858 
Potamacete. 
almost cordate. Carpels small, obtusely keeled. Stem 
branchy. P. plantagineus Ducros, P. Hornemanni Koch. 
—Stagnant water, rare; W. Y. B. Z. Glarus. 6 
coloratus Vahl. 2038. 
— Submerged Is sessile (the base often narrowed like a 
petiole), long-lanceolate (up to 10cm long); floating Is, 
when present, leathery, oblong, obtuse, cuneiform nar¬ 
rowed to a petiole. Carpels large, with a sharp keel. 
Stem gen simple. P. alpinus Balb., P. obtusus Ducr.— 
Stagnant or slowly flowing water; not common (wanting 
in T. S.). 6 rufescens Schrad. 2039. 
7 (4). Ls obtuse or acute, rather small, very slightly rough, 
the submerged Is sessile, linear-lanceolate; floating ls, 
when present (v. beterophyllus), leathery, oval or ob¬ 
long, with long petioles. Stem very branchy, flexible.— 
As the last; not common (wanting in G. T.). 6 
gramineus L. 2040. 
— Ls distinctly mucronate, rough-denticulate at the edges, 
all of the same consistency, membranous-transparent, 
all shortly petioled, or the upper sometimes with a 
longer petiole and almost floating. Stem branchy 8 
8. Ls (shining as if varnished) large (10—15 cm long), all 
of the same form and shortly petioled, oblong-lanceo¬ 
late (in b. longifolius Gay long-lanceolate, acuminate, 
20—22 cm long and 18—28 mm broad), fairly often ter¬ 
minated by a long horn-like point (v. cornutus Presl.). 
—As the last; distrib.; b. Schwarzsee, Canton Freib. 6 
lucens L. 2041. 
* 
— Ls smaller, 7—8 cm long and 10 — 12 mm broad, oblong- 
lanceolate, the upper elliptic with a petiole half as long 
as the limb, often almost floating. P. gramineus var. 
Koch, P. lucens var. Nolte, Aschers.—Reuss near Ma- 
8chwanden! Yverdon and probably other places.*) 
Zizii M. K. 2041. b 
9 (3). Carpels terminated by a long recurved beak. Ls 
wavy-crisp, finely denticulate, linear-oblong.—As the 
last; distrib. 6 .... crispus L. 2042. 
— Carpels terminating in a short point . . . 10 
10. Ls (dirty green) round-oval, oval or lanceolate, cordate- 
clasping at the base, rough-denticulate at the edges. 
Spikes short.—As the last; distrib. 6 perfoliatus L. 2043. 
— Ls (bright green) lanceolate, elongated, 90—180 mm long, 
rounded at the base, half-clasping, concave at the tip, 
smooth at the edges. Spikes gen. elongated.—As the 
last; lac alpin of Brettaye, lac d’Etalieres. 7 
prselongus Wulf. 2044. 
*) Also indicated in the French Jura and in Canton Schaffh. Nervation 
of the Is more resembling that of P. lucens than P. gramineus ! 
