Periodical Literature 751 



dently to compensate the reduction of the conducting area due to 

 the dead branch knots. An experiment with inserted glass rods, 

 interrupting the Hving wood area produced the same result. 



The mechanical theory of the root collar is denied and a physio- 

 logical explanation substituted, namely the retardation of the 

 transpiration stream due to change of direction which requires an 

 increased conducting area. 



The author does not claim that water conduction is the only 

 influence on stem form and admits that mechanical influences may 

 cooperate, but much more complicated ones, than have hitherto 

 been assumed. For instance, the author could differentiate com- 

 pression and tension influences on diameter growth at night 

 from those in the day time, and show that the reaction to bending 

 is different in different trees. 



The anatomy is always different on the pressure side from that 

 on the tension side, sometimes suppressing formation of vessels, 

 and of wood fibers, the cambiiun making only parenchymatic 

 cells. 



The author concludes that many of the phenomena of life 

 which hitherto have been supposed to be adaptations are mostly 

 direct reactions to present influences ; especially the structtu-e and 

 anatomy of vegetative organs are directly depending on conditions 

 of nutrition. 



Was wissen wir vom Dickenwachstum der Bdume? Schweizerische Zeitschrift 

 fiir Forstwesen, May -June, 1916, pp. 104-17. 



SOIL, WATER AND CLIMATE 



In a most painstaking analysis of the 



Forest problems which confront the water works 



Influences engineer by the variations in precipitation, 



replete with a mass of detail, tabulations, 



maps, curves, and all the means of making for sound argimient, 



Mr. Carl Peter Birkinbine, son of the well known, late, lamented 



John Birkinbine, also incidentally alludes to the relation of forest 



cover to precipitation and run-off, and in the subsequent discussion 



was induced to use the following language: "As to the matter of 



precipitation and run-off being affected by deforestation and 



agriciilttual development, the point brought out in regard to 



precipitation includes two separate ideas. One that the different 



