xx BOTANY. 
general and particular outlines of the blade. There is commonly 
a mid-vein (midrib) running centrally from base to apex, and 
secondary ones which run centrally (or nearly so) through the 
lobes. We have thus a pinnate venation, in pinnately-lobed leaves, 
and radiate venation, in radiately-lobed leaves. Moreover, a 
modified form of the pinnate or the radiate venation usually 
occurs in leaves which are not lobed. In grasses, sedges, and 
many other Monocotyledons the venation is longitudinal. (Fig. 
XVII.) 
The leaves of most Monocotyledons have their principal as well 
as subsidiary veins more or less parallel, while in Dicotyledons the 
LON NAL. 
RADIATE GR PALMATE/ 
Fic, XVII.—Diagrams showing principal kinds of venation. 
subsidiary veins are mostly disposed in a net-like manner; the 
formcrare hence called parallel-veined, and the latter netted veined, 
leaves. 
Size of the Blade.—The length and width of a blade of average 
size should be measured, and when there is great diversity in size 
the extremes should also be noted. 
Surface of the Blade.—The principal varieties of surface are 
the following: é 
1. Smooth, when there are no sensible projections or depressions, 
as hairs, warts, pits, etc., upon the surface. Sometimes a smooth 
surface is shining; in some cases (e.g., the cabbage) it is covered 
with a fine whitish, floury substance (2loom), and is then said to 
be glaucous, 
