PREFACE. 
be hoped that these beautiful but neglected tribes will become as 
familiar to botanists as our more conspicuous flowering plants 
now are. I have already mentioned my indebtedness to my 
friend, Mr. Tuckerman, for his contribution of the still more 
obscure Lichenes , and my regret at being compelled to omit this 
order. 
I have to thank a large number of correspondents for specimens 
and information kindly rendered in various ways, and especially 
my esteemed friends, Mr. Oakes, of Ipswich (who is far more 
intimately acquainted with New England plants than any other 
botanist), and Mr. Olney, of Providence, who have most cor¬ 
dially rendered me essential aid. 
I have only to ask, that those who use this book will favor 
the author with information of the corrections, alterations, and 
additions that may appear to be necessary, in order that a fu¬ 
ture edition may be made more accurate and complete than the 
present. 
Harvard University, Cambridge, 
December 24£4, 1847. 
