390 CRYPTOGAMIA.— RH1ZOCARPA, 



HAB. Boggy grounds. April. A span high ; sheatfu 

 of the fertile stems swelling ; teeth black. 



3. E. sylvaticum : sterile and fertile stems with com- 



pound scabrous deflexed branches. 

 HAB. Woods and low grounds. May. Branch, 

 verticill., curved downwards ; sheaths loose. 



4. E. limosum : stems branched upwards, with the 



branches about 12 in a whorl, simple, pentagonal, 

 smooth. 

 HAB. Borders of ponds, &c. July. Stems 2 — 4 

 ft. high ; sheaths with narrow acute black teeth. 



5. E. variegatum : cespitose ; stems somewhat branch- 



ed at the base, naked, scabrous, filiform ; sheaths 

 3-toothed, blackish ; teeth membranaceous, lanceo- 

 late, whitish, deciduous at the tips. 

 HAB. Borders of lakes. Aug. Stem 3 — 6 in. 

 long, 5-angled ; rough with siliceous dots. 



RHIZOCARPA. 



613. SALVINIA. 



« 



S. natans: leaves ovate, subcordate, obtuse, with fas- 

 cicles of hairs beneath, scabrous. 

 HAB. Lakes and still waters. Floating. 



614. AZOLLA. 



A. caroliniana : leaves distichous, imbricate, ovate 

 oblong, obtuse, spreading. 

 HAB. Lakes and still waters. Floating ; resembling 

 a Jungermannia ,' leav. reddish beneath. 



615. 1SOETES. 

 I. lacustris. 



HAB. Bottom of lakes. Leav. all radical, 2 — 5 in- 

 long, subulate, fleshy ,*semicylindrical . 



