Id8 IMPROVEMENTS IN THE CULTURE OF 



able for the escape of superfluous water, and ad- 

 verse to its evaporation, by never becoming so much 

 heated on the surface, or conducting the heat so 

 far downwards as a close compact soil. 



These properties of the soil relatively to plants 

 can never be completely attained by growing 

 plants in pots, and least of all by growing them in 

 pots surrounded by air. In this state, whatever 

 may be the care of the gardener, a continual suc- 

 cession of changes of temperature will take place 

 in the outside of the pot, and the compact material 

 of which it is composed being a much more rapid 

 conductor of heat than porous earth, it will soon 

 be communicated to the web of roots within. 



With respect to water, a plant in a pot surround- 

 ed by air is equally liable to injury. If the soil be 

 properly constituted, and the pot properly drained, 

 the water passes through the mass as soon as poured 

 on it, and the soil at that moment may be said to 

 be left in a state favourable for vegetation. But as 

 the evaporation from the surface and sides of the 

 pot, and the transpiration of the plant goes on, it 

 becomes gradually less and less so, and if not soon 

 re-supplied, would become dry and shrivelled, and 

 either die from that cause, or be materially injured 

 by the sudden and copious application of water. 



Thus, the roots of a plant in a pot surrounded 

 by air, are liable to be alternately chilled and 

 scorched by cold or heat, and deluged or dried up 

 by superabundance or deficiency of water, and no- 



