It] VENATION, TEXTURE, APEX 21 
Further characters of the leaves are derived from their 
texture, apex, margins, mid-ribs and venation, hairiness, and 
especially the presence and characters of the longitudinal 
ridges which run along the upper or lower surface in many 
cases. 
The venation is parallel from base to apex in nearly 
all our grasses, but such is not always the case—e.g. in 
the exotic Panicum plicatum the mid-rib, which enters the 
leaf with several vascular bundles, gives off strong and 
weak veins below, which first diverge and then run in arches 
which converge upwards: this leaf is also remarkable in 
being plaited (plicate) in vernation. In Arundo Donax 
also the veins, though approximately parallel, do not all 
run to the apex of the tapering leaf; the outer ones end 
above in the margins and are shorter than the mid-rib. 
As regards texture, the leaves of most grasses are thin 
and herbaceous; but in some they are dry and harsh to 
the touch. They are thin and dry in Agropyrum cani- 
num, Hordeum pratense, H. murinum, Avena pratensis, &c., 
very hard and leathery (coriaceous) in Psamma, Nardus, 
species of Festuca, Aira, Agropyrum junceum, Elymus, &c. 
In aquatic grasses like Glyceria, the leaf is almost spongy 
owing to the large air-chambers developed in the tissues. 
These are easily visible with a lens. 
The apex is in most cases slender and tapering— 
acuminate; but in some it is merely brought to a point 
(acute) as in Catabrosa, Glyceria and several species of 
Poa and Avena, &c., usually flat, but somewhat hooded or 
curved up in some Poas. In cases where the leaves are 
setaceous or subulate, the apex is like a thin tapering 
