This is a final report to the friendly correspondents of the author on 
the specimens which, for many years, they have sent to him for determi- 
nation. And such determination implying a certain arrangement, the 
book is further a report upon what, after much labour, has commended 
itself to him as the best-ascertained, systematic disposition of the Lichens. 
It was intended, in an introductory chapter, to attempt some reckoning 
of the more weighty, published opinions as to the position, and rank of 
these plants in nature; to review cursorily the development of the sys- 
tem, and several of the varying interpretations of it; and to consider 
finally, more at large, the systematic value of the anatomical characters, 
as especially of the spore characters ; but prolonged indisposition, result- 
ing from overwork, and rendering it necessary to depend upon a friend 
for the correction of the press, and to shorten as much as possible these 
prefatory observations, leaves it open only to say that the author’s point 
of view here, remains in general the same with that indicated by him 
already in print, on another occasion ;' and that the further exemplifica- 
tion of what is there advanced must now speak for itself. 
It yet appears proper to add that the result of a long study of inter- 
tropical and related lichens, pursued by the writer, at first under the 
friendly direction of Fries, and Montagne, as afterwards in the light of 
the more recent lichenology, and, especially, of the very instructive writ- 
ings of Nylander, — was a persuasion that, so far as system was concerned, 
the later lichenographers had scarcely the advantage which it was 
assumed that they had over the earlier; that not a few of the changes of 
form proposed by the former were either insufficiently grounded, or com- 
paratively unimportant, if not now erroneous; and that there was, in a 
word, nothing as yet to compare, in solidity and thoroughness of con- 
struction, with the system (as understood in its principal outlines, and as 
embracing, it afterwards proved, the Collemaceous lichens) of Fries. 
And thus the question opened which is pursued in these pages — how far 
does the increase of knowledge, whether of external form or anatomical 
! Lichens of California, Oregon, and the Rocky Mountains, 1866, pp. 5—11. 
