I04 Forestry Quarterly. 



have the power of fixing free nitrogen than the contrary. Yet 

 it is only fair to say that the tendency of the later investiga- 

 tions with their improved methods of experimentation is towards 

 conclusions like that of the present investigator. 



C. D. H. 

 The Botanical Gazette, October, 1913, pp. 249-305. 



A scholarly study by Forstmeister Wag- 

 Solar Energy ner of Pommerania of the power of the 

 in the sun in the forest, deserves more than the 



Forest. brief mention which can here be given. 



Wagner starts out by showing the import- 

 ant role which solar-energy plays in the growth of forests. This 

 energy he seeks to determine quantitatively and qualitatively ; 

 which, from the standpoint of silviculture has never heretofore 

 been done. 



Of course, the solar energy on unshaded areas has been deter- 

 mined. Wagner sums up the data along these lines and then, 

 from the standpoint of solar energy directs his inquiry along 

 four main lines: 



I. The influence of latitude upon crown formation, volume 

 production, number of trees, basal areas and branch formation. 



II. The extent of sim rays in the forest, with special reference 

 to Border Cuttings (Blenderaumschlage.) 



III. The absorption of solar energy in the green leaf and its 

 relation to site and to volume production. 



IV. The measurement of light in the forest; results and prac- 

 tical importance. 



Much of what Wagner writes about is of a physico-chemical 

 character and yet it all has its direct application in practical for- 

 est management. For example, his studies show that a pure 

 stand of 130 year old oaks, "closed," and with the crowns al- 

 most touching each other, passes half of the red light waves, 

 on which, he has previously shown, growth energy chiefly de- 

 pends. Poor soil conditions are evidenced by the presence of 

 short light waves under the crowns. From this Wagner con- 

 cludes that under the north German solar conditions, (pure 

 stands of oak involve an unjustifiable waste of solar energy and 



