BOOK II. 



OP THE PHTSIOIiOGHOAL PRINCIPLES UPON WHICH THE OPEEATIONS 

 OP HORTICULTURE ESSENTIALLY DEPEND. 



All operations in horticulture depend for success upon a 

 correct appreciation of the nature of the vital actions described 

 in the last Book; for although there have been many good 

 gardeners entirely unacquainted with, the science of vegetable 

 physiology, and although many points of practice have been 

 arrived at altogether accidentally, yet it must be obvious that 

 the power of regulating and modifying knowledge so obtained 

 cannot possibly be possessed, unless the external influences by 

 which plants are affected are clearly understood. Indeed, the 

 enormous difference that exists between the skiU of the present 

 race of gardeners and their predecessors can only be ascribed 

 to the general diffusion, that has taken place, of an acquain- 

 tance with some of the simpler facts in vegetable physiology. 



In attempting to apply the explanations of science to the 

 routine of horticultural practice, it appears desirable, in order 

 to avoid frequent repetition, that mere details should be 

 omitted, and that those general operations should alone be 

 adverted to which, under many different modifications, and in 

 various forms, constitute the foimdation of every gardener's 

 education. 



