BOOK 4 
SYSTEMATIC BOTANY, OR THE CLASSIFICATION 
OF PLANTS. 
——_# —_ 
CHAPTER 1. 
GENERAL PRINCIPLES OF CLASSIFICATION, 
Section 1.—Spxucres, GENERA, ORDERS, AND CLASSES. 
Ovr attention has been hitherto directed to the examination of 
the structure and forms of the various organs and parts 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 indicated between them. It is the 
object of Systematic Botany to take notice of such relation- 
ships, and thus to bring plants together which are allied in 
their forms and 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 affinities and 
general properties. 
At the present time there are at least 120,000 species of 
plants known to exist on the earth. It is absolutely necessary 
therefore, for the purpose of study, or in order to obtain any 
satisfactory knowledge of such a vast number of plants, 
that we should arrange them according to some definite and 
fixed rules ; but before we proceed to describe the systems that 
have been devised at various times for their arrangement, it 
will be necessary to define the principal terms which are in 
common use in such systems. 
1. Sprcins.—By the term species we understand a collection 
of individuals which resemble each cther more nearly than they 
