laws by which they may be judged of beforehand. Horticulture 

 is by these means rendered a complicated subject such as none 

 but practised gardeners can hope to pursue successfully ; and, 

 like all empirical things, it is degraded into a code of 

 peremptory precepts. 



It will nevertheless be found, if the subject is carefully 

 investigated, that in reality the explanations of horticultural 

 operations are simple, and free from obscurity ; provided they 

 are not encumbered with speculations, which, however inter- 

 esting in theory, are only perplexing in practice in the present 

 state of our knowledge. When, for example, refined chemical 

 disquisitions or minute anatomical details, or references to 

 electrical action, are introduced, a plain subject becomes 

 embarrassed with considerations too learned for the majority of 

 readers of gardening works, and having Kttle obvious applica- 

 tion to practical purposes. Instead, therefore, of introducing 

 points of obscure or doubtful application, or such as are merely 

 speculative and which only tend to complicate the theory of 

 horticulture, it seems better strictly to confine attention to the 

 action of the simplest vital forces ; for the general nature of 

 these has been undoubtedly ascertained, and is easily under- 

 stood by every class of readers. It is certain, for instance, 

 that plants breathe, digest, and perspire ; but it may be a 

 question whether the exact nature of their respiration, digestion, 

 and perspiration is beyond all further explanation ; it is there- 

 fore better to limit our consideration to the naked fact, which 

 is all that it imports the gardener to know, without inquiring 

 too curiously into those phenomena. For it must always be 

 remembered that the object of a work like the present is not to 

 elucidate the laws of vegetable life in all their obscure details, 

 but to teach, to those acquainted with the art of gardening, 

 what the great principles are upon wliich their practice is 

 founded. 



