1913] NICHOLS—SUMMER EVAPORATION INTENSITY I5r 
the same interval. As is indicated in the last column, the disparity 
was least in the Western Highland, greatest in the Eastern High- 
land. The fact that, despite this at first sight rather startling 
deficiency in precipitation as compared with evaporation during 
this particular season, plants were still able to maintain the balance 
between absorption and transpiration may be attributed partly 
to the manner in which evaporation is modified by the physical 
structure of various soils, partly to the adequacy of the ground- 
water supply, which in turn is largely dependent on the influx of water 
TABLE II 
MEAN WEEKLY RATES OF RAINFALL AND EVAPORATION DURING THE PERIOD OF 
9 WEEKS FROM JUNE 1 TO AUGUST 3, 1912 







MEAN WEEK RaTIo 
pg tec te MEAN WEEKLY EVAPORATION Ree 
RSLS ALERT a iene anyessee. Fe RAINFALL 
AND EVAP. 
cm. in ce | cm | in ORATION 
Western Highland. . 1.19 0.47 137 1.94 0.76 0.61 
Central Lowland. . . 1.14 0.45 171 2.42 0.95 ©.47 
Eastern Highland . . T.02 0.40 174 2.45 0.96 0.42 
Coastal Region.....| 0.91 0.36 135 1.gI 0.75 0.48 

at times of the year when the effects of evaporation are less pro- 
nounced, and partly to various structural peculiarities of the plants 
themselves by which transpiration is regulated. Nevertheless, the 
marked excess in the rate of evaporation over that of precipitation 
at such a critical period in the life of the plant cannot but make some 
impress on the character of the vegetation. Another interesting fact 
is brought out in this table. As has already been noted, the absolute 
amount of evaporation in the Coastal Region is even lower than 
that in the Western Highland. But taking the ratio between the 
amount of evaporation and that of rainfall as a criterion, it is seen 
that conditions in the Coastal Region approximate more closely 
those in the Central Lowland. Similarly the less mesophytic nature 
of the Eastern Highland is forcibly accentuated. 
It is fully appreciated that too definite conclusions cannot be 
drawn from such a series of experiments conducted for but a single 
Season. It is recognized, furthermore, that it is well-nigh impossible 
to select with certainty in different localities representative sites 
