6 BTJT.T.F.Tiy 1087, TJ. S. DEPAETMEXT OF AGEICULTURE. 



ABNORMALITIES DUE TO INJURIES. 



Abnormalities may be the result of injuries due to alternate freez- 

 ing and tha-wing. to cultural treatment, rodents, insects, or disease. 

 Only the more evident of these will be considered in this connection. 



The breaking of roots due to soil heaving is a common occurrence 

 in regions of considerable precipitation and subject to rather 

 suddenly alternating temperatures above and below freezing. The 

 breaking of taproots near the surface in plants with few branch 

 roots may prove fatal, but where there is considerable branching of 

 the taproot near the crown the plant will ordinarily survive, being 

 supported by some of the branch roots that have not been broken. 

 Root injury caused by the heaving of the soil has proved to be a 

 serious factor in the humid sections of the northern United States, 

 but does not commonly occur in the Great Plains. 



Fig. .". — Alfalfa roots from a plat clipped 18 timrs during the second season. 



Transplanted plants develop many more branches than where the] 

 nontinue growing under normal conditions. This is because the tap 

 root is generally severed a few inches below the crown, which re 

 suits in the development of an abnormal number of branch roots 

 Plants vary in their ability to produce these lateral roots. A ver 

 good example of a plant possessing this characteristic to a consider 

 able degree is shown in Figure 4. Six consecutive plants of thi 

 same variety of alfalfa grown from seed were removed from th 

 field and the root systems photographed. (Cf. Fig. 15.) Only on 

 of the plants from seed approached in any way, or would in tim 

 approach, the type of a reset plant. 



Where plants are grown in pots the roots are so closely confine 

 tliat they assume a spiral form and when transplanted to the fiel 

 continue to develop abnormally. The root system instead of spreaf 



