336 PRINCIPLES OP NATURAL ARRANGEMENT. 



now regarded as. for the most part, very natural assemblages ; 

 that is, as containing plants really allied to each other in their 

 most important characters, and differing from those of other 

 orders in the same. But of the best mode of arranging these 

 orders he was necessarily ignorant, since the most important 

 characters were not then understood. The great progress which 

 has been made since his time, in the Structural and Physiolo- 

 gical departments of Botanical Science, has done much to place 

 Classification on a more certain basis ; yet there is still much 

 wanting, before Botanists shall be generally agreed on the prin- 

 ciples which shall regulate the division and subdivision of the 

 Vegetable Kingdom. In the following outline, the object is 

 less to give a bare sketch of the entire system, than to offer such 

 a view of it, as may serve to show its nature. It is intended to 

 describe most fully those Orders to which the greatest number of 

 British Plants belong; and to state the relations which the 

 species of most importance to man, whether as furnishing articles 

 of food, valuable medicines, or materials for his various arts, 

 bear to these. In so doing, it has been deemed advisable to 

 adopt the Classification of De Candolie, being the one which is 

 most in use at the present time ; and the principles upon which 

 it is founded will, therefore, now be explained. 



490. It may be remarked, however, in the first place, as a 

 principle common to all Systems of Classification which profess 

 to be Natural, that the different values which are attached to 

 the various characters furnished by the several organs of plants, 

 should be estimated by the degree in which they respectively 

 indicate important similarities or differences si general conforma- 

 tion. It often happens that attention to one or two characters 

 may afford a considerable amount of knowledge of the whole ; 

 because those characters are found to be inseparably connected 

 with others. An instance of this lias been already given, in 

 regard to the primary division between Exogens and Endogens 

 (. 478) ; and it may be useful to illustrate it further by refer- 

 ence to the Animal kingdom. If, for example, we meet witli an 

 Animal covered with feathers, we at once know a great deal of 

 its internal structure and economy. It is a Veriebraled animal, 

 possessing a jointed back-bone and complete internal skeleton ; 



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