900 
Journal of Agricultural Research voi. xxiv, No. n 
increased. In fact, the alcoholic precipitate from cultures 6 days old 
and the filtrate from cultures 21 days old produced no visible effect on 
the middle lamella. This deterioration or inhibition of the action of the 
pectinase from age is quite different from the rapid action obtained 
with pectinase from cultures of Bacillus carotovorus 21 days old. 
ACTION ON TH^ cellulose 
The passage of this fungus through the cell walls is shown by the 
drawings in Plate 3, N-T, and by the intracellular filaments in the photo¬ 
micrographs of Plate I. The drawings in Plate 3, N-T, were made from 
partly destroyed cells of a disintegrating area of the fruit. Only the 
tips of growing hyphae are shown passing through the somewhat wavy 
and more or less separated walls. The penetration of the cell walls of 
normal cells by young germ tubes was also observed by means of the 
microscope. The more important details of this process will be described 
later. 
No visible effect was made on the walls by the filtrate, by the alcoholic 
precipitate from the filtrate, nor by the mycelium in the presence of 
sufficient chloroform or toluene to inhibit its growth. Moreover, bits 
of filter paper placed in fresh cultures of the fungus and allowed to remain 
there for 10 days to 2 weeks did not disintegrate. The fungus filaments 
passed between the fibers, causing the paper to tear apart somewhat 
more readily after the breaking up of the hyphae than similar bits of 
paper kept in distilled water, but microscopic examination of the fibers 
failed to reveal any corroding effects. There was apparently no chemical 
action on the filter paper. 
It might seem from the foregoing facts that pressure rather than en¬ 
zymic action enables the fungus to penetrate the cell walls as described 
for Pythium deharyanum by Hawkins and Harvey (7), but further obser¬ 
vations do not substantiate this means of penetration for Oospora lactis. 
Before a fungous filament can penetrate a cell wall by means of pres¬ 
sure, it must attach itself to the wall, or, if in a cell, to the protoplasm 
in order to prevent pushing itself away from the wall as it elongates. 
Spores of this fungus germinated either in water or in culture solution 
do not attach themselves to the slide or the cover slip. Moreover, when 
germinated in cells of tomato fruit tissue they do not adhere to the wall 
or the protoplasm. When the tip of such a sporeling comes into contact 
with the wall, its more or less continuous growth in length usually pushes 
it aside, which causes it to slide along the wall. Not infrequently the 
position of the whole filament is thus changed, as well as the position of 
other sporelings lying in contact with it. In fact, such a filament may 
even shift its position in such a way as to remove its tip some little dis¬ 
tance from the wall. Such short filaments go through the walls more 
easily at the corners of the cell because there is less chance to slide along 
the wall. When a filament has passed through a wall it pierces other 
walls more rapidly because the anchorage thus obtained holds the grow¬ 
ing tip against a single point better than does the free spore end of a 
germ tube that has no anchorage. 
The phenomena accompanying the penetration of a cell wall by a 
germ tube of this fungus throw some light on the means by which it is 
accomplished. By placing spores of the fungus on the top of thin sec¬ 
tions of tomato fruit tissue mounted and covered on a glass slide and 
furnished with a constant supply of water, the growth activities of the 
