TETRANDRIA. TETRAGYNIA. Potamogeton. 259 
tuber. Stem cylindrical, much branched, flexuose, leafy. Leaves alter¬ 
nate, slender, flatted. Blossom whitish, or dull green. E.) 
(The slender varieties supposed peculiar to salt-water ditches, which were 
once considered to constitute the species P . marinum, are found to yield 
no permanent characteristic, the same being observed in fresh water. E.) 
Fennel-leaved Pond-weed. (Welsh: Dyfr-llys gwrychddail. . E.) 
Rivers and ponds. River Waveney. Mr. Woodward. Entirely filling a 
pond at Pendarvis, Cornwall. Mr. Stackhouse. (Near the canal bridge, 
Saltisford, Warwick. Perry. Duddingston Loch, and Loch-end, near 
Edinburgh. Greville. P* May—July. 
I\ gramin'eum. (Leaves linear, tapering downwards, with solitary, 
very slender, lateral ribs: stem cylindrical, forked: flower-stalks, 
from the forks, scarcely longer than the spikes. 
E. Bot. 2253. 
Herb submersed. Stem slender, thread-shaped, wavy. Leaves grassy, 
crowded, three inches long. Stipules usually convoluted, so as to be 
narrower than the leaves. Spikes ovate, dense, generally as long as the 
stalks. Seeds almost globular, with an oblique point. Sm. E.) 
Grassy Pond-weed. Slow streams and ditches. Binsey Common: 
Ditches by the road side going to Port Meadow, Oxon. Sibthorp. 
(Observed for many years by the Rev. R. Relhan, in Cambridgeshire. 
In ditches about Rhyd Marsh, Flintshire. Mr. Griffith. In fish ponds at 
Castle Howard. Mr. Teesdale. Lakes in Fanet, Donegal. E. Murphy, 
Esq. E.) P. July. 
(P. lanceola'tum. Leaves lanceolate, membranous, entire, contracted 
at the base, with chain-like reticulations near the ribs: spike 
ovate, dense, of few flowers. 
E. Bot. 1985. 
Stems floating, slender, round, branched, with creeping roots. Leaves an 
inch and a half to two inches long, uniform, bluntish, flat, thin, with one 
rib, and several reticulated veins, tapering at the base, alternate, except 
where the flowers are situated. Stipulce narrow, lanceolate, acute. 
Flower-stalks solitary from the bosom of one stipula of the opposite 
leaves, nearly as long as the corresponding leaf, cylindrical, equal. Spike 
short, of eight, ten, or twelve small flowers. Colour of the whole 
plant dark green, or brownish olive. In the fig. above cited, the pecu¬ 
liar chain-like reticulations close to the main rib of the leaves are omitted. 
Thus is named and described in the English Botany, a plant found by the 
Rev. H. Davies in the lakes of North Wales. Sir J. E. Smith is of 
opinion that it may possibly prove to be the real P. setaceum of Linnaeus, 
as yet so imperfectly known in this country. We find in our herbarium 
specimens from Lynn y Cwn, a lake in North Wales, communicated by 
Mr. Griffith, much resembling it, but which have hitherto been esteemed 
a variety of P. natans, and when we consider the changes which these 
plants undergo from the greater or less quantity of water, and its 
stagnant or current state, we cannot but suspect the permanency of 
P. lanceolatum. 
Lanceolate Pond-weed. Welsh: Dyfr-llys cul-ddail. Mountain lakes 
in Wales and Scotland. Loch of Linthothen, Angus-shire. Mr. G. Don. 
By the bridge at Bervie, Kincardineshire. Mr. Maughan. Hook. Scot. 
P. Aug. E.) 
