PRINCIPLES OF THE GROWTH OF TREES. 



divided as growth advances, until lost in laterals or side 

 branches. The fibres or rootlets are the small thread-like 

 roots proceeding from the laterals; and lastly, the smallest of 

 all, the new fibres are furnished with root-hairs, scarcely visi- 

 ble without a 

 ^ H ii microscope. 



The whole 

 surface of 

 roots continue 

 to absorb 

 moisture from 

 the soil so 

 long as they 

 are fresh and 

 new; and the 

 newer p o r- 

 tions, near the 

 tips, absorb 

 m o St freely. 

 Old roots, 

 covered with 

 a hard or hor- 

 ny bark, imbibe almost none. The root-hairs convey mois- 

 ture into the fibres with rapidity. Young trees, when dug 

 up for transplanting, have most of the fibres and root-hairs 

 torn from them, and they would suffer serious injury or die, 

 but for the powv^r which they possess of rapidly reproducing 

 them under favorable influences. 



The collar is the point of union between the root and the 

 stem, but its place may be easily changed in many young 

 plants by banking up the stem, which will emit new roots 

 above. Or, a branch may be buried, as in layering grape- 

 vines, honeysuckles, gooseberries, and many other woody 

 plants. Small portions of roots attached to a graft will often 

 produce a new plant; this is especially the case with the 

 grape and rose, which are extensively propagated in this way ; 

 and also in some degree with the apple, of which, however, 

 when thus root-grafted, larger portions should be employed of 

 the roots of one-year, or at most two-year, seedlings. 



Fig. 2.— Root System of Two-year-old Apple. 



