82 THE ROOT, 



Growing as they do in a medium of such unequal resistance as the 

 soil, if roots increased like growing stems, by the elongation of 

 their whole body, they would be thrown, whenever the elongating 

 force was insufficient to overcome the resistance, into knotted or con- 

 torted shapes, ill adapted for the free transmission of fluid. But, 

 lengthening only at their farthest extremity, they insinuate them- 

 selves with great facility into the crevices or yielding parts of the 

 soil, and afterwards by their expansion in diameter enlarge the 

 cavity ; or, wlien arrested by insuperable obstacles, their advancing 

 points follow the surface of the opposing body until they reach a 

 softer medium. In this manner, too, they readily extend from place 

 to place, as the nourishment in their immediate vicinity is consumed. 

 Hence, also, may be derived a simple explanation of the fact, that 

 roots extend most rapidly and widely in the direction of the most 

 favorable soil, without supposing any self-determining power beyond 

 what belongs to all growing parts. (Chap. XIII.) 



138. Wc have taken the root of the seedling as an example and 

 epitome of that of the whole herb or tree; as we rightly may, for 

 in its whole development the root produces no other parts ; it bears 

 nothing but naked branches, which spring from different portions of 

 the surface of the main root, nearly as this sprung from the radicle, 

 and exactly imitate its growth. They and their ramifications are 

 mere repetitions of the original descending axis, serving to multiply 

 the amount of absorbing surface. The brandies of the root, more- 

 over, slioot forth irregularly, or at least in no order like that of the 

 branches of the stem, which have a symmetrical arrangement, de- 

 pendent upon the arrangement of the leaves (166). 



139. To the general statement that roots give birth to no other 

 organs, there is this abnormal, but by no means unusual exception, 

 that of producing buds, and therefore of sending up leafy branches. 

 Although not naturally furnished witli buds, like the stem, yet, 

 under cerlfiin circumstances, the roots of many trees and shrubs, 

 and of some herbs, have the power of producing them abundantly. 

 Thus, when the trunk of a young Apple-tree or Poplar is cut off 

 near the ground, while the roots are vigorous and full of elaborated 

 sap, those which spread just beneatli tlie surface produce buds, and 

 give rise to young shoots. The roots of the Maclura, or Osage 

 Orange, habituallj' give rise to such irregular or adventitious (168) 

 buds and branches. 



140. Although the root does not produce ascending axes, or stems, 



