122 
Along Quatre Fourches river, No. 486; 30th base line, Slave river, 
No. 482; Fort Smith, No. 489; Pine Lake district, Nos. 2076, 2079; Peace 
point, No. 2077; Moose (Eight) Lake district, No. 2078; base of eastern 
slope of Caribou mountains, No*. 2075; Little Buffalo river, Russell, No. 23. 
P. tacamahacca Mill, P. halsamifera DuRoi, not L. See Jour. Arn. Arb. x, 55 (1029). 
Balsam, or Black Poplar. 
Abundant in the flood-plain forests where it forms nearly pure stands 
as the first tree in the flood -plain and delta successions. In older lowland 
timber it is mixed with spruce and later is entirely replaced by the latter. 
Throughout the upland districts it is associated with aspen P. tremuloides 
in burned-over country, where it usually appears in the transition timber 
between aspen and spruce. Trees 2 feet in diameter at the base are not un- 
common. Along the main rivers the black poplar has been a source of fire- 
wood for trappers and for the wood-burning steamboats for many years. 
Fruiting catkins were collected between June 7 and June 24. 
Along Quatre Fourches river, Nos. 493, 494; 30th base line, Slave 
river, No. 495; Fort Smith, No. 497; Pine Lake district, No. 2081; Moose 
(Eight) Lake district, No. 2080; base of eastern slope of Caribou moun- 
tains, No. 2082. 
Salix lasiandra Ben tii. See Cent. Am. Arboret. vi, 142-3 (1904). Red Willow. 
Common in the lowland flood-plain and delta districts, where it grows 
at the margins of sloughs and on damp sand and mud bar deposits. Thus 
far it has been found occupying only the transition ground between the 
colonizing willows of bars and sloughs, and the more mesophytic species 
on higher areas. In the deltas it shares this role with S. petiolaris. Flowers 
collected June 14, and mature fruit August 10. 
East shore of lake Mamawi, No. 2084; 30th base line district, Slave 
river, No. 560. 
S. interior Rowlee var. pedicellate (Anders.) Ball. S. linearifolia Rydb. See Can. 
Field-Nat. xl, 175 (1926). Sand-bar Willow. 
Abundant on river sand-bars throughout the region. Pure stands of 
it in such situations are the first of the shrubby growths to appear on 
recently deposited soils, and make a conspicuous, pale-green bank of filmy 
foliage on low islands and local flood-plain deposits. In the lower deltas 
of the large streams it is largely replaced by slough-margin willows like 
S. planijolia. In flower during the first tw r o weeks of June, and in fruit 
during July. Late fruiting catkins cling to the branches and may be 
collected as late as August 20. 
Lower delta of Athabaska river, No. 566; east shore of lake Mamawi, 
No. 2086; along Quatre Fourches river, Nos. 564, 565; 30th base line dis- 
trict, Slave river, No. 563; Peace point, No. 2087. 
S. brachycarpa Nutt. var. antimima (Schneider) Raup. See RJhod. xxxiii, 241^4 
(1931). 
Collected in this region only on the Salt Plains and in Caribou moun- 
tains. In the former region it is an important constituent of the thick- 
ets that margin the prairies, and in the latter it inhabits muskeg thick- 
