16 PLANT STUDIES 
find the lowest leaves of a plant the largest and with the 
longest petioles, even when the leaves are not very close 
together on the stem. 
It must not be supposed that by any of these devices 
shading is absolutely avoided. This is often impossible and 
sometimes undesirable. It simply means that by these 
FIG. 9. A plant (Saintpaulia) with the lower petioles elongated, thrusting the blades 
beyond the shadow of the upper leaves. A loose rosette. 
arrangements the most favorable light-relation is sought by 
avoiding too great shading. 
20. Direction of leaves. Not only is the position on the 
stem to be observed, but the direction of leaves often shows 
a definite relation to light. It is a very common thing to 
find a plant with a cluster of comparatively large leaves at 
or near the base, where they are in no danger of shading 
other leaves, and with the stem leaves gradually becoming 
