14 THE MYXOMYCETES 



Decision as to the limits of species and genera must necessarily be a 

 matter of personal judgment, and this is perhaps more apparent in the 

 slime molds, because of their obvious responsiveness to environmental 

 conditions while the fructifications are forming, than in most other 

 groups. We have felt justified in applying a distinctive specific name 

 to any form which shows reasonable constancy under varying condi- 

 tions, even though occasional intermediate forms may appear. The 

 multiplication of varieties has nearly if not quite reached the satura- 

 tion point. Many of the varieties listed in the literature are obviously 

 merely growth forms; some are doubtless autonomous species. If 

 the latter, they will eventually be recognized as such; if the former, it 

 would seem better to modify the diagnosis of the species to accommo- 

 date them, rather than to multiply names. 



The space devoted to synonymy is extensive. It is unfortunate that 

 this should be so, but at present it seems to be necessary. Many 

 synonyms are listed on the authority of earlier students, particularly 

 Rostafinski, and in view of the scanty and inadequate descriptions 

 given in many of the earlier works, many must be regarded as doubtful. 

 Where possible, however, the original descriptions have been consulted, 

 and the attempt has been made to judge their value impartially. We 

 have included either in the synonymy or the appendix many published 

 names which have been applied to slime molds, even certain names not 

 validly published but which have appeared in the literature. If they do 

 nothing else, such compilations help to prevent the publication of 

 invalid names, and, in case of doubt, send the student to original 

 sources for verification of conclusions. 



