122 Mvricaceae 
POPULUS POPLAR 
Trees; bud-scales resinous. Leaves wide (ours) or narrow, usually long-petioled ; 
stipules minute, fugaceous. Ament-scales fimbriate or incised. Disk cup-shaped, oblique, 
lobed or entire. Staminate aments dense, pendulous: stamens 6—40.  Pistillate aments 
sometimes iaceme-like, erect to pendulous: ovary sessile; style short; stigmas 2—4, entire 
or 4-lobed. Capsule 2—4-valved. Seed-hairs often very long and conspicuous. (le 
populus—the common people; these were planted in public places by the Romans.) 
A.  Petiole strongly flattened laterally. 
B. Tree not strikingly narrow for its height; branches spreading, their angle with 
the stem more than 45°; leaves ovate to suborbicular, short-pointed. W. E. 
P. tremuloides Michx. (Aspen) 
BB. Tree strikingly narrow for its height; branches nearly erect, their angle with the 
stem less than 45°; leaves broadly deltoid, abruptly acuminate. W.E. (P. dila- 
tata.) P. nigra italica DuRoi (Lombardy Poplar) 
AA.  Petiole terete or channeled, scarcely or not at all flattened laterally. 
C. Leaves persistently and densely white-tomentose beneath, 3—5-lobed or irreg- 
ularly dentate. W. P. alba L. (Silver-leaf Poplar) 
CC. Leaves glabrous or nearly so when mature, crenate or crenulate. 
D. Petiole 2.5——5 cm. long; leaves mostly ovate-lanceolate, rounded or subcordate 
at base; capsule 3-valved. W. E. 
Pp. trichocarpa T. & G. (Cottonwood) 
DD.  Petiole 0.6—1.3 cm. long; leaves mostly lanceolate, rounded or obtuse at 
base; capsule 2-valved. E. 
P. angustifolia Jas. (Narrow-leaved Cottonwood) 
MYRICACEAE Sweet Gale Family 
Shrubs or trees. Leaves alternate, simple, resinous-dotied. Flowers in aments, 
monoicous or dioicous, naked, only | in the axil of each scale. Stamens 2—16, on the 
receptacle; filaments short, distinct or somewhat united; anthers ovate, 2-celled. Ovary 
l-celled, subtended by 2—8 branchlets; style very short; stigmas 2, linear. Fruit a 
small drupelet (ours) or a nut. Seed 1. 
MYRICA 3 
Shrubs or small trees. Leaves oblanceolate (ours), entire or dentate (ours) or 
lobed, pinnately veined. Staminate aments oblong or nearly cylindric, expanding before or 
with the leaves: stamens 48. Pistillate aments ovoid or subglobose: ovary subtended 
by 2—4 bractlets. Fruit a drupelet, globose or ovoid, waxy. (Gk. myrikn—the name 
of the Tamarisk.) 
A. Shrub, 0.3——2 m. high; leaves deciduous, 2—5 cm. long; staminate aments | 2—21 
mm. long. W. M. gale L. (Sweet Gale) 
AA. Tree, 3—6 m. high; leaves evergreen, 5-10 cm. long; staminate aments 6—10 
mm. long. W. M. californica, Cham. (Wax-myrtle) 
BETLUACEAE Birch Family 
Shrubs or trees. Leaves alternate, petioled, simple, pinnately veined; stipules fuga- 
ceous. Flowers monoicous, rarely dioicous, in aments or head-like: clusters; staminate - 
aments pendulous; pistillate aments erect to drooping, spike-like or head-like or bud-like. 
Staminate flowers 1—3 in the axil of each scale: perianth 2—4-parted or -toothed, 
membranous or none: stamens 2—10, on the receptacle; filaments distinct. Pistillate 
