268 BOTANICAL GAZETTE [octoper 
3. THE sorts.—The distribution of surface soils is important 
because of the relations existing between soil types and plant societies. 
The floodplain, while having areas of peaty earth about the center 
and between the ponds and bluff, with an outwash of sand at the 
northwest and southeast, is fundamentally of compact till, which 
underlies the whole region and frequently appears elsewhere at the 
surface. The east bluffs are more porous, being composed of gravel 
or sand. A long ridge of mineral soil reaches from the northwest, 
forming a low barrier along the stream to the marsh about 
e the bay, where it is bordered by peat-like earth. Humus 
“1 is present everywhere except on the washed slopes of the 
Pee bluffs. At the east is a line 600 feet in length, 
Mis Gar xe following the base of the cemetery bluff, where 
a > sand borders the till below with the 
“x sharpness of exposed strata. A profile 
was made through B (map), shown in 
fig. 3, which further explains this 
peculiarity in the structure of the 
Ss 
Fic. 3.—Profile through B, map, showing influence of plant associations In pre- 
venting the outwash of soil, and in the formation of beds of peat; A, black oak; = 
black locust; C, yellow oak (Quercus acuminata); D, bur oak; 5S, seepage — 
E, shrubs (Betula pumila); scale 60 feet to the inch. 
bluff. The sand or gravel-capped bluff, with seepage springs along 
its soil line, and with its structure plainly revealed by the plant 
societies which inhabit its slope, occurs commonly in the valley. — 
4. SOIL WATER.—The conditions of soil moisture, as influenced 46 
varying soils and differences of elevation, have an obvious sae 
bearing upon the distribution of plant societies. Conditions : 
extreme dryness are to be found in places along the brink of the 
steeper bluffs, where the combined effects are felt from the age 
nature of the soil, elevation, and exposure to drying effects of wi 
and heat. More soil moisture is found on descending the — 
and the change may be abrupt along soil lines where seepage springs 
occur. There is a slow but constant flow and percolation of spring 
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