250 The Plant World. 



kev to the genera, and descriptions of the famiHes, genera, and 

 species represented in Minnesota, keys to the species being given 

 wherever necessary. In this part of his work Professor Fink has 

 of course been guided in his arrangement by the views of several 

 authors, especially Dr. Alexander Zahlbruckner, but he has been 

 courageous enough to arrange the fam.ilies and genera according 

 to his own ideas. His system naturally differs widely from that 

 of Tuckerman, the only other independent American writer, 

 while he recognizes some genera not accepted by Zahlbruckner 

 in Engler and Prantl and discards other genera held valid by 

 m.any European authors. But in the present unsettled state of 

 nom^enclature in cryptogamJc botany it would be strange were it 

 otherwise. In his definition of species the author has in the m.ain 

 followed the treatment of Tuckerman, tending to consider a 

 species as a group composed of a number of sub-species and va- 

 rieties. 



The treatment of the different genera naturally differs some- 

 what; that of the Cladonias is particularly good, as that genus is 

 exceedingly well represented in Minnesota. As Professor Fink 

 is our forem.ost American student of this most puzzling group 

 this adds a special value to the work. 



The descriptions in general are terse without being scrappy, 

 and clearer and in simpler language than any ever before written 

 dealing with our eastern lichens. In each instance the technical 

 description is followed by valuable observations and data on the 

 distribution of the species both in Minnesota and elsewhere. 

 All chemical tests for the determination of species are omitted, 

 thus disregarding the practice of the European lichenologists'. 

 The text figures and many of the plates are valuable in exe:7;- 

 plifying the structure and spore characters, while the plates 

 m.ade from field photographs of growing lichens are one of the 

 most valuable features of the book. The addition of a glossary 

 is a commendable feature enabling those not specialists to use 

 the work more readily. 



For the region east of the Rocky mountams and north of 

 the Gulf states the work will serve satisfactorily for the determi- 

 nation of nearly all lichens found therein, while it will be an in- 

 dispensable work of reference for the student of lichens in any 

 part of North America outside the strictly tropical portion. 



