78 URTICACEAE. 



Alnus tenuifolia Nutt. Small tree, 5-10 m. tall; bark whitish even on the 

 twigs; buds pubescent; leaves ovate or somewhat obovate, mostly obtuse, 

 rounded or subcordate at the base, with a small lobe at the end of each vein, 

 dentate-serrate, dull-green, 3-8 cm. long, sparsely pubescent on both sides, 

 becoming glabrous above; petioles stout, pubescent, 1-1.5 cm. long; fruiting 

 aments ovate, 1-2.5 cm. long, resinous, with shorter peduncles. Along streams, 

 not rare. 



Family 26. ULMACEAE. ELM FAMILY. 



Trees or shrubs; leaves alternate, simple, serrate or entire, 

 petioled, pinnately veined, with usually fugacious stipules; 

 flowers small, monoecious, dioecious, perfect or polygamous; 

 sepals 3-9, free or united; petals none; stamens as many as the 

 sepals and opposite them; ovary 1 -celled; ovule one; fruit a 

 samara, drupe or nut. 



107. CELTIS. 



Trees or shrubs; leaves serrate or entire, pinnately veined; 

 flowers polygamous or monoecious, borne in the axils of the 

 season's leaves, the staminate clustered, the fertile solitary or in 

 2-3-flowered clusters; calyx 4-6-parted; ovary sessile; stigmas 

 2 ; fruit an ovoid or globose drupe. 



Celtis douglasii Planch. Hackberry. Scraggly tree or shrub, 3-5 m. tall; 

 leaves oblique-ovate, acuminate, cuneate at the base, sharply serrate, pu- 

 bescent when young, glabrous and shiny above when mature, somewhat 

 pubescent on the veins beneath, rough, reticulated, 4-8 cm. long; petioles 

 about 1 cm. long; fruit reddish, globose, smooth, 5-7 mm. in diameter, on 

 slender peduncles, about 2 cm. long. Basaltic bluffs on Snake River; a hand- 

 some tree when grown in good soil, but under natural conditions very scraggly; 

 leaves often distorted as a result of insect attacks. 



Family 27. URTICACEAE. NETTLE FAMILY. 



Herbs (in ours); leaves alternate or opposite, simple, with or 

 without stipules; flowers small, monoecious, dioecious or polyg- 

 amous; calyx of 2-5 nearly separate sepals or cup-shaped; 

 petals none ; stamens as many as the calyx-lobes and opposite 

 them; ovary 1 -celled, mostly superior; ovule solitary; fruit an 

 akene; endosperm scanty or none. 



Leaves opposite, with stinging hairs. 108. URTICA, 78. 



Leaves alternate, without stinging hairs. 109. PARIETARIA, 79. 



108. URTICA. NETTLE. 



Annual or perennial simple or branching herbs with stinging 

 hairs; leaves opposite, 3-7-nerved, petioled, dentate or incised, 

 with distinct stipules; flowers greenish, very small and numerous, 



