PONDWEED FAMILY. 



Potamogeton heterophyllus Schreb. 



(Fig. 150.) 



Yuriou leaved I'undweed. 



Potamogeton heterophyllus Schreb. Spicil. I'l. 



Lips. 21. 1771. 

 Potamogeton heterophyllus var. ma.\-imn\ MM 



rong, Mem. Torr. Club, 3: Part 2, 25. 1893. 

 Potamogeton heterofiliyllux var. longipednHcu- 



liitus Morong, Mem. Torr. Club, 3: Part 2, 24. 



1893. 



Steins slender, compressed, much branch- 

 ed, sometimes 12 long. Floating leaves 

 pointed at the apex, rounded or subcordate 

 at the base, $"-4' long, 4"-i4 // wide, ic 18- 

 nerved, on petioles i'-4' long; submerged 

 leaves pellucid, sessile, linear-lanceolate, 

 acuminate or cuspidate, rather stiff, i'-6> / 

 long, i "-8" wide, 3-9-nerved, the uppermost 

 often petioled ; peduncles often thickened 

 upward, I'-j' long, sometimes clustered, 

 stipules spreading, obtuse, 8 // -i2 // long; 

 spikes <)' f -i l 4' long; fruit roundish or 

 obliquely obovoid, i // -i^ // long, y>"-\" 

 thick, indistinctly 3-keeled; style short, ob- 

 tuse, apical; apex of the embryo nearly touch- 

 ing the base, pointing slightly inside of it. 



A very variable species, occurring in different forms throughout almost all North America K. 

 cept the extreme north. Also in Europe. July-Sept. 



Potamogeton heterophyllus graminifolius (Fries) Morong, Mem. Torr. Club, 3: Part 1, 24. 189$. 

 Potamogeton gramineus\&c. graminifolius Fries, Novit. Ed. 2. 36. 1826. 



Submerged leaves delicate, flaccid, linear, 2'-$' long, i"~3" wide. With the type. 



Potamogeton heterophyllus myriophyllus ( Robbing ^ Morong, Mem. Ti.rr. Club. 3: Part a, 24. 1895. 

 Potamogeton graminens var. myriofikylhts Robbins in A. Gray. Man. I-M -*fj. 



Stems dichotomously branching, very leafy; submerged leavi about T lung and " 



wide. 3~5-nerved, linear or the upper oblanceolate ; floating leaves elliptic ">r lanceolate-oblong; 

 rootstock tuberous. Massachusetts, Rhode Island and Connecticut. 



Potamogeton heterophyllus minimus Monmg, Mem Torr. Club, 3: Part 2, 25. 1893. 

 Stems long and almost capillary, the internodes 3' -4' long; submerged leaves densely clnv 

 on short lateral branches, l A'-i' long, scarcely Y<" wide, acuminate, i nerved, fliMling lca\- 

 i ^' long, 3" -9" wide, lanceolate, oval or ovate, usually clustered at the summit of the >tcm. 

 chusetts and New Hampshire. 



10. Potamogeton spathulaeformis (Robbins Morong. 



Pond weed. (Fig. 151.) 



Spatulatt- k-avcd 



Potamogeton gra min iti\ v;ir ' .' ' ' 



Robbins in A ('.ray, Man ! 

 Potamogeton spatlnt'ld, Mem. Torr 



Club, 3: Part 2, 26. 1893. 



Stems many, branched, 2-3 long. Floating 

 leaves obovate or elliptic, abruptly acute at the 

 apex, rather thin, i3-23-nerved. i'-2#' long, 

 6 // -i3 // wide, borne on slender petioles; wib- 

 merged leaves pellucid, spatulate-oblong or 

 linear-lanceolate, 2'~4' long, 3"-9" ^ 

 nerved, cuspidate or spinescent, sessile or Mb- 

 sessile, often reduced to phyllodes with a very 

 narrow blade and a long acumination at the 

 base and apex ; peduncles often thickening up- 

 ward, i '-2' long ; stipules obtuse, faintly keeled. 

 the apex slightly hooded ; spikes Urge ; fruit 

 about i" long, roundish or obliquely ovoid, ob- 

 scurely 3-keeled, with a curved or ! 

 angled face; embryo with the apex pointing 

 slightly inside of the base. 



In Mystic Ton-! Mass. Also in Kuropc. 



Summer. 



