ANTHRACNOSE OF CUCURBITS. DF, 
In some cases of delayed or, perhaps, inhibited penetration, there is 
a swelling and: change of staiming reaction of the cell wall under the 
appressorium, characterized 
by retention of the safranin 
in the triple stain (fig. 8). 
The mode of fruit penetra- 
tion appears to be somewhat 
similar. Sections from fixa- 
tions made two weeks after 
inoculation show numerous 
Fig. 6.—Cross section of leaf epidermis and pan- 
sade tissue, showing penetration of a stomatal 
guard cell from an appressorium, emergence of 
Fia. 5.—Cross section through a stoma, show- penetration tube intosubstomatal chamber, and 
ing an appressorium formed directly with- indentation of palisade cell by the swollen tip of 
in the stomatal pore. Penetration of a the tube. The wallof the palisade cell is swollen 
guard cell has occurred, 65 hours after in- and retains safranin in the area in contact with 
oculation. (Camera-lucida drawing; mag- the fungus; 65 hoursafter inoculation. (Camera- 
nified about 1,300 times.) lucida drawing; magnified about 570 times.) 
examples of direct penetration of the cuticle and thick outer 
wall, but no cases of subsequent mycelial development. In view 
of this fact, it seems likely that these are abortive or inhibited 
penétrations. Fruit penetration is iulustrated in figure 9. Here 
the penetration tube is not 
as clearly distinguishable as 
in the leaf sections, and only 
the swollen tip is to be seen. 
There is indication of a 
splitting apart of the wall 
‘layers in some cases, and all 
cases are characterized by 
a marked retention of the 
CaN safranin in the inner wall 
Fic. 7.—Cross section of leaf epidermis, showing penetration 
of an epidermal cell, 121 hours after inoculation. The con- layer under the appresso- 
tents of the appressorium have apparently passed into the yjym (fie. 9) i 
penetration tube. Mycelial growth has begun from the 2 
swollen tip of the latter. Division of the host nucleus has The exact method of 
occurred as a result of the fungous invasion. (Camera- cuticle penetration 1s not 
lucida drawing; magnified about 615 times.) ‘ 
| yet understood. It is not 
known whether the penetration of the cuticle proper is due to 
mechanical pressure alone, as Blackman and Welsford (6) find in 
Botrytis, or whether there is some softening in advance of actual 
