Vl TREE PRUNING. 



their ancestors found on this continent, and which 

 they are now too rapidly and surely destroying. 



The advantage of pruning forest trees, in order to 

 increase their yield of timber, was recognized in Ger- 

 many as early as the beginning of the seventeenth 

 century. At first warmly advocated, the practice 

 seems to have been soon very generally abandoned ; 

 and it was not until the writings of de Courval and 

 des Cars, recommending a scientific system based on 

 fundamental laws of vegetable physiology, again 

 called public attention to the importance of the 

 subject, that systematic pruning became a regular 

 operation in all Continental forests. 1 



Their system is based on the fact that, as wood is 

 alone formed by descending, elaborated sap, a wound 



1 The following are the most important works which have been 



published on this subject : 



Grundsdtze der Forst-GEconomie. Moser. 1775. 



Anleitung zur sicheren Erzielung der heimischen und fremden Holzarten. 

 Burgsdorf. 1785. 



Lehrbuchfur Forster. Hartig. 1811. 



Behandlung und Schatzung des Mittelwaldes. Pfeil. 1830. 



Theory and Practice of Horticulture, Chap. XIII. Lindley. 1855. 



Taille et Conduits des Arbres Forestiers. De Courval. 1861. 



L'Elagage des Arbres. Des Cars. 1864. 



Anleitung zum nationellen Betrieb der Ausdstung. Von Muhlen. 1873. 



For stliches Halfsbuch fur Schule und Praxis. Pressler. 1872. 



Schneiden und Ausdsten. Tramnitz. 1873. 



Sdmen und Pflanzen. Burckhard. 1874. 



Das Ausdsten der Waldbdume. Vitus Ratzka. 1874. 



Ueber die Folgen ausseren Verletzungen der Bdume. Goeppert. 1874. 



Notice sur I'Elagage des Arbres, by Martinet. Published by the Admin- 

 istration of the French Forests in connection with the national 

 exhibition of forest products at the Paris Exposition of 1878, a 

 valuable paper to which I am indebted for much information. 



