Deciduous shrubs or small trees, or climbing by aerial roots, with milky, sometimes poisonous sap. Twigs round or obscurely 3-sided, slender to quite thick; pith large. Buds moderate or small, solitary, sessile, round-ovoid; terminal bud often lacking. Leafscars round to crescent-shaped, or horseshoe-shaped and encircling the bud; bundle-traces numerous in the round leaf-scars, but often 3, 5, or 9 single traces or groups of traces in the narrow leaf-scars; stipule-scars none.
Fig. 176. Rhus typhina.
Fig. 177. Rhus glabra.
Fig. 178. Rhus copallina.
Fig. 179. Rhus aromatica.
Fig. 180. Rhus vernix.
Fig. 181. Rhus rodicans.
Leaf-scars horseshoe-shaped or U-shaped
b. Leaf-scars horseshoe-shaped, nearly encircling the bud;twigs thick
c. Twigs velvety-hairy, rounded.
c. Twigs glabrous, somewhat 3-sided
b. Leaf-scars U-shaped; twigs terete, puberulent
Leaf-scars round, or broadly crescent or shield-shaped
b. Leaf-scars circular, distinctly raised, covering the small yellow hairy buds; twigs slender
b. Leaf-scars broadly crescent or shield-shaped
c. Erect; twigs thick; buds sessile
c. Climbing or bushy-spreading; twigs slender;buds stalked
1. R. typhina L. Staghorn Sumac. A shrub or small tree, 10 m. high or less; twigs densely hairy, the hairs concealing the lenticels; fruits in dense clusters, globular, covered with red hairs, persistent in winter. Thickets, Quebec to Minnesota, south to North Carolina and Iowa (Fig. 176).
2. R. glabra L. Smooth Sumac. A shrub 0. 5-8 m. high, with smooth,glaucous, somewhat 3-sided twigs; fruits in dense clusters, covered with reddish viscid hairs, persistent in winter. Dry soil, Maine and Quebec to British Columbia, south to Florida and Arizona (Fig. 177).
3. R. copallina L. Dwarf Sumac. Shrub or small tree, 10 m. high or less; twigs reddish-brown, downy-puberulent; fruits covered with crimson hairs, persistent in winter. Dry soil,Maine to Illinois, south to Florida and Texas (Fig. 178).
4. R. aromatica Ait. Aromatic Sumac (R. canadensis Marsh.). A straggling fragrant shrub 1-2 m. high, with ascending or diffuse branches; twigs pubescent; buds small, yellow, hairy, covered by the leaf-scars; fruits globose, covered with long soft red hairs. Dry soil, Quebec to Illinois and Nebraska, south to Florida and Texas (Fig. 179).
5. R. vernix L. Poison Sumac. (Toxicodendron vernix Ktze.), Shrub or small tree up to 8 m. high, with smooth, slightly streaked, light to dark gray bark; terminal bud present, glabrate, moderate, 5 mm. or less long; fruit white, conspicuous all winter. Twigs poisonous to the touch, causing a dermatitis. Swamps, Quebec to Minnesota, south to Florida and Texas (Fig. 180).
6. R. radicans L. Poison-Ivy. (R. toxicodendron of authors, not L. ; Toxicodendron radicans Ktze.). A shrub, erect and bushy, scrambling over rocks, or climbing by aerial roots; twigs sparingly pubescent or glabrate; fruits greenish-white. Poisonous to the touch, in winter as well as summer. Thickets and fence-rows, Quebec to British Columbia, south to Florida, Texas, New Mexico and Arizona; often too abundant (Fig. 181).