RHUS 



133 



scars round to crescent-shaped, or horseshoe-shaped and encir- 

 cling 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. 



a. Leaf-scars horseshoe-shaped or 

 U-shaped 



b. Leaf-scars horseshoe-shaped, 

 nearly encircling the bud;twigs 

 thick 



c. Twigs velvety-hairy, rounded. 1. R. typhina 

 0. Twigs glabrous, somewhat 



3-sided 2. R. glabra 



b. Leaf-scars U-shaped; twigs 

 terete, puberulent 



a. 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 



3. R. copallina 



4. R. aromatica 



c. Erect; twigs thick; buds sessile 5. R. vernix 

 c. Climbing or bushy- spreading; 



twigs slender; buds stalked 6. R. radicans 



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 Ari- 

 zona (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 



