ABSORBENT POWER OF PLANTS. 83 



greater in these places than in the uninjured surface 

 of the plant. 



The evaporation, further argues HALES, is the Evapora- 

 powerful cause which provides food for the plant 

 and its vicinity. Disease and death of the plant 

 follow, when the proportion between evaporation 

 and supply is interrupted or destroyed in any way. 



When, in hot summers, the earth cannot supply, Effect of 



A ' hot wea- 



through the roots, the moisture which during the ther. 

 day has evaporated through the leaves and surface 

 of the tree, when the tree, or a twig of it, dries up, 

 the motion of the sap is arrested at these points. 

 When once dried, capillary action alone cannot 

 restore the original activity ; the evaporation is the 

 chief condition of the life of plants ; by its means a 

 permanent motion, a continually repeated change in 

 the quality of the juice (sap) is effected. 



" By comparing, "says HALES, " the surface of the Necessity 



for cutting 



roots of plants, with the surface of the same plant the roots 

 above ground, we see the necessity of cutting off planted 

 many branches from a transplanted tree : for if 256 

 square inches of root in surface was necessary to 

 maintain this cabbage in a healthy natural state : 

 suppose upon digging it up, in order to transplant, 

 half the roots be cut off (which is the case of most 

 young transplanted trees), then it's plain that but 

 half the usual nourishment can be carried up, 

 through the roots, on that account ; and a very much 

 less proportion, on account of the small hemisphere 

 of earth the new-planted shortened roots occupy ; 



G 2 



