ON THE WORLD'S "LICHENES EXSICCATl". 97 



of earlier collections — with labels ol' such a character that no 

 doubt can arise as to the identity of the specimens. 



Many eminent men have favoured me with advice as to the 

 best manner of publication, but I have never met two whose 

 advice agreed. Some told me to examine every specimen myself, 

 and make corrections accordingly, although it is obvious that no 

 mortal being could personally examine 30,000 specimens, — many 

 of them very difficult ones, — and give an authoritative judgment, 

 even supposing anyone could be found who could afford to do so. 

 I do not consider it of very great value to excerpt the various 

 floras and state their "corrections''. The latter are not unvariably 

 improvements, and the weighing of authorities against each other 

 is an unscientific proceeding. I will endeavour, however, to provide 

 bibliographical notes from leading journals of cryptogamy 

 (reviews of exsiccati etc), and I shall mention papers (indexes, 

 criticisms etc) published on any special collection that have been 

 brought to my notice. 



The synonymy of the Lichens is extremely intricate, and as 

 every collection has a synonymy of its own, one species will be 

 found under many different names. It would be very useful, if 

 the names could be reduced to one system, e. g. that of 

 Zahlbruckner in the Natürliche Pflanzenfamilien, but I have 

 doubts of the possibility of so doing. I could easily mention 

 all the Lecidella, Psora, Biatora etc. species under Lecidea, 

 and Cenomyce under Gladonia, but it is not always possible 

 to know, what a Parmelia olivacea or a Lecidea parasema is 

 without an examination of the specimens. I might also make 

 serious blunders with the Pyrenocarpous Lichens for lack of 

 knowledge. — I have thought of arranging the index alphabetically 

 according to the species, not according to the genera. This would 

 bring together names like Lecidea vernalis and Biatora vernalis, 

 G y rophora hyperborea and Umbilicaria hyperborea. I have some 

 liking for this plan, but I cannot say whether it is practical. 

 It is of no small importance to keep the genera together. The 



Nyt. Mag. f. Naturv. LI. II. 1913. 7 



