1914) 
COOLEY—SCLEROTINIA CINEREA 301 
a pure culture of the fungus. These segments were immersed 
in 70 per cent alcohol just long enough to partially kill the 
fungous filaments and the host cells, yet not long enough to 
discolor the sound tissue or to modify or change the color of the 
diseased tissue in any way. From this material razor sections, 
containing both diseased and healthy tissue, were made, stained 
for a short time in eosin, and then partially destained with 
alcohol. If the pieces of plum had not remained in the alcohol 
for a sufficient length of time, the razor sections were immersed 
in 70 or 95 per cent alcohol before staining. By employing 
this method it is possible to stain the fungous filaments deeply, 
while the host tissue remains unaffected. Indeed, this method 
permits of a rather sharp color differentiation between the 
healthy and the diseased tissue, the latter being blackened by 
the disease. This method, though quite applicable for the pur- 
pose at hand, was primarily developed for another purpose, 
which will be discussed below. 
Since every fungous filament is very sharply differentiated, 
one may readily study the course of the hyphæ with reference 
to the host cells. By staining, sectioning, and examining dis- 
eased material taken from the margin of the infected area, one 
finds the fungous һурһе penetrating the cells at any point of 
contact; indeed, after examining а number of specimens by the 
method reported above, the writer finds no indications that the 
fungous hyphe follow the middle lamellze, as has been reported 
by other investigators (57, 6) for pears and other fruits. 
The above method also enables one to contrast the cell walls 
of infected and penetrated cells with those of normal tissue. 
It is entirely possible that the fungous filaments, on coming in 
contact with a cell wall, secrete just enough enzyme to dissolve 
their way through the cell walls, leaving the walls of the host 
cells surrounding the hyphæ entirely normal, i. e., without 
swelling or disorganization. 
Another and somewhat different experiment was performed 
to get additional evidence on this point. From sound plums 
which had previously been rendered sterile by washing in bi- 
ehloride of mereury solution (1-1000) and sterile distilled water, 
free-hand sections were cut with a razor sterilized in 50 per cent 
aleohol. Тһе sections were arranged in hanging drop cultures 
