PREFACE. VU 



opinions, whether admitted as true or rejected as 

 erroneous, should be given at length. 



In the first edition, this department was not so 

 complete as I could have wished ; in the present, I 

 have been enabled, chiefly by the aid of Professor 

 De CandoUe's Physiologie, to extend, and, as I hope, 

 to improve it very materially. 



Next foUow^ed in the first edition Taxonomy : or 

 some account of the Principles of Classification ; — 

 a very important subject, comprehending not only 

 a view of the various methods of arrangement em- 

 ployed by botanists in their systematic works, but an 

 explanation of the principles by which the limits of 

 genera and species are determined. It also shews 

 the mode of obtaining a correct view of vegetation, 

 of conducting the examination of unknown plants 

 with precision, of avoiding errors in consequence of 

 accidental aberrations from ordinary structure, and 

 of forming a just estimate of the mutual relation 

 that one part of the vegetable kingdom bears to 

 another. 



But in the present edition I have entirely omitted 

 this book : firstly, because of the great additions that 

 have been made to other topics ; and, secondly, be- 

 cause it is extensive enough to form a work by itself 

 The whole of what was contained in this part of the 

 first edition will be found incorporated with the pre- 

 fatory matter of the second edition of the Introduction 

 to the Natural System of Botany, now in preparation. 

 After this, I have taken Glossology (Book III.) ; 

 or, as it was formerly called, Terminology ; restrict- 

 ing it absolutely to the definition of the adjective 

 terms, which are eitlier used exclusively in Botany, 

 or which are employed in that science in some parti- 

 cular and unusual sense. The key to this book, and 



