Roots and its Influence on the Ecesis of Plants in Swamps, 1 9 
The reduced rate, then, is not to be explained by lower temperature and 
higher humidity. After two days of the reduced rate of transpiration, the 
leaves began to turn yellow. From this time the average transpiration rate 
dropped still lower until at the end of ten days after the roots had been 
submerged the transpiration rate per day averaged 7-3 grm. for one plant, 
and 9 grm. for the other. This average rate was maintained three days, at 
which time the plants began to shed their leaves. In the nine days follow- 
ing, in which weighings were continued, the average daily rate of transpira- 
tion was reduced to 2-8 grm. for one plant, and 1-5 grm. for the other. It 
is to be observed that when the roots of plants had been submerged 
a decrease in the average daily rate of transpiration soon 'followed. It is to 
be noted, further, that this decreased average daily rate of transpiration 
Fig. 2. Comparative transpiration of two seedlings of Quercus macrocarpa. The dotted line 
represents a plant in moist soil, the line of long dashes a plant in submerged soil. Leaf area oi 
former, 100 sq. cm. ; of the latter, 64*27 sq. cm. The line of short dashes represents the rate of 
transpiration of the plant with the smaller leaf area based on 100 sq. cm. leaf surface ; the heavy 
solid line represents the transpiration rate of the plant with 100 sq. cm. leaf area based on the same 
leaf area as the plant in submerged soil. 
continued two or more days before the manifestation of any evidence of 
injury to the plant. These facts indicate clearly that transpiration is greater 
than absorption. The shedding of leaves is to be regarded as a compensa- 
tion for the reduced ability to absorb by reduction of the transpiration 
surface. 
Two seedlings of Quercus macrocarpa were potted in garden soil in 
aluminium pots. The roots of one were submerged, while the other was 
allowed to grow in moist soil. The pots were covered with rubber tissue to 
prevent surface evaporation, and weighings made. The results are shown in 
the accompanying graph (Fig. 2). 
The plant with the roots in moist soil had a leaf area of 100 sq. cm., 
and the plant with submerged roots had a leaf area of 64-27 sq. cm. In 
