Nr. 1] SUBAÉRIEL ALGAE FROM SOUTH AFRICA 5 
found both at Durban, which is a damp place, and at Saldanha Bay, 
with a very dry climate — two places being also very far apart 
— allows the conclusion that the composition of the subaérial algal 
vegetation is rather homogeneous over large parts of the South 
African continent, and mainly conformable to the following 
treatment. 
As compared with the freshwater algae, it is only a very ineonsi- 
Gerable number of species and. genera that occur as true aérophilous 
algae, — that is, algae which are reduced to cover their consumption 
of water by absorbtion of atmospheric moisture, and which survive 
the usually frequent dry periods, on which they are conditional by 
their mode of living, without undergoing any particular resting 
stages. 
In my material from South Africa I have been able to dis- 
criminate 22 different species, 11 of which, or precisely one half, are 
new ones. 5 of them even belong to genera, hitherto unknown. 
Inis result is not surprising, considering our extremely slighit 
knowledge of the subaérial algae of the southern hemisphere. In 
addition to these were further encountered three species which 
were not present in sufficient material for adequate determination. 
If compared on the basis of the present material, the flora of 
subaérial algae in South Africa will be seen to have åa comparatively 
small number of species in common with the one occurring in 
northern Europe, viz. Ghlorella vulgaris, Pleurastrum lobatum, 
Stichococeus variabilis, Hormidium flaccidum, Trentepohlia 
aurea, Tr. umbrina, and Dactylococcopsis rhaphidioides. Im the 
main features, however, the growth-forms are identical 
in type, but the bulk of the constituents belongs to other genera 
and species — the floristic composition being rather 
different. Å comparison of the freshwater algae from the said 
places, on the other hand — if. e. g. the species from South Africa, 
given by FRiTscH, 1. c., are compared with the species occurring in 
northern Europe — will evince a much closer conformity. 
Among phycologists the apprehension is generally reigning, that 
the tropics are more deficient in freshwater algae than e. g. the 
temperate zones. Whether they are absolutely right, I somewhat 
doubt, however. It must be kept in mind that by far most of the 
collections of algae brought home from the tropics, have been coil- 
lected by travellers, who have been mainly interested in other bran- 
ches of science, and that the collections thus ought to be considered 
as rather accidentally brought together, and not giving any exhau- 
stive idea of what is really to be found in the places. Further, for 
a successful collection of freshwater algae is needed not a smal! 
amount of experience. I therefore at present consider the accounts 
of the supposed sparsity of freshwater algae in the tropics as not 
EN 
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