PONDWEED FAMILY. 69 
g. Potamogeton heterophyllus Schreb. Various-leaved Pondweed. 
(Fig. 150.) 
Potamogeton heterophyllus Schreb. Spicil. F. 
Lips. 21. 1771. : 
Potamogeton heterophyllus var. maximus Mo- 
rong, Mem. Torr. Club, 3: Part 2, 25. 1893. 
Potamogeton heterophyllus var. longipeduncu- 
latus Morong, Mem. Torr. Club, 3: Part 2, 24. 
1893. 
Stems slender, compressed, much branch- 
ed, sometimes 12° long. Floating leaves 
pointed at the apex, rounded or subcordate 
at the base, 8’’-4’ long, 4’’-14’’ wide, 10-18- 
nerved, on petioles 1’-4’ long; submerged 
leaves pellucid, sessile, linear-lanceolate, 
acuminate or cuspidate, rather stiff, 1/612’ 
long, 1-8’ wide, 3-9-nerved, the uppermost 
often petioled; peduncles often thickened 
upward, 1/-7’ long, sometimes clustered, 
stipules spreading, obtuse, 8’/-12’’ long; 
spikes 9//-1'4’ long; fruit roundish or 
obliquely obovoid, 1/’-14%4’ long, 14//-1// 
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 ex- 
cept the extreme north. Alsoin Europe. July—Sept. 
Potamogeton heterophyllus graminifolius (Fries) Morong, Mem. Torr. Club, 3: Part 2, 24. 1893. 
Potamogeton gramineus var. graminifolius Fries, Novit. Ed. 2, 36. 1828. 
Submerged leaves delicate, flaccid, linear, 2’-5’ long, 1'’-3'' wide. With the type. 
Potamogeton heterophyllus myriophyllus (Robbins) Morong, Mem. Torr. Club, 3: Part 2, 24. 1893. 
Potamogeton gramineus var. myriophylius Robbins in A. Gray, Man. Ed. 5, 487. 1867. 
Stems dichotomously branching, very leafy; submerged leaves delicate, about 1’ long and 2'’ 
wide, 3-5-nerved, linear or the upper oblanceolate; floating leaves elliptic or lanceolate-oblong; 
rootstock tuberous. Massachusetts, Rhode Island and Connecticut. 
Potamogeton heterophyllus minimus Morong, Mem. Torr. Club, 3: Part 2, 25. 1893. 
Stems long and almost capillary, the internodes 34 long; submerged leaves densely clustered 
on short lateral branches, !2'-1' long, scarcely %'’ wide, acuminate, 1-nerved; floating leaves '’— 
1%! long, 3''-9'’ wide, lanceolate, oval or ovate, usually clustered at the summit of the stem. Massa- 
chusetts and New Hampshire. 
1o. Potamogeton spathulaeformis (Robbins) Morong. Spatulate-leaved 
Pondweed. (Fig. 151.) 
Potamogeton gramineus var. (?) spathulaeformis 
Robbins in A. Gray, Man. Ed. 5, 487. _ 1867. 
Potamogeton spathulaeformis Morong, 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, 13-23-nerved, 1/-2%4’ long, 
6/’-13/’ wide, borne on slender petioles ; sub- 
merged leaves pellucid, spatulate-oblong or 
linear-lanceolate, 2’-4’ long, 3/’-9’’ wide, 5-13- 
nerved, cuspidate or spinescent, sessile or sub- 
sessile, often reduced to phyllodes with a very 
narrow blade and a long acumination at the 
base and apex; peduncles often thickening up- 
ward, 1/-2/ long ; stipules obtuse, faintly keeled, 
the apex slightly hooded; spikes large; fruit 
about 1’’ long, roundish or obliquely ovoid, ob- 
scurely 3-keeled, with a curved or slightly 
angled face; embryo with the apex pointing 
slightly inside of the base. 
In Mystic Pond, Medford, Mass. Also in Europe. 
Summer. 
