86 



ZANNICHELLIACEAE 



& 



6. Potamogeton angustifolius Berch. cc 

 Presl. Ziz's Pondweed. Fig'. 178. 



Potamogeton angustifolius Berch. & Presl, Rost. 19. 1821. 

 Potamogeton sizii Roth. Enum. 1: 531. 1827. 



Stems slender, branching. Floating leaves el- 

 liptic, 3-5 cm. long, 12-25 mm. wide, acute or 

 acuminate at apex, sometimes mucronate, nar- 

 rowed to the acute base, about 15-nerved ; petioles 

 shorter than the blades or sometimes longer ; 

 submerged leaves sessile or the upper petioled, 

 lanceolate or somewhat spatulate, pellucid, minute- 

 1\- serrulate towards the acute, 'sometimes cuspi- 

 date apex, 5-15 cm. long, 0.5-2.5 cm. wide, 

 7-nerved, sometimes with a few intermediate 

 secondary nerves; stipules 2-keeled, 15-30 mm. 

 long, obtuse, axillary and free from the petioles ; 

 spikes cjdindric, 2.5-4.5 cm. long, densely flowered; 

 peduncles as thick as the stem or thicker, 6-12 

 cm. long; nutlets smooth, 3-keeled at maturity; 

 3-4 mm. long; apex of the embryo pointing di- 

 rectly toward the base. 



Ponds and streams; Maine to Florida, Texas, and Guatemala, also in Europe 

 it has been collected at Tiajuana, Lower California. Type locality: Bohemia. 



On the Pacific Coast 



Mainl 

 fornia. 



the Boreal 

 in Europe 



Zones; Y 

 and Asia. 



7. Potamogeton alpinus Balbis. 

 Northern Pondweed. Fig. 179. 



Potamogeton alpinus Balbis, Misc. Bot. 13. 1804. 

 Potamogeton rufcscens Schrad.; Cham. Adn. Fl. Ber. 5. 

 ISIS. 



Whole plant of a reddish tinge ; stems simple 

 or branched, somewhat compressed. Floating 

 leaves spatulate or oblanceolate, obtuse at the 

 apex, narrowed at the acute base, 25-35 mm. long, 

 8-13 mm. wide, coriaceous; petioles as long as 

 the blades or longer; submerged leaves sessile, 

 oblong-lanceolate to linear-lanceolate, 7-25 cm. 

 long, as wide or wider than the floating leaves ; 

 stipules axillary and free from the petiole, ob- 

 scurely 2-keeled, 20-35 mm. long ; spikes cylindric, 

 15-35 mm. long, many-flowered; peduncles 5-18 

 mm. long, as thick as the stem ; nutlets smooth, or 

 pitted when young, 3-keeled, the middle keel ob- 

 scurely winged and more prominent than the 

 smaller lateral keels ; embryo an incomplete spiral, 

 the apex pointing towards the base, 

 ukon and I-abrador to Florida and the southern Sierra Nevada, Cali- 

 Type locality : Lake Chaniollet, France. 



8. Potamogeton heterophyllus Schreb. 

 Various-leaved Pondweed. 



Fig. 



180. 



Potamogeton heterophvUus Schreb. Spied. Fl. Lips. 21. 



1771. 

 Potamogeton gramineus of various American botanists, 



not L. 



Stem simple, or simply or dichotomously 

 branching, sometimes as long as 4 m. Floating 

 leaves present or sometimes wanting, on petioles 

 usually longer than the blades, ovate or elliptic-' 

 ovate, 2-6 cm. long, 7-25 mm. wide, acute or 

 mucronate at apex, narrowed or subcordate at 

 base, coriaceous ; submerged leaves sessile or the 

 upper petioled, 15-30 cm. long, 2-18 mm. wide, 

 varying from narrowly linear to lanceolate or ob- 

 lanceolate. translucent, 3-7-nerved ; stipules axil- 

 lary and free from the petiole, 15-25 mm. long; 

 spikes cylindric, 2-4 cm. long, many-flowered ; pe- 

 duncles mostly twice as thick as the stem, 4-10 

 cm. long or sometimes becoming much elongated ; 

 nutlets slightly compressed or pitted, obscurely 

 3-keeled ; embryo an incomplete spiral, the ape.x 

 pointing toward the base. 



Widely distributed over the northern hemisphere. On the Pacific Coast ranging from 

 to the southern Sierra Nevada, California, in the Transition and Boreal Zones. Type 

 thai, Germany. 



British 

 locality 



Columbia 

 ; Linden- 



