LEAVES 9 
cannot be covered by a general rule, except that it seeks 
to get all the light it can without danger. How leaves seek 
the light will be first considered, and later how they protect 
themselves against it. 
(1) Hortzontal position.—The ordinary position of the 
leaf is more or less horizontal. This enables it to receive 
the direct rays of light upon its upper surface, and more 
rays strike it than if it stood obliquely or on edge. Most 
leaves when fully grown are in a fixed position and cannot 
change it, however unfavorable it may become; but there 
Tic. 4.—Geranium leaves exposed first to vertical (A) and then to oblique (J) 
rays of light. 
are leaves so constructed that they can shift their position 
as the direction of the light changes, or the stem bearing 
the leaves may shift its position so that a better relation to 
light is secured (Fig. 4). If a garden nasturtium growing in 
a window be observed, its leaves will be seen facing the 
