84 MANUAL OF FRUIT DISEASES 
flesh of the diseased portion becomes light-brown, the surface 
depressed, and the texture dry and leathery. Within the 
affected area the fruiting pustules of the pathogene develop 
in concentric circles; finally they split open, exposing the 
creamy substance as described for the canker. 
No variety is wholly immune to the disease and some are 
nearly ruined by it. While it would appear that certain 
varieties are generally more susceptible than others, the degree 
of susceptibility varies considerably in different orchards of 
the same variety, and in different trees of the same variety in 
any given orchard. The evidence indicates that the kind of 
soil has little to do with susceptibility. Some hold that the 
Baldwin, Spitzenberg and Jonathan are most commonly at- 
tacked, and that the Newtown, Rhode Island and Gravenstein 
are somewhat less susceptible. Those showing less tendency 
to be affected are the Ben Davis, Northern Spy, Winesap, 
Tompkins King and Hubbardston. 
Cause of anthracnose. 
The apple-tree anthracnose is caused by the fungus Neofabrea 
Malicorticts. In its structure and habits it is very similar to 
the fungus Pseudopeziza Ribis Kleb., which causes the currant- 
anthracnose. It spends the winter as almost inactive myce- 
lium in the cankers. In the spring the fungus renews activities 
for a short period, but usually stops its further spread as soon 
as the cambium becomes active. In midsummer those cankers 
which were initiated the previous fall form acervuli (Fig. 23, 
extreme left). With the advent of the autumn rains the 
acervuli become active, the conidia oozing forth in a creamy, 
gelatinous mass. On being dried by the wind the conidia are 
carried to other limbs and to fruits. With the return of the 
rains the conidial masses again ooze out, and the process of 
dissemination is repeated. In many cases conidia are doubt- 
less washed by the rain to points below the cankers. In general 
the conditions prevailing from October to December are very 
