144 THE BEAUTIES OF NATURE. CHAP. 
and ,’;. In the first the leaves are generally | 
broad, in the @ arrangement they are elliptic, 
in the >; and more complicated arrangements 
nearly linear. The Willows afford a very 
interesting series. Salix herbacea has the 4 
arrangement and rounded leaves, Salix caprea 
elliptic leaves and 2, Salix pentandra lancet- 
shaped leaves and 3, and S. incana linear leaves 
and a +; arrangement. The result is that 
whether the series consists of 2, 3, 5, 8, or 13 
leaves, in every case, if we look perpendicu- 
larly at a twig the leaves occupy the whole 
circle. 
In herbaceous plants upright leaves as a 
rule are narrow, which is obviously an advan- 
tage, while prostrate ones are broad. 
AQUATIC PLANTS 
Many aquatic plants have two kinds of. 
leaves ; some more or less rounded, which 
float on the surface; and others cut up into 
narrow segments, which remain below. The 
latter thus present a greater extent of surface. 
