73. Urticaceae 1 59 



73. Urticaceae Reichenb. — Nettle Family 



1. Leaves mostly opposite. 



2. Plants often with some stinging hairs; stigma capitate-tufted 1. Urtica 



2. Plants without stinging hairs. 



3. Plants perennial, more or less pubescent; stems opaque; stipules sepa- 

 rate; stigma filiform 2. Boehmeria 



3. Plants annual, chiefly glabrous; stems translucent; stipules united; 



stigma capitate-tufted 3. Pilea 



1. Leaves alternate. 



4. Plants with stinging hairs; leaves ovate, 5-12 cm broad; flowers in loose 



branched cymes 4. Laportea 



4. Plants without stinging hairs; leaves lanceolate, less than 2.5 cm wide; 

 ffowcr-clusters sessile in the leaf-axils 5. Parietaria 



1 . Urtica L. — Nettle 

 1. Plants perennial, 0.5-3 m tall; flower-clusters in branched panicu- 

 late spikes; alluvial soil in the n. half of the state. July- Aug. 

 [U. procera Muhl. ; U. dioica of auth., non L.] Common Nettle 



U . gracilis Ait. 



1. Plants annual; flower-clusters shorter than the petioles. 



2. Leaves ovate, crenate-serrate, the upper ones much smaller; 

 achenes oval, 1.2 mm long; alluvial soil, usually near base of 

 cliffs; known from Alexander and Jackson counties. Apr.- 



July U. chamaedryoides Pursh 



2. Leaves oval to ovate, deeply laciniate-dentate ; stem leafy to the 

 tip; achenes ovate, L7 mm long, microscopically puncticu- 

 late; waste places, occasional; nat. from Eur. Burning 

 Nettle. June-Sept U . urens L. 



2. Boehmeria Jacq. — False Nettle 

 I. Leaves thin, smooth or slightly scabrous above, the petioles about 



as long as the blades; moist woods. July-Sept 



B. cylindrica (L.) Sw. 



1. Leaves firm, strongly scabrous above, the petioles much shorter 



than the blades; marshy ground, rare ....B. drummondiana Wedd. 



3. Pilea Lindl. — Clearweed 

 \. Mature achenes yellowish green, oval, 1-1.5 mm long, with brown 



or purple spots; moist shaded ground, common. July-Sept 



P. pumila (L.) A.Gray 



L Mature achenes green or dark purple, ovate, L5-2 nun long, with 



a very narrow hyaline margin; moist ground, rare; July-Sept. 



[P.opaca (LuneU) Rydb.] ..'. P. fontana (Lunell) Rydb. 



4. Laportea Gaud. — Wood Nettle 

 L. canadensis (L.) Gaud. Woods, common. July-Aug. 



5. Parietaria L. — Pellitory 

 P. pennsylvanica Muhl. Woods, common. May-Sept. 



