IV 
PREFACE. 
ence that climate exercises upon their developement ; 
and, lastly, from botany as now understood, in its 
most extensive signification, is inseparable the know- 
ledge of the various ways in which the laws of vege- 
table life are applicable to the augmentation of the 
luxuries and comforts, or to the diminution of the 
wants and miseries, of mankind. It is by no means, 
as some suppose, a science for the idle philosopher in 
his closet ; neither is it merely an amusing accom- 
plishment, as others appear to think ; on the con- 
trary, its field is in the midst of meadows, and 
gardens, and forests, on the sides of mountains, and 
in the depths of mines, — wherever vegetation still 
flourishes, or wherever it attests by its remains the 
existence of a former w^orld. It is the science that 
converts the useless or noxious weed into the nutri- 
tious vegetable ; which changes a bare volcanic rock, 
like Ascension, into a green and fertile island ; and 
which enables the man of science, by the power it 
gives him of judging how far the productions of one 
climate are susceptible of cultivation in another, to 
guide the colonist in his enterprises, and to save him 
from those errors and losses into which all such per- 
sons unacquainted with Botany are liable to fall. This 
science, finally, it is which teaches the physician how 
to discover in every region the medicines that are 
best adapted for the maladies that prevail in it ; and 
which, by furnishing him with a certain clue to the 
knowledge of the tribes in which particular proper- 
ties are, or are not, to be found, renders him as much 
at ease, alone and seemingly without resources, in a 
land of unknown herbs, as if he were in the midst of 
a magazine of drugs in some civilised country. 
The principles of such a science must necessa- 
rily be complicated, and in certain branches, which 
