INTRODUCTION. 
XI 
sub-genera, are connected with the habit of the plant, and 
cannot be neglected. Indeed the time may ere long 
arrive, when what are now called genera or sub-genera 
will alone be considered species, and another Linnaeus be 
requisite to reduce the chaos into order. Mr. Bentham, 
in his “ Handbook,” has advanced boldly in this direc- 
tion ; but it does not seem expedient either to reduce what 
have been for long deemed distinct, or to subdivide 
them in the Flora of a single country, until the same 
principles have been successfully applied to all genera, 
Tropical as well as European. Those who study only 
specimens preserved in herbaria may occasionally com- 
bine too much ; while others, who trust to living plants 
without testing the characters by dried specimens, are 
much too apt to raise forms, particularly if permanent 
in cultivation, to the rank of species. We have, there- 
fore, endeavoured to follow a middle path : the species 
admitted in former editions are seldom reduced, unless 
where it was found that the characters were insufficient 
or variable ; and as rarely has sanction been given to 
those which have been split off from others, by the 
ingenuity of a Fries, a Koch, or a Jordan. If in 
some cases, particularly in the genus Hieracium, this 
neomania has been yielded to, it has been partly on ac- 
count of the remonstrances of our friends, and partly 
from the difficulty in ascertaining to which original 
species these aberrant forms ought to be referred ; of 
several of them, indeed, we have not seen authentic 
specimens. 
As to varieties, of late years a practice has prevailed 
of considering them to be departures from or abnormal 
states of some single form, which is assumed to be the 
type of that species : and thus the species is frequently 
characterized so as to exclude all but one variety, the 
others being appended like so many useless disjecta 
