206 PETRY: VEGETATION OF NEW YorK STATE 
is not clear, but is probably to be found in the accumulation of 
ice in underlying fissures. In the basin itself ice persists in the 
spring about a month after it has disappeared elsewhere. It is 
_ possible that a sufficient amount of ice accumulates in large crev- 
ices or fissures under the loose rock of the basin to maintain the 
low temperatures through the summer season. Some such locali- 
zation of the areas of lowest temperature is indicated by the data 
on soil temperatures given in Fic. 2. 
Fic. 2. Map of plunge basin with isotherms of soil temperatures (Fahr.) at depth 
of 1 inch at noon, September 12, 191 Scale ft. 
In order to determine with exactness the temperature condi- 
tions over the entire bottom of the basin, a system of twenty 
stations, at distances of thirty-five to fifty feet from each other, 
was established; these covered an irregular area extending about 
three hundred feet along the axis of the basin, some ninety feet 
up the south slope and about seventy feet up the northern slope. 
‘Two thermometers were placed at each station, one, completely 
shaded, at one inch from the ground, the other with the center of 
the bulb in the soil to a depth of one inch; after thirty minutes all 
the thermometers were read simultaneously. 
When the temperature data are plotted on a map of the basin, 
isotherms can be drawn to represent the temperature conditions. 
Fic. 1 shows air isotherms representing the conditions existing 
