128 
AMERICAN JOURNAL OF BOTANY 
[Vol. io, 
grown at the three higher temperatures for 3 days and at the lower for 
26 days. A luxuriant growth resulted in 3 days at 20°, 30°, and 40° C., 
thereby furnishing a sufficient amount of mycelium for enzymic studies. 
However, at 9 0 barely enough material for this purpose was produced after 
26 days of growth. The decoction in the two flasks upon which the same 
species had grown was combined into one compound sample, and aliquot 
parts were taken for maceration experiments.. The solution was handled 
and the mycelium treated according to a method previously described (3). 
Maceration was regarded as complete when the disks offered no resistance 
when pulled from opposite directions. The enzymic action of the mycelium 
was determined by suspending 0.50 g. of pulverized material in 25 cc. 
of distilled water, in accordance with methods previously described (3). 
The raw disks (1.5 mm. in diameter and 0.5 mm. thick) which were 
employed to measure the macerating power of the enzym in each experiment 
were cut from within the fibro-vascular ring of one sweet potato. The ex¬ 
periments with all the organisms were repeated several times at each tem¬ 
perature. Flasks in which the enzym was inactivated by steaming, as 
well as flasks containing some of the original decoction which had not been 
inoculated, were employed as controls in all the experiments. The sweet- 
potato decoction was made in sufficient quantity of uniform composition 
for one entire experiment with all the species. 
Maceration was carried out at 40° C. regardless of the temperature at 
which the organisms were grown. The solutions, previously filtered through 
cotton to remove the fungous material, were brought to the temperature 
at which maceration was to take place by exposing them for one hour at 
40° C. before the raw disks were added. After the disks were added to the 
solutions they were examined at frequent intervals in order to study the 
progress of maceration. 
Experimental Data 
The results of the various experiments with each organism at the different 
temperatures have been averaged and set forth in table 1. The length 
of time required to macerate the raw disks completely is given in hours. 
It is hardly necessary to point out that any method no more refined than 
the one employed here is certain to give some variation in the results. 
Some of the factors which have an influence on the results will be discussed 
later. 
Table 1 shows that at only one temperature (20° C.) were data obtained 
on the maceration of the raw disks by all the organisms. At 40° and 30° 
the species microsporus and nigricans made no, or at least such a feeble, 
growth in the time allowed that neither the solution nor the mycelium 
contained a measurable quantity of pectinase. Likewise certain species, 
namely, delemar, chinensis, and maydis , made no growth at 9 0 in 26 days, 
the time allowed for development at the lower temperature. A small 
