300 BOTANY. 



the pinnate or the radiate venation usually occurs in leaves wbicli 

 are not lobed. In grasses, sedges, and many other Monocotyledons 

 the venation is longitudinal. (Fig. 194.) 



The leaves of most Monocotyledons have their principal as well as 

 subsidiary veins more or less parallel, while in Dicotyledons the 

 subsidiary veins are mostly disposed in a net-like manner ; the 

 former are 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 Bladei — The principal varieties of surface are 

 the following : 



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 (bloom), and is then said to be 

 glaucous. 



2. Rough, when covered with raised dots or points. 



3. Hairy (pubescent), when the whole surface is more or less cov- 

 ered with hairs. The hairs are sometimes fine and soft, forming a 

 white, glossy covering as in the silky surface. When the hairs are 

 long, soft, and spreading, the surface is mllous; when short and 

 stiff, it is hispid. In some cases the hairs are confined to the margin 

 of the blade, when it is said to be ciliate. 



Color of the Blade — This is usually green, the particular shade 

 being indicated as green, light green, dark green, etc. Note care- 

 fully the difference in color (often due to hairs, etc.) between the 

 upper and under surfaces. 



Texture of the Blade.— Most leaves are thin and have » firm 

 texture (memhranaceous) ; when tough and leathery, they are coria- 

 ceous. Leaves of » considerable thickness are fleshy or suc- 

 culent. 



The Petiole. — The length, shape, surface, and color of the petiola 

 should be carefully noted. Make similar notes also upon the 

 "partial petioles" (i.e., the petioles of the leaflets) of compound 

 leaves. 



The Stipules. — These usually consist of small lobes which grow 

 out from near the base of the petiole. Sometimes they are more or 

 less attached to the stem, in some instances sheathing it, as in the 

 buckwheat, where they have united into a single sheath. 



In all cases note (a) position, (6) shape, (c) size, (d) surface, and 

 (e) color of the stipules. 



