672 HYDROPTERIDES. 



forking, and terminated by the short (4" -6") nodding spike; leaves about 

 6-rowed, linear-subulate, entire, spreading or recurved ; those of the spike 

 ovate, acuminate, with bristly margins. Springy sandy places, East Florida 

 (Curtiss), and Alabama (Mohr). 



ORDER HYDROPTERIDES. 

 MARSILIA, L. 



l Plants with filiform creeping stems, a whorl of 4 wedge-shaped leaves at 

 the summit of a long erect petiole, and one or more globular sporangia 

 borne on a slender stalk at the base of the petioles, each divided into sev- 

 eral partitions, which contain the larger and smaller spores. 



S. uncinata, A. Braun. Stem long ; leaves smooth or hairy ; sporangia 

 oval, compressed, half as long as the peduncle. Banks of the Mississippi 

 below Vicksburg. 



ISOETES, L. 



I. melanospora, Engelm. Small, mostly monoecious; leaves few (5- 

 10), distichous ('2' -2%' long) ; spore-cases covered by the thin edges of the 

 cavity (velum); larger spores blackish, very minutely warty, the smaller 

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

 Stone Mountain, Georgia (Engdmann, frc.). 



I. Engelmanni, A. Braun, 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. 



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 Ten- 

 nessee (Di: Gattinyer), and westward. 



