Lichenes of New England. 449 
in these papers.* But the path is by no means a 
smooth one, and the errors that may be found to 
occur, will, I hope, meet with due consideration. To 
William Oakes, and B. D. Greene, Esquires, I owe 
the unrestricted use of the collections of Lichens in 
their extensive herbaria ; that of the latter gentle- 
man containing many species from Hooker. To 
Dr. Porter, of Plainfield, who has pursued, for many 
years, the study of the Cryptogamous Orders, I have 
been long indebted, not only for several very rare 
lichens, but for numerous authentic specimens of the 
‘More’common forms. From. other of our Cryptoga- 
mists the writer has received interesting species, and 
particularly from Mr. Russell, of Chelmsford, the 
author of several excellent papers on these and other 
allied plants, an and our President, George B. Emerson, 
Esq. 'To Dr. Harris, in common with every student 
of Natural History at Cambridge, my obligations 
have been constant. And I have received from Pro- 
fessor Torrey; Mr. Greene, and Mr. A. White of the 
British Museum, numerous lichens of New Holland 
and Yan Diemen's Land, some of which are interest- 
ing for comparison with our — with which the 
former generally seem to 
_ In accordance with the intimation at the beginniay 
of the paper, a few brief remarks on The- Syste- 
aaner t varieties, have been enumerated 
; e and is exclusive of the common 
species, Lecidea parasema, Lecanora subfusca, Parmelia masa, &c., 
which have not been mentioned in his list. 
