THE STEMS 



point at which the plumule is arrested in its upward growth through the 

 soil, is regulated chiefly by the light-perception of the plant, and by the 

 depth at which the grain is sown. 



In shady places the tillering node is found nearer the surface than in 

 sunny open ground, and a continuance of dull weather after late sowing 

 tends to shallow tillering. 



The following measurements obtained from plants derived from 

 grains sown at carefully controlled depths illustrate the influence of depth 

 of sowing on the length of the rhizome, and the depth of the tillering node 

 below the surface. 



The arrangement and order of development of the several branches 

 may be followed by the dissection of young plants 

 in different stages of growth. 



In the resting embryo within the grain, the 

 terminal primary bud is visible with its axis and 

 two or three rudimentary leaves ; the first lateral 

 bud is also seen in longitudinal sections in the 

 axil of the coleoptile (Fig. 10). 



Ten or fifteen days after germination com- 

 mences, more lateral buds are formed, one in 

 each axil of the alternate leaves on opposite sides 

 of the primary axis (Fig. 62). Expansion of the 

 latter soon commences ; its first internode, 

 namely, that below the first lateral bud in the 

 axil of the coleoptile, always remains very short ; 

 the second, however, grows considerably, forming 

 a more or less elongated rhizome as already 

 described, the terminal bud with its lateral buds 

 being pushed upwards in the soil to the tillering 

 point. 



After the plumule has been carried upwards 



to this position, the buds in the axils of its two , 



, /.. . FIG. 61. Rhizome of three 



lowest roliage leaves develop rapidly, the plant internodes. 



