12 CoIIcfjc of Forcslnj 



1)0011 done tdWiird the studv of tliciii. ( )('cii,sioiiall,v tlicv have 

 been alluded to in slightly greater detail by a few authors 

 in this country. On the other hand many valuable investiga- 

 tions carried on during the last quarter century by German 

 workers, to explain closely related subjects, have thrown con- 

 siderable light upon our problem. For the establishment of 

 many important })rinciples I am indebted to the writings of 

 Dr. Enist ]\Iiinch Avliich have lieen used as a basis for a por- 

 tion of this paper, since the writer flrnily believes that his 

 explanation of the origin of this infiltration and its physio- 

 logic significance is the ultimate one. For this reason, and 

 in order that the results of his investigations may be brought 

 to the attention of those in this country who may be interested 

 in them, a number of his results and experiments that deal 

 with our question have been quoted.^ 



HISTORICAL. 



It is first necessary to review briefly the older literature 

 dealing with the pathologic changes Avhicli, originating in the 

 region of wounds in wood, are accompanied by a brown dis- 

 coloration and are temied, according to their position and 

 arrangement in the stem, '" protection wood," " protection 

 heart," " false heart," " pathologic heart," and etc. Frank 

 (1895, p. 31)- states that the woody plants, without excep- 

 tion, exhibit the phenomenon of a darkening to a considerable 



^ Tliis study was started in the Botanical Laboratory of The Pennsyl- 

 vania State College vinder the direction of Prof. C. R. Orton, to whom 

 the writer is indebted for advice and through whom he became interested 

 in the problem. Grateful acknowledgment is hereby made of my 

 indebtedness to Dr. William Frear and Dr. Guy Given of the Experi- 

 ment Station for their instruction and advice upon the chemistry of the 

 problem. Furtlier investigation was carried on in the Botanical Labora- 

 tory of The New York State College of Forestry. The writer also wishes 

 to express his gratitude to Dr. L. H. Pennington and Dr. H. P. Brown 

 for many helpful suggestions and criticisms, both of the work and the 

 manuscript. 



- Bibliographic citations in parentheses refer to " Literature Cited," 

 pp. 4G-49. ' 



