466 BOTANICAL GAZETTE [JUNE 
transpiration from a colder solution would be caused by the extra 
amount of energy required to warm the colder water up more 
degrees of temperature. In nature these bog plants are subjected 
to these extremes of temperature maintained in the laboratory, 
and this range is well within their physiological ability. 
These experiments were repeated under the very severe condi- 
tions obtaining over a steam radiator. As the temperature of the 
solution became hot, transpiration proceeded at a very rapid rate, 
until the tissue was killed at a temperature of 42-46° C., after which 
the transpiration fell to a low amount without a corresponding 
drop in the evaporating power of the air. The graph obtained by 
plotting the data may be called the death curve. It is similar to 
those obtained by Bose (2) in experimental work on death in plant 
tissues. After the marked drop, the rate of transpiration increases 
and then fluctuates with the evaporating power of the air, but does 
not exhibit the decided increase which the access of sunlight causes 
in living twigs. 
Other twigs maintained in cold water under radiator conditions 
exhibited a higher rate of transpiration than those in the room. 
The average rate of transpiration under these conditions was very 
little in excess of that of twigs in the room with solution at room 
temperature. This clearly shows the retarding influence of cold 
soil water. It also shows the ability which these plants possess 
of withstanding a much severer aerial condition of high temperature 
and low relative humidity than they are ever subjected to in nature. 
Rate of conduction of a 0.5 per cent aqueous solution of 
lithium nitrate 
Table IL summarizes the winter experimentation upon the rate 
of conduction in peat bog plants. 
The results obtained from these experiments were subject to 
considerable variation, but in general the rate of conduction was 
greater from warmer solutions. Plants from habitats where the 
soil temperature is naturally lower seem to have a greater ability 
to conduct water from a colder solution. Transpiration takes place 
faster from a warmer solution. An increase of rate of conduction 
from a warmer solution is just what is to be expected to supply 
the greater demand for water which increased transpiration entails. 
