PLAN AND ARRANGEMENT 

 OF THE CATALOG 



The catalog has been arranged as simply as possible to bring to- 

 gether in as brief a summary as seems feasible all the information 

 concerning Illinois algal species that is known to the writer. The 

 genera and species are presented in a classified form, following with 

 but minor modifications the scheme of classification of G. M. Smith's 

 "Freshwater Algae of the United States." The algae are listed alpha- 

 betically by genera in each family and by species in each genus. Syn- 

 onomy has been brought up to date in all cases where such corrections 

 seemed possible with reasonable accuracy. Species which could not 

 be corrected or which for other reasons appeared to be worthless have 

 been listed separately as "Excluded Species" (see. p. 154). It is per- 

 haps possible that some of these excluded species can be shown by 

 some workers to merit a place in modern interpretations of the algae 

 and for this reason they are included here. The problem of correcting 

 synonomy is at best a hazardous one when no specimens are available 

 for study, and usually a bare name is the only point of departure. 

 The assumption that identifications were correct in the first place 

 undoubtedly results in some error, but it is believed by the writer 

 that such errors are a minimal possibility in the Illinois reports, since 

 much of the more important work has been done by recognized 

 specialists, and those reports from other workers perhaps not so 

 critical almost invariably involve the commoner species, which al- 

 most any algologist should recognize. A further ever-present diffi- 

 culty is the difference of opinion existing between specialists as to 

 where a species belongs and what the valid name of it should be. An 

 attempt has been made in this catalog to follow insofar as possible 

 the opinions of an accepted specialist for each group. For those who 

 differ in their opinions as to the proper disposal of a given species, 

 the original synonyms will be found carefully preserved here readily 

 available for further change. Perhaps the only algal group for which 

 there will be any considerable difference of opinion is the Bacil- 

 lariophyceae, and there seems no way of resolving the many conflict- 

 ing points of view in this group. 



It will be noted that following the name of each species a reference 

 is given. The writer has had a two-fold purpose in mind in including 

 these references. In the first place, they indicate a modern authority 

 as to the validity of the species, and will establish the writer's reason 

 for correcting synonomy in each case. Secondly, in most cases these 

 references furnish a readily available means of finding more or less 

 modern descriptions and other information about each species. It 



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