Class XXI. Order 



TETRAWDR1A. 



252. URTICA. 



URTICA DIOICA. L. Large stinging Nettle* 



Leaves opposite, heart-shaped clusters much 

 branched, in pairs, mostly dioecious. Sm. 



The sensible qualities of this plant are so convincing, that 

 a botanical description would hardly be necessary to identify it, 

 did not some others of the genus possess similar properties. 

 Its power of stinging resides in its minute, tubular hairs or 

 prickles, which transmit a poisonous fluid. It grows common- 

 ly in bunches about the road sides. Stem erect, obtusely quad- 

 rangular. Leaves opposite, heart-shaped, toothed. Racemes 

 axillary, in pairs, spreading, branched. Flowers small, obscure, 

 green. July, August. Perennial. 



URTICA PUMILA. L. Richweed. 



Leaves opposite, ovate, acuminate, three nerv- 

 ed, serrate; lower petioles as long as the leaf; 

 flowers monoecious, triandrous, in corymbed heads, 

 shorter than the petioles, l^illd, 



A weed about houses, distinguished by its stem, which is 

 fleshy and almost transparent. Leaves smooth and shining;, 

 regularly toothed or serrate, very distinctly three nerved, with 

 long petioles. Flowers in short axillary racemes or heads, re- 

 peatedly forked and recurved. August, September. Annual. 



253. ALNUS, 



AI/NUS SERRULATA. Willd. Common Alder. 



Leaves ohovate, acuminate, the veins and their 

 axils hairy underneath ; stipules elliptical; obtuse, 

 Willd. 



Syn. BEfULA SERRULAfA. Ait. 



