156 PRACTICAL COURSE IN BOTANY 
leaf (Fig. 208) into a number of primary veins or ribs, which 
radiate in all directions like the fingers from the palm of the 
hand; hence, such a leaf is said to be palmately veined. 
Net-veined leaves — the plantain 
(Fig. 209), wild smilax, beech, dog- 
wood — are sometimes ribbed in a 
way that might lead an inexperi- 
enced observer to confound them 
with parallel-veined ones, but the 
reticulations between the ribs show 
that they belong to the net-veined 
class. 
173. Veins as a mechanical sup- 
port. — Hold up a stiff, firm leaf of any kind, like the mag- 
nolia, holly, or India rubber, to the light, having first scraped 
away a little of the under surface, and examine it with a lens. 
Compare it with one of softer texture, like 
the peach, maple, or clover. In which are 
the veins the closer and stronger? Which 
is the more easily torn and wilted? Tear a 
blade of grass longitudinally and then cross- 
wise; in which direction does it give way 
the more readily? Tear apart gently a leaf 
of maple, or ivy, and one of elm or other 
pinnately veined plant; in which direction 
does each give way with least resistance? 
What would you judge from these facts as 
to the mechanical use of the veins? 
174. Effect upon shape.— By comparing 
a number of leaves of each kind it will be seen that the 
feather-veined ones tend to assume elongated outlines (Figs. 
197, 207); the palmate-veined ones, broad and rounded forms 
(Figs. 195, 208). Notice also that the straight, unbroken 
venation of parallel-veined leaves is generally accompanied by 
smooth, unbroken margins, while the irregular, open meshes 
of net-veined leaves are favorable to breaks and indentations. 
Fic. 208.—Palmately net- 
veined leaf of wild ginger. 
Fic. 209. — Ribbed 
leaf of plantain. 
