TRANSPIRATION OF SILPHIUM 



325 



Evaporiiiieter No. T was at a height of 25 cm., evapormieter 

 No. 11 at a height of G cm. The anemometer was at a height of 

 54 cm. The evaporimeter at the greater height lost the greater 

 amount of water. Both instruments showed a maximum loss 

 an hour before relative humidity was lowest. 



In this experiment two leaves showed the greatest loss before 

 the time of greatest kjss by the evaporimeters and two of them 

 after. . In this experiment the loss of water by the leaves did not 

 run the same as in the experiments where the leaves were not 

 covered with vaseline. Taking the lowest leaf as 100%, the 

 loss of the other leaves was 98.2%, 125.8%o, and 88.2%). In- 

 stead of the second leaf losing the greatest amount it lost next 

 to the least. By comparing these figures with those of other 

 experiments it becomes very evident that there is a difference 

 in the rate of transpiration from the upper and lower surfaces 

 of the leaf of Silyhium. In a leaf which assumes a more nearly 

 horizontal position the difference would probably be much 

 greater. In the graphs for this experiment (f g. 9, fig. 10) the 

 leaves are numbered in order from the lowest to the highest. 

 The evaporimeters are numbered in order from the lower to the 

 higher. 



In table 10 are given the total transpiration results for two 

 experiments wdth Silphium leaves, part of which had vaseline 

 on the upper and part on the lower surface. In these experiments 

 the leaves were taken from the same height from different plants. 

 The loss here given is on the basis of 100 sq. cm. of surface. In 

 both of these experiments the leaf with the vaseline on the lower 

 surface lost the least. 



TABLE 10 



Transpiration (in grams 100 sq. cm.) from the upper or lower surfaces of leaves of 

 Silphium taken from different heights and coated with vaseline. 1912 



THE PI.AXT WOULD, VOL. 17, Nl). 11, ':/14 



