8 BULLETIX 1087, U. S. DEPAET:MEXT OF AGEICULTURE. 



branching and distortion. It is, therefore, quite evident in studying 

 transplanted plants — whether from pots to field or from field to 

 field — that due consideration must be given to the effect of such 

 treatment upon root development. 



Cultivation modifies the normal root system by injuring or de- 

 stroying a large number of the surface roots. The use of the disk 

 harrow on alfalfa fields has been recommended frequently on the 

 theory that by means of it soil moisture is conserved, weeds elimi- 

 nated, and the stand thickened by splitting the crowns. Experiments 

 generally have shown that such treatment is injurious in that it 

 weakens or kills many of the plants. 



Fig. 5. — Production of branch roots and distortions in Grimm alfalfa plants 166 days 

 old. From the 49tli to the 87th day the root systems were confined in small flower- 

 pots. 



In many localities alfalfa roots are subject to considerable injury 

 by rodents, such as gophers and mice. ^Vhen they sever the taproot 

 very close to the crown, as frequently happens, there is no opportunity 

 for the plant to develop side roots, and it soon dies. If the taproot 

 is severed several inches below the crown, the plant often survives 

 and throws out branch roots, behaving much as a transplanted plant 

 does. At Highmore, S. Dak., in 1912 and 1913, several Medicago 

 falcata plants had their main roots severed by gophers, yet these 

 plants have continued to live, although much reduced in vitality. 

 Medicago sativa plants failed to survive when the taproot was 

 severed so near the crown. Malformations in roots may sometimes 

 be caused by disease, the presence of which can only be determined 

 bv close examination. 



