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© Seen 
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428 THE NAIAD FAMILY. [Potamogeton. 
through ; from 1 to 14 inches long by fully an inch broad. Stipules as 
in the preceding species, but soon disappearing. Spike of flowers 
seldom above 6 or 8 lines long. . 
In rivers and ponds, all over the northern hemisphere, and in Australia. 
Generally distributed in Britain. 1. swmmer. 
6. P. crispus, Linn. (fig. 963). Curly P.—-One of the most marked of 
the alternate-leaved species. Leaves all submerged and thin, narrow- : 
oblong or broadly linear, obtuse, shortly tapering at the base, 1 to 2 
inches long, 3 to 5 lines broad, always waved and sinuated on their 
edges, and marked by 1 strong midrib and 2 parallel slender nerves at 
some distance from it, but connected with it by a few transverse veins, 
Spikes small, consisting of about 3 to 6 flowers, at some distance from ~ 
each other. 
In ponds, streams, and ditches of the northern hemisphere, except 
the extreme north, and in Australia. Commonin Britain. Fl. summer. 
7. P. densus, Linn. (fig. 964). Opposite P.—Readily known by its 
numerous short leaves, all opposite, and arranged in 2 rows on the 
opposite sides of the stems; they are all submerged and thin, broadly 
lanceolate, 6 to 9 lines long, folded and clasping the stem at their base, 
with a strong midrib and 2 fainter parallel nerves, connected by a few 
transverse veins, Stipules only under the peduncles or branches. Pedun- 
cles very short, turned down after flowering, bearing a head of 2 or 3 
flowers only. Ripe carpels rather large, rounded, and smooth. 
In shallow pools, and ditches, of Europe, except the extreme north, 
temperate Asia and America. Common in Britain. Fl. swmmer, 
8. P. obtusifolius, Mert. and Koch. (fig. 965). Obtuse P.—Stems 
slender. Leaves all submerged, alternate except under the branches, 
14 to 3 inches long, and 1 to 2 lines broad, obtuse or scarcely acute, 
usually 3-nerved, with a very few transverse veins. Sheathing scarious 
stipules often persistent under the branches, but sometimes mostly 
fallen away. Peduncles not long. Spikes usually 4 inch or rather 
longer, not very dense. Nuts broadly ovoid, about 14 lines long, nearly 
smooth or with a prominent often rugose dorsal rib and straight beak. 
Seed much curved. 
In pools, ditches, and still fresh waters, over a great part of the globe. . 
Common in Britain. Ll. summer. The Linnean names P. gramineus and é 
P. compressus have been so variously applied by their author and others, . 
to this and the following species, and to some states of P. heterophyllus, 
that the names given by German botanists are now generally adopted. 
9, P. acutifolius, Linn. (fig. 966). Acute P.—Very near P. obtusi- 
jolius, with the same habit and stipules. Leaves as in that species, 
narrow-linear, but semi-amplexicaul and very acute, with 1 prominent 
central nerve, and often 1 on each side not connected by transverse 
veins, but occasionally numerous exceedingly fine longitudinal ones 
may be seen under a lens. Spikes usually shorter than in P. obtuse- 
folius. Nuts the same, but with a recurved beak. 
Appears to be as generally spread as P. obtusifolius, and perhaps more 
common in Britain. Fl. summer. Both this and the preceding species 
were included in early editions as robust varieties of A. pusilus. d 
[P. zosterifolius, Schum., is a very closely allied plant with broad — 
almost winged stems, abruptly acuminate leaves, and 3-ribbed nuts.] : 
10. P. pusillus, Linn. (fig. 967). Slender P.—Distinguished from — 
