90 ORGANIC STRUCTURE. 



both cases will be prolonged towards the river and 

 the richer soil. If a plant be so placed, that a greater 

 degree of moist heat exist on one side than on the 

 others, the roots will all trend towards the warmth. 

 Again, if a solid body (which is retentive of heat, 

 or, if cold, is attractive of moisture) be within reach 

 of fibrous roots, they will extend towards and spread 

 themselves on its surface, and seem to luxuriate in 

 the cavity formed by the side of the solid and the soil. 



Roots both ascend and descend from their acci- 

 dental stations in the soil to reach more suitable 

 aliment. Those of the ash will cross from one side 

 of a deep ditch to the other ; first descending when 

 they reach the brink, passing under the bottom, and 

 again ascending the opposite side till they arrive at 

 the due point under the surface, whence they resume 

 their horizontal course, keeping a uniform distance 

 (about ten inches) from the air throughout their 

 range. Mulching with rotten manure will bring 

 roots to the surface ; and in dry seasons they will 

 descend even into deleterious subsoils in quest of 

 moisture. This last circumstance should be guarded 

 against by the orchardist if possible ; for though it 

 may be irrational to suppose that roots can be at- 

 tracted by destructive qualities, yet the want of 

 moisture may induce them beyond a proper depth. 



Although all plants are furnished with fibres, which 

 issue from the extremities of the descending caudex, 

 or immediately from the collet, there are, besides, 

 other processes ejected by the latter organ which 

 cannot with propriety be called fibres ; such are the 



