514 Annals of the South African Museum. 



(c) Volvox scarce or absent, Sphaerocystis dominant, Kirchneriella 



fairly numerous; 



(d) Vegetation consisting almost entirely of the palmelloid form of 



Sphaerocystis Poweri ; pool almost dry. 



6. A summary of the seasonal history from November 1931 to 

 April 1932 of Pool I and its vegetation is given in tabular form. 



DISCUSSION AND CONCLUSION. 



Occurrence in a region of summer rainfall appears to be peculiarly 

 favourable to the development of Volvox all the three species found 

 in the Kimberley district are outstanding either for their size, e.g. 

 V. gigas and F. africanus, or for the extreme richness of development, 

 e.g. the reproductive cells of F. Rousseletii, particularly the sexual 

 cells. With this may be compared F. amboensis, Kich and Pocock 

 (loc. cit., p. 462), from a region which has very similar climatic conditions 

 to Kimberley. That a comparatively high temperature is favourable 

 for development in Volvox was also suggested by observations in 1931 

 of F. capensis on the Cape Flats. 



The same is true of the associated algae, all of which are large of their 

 kind even the Eudorina colonies are unusually large, the Kirchneriella 

 is larger than anything previously recorded for the genus, while 

 Sphaerocystis Poweri shows great luxuriance of growth. 



Of recent years much work has been done on the algae of South 

 Africa, but mainly from the systematic standpoint, consisting in the 

 identification and description of species and records of occurrence as 

 shown by more or less isolated collections. As yet the ecological 

 aspect has hardly been touched ; quite recently an ecological study 

 of the plankton of various pans and other inland waters has been 

 published (Hutchinson, Pickford, and Schuurman, 1932), but even 

 this very interesting piece of work deals with seasonal observations 

 in two only of the localities under review. A more detailed study 

 of the seasonal changes in planktonic life, extending over a period of 

 two years, was made in the case of Florida Lake, Johannesburg, 

 by Miss Schuurman (1932). Both these papers deal only with the 

 plankton. As yet no study of the seasonal succession of the algal 

 vegetation as a whole has been published for any piece of water in 

 South Africa. Further, in most cases the pans or vleis concerned in 

 these two papers are either permanent (e.g. Florida Lake), semi- 

 permanent, or extensive artificial bodies of water very different from 

 the small temporary pools near Kimberley. Such rain-water pools, 

 either as in this case in artificially made hollows in the surface of the 



