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 gii-der above 

 and below each bundle, and contiguous with it, joining 

 it to the epidermis above and below — Leersia, Pfdeuni 

 pratense, Galamagrostis Epigeios, Bromus erectus, &c. 



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 Jlewuosa, 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) is 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- 



