386 SYSTEMATIC BOTANY. 



BOOK 11. 



SYSTEMATIC BOTANY, OR THE CLASSIFICATION OF 

 PLANTS. 



CHAPTEE 1. 



GENERAL PRINCIPLES OF CLASSIFICATION. 



OiJR 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 almost infinite varieties of 

 forms which have thus been presented to us, 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 close 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 are 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 at least 120,000 species of plants 

 kno^\^l to exisfon the earth. It is absolutely necessary there- 

 fore, for the purpose of study, or in order to obtain any satisfac- 

 tory 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 

 fur us to define certain terms which are in common use in such 

 systems. 



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

 of individuals which resemble each other more nearly than they 

 resemble any other plants, and which can be reproduced by 



