iqiqI 



WEAVER &• MOGENSEN— TRANSPIRATION 



409 



Picea Engelmanni 



This battery consisted of eight 3-year-old Engelmann spruce 

 seedhngs grown in containers 3 . 5 inches in diameter by 6 . 5 inches 

 in depth, and in soil with available moisture ranging from 1 1 . 3 to 

 15 .1 per cent. 



Although the leaves dropped off badly during late December 

 and in January, none of the plants died. All put forth a vigorous 

 growth of new leaves during April and May of the following spring. 

 Three of these trees, photographed in February, are shown in fig. 1 1 . 



Fig. II. — Three 3-year-old Engelmann spruces, three 2-year-old white firs, and 

 one Douglas fir, all more or less defoliated; photograph taken February 28, 1918. 



The leaf areas of three plants, calculated at the time the leaves 

 had just begun to fall, were 2.78, 3.91, and 5.87 sq. dm. respec- 

 tively. These areas were determined while the leaves were still 

 intact by counting their total number, measuring the length and 

 average diameter of each leaf, and then calculating the area of the 

 four sides. The graphs giving the transpiration losses are shown 

 in fig. 9. A comparison of the water losses from these plants with 

 those of other conifers shows a remarkable similarity. 



Pseudotsuga mucronata 



Because of high mortality among the Douglas firs during the 

 reestablishment in pots in early summer, only three 3-year-old 

 seedlings were available for experimental work in September, 

 These were placed in containers 3 . 5 inches in diameter by 8 inches 



