CHAPTER X. 
Leaf Arrangement for Exposure to Sun and Air; 
Movements of Leaves and Shoots. 
122. Leaf Arrangement.'— As has been learned from the 
study of the leafy twigs examined, leaves are quite generally 
arranged so as to secure 
the best possible exposure 
to the sun and air. This, 
Fic. 78. — Leaf Ar- 
Fig. 77. — Leaf Arrangement of the rangement of Euro- 
Oak. pean Beech. 
in the vertical shoots of the elm, the oak (Fig. 77), the apple, 
beech, and other alternate-leaved trees, is not inconsistent 
with their spiral arrangement of the leaves around the stem. 
In horizontal twigs and branches of the elm, the beech (Fig. 
78), the chestnut, the linden, and many other trees and shrubs, 
the desired effect is secured by the arrangement of all the 
leaves in two flat rows, one on each side of the twig. The 
rows are produced, as it is easy to see on examining such a 
1 See Kerner and Oliver’s Natural History of Plants, vol. I, pp. 396-424 
