6 BULLETIN 1087, U. S. DEPARTMENT OF AGRICULTURE. 
ABNORMALITIES DUE TO INJURIES. 
Abnormalities may be the result of injuries due to alternate freez- 
ing and thawing, 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. 
Eoot 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. 3. — Alfalfa root? from a plat clipped 18 timos during the second season. 
Transplanted plants develop many more branches than where the}' 
continue growing under normal conditions. This is because the tap- 
root is generally severed a few inches below the crown, which re- 
sults in the development of an abnormal number of branch roots. 
Plants vary in their ability to produce these lateral roots. A very 
good example of a plant possessing this characteristic to a consider- 
able degree is shown in Figure 4. Six consecutive plants of this 
same variety of alfalfa grown from seed were removed from the 
field and the root systems photographed. (Cf. Fig. 15.) Only one 
of the plants from seed approached in any way, or would in time 
approach, the type of a reset plant. 
Where plants are grown in pots the roots are so closely confined 
that they assume a spiral form and when transplanted to the field 
continue to develop abnormally. The root system instead of spread- 
