28 BULLETIN 1727, U. S. DEPARTMENT OF AGRICULTURE. 
entry, or, at least, in conjunction with it, as De Bary (2), Biisgen 
(7), and Miyoshi (30) have concluded for certain parasitic fungi. 
There is no evidence of a cavity in the cell wall, indicating dis- 
tinct solvent action, such as Hasselbring 
found in the barberry (26). Nor was 
any indentation and rupture of the cu- 
ticle discovered, such as Blackman and 
Welsford describe. However, the germ 
pore is very small, and swelling of the 
contents of the appressorium could ex- 
ert considerable pressure on the cuti- 
cle at that 
point lying 
directly be- 
neath the ‘ 
germ pore. | 
Fic, 9.—Cross section of the up- 
per end of a cucumber-fruit 
This is su o- Fig. 8.—Cross section of the outer wall epidermal cell, showing pene- 
5 of a leaf epidermal cell, showing trationfrom an appressorium, 
ges ted in swelling under an appressorium ac- two weeks after inoculation. 
fi eure 1 0, companied by retention of safranin Retention of thesafranin stain 
. stain, 65 hours after inoculation. No is shown in the inner wall 
a case 1n penetration tube is visible. (Camera- layer under the appressorium. 
whic h qi b e lucida drawing; magnified about 1,300 (Camera-lucida drawing; mag- 
times. ) nified about 540 times.) 
ap presso- | 
rium has apparently forced itself loose. In figure 6 the palisade 
cell wall is clearly seen to be indented by the pressure of the 
hyphal tip. On the other hand, the swelling of the wall under an 
apparently unbroken cuticle has been noted (fig. 8), and swelling of 
an area of the palisade cell wall about the point 
in contact with the fungus is also evident in 
figure 6. ! 
To summarize, penetration takes place di- 
rectly through the cuticle from appressoria in 
close contact with the latter and provided with 
Fig. 10.—Cross section of the g small round germ pore. The exact method 
outer wall of a leaf epidermal i 2 B 
cell, showing an appressorium Of cuticle penetration has not been determined. 
apparently forced off by pres- 
, sure exerted by the penetration EFFECT ON INVADED CELLS. 
tube, 121 hours after inocula- 
tion. (Camera-lucida drawing; In the leaf sections from material fixed 121 
magnified about 1,300 times. ) 6 : Sohinkewetare : 
hours after inoculation incipient lesions are 
found to be characterized by marked shrinkage and collapse of the 
epidermal and palisade cells. These cells stain deeply with the heema- 
toxylin. The mycelium is almost entirely intracellular Gres tc) in 
some cases the appressorium from which infection occurred is still to 
be seen (fig. 11). In sections of a stem lesion collapse of the collen- 
chyma cells is plainly visible. In razor sections of diseased stems and 
