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Annals New York Academy of Sciences 



authors were then determined for each genus and species. The algae were 

 arranged in the order of decreasing emphasis by the authors as a whole as in- 

 dicated by the comparative total scores for each alga. Theoretically an alga 

 considered as very highly tolerant by all 110 authors would have had a perfect 

 score of 110 multiplied by 2, or 220 total points. 



For studies in sanitary science the algae are frequently placed into four 

 groups. All flagellates containing photosynthetic pigments constitute one of 

 the four groups. The other three groups are the blue-green algae, the diatoms, 

 and the green algae, the last group including all of the nonflagellated green, 

 yellow-green, and other related forms. 



Table 1 

 Pollution Algae 



Most tolerant genera, by groups 



Table 2 

 Pollution Algae 



Most tolerant species, by groups 



All four groups are well represented among the genera and species with high 

 scores as pollution-tolerant algae. For example, of the 10 genera with the 

 highest scores, 2 are blue-green algae, 2 are flagellates, 3 are diatoms, and 3 are 

 green algae (table 1). Of the four species with the four highest scores, each 

 belongs to a different group. Among the 50 most tolerant species, the range in 

 number per group is from 10 to 15 (table 2). 



The 52 most tolerant genera are listed in table 3. Leading the list, in order 

 of decreasing total scores, are Euglena, Oscillaloria, Clilamydomonas, Scenedes- 

 mus, Chlorella, and Xilzschia. The first two were considered as tolerant genera 

 by 62 and 61 authors and rated 110 and 105 total points, respectively. These 

 are in contrast with the fiftieth genus, Cocconeis, which was referred to by only 

 8 authors for a total score of eight. 



