PONDWEED FAMILY. 75 
26. Potamogeton lateralis Morong. Opposite-leaved Pondweed. (Fig. 167.) 
Potamogeton lateralis Morong, Coult. Bot. Gaz. 5: 
51. 1880 
Stems filiform, much branched. Floating 
leaves on sterile shoots only, coriaceous, ellip- 
tic, obtuse, 4’’-5’’ long, 1//-2’’ wide, 5-7- 
nerved, the nerves deeply impressed beneath, 
usually in I-3 opposite pairs which stand at 
right angles to the stem, on petioles 3//—10’’ 
long; submerged leaves linear, acute, 1/-3/ long, 
//-44/’ wide, 1-3-nerved, 2-glandular at the 
base, but the glands small and often obsolete; 
stipules small, hyaline, many-nerved, obtuse, 
deciduous ; peduncles and floating leaves lateral, 
with a peculiar appearance, widely spreading 
at maturity, sometimes recurved, thickening in 
fruit, 4’’-15’’ long; spikes capitate or often in- 
terrupted, 3—4-flowered; fruit obliquely obovoid, 
about 1’’ long, lenticular, the back much curved 
and 2-grooved, the face arched and surmounted 
by the nearly sessile stigma; curve of the em- 
bryo oval, its apex nearly touching its base. 
In lakes and slow streams, eastern Massachusetts to Michigan. Proliferous shoots at the sum- 
mit of the stem and on the upper branches appear late in the season, as the plants are beginning to 
decay. July-Aug. 
27. Potamogeton pusillus 1. Small Pondweed: (Fig. 168. ) 
Potamogeton pusillus I, Sp. Pl. 127. 175 
“I 
oO 
Stems filiform, branching, 6/-2° long. 
Leaves all submerged, linear, obtuse and mu- 
cronate or acute at the apex, 2-glandular at the 
base, 1/-3’ long, about %4’’ wide, 1-3-nerved, 
the Tateral nerves often Biers stipules short, 
hyaline, obtuse; peduncles usually 3//—-9’’, or 
rarely 3 long; spikes 3-10-flowered; fruit ob- 
liquely ellipsoid, about 1/” long and 14’ thick 
curved and 2-grooved on the back or sometimes 
with 3 distinct keels, the face slightly arched, 
beaked by a straight or recurved style; apex of 
the embryo slightly incuryed and pointing ob- 
liquely downward. Propagative buds occur in 
greater or less abundance. 
In ponds and slow streams, New Brunswick to 
British Columbia, south to Virginia, Texas and 
California, Also in Europe. July-Aug. 
Potamogeton pusillus Panormitanus ( Biv.) Morong, Mem. Torr. Club, 3: Part 2, 46. 1893. 
otamogeton Panormitanus Biv. Sic. Pl. 1806-7. 
Uppermost leaves subcoriaceous, spatulate, opposite, divaricate, 3-5-nerved, 4''-5'’ long, taper- 
ing into a broad petiole as long as the blade. Ottawa, Ontario. Also in Europe. 
Potamogeton pusillus polyphyllus Morong, Coult. Bot. Gaz. 5:51. 1880. 
Stem 3/-5’ long, divaricately branching from the base and very leafy throughout; leaves 
very obtuse, 3-nerved. Plant not known to flower, but abundantly prov ided with propagating buds 
which are thickened, hardened and closely invested by imbricated leaves. Eastern Massachusetts. 
Potamogeton pusillus Sturrockii A. Bennett in Hook. Stud. Fl. Ed. 3, 435. 1884. 
A rare form w ith delicate bright green pellucid leaves, 1’-3' long, obtuse or often apiculate at 
the apex, less than 1'’ wide, sometimes 5-nerved; fruit much Se alter than that of the type, short- 
beaked. Eastern Massachusetts. Also in Europe. 
