128 
The American Naturalist. [February, 
the germs on the end of a sterilized platinum wire. 
The vessels were then placed in a brood oven at a 
temperature of 35°C. Within 12 hours the nutrient 
fluid became very turbid and began to give off gas 
bubbles rapidly. 
After 8 days three vessels were opened and the 
potatoes taken out. Tubers and broth were examined 
immediately. In places the skin of the tubers ex- 
hibited folds and the tissue underneath appeared to 
be soft. When these spots were cut out and examined 
microscopically the entire tissue was found to be 
honeycombed, the intercellular substance being 
strongly swollen or entirely dissolved, the cell mem- 
branes wholly or partially destroyed, and the starch 
grains free in places. 
After 14 days more vessels were opened and the 
potatoes removed. Under the skin of these tubers 
there were very soft spots and exact investigation 
showed that in these places the tissue was almost en- 
tirely destroyed so that great cavities were formed. 
The softened tissues surrounding these cavities gave 
a faint acid reaction and contained numerous bac- 
teria. 
Finally, after 20 days, the remainder of the potatoes 
were removed from the broth and examined. By this 
time the appearance of these tubers had entirely 
changed. They consisted only of bloated sacks filled 
with a half fluid pulp. Exactly as in case of the 
original wet rotten tubers the contents consisted of 
free starch grains, single cells and groups of cells, 
cell membranes, remnants of protoplasm, and myriads 
of bacteria. The fluid pulp gave a strongly acid re- 
action and had a smell like butyric acid. When such 
tubers were pressed, gas bubbles came out. Taken 
out of the nutrient fluid and kept in a damp chamber 
at 25°C., the tubers rapidly underwent a still further 
decay. After 12 hours the smell of butyric acid dis- 
appeared and the tissues showed a strong alkaline 
