6 HENRIK PRINTZ [1920 



There is no doubt, oii the contrary, that the tnopics — where the 

 climate is not toio drv — have a far richer vegetation of s u b a é r i a 1 

 algae than the teniperate zones. It is particulaiiy the Myxophijceae 

 that are repioited to be dominating, while the Chlorophijceae are 

 playing a more modeist part. ()n Ihis comp. e. g. Fritsch, A 

 General Gonsidcration of the Subaerial and Fresh-water Algal 

 Flora of Ceylon. A Contril>ntion lo the Study of Tropical Algal 

 Ecology (Prooeed. Royal. Soc. Vol. 79, 1907) and Wille, Report 

 on an Expediliion to Porto Rico for collecting Fresh-water Algae 

 (Journ, New York Bot. Garden, 1915). It is therefore not super- 

 fluous to point out especially that the bulk of the algae that occur 

 in the samples from South Africa, examined l)y me, are Chloro- 

 phyceae, while the Myxophijceae liave been oljserved only in a 

 few samples, and in none of them in any particular abundance. 

 Thus, the total number of the Myxophijceae observed iis only 5. Tlie 

 possibility is not precluded, however, that this, partly at least, may 

 be due lo the collecting. 



As is well known, Ihe freshwater algae evince, on the whole, 

 a striking cosmopolitanism in their distribution, a nalm'al con- 

 sequence of the uniform character of the surroundings. On the 

 other hånd, il is to be cxpecled that the various subaerial algae — 

 thougli Ihey are at least as eaisily spread by their akinetes, aplano- 

 •spores, and in other ways — like the lerrestrial flora on the wliole, 

 will appear lo be more directly dependent on the cliniatic con- 

 dilions, as d a m p n e s s o f the air, temperature, w i n d, 

 size ol the a m p 1 i t u id e s, etc. As to the demands of life of 

 the algae, their conditions in air will be exposed to greatcr varialionis 

 than in water in the same piaces. It does nol therefore follow that 

 the freshwater algae are cjuite independent of the environments, 

 bul liere, no doubt, the c h e ni i c a 1 and p h y s i c a 1 states 

 of the water lake a vital part. In an earliier paper: Krisliania- 

 traklens Protococcoideer (Krisliania Videnskabsselskabs Skrifter, 

 1914), I have, by the way, poinled out the ralher essential diffe- 

 rence in the composition of the algal vegetation ol the Iracts west 

 ol Kristiania, abounding in lime, and the localities- poor in lime 

 and abounding in liuniic acid in the eastern neighl>ourliood ol the 

 town. Indeed, to the freshwater algae the heighl above the level of 

 Ihie sea seems to be ol no considerable imporlance, at least not 

 belore the absoluitely arctic coaiditions begin to asisert themselves. 

 Most species of algae, al least the most general ones, the distribu- 

 tion ol wliicli is laiown witli same degi^ee of certainty, thus are 

 found nearly all m'er the world, apparently quile independent of 

 geographic limitations as well as olimatic condilions. Under extreme 

 conditions only, e. g. in absolutely arctic countries oi' high up in 

 the mountains, there apparently occur a few particular species, e. g. 



