1911] DACHNOWSKI—CRANBERRY ISLAND 143 
instrument extended uninterruptedly to October 2. During the 
writer’s absence in Europe, the readings in the two plant zones 
were recorded by Mr. Dickey; they have since appeared in pub- 
lished form (12). It is not necessary to reproduce in detail the 
original observations for the entire period. A series of data from 
the observations made have been summarized here and the con- 
clusions stated. 
Following are the atmometer readings for the several habitats, 
together with the comparative evaporation expressed in percentage 
of the standard instrument (table VII). 
TABLE VII 
ATMOMETER READINGS FOR STATIONS ON CRANBERRY ISLAND AND THE 
UNIVERSITY CAMPUS 
Central, 
i i - . aple-alder : 
suse ae a s oo poe, ne Percent. diff. M — Percent. diff. 
zone 
May 28) 118-8 cc. OF CC. 81.6 90,5 66. 65.7 
PP nets ccna ee I10.9 7a | 83 60.5 54-5 
JUue 43.550 88.1 6354 60.5 27.5 ai .2 
Fi “ns wrecks ending July 
tite een Ue Os 87 349.2 91.7 290.4 59.6 
Tae oe July 24. 151.4 120.2 79.3 
et 7.8 9.8 59.2 50.6 42.9 
ee . BBO E conan alt tae 140.6 69.8 49.6 36:3 25:6 
AGhs Ta eee 134.6 82.4 61:2 70.4 $2.5 
Total evaporation... . .|1349.2 933-8 69.2 690.8 eee 
As was to be expected, by far the smaller part of the total 
evaporation on Cranberry Island occurred in the maple-alder 
zone. The annual evaporation within the maple-alder zone is 
now about three-fourths of that in the open central zone, that is, 
fully 25 per cent of the moisture is saved by shade-producing trees 
and shrubs. The evaporation within this zone is greatest in the 
season from October to May. The difference in evaporation 
between this zone and the central zone is then at a minimum, but 
later it follows closely the growth of the leaves in the early spring 
and their fall in autumn. The maximum difference occurs in 
June and July. As the seasons advance, the evaporating power 
of the air in the forested zone varies with precipitation. Wind 
