30 THE ROOT 



stout roots similar to the thicker branches of the crown, and from 

 these are given off a larger number of a finer texture. By far 

 the greater bulk, however, which the tree possessed remain in the 

 ground in the form of extremely fine rootlets or fibrils extending 

 outwards generally as far, or a little farther, than the branches 

 and leaves of the tree, but in some instances to much greater 

 distances. Not only do the roots grow out horizontally and near 

 the surface of the soil, but they extend downwards as well. In 

 isolated instances, where an adequate supply of air has been 

 maintained along open cracks and fissures, roots have been 

 found to descend many yards into the ground, but in general 

 the roots of the tallest trees rarely go down more than seven 

 or eight feet. The want of air and presence of noxious sub- 

 stances in the lower regions of the soil checks further growth in 

 this direction. 



With many plants almost every cubic inch of soil immedi- 

 ately beneath their shade contains fine delicate rootlets, and tha 

 extent of their root-branching is very rarely realised on account 

 of the ease with which these hair-like fibrils are broken off when 

 the plant is pulled up or disturbed. 



Many forest trees have a natural habit of sending their roots 

 several feet into the soil. Examples of fruit-trees belonging to 

 this class, and requiring a deep soil for proper growth, are the 

 cherry and wild pear. 



Some trees, such as larch, keep their root-system nearer 

 the surface, spreading out more horizontally in the ground. 

 The quince, used as a stock on which to graft pears, has roots 

 which remain in the upper regions of the soil. Similar surface- 

 rooting habit is very marked in the ' Paradise ' apple on which 

 apples are grafted, and in Prunus Mahaleb upon which cherries 

 are often grafted. 



The root-system of wheat penetrates more deeply than that 

 of barley ; the mangold sends its fine rootlets more extensively 

 into the deeper layers of the soil than cabbage or turnip; 



