THE WHEAT GRAIN AND PLANT 13 



grows about an inch beneath the soil, irrespective of the depth 

 to which the grain was planted. From the crown are thrown 

 out whorls of coronal or permanent roots. Any node of the 

 wheat stalk under or near the soil may also throw out a 

 whorl of permanent roots, somewhat similar to those of corn. 

 There are four or five whorls with three to five roots each. 

 The roots from the base of the crown strike directly down- 

 ward, while those from the later whorls run at an angle for a 

 few inches before taking a vertical direction. Most of the 

 main roots penetrate to a depth of over 4 feet, perhaps 5 or 6 

 feet, provided the water-line is not closer to the surface than 

 that distance, for below this the roots will not enter to any ap- 

 preciable extent. The roots of wheat have been traced to a 

 depth of 7 feet, and it has been found that if those of one 

 plant were placed end to end they would reach 1,704 feet. 

 The deep roots are all fine threads of practically uniform diam- 

 eter throughout their entire length. They branch and re- 

 branch freely to a depth of 18 or 20 inches, about eight branch 

 roots occurring to an inch length of a main root. At a greater 

 depth, branches are few or absent, and it is supposed that the 

 deep roots are for securing moisture. The roots do not branch 

 or feed much in the region just below that stirred by the 

 plow, if that region is hard and gummy, as is often the case. 

 The upper whorls give forth roots that are larger and coarser, 

 and which resemble the brace roots in corn. It is said that 

 the roots extend chiefly at their extremities, while the stem 

 elongates equally, or nearly so, in all of its contiguous parts. 

 The root development seems to be greatest in durum wheats. 

 Early spring and summer rains cause shallow rooting. In the 

 absence of these rains in the far west, a deeper root system, 

 capable of resisting superficial droughts, is developed. Poor 

 soil causes the roots to age rapidly. 



Culms. The culms of wheat are usually hollow, but in some 

 varieties they are quite filled with pith. The length varies 

 greatly in different varieties, soils and seasons, a fact which 

 results in greater variation in size and yield of straw than of 

 grain. Common wheat averages from three to five feet in 

 height. The liability of lodging depends greatly on the culm, 

 the length of which is also important in harvesting. 

 1 Hunt. Cereals in Amer. (1904), p. 27. 



