CYPKRACEvE. 387 



** Leaves all submersed. 



5. P. perfoliaium Linn. : leaves oblong-ovate, obtuse, somewhat cordate 

 at the base, sessile and clasping. P. densum Schw. not of Linn. P. cris- 

 pum Pursh. 



Lakes, &c. Can. toPenn. Aug. 1\.. Stem slender, dichotomously branched. 

 Leaves an inch or more in length, appearing perfoliate, slightly waved on the 

 margin, subpellucid. Spadix few-flowered, on a peduncle of about an inch in 

 length. Perfoliate Pondweed. 



6. P. lucens Linn. : leaves elliptic and elliptic-lanceolate ; upper some- 

 times petiolate, coarsely reticulate and mucronate. 



Rivers and lakes. Can. to Car. W. to Miss. Aug. 7J.. Stem long., 

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

 many-flowered, on a thick peduncle which is sometimes shorter and at others 

 much longer than the leaves. A very variable species. Shining Pondweed. 



7. P. zosterifolium Schumach. : leaves all linear and grass-like, pellucid, 

 with three primary and many smaller nerves, acuminate ; spadix cylindric, 

 on longish thick peduncles. P. compressum, Torr. Fl. 



In water. Can. to Virg. July, Aug. T+. Stem 2 4 feet long, much com- 

 pressed , almost winged. Leaves 3 6 inches long, very narrow. Spadix 6 9 

 lines long, on short peduncles. Grass-leaved Pondweed. 



8. P. pusillum Linn. : leaves narrow-linear, 3 5-nerved, rather obtuse, 

 pellucid ; spadix oblong, few-flowered, somewhat interrupted, much shorter 

 than the peduncles. 



Crooked Lake, N. Y. Dr. Sartwett. Aug. 1\.. Stem branching, slender, 

 fleruous. Leaves 1 2 inches long, very narrow, mostly 5-nerved. Spadix 

 about 6-flowered, on a thick peduncle which is about an inch in length. 



Small Pondweed. 



9. P. pauciflorum Pursh. : leaves sessile, narrow-linear, flat ; lower al- 

 ternate ; uppermost subverticillate ; spadix capitate, 4 6-flowered. P. 

 gramineum Mich. 



Ponds and rivers. N. Y. to Car. W. to Miss. July, Aug. %.Slem al- 

 most filiform, much branched, compressed. ^Leaves 2 3 inches long, not more 

 than half a line broad. Spadix small, on a clavate peduncle about half an 

 inch long. Few-flowered Pondweed. 



10. P. pectinatum Linn. : leaves distichous, setaceous, alternate, sheath- 

 ing; stipules scarcely any ; spadix few-flowered, interrupted. P.marinum 

 Mich. 



Ponds. Can. to Virg. June. 1\- Stem filiform, much branched. Leaves 

 very numerous, giving to the plant a pectinated appearance. Spadix inter- 

 rupted, on an elongated peduncle. Fennel-leaved Pondweed 



SUBCLASS II. GLUMACEALS. 



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

 cate colorless or herbaceous scales. 



ORDER CXLVI. CYPERACE^E. SEDGES. 



Flowers often monoecious or dicecious, consisting of imbri- 

 cated solitary bracts, (scales,) rarely enclosing other opposite 



