198 TETRANDRIA. TETRAGYNIA. poTAMoaETOjr. 



7. P. crispum L. : leaves lanceolate, tapering, sessile, un- 

 dulate and serrate. Willd. Spec. I. p. 714. Smith FL 

 jBn7. I. p. 195. En^. BoL t. 1012. P m r 5 /» F/. I. p. 121. 

 Roem. ^ Schult. III. p. 511. 



Stem branched, subcompressed. Leaves an inch and a half long, 

 2 — 3 lines broad, membranaceous, acute. Sfiikea on pretty 

 long peduncles, 8 — 10-flowered. 



Hab. In Lake George, New- York. Mr. J. H. Eddy. 



8. P. compressum L. : leaves linear, obtuse, sessile ; 

 stem compressed. Willd. Spec I. p. 715. Smith FL 

 Brit. I. p. ion. Eng. Bot. t. 418. Muhl, Cat. p. 17, 

 Roem. ir Schult. III. p. 512. 



Stem much branched, thick. Leaves 2 inches long, and about 

 2 lines broad, obtuse, or abruptly acuminate. Peduncles com- 

 pressed. Flowers 4 — 6. 



Hab. In slow-flowing streams. July — August. 



9. P. paucifiorum Ph, : leaves sessile, narrovv^-linear, 

 flat; spike capitate, 4-flowered ; stem slender,terete. P ur sh 

 JF"/. I. p. 1 2 1 . Elliott Sk. I. p. 222. R o e 7n. ^r Schult, 

 III. p. 516. P. gramuieum. Mich. FL I. p. 102, 



Stem almost filiform, much branched. Leaves 2 — 3 inches long, 

 not more than half a line broad, acute. Spikes on short pe- 

 duncles, seldom perfecting more than 4 flowers. Seeds large. 



Hab. In ponds and rivers ; very common. July — August. 



10. V, pectinatum L.: leaves setaceous, distichously 

 approximate, sheathing; stipules almost wanting; spike few- 

 flowered, interrupted. Willd. Spec. I. p. 715. Smith 

 Fl. Brit. I. p. 197. Eng. BuU t. 32.3. Pursh Fl. I. p. 

 121. Roem. ir Schul). III. p. 513. V. marinum M % ch.. 

 Fl. 1. p. 102. P. exstipulatum M u h I. Cat. p. 17 ? 



Stem filiform, much branched, dichotomous. Leaves very nu- 

 merous, 4 — 6 inches long, attenuated to a fine point. Peduncle 

 generally elongated. S/i'ike about an inch long, with the flowers 

 arranged in a subverticillate manner. Seeds large in propor- 

 tion to the size of the plant. 



Hab. In ponds in the pine barrens of New-Jersey, Sec. June. 



131. RUPPIA. L. 



Calijx and Corolla 0. Seeds 4, pedicellate. Gen. 

 pi. 235. Nutt. Gen. I. p. 111. Juss, p. 19. Lam, 

 111. t. XC. f. 1. Roem. ^ Schult. Gen. 611. 

 Nat. Ord. Naiades Juss. Fluviales Rich^ 

 (Ho ok. J An aquatic, plant. Flowers on a spadir 



