STRUCTURE OF WHEAT 27 



soil, but is usually about an inch from the surface, irrespective of 

 the depth of the grain or of the temporary roots. There is noth- 

 ing in the nature of a tap root in any of the grasses such as is 

 found in the legumes. Any node under the soil, or even near 

 the soil, may throw out a whorl of roots. When wheat is planted 

 under ordinary field conditions the roots curve slightly outward 

 and then descend almost vertically. The more unoccupied soil 

 about a wheat plant the more the roots curve outward. As soon 

 as the available surface soil is occupied the roots descend. An 

 abundance of roots has been observed at a depth of four feet, 

 and under favorable conditions they doubtless go much deeper. 

 Schubart traced the roots of a winter wheat plant seven feet deep.-^ 

 Webber found that if the roots of one wheat plant were placed 

 end to end they would reach 1,704 feet.^ Near the surface the 

 roots branch and re-branch abundantly, filling the soil with a 

 mass of roots, the ends of which are covered with root hairs. 

 The Minnesota Station found about eight branch roots to the 

 inch on the main roots to a depth of eighteen to twenty inches, 

 varying in length from one-half inch to twenty inches. Below 

 this distance few or no branches were found, suggesting that the 

 purpose of these deep roots was to secure water.^ 



53. Culms. — Like the majority of the plants of the grass 

 family, wheat has usually hollow culms, but in some varieties this 

 space is more or less filled with pith. The greatest variation is 

 found in the upper internode, which should be examined in de- 

 scribing a variety. The walls of the culm also vary in thickness, 

 and the surface varies in color, and may be whitish, yellow, 

 purple cr brownish. Just below the spike the surface of the 

 culm is more or less furrowed. The length varies with type and 

 variety. The same variety is variable on different soils, with 

 different fertilizers, and in different seasons. The variation in 

 length of stem and yield of straw is greater than in size or yield 



1 Agricultural Botany. M. C. Potter, p. 170. 



2 Ibid. 



8 Minn. Bui. 62 (1899), p. 405. 



