293 NAIADACEJ-:. rutaniojdun. 



very acute ami mucronate, narrowed to tlie eubpetiolate base : otlierwise like the 

 last, of which it is scarcely more than a variety. — Aiuer. Jourii. Sci. 2 ser. vii. 351. 

 Walker's Hivsiii {llnthruck, n. 21)2) ; in the Atlantic States, IVoni the Great Lakes to South Caro- 

 lina, but not couinion. 



13. P. puslllus, Liiin. Stem filiform, hranching: leaves narrowly linear, 1 or 2 

 inches long, rarely a line wide, often nearly setaceous, 1-5-nerved, obtuse and 

 mucronate or acute, biglandular at base and sessile ; stipules obtuse, becoming setose : 

 spikes capitate, or somewhat elongated and open, or interrupted, on slender ilatteneil 

 peduncles h to nearly 2 inches long : fruit as in the preceding, but more obscurely 

 and obtusely keeled : embryo less incurved. — Keichenb. 1. c, t. 22. 1'. (richoides, 

 Uenth. ri. Ilartw. 341. 



In iiools and ditches ; near Santa Cruz {Ilartwcg, n. 201G) and at Soda Sprin|Ts on the Upper 

 Tuolumne (Bolaiulcr), the foiin with subsetaeeous acute or cuspiilate leaves, distinf^uished as var. 

 tenuissimiis, Murt. k Koch. The typical European i'oiin occurs in the northern Atlantic States 

 and in British America. 



•h- -f- Stipules united with the s/ieathi/if/ base of the leaf: spikes interrupted. 



14. P. pectinatUS, Linn. Stem hliform, repeatedly branched : leaves very 

 narrowly linear, 2 to (i inches long, rarely over half a line broad, often setaceous, 

 1-nerveil, acute: peduncles elongated, slender: spikes \ to 2 inches long: fruit in 

 often dense verticils, large (2 lines long), obli(iuely obovate, compressed, obtusely 

 keeled, acute: nutlet very thick: emljryo spirally incurved. — lleichenb. 1. c. 11, 

 t. 10. 



Var. (0 latifolius, Robbins. Stem stouter: leaves short and broader (1 nr 2 

 inches long by a line or two broad), 3-5-nerved with luimerous transverse veinlets, 

 acute or obtuse : sheaths large, with scarious margins, exceeding the obtuse scarit)us 

 stipules. — Bot. King Ex[). 338. 



In various parts of California {Chamisso, Coulter, Douglas); Santa Barbara (J//-s. i^/wood Coo;>c/'); 

 Oregon and Washington Territory (Li/all, Hall) ; Northern Nevada and Utah ( )\'utson), and com- 

 mon in the Atlantic States as well a.-, in l*;uroi>e. The variety has been collected in King's Hiver 

 and at GuUing's Hot Spring, Lassen County (Lcininun), and in the lower Humboldt liiver 

 (iratso)i); it appears to scarcely dilier from the European marine species /'. zostiracfiis, Fries, to 

 which it might perhaps well be referred. 



15. P. marinus, Linn. Resembling narrow leaved forms of the last species, 

 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 : embryo annular. 



Var. (?) OCCidentaliS, Robbins. Often taller and less leafy : peduncles usually 

 rather short : sjjikes interrupted : nutlet slightly 3keeled. — l5ot. King Ex}). 339. 



The variety only has been collected in Tiuckee hiver and Huby Lake, Northern Nevada (JTat- 

 sail), and is apjian-ntly a eonunon species of the interior eastward to Jlontana (JliiJianhou) and 

 Colorado (//((// k ll(irlour), sometimes nearly approaching European forms. 



16. P. Robbinsii, Oakes. Stem rather stout, often much branched and fre- 

 quently Hexuuus : hiaves numerous, distichous, the close shuaths neaily covering tlie 

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

 ciliate-serrulate ; stipules obtuse, becoming setose : spikes usually several, on rather 

 stout pedicels about an inch long, loose ami more or less interrupted, about half an 

 inch long: fruit obloiig-obovate, nearly 2 lines long, keeled with a broadisii wing, 

 acutely beaked: end)ryo stout, ovally annular. — Hov. Mag. vii. 178; Robbins, in 

 dray's Manual, 490. 



In ponds and slow streams ; not yet found in California, but to he expected ; Oregon (Hall); 

 Yellowstone region (C. Richardson); eonunon in the northern Atlantic States. 



Scanty specimens of what seems to be an nndescribed spec'ies of this group have been collected 

 in Pyramid Lake (.)//,ss S. A. rininincr), without flowers or fruit. The stem is broad and flat- 

 tened ; the leaves thick, 6 inches long by 1^ lines broad, 3-nerved with transverse veinlets, con- 

 spicuously sheathing and with broad stipules. 



