PRUNING OF PLANTS. 



273 



KIG. 89. — DIAGRAMMATIC CROSS-SECTION OF A 15ASSWOOI) STEM 



TWO YEARS OLD. 

 p — Pith, m — Medullary rays, c — Cambium, vb — Vascular bundle. 



of healing is carried on by the throwing out of 

 new tissue at the cut edge of the cambium, which 

 gradually rolls out from 

 the circumference to- 

 ward the center of the 

 wound (Fig. 90), where 

 in time it unites and 

 forms a continuous layer 

 of cambium, which gives 

 rise to both wood and 

 bark cells, as in any other 

 portion of the stem. 



It is of the utmost iiu- 

 portance that in remov- 

 ing the limb the cut 

 should be made in such 

 a manner as to bring all parts of its circumfer 



FIG. 90. — IMPROl'ER AND PROPER 



PRUNING. 



a — Cannot heal, b — Healing. 



