138 PRINCIPLES OF GARDENING. [CH. IV. 



they are more capable of Imng in dry situations, 

 wliich, in general, is really the case. The matter 

 transpired by a healthy plant is nearly pure water, 

 5,000 grains of it never containing more than one 

 grain of solid matter, and this is constituted of resin- 

 ous and gummy matter, with carbonate and sulphate 

 of lime. It appears to be nearly the same in all 

 plants. The quantity, however, we have seen, varies 

 in every species, probably in eveiy indi^ddual — and 

 is greatly influenced by the quantity of water applied 

 to the roots. Under precisely similar circumstances, 

 Sennebier obtained the following results : 



Grs. Grs. 



A peach branch, imbibing 100 exhaled 35 



210 . . 90 



220 . . 120 



710 . . 295 



I have found the branch of a pelargonium, that, 

 whilst growing on the parent stem, exhaled only 

 twenty grains in twenty-four hours, more than trebled 

 that quantity, in the same time, when cut from the 

 stem, and placed \^ith the di^dded end in water. 

 This increased transpiration is attended by a propor- 

 tionate reduction of temperature ; for a collection of 

 pelargoniums, in the midst of which Fahrenheit's 

 thermometer stood at 55*^, fell to 48° ^rithin two 

 hours after a plentiful watering to their roots only, 



