NAlADACEiE. 



369 POTAMOdETON. 



4. RU'PPIA. 

 Flowers perfect, 2 together on a spadix arising from the 

 sheathing base of the leaves; perianth 0; stamens 4, sessile; 

 ovaries 4, pedicellate, becoming in fruit 4 dry drupes or 

 achenia. 



Name in honor of Ruppi, a German botanist. Root perennial. 



R. mari'tima. 



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

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

 sheaths at base, 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. Sea Teazel-grass. 



5. POTAMOGE'TON. 

 Flowers perfect, on a spadix arising from a spathe; calyx 

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

 achenia 4, sessile, flattened on one or two sides. 



Gr. TFora^oi, a river, yiiriov, near. Mostly perennial, submersed aquatics, 

 only the flowers arising above the surface of the water. Root perennial. 



* Upper leaves floating. 



1. P. NATANS. P. natans, fluitans and heterophyllum of «MfAor5. 

 Upper leaves long-petiolate, coriaceous, lanceolate, often subcordate at base, 



lower leaves submersed. Ions, membranous, linear-lanceolate. In ponds and 

 sluggish streams. Stems round, branching, 6—20 inches long accnrdmg to 

 the depth ot the water. Leaves smooth, panillel-veined, upper U — 3 inches 

 long, i— I as wide, varyin-r throuo-h all forms between elliptic-lanceolate and 

 cordate-ovate, on petioles 2—6 inches in length, often reddish, issuing from 

 bracts ; lower leaves very variable in form and length, tapering to both ends^ 

 Peduncle 2—6 inches long, thick, bearing a spadi.x just above the water, 1—2 

 inches long, with greenish flowers. June. Floating Pond-weed. 



». upper leaves cordate-ovate, lower ones all petiolate. 



/3. fliiUans ; upper leaves oblong-lanceolate, tapering at base, lower linear. 



y.heterophijllum; upper leaves e\lipt\ca.\, lower linear. Plant reduced. 



2. P. SETA'cEUM. p. p. diversifoliuni. Bart. 

 Upper Zeaces lanceolate, opposite, 5-nerved, on short petioles ; lower ones 



submerged, sessile, filiform, alternate, dense, axillary. Common in pools and 

 ditches. A very slender and delicate species, only the upper leaves arising to 

 the surface. These are 6 — 10 lines long, 1 — 2 wide, acute at each end, on 

 hair-like petioles 5—6 lines long. Spadices dense, short, 5—6 flowered. 

 July. Setaceous Pond-weed. 



* * Leaves all submersed. 



3. P. LUCENS. 



Leaves lanceolate, flat, large, the short petioles continuing in a thick mid- 

 rib ; s;?j7£es long, cylindric, many-flowered. Rivers and lakes. Distinguished 

 for its large leaves which are very pellucid, and, when dry, shining above, 

 beautifully veined, 3 — 5 inches long, acuminate, | — 1 inch wide, each with 

 a lanceolate bract above its base. Spadix 2 inches long, of numerous, green 

 flowers, on a peduncle 2 or 3 times as long, thick and enlarged upwards. 

 June. Per. Shining Pond-weed. 



