APPLE DISEASES 93 
sort on the surface of an apple, it germinates and its mycelium 
proceeds to feed on the ripe fruit. Among the common types of 
wounds through which P. expansum gains entrance may be 
noted, finger-nail cuts, bruises, worm-holes, scab spots, and 
spray-injured places. The fact that the soft-rot fungus gains 
entrance to the apple through such injuries is highly important 
in the matter of controlling the disease. It is further worthy 
of attention in this connection that this pathogene cannot 
enter normal, unbroken skin. Accordingly it will be learned on 
observation that in barreled apples of a good quality those fruits 
at the heads of the barrel are rotted more extensively than 
those in the center of the barrel. 
Like many fungi, P. erpansum develops an extensive system 
of mycelium in the lesion. From the germtube, hyphe grow 
in all directions into the flesh. The threads dissolve their way 
between the cells of the fruit-pulp, as a result of which the latter 
are easily pushed out of position. They slip over each other at 
the slightest pressure.“ Thus when the surface of a rotted area 
is pressed by the finger the tissue quickly and easily gives 
way, offering no resistance whatever. The disease is well 
named soft-rot. As already mentioned, under conditions of 
high relative humidity greenish cushions or pustules appear 
on the surface of the affected area. These are tufts of fruiting 
stalks of the fungus which arise from the mycelium within. 
Numerous hyphe grow in erect fashion at the same point; 
their general arrangement is not unlike that of an inverted 
broom without the handle. The tips of these hyphe, or 
conidiophores, become branched in a digitate fashion, and at 
the end of each stalk is developed a chain of spores, or conidia. 
The number of conidia which might be produced on the surface 
of a single rotten apple would aggregate millions. As soon as 
mature these spores are easily broken from the conidiophore 
and, being extremely light in weight, float about in the air for 
some time. 
