32 



THE ROOT 



the rational application of manures to the plant are best under- 

 stood and appreciated after a careful study of these points. Tap- 

 rooted crops, such as sugar-beet, mangold, carrot, and parsnip, 

 require the soil to be well-worked to some considerable depth. 



Surface-rooting plants, such as barley, can be grown upon 

 comparatively thin soils. The same is true of pears grafted on 

 the quince and apples on the Paradise stock, and such plants 

 respond more quickly to, and are more benefited by, top-dressings 

 of soluble manures than plants with a deeply-penetrating root- 

 system. 



Ex. 18. — The student should dig up and examine specimens of the roots 

 of all the chief plants of the farm ; especially is it necessary to investigate 

 the general form and extent of the roots of the common weeds of arable 

 and pasture land. Begin with the examination of young seedlings, which are 

 readily obtained in a complete condition. Note the presence or absence of 

 tap root, extent of branching, the depth to which they descend, and their 

 horizontal extension. 



8. Root-Hairs. — On the root of a seedling bean grown on damp 

 flannel or blotting-paper is seen a fine white silky band of hairs. 

 These are called root-hairs, and they are never present at the 

 extreme tip of the root but arise at some distance behind its 

 growing point. As the root elongates the root-hairs on the 

 older parts die and turn brown, but others are produced on 

 the younger parts, so that no matter what the length or size of 

 the root may be for a short distance behind its tip it is clad 

 with these delicate transparent hairs. When secondary roots make 

 their appearance hairs are produced upon them in the same 

 manner and follow the same order of development as those upon 

 the primary root. 



Their size and abundance are dependent on the species of the 

 plant, and, the amount of moisture surrounding the root. Plants 

 growing in very wet situations or completely in water have 

 few or no root-hairs. In very dry soils their development is 

 checked, the greatest abundance being met with in moderately 

 damp soils. 



