AGRICULTURAL BOTANY 



121 



Our most important food supply comes from the 

 flower, or rather the seed which the flower produces. 

 Grains, fruits, nuts, and melons are well-known ex- 

 amples. 



The Root. The root of the plant in most instances 

 extends below the surface of the ground, fixing the 

 position of the plant and taking from the 

 soil water containing the dissolved mineral 

 food that the plant needs. As a rule, the 

 root springs from the stem, and not the 

 stem from the root. 



Primary Roots. The seed, when put 

 under the right conditions of moisture, air, 

 and temperature, begins to sprout, or ger- 

 minate. It sends downward a primary root. 

 This may later branch and subdivide until 

 it is entirely lost in its divisions, or it may 

 continue in one main root, having small 

 side branches only, as in the carrot and 

 radish. The branches from the primary 

 roots are called secondary roots. 



Adventitious Roots. Under favorable 

 conditions any part of the stem may produce roots. 

 These usually come from parts where leaves or branches 

 would naturally spring, but sometimes they grow from 

 other parts of the stem. In either case they are called 

 adventitious roots. Because of this tendency in stems 

 to send off roots from different parts, some plants may 

 be multiplied by cuttings ; that is, by cutting a slip 

 of the stem and planting it in moist soil, in sand, or in 

 water. 



Classes of Roots. When a root of a plant divides 

 and subdivides into numerous small, threadlike forms, 



FIG. 48. 

 Plantlet of 

 Indian Corn, 

 showing Pri- 

 mary Root. 



