402 



BOTANICAL GAZETTE 



[DECEMBER 



weather (the mean monthly temperature of January being only 

 12.6" F.) gave total maximum losses for the entire period of 37 

 days of only 2 . 5 gm. The average total loss during this time was 

 about I gm. It is surprising how an area of 3-6 sq. dm. of leaf 

 surface can be exposed with such minimum losses. The daily 

 losses, compared with those from the same plants during the period 

 September 24 to October 11, are only 1/25 1 as great. The average 

 losses during succeeding intervals are shown in table II. 



TABLE II 



Total amoxhsit (in gm.) of water transpired by 3-year-old yellow pines from 



January i to May 2, 1918 



A general but slow rise during the cold month of April may be 

 noted, with a sharp increase following the milder weather in May. 

 The transpiring area throughout is practically constant, since little 

 growth occurred before May i. On April 3 the stomata were found 

 to be open. 



Initial weighings from a battery of five 2-year-old yellow pines, 

 each in a 4X 9-inch container, were obtained on October 18. Two 

 of these plants are shown in fig. 12. Table III gives the total losses 

 during the several periods. 



On December 19 the leaves were falling so badly that all but 

 two plants were discarded, but the following spring all put out 

 new leaves. 



The exceedingly low water losses during the period December 

 19 to March 13 correspond with those found for the other battery 

 of older yellow pines; in fact, this was found to be the case with 

 all of the conifers. Table III shows an increase in the transpiring 



