37° BOTANICAL GAZETTE [NOVEMBER 
The branches proceeding from the primary substems have also branches, 
equally healthy with themselves, proceeding from them, and with every appear- 
ance of their producing others. . .. . e primary substems, which constitute 
the inner concentric circle of young trees, vary from 8 feet to 25 feet in height; 
and the secondary substems, which form the trees of the outer circle, are from 
4 feet to 10 feet high. There are upward of thirty rooted stems surrounding 
the mother tree, and 30 feet is the greatest diameter of the space covered by 
stoloniferous branches; though in one case a secondary layer has reached as 
far as 18 feet from the main trunk. 
Loupon also mentions cases of abundant layering in Abies nigra 
(Picea mariana [Mill.] BSP.). 
UNZE (7) also refers to M’Nas’s observations and concludes 
from these and other cases that ‘Coniferae, especially the Abie- 
tineae, possess widely extended power of root formation and are 
able to send out rooting shoots.” 
KiHLMAN (6) notes that Picea excelsa growing at the arctic tree 
line in Lapland spreads extensively by layering. He describes 
the occurrence of the habit as follows. The lowest branches often 
have roots, and from their tips new erect shoots develop, which 
become treelike in form and come to lead independent lives; from 
this results a complex of shoots and small trees of various ages, 
which is very sharply bounded, and which often arises from a single 
parent. Such a group, 4 meters in diameter, included 42 stems 
more than 4 cm. thick, besides numerous smaller ones. The age 
of such a centrifugally spreading group of spruces may almost 
be unlimited. He distinguishes two habit varieties of Pues 
excelsa. One possesses a tall cylindrical crown, often extending 
to the ground, the lower branches seldom rooting, and the life of 
the individual thus ending with the death of the main trunk. The 
other variety, characteristic of the region of the northern limit 
of the spruce, is low and scrubby, and layers abundantly as described 
above. 
Curist (2) refers to layering in Picea excelsa as of rare occur 
rence, and names such forms Picea excelsa forma stolonifera. 
GOEBEL (5) mentions cases of layering in Picea excelsa, P. nigra; 
and Abies sibirica. 
ScHROTER (11) describes and illustrates something very similar 
in the case of Pinus montana in the timberline belt of the Alps- 
