468 BOTANICAL GAZETTE [JUNE 
TABLE IV 
CHAMAEDAPHNE CALYCULATA 
February 27 March 1 March 3 March 5 
Laboratory (room temp.) Seat ee 028025 =0.028\0- 43 =0. 01 
aboratory it ee 73 7 =< MOE Sas ised cee 
Laboratory (sol. freezing) . . |2-°5?=0.027 2-08" =0.023 ee 0.060=9 024 
a. 2.3 5 
Radiator (rad. temp.)...... 0: TT = 0.038 ae =o. RE fs is Ca ice os day ees 
2. 
Radiator (sol. freezing)... et <3 <0, 029 0.619 5 eG, eS Pama ea 
2. 
Outdoors (sol. frozen)...... ms 0-010 _ 5 99919927 9 o09'9:9°3 9.004 Se Oe 
0.5 0.8 0.7 
To obtain the factor in table IV, the average of the values of all 
specimens under the same conditions during a day was used as a unit. 
The rate of transpiration was divided by the rate of conduction. 
The resulting factor expresses the number of grams of transpiration 
per unit area, which is equivalent to 1 cm. of conduction. Wi 
the solution at a lower temperature in one of two simultaneous 
sets, but the evaporating power of the air the same, it takes 
smaller amount of transpiration to account for 1 cm. of conduction. 
Utilizing the high temperature of the steam radiator in the 
laboratory, it was found that a much greater (2-4 times) amount 
of water loss occurred in proportion to the amount of conduction 
in plants kept in solutions at the radiator temperature than near 
freezing. The temperature of the radiator exceeded the death 
point of the plants and was far above any temperature that their 
roots are ever subjected to in nature. 
Plants maintained in solutions near the freezing point in the 
extreme evaporating condition of the air above the radiator, a 
condition which is more severe, with respect both to summer heat 
and to summer soil water temperatures, than any ever expe- 
rienced by Chamaedaphne in its natural habitat, exhibited a higher 
transpiration and a higher rate of conduction than plants kept in 
the room at both room and freezing temperatures. This was in 
spite of the cold solution. A comparison of the transpiration- 
conduction factor of plants in freezing solutions in the room and over 
the radiator shows scarcely any difference. 
