PLANT STUDIES 
ally arranged in a definite number of vertical rows. It is 
to the advantage of the plant for these leaves to shade one 
another as little as possible. Therefore, the narrower the 
leaves, the more numerous may be the vertical rows (see 
Figs. 7, 8) ; and 
the broader the 
leaves the fewer 
the vertical rows 
(see Fig. 1). A 
relation exists, 
therefore, be- 
tween the breadth 
of leaves and the 
number of verti- 
cal rows, and the 
meaning of this 
becomes plain 
when the light-re- 
lation is consid- 
ered. 
18. Relation of 
length to the dis- 
tance between 
leaves of the same 
row. The leaves 
in a vertical row 
may be close together or far apart. If they should be close 
together and at the same time long, it is evident that they 
will shade each other considerably, as the light cannot well 
strike in between them and reach the surface of the lower 
leaf. Therefore, the closer together the leaves of a verti- 
cal row, the shorter are the leaves ; and the farther apart 
the leaves of a row, the longer may they be. Short leaves 
permit the light to strike between them even if they are 
close together on the stem ; and long leaves permit the 
same thing only when they are far apart on the stem. A 
FIG. 7. 
An Easter lily, showing narrow leaves and 
numerous vertical rows. 
