URTICACEAE 357 



wise glabrous, simple or branched at the base or above : leaf-blades thin, varying from 

 suborbicular on the lower part of the stem, through ovate to lanceolate on the upper part of 

 the stem, 1-4 cm. long, obtuse or acute, crenate-dentate, truncate or cordate at the base or 

 the upper ones acutish ; petioles slender, i-i as long as the blades : flower-clusters shorter 

 than the petioles : sepals oblong or those of the pistillate flowers oval, less than 1 mm. long, 

 obtuse : achene ovoid, 1 mm. long, enveloped in the 2 accrescent sepals. 

 In thickets, Kentucky to Arkansas, Florida and Texas. Spring and summer. 



3. Urtica Brfeweri S. Wats. Perennial, stout, finely pubescent with somewhat curled 

 hairs or glabrate except scattered bristle-like hairs. Stems 4-12 dm. tall, often branched : 

 leaf-blades thin, lanceolate to narrowly oblong, 7-20 cm. long, acuminate, coarsely serrate 

 with somewhat flaring teeth, rounded or subcordate at the base ; petioles about ^ as long as 

 the blades : panicles about as long as the ]ietioles : sepals oval, 1 mm. long, obtuse, densely 

 hispid : achene ovoid, 1.2 mm. long, enveloped in the 2 accrescent sepals. 



On river banks, Wyoming to California, Texas and Mexico. Summer and fall. 



4. Urtica gracilis Ait. Perennial, slender, sparingly pu))escent with stinging hairs. 

 Stems erect, 6-18 dm. tall, angled, simple or sparingly branched above : leaf-bhides thin, 

 lanceolate to ovate-lanceolate, 6-15 cm. long, acuminate, rather coarsely serrate, the teeth 

 often somewhat incurving, acute or oljtuse at the base ; petioles ^-} as long as the blade : 

 panicles much longer than the petioles : sepals suborbicular, about 1 mm. long, densely 

 puberulent : achenes ovoid, 1.2 mm. long, enveloped in the accrescent ovate sepals. 



On river banks and along fences. Nova Scotia to British Columbia, North Carolina and Louisiana. 

 Summer and fall. 



5. Urtica dioica L. Perennial, stoutish, densely bristly with stinging hairs. Stems 

 erect, 6-13 dm. tall, simple or branched : leaf-blades ovate to ovate-lanceolate, 3-12 dm. 

 long, acute or short-acuminate, coarsely serrate or sometimes incised, cordate at the base ; 

 petioles ^-j as long as the blades : panicles shorter than the petioles or about equalling them 

 in length : sepals densely soft-pubescent, less than 1 mm. long, the outer obovate, the inner 

 spatulate : achene suborbicular, 1 mm. long, enveloped in the accrescent depressed orbicular 

 sepals. 



In waste places. Nova Scotia to Minnesota, South Carolina and Missouri. Naturalized from 

 Europe and Asia. Summer and fall. 



2. URTRICASTRUM Fabr. 



Perennial herbs (shrubs or trees in the tropics), armed with stinging hairs. Leaves al- 

 ternate : blades often large and membranous, toothed : stipules distinct. Flowers monoecious 

 or dioecious, mostly in axillary panicted or dichotomous cymes, the staminate with a 

 perianth of 5 partially united sepals, 5 stamens, and a rudimentary ovary. Pistillate 

 flowers with a perianth of 4 partially united somewhat unequal sepals and an oblique 

 ovary : style subulate, becoming lateral. Achene oblique with a membranous or fleshy 

 pericarp. Wood Nettle. 



1. Urticastrum divaricatum (L. ) Kuntze. Foliage bright green, bristly witli sting- 

 ing hairs. Stems 2-1 2 dm. tall, often flexuous : leaves alternate ; blades thin, ovate, oblong 

 or elliptic, 5-20 cm. long, acuminate, coarsely serrate or crenate-serrate, rounded or rarely 

 acutish at the base, glabrous or bristly, especially on the nerves ; petioles slender, h as long 

 as the blades or longer : panicles slender, spreading, the lower staminate, the upper pistil- 

 late : sepals oblong (in the staminate flowers) or suborbicular (in the pistillate), hyaline, 

 or with hyaline margins : achene oblique, almost 3 mm. in diameter, the style lateral, about 

 twice as long as the 2 accrescent sepals. [Laportea Canadensis Gaud.] 



In thickets and rich woods. Nova Scotia to Minnesota, Florida and Kansas. Summer and fall. 



3. ADICEA Raf. 

 Annual or perennial herbs, with pellucid watery tissues, destitute of stinging hairs. 

 Leaves opposite : blades often 3-nerved or nearly nerveless, and transversely ridged or 

 wrinkled, entire or toothed : stipules interpetiolar. Flowers monoecious or dioecious, in 

 axillary panicled or congested cymes, the staminate with a perianth of 4 or rarely 2-3 

 partially united sepals, the tube often cup-like, 4 or rarely 2-3 stamens and a rudimenfary 

 ovary. Pistillate flowers with a perianth of 3 partially united sepals and an equilateral 

 ovary surrounded by 4 or rarely 2-3 staminodia : stigma tufted. Achene flattened, with 

 a membranous pericarp. [Pilea Lindl.] Richweed. Clearweed. 



Leaf-1)lades 2-10 mm. long, entire, transversely wrinkled or ridged. 



Stems filiform : leaf-blades suborbicular or broadly oval, 2-4 mm. long. 1. A. herniarioides. 



Stems not filiform : leaf-blades elliptic or oblanceolate, 5-10 mm. long. 2. A. microphylla. 



Leaf-blades 3-10 cm. long, toothed, not transversely roughened. 3. A. pumila. 



