cells.]

Even from the few examples dealt with above, it is obvious that the
range of variation of sclerenchyma in leaves is very great. In the
leaves of _Aristida setacea_ there is a considerable amount of
sclerenchyma whilst in some leaves such as those of _Panicum_ _colonum_,
_P. flavidum_ and _Panicum fluitans_ the sclerenchyma is reduced to its
minimum.

[Illustration: Fig. 59.--Transverse section of a part of the leaf of
Panicum fluitans. x 30

1. Vascular bundle; 2. sclerenchyma.]

In the leaves of grasses growing in dry situations the development of
sclerenchyma is generally very considerable. The grass _Aristida
setacea_ is a good example of a xerophytic grass. The sea-shore grass
_Spinifex squarrosus_ is another example of the same kind. But in the
leaves of this grass, the development of sclerenchyma is not very
considerable, but there is a great development of parenchymatous cells
free from chlorophyll within the leaf, the chlorophyll bearing cells
being confined to the upper and the lower surfaces of the leaves.

[Illustration: Fig. 60.--Transverse section of a leaf of Spinifex
squarrosus. x 10

1. Vascular bundle; 2. sclerenchyma.]

[Illustration: Fig. 61.--A portion of the transverse section of the leaf
of Spinifex squarrosus. x 60

1. Sclerenchyma; 2. vascular bundle; 3. epidermis; 4. stomata.]

The upper and the lower surfaces of the leaves of many grasses are more
or less even, but in the case of a few grasses the upper surface
consists of ridges and furrows, instead of being even. In the leaves of
_Panicum repens_ and _Eragrostis Willdenoviana_ the upper surface is
wavy and consists of shallow furrows and slightly raised ridges. But in
the leaves of _Aristida setacea_ and _Panicum fluitans_ the furrows are
deeper and the ridges are more prominent. In _Aristida setacea_ the
ridges are flat-topped and they are rounded with broad furrows in
_Panicum fluitans_.

[Illustration: Fig. 62.--Upper epidermis of the leaf Panicum Isachne. x
200

1. Cells overlying the veins; 2. cells overlying the furrows; 3.
stomata.]

[Illustration: Fig. 63.--Lower epidermis of the leaf Panicum Isachne. x
200

1. Cells overlying the veins; 2. cells overlying the furrows; 3.
stomata.]

The epidermis covering the leaves consists of elongated cells with plane
or sinuous walls, various kinds of short cells intercalated between the
ends of long cells, motor-cells and stomata. Hairs of different sorts
occur as o