LEAF EXPOSURE TO 
SUN AND AIR ~ 143 
in the figure above mentioned) are found in the so-called 
root-leaves of plants. 
FIG. 110.— Opposite Leaves of Deutzia, as 
arranged on a Vertical Branch. 
Good examples of these are the 
dandelion, chicory, fall 
dandelion, thistle, hawk- 
weed, pyrola, plantain. 
How are the leaves of 
these plants kept from 
shading each other? 
‘151. Much- Divided 
Leaves. — Not infre- 
quently leaves are cut 
into slender fringe -like 
divisions, as in the carrot, 
tansy, southernwood, 
wormwood, yarrow, dog- 
fennel, cypress-vine, and many other common plants. This 
kind of leaf seems to be adapted to offer considerable 
surface to the sun without cut- 
ting off too much light from 
other leaves underneath. Such 
a leaf is in much less danger of 
being torn by severe winds than 
are broader ones with undivided 
margins. ‘The same purposes 
are served by compound leaves 
with very many small leaflets, 
such as those of the honey- 
locust, mimosa acacia (Fig. 113), 
and other trees and shrubs of the pea family. 
Fie. 111. — Leaf-Mosaic of a 
Campanula. 
What kind 
of shade is produced by a horse-chestnut or a maple tree 
compared with that of a honey-locust or an acacia ? 
