562 NAIADACE^. (PONDAVEED FAMILY). 



ans, Morong.") — N. Eng to Fla., and west-ward. Connecting with the next 

 section. (Eu ) 



§ 2. Leaves all submersed and similar, mostli/ sessile, membranaceous and di- 

 lated, lanceolate, oblong, or oval; stipules obtuse, becoming loose. 



14. P. lucens, L. Stem thick, branching, sometimes very large ; leaves 

 more or less petioled, oval or lanceolate, m?<c/-o/}a^e, often rough-serrulate, /?'e- 

 quentltj shining ; peduncles often elongated ; fruit roundish and compressed, 

 with obtuse margins, slightly keeled; embryo circularly incurved above. — 

 Ponds, N. Eng. to Fla., west to the Pacific. Aug., Sept. (Eu.) 



Var. (?) Connecticutensis, Bobbins. Stem flexuous ; leaves all sub- 

 mersed, nearly sessile, lanceolate, acuminate, crisped, not shining nor serrulate ; 

 fruit larger, distinctly keeled ; nutlet thick and hard. — Lake Saltonstall, East 

 Haven, Conn. 



15. P. prselongUS, Wulf. Stem very long, branching, flexuous; leaves 

 lance-oblong or lanceolate (sometimes 7' long), half-clasping , obtuse with a boat- 

 shaped cavity at the extremity, thence splitting on pressure; stipules scarious, 

 very obtuse ; spikes rather loose-flowered ; peduncles very long (sometimes 

 reaching 20') ; fruit obliquely obovate, compressed, sharply keeled when dry ; 

 style terminating the nearly straight face ; curve of the embryo oval and lon- 

 gitudinal. — Ponds and large rivers, N. Scotia to Mass., west to Minn, and 

 Iowa. Sept., ( )ct. — Stem white ; foliage bright green. (Eu.) 



16. P. perfoliatus, L. Stem branching; leaves orbicidar, ovate or lanceo- 

 late from a cordate-clasping base, usually obtuse and often minutely serrulate; 

 peduncles short, cylindrical; fruit irregularly obovate, obtusely margined; 

 embryo incurved in an oval. — Ponds and slow streams, common. N. Scotia 

 to Fla., Avest to Minn, and Iowa. Sept., Oct. (Eu.) 



Var. lanceolatus, Eobbins. Larger; leaves long-lanceolate from a cor- 

 date-clasping base and acuminate, wavy, 3-4^' long; peduncles thickened up' 

 w ird. — Same range as the species, and extending west to the Pacific. 



17. P. crispus, L. Stem compressed ; leaves linear-oblong, ha.U-dsi&ip'mg, 

 obtuse, serrulate, crisped-icavy, 3-nerved ; fruit long-beaked ; upper portion of the 

 embryo incurved in a large circle. — Flowing and stagnant waters, Mass. to 

 N. J. and Ya., west to western N. Y. June, July. (Eu.) 



18. P. Mystieus, ^Nlorong. Stem, very slender and irregularly branching, 

 nearly filiform (1 -3° high) ; leaves oblong-linear {^-\V long by 2 -3" wide), 

 5-7-u(iTved,fnely undulate and entire, obtuse or bluntly pointed, abruptly nar- 

 rowing at base, sessile or partly clasping ; spikes few, capitate (4-6-flowered), 

 on erect peduncles (1-2' long) ; fruit (immature) obovate, small (hardly f" 

 1 )ng), obscurely 3-keeled on the back, a little beaked by the slender recurved 

 style. — Mystic Pond, Medford, Mass. 



§ 3. Leaves all submersed and similar, mostly membranaceous and sessile, linear 



or setaceous. 

 * Stipules free from the sheathing base of the leaf 



19. P. ZOSteraefolius, Schum. Stem branching, iving-flattened ; leaves 

 linear and grass-like (commonly 4' by 1|"), abruptly pointed, ivith many fine 

 and 3 larger nerves; stipules (seen young) oblong, very obtuse; spikes cylin- 

 drical, 12- 15-flowered, not half as long as the peduncle ; fruit obliquely obovate, 

 somewhat keeled and with slight teeth on the back, the sides not impressed, 



