APPLE DISEASES 11 
its food from the cuticle, water is drawn from adjacent cells as 
evidenced by the one-sidedness of affected apples and in the 
puffing of the leaves under the scab spots. 
The mycelium of the pathogene on the leaves and fruits 
modifies its form slightly by transforming into a stroma, a 
spore-bearing cushion. From this cushion arise spore-stalks, 
conidiophores, which cut successively from the free outer end 
several conidia — asexual summer spores. ‘These conidia. 
mature rapidly and are blown to other leaves and fruits, where 
they produce scab spots just as described for the ascospores. 
From these spots, caused by the growth from the conidia, arise 
again the stromata on which a second crop of conidia are borne. 
These are likewise capable of further spread of the pathogene. 
This process repeats itself throughout the growing-season, 
depending on conditions of moisture. If fruits are inoculated 
just prior to picking, the spots appear in storage; their ap- 
pearance has been described under Symptoms. Fruits which 
fall carry the fungus with them, but the pathogene never devel- 
ops further. Leaves, on the other hand, furnish the chief 
hibernating quarters for the fungus. As soon as the foliage 
falls, the mycelium of the organism penetrates all parts of the 
leaves. During the autumn and early winter the perithecia 
are partially formed, these organs lying dormant until spring. 
‘At this time growth is resumed and the life-cycle is again ini- 
tiated. There is considerable evidence that the conidia hiber- 
nate on the twigs or in the bud-scales, but the old leaves on the 
ground are to be regarded as the chief source of the primary 
inoculum. 
Control of apple-scab. 
The destruction of fallen leaves would appear to lessen the 
primary infection. But in actual practice that method alone 
is not reliable and at best is only to supplement spraying or 
dusting. Spraying is at present the chief method of control. 
The fungicide used is lime-sulfur solution, diluted one gallon 
