PERIODICAL LITERATURE 



SOIL, WATER, AND CLIMATE 



Weaver and Mogensen of the University of 

 Transpiration Nebraska have studied the transpiration rates of 

 of Tree forest seedlings with the purpose, as they state. 



Seedlings "of obtaining data on the relative losses in sum- 



mer and winter of conifers and broad-leaves, and 

 also to make a beginning on the problem of winter killing of trees 

 and shrubs." 



The tests comprise 6 species of conifers represented by 70 indi- 

 viduals, and 3 species of broad-leaves represented 30 individuals. The 

 plants were grown in galvanized iron pots sealed with a mixture of 

 paraffin and petrolatum. In order to maintain natural temperature 

 conditions, the pots were placed inside of slightly larger pots or 

 "collars" sunken in the soil and covered with heavy woolen blankets 

 which were in turn covered with waterproofed muslin. Leaf areas 

 were determined for conifers as well as broadleaves. 



During the mid-summer period, July 20- August 15, the broadleaved 

 seedlings transpired about twice as fast as the conifers ; but during the 

 autumn, September 24-October 10, there was no appreciable difiference. 

 All species showed a steady decline with the approach of winter until 

 in mid-winter the loss per plant for an entire month was, in most 

 cases, less than a gram. Table 2 gives the total loss for western yellow 

 pine by periods during winter and spring and Table 9. gives the com- 

 parative loss for different species in autumn. 



Table 2. — Total amount (in gm.) of zt'ater trati'Spired by j-ycar-old yellow 

 pines from January i to May 2, igiS. 



638 



