24 THE AGARICACEAE OF MICHIGAN 



with either (a) or (aa). This leads to (b) and (bb) or to the 

 name of the plant. Sometimes the letters are tripled, etc., as 

 (aaa), (aaaa). In that case there are three or more possibilities 

 to choose from. 



Arrangement of Species in the Text 



The student will find, besides the keys, another means of 

 identification. This is an arrangement in the text, by which 

 the species which are the most closely related are grouped side by 

 side. This is called a "natural classification" and is supposed to 

 represent a relation according to the laws of evolution. Authori- 

 ties differ on many points involved in such an arrangement, and 

 hence it was necessary to follow, according to my best judgment, 

 the order which appeared to be at the present time most acceptable. 

 Our knowledge of many species is still too imperfect to expect any 

 final arrangement. Furthermore, the number of species of such a 

 small area of the world's surface as Michigan, is not representative 

 of a like arrangement if applied to all the species of Agarics the 

 world over. In view of this fact it seemed useless to try to be en- 

 tirely consistent throughout the work. The genera are therefore 

 subdivided in the way best adapted for each, although a general uni- 

 formity is approximated. The genera may be divided into subgenera 

 and sections, and sometimes the sections are subdivided. In this 

 way the most closely allied species are usually found together under 

 the last subdivision. 



Nomenclature 



The rules of the International Botanical Congress held at Brus- 

 sels in 1910, have been used (see Authorities and Abbreviations). 

 Synonyms have been purposely omitted except in so far as they are 

 mentioned in the commentaries. The study of synonymies is apt 

 to become a "wild goose chase" and often offers nothing of im- 

 portance for those who wish to become acquainted with the living 

 plants; it is well adapted for those who prefer to make their my- 

 cological studies in the herbarium and library. There is little doubt 

 that in the course of time, some of our American plants which were 

 supposed to be different and were given names, will be found to be 

 synonyms of European species. But there is no need of passing 

 judgment on such till the evidence is all in. Undue haste in con- 

 sidering species identical has often brought about more error than 

 existed in the first place. The field mycologist is constantly finding 

 species which he had given up as hopeless synonyms, and much col- 



