1913] FULLER—LAYERING IN BLACK SPRUCE 457 
of the black spruce growing on granite be cut down, their early 
replacement is much more definitely assured (fig. 3). 
By this layering circular areas with a radius of 2-4 meters soon 
become covered with vigorous young upright shoots, like the one 
provided with a white background in fig. 2, which is 2.4 meters 
from the main trunk. This shoot was removed from the soil and 
proved to be one of two upon a prostrate branch rooted at several 
points throughout its length (fig. 4). The orthotropic develop- 
ment of the shoot is well marked, while several other twigs showed 
it in a less marked degree. The development of such shoots seems 
to be closely connected with the production of adventitious roots, 
although not always dependent upon it. Occasionally an abun- 
dance of adventitious roots was unaccompanied by any definitely 
orthotropic shoots (fig. 5). This was frequently noticed in the 
layering of Abies balsamea as it occurs in its shrubby habit in the 
deeper forests. 
The layering was seldom found on Picea canadensis, because 
this species rarely occurs in exposed rocky situations as a member 
of the pioneer forest association. By far the greatest importance 
of the habit, in the Saguenay region, is its abundance in the black 
spruce. Often large clumps of small trees could be referred to the 
parentage of.a few individuals, although with increase in size the 
connections became increasingly difficult to trace. Frequently 
clusters of 6-20 closely clustered young trees (fig. 6) marked the 
spot where a tree of a former generation stood, showing much more 
rapid replacement than could have been effected by seed. 
UNIVERSITY OF CHICAGO 
