24 PHENOMENA OF VEGETATION. 



These observations may give some idea of the quantity of moisture 

 taken up by the rootlets of trees. 



Sueh is a report of facts ascertained in regard to the maple. It 

 does not follow that an equal quantity of moisture is raised by every 

 kind of tree ; but it may be said a corresponding quantity is, by every 

 one, or a quantity which may be spoken of as something like an 

 approximation to this. And though the fact has not, so far as I 

 know, been tested by exact observation, it is probable that the greater 

 portion of the moisture thus raised from the ground by plants, 

 whether arborescent or herbaceous, is by many of them passed into the 

 atirosphere by the stomates of the leaves — succulent plants with few 

 Btomates being the exception — and that a portioU, and it may be a 

 large portion, of the remainder passes into the soil by the process of 

 exosmose by which the circulation of sap in the plant is effected, 

 but returns to the soil only to be again taken up by the rootlets of 

 the same, or of some other plant, when it has been relieved of some 

 of the residuary matter with which it returned charged, and has taken 

 up a return load of nutriment ; but the probability that the quantity 

 thus returned to the soil bears but a small proportion to the quantity 

 passed into the atmosphere may be demonstrated by an observation 

 of the process referred to. 



To some one charged with the watering of flowers, and who finds 

 the charge a burden, it may have occurred that he seemed to have 

 to supply far more water than could be employed in the structure of 

 the plant, that some, such as the balsam, seemed to require a fresh 

 supply morning, noon and night to keep them growing, and that to 

 planted cuttings and transplanted plants he could scarcely give too 

 copious a supply, and unless he had trimmed them by removing some 

 of the leaves scarcely would what he gave have sufficed : now perhaps 

 it may be understood why all this was necessary, and how the diminu- 

 tion of the foliage helped the growth of the plant when the supply 

 of moisture might otherwise have been inadequate to its maintenance 

 in life. 



