Vlll 
PREFACE. 
to species. A genus, order, or class, is therefore called natural, not be- 
cause it exists in Nature, but because it comprehends species naturally 
resembling each other more than they resemble any thing else. 
The advantages of such a system, in applying Botany to useful pur- 
poses, are immense, especially to medical men, with whose profession 
the science has always been identified. A knowledge of the properties 
of one plant is a guide to the practitioner, which enables him to substitute 
with confidence some other that is naturally allied to it ; and physicians, 
on foreign stations, may direct their inquiries, not empirically, but upon 
fixed principles, into the qualities of themedicinal plants which nature has 
provided in every region for the alleviation of the maladies peculiar to 
it. To horticulturists it is not less important : the propagation or cultiva- 
tion of one plant is frequently applicable to all its kindred ; the habits of 
one species in an order will often be those of the rest ; many a gardener 
might have escaped the pain of a poisoned limb, had he been acquainted 
with Natural affinity; and, finally, the phenomena of grafting, that 
curious operation, which is one of the grand features of distinction be- 
tween the animal and vegetable kingdoms, and the success of which is 
wholly controlled by ties of blood, can only be understood by the student 
of the Natural System. 
As to any difficulties that the student may encounter in the study of 
Botany upon the principles of the Natural System, it is to be observed 
ill the first place that they are only such as it is always necessary to re- 
move in all branches of human knowledge ; and secondly, that they 
have been very much exaggerated by persons who have written upon 
the subject without understanding it. 
It is said that the primary characters of the classes are not to be as- 
certained without much laborious research ; and that not a step can’ 
be taken until this preliminary difficulty is overcome. But it is 
hardly necessary to say, that in natural history many facts which have 
been originally discovered by minute and laborious research, are subse- 
quently ascertained to be connected with other facts of a more obvious 
nature, and of this Botany is perhaps the most striking proof that can 
be adduced. One of the first questions to be determined by a student 
of Botany, who wishes to inform himself of the name, affinities, and 
uses of a plant, appears to be, whether his subject contains spiral vessels 
or not, because some of the great divisions of the vegetable kingdom 
are characterised by the presence or absence of these minute organs. 
It is true, Ave have learned by careful observation, and multiplied mi- 
