SCIENTIFIC PAPEES. 



A DISEASE OF TAXODIUM DISTICHUM KNOWN AS PECKI- 

 NESS, ALSO A SIMILAR DISEASE OF LIBOCEDRUS DECUR- 

 RENS KNOWN AS PIN-ROT.* 



BY HERMANN VON SCHRENK. 

 INTRODUCTION. 



The diseases of forest trees had attracted attention for 

 many years before any attempt was made to arrive at an 

 understanding of their true nature. With the investigations 

 of Th. Hartig, t Schacht,J and Willkomm, a beginning was 

 made, but not until the epoch-making researches of R. 

 Hartig, || were some of the complex relations between 

 diseased trees and the exciting causes made clear. In 

 England, Marshall- Ward has paid some attention to the 

 diseases of trees, but in this country few have given this 

 subject much study. 



A tree may be diseased because of the natural decadence 

 of its vital forces incident to old age, it may be influenced 

 by abnormal physiological conditions, or its functions may 

 be impaired by the activities of a disturbing organism. 



* A thesis presented to the Faculty of Washington University for the 

 degree of Ph. D., April, 1899. 



t Hartig, Th. Abhandlung iiber die Verwandlung der polycotyle- 

 donischen Pflanzenzelle in Pilz u, Schwammgebilde, u. die daraus 

 hevorgehende Faulniss des Holzes. 1833. 



t Schacht, Hermann. Der Baum, Studieu iiber Bau u. Leben der 

 hoheren Gewachse. Berlin. 1860. 



Willkomm, M. Die mikroscopischen Feinde des Waldes. Dresden. 

 1866. 



|| Hartig, R. Wichtige Krankheiten der Waldbaume. Berlin. 1874. 

 Die Zersetzungserscheinungen des Holzes, etc. Berlin. 1878. 



Separates issued June 3, 1899. 1 



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