3. Urtica L. Nettle 

 About 30 species of wide distribution, mostly in the North Temperate Zone. 



1. Urtica dioica L. ssp. gracilis (Ait.) Seland. Fig. 396A. 



Strongly rhizomatous typically monoecious perennial 1-3 m. tall, from glabrous 

 except for a few stinging hairs to strongly bristly and sericeous-pubescent; leaves 

 (5-) 7-15 cm. long, the petiole from nearly one half as long as to scarcely one 

 tenth as long as the blade; stipules prominent, mostly (5-) 10-15 mm. long; leaf 

 blades from narrowly lanceolate and rounded or cuneate at base to broadly ovate 

 and often cordate at base, coarsely serrate; pistillate flowers usually uppermost; 

 perianth 1-2 mm. long, pubescent; achene flattened, about 1.5 mm. long May- 

 Sept. 



We have several varieties of this complex species that are distinguished in the 

 following key. 



1. Leaf blades usually ovate-lanceolate to ovate, the length rarely as much as 

 3 times the width; petioles mostly at least one third or rarely only 

 one fourth as long as the blades; inflorescence not crowded, the 

 floral leaves not greatly reduced and usually well-exceeding the 

 panicle branches var. gracilis. 



1. Leaf blades narrowly to broadly lanceolate, usually at least 3 times as long 



as broad, acute to rounded at base; petioles short, rarely as much 

 as one third as long as the blade; inflorescence crowded above, the 

 upper leaves reduced and usually equal to or exceeded by some of 

 the panicle branches (2) 



2(1). Plants densely pubescent, the stems and leaves usually more or less 

 cinereous var. holosericea. 



2. Plants much less strongly pubescent, the stems and leaves often essentially 



glabrous with only bristles on the stems (3) 



3(2). Stems (at least near the base) usually bristly only, not otherwise hairy; 

 leaves lightly hairy var. procera. 



3. Stems usually moderately hairy as well as bristly; leaves rather strongly hairy 



var. angustifolia. 



Var. gracilis. In thickets, springy places and along streams in the Plains 

 Country and Trans-Pecos of Tex., through N.M. to Ariz.; from B.C. s. to Ariz., 

 eastw. to the Atl. coast. U. gracilis Ait., U. viridis Rydb. 



Var. holosericea (Nutt.) C. L. Hitchc. On banks of streams and ditches, in 

 swamps and marshes, possibly in mts. of Ariz, but yet to be verified; mostly in 

 s.w. U.S., n. to Wash, and Ida. 



Var. procera (Muhl. ex Willd.) Wedd. In wet thickets, alluvial bottomlands 

 along streams and floodplain areas in n.e. Okla. (Ottawa Co.), w. to N.M. and 

 Ariz.; mainly e. U.S. and s. Can. 



Var. angustifolia Schlecht. Low ground and stream banks, ditches and marshes, 

 in mts. of the Tex. Trans-Pecos, through N.M. to Ariz.; also Colo., Calif, and 

 adj. Mex. U. Serra Bl., U. Breweri Wats., U. gracilenta Greene. 



4. Pilea Lindl. Richweed. Clearweed 

 About 400 species, mainly in the tropics. 



1. PUea pumUa (L.) Gray. Fig. 397. 



Low annual to 7 dm. high, usually much smaller, simple to bushy-branched, 

 the bases of large plants decumbent, essentially glabrous throughout; leaves 

 opposite, with petioles about one third as long as to longer than the blade, to 

 15 cm. wide, lustrous, translucent, ovate, rounded to cuneate at base, with a 

 conspicuous linear entire apex, with as many as 17 coarse rounded teeth on each 



792 



