70 XEROPHYTES, HYDROPHYTES, ETC. [cH. 
(Fig. 24), Brachypodium, Nardus (Fig. 26). In Psamma 
arenaria the lower bands join into a continuous layer. 
In the following there is a band like a girder above 
and below each bundle, and contiguous with it, joining 
it to the epidermis above and below—Leersia, Phlewm 
pratense, Calamagrostis Epigeios, Bromus erectus, Xe. 
Giintz points out that xerophilous grasses are apt to 
have upright, narrow (Figs. 26—28), grooved or folded 
leaves, with strong cuticle, and marked motor-cells when the 
leaves open. It is in grasses of this kind, especially such 
as inhabit dry sandy districts, that the subulate, solid or 
grooved leaves shown in Figures 18, 19 occur—e.g. Festuca 
ovina and its varieties, Aira flecuosa, Nardus stricta, &c. 
The epidermal cell-walls are sinuous, the stomata pro- 
tected—e.g. on the flanks of ribs and in grooves—and 
waxy or hairy coverings occur. Colourless water-storing 
cells are apt to occur between or around the vascular 
bundles, and the chlorophyll-tissues tend to be dense 
and well protected inside the leaf: strongly developed 
bast-sclerenchyma is also frequent (Fig. 18). 
In shade-grasses, on the other hand, and in hygro- 
philous species, the leaves are as a rule flat, with thin 
epidermal cell-walls, which haye plane sides, free stomata, 
and no wax &c. Water-storing tissue (apart from tropical 
species) 1S sparse or absent, and the chlorophyll-tissues 
have well aerated lacunar spaces. Bast-sclerenchyma is 
in these cases feebly developed. 
In the following chapter I have brought together some 
of the principal anatomical features, in such form that the 
characters can be. employed in checking other determina- 
