282 Forestry Quarterly. 



the conifers, spruce and fir, the latter forming a much larger 

 part of the natural regeneration, besides being planted in fail 

 places. 



To make the forest resistent to the attacks of an organic na- 

 ture must be the aim of the forester. This according to Meister, 

 where snowbreakage is to be feared, can be done by the mixed 

 forest which shows a greater variation in the form of the crown- 

 cover, by longer regeneration periods, and especially by the se- 

 lection forest which assures the existence of the single species 

 as well as of the forest formation. 



Aphorismen zur Biologic des Waldes. Schweizerische Zeitschrift fiir 



Forstwesen. March, 1912. Pp. 77-87. 



It is well-known that the wood of these 

 Wood two genera is difficult to distinguish. 



Structure Prof. Burgerstein uses for diagnosis the 



of structure of the pith rays, which in 



Populus both woods consist of two kinds of cells, 



and namely one set radially longest without 



Salix pits, the other set vertically longest and on 



their radial wall towards adjoining ves- 

 sels beset with large round pits. 



In Populus the relation between the average height of the 

 pitted pith ray cells (//) and the average height of the unpitted 

 cells {h), i. e. //: h lies between 1.2 and 1.55, while in Salix 

 this relation lies between 1.85 and 2.1, that is to say the height 

 of the unpitted cells is relatively smaller than those in Populus. 

 Moreover, the pits on the radial cell walls occur in Populus in 

 2 to 3 (in root- wood occasionally 4) rows, while in Salix in 

 2 to 10, mostly 4 to 6 rows. 



Diagnostische Merkmale der Markstrahlen von Populus und Salix, 

 Centralblatt f. d. g. Forstwesen. March, 1912. Pp. 150, 151. 



Fankhauser reports on a phenomenon. 

 Heat observed in a number of localities of 



Splits Switzerland and Belgium during the un- 



usually dry summer of 1910, which in its 

 results resembles frost splits. So far as known spruce only has 

 suffered. In a 15-25 year plantation of very rapidly growing 

 trees longitudinal (not spiral) splits of considerable length and 



