NAIADACE.E. 49 
nearly simple and scarcely dichotomous. Leaves all similar, sessile, 
inear, narrowed towards the base, shortly acuminate-cuspidate, with 
5 (rarely 3) longitudinal ribs without faint ones between them, mostly 
with axillary fascicles of smaller leaves. Stipules small, acuminate 
or acute, scarious, with numerous rather slender longitudinal fibres. 
Peduncles terminal between the forks of the stem (but the lower ones 
pseudo-axillary, from one of the forks being reduced to a fascicle of 
leaves), longer than the spike, usually twice or thrice as long, rather 
‘slender, slightly thickened upwards. Sepals with their lamina sub- 
orbicular. Pistils 4. Fruiting-spike cylindrical-oblong, slightly inter- 
rupted, few-flowered. Fruit rather small, brownish-olive, slightly 
‘compressed, acuminated, convex on the upper margin, on which there 
is no tooth, half oval and bluntly 3-keeled on the back, terminated 
‘by a rather short central slightly recurved beak. Plant rather dull 
green, retaining its colour when dried. 
In ponds and ditches. Apparently rare. I have found it myself 
only on Wray Common, near Reigate, where it is now extinct by 
‘drainage. Besides this, I have specimens from Stoke Heath, War- 
rington. It has been so much confounded with large forms of P. 
-pusillus that I do not venture to quote stations from which I have 
“not seen specimens. 
England, [Scotland ? Ireland ?]. Perennial. Summer. 
Very similar in general aspect to P. gramineus, but the leaves are 
‘usually longer and much more distant, the stems much more flattened 
vand less branched, the greater number of branches being reduced 
“merely to fascicles of leaves. The leaves are acuminate-cuspidate, and 
have two more ribs than those of P. obtusifolius, though the two next 
the margin of the leaf are said to be sometimes absent. The peduncles 
(exclusive of the spike) are, in fruit, } to 14 inch long, the spike 3 
to } inch, distinctly interrupted. The fruit is considerably smaller, 
“scarcely { inch long, bulging out towards the apex on the upper side, 
and with the margin forming less than a semicircle on the lower; the 
beak conspicuous, about 1 of the length of the fruit. Whether this 
be really distinct from P. pusillus, I have seen too few specimens to 
enable me to decide. 
Flat-stemmed Pondweed. 
German, Stachelspitziges Samleraut. 
SPECIES XX—POTAMOGETON PUSILLODS. Liu. 
Prare MCCCCXIX. 
Billot, Fl. Gall. et Germ. Exsice. No. 653. 
Stem subcylindrical, not compressed, filiform, subdichotomous, 
VOL. Ix. H 
