth was so poor that these substances were not 
considered satisfactory; Klebs ('99, p. 520-523) also found that 
growth took place in lower concentrations of peptone than of leucin. 
The latter is very expensive to use for so large a number of experi- 
ments as had been planned, and is moreover of a rather uncertain 
quality. In the course of the work there was occasion to try the leucin 
from three prominent German makers and no two were found to give 
like results. Synthetic leucin was once used, but proved to be so 
toxic that little growth took place in it. Carbohydrates were added as 
an additional source of carbon. At first sucrose alone was used, but 
later maltose, levulose and dextrose were added. For salts, potassium 
nitrate, magnesium sulphate, and potassium phosphate, either mono- 
or di-basic were added. Wherever in the tables the term ''salts" is 
used, the above salts, in concentration to total i/ioo or 1/200 mole- 
cular, are meant. In the earliest experiments these salts were used 
in a strength of o.i percent or 0.05 percent but later molecular weights 
only were used. In some cases each salt was used separately. 
Experimental 
Experiments with Achlya racemosa 
This species offers advantageous material because it will produce 
in water oogonia with oospores and antheridia. It is not necessary 
to transfer to another food solution ; it is only necessary to prevent the 
too rapid formation of sporangia. This can be done by placing the 
mycelium in a temperature of 24 degrees, at which temperature few 
sporangia are formed, while the formation of oogonia is not interfered 
with. The mycelia for the following experiments were grown for 
seven days in 50 cc. of the following solutions. 
(i) Peptone o.i percent, sucrose i percent, salts o.i percent; 
(2) peptone 2 percent; (3) peptone i percent; (4) peptone 0.5 percent; 
