MYRICACEAE (SWEET-GALE FAMILY) 73 



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. — 

 Common shade-tree. P. dilatata (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 irregularly 

 dentate. ■ W. — Common shade-tree. P. alba (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. — Wood used in making paper. 



P. trichocarpa (cottonwood) 



DD. Petiole 0.6-1.3 cm. long; leaves mostly lanceolate, rounded or obtuse at base; 



capsule 2-valved. E. P. angustlfolla (narrow-leaved cottonwood) 



MYRICACEAE (Sweet-gale Family) 



Shrubs or trees. Leaves alternate, simple, resinous-dotted. 

 Flowers in aments, monoecious or dioecious, naked, only i in the axil 

 of each scale. Stamens 4-8, on the receptacle; anthers ovate, 

 2-celled. Ovary i-celled, subtended by 2-4 bractlets; style 

 very short; stigmas 2, linear. Fruit a small drupelet. Seed i. — 

 Only the following genus. 



MYRICA 



Leaves oblanceolate, dentate. Staminate aments oblong or nearly 

 cylindric. Pistillate aments ovoid or subglobose. Fruit globose or ovoid, 

 waxy. — (Gk. myrike = the name of the Tamarisk.) 



A. Shrub, 0.3-2 m. high; leaves deciduous, 2-5 cm. long; staminate aments 12-21 

 mm. long. W. M. gale (sweet gale) 



AA. Tree, 3-6 m. high; leaves evergreen, S-io cm. long; staminate aments 6-10 mm. 

 long. W. M. califomica (wax myrtle) 



BETULACEAE (Birch Family) 



Shrubs or trees. Leaves alternate, petioled, simple; stipules 

 fugaceous. Flowers monoecious or rarely dioecious, in aments or 

 headlike clusters; staminate aments pendulous; pistillate aments 

 spikelike or headlike or hudlike. Flowers 1-4 in each scale axil'; 

 perianth membranous or none, entire or 2-4 toothed; stamens 

 2-10; style 2-cleft or divided. Fruit a nut or samara, flat or ovoid- 

 globose, mostly i-celled and i-seeded. 



A. Leaves densely stiff-hairy making them velvety to the touch; pistillate inflores- 

 cence budlike, 5-10 mm. long; fruit a nut, i cm. or more in diameter, solitary 

 or 2-3 in a group, each inclosed in a leafy involucre; shrub. W. C. E. — (Gk. 

 korys = a helmet; referring to the involucre.) Corylus califomica (hazel) 



AA. Leaves not densely stiff-hairy nor velvety to the touch; pistillate inflorescence 

 amentlike or coneUke; fruits small, many grouped together in cones or aments, 

 without involucre; shrubs or trees. 



