CYPERACE^. 387 



** Leaves all submersed, 



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

 at the base, sessile and clasping. P. densnm Schw. not oi Linn. P. criS' 

 pum Pursh. 



Lakes, &c. Can. toPenn. Aujr. '\. — <S/'em 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. %. — Stem long, 

 branched. Leaves large, very pellucid ancL 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. 



1. P. zosterifolinm Schumach. : leaves all linear and grass-hke, pellucid, 

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

 on longish thick peduncles, P. compressum Torr. PL 



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



J)ressed , almost winged. Leaves 3 — 6 inches long, very narrow. Spadix 6 — 9 

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



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

 pellucid ; spadix oblong, few-flowered, somew^hat interrupted, much shorter 

 than the peduncles. 



Crooked Lake, N. Y. Dr. Sartwell. Aug. %. — Stem branching, slender, 

 flexuous. 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. paucijlorum Pursh. : leaves sessile, narrow-hnear, flat ; lower al- 

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

 gramineum Mick. 



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. peciinatum Linn. : leaves distichous, setaceous, alternate, sheath- 

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

 Mich. 



Ponds. Can, to Virg, June. %.—S(em filiform, much branched. Leaves 

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

 rupted, on an elongated peduncle. Fennel-leaved Pondvxed 



Subclass IL— GLUMACEALS, 



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

 cate colorless or herbaceous scales. 



Order CXLVI. CYPERACE^.— Sedges. 



Flowers often monoecious or dioecious, consisting of imbri- 

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



