WHEAT 33 



within an inch of the surface of the ground, whatever may 

 have been the depth of planting. 



However, before the crown and the main or permanent 

 system of roots are formed, three short temporary roots 

 develop from the sprouted grain ; thus the depth of these 

 temporary roots depends upon the depth of planting. 

 They serve no further use after the development of the 

 numerous permanent roots originating chiefly at the crown. 

 Hence, the depth at which the wheat roots and feeds is 

 independent of the depth at which the seed is sown. 



36. Stems. — The stems or culms of wheat are hollow, 

 with closed or solid joints. The usual height is three to 

 five feet. When the straw grows to great length, there is 

 danger that the plant may " lodge " (fall), thus interfering 

 with the perfect development of the grain and making har- 

 vesting difficult and incomplete. As a rule, wheat grows 

 taller than barley and not so tall as rye. The weight of 

 straw is usually nearly twice the weight of grain, but it may 

 vary widely from this. 



A single wheat grain may give rise directly to a single 

 culm and indirectly to a score or more of stems, as explained 

 below. The buds at the lower nodes (joints) of each culm 

 may themselves develop into additional culms, and from 

 the lower nodes of these still other stems may spring. This 

 formation of culms from lower buds at the underground 

 nodes of each stem explains how and why wheat and other 

 small grains tiller; that is, they produce a number of 

 stems from a single seed. The greater the space between 

 plants and the greater the rainfall and supply of plant- 

 food, the greater is the number of culms from a single 

 crown. 



D 



