524 CXXXVII. NAIADACE^. Potamogeton. 



more) : filament slender, often elongated ; anther 4-Yalved, valves 

 spreading. 9 Perianth ; style filiform ; stigma 2 — 3-fid ; capsule 

 1 -seeded. — Fls. axillarij. 



xs. Canadensis. Michx. (Canlinia Ilexilis. Willd. Fluvialis flexilis. 

 Ptrs.) Water Ni/mph. — Si. filiform, casspitose, diehotomously branching; 

 ;r5. opposite or fasciculate in 3s, 4s or 6s, at the nodes, linear, obscurely denticu- 

 late, spreading, 1-veined. — A slender, flexible, rather erect, submersed aquatic 

 plant, Can. to N. J. and W. States, consisting of tufts of thread-like, knotted 

 stems 6 — 12' long. Leaves h — 1' long, ^" wide, sessile and sheathing at base. 

 Flowers solitary, sessile, axillary, very small, the fertile ones consisting of an 

 oblong ovary tipped with a filiform style, with 2 — 3 stigmas at simimit. Aug. 

 0. (^Caulinia fragilis. Willd.) SI. and lis. rather rigid, the latter mostly 

 opposite and recurved. 



3. Z ANNICHELLIA. 



In honor of Zannichelli, an eminent botanist of Venice. 



Flowers c?. — cf Stamen 1 ; filament elongated. 9 Calyx mono- 

 pliyllous ; corolla ; ovaries 4 or more, each with a single style and 

 stigma, and becoming in fruit an oblong, incurved, subsessile acheuium. 



Z. PALUSTRis. Honi Pofid-urcd. 



S/. fililbrm, floating; Zrs. opposite, linear; a7ith. 4:-cel\ed] stig. entire; acJi. 

 toothed on the back. — In pools and ditches, N. States. Stem round, .smooth, 

 1 — 2f long, branching, leafy. Leaves grass-like, 2 — 3' long, sessile. Flowers 

 issuing from axillary bracts, small, 2 together, a sterile and fertile, the former 

 tonsisUng of a single, naked, erect, yellowish-brown stamen, the latter of 4 — 6 

 ovaries which are free from the inflated, one-sided, 2 — 3-toothed calyx. Jl. Aug. 



4. RUPPIA. 



In honor of Ruppi, a German botanist. 



Flowers $ , 2 together on a spadix or spike arising from the sheath- 

 ing base of the leaves ; perianth ; stamens 4, sessile : ovaries 4, 

 pedicellate, becoming in fruit 4 dry drupes or achenia. — Root '^. 



R. MARITIMA. 



A grass-like plant, in salt marshes, Mass. Stems several feet long, fili- 

 form, branched, floating. Leaves 1 — 2f long, linear and setaceous, with inflated 

 sheaths at ba.se, all immersed. The common peduncle is contorted and spiral, 

 and by winding and unwinding bears the naked, green flowers on the surface 

 of the water as it rises or falls. July. 



5. POTAMOGETOX. 



Gt. TTOTajioi, a river, yEirwj', near. 



Flowers 5 , on a spadix or spike arising from a spathe ; calyx 4- 

 sepaled ; anthers 4, alternate with the sepals ; ovaries 4 ; achenia 

 4, sessile, flattened on one or two sides. — Mostly %■, aquatic and sub- 

 mersed^ only the jlowers arising above the surface of the water. Spadix 

 [or spike) pedunculate, 3 — 10- flowered. Lvs. stipulate^ parallel-veined^ 

 lower alternate., the tipper [mostly) opposite. Fls. small., greenish. 



^ 1. Leaves of two forms, the upper floating. 



1. P. NATANsI (P. pulcher. Tackerman.) Broad-leaved Pond-weed. 



Floating; /r.v. coriaceous, oblong, or elliptic-ovate, acute or obtuse or cor- 

 date at ba.se, on long petioles, submersed ones linear-lanceolate, membrana- 

 ceous, elongated, attenuated to petioles at base, lowest reduced to mere petioles, 

 all stipulate; spikes rather dcn.se, shorter than the peduncles;//-, somewhat 

 semi-globose, roiighish, more or less carinate at the back. — A very common 

 species, in slow waters or ponds, N. Eng. ! to Wise. Lapham! Stem slender, 



