minute-pubescent, dull-brown where abraded, included at base only. Q. aquatica 

 Walt., Q. nigra var. tridentifera Sarg. 



In wet forests, edge of swamps and streams, and in river bottomlands in s.e. 

 Okla. and e. Tex.; e. to the Atl. States and n. to Mo. and Del. 



Fam. 49. Ulmaceae Mirb. Elm Family 



Trees or rarely shrubs with watery sap; buds with imbricate scales; leaves simple, 

 2-ranked, alternate, usually oblique at base, pinnately veined, serrate or rarely 

 entire; stipules deciduous; flowers perfect or unisexual with both sexes on the 

 same plant; perianth 4- or 5-merous, rarely more or less, usually somewhat 

 connate; stamens (in bud) with curved or somewhat sigmoid filaments, as many 

 as or twice as many as the perianth lobes; filaments straight; ovary superior, 

 1-celled, with 1 suspended anatropous ovule; style 2-parted; fruit a samara, nut 

 or drupe. 



About 15 genera with more than 200 species in both hemispheres. 



1. Planera J. F. Gmel. 

 A monotypic genus. 



1. Planera aquatica (Walt.) J. F. Gmel. Water-elm, planer-tree. Fig. 395. 



Small deciduous polygamo-monoecious tree with spreading branches to form 

 a low broad crown, to about 12 m. high, the short trunk with reddish-brown scaly 

 and flaky bark; branchlets puberulous; winter-buds subglobose, minute; leaves 

 with petioles 3-6 mm. long, rhombic-ovate to ovate-oblong, 3-8 cm. long, to 25 

 mm. wide, unequal at the rounded to cuneate base, acute at apex, unequally ser- 

 rate, scabrate above, pinnately veined, at maturity glabrous; calyx deeply 4- or 

 5-lobed; staminate flowers in clusters at base of the young branchlets; stamens 

 4 or 5; perfect flowers 1 to 3 in the axils of the young leaves; fruit ellipsoid, about 

 8 mm. long, with irregularly crested fleshy ribs. 



In water of streams and lakes and in alluvial floodplains subject to periodic 

 flooding, often forming large stands, in s.e. Okla. (McCurtain Co.) and e. Tex.; 

 from Fla. to Tex., n, to s. 111. and Ky. 



Fam. 50. UrticaceaeJuss. Nettle Family 



Annual or perennial herbs, sometimes with stinging hairs, frequently succulent 

 and with watery sap; leaves simple, alternate or opposite, mostly stipulate; flowers 

 minute, greenish, unisexual or rarely perfect, in simple or branched spikes or 

 clusters; calyx 2- to 5-cleft or of separate sepals; petals none; stamens as many 

 as the calyx lobes or sepals and opposite them, the filaments inflexed; ovary 

 superior, 1-celled; style simple, with a capitate or filiform stigma; ovule solitary, 

 erect or ascending, orthotropous; fruit an achene, often tipped with the persistent 

 style or enclosed by the accrescent calyx. 



About 45 genera and 600 species of wide geographic range, but mostly tropical 

 and subtropical. 



1. Leaves alternate 1. Laportea 



1. Leaves opposite or rarely alternate (2 ) 



2(1). Calyx of pistillate flowers tubular or cupuliform, enclosing the achene; 

 plants without stinging hairs 2. Boehmeria 



2. Calyx of pistillate flowers of 2 to 5 separate or nearly separate sepals (3) 



3(2). Plants more or less pubescent, beset with stinging bristles; achene enclosed 

 by the calyx 3. Urtica 



788 



