PLAN AND ARRANGEMENT 13 



will not be argued that the best reference has always been used, for 

 in their selection an attempt has been made to use the more readily 

 available literature, insofar as possible that written in the English 

 language. Foreign-language references are used in cases where there 

 is a more recent and more adequate treatment of a particular algal 

 group than exists in English publications. Also, insofar as possible, a 

 single reference has been used for a large taxonomic unit even though 

 a slightly better treatment might be available for a particular genus 

 within the larger unit. Original type descriptions are avoided as much 

 as possible and are never used if there is a more general comprehensive 

 and authoritative reference available. In some cases, unpublished 

 manuscripts have been used as authority for changes of synonomy, 

 and the published references given will not be the best possible but 

 the best which most students will at present have available. The 

 point of view taken here, it is believed, will ease the problem of the 

 less well-trained student and will occasion no hardship on the expert, 

 who will be familiar with other sources. 



Much of the Illinois literature contains only generic names of al- 

 gae, and they have been omitted in the catalog, with the exception 

 that each of the articles has been included in the review of the litera- 

 ture. In using the catalog, the following points relative to arrange- 

 ment of data should be kept in mind : 



1. Synonyms as they occur in the Illinois literature are included 

 in italics. 



2. All species reports are given by counties, which are arranged 

 alphabetically in bold-face type. 



3. Preceding the county name are the names of the authors report- 

 ing the species, the date and page numbers of the reference, and 

 the name under which the species was reported if a synonym. 



4. Following the county name are the names of cities, towns, or 

 other localities near the point of collections, the type of habitat, 

 and the months of collection (in parentheses). 



5. Specific dates of collections are given only for reports from the 

 Field Museum of Natural History and for those of the writer. 



6. Herbarium numbers are given for the writer's collections. 



7. The absence of a reference date after the name of a person re- 

 porting algal species indicates that this information has not 

 previously appeared in print. 



8. In the case of many of Dr. E. N. Transeau's reports, unpub- 

 lished data have been included with published data without dis- 

 tinguishing them. 



9. In some cases the data for a given species are too extensive or 

 otherwise unwieldy to follow the system outlined above. In such 

 cases the data have been separated into two units, the first of 

 which includes references arranged chronologically, synonyms. 



