614 
Journal of Agricultural Research 
Vol. XXI, No. 9 
The flasks were inoculated with spores and bits of hyphae from stock 
cultures which were kept in a vigorous state of growth. Incubation was 
carried out in the dark at a constant temperature, the temperature used 
depending on the character of the experiment. 
UTILIZATION OF THE MYCELIUM AND SOLUTION 
At the end of the incubation period the fungus growth was removed, 
washed in running water for 15 minutes, the water squeezed out by 
hand, and then treated with acetone and ether, according to Dox’s (7) 
modification of Albert and Buchner’s method for preparing “Aeeton- 
dauerhefe.” After washing, the operation is essentially as follows: 
The mycelium is immersed for 10 minutes in a large excess of acetone 
and constantly stirred, the hyphae being torn apart by forceps at the 
same time. The material is then squeezed to dryness and immersed in a 
fresh supply of acetone for 2 minutes with constant stirring. It is again 
squeezed to dryness and stirred for 3 minutes in ether, after which it is 
laid out to dry. After the odor of the ether can no longer be detected, 
the mycelial mass is put in flasks and stored at 9 0 C. until required for use. 
Except in so far as it was necessary to meet the requirements of special 
experiments maceration of raw sweet-potato disks was carried out by 
the use of 0.25 gm. of the mycelium ground to a powder in fine quartz 
sand. The sand used for grinding Was thoroughly washed in distilled 
water and then burned in a crucible for two hours. The enzym powder 
was then transferred to 120-cc. Erlenmeyer flasks, and 25 ec. of distilled 
water were added. Several, usually five, raw sweet-potato disks 1 mm. 
thick and 15 mm. in diameter were placed in each flask containing the 
suspension of hyphae and sand. The disks were always cut from that 
part lying within the fibrovascular ring of the potato, since the tissue 
there is more uniform, being made up largely of thin-walled parenchyma 
cells with only here and there a vascular bundle. 
The tissue inside the fibrovascular ring of different sweet potatoes has 
been observed to differ somewhat in character and to react differently 
to the macerating agent. In view of this fact each experiment was 
always conducted with disks taken from the same root. The potatoes 
were carefully selected for soundness of the internal tissue, and any show¬ 
ing cavities or pithiness were rejected. In a few preliminary experiments 
the air was removed from the disks by suction before they were put in 
the solution. However, this practice was found to be unnecessary and 
was finally abandoned after the results showed that the rate of macera¬ 
tion was neither increased nor decreased by the air in the tissue. 
The flasks after the disks had been added were incubated at a constant 
temperature, and notes were taken of the progress of maceration from 
time to time. Loss of coherence of the tissue was regarded as complete 
when the disks offered no resistance to pull. In a determination of the 
