8 A TEXT-BOOK OF BOTANY 
incline to broader forms than leaves pinnately veined or 
parallel-veined. Names have been given to the various leaf 
forms, as linear, lanceolate, ovate, orbicular, etc., but they 
can be learned as they are needed. In the net-veined 
leaves the margin of the blade may be more or less deeply 
toothed or lobed (Vig. 2, B); but in the parallel-veined leaves 
the margin is not at all 
toothed, in which case 
the leaf is said to be en- 
tire (Fig. 2, C). It is 
quite common also for 
net-veined leaves to 
branch, when they are 
said to be compound. 
In this case the leaf- 
blade is broken up 
into a number of small 
blades, sometimes very 
B many of them, called 
leaflets. A branching 
pinnate leaf is said to 
be pinnately compound 
Tia. 3.—Compeund leaves: A, pinnately com- (Trig. 3, A); and a 
pound leaf of black locust ; B, palmately com- branching palmateleaf, 
pound leaf of red clover, with three leaflets, 
also showing stipules. palmately compound 
(Fig. 3, B). 
12. Exposure to light.—The special work of leaves is ex- 
ceedingly important, and this work cannot be done unless 
the leaf is exposed to light. This fact explains many 
things in connection with the position and arrangement 
of leaves. Leaves must be arranged to receive as much light 
as possible to help in their work, but too intense light is 
dangerous; hence the adjustment to light is a delicate one. 
The exact position any particular leaf holds in relation to 
light, therefore, depends upon many circumstances, and 
