ration: Fig. 7.--Panicum javanicum.]

=The shoot-system.=--The shoot-system varies with the duration of the
life of the plant. In annual grasses stems are in most cases erect and
even if they are not entirely so they become erect at the time of
flowering. They are attached to the soil by a tuft of fibrous roots
arising from the base of the stems. But in perennials in addition to
erect branches, creeping branches, stolons and rhizomes may occur.

[Illustration: Fig. 8.--Prop roots of Andropogon Sorghum.]

[Illustration: Fig. 9.--Aerial roots of Ischaemum ciliare.]

The stem is either cylindrical or compressed and consists of nodes and
internodes. In most grasses the internodes are usually hollow, the
cavity being lined by the remains of the original pith cells. However,
there are also grasses in which the stems remain solid throughout. In
many grasses the basal portions of stems are more leafy and the
internodes are short, but in the upper portions the internodes become
longer separating the leaves one from the other.

In young shoots the leaves grow much faster than the internodes and
consequently internodes remain small, and leaves become very
conspicuous. The youngest portions of the shoots are by this means
always well protected by the surrounding leaf-sheaths. As soon as leaves
have grown fully, the internodes begin to elongate rapidly separating
the leaves. At first growth in length takes place throughout its length
in the internode and when it gets older this elongation ceases. But,
however, the lower portion of the internode close to the node and which
is enclosed by the leaf-sheath retains its power of growth for a
considerable time.

Branches arise from the axils of leaves and when a considerable number
of the axillary buds, especially from the lower nodes, develop into
branches the plant becomes tufted in habit. In most grasses branches
grow upwards through the sheath and emerge at its mouth as aerial
branches. Such branches are called =intravaginal= branches or stems. But
in some grasses axillary buds, instead of growing straight up through
the sheath, pierce the leaf-sheath, come out and then they grow out as
branches. This may be seen in the underground stolons of _Panicum
repens_ and in the ordinary aerial branches of _Arundo Donax_. Branches
that pierce through the sheaths are called =extravaginal= branches. (See
fig. 10.)

[Illustration: Fig. 10.--Extravaginal shoots of 1. Panicum repens and 2.
A