r bundles inside the ring which surrounds a
large area of the ground tissue. Two isolated bundles, one in front and
another at the back of the ground tissue, are found. The cells of the
ground tissue lying just inside the vascular bundles are all very much
thickened. (See figs. 33 and 34.)

[Illustration: Fig. 36.--Transverse section of the stem of Eragrostis
interrupta. x 25]

[Illustration: Fig. 37.--Transverse section of the stem of Panicum
flavidum. x 15]

[Illustration: Fig. 38.--Transverse section of a portion of the stem of
Panicum flavidum. x 70

1. Epidermis; 2. sclerenchyma; 3. vascular bundle.]

The stems of _Panicum Isachne_ and _Eragrostis interrupta_ are hollow.
The stem of the former is circular in outline in cross section, though
wavy. There is a sclerenchymatous ring close to the epidermis but
separated from it by a few layers of parenchyma. One set of bundles is
imbedded in the band, and another set just touches the inner border of
it. A third series is disposed around a fairly large amount of ground
tissue, which may or may not have a cavity in the centre. The stem of
_Eragrostis_ _interrupta_ has more or less the same structure, but the
cortex has air spaces here and there. Other minor differences may be
seen on referring to figs. 35 and 36.

[Illustration: Fig. 39.--Transverse section of a portion of the stem of
Panicum colonum. x 70

1. Epidermis; 2. sclerenchyma; 3. vascular bundle.]

The stems of grasses growing in wet or marshy situations differ in
structure from those detailed above. As examples the stems of _Panicum
flavidum_, _Panicum colonum_, _Panicum Crus-galli_ and _Panicum
fluitans_ may be considered. The stem of _Panicum flavidum_ is broadly
ovate in cross section with a flat front and is more or less solid,
though occasionally the parenchymatous cells in the centre get broken.
Two rows of vascular bundles surround a fairly large amount of
parenchymatous cells of the ground tissue. There is a continuous ring of
sclerenchyma separated from the epidermis by a fairly broad cortex. The
cortex has a number of fairly large air-cavities separated by bands of
parenchymatous cells. Within the sclerenchymatous band lie small
vascular bundles at regular intervals just towards the cortex. A few
isolated bundles are in contact with the inner border. (See figs. 37 and
38.)

The stems of _Panicum colonum_, _Panicum stagninum_ and _Panicum
Crus-galli_ have in their centre in the ground tiss