34 Distinguishing Species of Populus and Fuglans [January, 
stem not far from the base of the growth of last year; the others 
are taken from near the middle of the same growth. These illus- 
trations and the succeeding ones are all drawn to the same 7 
unless otherwise designated. 
Populus grandidentata.—In thrifty twigs, one year old, the pith 
is yellowish white; the wood greenish white. The pith in twigs 
two or three years old is light brown. The buds are slightly 
pubescent under a lens and of a grayish-brown color, not viscid, 
Near the middle of a branch, the leaf scars are about as broad as 
long. Near the base the transverse diameter is the greater. The 
internodes of this species in slow or in rapid growth are much 
longer than those of P. tremuloides. They are often twice as long 
in stems which have made the same amount of growth. Fig. 2, 
a bc, illustrates the buds and leaf scars on young stems of P. 
grandidentata. 
Populus monilifera—tThe pith is light-brown and a cross section 
is: usually pentagonal. - In most slender young branches the pith is 
green, changing to brown on an exposure of a few minutes to the 
air. The shape of the leaf scars is about midway between that of P. — 
tremuloides and P. grandidentata, Branches which have made — 
slow growth and the base of thrifty branches are often without 
~ angles on the surface. Thrifty young branches have from five to — 
eight prominent vertical ridges. One of these ridges extends — 
below the center of a bud and one runs down from either side of — 
the leaf scar. The branches are of a yellowish or greenish-brown : 
color. There are a few round or oval white or brown spots on — 
thrifty stems a year old. The buds are brown, viscid, not very — 
glossy, and are destitute of pubescence, except a little on the 
margins of bud scales. The buds are larger but their shape is — 
much the same as those of P. tremuloides. On thrifty branches 
there are often some buds mixed in with those larger which aré — 
short and not fully sidinls eas For illustrations see Fig. 3, - 
abca. a 
Populus balsamifera—The young branches are brown and pol- a 
ished. The lower buds of the season are broad and small, and 
the scar below is broad. The lower buds and leaf scars of these a 
four species of Populus are much alike in shape. The buds on - 
the middle of the thrifty growth of P. da/samifera are quite long, 
often seven-eighths of an inch. They are curved and pointed, 
and become viscid. .Fig. 4,a 0c de, illustrate buds and leaf scars 
of this species. 
