118 BOTANICAL GAZETTE [AUGUST 
sedge rises and falls with it, and there is little variation during 
the growing season. 
The other zones show a gradual lowering of the water table, 
beginning quite rapidly June 8 and continuing until July 3. At 
this time a heavy rain fell, raising the water level sharply in all 
zones. After this there was a rapid lowering of its position in all 
zones until the close of measurements, except in the bog shrub; 
this showed a slight rise. 
The greatest variation, as has been said, was in the marginal 
zone. On April 20 the water was 7.2 inches (18 cm.) above the 
surface of the peat. This gradually lowered until the water table 
was 38.4 inches (96 cm.) below the surface. A variation of 45.6 
inches (113 cm.) was recorded.? In the maple-poplar zone the 
variation was 18.4 inches (46 cm.); in the tamarack zone, 12.4 
inches (31 cm.); in the bog shrub zone, 6.8 inches (17 cm.). These 
figures show that the loose peat acts as a dam, holding the open 
water in the lake from flowing back to the outer zones. The 
same fact was reported by a former student (14) at the small bog 
near Carpenter’s Corner. Here a central area was found with 
the characteristic bog flora of this region, while the greater part 
of the original lake was occupied by a mixed flora, with red maple 
and poplar as the dominant trees. This seemed to be an example 
of the “lagging behind of a xerophytic group of plants in a hydro- 
phytic habitat,’ but borings showed that the water table was 
only 1.4 inches (6 cm.) from the surface. The temperature of 
the soil and character of the peat were the same as generally found 
under such plants. A few rods to the east, under the maples, the 
water table was several feet below the surface. 
An excellent example of the holding back by peat of the water 
in a lake was related to me by a former student, after he had 
examined the above chart. A farmer living near his home had 
a peat bog with a very wide marginal zone and a low shore of con- 
siderable width. During dry years he was able to cultivate this 
ground with good returns, but during wet years he always lost 
his crop. Accordingly, in order to secure continuous use of his 
? In the report in Science N.S. 29: 269, the height of the water above the surface 
should have been added, making a total of 113 cm 
