WHEAT 



307 



short distance from the plant and then descend almost 

 vertically, many of them having been known to grow to a 

 depth of four or five feet. 



376. Culms. The culms of wheat vary in height 

 from three to five feet. They are usually hollow with solid 

 joints, but in a few varieties they are partially or entirely 

 filled with pith. During the early growth of 



the culm, the joints are very close together 

 but as it elongates the spaces between the 

 joints increase rapidly until the plant has 

 reached its full height. The length of the 

 culms vary with type, variety, soil, fertility, 

 and seasonal conditions. The tendency to 

 lodge is governed primarily by the length of 

 the stems and secondarily by their stiffness 

 or strength. There is not necessarily any 

 direct relation between the yield of grain 

 and the length of culms. The latter char- 

 acter, however, influences the ease of har- 

 vesting. 



377. Tillering (Fig. 48). Wheat, like 

 other cereals, throws out branches after the 

 plumule has appeared above ground. Within 

 the axil of each leaf on the culm as well as 

 at each underground node a bud is formed. 

 Ordinarily only the buds that are covered with soil develop 

 into branches, the others remaining dormant. As each 

 branch may produce a limited number of branches, and as 

 these branches may in turn, produce still other branches, 

 each grain may under favorable conditions, produce a rela- 

 tively large number of culms. In exceptional cases one 

 grain of wheat has been known to produce as many as fifty 

 spikes. By this characteristic of tillering, wheat and other 



FIG. 48. 

 Diagrammat- 

 ic section 

 through the 

 stem of wheat 

 about 25 days 

 after planting 

 (enlarged). 

 The first bud 

 designed to 

 form a tiller 

 is just start- 

 ing. 



