PEACH SCAB AND ITS CONTROL. 
9 
contrast, the fungal tissue took up the red and orange quite freely, 
while the dividing cells of the cork-forming layers stained a striking 
blue and the normal host cells below a bright 
red. 
Fruit lesions. — In the early stages of fruit 
infection the slender, branching, hyaline, 
septate hyphse of the fungus are found closely 
appressed to the inner walls of the irregular 
surface cells of the host. This early develop- 
ment is most abundant in the minute depres- 
sions about the bases of the hairs, where 
conditions seem to be particularly favorable 
for the development of the parasite (fig. 1). 
As the fungus becomes firmly established, 
conidiophores are produced, while the vege- 
tative hyphse branch and thicken until they 
may entirely cover the area of infection. 
The individual cells thicken and darken, 
while transverse and longitudinal divisions 
take place, often resulting in the formation 
of irregular fungal masses ^.yq or six cells in 
depth (fig. 2, a). This later development, 
too, is particularly abundant in the depres- 
sions about the bases of hairs. 
As the fungus develops generally over the sur- 
face of the infected areas, the superficial host 
cells die and the lesions may be cut off from the 
sound tissues below by the formation of pro- 
tective layers of cork (fig. 2, b). These layers 
are formed as the result of tangential divi- 
sions of the subepi- 
dermal cells. Less 
frequently, trans- 
verse divisions oc- 
cur. Cork forma- 
tion is usually most 
vigorous in the third 
or fourth subepi- 
dermal layers and 
ordinarily extends 
en lruits: a, bnortiy Deiore ,. , - , , 
cork formation; b, soon after cork formation. At the right the section Slightly above and 
extends nearly to the edge of the corky layer. Camera-lucida drawings. beloW this actively 
(Magnified 310 times.) dividing region. 
In the case of early varieties of peaches, the fruits usually mature 
before cork formation occurs. Upon later varieties, however, the 
48408°— Bull. 395—17 2 
Fig. 1.— Section of a lesion from 
an Elberta peach fruit, showing 
the early development of the 
parasite about the base of a 
hair, in close contact with the 
inner walls of adjacent surface 
cells of the host . Camera-lucida 
drawing. (Magnified 465 times.) 
