200 BOTANICAL GAZETTE [SEPTEMBER 
but as it occurred when only one instrument was recording, it may 
be regarded as lacking confirmation, and as it could hardly be a 
critical period on account of the abundant water supply in the soil, 
it is disregarded in the general discussion. Throughout the re- 
mainder of the season the rate is rather high, but not subject to 
great fluctuations. A minimum of about 5 cc. per day is reached 
in September, and is followed by a distinct rise as defoliation pro- 
MAY JUNE JULY AUGUST {SEPTEMBER} OCTOBER 
a Ab 
2 = RSA ia ~ 
I ie \\ VAN 
| VAN —) 7 
ne Att \ Ng SSMT/NE 
fi \ } = 
ae 
: N/ 
Fic. 2.—Evaporation rates in the oak dune association at stations nos. 6, 7, and 8. 
gresses. Station no. g (not plotted) gives a somewhat higher rate 
during July, affording a maximum for that month and for the sum- 
mer of 16 cc. per day. The average rate for the whole period is 
10.3 cc. per day. The mean of all stations in the oak dunes is 
used (fig. 4). in comparison with similar graphs from the other asso- 
clations. 
At Millers, Ind., the vegetation exhibits no undisturbed ‘suc- 
cessional stages beyond the oak dune, but 15 miles farther east, 
near the village of Otis, Ind., there is a tract of the climax deciduous 
