16 



PLANT RELATIONS. 



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 may result 

 in a favorable 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 



