DEVELOPMENT OF PLANTS 



407 



usual localization of the growing regions also characterizes the 

 grasses which enables them to lift up again their stems if they 

 by any means become prostrate. In case the stem becomes pros- 

 trate, the stimulus of gravity causes a renewal of growth in the 

 cells at the base of the node on the side of the stem next to the 

 ground, thus causing the stem to curve up (Fig. 282, C), You 

 can easily demonstrate this peculiar localization of growth by 

 cutting off a growing stem of grass and placing it horizontally 

 with one end embedded in moist sand and noting the curvature 



Fig. 283. Inflorescence of a grass: I, tip of stem with flowers arranged 

 in spike-like inflorescences. 2, a single spike enlarged at time of flowering. 

 4, diagram showing structure of spike. At base two starile bracts, above 

 three flowers, each enclosed by an outer firm bract and an inner more delicate 

 bract. /, lodicules. At apex of spike a sterile flower. 5, another species 

 of grass, showing the scattering of the microspores. 



of the node after a day. The leaves show wide variation in 

 structure and are doubtless one of the factors that have enabled 

 these plants to live under a variety of conditions. For example, 

 where the plants are exposed to drought or drying winds the 



