92 
GROWTH IN DIAMETER OF COLONIES (MILLIMETERS) 
At 4 days’ age At 11 days’ age 
On 12 cc. of agar 30c.c. of agar On 12 cc. of agar 30 c.c. of agar 
lew, 22 pl. 8, 32 pl. 1, 60 pl. 8, 85 
ple2. 20 pl. 9, 40 pl. 2, 65 pl. 9,90 
pl. 3, 29 pl. 10, 32 pl. 3, 65 pl. 10, 85 
pl. 4, 32 pl. 11, 40 pl. 4, 63 pl. 11, 85 
plied, 20 pl. 12, 35 pl. 5, 63 
pl. 6, 29 pl. 6, 62 
pl. 7, 27 pl. 7, 65 
Totals, 189 Totals, 179 Totals, 443 Totals, 345 
Av. per pl., Av. per pl., Av. per pl., Av. per pl., 
27 mm. 35.8 mm. 63.3 mm. 86.2 mm. 
It appears that at 4 days the colonies on the deep agar grew more 
than 32% faster than those on the plates with less agar; at 11 days, more 
than 28% faster, the colonies being at the same time more dense. A 
repetition of the test with 16 plates gave at 9 days a growth-average of 
50 mm. on the shallow agar and of 74 mm. on the deep agar—an increase 
of 48% in rate. 
Since it was deemed possible that the differences here noted might 
be due to differences in humidity, the depths of several plates were care- 
fully measured and sufficient agar poured into each to make the air-space 
above the agar in all cases equal, although, since half of the plates were 
shallow and half of them deep, there was a great difference in the depth 
of agar used, which averaged in the deep plates about 11 mm. and in the 
shallow plates about 3mm. The results of this test were almost identical 
with those recorded above. The differences noted, therefore, could hardly 
have been due to differences in humidity, but rather to the amount of 
nutriment available. The graphs of conidial length given in Fig. Eshow a 
larger predominance of short conidia on the deep agar, indicating the contin- 
uance of conidia-formation for a longer period of time. For this reason 
the mean length is much lowered and the coefficient of variability on the 
deeper agars is much higher than on the plates with less agar. 
These results on deep agar are in entire agreement with those already 
given concerning corn shoots (page 90), to the effect that quantity of nutri- 
ment available may influence the growth-characters very markedly, often 
as distinctly as does the quality of the food available. The dilution ex- 
periments with green-wheat agar and corn-meal agar (pages 83 and 84) tend 
toward the same conclusion, though other factors also appear in those cases. 
