May 16, i 9 ai Respiration of Sweet Potato Storage-Rot Fungi 215 
tritici illustrates this point. On the second day it produced a measur¬ 
able amount of C 0 2 , the quantity steadily increasing up to the fourth 
day. Thereafter it gradually decreased and practically ceased entirely by 
the twelfth day. Penicellium sp., B . cinerea , and 5 . bataticola , on the other 
hand, grew slowly and did not give off a measurable quantity of C 0 2 
for several days following inoculation. The evolution of C 0 2 rapidly 
increased thereafter and continued a considerable number of days before 
it ceased entirely. 
Except with Botrytis cinerea , the day of maximum production of 
C 0 2 was followed by a sharp decline, which continued to the close of the 
experiment. B. cinerea differed from all the other organisms in that there 
was a period of two or three days when the maximum C0 2 production 
remained about constant. However, it is probable that if determinations 
had been made in less than 24-hour periods an apex in the curve would 
have been shown for this fungus. 
DRY WEIGHT OE MYCELIUM 
A direct comparison of the dry weight of the different organisms is not 
possible for reasons that can be well understood. As previously pointed 
out, the fungi were allowed to grow as long as a measurable quantity of 
C0 2 was given off. This varied from 11 to 30 days, so that some fungi 
had a much longer time to form mycelium. Furthermore, some fungi 
will produce a much larger quantity of dried material than others under 
identical conditions; in fact, it was shown by Kunstmann ( 14 ) that in 
duplicate cultures of the same fungus two and one-half times as much 
dried material might be produced i'n one flask as in another. 
An examination of Table I and the curves in figure 1 will show that 
although the experiments with Botrytis cinerea ran for 38 days, Penicil- 
lium sp. produced about 11 per cent more dry weight in 10 days less time 
and that Sclerotium bataticola produced a greater dry weight in 25 days 
than B. cinerea , which grew 12 days longer. Mucor racemosus and Rhiz- 
opus tritici were grown 23 and 12 days and produced 1.13 and 0.94 gm. of 
dry weight, respectively. A comparison of M. racemosus with S. batati¬ 
cola shows an even more striking difference, the ratio of dry weight being 
approximately 1 to 5.5. 
