[325] SCIENTIFIC MANUAL. 39 



roots crown roots at the base of the stem. (Fig. 2.) 

 The grasses, including small grain and corn, are examples 

 of this class. 



Notwithstanding the plants have no tap-root, under fa- 

 vorable circumstances, their roots descend to great depths. 

 The roots of wheat have been found at the depth of from 

 three to four feet in light sub-soil. Those plants whcih 

 have more than two cotyledons are called poly cotyledons. 

 Fig. 3 represents the magnified seed of the pine, and the 

 young plant. 



Roots, as well as plants, are further di- 

 vided into annual, bi-ennial and perennial. 



Aquatic and aerial roots, being of no 

 special interest to the farmer, are omitted. 



When we consider the fact that plants 

 are entirely dependent upon their roots for 

 their supply of all of the mineral elements 

 of their food, except carbon, and for their 

 entire supply of water, their importance to 

 the agriculturist demands careful study of 

 their nature, needs and methods of develop- 

 ment. Fig. 3. 



The absorptive power of the root seems to reside in the 

 newt} formed parts, near the extremities of the principal 

 roots, but more particularly in the " root hairs, " which 

 thickly cover the new portions as they advance, and dis- 

 appear as the surface grows hard and becomes covered 

 with thick bark. (See Fig. 4.) 



The tender, newly formed extremities of the roots are 

 also destitute of these ' root hairs, "as may be observed by 

 a close inspection of the roots of a plant soon after germi- 

 nation. The parts covered with " root hairs" will be found 

 closely enveloped in fine earth, while the rest will be bare. 



The force with which active roots absorb the water of 

 the soil, with the plant-food in solution, is very great, ex- 



