STEVENS: PREVALENCE OF ENDOTHIA GYROSA 141 
the south erosion is worse than in other sections of the country 
and suggests that “‘it is probable that the climate has much to do 
with the fact that erosion is so rapid in the south. The character 
of the soil makes a marked difference in the rates of erosion under 
the same climatic conditions.”’ 
SNOW-COVER 
The abundant rainfall of the southern states, already referred 
to, no doubt greatly increases erosion. Perhaps equally important 
is the amount of snowfall, or rather the persistence of snow-cover, 
since the longer the period during which the ground is covered 
with snow, the shorter the period of soil erosion. 
The snowfall data of the U. S. Weather Bureau are not so 
arranged as to show readily the period each year for which the 
ground is covered with snow in any given locality. Recently, 
however, Brooks published a discussion (1) of the snowfall of 
the eastern United States in which he reviewed the previous work 
on the subject and summarized the available data. Brooks also 
maps the average snowfall for each month, the average annual 
snowfall in inches,-and the average annual number of snowfall 
days in the eastern United States. From these maps it is possible 
to get a fairly good idea of the duration of snow-cover in various 
parts of the region under consideration. 
While the total amount of snowfall does not necessarily corre- 
spond with duration of snow-cover, in general those regions which 
have most snow have the longest periods of frozen and snow covered 
ground, and the shortest periods in which erosion is possible. 
Certainly soil in the region which has an average of over twenty 
inches annual snowfall and one inch as early as November is more 
protected than that south of this region. Longer snow-cover 
alone would greatly reduce the amount of erosion in the northern 
states as compared with that in the south. Greater erosion means 
necessarily more exposed roots and consequently more frequent 
opportunity for infection with E. gyrosa. 
CULTURAL CONDITIONS 
The contrast between the cultural conditions of the north 
and south has been frequently noted (4, 9). The relation of cul- 
