periodicity, determined by the occurrence and 

 length of the vegetational span of the species in- 

 volved . . . .Climax associations are approached 

 in some instances , but they are scarcely to be con- 

 sidered as the counterparts of such aggregations 

 among the higher plants of terrestrial habitats . " 



He says also that it is almost impossible to 

 make a classification of algal communities that 

 will entirely separate one community from another 

 or that has ecological significance. 



Each ecological investigator should deal with 

 the problem in his own way. He should use the 

 classification which seems to fit his data best, or 

 make his own. It is only in this way that a good , 

 basic, and generally acceptable system of com- 

 munity classification will sometime be achieved. 

 I cannot refrain from again quoting from Tiffany be- 

 cause I recently found a statement of his which 

 clearly and succinctly expresses my own views, 

 " . . .we are as yet not in a position to formulate 

 very definite principles regarding algal associa- 

 tions /and7 successions, or even direct relation- 

 ships between algal productivity and special 

 causal environmental factors." 



The last part of the above quotation is a good 

 way to introduce the problem of seasonal distribu- 

 tion . We have a relatively large amount of data on 

 the specific organisms abundant at the different 

 seasons, and on many of the associated habitat 

 factors . This is especially true of the phytoplank- 

 ton . Can we, however, even occasionally be sure 

 just what the chief causal factors are for seasonal 

 abundance, or more particularly for the sporadic 

 blooms of phytoplankton? This is even more true 

 for the littoral and lotic communities where we have 

 much less data. There is general agreement that 

 temperature and light are important in seasonal dis- 

 tribution, but these factors act on a whole spectrum 

 of autotrophic, heterotrophic, and parasitic organ- 

 isms. As pointed out above, we cannot sometimes 

 easily separate the effect of temperature from that 

 of light. Can we ever be quite sure, on the basis 

 of present data, that phosphorus or nitrogen is 

 really a limiting factor in a natural community, ex- 

 cept perhaps for a very short period of time? Some 

 of you have read numerous papers on phosphorus as 

 a limiting factor, but the problem does not seem to 

 be settled yet. Here, it seems to me, is where 

 combination laboratory and field studies of species 

 could give us some exact answers. Laboratory cul- 

 ture work should always be checked against a study 

 of the same species in natural communities . Only 

 such studies give promise of solving the problem of 

 the sporadic, objectional bloom as well as that of 

 seasonal fluctuations . 



It is amazing to those who have had an in- 

 terest in fresh-water algae for many years, how 

 frequently a species first described from one local- 

 ity will turn up next in a locality very remote from 

 the first one. William Bailey (1851) wrote an 



excellent paper on fresh-water algae collected 

 along the south Atlantic, coast. In this paper he 

 described a new desmid genus, Triploceras . His 

 two species were next collected in Scandinavia, I 

 believe. Triploceras is now known from all five 

 continents. Bailey's Ceratium carolinianum was 

 also next found in Scandinavia. The genus Oedo - 

 cladium was first collected in Germany, then 

 Virginia, Puerto Rico, India, and Australia. Oedo- 



cladium operculatum described from Puerto Rico, is 

 common in India and is known also from Missis- 

 sippi. These few illustrations give the pattern, or 

 rather the lack of a pattern, in the known world 

 distribution of fresh-water algae. Sometimes one 

 thinks there is a pattern of distribution for certain 

 species. In 1935 Tiffany described a genus (Clon- 

 iophora) from Puerto Rico which somewhat resem- 

 bles both Stiqeoclonium and Draparnaldia . Re- 

 cently when I found the plant common in Peruvian 

 rivers in the Amazon watershed, I thought, "Here 

 is a tropical species . " When I came to examine 

 the literature, however, I found that the species 

 has been collected widely in the northern hemi- 

 sphere but reported under the name Draparnaldia 

 mutabilis . 



In a review of the geographic distribution of 

 one of the best known families of green algae, the 

 Oedogoniaceae, Tiffany (1957) concludes that some 

 species (of Oedogonium and Bulbochaete ) are cos- 

 mopolitan, the largest aggregation of species 

 occurs in the temperate zone (where most collecting 

 has been done), a few species are arctic, many 

 species are both temperate and tropical, and a few 

 large species are almost exclusively tropical. 

 These conclusions are anything but concise and 

 definite but they indicate the state of our present 

 knowledge. Some of the supposedly rare species 

 have an interesting history. Cyclonexis annularis 

 Stokes, Chrysophyceae, was described from New 

 Jersey in 1886 . It was next found in Germany about 

 1910, then in Ohio in 1933 and in Massachusetts 

 in 1939 . A closely related species was described 

 from Russia a few years ago, and last winter we 

 found Cyclonexis annularis again, in North 

 Carolina. We have three second records of species 

 described in Europe, 30, 40, and 50 years respec- 

 tively after the original collection. The diatom, 

 Actinella punctata , until two years ago was known 

 from only two or three collections in the United 

 States . Since then we have found it at 12 locali- 

 ties in 10 counties in the Coastal Plain of North 

 Carolina . As many as 50 cells were seen in one 

 clump this past winter. Is it possible that if we 

 knew when and where to look there would be no 

 really rare species of fresh-water algae? I believe 

 this is probably true. Most genera have been in 

 existence for a very long time and individuals have 

 become widely distributed into suitable habitats 

 throughout the world . Just the other day I found 

 this statement in Str>:fm's 1924 paper, "They all 



