A PARASITIC BOTRYTIS ON PEPPER AND LETTUCE. 63 
(49), large areas surrounding the mycelium appear to be 
dead, showing that the fungus secretes some substance which 
kills the tissues in advance of the hyphe. Strictly speaking, 
then, the fungus is always a saprophyte, because it invariably 
lives on dead tissue, and its ability to penetrate living tissue 
bougie, was quite concentrated, free from any foreign sub- 
stance secreted by the hyphe. 
To carry this point a step further the writer obtained an 
extract from the mycelium and spores by collecting them from 
the cultures and grinding the material with clean quartz sand 
inamortar. To obtain as concentrated an extract as possible, 
only a few cc. of water were added to the mass and the whole 
placed in a hydraulic press. The extract, passed through a 
bougie, was quite concentrated, free from any foreign sub- 
stances and sterile. 
A petiole of the lettuce submerged in the extract darkened 
and disintegrated very rapidly; acting for a longer time, 
weaker concentrations gave the same results. The point that 
attracted attention was that the tissues one to two centimeters 
above the liquid, were discolored and fell to pieces rapidly. 
On boiling the extract for varying lengths of time and placing 
the petioles of lettuce leaves in them the same characteristic 
changes in the tissues occurred. Sections of the tissues 
showed that the microscopical changes were in all cases similar 
to those observed in the diseased lettuce leaves. 
Working along the line suggested by Smith, the next step 
was to ascertain the nature of the substance that caused the 
disorganization of the plant cells. Using several delicate tests 
for oxalic acid, negative results were obtained in each case. 
These were repeated a number of times with the same result. 
Solutions of oxalic acid of different concentrations when 
applied to the petioles showed an action on the tissues some- 
what like that of the extract, except that the tissues were 
bleached instead of becoming darker in color. Solutions of 
acetic, gallic, malic and tartaric acids of the same strength 
as the oxalic acid used, affected the tissues of the petioles in 
much the same manner. It may be, then, that the substance 
