THE GREEN-HOUSE. 



141 



Though an imitation of nature may not be always 

 the best mode of culture, yet no culture can be suc- 

 cessful that is not conducted on natural principles. 

 No culture can be successful which does not proceed 

 on the value of roots and leaves, as the foundation of 

 all the other productions of the plant, and recipro- 

 cally of each other's growth — on the value of light 

 to the maturation of leaves — and of heat and mois- 

 ture to the promotion of growth, &c. 



The living principle in most plants ceases to exist 

 when they are detached from the soil, and surrounded 

 by air. The same may be said of the parts of plants 

 artificially detached, as branches, shoots, leaves, &c. ; 

 but not of bulbs and tubers, which are entire plants 

 in embryo, and, like seeds (which are the same 

 thing), may be kept out of the soil for some time. 

 The living principle in plants detached from the soil, 

 and in shoots or detached leaves or flowers, may be 

 preserved for a considerable period by lessening 

 evaporation from their surfaces ; as by inclosing in a 

 box or case, packing in loose straw, &c. ; and hence 

 the value of a botanic box. Life may be maintained 

 a still longer time, by inserting the roots or root ends 

 of shoots or leaves in soil, or moistened moss, straw, 

 or other matter that will supply a moderate degree of 

 moisture. Thus it appears that plants when in a 

 dormant state are not entirely so ; but that there is 

 going on a certain degree of circulation of sap, or 

 waste of life, and which of course requires a supply. 



All extraordinary stimuli applied to plants, as 



