24 THE NATURAL HISTORY OF BRITISH GRASSES. 
The stem is separated into long or short lengths, called 
joints, by the intervention of nodes (knots), which are solid 
and tend much to strengthen the structure of the plant, to 
which end they will be found to be closer at the base, where 
the strain would be greatest on account of these light plants 
swaying forwards and backwards in the wind, and more 
remote upwards in the culm, from which are suspended the 
newer and more active leaves. 
Stems may vary in being quite smooth, ribbed, armed with 
bairs—which may be long or short—bristly or downy, in 
proportion as this kind of armature may be coarse or harsh, 
or fine and soft. 
The nodes again may be of a different colour from the 
culm, or, like it, may be smooth or armed in a similar man- 
ner. 
The leaves consist of the following parts :— 
The sheath, = petiole, or leaf-stalk of other plants. 
The ligule, or tongue. 
The lamina, = blade, or flat part of the leaf. 
The sheath is the footstalk of the leaf. This takes its rise 
from the nodes, one from each, arranged on alternate sides 
of the culm. The whole length of the sheath, which is 
variable, is folded around the culm, from which it can be 
loosened by unwinding without fracture, a circumstance 
which serves to distinguish the grasses from the sedges 
(Carex), as the sheath of the latter is a continuous tube, in 
which the solid and often triangular culm is inserted, not 
folded. This is a distinctive character of great importance 
to observe, inasmuch as grasses and sedges are outwardly 
much alike—indeed some species of the latter are called 
Carnation Grass—but greatly different in quality; grasses 
being for the most part highly nutritious plants, whilst 
sedges are not only usually innutritious, but, from the 
harshness of their herbage, are often a source of injury and 
annoyance to the creatures that from starvation are some- 
times doomed to eat of them. 
The blade—lamina—is the expanded part of the leaf. It 
