confined to the contact with the wires when the tree is moist. But 

 instances are known in which large trees have been killed by direct 

 current, and several authentic cases are cited. 



In this country every forester is expected to be a general "tree 

 sharp," and here is an opportunity to secure reliable basis for his sharp- 

 ness, which we can unreservedly recommend. 



B. E. F. 



Factors Influencing Transpiration. 



Transpiration as a Factor in Crop Production. By T. A. Kiessel- 

 bach. Agricultural Experiment Station, University of Nebraska, Re- 

 search Bulletin 6. 191 6. 



Hourly Transpiration Rate on Clear Days as Determined by Cyclic 

 Environmental Factors. By L. J. Briggs and H. L. Shantz. Journal 

 Agricultural Research, Vol. 5, No. 14, pp. 583-649. 1916. This was 

 not published until after Kiesselbach's work was completed. 



Relative Water Requirements of Plants. By E. J. Briggs and H. E. 

 Shantz. Journal Agricultural Research, Vol. 3, No. i, pp. 1-63. 1914. 



Transpiration is the simplest and most readily measured plant activity 

 reflecting the conditions under which plants grow. It is therefore of 

 great value in studying the effect of environmental factors upon plants, 

 and is one of the means by which we will eventually secure the knowl- 

 edge we require as a basis for forest experiments. Kiesselbach has 

 investigated transpiration and the factors influencing it in a way which 

 is not only suggestive, but gives results of considerable importance. 



The study covers the relation of transpiration to climate, to soil mois- 

 ture, and to soil fertility, as well as the effect upon transpiration pro- 

 duced by growing first in a dry and then a moist atmosphere. Much 

 quantitative, and hence definite, data was obtained under each of these 

 headings. Although the work was done with field crops, chiefly corn, 

 the broader results apply to all vegetation. 



Under the relation of transpiration to climate, Kiesselbach measured 

 the transpiration of good-sized corn plants growing in large cans, while 

 he kept records of evaporation from a free water surface, of tempera- 

 ture, of relative humidity, and of wind velocity. The resulting charts 

 (pp. 98 and 99) show that transpiration paralleled evaporation more 

 closely than any of the other measured factors. Since he did not record 

 the solar radiation, his results are not in disagreement with Briggs and 

 Shantz's conclusion that solar radiation is the primary climatic factor 



