THE STEM. 
35 
jinnicatioii between tliem and the root, conducting to tliem the 
animal and vegetable substances, salts, and earthy matter, 
which the radicles by their spongioles imbibe for the nourish- 
ment of the plant. The influence of light and air, through the 
medium of the stem, is conveyed from the leaves to the root. 
Stems have a provision for a symmetrical arrangement of 
leaves and branches ; nodes (from nodus ^ a knot), or points where 
leaf-buds are produced, being placed at regular intervals. JSTo 
such provision occurs in roots, which branch out irregularly, 
according to the nature of the soil. The intervals between the 
nodes are called internodes. In the internodes, the fibers of 
the s\em are parallel; but at the nodes, the inner fibers are 
sent off laterally to form leaf-stalks. The nodes have an in- 
timate connection with the formation of all leaves and Imds / 
they are the points from which these organs are developed. 
The stem in the embryo plant has its nodes, to the first of 
which the cotyledons are attached ; at the next node above, we 
find the primordial leaves. The distance between the nodes 
determines the distance between the leaves ; they may be so 
short as scarcely to be perceptible, or they may be wholly ob- 
literated, or suppressed, and the leaves brought close together, 
in bunches, or arranged in whorls round the stem, or two may 
be situated on opposite sides of the stem. It is a general law 
in the arrangement of leaves and branches, that they are dis- 
posed S2)irally^ in a line winding round the stem or axis^ like 
the threads of a screw, though this arrangement is often inter- 
rupted by various causes. 
41. All flowering plants have stems in some form 
or other. Those which have conspicuous stems are 
said to be caulescent (from caulis^ a stem), as in trees, 
shrubs, and most annual plants. The caulis is either 
simple, as in the white lily ; or branching, as in the 
geranium. We have, at Fig. 24, the representation of 
a caidis^ or proper stem («), a peduncle., or flower- 
stalk (J), and a petiole., or leaf-stalk (c). Culm., or 
straw (Fig. 25), is the stem of grasses and rushes. 
The culm is either without knots., as in the bulrush, 
\ointed> or knotted., as in Indian corn, gen- 2 
iculated., or bent like an elbow, as in ^^-=q:^;^_°^ 
fiome of the grasses. The bamboo, sugar- ^^^^^^^ 
cane, and various species of reeds, have 
stems of the culm kind ; some of them, particularly the bam- 
boo, are known to attain the hight of forty feet. Bcape (Fig 
26, ad) is a stalk springing from the root, which bears the 
Nodes and internodes— General rule in the arrangement of leaves. — 41. Division of stems — Cauha- 
Culm — Scaue. 
