146 PRINCIPLES OF GARDEXING. [CH. IV. 



may be made to grow in spite of such confinement, 

 but all experience proves that other favourable cir- 

 cumstances, such as heat, light, and moisture, being 

 equal, those plants are most ^-igorous and healthy 

 wliich have the most liberal supply of air. 



Though an excess of carbonic acid eras is detri- 

 mental, yet its partial absence from the atmosphere 

 is equally fatal to a plant's leaves, for without it they 

 witlier and fall. It is not a matter of indifference, 

 therefore, whether a gTeen-house or hot-house be 

 whitened with a solution of lime, which absorbs that 

 gas from the air, a fortnight or only a day or two before 

 plants are introduced or forcing commenced ; for it 

 is the infliction of several tri\dal injuries to a plant that 

 prevents its successful cultivation; no one who is 

 entitled to practise in the higher departments of his 

 art ever makes such great blunders as at once to 

 destroy the plants under liis care. That fresh-limed 

 walls do injui-e plants is beyond dispute, for the 

 plants in a row of small pots next the back wall in a 

 propagating house W'hich had been thus whitened 

 only the day before, have been more than once 

 observed to be the only plants that acquired a sickly 

 hue, and shed nearly all their leaves. Fleshy leaved 

 plants would not be so liable to injury if obliged to 

 be brought into a house fresh limed, for these require 

 much less carbonic acid daily than thin leaved plants. 

 Five plants of Cactus sj^eciosmimus in the injured 



