[From the BULLETIN OF THE TCRREY BOTANICAL CLUB 40; 271-293. 19 Jnne 1913.] 



Observations on the inception, season, and duration of cambium 



development in the American larch [Larix laricina 



(Du Roi) Koch,]* 



L. KNUDSON 

 (WITH PLATES 1 8 AND 19) 



INTRODUCTORY 



During the past twenty-five years very little attention has been 

 devoted to a minute study of the diameter increase in trees. 

 Comparatively little is known concerning the season of wood 

 formation; and with respect to the region of the tree in which 

 diameter increase first begins, the evidence is contradictory. 

 With the object of determining the part of the tree in which 

 cambial activity begins, as well as to determine the season of 

 growth, investigations were begun during the season of 1909 and 

 continued in 1911. The results obtained from the study of mate- 

 rial collected these two seasons form the basis of this paper. 



The subject was suggested by Prof. W. W. Rowlee, and to 

 him, as well as to Prof. B. M. Duggar, the writer is indebted for 

 helpful suggestions. 



HISTORICAL 



The work of von Nordlinger, Th. Hartig, Robt. Hartig, Mer, 

 and others has thrown some light upon the extent and duration of 

 cambial activity. They have found, in general, that under 

 forest conditions growth first begins in the youngest twigs and 

 then proceeds downward into the older regions. Less work has 

 been done on the cambial activity in isdlated trees. 



Concerning the region of first cambial activity, Th. Hartigf 

 concluded that it occurred in the youngest twigs and then gradu- 

 ally extended downward. In a 3O-year old Pinus sylvestris, and 

 also in oak, cambial activity began almost simultaneously over 

 the entire trunk, while in larch and maple of the same age cambial 



* Laboratory of Plant Physiology, Cornell University, Contribution No. 8. 

 t Hartig, T. Anatomic und Physiologic der Holzpflanzen, 368. 1878. 



271 



