394 



BOOK II. 



SYSTEMATIC BOTANY, OR THE CLASSIFICATION OF PLANTS. 



CHAPTER 1. 



GENERAL PRINCIPLES OF CLASSIFICATION 



Our attention has been hitherto directed to the examination of 

 the structure of the various parts and organs of plants. In doing 

 so, we cannot but have noticed the ahnost infinite varieties of 

 forms which have thus been-, presented to ns, and also at the 

 same time observed that, notwithstanding such variations, there 

 are some striking resemblances in the structure of the organs of 

 certain plants, by which a cloge relationship is thus clearly indi- 

 cated between them. It is the object of Systematic Botany to 

 take notice of such relationships, and thus to bring plants 

 together which are allied in their structure, and to separate those 

 that arc unlike; and in this way to take a comprehensive view 

 of the whole Vegetable Kingdom. In its extended sense. 

 Systematic Botany has for its object, the naming, describing, 

 and arranging of plants in such a manner, that we may readily 

 ascertain their names, and at the same time get an insight into 

 their relations and general properties. 



At the present time there are probably about 125,000 species 

 of plants known to exist on the earth. It is absolutely neces- 

 sary therefore, for the purpose of study, or in order to obtain 

 any satisfactory knowledge of such a vast number of individuals, 

 that we should arrange them according to some definite and 

 fixed rules. Before we proceed to describe the systems that 

 have been devised at various times for their arrangement, it will 

 be necessary for us to define certain terms which are in common 

 use in sucli systems. 



1. SricciEs. — By the term species we understand a collection 

 of individuals whicli resemble each other more nearly than they 

 resemble any other plants, and which can be rejjroduccd by 

 seed ; so that we may from analogy infer that they have all 



