66 CANNABINACEAE 



Family 35. CANNABINACEAE. Hemp Family. 



Erect herbs; leaves digltately divided to near the base; pistillate flowers in axillary stiff 

 spikes. 1. Cannabis. 



Twining vines; leaves merely digltately lobed; pistillate flowers in drooping ament-like 

 spikes with imbricate bracts. 2. HdmuIiUS. 



1. CANNABIS L. Hemp. l. C. sativa. 



2. HUMULUS L. Hops. 



Leaf-blades 3-7-lobed about half-way to the base, with ovate, acute or short-acuminate 

 lobes; those of the inflorescence 3-lobed or undivided. 1. H. Lupulus. 



Leaf-blades 5-7-divided to near the base, with lanceolate, long-acuminate divisions ; those 

 of the inflorescence 5-cleft. 2. H. neomexicanus. 



Family 36. URTICACEAE. Nettle Family. 



Herbs with stinging hairs; leaves opposite; flowers not involucrate. 1. ITrtica. 



Plants without stinging hairs; leaves alternate; flowers involucrate by leafy bracts. 



2. Pabietabia. 



1. URTICA (Tourn.) L. Nettle. 



Stipules membranous, oblong or broadly lanceolate, obtuse or acutish, often 1 cm. long. 

 Stem and leaves densely pubescent. 



Stem and lower surface of the leaves coarsely velvety. 1. U. holosericea. 



Stem finely strigose; lower surface of the leaves finely short-pubescent. 



2. U. Breweri. 

 Stem nearly glabrous; leaves puberulent, in age becoming glabrate. 



3. U. Lyallii. 

 Stipules narrowly lanceolate or linear, attenuate. 



Teeth of the leaves ovate, strongly directed forward. 



Stem glabrous except the presence of a few bristles; leaves thin, almost glabrous, 

 not strougljr veined. 

 Petioles one-third to one-half as long as the cordate or broadly ovate leaf- 

 blades. 4. U. cardiophylla. 

 Petioles one-flfth to one-third as long as the lanceolate or ovate-lanceolate 

 leaf-blades. 5. U. viridis. 

 Stem more or less strigose or hirsute; leaves decidedly hairy, especially on the very 

 strong veins. 

 Leaf-blades lanceolate, scarcely cordate at the base. 



Stem sparingly strigose and bristly. 6. U. gracilis. 



Stem densely strigose, scarcely at all bristly. 7. C/. strigosissima. 



Leaf-blades broad, deeply cordate at base. 8. 17. dioica. 



Teeth of the leaves broadly triangular, not strongly directed forward; stem and leaves 

 glabrous or nearly so. 9. U. gracilenta. 



2. PARIETARIA (Tourn.) L. Pellitory. 



Leaf-blades lanceolate, 2-7 cm. long, twice as long as the petioles or longer. 



Plant comparatively dark green ; stem densely puberulent; sepals lanceolate, Eicute. 



1. P. pennsylvanica. 

 Plant very light green; stem long- villous ; sepals ovate, often obtuse. 



2. P. occidentalis. 

 Leaf-blades oblong or ovate-oblong, 0.5-2 cm. long, not twice as long sis the petioles. 



3. P. obtusa. 



Family 37. POLYGONACEAE. Buckwheat Family. 



Leaves without stipules; flowers or flower-clusters subtended by involucres of pjirtly 

 united bracts; stamens mostly 9. 

 Involucres from tubular to campanulate, of several united bracts. 



Involucres awnless, campanulate or turbinate, 4-8-toothed or -lobed. 



1. Ebiogonum. 

 Involucres awn-pointed. 



Involucres herbaceous; flowers exserted; achenes lenticular. 



2 OjCYTHPr'A 



Involucres leathery or homy; flowers included; achenes 3-augled. 



Involucres with 3-6 awn-tipped spurs near the base, 1-3-flowered, in open 



dichotomous panicles. 3. Centbostegia. 



Involucres without spurs, 1-flowered. 



Involucres 6-angled, siUcate; fllaments adnate to the base of the peri- 

 anth. 4. Chobizanthe. 

 Involucres 3-angled; fllaments adnate to the whole tube of the perismth. 



5. ACANTHOGONIT.M. 

 Involucres bract-like, 2-cleft. 6. Ptbrostegia. 



Leaves with sheathing stipules (ocreae); flower-clusters not involucrate; steimens 4-8. 

 Stigmas tufted. 



Sepals 6; styles 3; achenes triangular. 7. Eumex. 



Sepals 4 ; styles 2 ; achenes lenticular. 8. Oxtbi\. 



