364 NAIADACE^E. (PONDWEED FAMILY.) 



Var. vulgaris, Fries. Leaves 3-nerved, often obtuse, revolute and hence 

 subulate. From the Uintas to the N. Atlantic States and Canada. 



- H Stipules united with the sheathing base of the leaf: spikes interrupted. 



9. P. pectinatUS, L. Stem filiform, repeatedly branched : leaves very 

 narrowly linear, 2 to 6 inches long, rarely over ^ line broad, often setaceous, 

 l-nerved, acute : peduncles elongated, slender : fruit in often dense verticils, large 

 (2 lines long), obliquely obovate, obtusely keeled. From the Rocky Mountains 

 eastward across the continent ; also in the Pacific States. 



10. P. marinus, L. Resembling narrow-leaved forms of the last, low 

 and very leafy : peduncles much elongated : fruit much smaller (a line long) and 

 thinner, round obovate, not keeled upon the rounded back, tipped with the broad 

 sessile stigma. 



Var. (?) OCCidentalis, Eobbins. Often taller and less leafy: peduncles 

 usually rather short: spikes interrupted. Bot. King Exped. 339. Colorado, 

 Utah, Montana, and westward. 



11. P. Hobbinsii, Oakes. Stem rather stout, often branched and 

 flexuous : leaves numerous, distichous, the close sheaths nearly covering the stem, 

 linear-lanceolate, 2 to 3 inches long by 2 lines broad, many-nerved, acuminate, 

 ciliate-serrulate : spikes usually several, on rather stout pedicels : fruit obiong- 

 obovate, nearly 2 lines long, keeled with a broadish wing, acutely beaked. 

 Gray's Manual, 490. From Oregon to the Yellowstone, and common in the 

 N. Atlantic States. 



3. TBIGLOCHIN, L. ARROW-GRASS. 



Stamens 3 or 6 : anthers nearly sessile. Ovary with sessile stigmas and 

 solitary ovules, separating at maturity from the central axis into as many dis- 

 tinct pods. Herb with fibrous roots. 



1. T. maritimum, L. Bather stout, a span to 2 or 3 feet high : leaves 

 shorter than the scape, a line or two broad : raceme usually crowded, 4 to 12 

 inches long : flowers a line broad : fruit obtuse at base, b-carpelled, 1-J- to 2| lines 

 long, and about equalling the pedicels. In saline places across the continent. 



2. T. palustre, L. Slender, to l feet high: leaves less than a line 

 broad : flowers smaller : fruit attenuate at base, 3-carpelled, 2^ to 4 lines long, 

 exceeding the pedicels, separating from below upward. From the Rocky 

 Mountains eastward across the continent. 



4. SCHEUCHZERIA, L. 



Stamens 6 : anthers on slender exserted filaments. Ovary of 3 nearly dis- 

 tinct carpels, becoming divergent coriaceous sub-globose pods : stigmas flat 

 and sessile. Herb with a creeping jointed scariously sheathed rootstock. 



1. S. palustris, L. Stems a span high or less : leaves exceeding them, 

 pitted at the tip : raceme 4 to 6-flowered, with sheathing bracts, the upper 

 ones small. From the Rocky Mountains eastward across the continent; also 

 in California and Washington Territory. 



