year. If, on the other hand, both young leafy
branches and old branches ending in inflorescences are found mixed, it
must be a perennial grass. The presence of the remains of old leaves,
underground stolons and rhizomes is also evidence showing the perennial
character of the plant.

Grasses are eminently adapted to occupy completely large areas of land.
They are also capable of very rapid extension over large areas, on
account of the production of stolons, rhizomes and the formation of
adventitious roots.

=The root-system.=--The root-system of grasses is very striking in its
character. In most grasses, especially in erect ones, several roots all
of about the same diameter arise in a dense tuft from nearly the same
level and from the lower-most nodes of the stems. The roots are all thin
and fibrous in the vast majority of these plants, and they are tough and
wiry only in a few cases such as in the case of the roots of _Pennisetum
cenchroides_, _P. Alopecuros_, _Ischaemum pilosum_ and _Andropogon
Schoenanthus_.

On a close examination it will become evident that all the roots of a
grass plant are adventitious. Inasmuch as the growth of the primary root
is soon overtaken by other roots growing from the stem, all the roots
happen to be of the same size. Roots arise from the nodes just above the
insertion of the leaf, and they grow piercing the leaf-sheath.

[Illustration: Fig. 6.--Panicum Crus-galli.]

Grasses in which stolons and prostrate branches occur have, in addition
to the usual radiating crown of roots at the base, aerial roots growing
out of the upper nodes of the branches and fixing them to the soil. Such
roots become supporting or prop roots and are particularly conspicuous
in several stout tall grasses such as _Andropogon Sorghum_, _Zea Mays_
and _Pennisetum typhoideum_. (See figs. 8 and 9.)

All the roots bear branch-roots which originate from the inner portion
of the mother roots in the usual manner. The character and the extent of
the development of the root-system is to a large extent dependent upon
the nature of the soil and its moisture content. In light dry soils
roots remain generally stunted and in well drained rich soils they
attain their maximum development. In clayey soils roots penetrate only
to short distances. When the soil is rich and sandy roots go deeper and
extend in all directions. The root-systems of most grasses are
superficial and so are best adapted for surface-feeding.

[Illust