88 



ZANNICHELLIACEAE 



12. Potamogeton praelongus Wulf. 

 White-stemmed Pondweed. Fig. 184. 



Potamogeton praelongus Wulf. in Roem. Arch. 3: 331. 1S05. 

 Stems white, flexuous, flattened, much-branched, 

 sometimes 3 m. long. Leaves all submerged, oblong 

 or oblong-lanceolate, 5-25 cm. long, 15-30 mm. wide, 

 amplexicaul, bright green, with 3-5 main nerves ; 

 stipules white, scarious, obtuse, commonly closely 

 embracing the stem ; peduncles 1-3 dm. long, erect, 

 straight, about as thick as the stem ; spikes cylindric, 

 1-4 cm. long, thick ; nutlets smooth, 1-keeled or 

 sometimes with 2 lateral and less conspicuous keels ; 

 embryo an incomplete spiral, the straight apex point- 

 ing toward the apex. 



Growing in deep water and widely distributed over the 

 cool temperate regions of the northern hemisphere. On the 

 Pacific Coast ranging from British Columbia southward 

 through the Boreal Zones to the southern Sierra Nevada, 

 California. Type locality: Europe. 



13. Potamogeton richardsonii (A. Benn.) 



Rydb. 



Richardson's Pondweed. Fig. 185. 



Potamogeton perfoliatus richardsonii A. Benn. Journ. Bot. 27: 



25. 1889. 

 Potamogeton richardsonii Rydb. Bull. Torrey Club 32: 599. 



1905. 



Stems branched. Leaves all submerged, long- 

 lanceolate from a cordate-clasping base, acuminate, 

 3-11 cm. long, wavy, pale bright green; stipules con- 

 spicuous, at least as shreds; peduncles 5-15 cm. 

 long, thickened upward and somewhat spongy ; spikes 

 cylindric, 15-35 mm. long; nutlet irregularly obovoid, 

 4 mm. long, obscurely 3-carinate on the back, the 

 sides with a shallow indentation that runs into the 

 face ; style nearly facial. 



Widely distributed over the cool temperate regions of 

 North America. On the Pacific Coast ranging from British 

 Columbia to the Sierra Nevada. California. Mainly confined 

 to the Boreal Zones. Type locality: "along the Great Lakes." 



14. Potamogeton foliosus Raf. 

 Leafy Pondweed. Fig. 186. 



Potamogeton foliosus Rai. Med. Rep. II. 5: 354. 1808. 

 Potamogeton pauciHoriis Pursh, Fl. Am. Sept. 121. 



1S14. 

 Potamogeton foliosus calif amicus Morong, Bot. Gaz. 



10: 254. 1885. 

 Potamogeton californicus Piper, Contr. Nat. Herb. 11: 



98. 1906. 



Stems flattened, leafy, very rarely with 

 propagating buds. Leaves all submerged, 

 linear, 1.5-8 cm. long, 0.5-2 mm. wide, obtuse 

 or more or less pungent at apex, 3-5-nerved, 

 the midrib prominent ; stipules axillary and 

 free from the leaf bases, 15-25 mm. long, ob- 

 tuse or acute ; spikes few-flowered, usually not 

 more than 12 nutlets maturing ; peduncles 

 usually 1-2 cm. long, as thick or thicker than 

 the stem ; nutlets pitted, 3-keeled, the middle 

 keel winged and more or less dentate ; embryo 

 an incomplete spiral, the apex pointing toward 

 the base or outside it. 



In rather shallow, still or slowly running water; New Brunswick to British Columbia, south 

 West Indies and Mexico. On the Pacific Coast it is found mainly in the Sonoran Zones from 

 Washington to southern California. Type locality: Carolina. 



to the 

 eastern 



