198 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



4. Callitriche autumnalis L. 



In shallow water; Great Falls, Md., May, 1899 (Steele). Widely distributed in N. 

 Amer., Eur., and Asia. (C bifida Morong.) 



92. LIMNANTHACEAE. 



1. FLOERKEA Willd. 



1. Floerkea proserpinacoides Willd. False mermaid. 



Low wet soil; High Island, below Dead Run, and Plummers Island. Apr.-May. 

 Eastern U, S. 



93. ANACARDIACEAE. Sumac Family. 



The smoke tree, Cotinus coggyria Scop., is cultivated for its attractive feathery 

 fruiting panicles and highly colored autumn foliage. 



Fruit whitish, glabrous or sparsely pubescent; stone striate; small trees, shrubs, 

 or climbing vines, poisonous to the touch. Leaflets 3-13. 



1. TOXICODENDRON. 

 Fruit reddish or purplish, densely pubescent; stone smooth; shrubs or small trees, not 

 poisonous. 

 Flowers in dense terminal panicles, appearing after the leaves; leaflets more than 3. 



2. RHUS. 



Flowers in clustered spikes, appearing before the leaves; leaflets 3. 



3. SCHMALTZIA. 

 1. TOXICODENDRON Mill. 



Leaflets 7-13; tall shrubs, sometimes treelike 1. T. vernix. 



Leaflets 3; low shrubs, suberect and scrambling, or climbing to considerable heights. 



2. T. radlcans. 



1. Toxicodendron vemix (L.) Kuntze. Poison sumac. 

 Swamps; frequent. July. Eastern U. S. {Rhus venenata "DC; R. vemix h.) 

 This is the most poisonous species. 



2. Toxicodendron radicans (L.) Kuntze. Poison ivy. 

 Woods or open fields; common. May-June. Eastern U. S. {Rhus radicans L.) 

 The typical form is a low erect pubescent plant. Very often, however, the plants 



are climbing and glabrate. The latter form is T. pubescens Mill. (Rhus toxicoden- 

 dron L.; T. toxicodendron Britton.) 



2. RHUS L. Sumac. 



Rachis of the leaf wing-margined...^ 1. R. copallina. 



Rachis of the leaf not winged. 



Foliage and twigs velvety-pubescent 2. R. hirta. 



Foliage and twigs glabrous 3. R. glabra. 



1. Rhus copallina L. Dwarf sumac. 

 Woods or open fields, preferring dry situations; common. July. Eastern U. S. 



A shrub, usually 1-2 meters high; leaflets glabrous on the upper surface. Sometimes 

 known as black sumac. 



2. Rhus hirta (L.) Sudw. Staghorn sumac. 

 Dry rocky soil; frequent. June. Eastern N. Amer. (R. typhina L.) 



This species has orange-colored wood and is ordinarily a shrub 2-5 meters high. 



8. Rhus glabra L. White sumac- 



Dry soil; common. July. Eastern N. Amer. 



A shrub 1-3 meters high. Known also as scarlet or smooth sumac. The leaves, like 

 those of other species, are sometimes used for tanning. 



