cup-shaped disk; calyx inferior, rarely lacking; corolla seldom lacking; stamens as 

 many as and alternate with the petals, sometimes twice as many or partially abort- 

 ing; carpels I or 2 to 5 united; styles separate or more usually coalesced; fruit 

 various, dry or drupaceous, with resinous or ceriferous mesocarp and crustaceous 

 or bony endocarp (stone) ; seed with little or no endosperm. 

 About 60 genera and nearly 600 species, mostly in the tropics. 



1. Rhus L. Sumac 



Shrubs or small trees, rarely vines; leaves alternate, simple or compound (in 

 ours); flowers polygamous, in axillary or terminal panicles; calyx lobes 4 to 6, 

 usually 5, persistent; petals imbricated in the bud, spreading in anthesis; disk 

 annular; stamens 5; ovary 1-celled, 1-ovuled; styles 3, terminal; drupe small, sub- 

 globose or compressed, pubescent or glabrous, the exocarp persistent or deciduous; 

 seed solitary, inverted on a stalk that rises from the base of the ovary. 



About 250 species of temperate and tropical regions, most abundant in South 

 Africa. The venacular name is commonly pronounced "shumac." 



1. Leaflets 5 to 17; large shrubs or trees, always in wet habitats 1. R. Vernix. 



1. Leaflets typically 3; small shrubs or vines of usually (but not always) dryish 



habitats (2) 



2(1). Terminal leaflet oblong-elliptic, with broad blunt apex; leaflets entire 

 or with shallow rounded lobes or broad blunt teeth; low creeping 

 shrub 2. R. Toxicodendron var. Toxicodendron. 



2. Terminal leaflet ovate or rhombic, with narrowed apex; usually with some 



leaflets deeply lobed or sharply toothed (3) 



3(2). Petioles and lower surface of leaflets pubescent; low or high-climbing 



vine, sometimes creeping and with erect branches to 18 dm. tall 



2. R. Toxicodendron var. vulgaris. 



3. Petioles and leaflets glabrous; low shrub usually less than 10 dm. tall, forming 



beds from creeping rootstocks 2. R. Toxicodendron var. eximia. 



1. Rhus Vernix L. Poison sumac, poison elder, poison dogwood. Fig. 515. 

 Shrub or small tree to 7 m. high; branchlets glabrous, glaucous at first, gray 



at maturity; leaves odd-pinnate, with glabrous petioles; leaflets 5 to 13, short- 

 stalked, elliptic to elliptic-oblong, 4-10 cm. long, acuminate at apex, cuneate at 

 base, entire, slightly pubescent at first, becoming quite glabrous, with 8 to 12 

 pairs of veins; flowers greenish, in slender axillary panicles to 2 dm. long; fruit 

 subglobose, compressed, 5-6 mm. across, whitish or light yellowish-gray. 



In swamps, bogs, on seepage slopes and in wet thickets in e. Tex., Apr.-June; 

 from Fla. to Tex., n. to N.E. and s.e. Minn. 



The plant, at all seasons, is virulently poisonous to the touch. The leaves 

 turn to orange or scarlet in the fall and are most attractive but dangerous! 



2. Rhus Toxicodendron L. Poison ivy, poison oak, hiedra. Fig. 515A. 



Small shrub or vine with slender glabrate to densely pubescent or puberulent 

 stems and branches, sometimes with aerial root and/or subterranean stolons; 

 leaflets 3, very rarely with some 5, variable, at first more or less pubescent, later 

 glabrate (especially above) or somewhat pubescent beneath, ovate to elliptic 

 or rhombic to obovate, entire or irregularly serrate or dentate to regularly 

 lobate-dentate with 3 to 7 rounded blunt or rarely subacute lobes, rounded to 

 acute or acuminate at apex, rounded to cuneate at the base; terminal leaflet 3-20 

 cm. long, 1.5-13 cm. wide, with a petiolule 1-4.5 cm. long; lateral leaflets some- 

 what smaller than terminal one, inequilateral, often subentire on the upper margin 

 and 3- to 7-lobed on the lower margin, with petiolules 1-5 mm. long; inflorescence 



1093 



