464 BOTANICAL GAZETTE [yoNE 
the means employed. The advantage of the deciduous habit in 
reducing transpiration in the winter is apparent. 
Per unit area of leafless twig surface, bog shrubs lose less water 
than do the bog trees under the conditions of these experiments. 
Furthermore, bog shrubs are more subject to winter killing in a 
severe winter in this latitude unless protected by snow. This 
would seem to indicate that the xerophytism of the bog trees was 
in general more efficient 
=e 1912, Feb.1911 than that of the bog 
hen Shay ieee = u fis shrubs under extreme 
pe easel ts winter conditions, or 
that their means of 
water renewal was more 
efficient. 
.006 
wes ALS During stormy 
— Aacer weather it is difficult to 
oo2 / : 
: Betula ace allow a real exposure to 
ta? ? a 
nd me Nendpanthes.| the weather and then be 
Temperature i 
nie able to measure transpi- 
-10° ration by weighing, but 
100% Rel. Humidity, Transpiration of repeatedly, even when 
vo Outtings : 
50% a ag preparations were 
shielded from the rain 
Fic. 6.—Transpiration of cuttings of Acer OF Snow, measurement 
rubrum, Betula pumila, Cephalanthus eieomed showed an increase in 
Chnieanndothee calyculata, Larix laricina, and Nem tote b thet ok 
panthes mucronata outdoors in winter. hibass eyond that o 
a control. This was 
noticed particularly in Chamaedaphne and Andromeda, whose 
leaves were covered beneath with scales and hairs, respectively. 
This absorption helps replenish the saturation deficit of the leaves, 
and so in a measure alleviates the demands upon the root system 
at a time of year when absorption is at best difficult. It is not 
certain, however, whether this water absorbed from the air ever 
actually penetrates to the mesophyll. 
Influence of solution temperature upon transpiration 
To determine the influence of the temperature of the solution 
from which the cutting was taking water upon the rate of tran- 
