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Abstract
Knowledge of the genus Haematococcus is briefly summarized, the existence in Southern Africa of many habitats suitable to the alga indicated, and the occurrence of the various species recorded.
The cosmopolitan species H. lacurtris is widespread. In addition two new species are described: H. capensis with several varieties and forms already recorded from many localities in both the Western and Eastern Provinces and H. zimbabwiensis as yet known only from Zimbabwe.
The life history of H. capensis, described in detail, is closely comparable with those of H. buetschlii and H. droebakensis. Material of the latter collected at Stonehenge has been kept in culture at the Cape and in Grahamstown for many years. In all three species sexual reproduction is by means of gametes formed in motile cells, and asexually formed resting cells are rare.
Special attention has been given to the behaviour of H. lacustris from numerous sources grown under varying conditions; the dominance of the motile cell in building up the population in this as in the other species is stressed. Reproduction by means of asexually formed non-motile cells, occasional in the other species, has developed to such a degree in this species that it has largely replaced sexual reproduction which is comparatively rare, the gametes being formed not in motile cells but on germination of asexually formed resting spores. Gametes and zygotes have been found once in nature near Grahamstown.
Partial success in applying Peeble's method for inducing sexual reproduction has yielded indications of the existence of two types of naked swarmers: the smaller, gametes which conjugate to form zygotes, the larger of the nature of accessory cells. These develop without conjugation, forming resting spores which eventually germinate producing normal motile cells.
The taxonomy of the genus is discussed, the combination Haematococcus lacustris (Girod.) Rostafinski is maintained and the division of the genus into two genera proposed by Droop considered. Careful comparative studies of the species leads to the conclusion that such a division is not justified and the genus Balticola proposed by Droop is therefore rejected. A key to the species of Haematococcus is included.