URTICACEAE (NETTLE FAMILY) 345 



acbene In fruit. Embryo curved or colled. Herbs with watery juice, mostly opposite lotted 

 or divided leaves and persistent stipules. 



4. Cannabis. Fertile flowers spiked-clustered. Leaves 5-7-divided. Erect. 



5. Humulus. Fertile flowers in a short spike forming a membranaceous catkin in fruit. 



Leaves 3-5-lobed. Climbing. 



Tribe IV. MdREAE. Flowers unisexual ; calyx becoming fleshy or juicy in fruit. Anthers in- 

 flexed In the bud. Ovule pendulous. Fruit an achene. Embryo curved. Trees or shrubs, 

 with milky juice, alternate leaves, and fugacious stipules. 



6. Maclura. Sterile flowers in loose racemes ; fertile In globose heads. Leaves entire. 



7. Broussonetia. Sterile flowers In dense catkins ; the fertile in globose heads. Leaves serrate, 



often lobed. 



8. Moras. Fertile and sterile flowers In separate spikes. Leaves dentate, 8-ncrved. 



Tribe V. URTfCEAE. Flowers unisexual. Filaments indexed in the bud. Style or stigma 

 simple. Ovary 1-celled, with an erect ovule, forming an achene In fruit. Embryo straight. 

 Herbs with watery juice. 



* Calyx in the fertile flowers of 2-5 separate or nearly separate sepals. 

 - Plant beset with stinging bristles. 



9. Drtica. Sepals 4 in both fertile and sterile flowers. Achene straight and erect, Inclosed by 



the 2 inner and larger sepals. Stigma capitate-tufted. Leaves opposite. 



10. Laportea. Sepals 5 in the sterile flowers, 4 In the fertile, or apparently only 2. Stigma long- 



subulate. Achene very oblique, deflexed, nearly naked. Leaves alternate. 

 - +- Plant wholly destitute of stinging bristles; leaves opposite. 



11. Pilea. Sepals 3 or 4, those of the fertile flowers unequal, all or all but one small. Achen 



partly naked, straight and erect. Stigma pencil-tufted. Smooth and shining. 

 * * Fertile calyx tubular or cup shaped, Inclosing the achene ; unarmed. 



12. Boehmeria. Flower-clusters spiked, not involucrate. Style long and thread -shaped, stig- 



matic down one side. Leaves opposite, serrate. 



13. Parietaria. Flowers in involucrate-bracted clusters. Stigma tufted. Leaves alternate, 



entire. 



1. tJLMUS [Tourn.] L. ELM 



Calyx bell-shaped, 4-9-cleft. Stamens 4-9, with long and slender filaments. 

 Ovary 1-2-celled, with a single anatropous ovule suspended from the summit of 

 each cell; styles 2, short, diverging, stigmatic along the inner edge. Fruit a 

 1-celled and 1-seeded membranaceous samara. Albumen none ; cotyledons large. 

 Flowers purplish or yellowish, in lateral clusters. Leaves strongly straight- 

 veined, short-petioled, and oblique or unequally somewhat heart-shaped at base. 

 Stipules small, caducous. (The classical Latin name.) 



* Flowers nearly sessile ; fruit, orbicular, not ciliate ; leaves very rough above. 



1. U. fiilva Michx. (SLIPPERY or RED E.) Buds before expansion soft- 

 downy with rusty hairs ; leaves ovate-oblong, taper-pointed, doubly serrate, 1-2 

 dm. long, sweet-scented in drying, soft-downy beneath or slightly rough down- 

 ward ; branchlets and pedicels downy ; calyx-lobes and stamens 6-9; fruit (1.6- 

 1.8 cui. wide) with the cell pubescent. Rich soil, w. Que. and N. E. to L. Huron, 

 the Dakotas, and southw. Mar., Apr. A small or middle-sized tree (16-20 m. 

 high), with tough reddish wood, and a very mucilaginous inner bark. 



2. U. CAMPESTRIS L. (ENGLISH E.) A large irregularly branched tree with 

 glabrous pedicels and large suborbicular glabrous fruit. Commonly planted for 

 shade, and tending to escape. Variable; some forms with corky-winged 

 branchlets. (Introd. from Eu.) 



* * Flowers on slender drooping pedicels, which are jointed above the middle; 



fruit ovate or oval, fringed-ciliate ; leaves smooth above or nearly so. 

 *- Flowers vernal, appearing before the leaves. 



3. U. americana L. (AMERICAN or WHITE E.) Buds glabrous; branches 

 not corky ; leaves obovate-oblong or oval, abruptly pointed, sharply and often 



