386 MONOCOTYLEDONOUS PLANTS. 



5-nerved ; lower ones filiform ; spadix axillary, almost sessile, few- 

 flowered. P. setaceum Pursh. 



HAB. Ponds and small streams. N. S. June. If. Stems nu- 

 merous, branched, filiform. Upper leaces scarcely an inch long. 

 Spadix, 4-6-flowered. 



"* Leaves all submersed. 



5. P. perfoUatum Linn. . leaves clasping, cordate, ovate. 



HAB. Lakes, &c. Can. to Penn. Aug. L(. Stem dichoto- 

 nious. Leaves an inch or more in length, appearing perfoliate. 

 Spadix fe.w-flowered, on a short peduncle. 



6. P. lucens Linn. : leaves ovate-lanceolate, petiolate. 



HAB. Rivers and lakes. Can. to Car. Aug. 11. Stem long, 

 branched. Leaves large, very pellucid and finely veined. Spadix 

 cylindrical, many-flowered. 



7. P. densum Linn. : leaves opposite, crowded, ovate, acuminate, 

 acssile ; stem forked ; spike about 4-flowered, on very short peduncles. 



HAB. Pools, &c. Bethlehem, Penn. Schwdnitz. 



8. P. crispum Linn. : leaves lanceolate, tapering, sessile, much 

 waved, serrate. 



HAB. Lakes. Can. to'Vir. Pursh. Aug. 11. Stem long, 

 much branched. Leaves 1 1-2 inches long, 2 3 lines broad, 

 crisp to the touch. Spadix 8 10 flowered. 



9. P. compressum Linn. : leaves linear, yery obtuse, sessile ; stem 

 compressed, 4 6-flowered. 



HAB. In water. N. S. July, Aug. I/. Plant small. Stem 

 much branched, thick. Leaves 2 inches long, linear. 



10. P. paucijlorum Pursh: leafy ; leaves sessile, narrow linear, flat ; 

 the upper verticillate ; spadix capitate, 4-flowered ; stem slender, te- 

 rete. P. gramineum Mich. 



HAB. Ponds and rivers. N. Y. to Car. July, Aug. 2JL.Stcm 

 almost filiform, much branched. Leaves 23 inches long, not 

 more than half a line broad. 



11. P. pectinatum Linn. : leaves distichous, setaceous, alternate, 

 sheathing ; stipules scarcely any j spadix few-flowered, interrupted.- 

 P. marinum Mich. 



HAB. Ponds. Can. and N. S. June. U.Slem filiform, much 

 branched. Leaves very numerous, giving to the plant a pecti- 

 nated appearance. 



SUBCLASS II. GLUMACEJE. LAnd. 



Flowers destitute of a true perianth, but consisting of im- 

 bricated bracts. 



ORDER CXXXV1II. GRAMINEJS. Jms. Lind. 

 Flowers usually monoclinous, sometimes monoecious or 



