Marine Algae of the Cape Peninsula 57 



latter position it is one of the most slippery of all the South African 

 Algae that I have as yet met. Porphyra, which is of almost 

 world-wide distribution, grows hanging from the bare rock or 

 amongst a tangle of other fronds; it is generally abundant in the 

 neighbourhood of drain pipes or around the bathing pools of these 

 coasts. It varies in colour from a deep purplish red to a pale 

 yellow. The pale yellow fronds are generally smaller, about 

 Yl inch to 3 inches long, and when examined microscopically may 

 be seen to be giving off solitary spores which from analogy with 

 their nearest allied seaweeds we must call monospores. The large 

 purple fronds, often 12 inches or more in length, on the other 

 hand often have brownish red edges, and these are the regions 

 where reproductive organs known as carpospores are formed in 

 little packets. As these packets are shed into the water the frond 

 loses its colour and appears with a whitish edge. The two kinds of 

 plants probably alternate with each other, the red spores produc- 

 ing the small plants which in their turn produce the solitary spores 

 and presumably these grow into the large fronds. This sequence has 

 never been observed for any species of Porph^ra, but with a 

 marine aquarium there is little doubt that something of the kind 

 could be observed. The large carposporic fronds of Porph^ra 

 are the most resistant to drought and to exposure to light. 



The distribution of Algae on a coast may often be found to 

 give a more or less definite zonation. On the whole the green or 

 blue green forms are found near the higher tide levels. 

 On the shore at Sea Point, for instance, there are many pools 

 filled wdth the bright green fronds of Ulva and of species of the 

 socalled Sea grass, or Enter omorpha. These, like Porphyra, 

 can endure bright sunlight for some hours at a time. They also 

 flourish best within reach of sewage or other organic contamination 

 of the water. Some years ago at Southampton Ulva increased 

 in the harbour to such an extent that it became a nuisance to the 

 inhabitants, owing to its liberation of sulphuretted hydrogen when 

 decaying. An investigation was made to find a practicable method 

 of exterminating the plants, but the only suggestion made was 

 that of cutting the fronds at intervals and removing them. There 



