us_ is pyramidal and the
branches are all verticillate, the lower being longer than the upper.
The branches of a panicle are usually loose, spreading or drooping in
most grasses. But in some species of grasses such as _Pennisetum
Alopecuros_ and _Setaria glauca_, the paniculate inflorescences become
so contracted that the pedicels and the short branches are hidden and
the inflorescence appears to be a spike. Such inflorescences as these
are called =spiciform panicles=. The inflorescences in several species
of Andropogon consist of racemes so much modified as to appear exactly
like a spike. What looks like a spike in these cases consists of a
jointed axis and each joint bears a pair of spikelets, one sessile and
the other pedicelled.

The name =rachis= is given to the axis of the spike, raceme and panicle,
whether the axis is the main one or of the branch. The rachis of the
inflorescence is usually cylindrical. In some grasses it is zigzag as in
_Pennisetum cenchroides_. It is very much flattened in _Paspalum
scrobiculatum_, but somewhat trigonous in _Digitaria sanguinalis_. In
very many grasses the rachis is continuous, but in a few cases it
consists of internodes or joints which disarticulate at maturity. Many
species of Andropogon have such jointed rachises. Sometimes the joints
become greatly thickened and the surface hollowed out, the spikelets
fitting in the cavities as in Rottboellia and Manisuris.

In panicles, especially when they are diffuse, the primary branches may
be disposed irregularly or in verticils on the main axis. For example in
the panicle of _Eragrostis Willdenoviana_, the branches are irregularly
disposed, whereas in _Sporobolus coromandelianus_ the branches are
verticillate. In both these grasses fleshy cushions are developed in the
axils of the branches. These swellings help to spread out the branches
especially at the time of anthesis. The branches at the top spread out
earlier than those below.

Sometimes at the base of the rachises, main or secondary, glandular
streaks are seen as in the rachises of _Sporobolus coromandelianus_.
These glands secrete a viscid juice at the time of anthesis.

[Illustration: Fig. 17.--The Spikelet of Dinebra arabica.

1 and 2. Empty glumes; 3, 4, 5, and 6. flowering glumes with flowers.]

The =spikelet= may be considered as a specialised branch consisting of a
short axis, the =rachilla= bearing a series of modified bracts, the
=glumes=, the lower pair being