40 CLASSIFICATION ACCORDING TO [CH. 
large air-cavities; ligule short. Leaf-base with a brown 
triangle. Margins and keel rather rough. 
These two species of Glycerta are distinguished by their shoot- 
sections and the ridges of the leaves of G. fuitans: they often occur 
in the same ditch. 
They cannot readily be confused with others on account of their 
aquatic habit, and the characters given. The only other aquatic or 
semi-aquatic species are forms of Catabrosa, Digraphis, Arundo, 
Alopecurus geniculatus, Molinia cerulea and the rare Calanagrostis. 
The ligule and flat shoots with closed sheaths alone suffice to 
distinguish it from the round and split sheathed Arwndo Phrag- 
mites; and the round shoots of Digraphis, its split sheath and firm 
leaves, suttice to distinguish it. 
Molinia also has a tuft of hairs instead of a ligule, and a split 
sheath, and its habit is different. 
Alopecurus geniculatus, with its “kneed” shoots, has a totally 
different habit from Glyceria, and its very high ridges and want of 
visible air-chambers complete the diagnosis. 
Catabrosa is a small creeping aquatic with very flaccid leaves, 
quite glabrous and soft. Also sweet-tasting. 
B. Not aquatic, and devoid of visible air-chambers in leaf 
or sheath. Often perennial, i.e. having stolons or other 
branches with no rudiments of flowers in them, and 
with relics of old leaf-bases. 
(a) Sections of sheathed leaves acute: either two- 
edged or four-edged. 
(1) Section of sheathed leaves quadrangular. “Blades of 
leaf thin and dry, sparsely hairy. Sheath quite 
entire. Woods and shady places. 
Melica uniflora, L. (Wood Melick). Lamina slightly 
tapered below, convolute. Ligule obsolete, with a stiff 
subulate process on the sheath opposite the blade- 
insertion. Ridges below, but not above. 
