150 BOTANICAL GAZETTE [AUGUST 
In the foregoing paragraphs no account whatever has been 
taken of the varying amounts of precipitation occurring in differ- 
ent sections of the state. But since the amount of water present 
in the ground and therefore available for plant use is in itself a 
potent factor in determining the character of vegetation, and 
since its abundance is so largely controlled by the amount of pre- 
cipitation, it is necessary, in order to gain a comprehensive view of 
the situation, that the relationship between the phenomena of 
precipitation and evaporation within the area under discussion be 
considered. So far as observed, there is no constant ratio between 
the rate of precipitation and the intensity of evaporation. Thus 
the rate of evaporation during a heavy rain is hardly lower than 
during a dense fog. But the ratio between the amount of precipi- 
tation and that of evaporation, especially over considerable periods 
of time, is of vital significance. In the state of Connecticut there 
is an average annual precipitation of 120.9 cm. (47.59 inches).® 
This is distributed approximately as follows: Western Highland 
(inland), 126.8 cm. (49.94 in.); Central Lowland (inland), 119.6 
cm. (47.08 in.); Eastern Highland (inland), 117.7 cm. (46.35 in.); 
Coastal Region, 116.8 cm. (45.98 in.). Of more special interest, 
however, for the purpose of comparison with the observed rates 
of evaporation, are the amounts of rainfall that occurred in the 
various localities during the past season for the period extending 
from June 1 to August 3. These, together with the contempora- 
neous evaporation records, are therefore indicated in table II. For 
convenience in comparing the two sets of data, the evaporation 
readings, heretofore given in terms of cc., are here expressed in 
units of depth as well, the conversion being made with reference 
to a more or less arbitrarily chosen free water surface. 
An examination of table II shows very convincingly that, for 
the period under observation, nowhere in the state would the 
amount of rainfall have compensated for the amount of water 
which would have been evaporated from a free water surface during 
* Based on records from 14 scattered stations. This and the following figures 
regarding precipitation have been computed from statistics published in the Monthly 
Weather Review of various dates, 
® The standard water surface on which these reductions are based is that used by 
Livincston (see Plant World 143214, 215. 1911). 
