3«4 
Journal of Agricultural Research 
Vol. V, No. 9 
The killing of the host cells, so far as is revealed by the microscopical 
examination; seems due principally to a modification of the osmotic 
relations of the cells as a result of the disappearance of the middle lamella 
and to much of the liquid contents of the cells being withdrawn by the 
fungus to be used in its development. In the plum the chloroplasts and 
chromoplasts contained in the cells lying directly under the epidermis 
appeared not to be disintegrating in those cells which had not so col¬ 
lapsed as to make observation impossible. The cytoplasm of the deeper- 
lying cells was very scant, but showed evidences of plasmolysis, often un- 
mistakablyin advance of the penetration of the hyphse (PI. XXXIX,fig. 3). 
middle-lamella solvent 
The nature of the substance secreted is not at all clear. From the 
effect on the host tissue it would appear that the middle-lamella-dissolving 
enzym pectinase was produced, but attempts to isolate it were without 
success. 
Juice was pressed from rotten portions of apples and loquats (Eriobotrya 
japonica) infected with the brown-rot fungus. This was filtered under 
sterile conditions, in some cases through coarse, and in others fine filter 
paper. Slices of healthy apple and loquat fruits were partially immersed 
in the liquid, but showed no softening effect in any case after several 
days. Further trials with a method to be described later, used in sepa¬ 
rating pectinase from Penicillium expansum , also gave negative results 
with S. cinerea. 
In another case a partially rotted apple plug was put into a test tube on 
cotton above commercial formalin so that the plug did not come in con¬ 
tact with the liquid. It was thought that the fungus would be killed by 
the fumes, but that if a pectinase were present it would continue to rot 
the tissue. No further rotting took place, and at the end of five days the 
tissue, unaffected at the beginning, was still firm and of normal color. 
An attempt was made to isolate the enzym pectinase from a culture of 
S. cinerea , 86 days old, on apple cider. The method used was that de¬ 
scribed by Pringsheim (1910), which consists, in brief, of thorough drying 
of the material with acetone, followed by pulverization of the dried 
material and extraction of the enzym with a small quantity of water. 
On May 8, 1915, succulent twigs of B X W21 plum, sand cherry, and pear 
(Pyrus betulifolia ) were partially immersed in the liquid extract in test 
tubes; also pieces of ripe apple the flesh of which was slightly mealy, and 
pieces of young peaches, one-quarter grown, were entirely immersed. 
The tubes were placed in a constant-temperature oven at 35 0 C. Checks 
were run, using water in place of the extract. 
After 24 and 48 hours the plum, pear, and sand-cherry twigs showed 
no effects from the treatment other than a slight wilting. The tissues 
were not softened. The blocks of green-peach fruit showed no softening. 
After 15 hours the apple plug had softened slightly over the surface, but 
