a ther, and separates others which are in many respects nearly 
174 SYSTEMATIC BOTANY. = 
627. When we consider the infinite variety of species — 
which compose the vegetable world, (there are about 80,000 
known), it will be obvious that it will be advantageous to 
have some method for arranging them in divisions and sub-— 
divisions, each of which shall possess some well-marked cha- 
racter or characters, common to all the plants that are in- 
cluded under it. Fortunately, though the differences are 
numerous, there are always numerous resemblances between — 
the species, which afford grounds for such arrangements 
By this means we are better enabled to retain the names and _ 
characters of plants in the memory, for it is easier to recollect — 
that a number of plants possess certain characters by seeing 
them classified together under some name implying these cha- : 
racters, than by studying them separately. When we know — 
in what particular class or order a plant is placed, we al- 
ready know so much of its structure, and, what is very im-_ 
portant, by having plants classified, and the classes arranged, 
we learn what plants have resemblances, and what have little 
similarity. ? 
628. Another object of a classification is, that a beginner, 
when he has a plant that is new to him, and no one at hand 
to tell him its name, may be able, by examining afew simple a 
and easily found out characters of the plant, to find out de 
name in a work of reference (or Flora), and thus ascertain — 
its history. This is the main object of what is called an 
Artificial System of Classification ; so called because it does 
_ not necessarily depend on the distinctions marked out, noT — 
correspond with the system followed, by Nature. It gn 
rally depends on only one or two organs, and sometimes 
upon an accidental or comparatively unimportant character — 
of the organ ; and frequently combines under one class or 
order plants dissimilar to-each other in almost every point 
except that single one for which they may be brought toge- 
related. An artificial system, from its simplicity, is extreme- 4 
Ty convenient, and, indeed, necessary, for beginners: but it 
should be regarded only as an introduction, because it doe — 
