264 HOW CROPS GROW. 



to make satisfactory observations on the roots of several 

 important crops, growing in the field. He separated 

 them from the soil by the following expedient : An exca- 

 vation was made in the field to the depth of 6 feet, and 

 a stream of water was directed against the vertical wall 

 of soil until it was washed away, so that the roots of the 

 plants growing in it were laid bare. The roots thus ex- 

 posed in a field of rye, in one of beans, and in a bed of 

 garden peas, presented the appearance of a mat or felt of 

 white fibers, to a depth of about 4 feet from the surface 

 of the ground. The roots of winter wheat he observed 

 as deep as 7 feet, in a light subsoil, forty-seven days after 

 sowing. The depth of the roots of winter wheat, winter 

 rye, and winter colza, as well as of clover, was 3 to 4 feet. 

 The roots of clover, one year old, were 3 feet long, those 

 of two-year-old clover but four inches longer. The quan- 

 tity of roots in per cent of the entire plant in the dry 

 state was found to be as follows. (Chem. Ackersmann, 

 I, p. 193.) 



Winter wheat examined last of April 40% 



" " May 22" 



rye " " "April 34" 



Peas examined four weeks after sowing 44 " 



" at the time of blossom 24" 



Hellriegel has likewise studied the radication of barley 

 and oats (Hoff, Jakresbericht, 1864, p. 106.) He raised 

 plants in large glass pots, and separated their roots from 

 the soil by careful washing with water. He observed 

 that directly from the base of the stem 20 to 30 roots 

 branch -off sideways and downward. These roots, at 

 their point of issue, have a diameter of ^ of an inch, 

 but a little lower the diameter diminishes to about T J^ of 

 an inch. Retaining this diameter, they pass downward, 

 dividing and branching to a certain depth. From these 

 main roots branch out innumerable side roots, which 

 branch again, and so on, filling every crevice and pore of 

 the soil. 



