Periodical Literature 547 



under winter conditions, through the absorption of radiant energy 

 maintained a temperature from 2 degrees to 10 degrees centi- 

 grade higher than the surrounding air. The maximum obtained 

 under brilhant illumination with a light breeze was 8.8° C. When 

 the leaves were protected from air currents, a differential tem- 

 perature of 10.3° C. was obtained. Even diffuse light, according 

 to its brightness, will increase the temperature from 0.5° to 2° C. 

 For February, the coldest month in the year, the average differ- 

 ential temperature between leaf and air — 650 readings in ail 

 taken between the hours of 8 a. m. and 3 p. m. under all kinds 

 of weather conditions — was 3.06° C. It is to be noted that these 

 differential temperatures are those of the leaf as a whole and 

 not necessarily those of the chloroplasts. It is the chloroplasts 

 that absorb most of the radiant energy; the temperature of the 

 leaf is due to radiation and conduction from the chloroplasts. 

 It is entirely probable, therefore, that the chloroplasts, the seat 

 of the food manufacture, have a temperature considerably higher 

 than that of the leaf as a whole. 



In the leaves of the Austrian pine, starch remained abundant 

 throughout October and November, but no conclusive evidence 

 of starch formation was found after December 13th. It does 

 not follow, however, that all photosynthetic activity had ceased. 

 Carbohydrates may have been formed and used or translocated 

 as fast as formed. It merely indicates that photosynthesis was 

 not sufficiently active under the conditions that obtained during 

 January and February to result in production of starch in the 

 leaf. C. D. H. 



American Journal of Botany, January, 1915, pp. 32-70. 



SILVICULTURE, PROTECTION AND EXTENSION 



Under the title of forestal questions of 

 Silviculture the day. Dr. Borgmann, in the Tharandter 



Developed Jahrbuch, discusses the more important de- 



from velopments in science and practice of for- 



Yield Tables estry, as they appear at the beginning of 

 1915, the object being assistance to the prac- 

 titioner. In the present number he begins an analysis of what is 

 known as regards yield and the influencing of it in the various 



