1914] 



BURT THELEPHORACE^ OF NORTH AMERICA. I 189 



Europe. In the later pages names of the many botanists who 

 have participated in this work by the contribution of speci- 

 mens from their respective regions are given in connection 

 with the specimens. I feel my obligation to each of these cor- 

 respondents. 



Having become thoroughly familiar with the species of a 

 family of fungi, one then faces the task of deciding under what 

 genera they shall be grouped in order that others may more 

 easily recognize them. Our studies in systematic botany and 

 the accumulations of plants in herbaria are primarily for the 

 purpose of enabling those who wish to obtain information about 

 any particular plant, however obscure, to determine its name 

 accurately and so be in a position to get at the world's literature 

 and knowledge concerning that species; and also to enable 

 botanists so to entitle and index their researches that the 

 results will be more available to the world at large. Stability 

 in the nomenclature of plants is therefore important, and revo- 

 lutionary changes in generic conceptions should not be lightly 

 and frequently made. Whenever one proposes new genera to 

 supersede a well-established genus which has satisfactorily 

 embraced the related species of the world, the burden of proof 

 should be on the one who makes the change to demonstrate 

 that the advantages from the innovation will more than com- 

 pensate for the confusion which would result as well as for the 

 loss of knowledge indexed under the superseded name. 



Many new genera of fungi have been proposed during recent 

 years. These have frequently come from students with a 

 limited knowledge of the species of the world. It is not sur- 

 prising that a botanist working on the few species of a limited 

 region should be led to the establishment of new genera on the 

 basis of what seem to be sharp differences in his species or groups 

 of species. When, however, his knowledge encompasses just 

 as definitely the structure of the many species of some large 

 portion of the world, his perspective changes, and he may now* 

 find that the species which he formerly regarded as generically 

 distinct are so closely connected by intermediate species that 

 the contemplated generic separation would be unnatural and a 

 hindrance to botanical progress. It is fundamental that genera 

 be so sharply defined that any accurate observer who will make 



