ROOTS THEIR STRUCTURE AND FUNCTION 53 



strength. The most important function, however, is performed 

 by the cambium, which is the region of active growth, and from 

 which both wood and bast are produced. 



Functions of Roots as a Whole. Absorption. The root, as is 

 evident from its structure, is primarily an absorbing organ, and 

 this function will be taken up at length. However, it has many 

 other uses and is adapted to perform very different duties in 

 different plants. 



Fixation. A second use, common to nearly all roots, is that of 

 attaching the plant to the soil, and holding it in an upright position. 



Storage. Frequently the root has sufficient bulk to act as a very 

 efficient storage place for foods. This is particularly important 

 for plants that retain life through long winter months. 



Propagation. It may happen that enough nourishment is stored 

 so that the plant can send up shoots at various places or even 

 be divided, so reproducing the plant. 



Adaptations of Root Form. From the foregoing it is evident 

 that roots must be profoundly varied in structure and form to 

 perform the different functions mentioned. And it must be re- 

 membered that not only function, but other factors such as climate, 

 soil, moisture, and exposure, which together make up the plant's 

 environment, affect growth. We shah 1 learn that only so far as a 

 plant is fitted to its environment will it thrive. 



Kinds of Roots. The usual place from which roots develop is 

 the lower end of the hypocotyl. Such roots are called normal roots. 

 If they grow from other places such as the stem, leaves, or upper 

 part of the hypocotyl, they are called adventitious roots. 



NORMAL ROOTS 



Soil Roots. Of all forms of normal roots, the commonest are 

 the soil roots and these are of many kinds, depending upon what 

 functions they must perform and the character of the soil, moisture, 

 or climate that surrounds them. They in turn may be divided 

 into three general classes. 



Fibrous Roots are made up of many fine slender rootlets, giving 



