47^ Forestry Quarterly. 



planting light plants of some age are to be avoided, although i 

 to 3 year olds from seedbeds, as stated before, may be used in 

 any condition, while transplants that are to be used after several 

 years should be grown under conditions similar to those in re- 

 gard to light as they are to be used in. 



Untersuchungen iiber den Blattausbruch und das sonstige Verhalten von 

 Schatten- und LichtpAanzen der Buche und einiger andrer Laubholzer. 



Mitteilungen der schweizerischen Centralanstalt fiir das forstliche Ver- 

 suchswesen, 191 1. Banx, pp. 107-175. 



Professor von Schermbeek publishes a con- 



IVater tribution to the explanation of water move- 



Movement ment in trees, based in part on older theo- 



in ries, in part on manometric measurements 



Trees. of his own on live and dead wood. He 



concludes : 



1. The cause of the ascent of water in the living tree is caused 

 by a difference in pressures (deficit) which is provoked in a 

 higher part of the tree trunk relatively poorer in water as long 

 as a lower part can still enrich the cell walls of its tissues with 

 water by imbibition. 



2. The degree of volume increase of the imbibing tissue is 

 determined by the ion contents (i. e. amount of soluble salts) of 

 the imbibed water. 



3. Transpiration and assimilation maintain the necessary dif- 

 ference in the relative water contents of the neighboring higher 

 and lower parts. 



4. Conducting vessels can be supplied with water from their 

 cell walls. When these organs come under the influence of this 

 pressure difference, an accelerated movement of water sets in, 

 provided, that the eventually present gaseous substances are 

 absorbd by the imbibed water. 



5. The imbibition proceeds fully only as long as the colloidal 

 cell wall substance is still capable of swelling. 



6. If this is not the case, then a part of the trunk can secure 

 its water only by conduction, equal volumes of gas and water 

 being exchanged. 



7. The conduction is the slower, the greater the resistance 

 which is opposed to the movement of gases. Hence the water 

 absorption in a slowly dying part is smaller in a given time than 

 in a killed part by destruction of tissues. 



