350 BOTANICAL GAZETTE [MAY 
twigs wére sealed with paraffin immediately after they were removed 
from the tree, so that all escape of water from the tissues must have 
taken place in a manner similar to that which occurs under normal 
conditions when the twigs remain on the tree. Fig. 4 and table 
VIII show the results of this experiment. 
TABLE VIII 
PERCENTAGE OF MOISTURE LOST FROM TWIGS OF TONKA AND ASSINIBOINE WHEN 
EXPOSED TO AN ATMOSPHERE OVER DIFFERENT CONCENTRATIONS OF SULPHURIC 
ACID FOR 28 DAYS 
Percentage loss | Percentage loss sien loss | Percentage loss 
Variety — = —— over H.SO. er H.SO, over H.SQ, 
24.12%) G37 7-45 %) (84.50%) 
ROMEM prs eos os Soe 0.04 4.83 137 9-49 
ASEITOOINE cae. 0.48 3.38 4:37 6.2 
It will be noted that the water loss from the semihardy twigs 
is much greater than from the hardy twigs. With the highest 
concentration of acid used, the loss from the semihardy twigs is 
nearly 9.5 per cent, while that from the hardy twigs is slightly 
over 6 per cent. This tardiness in water movement is in full 
agreement with that occurring in the twigs under normal conditions 
as shown in the graphs of the moisture content curves. It will also 
be observed (fig. 4) that the twigs exposed to a saturated atmosphere 
over distilled water absorbed less than 0.5 per cent of moisture. 
This fact would seem to counter the claims of some workers to the 
effect that there is a considerable exchange of moisture between the 
tissues and the air, and to establish beyond doubt that the moisture 
content of the twigs does not increase markedly with an increase in 
atmospheric humidity. 
order to determine the relative amounts of moisture given 
off from the twigs to the air through evaporation caused by winds, 
twigs of four varieties, including hardy and semihardy forms, were 
removed from the trees and the cut ends immediately sealed with 
paraffin. These twigs were then supported upright in Petri dishes 
by means of paraffin, and after being weighed were placed in a 
strong current of air produced by two large electric fans. The 
dishes containing the twigs were weighed daily, and at the end of 
