325 
ON POTAMOGETON NITENS, Weber, AS AN IRISH — 
v PLANT. 
By D. Moors, PH D., F.L.S., erc. Etc. 
(Pirate XXIII.) 
Those who have paid attention to aquatic plants know that many of 
them present different appearances at certain seasons of the year from 
that they have at others, whilst the various depth of water in which they 
happen to grow, is also calculated to alter their general appearance 
considerably. It must however be confessed that the species of 
Potamogeton admitted in the British Floras, though subject to similar 
alterations according to circumstances, have, for the most part, cha- 
racters sufficiently well marked and constant to distinguish them. 
Ireland is already credited with two, namely, P. sparganifolius, Laest., 
and P. longifolius, Gay, not hitherto discovered in England or Scot- 
land, whilst P. nitens, Weber, just discovered, makes a third, and 
forms another important link in the geographical distribution of plants 
which grow on the continent of Europe, having their only known 
British localities in the south-western counties of Ireland. 
Potamogeton nitens has long been known to inhabit parts of France, 
Germany, and Scandinavia, as may be seen by reference to Reichen- 
bach’s Icones Fl. Germanice, vol. vii. t. 34; Koch, Synop. Fl. Germa- 
nice, ed. 1, p. 675; Grenier and Godron’s Fl. France, vol. iii. p. 314, 
and Fries's Nov. Fl. Suecice, p. 34. 
The Irish plant agrees closely with Reichenbach's figures and 
description, as well as with the descriptions given in the other Floras 
just quoted, with which it has been carefully compared by myself and 
those botanical friends who have assisted me to ascertain the species. 
The following-are the principal characters of the Irish plant :—Stems 
round, slender, much branched. Leaves all membranous, transparent, 
crowded on the stem; firm, shining, and recurved: the lower lanceolate, 
semiamplexicaul, pointed at both ends, about 1i inches long by 4 inch 
in width, half folded, so as to appear channelled, and finely undulated 
at the margins. Upper leaves also submerged, broader and blunter at 
the points, narrowed at the base into a short petiole. Stipules per- 
sistent, membranous, about one-third the length of the leaf. Peduncle 
short and stout, about the length of the upper leaves, slightly thickened 
VOL. II. [NOVEMBER 1, 1864. z 
