PREFACE. 
This work is designed as a compendious Flora of the Northern 
portion of the United States, arranged according to the Natural 
System, for the use of students and of practical botanists. It was 
intended to be comprised within the compass of a pocket volume, 
which might serve as a vade-mecum in herborizations, as well as a 
convenient manual of reference at home. But the volume has 
attained a somewhat unwieldy bulk, notwithstanding every effort 
at condensation, and the rigorous exclusion of all irrelevant mat¬ 
ter, however interesting in itself, and of all synonymy not really 
essential. Perhaps I have been too scrupulous in the latter re¬ 
spect ; but it should be considered that all synonymes are useless 
to the beginner, — whose interests I have particularly kept in 
view, —while the greater part are needless to the instructed bota¬ 
nist, who has access to more elaborate works in which they are 
plentifully given. By discarding them, except in case of original 
or very recent changes in nomenclature, I have been able to avoid 
troublesome abbreviations and crabbed signs, to give greater ful¬ 
ness to the characters of the species, and especially of the genera 
(a point in which I conceive most works of this class are deficient), 
and also to add the derivation of the generic names. 
It will be observed, that I have been compelled to be extremely 
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