111 
Fiuigi on Culture Media . 
and Fusarium , the experience of the writer is as follows: Uniformity of 
starting is somewhat greater with the latter ; thus it is possible to place very 
similar masses of Fusarium spores on the plates, and, within wide limits of 
size of inoculum, the initial growth of the resultant colony is the same in all 
cases. With Sphaeropsis , the inocula are small portions of mycelium and 
it is not so easy to ensure uniformity of inoculation. The resultant young 
colonies vary more among themselves than is the case with Fusarium , but 
it has been found that if the first two days’ growth be subtracted from the 
following readings, much better agreement is shown. Under suitable con¬ 
ditions the degree of uniformity observed is surprising, and it is a common 
result to find the various controls agreeing among each other to within 
a few millimetres over a diameter of io centimetres. 
The following graphs (Figs. 1-6) will serve to illustrate the different 
types of growth met with in different fungi, and with the same fungus under 
different conditions, and they will indicate the nature of the problems which 
arise in a study of this description. 
In the experiment from which Figs. 1-3 were constructed, the various 
fungi were grown in the usual way on somewhat deep (1 cm.) layers of 
potato agar in closed Petri dishes. The medium was the same in all cases, 
and the growth tests were run concurrently. The experiment was done in 
triplicate, and each measurement is the average six readings, i. e. of two 
from each culture in the set. The ordinate corresponding to each plotted 
point on the curves represents the increment in diameter in the preceding 
•twenty-four hours. 
An examination of the curves in Fig. 1 brings out the following 
particulars: 
In the early stages, the growth-rate increases day by day, so that the 
curve of total growth is convex to the time-axis. 
In the 15 0 C. curve, the growth-rate had not reached a steady value at 
the end of the experiment, by which time the culture had reached a total 
diameter of 10 cm. and had almost covered the whole surface of the medium. 
The 20 0 curve, on the other hand, showed signs of reaching a steady growth- 
rate : and in the curve of growth at 25 0 this limiting value had been reached, 
and a subsequent slight falling off recorded. This falling off is very pro¬ 
nounced in the 30° curve, where growth ceased entirely after the first few 
days. 
The general statement of these results is that the growth-rate increases 
to a maximum which is sooner reached the higher the temperature. At the 
two higher temperatures a decline in growth-rate sets in, which is more 
pronounced the higher the temperature. Whether such a falling off would 
appear at the two lower temperatures if the cultures were grown on a larger 
surface of medium was not determined. It was sufficient for the present 
purpose to show that this fungus would grow to a diameter of 10 cm. at 
