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benefit of correspondence with the foremost American and European 
students, and during the latter part of which he has been called upon as a 
specialist to study collections from many parts of the country, The second 
factor is the long continued and thorough special work in Minnesota, upon 
which the book is based, extending as it does over fifteen years of field and 
herbarium study. The book is especially noteworthy in being the first 
American publication, including a large proportion of our species, to contain 
complete keys to the genera and species. The lack of such keys has been 
a serious handicap to all students of lichens, and especially to beginners in 
the study. Another feature of the work which is deserving of special 
mention is the large number of excellent photographs of typical specimens, 
with which the descriptive catalogue is illustrated. As an aid to the 
recognition of the plants and as an indication of their natural habits these 
photographs leave nothing to be desired. 
Professor Fink’s experience and the conservatism of his previous publi- 
cations lead us to examine with special interest the views on classification 
expressed in this work. The general outlines of the classification and the 
arrangement and limitation of the families is in general similar to that 
proposed by Doctor Zahlbruckner in Engler and Prantl’s Die Natiirlichen 
Pflanzenfamilien, which undoubtedly represents better than any other 
system yet offered our present ideas as to the natural classification of lichens. 
Professor Fink’s most marked departures from this are in retaining 
Biiellia among the Lecideaceae, a safe and conservative procedure, and in 
placing the Pyrenocarpineae at the end of the system. This position seems 
to be open to question. While it is clearly recognized that no linear arrange* 
ment can truly represent a natural system of classification it is generally 
assumed that the groups placed at the end of the system are the highest in 
evolution. The placing of the Pyrenocarpineae in such a position can only 
be justified as following the custom of the m^mologists in placing the 
Pyrenomycetes above the Discomycetes among the fungi. For those who 
hold the view that the lichens represents lines of evolution in a different direc- 
tion from the other fungi, a position for the lowly organized Pyrenolichenes 
at the beginning of the system seems much more natural. 
In the matter of generic limitations Professor Fink has followed the best 
mycological usage of the present day in recognizing the value of spore- 
differences, especially among the crustaceous lichens, where the thalline 
Characters are of such slight importance. The following genera for the 
most part based on spore-differences are recognized in the present work, 
having been included by Tuckerman in other genera: Chaenotheca,. 
Biatorella, Megalospora, Biatorina^ Bilimbia, Bacidia, Rhizocarpon, 
Psora, Toninia, Icmadophila, Synecohoblastus, Gyrophora, Acarospora, 
Haematommia,Art hopyrena, Thelocarpon, Derjnatocarpon. These genera 
are almost universally recognized among European lichenologists, but 
American students have been slow in accepting them on accountof the weight 
of Tuckerman’s authority. Professor Fink has done well therefore in encour- 
aging a more liberal interpretation of generic limits. The recognition of 
