Part 1, 1909] ZANNICHELLIACEAE 19 
_ Potamogeton varians Morong ; Fryer, Jour. Bot. 27: 33. 1889. (Potamogeton gramineus spath- 
uliformis Robb. in A. Gray, Man, ed. 5. 487. 1868. Potamogeion spathulaeformis Morong, Mem. 
Torrey Club 32: 26. 1893.) This is apparently a mere form of the preceding. The lack of mature 
fruit has suggested that it may be a hybrid (between P. angustifolius and P. heterophyllus?). 
11. Potamogeton heterophyllus Schreb. Spicil. Fl. Lips. 21. 1771. 
Potamogeton Proteus heterophylius Cham, & Schlecht. Linnaea 2: 202. 1827. 
Potamogeton gramineus graminifolius Fries, Novit. ed. 2. 36. 1828. Not P. gramineus L. 1753. 
Potamogeton gramineus myriophylius Robb. in A. Gray, Man. ed. 5. 487. 1867. 
Potamogeton gramineus Coulter, Man. Rocky Mt. Bot. 363. 1885. Not P. gramineus L. 
Polamogeton heterophyllus maximus Morong, Bull. Torrey Club 13: 155. 1886. 
Potamogeton heterophylius longipedunculatus Morong, Mem. Torrey Club 3?: 24. 1893. 
Potamogeton heterophyllus myriophylius Morong, loc. cit, 1893. 
Poltamogeion heterophyllus minimus Morong, loc. cit. 25. 1893. 
An exceedingly variable, and as here treated perhaps an aggregate species. Stem 
simple, or simply or dichotomously branched, sometimes up to 4 m. long; floating leaves 
petioled, sometimes wanting; blades coriaceous, ovate or elliptic-ovate, mostly acute or 
mucronate at the apex, narrowed or subcordate at the base, 1.5-6 cm. long, 0.7-2.5 cm. 
wide; petioles 3-10 cm. long, in some forms much longer ; submerged leaves sessile, or the 
upper petiolate, translucent, varying from linear and capillary in some rare forms to lance- 
olate or oblanceolate in the commoner forms, mostly 7-nerved, or with fewer nerves, 1-2.5 
em. long, 2-18 mm. wide; stipules mostly spreading, obtuse, 1.5~-2.5 cm. long; spikes 
cylindric, 2-4 cm. long, many-flowered; peduncles mostly twice as thick as the stem, 
from 4 cm.-1 m. long; nutlets slightly compressed or pitted, obscurely 3-keeled; embryo 
an incomplete spiral, the apex pointing directly towards the base or inside it. 
Type LOCALITY: Lindenthal, Germany. 
DISTRIBUTION : Throughout North America, except Central America and the West Indies; in 
the larger Bahama Islands; also in Europe. 
ILLUSTRATIONS: Linnaea2: pl. 5, f. 16,¢, f, g and h: Engler, Pflanzenreich 41: f. 20 a-c (as 
P. gramineus) ; Britt. & Brown, Ill. Fl. f 450; Mem. Torrey Club 3?: pl. 34; Fl. Dan. pl. 1263. 
12. Potamogeton alpinus Balbis, Misc. 13. 1804. 
Potamogeton rufescens Schrad.; Cham. Adnot. Fl. Berol. 5. 1815. 
Potamogeton obrutus‘Wood, Class Book 178. 1845. 
Whole plant reddish; stem simple or sparingly branched; floating leaves petioled, 
sometimes wanting; blades coriaceous, ovate-spatulate, obtuse at the apex, narrowed at the 
acute base, 2.5-3.5 cm. long, 0.8-1.3 cm. wide; petioles as long as the leaf-blades or longer ; 
submerged leaves sessile, translucent; blades oblong-lanceolate or linear-lanceolate, 7-25 
cm. long, as wide as or wider than the floating leaf-blades; stipules obscurely 2-keeled, axil- 
lary and free from the petiole, 2-3.5 cm. long; spikes cylindric, 1.5-3.2 cm. long, rarely 
becoming branched, many-flowered and -fruited; peduncles 5-18 cm. long, as thick as the 
stem; nutlets smooth, or pitted when young, 3-keeled, the middle keel obscurely winged and 
more prominent than the smaller lateral keels; embryo an incomplete spiral, the apex 
pointing towards the base or rarely inside it. 
TYPE LOCALITY: Lake Chamollet, France. 
DISTRIBUTION : Labrador west to the Yukon, south to Florida and California. 
ILLUSTRATIONS: Fl. Dan. £/. 1635; Mem. Torrey Club 32: p/. 30; Britt. & Brown, Ill. Fl. fi 
147 ; Engler, Pflanzenreich 41: f. 17; Engl. Bot. pl. 1286 (as P. fluitans). 
13. Potamogeton americanus Cham. & Schlecht. 
Linnaea 2: 226. 1827. 
Potamogeion fluitans Roth, Fl. Germ. 1:72, in part. 1788. 
Potamogeton natans Thunb. Prodr. Fl. Cap. 32. 1794. Not P. natansl. 1753. 
Potamogeton natans fluitans Torr. Fl. N. Y. 2: 254, 1843. 
Potamogetion lonchites Tuckerm. Am. Jour. Sci. IT. 6: 226. 1848. 
Potamogeion planitagineus jamaicensis Griseb. F1. Brit. W. Ind. 506. 1861. 
Potamogeton lonchites noveboracensis Morong, Mem. Torrey Club 3: 20. 1893. 
Potamogeton americanus noveboracensis A. Benn. Jour. Bot. 31: 297. 1893. 
Potamogeton rectifolius A. Benn. Jour. Bot. 40: 147. 1902. 
Potamogeton pennsylvanicus portoricensis Graebner, Symb. Ant. 4:73. 1903. 
Stems slender, much branched; floating leaves petiolate ; blades coriaceous, elliptic, 
2-12 cm. long, 0.5-3.5 cm. wide, 17-24-nerved, acute at the apex and rounded or rarely 
