SALVINIACEJE. 641 



ones dull, papillose. (Engelmann.) — In shallow depressious on the summit 

 of Stone Mountain, Georgia (Engelmann, etc.). 



3. I. Engelmanni, A. Biaun, var. Georgiana, Engelm. Leaves 10'- 

 12' long, rather slender, stomatose; spore-cases oval, with narrow velum; 

 larger spores and smaller spores smooth. — Slow-flowing water in Horseleg 

 Creek, mountains of Georgia. 



4. I. Butleri, Engelm. Dioecious; trunk nearly globose ; leaves 8-12, 

 bright green, 3' -7' long; spore-cases usually oblong, spotted, the velum very 

 narrow, or none ; ligule subulate, from a triangular base ; larger spores warty, 

 smaller spores dark brown, papillose. {Engelmann.) — Barrens of Tennessee 

 (Dr. Gattinger), and westward. 



Order 170. SALVINIACE^. 



Small floating branching plants, with two kinds of sporangia en- 

 closed in thin sporocarps, and attached to a central receptacle, one 

 kind containing a single large spore, the other numerous smaller ones. 



1. AZOLLA, Lam. 



Stems floating free, pinnately branched. Leaves distichous, imbricated, 2- 

 lobed. Sporocarps in pairs on the under side of the stem, unequal. 



1. A. Caroliniaua, Willd. — On still water, chiefly near the coast, 

 Florida, and northward. — Plant reddish, circular in outline, ^' - 1' in diameter. 

 Leaves ovate, obtuse, rounded and roughened on the back. 



41 



