188 ANACARDIACEAE. 



sively for it sometimes. The poisonous group, for which the 

 name Toxicodendron has been used, but to which the name 

 Rhus is most strictly applicable, is equally distinct in leaf- 

 scars from the true sumachs, to which the name Schmaltzia 

 is extended. Opinions differ as greatly in the definition of 

 their species as in the limitation of these nominal genera; 

 and Greene, in the eighth volume of Proceedings of the Wash- 

 ington Academy of Sciences, has made no fewer than 29 spe- 

 cies of what is here called R. glabra. 



1. Leaf-scars round, much elevated, covering the small yellow 



hairy buds: twigs slender. 



(Fragrant sumach). (1). R. canadensis. 

 Leaf -scars C-shaped, nearly encircling the buds: twigs 



stout. 2. 

 Leaf-scars U-shaped: twigs terete, puberulent. 



(2). R. copallina. 

 Leaf-scars broadly crescent- or shield-shaped. Poisonous. 5. 



2. Tall shrubs or small trees. 3. 

 Very low hairy shrub. 



(Southern hairy sumach). R. Michauxii. 



3. Twigs glabrous, 3-sided. (Smooth sumach). (3). R. glabra. 

 Twigs hairy, rounded. 4. 



4. Hairs dense, concealing the lenticels. 



(Staghorn sumach). R. typhina. 

 Hairs scanty: lenticels prominent. 



(Asiatic sumach). R. javanica. 



5. Twigs slender: buds stalked, naked. 6. 

 Twigs stout: buds sessile. 7. 



6. Climbing by aerial roots, or spreading. 



(Poison ivy). (4). R. radicans. 

 Bushy. (Poison oak). R. Toxicodendron. 



7. End-buds yellow-pubescent, large (8-10 mm. long). 



(5). R. vernicifera. 

 End-buds glabrate, moderate (scarcely 5 mm.). 



(6). R. vernix. 



