iqiq] 



WEAVER &» MOGENSEN— TRANSPIRATION 



411 



All of the plants died in February, although the needles persisted 

 for a long time. 



The transpiration losses shown in table V are not greatly 

 different in their amount from those of the other conifers. Like- 

 wise they show a gradual decrease as winter approaches, with 

 minimum midwinter losses. All losses recorded are reliable 

 because no readings were taken after the plants showed signs of 

 deterioration. 



TABLE V 



Total losses (in gm.) from a battery of six lodge pole pines from October 18 



TO February ii 



Plant 



I 



2 



3 



4 



S 



6 



r 



November 17- 

 January 4 

 (48 days) 



3-9 

 6.0 



5 

 2 



7 

 II 



January 4- 



February ii 



(38 days) 



0.7 

 0.7 



1.6 

 0.7 

 I . I 

 i.o 



Ulmus americana 



Initial weighings of a battery of 12 white elm trees were made 

 on September 20. These plants were in containers 5 . 5 inches in 

 diameter and 8.5 inches deep. A photograph taken on May i 

 just when the plants were leafing out is shown in fig. 13. 



The leaf areas were determined, as in the case of the other 

 dicotyledons, by means of solio leaf prints. These were made, 

 of course, without removing the leaves from the stems. The areas 

 of the plants whose transpiration losses are shown in fig. 14 were 

 as follows: 



No. 6 



7 

 8 



10.28 sq 



8.57 

 6.56 

 8.97 



. dm. 



No. 10 

 II 

 12 



4.15 sq. dm. 



452 

 5.26 



For the sake of clarity, the losses from the other plants were 

 not recorded in fig. 14. In all cases they were very similar. With 

 the exception of plant no. 12, there is a close agreement between 



