140 Chlorophycese 



developed luxuriantly, being represented by a large number of forms. The 

 ability of these Algae to grow in loose, muddy or sandy bottoms enables them 

 to occur in great masses and extend to a depth of more than 20 fathoms. 

 Many of them are also incrusted with lime and they contribute greatly to the 

 various marine deposits, not merely in the bays and lagoons, but also in the 

 more open sea. The gravelly sea-shores of these regions often consist very 

 largely of the remains of calcareous Green Alga?. 



There are some small marine genera of the Ulotrichales, mostly epiphytes, 

 and a few marine species of Ulothrix. The latter appear to be confined to 

 northern seas, being strangely absent from the tropics. There are also a few 

 marine species of Prasiola, but of the large group of the Protococcales scarcely 

 half-a-dozen live in marine habitats, and only one is of importance, viz. 

 Halosphtera viridis. There are no marine forms of the Heterokontse, nor of 

 the Conjugates. 



The brackish-water Chlorophyceae are very scanty, consisting of a few 

 species of the Ulvales and of the Cladophoracese, together with some species of 

 Vaucheria and Ulothrix, to which can be added a few members of the Proto- 

 coccales, such as Oocystis submarina and Brachiomonas submarina. 



It has been found that certain freshwater members of the Chloro- 

 phyceae are able to adapt themselves to an existence in salt water. 

 Richter ('92) stated that the lower the organization of the Alga the better its 

 power of adaptation, but Comere ('03) found that only those Alga? with a 

 robust structure could successfully withstand immersion in salt water. Comere 

 succeeded in growing species of (Edogonium and a freshwater species of 

 Cladophora in water containing 3'5 per cent, of sodium chloride, Vaucheria 

 sessilis in water containing 2 per cent., and some of the large species of 

 Spirogyra in water containing from T8 2 per cent. Richter affirmed that 

 (Edogonium, Spirogyra, or Vaucheria have less power of adaptation to life in 

 salt water than Stichococctts or Tetraspora, but this statement has not been 

 verified. Notwithstanding the somewhat contradictory nature of Richter's 

 and Comere 's experiments, it appears that certain of the freshwater Chloro- 

 phycea? can adapt themselves to an increasing salinity of the water in a 

 manner comparable with the adaptation of a few forms of the Green Algae to 

 a life in hot water. Both these observers found that in all cases the salinity of 

 the water caused the cells to increase in size, and when the concentration was 

 high malformation of the cells invariably occurred. Starch at first disappeared 

 from the cells, but reappeared when the adaptation was more complete. 



Techet ('04) has found that many of the marine Chlorophycea? exhibit 

 great power of accommodation to changes in the salinity of the water. 

 Experiments with Cladophora trichotoma showed that this Alga could with- 

 stand a salinity from 1*8 per cent, to 8'5 per cent., and that when the salinity 

 reached 13'2 per cent, the plant produced quantities of zoogonidia and then 



