OF THE LEAVES, &C. 93 



air, each continuing to grow more in height 

 than the other, until it is beyond obstruction. 

 Hence those plants that are grown in a clump 

 are always the shortest on the outside, for as 

 these are sooner satiated, they stop and allow 

 the others to overtop them. 



Every artificial means resorted to by garden- 

 ers, to force plants to a fructiferous state, is de- 

 termined by this law, and whether by forcing 

 and facilitating an extension of surface by ar- 

 tificial heat, or shelter ; or by lessening the sup- 

 ply of sap, by curtailing its roots, or channels of 

 conveyance, the effect is the same. 



This law, indeed, which determines the 

 growth and produce of a plant, is very similar 

 to that which governs the process of evaporation. 



As the evaporation and inspissation of a fluid, 

 are determined by the extent of surface, ex- 

 posed to the action of heat, the preparation of 

 the fluids in a plant for fructification appear to 

 be governed. Thus if a vessel, presenting a 

 certain surface, be deprived of one- half of its 

 contents, the remaining half will be evaporated, 

 or inspissated, in the same time that the whole 

 would have been, if placed in a vessel exposing 

 double the extent of surface. We may, there- 

 fore conclude, that as it is the law of nature. 



