462 BOTANICAL GAZETTE [JUNE 
laboratory conditions which simulated the severest conditions 
which could obtain in nature during the winter. 
Experimentation was carried on both with potted plants and 
with cuttings indoors and outdoors. A few of the graphs obtained 
from the data from these experiments are given in figs. 3-6. 
Although they have been selected from the general array of data 
to avoid needless repetition they represent the general conclusions, 
not merely special cases. 
Consideration of 
these data clearly indi- 
cates that the transpira- 
tion of these bog plants 
January 1912. 
1.8. OA ek 2e ee IS 
= aeee 
~ 
-140 
g/hr/100 om? 
120 
Qhamaedaphne calyculata ——— a . 
a a is very low in winter. 
Yeccinium macroca en 
Furthermore, ° with 
scarcely an exception, 
the rate of water loss is 
much greater (2-15 
times) in the evergreen 
ericads than in the leaf- 
less shrubs and trees. 
When the very much 
—_ Snow thane Cy gy Snew Car Seed mre Exposed position of 
Transpiration of Potted Plants Outdoors. the deciduous trees and 
oe most of the deciduous 
dudvonide ene ic aa mS piesa — nese oe 5 
and Vaccinium macrocar pon outdoors in winter. count, the difference in 
the rate of transpiration 
in nature is accentuated. The mere position of the ericads near 
the ground serves to reduce water loss. This same relation holds 
among the ericads themselves, namely, that the greater the rate 
of transpiration under given conditions, the more protected is the 
position in which that species grows. For example, Chamaedaphne 
transpires at a lower rate than Andromeda and Vaccinium; and 
Chamaedaphne, because of its higher growth, is more exposed. 
Yapp (52) has shown that the nearer the ground in a closed associa- 
tion the lower the evaporating power of the air. 
These data support the well known facts that transpiration 
— mo 
Se OR Ot Semen me 
. 
——<—- 
aa<seer= 
gc tata 
