THE HAUNTS OF LIFE 57 



the red seaweeds are able to continue the work of assimila- 

 tion in relatively faint light, though they do not form the 

 ordinary kind of starch. It may be noted in passing that 

 the pelagic Sargasso weed consists of pieces of httoral sea- 

 weeds (e.g. Sargassum) which have been torn by storms 

 from the shore and floated outwards. 



It is usually believed that the green Algae came first 

 historically, but it is interesting to notice Brunnthaler's 

 heresy that the red ones are most primitive. His idea is 

 that the red Algae were physiologically best suited for the 

 dim light of very ancient days when the Earth was enveloped 

 in a dense cloud canopy, just as they are nowadays best 

 suited for the deeper waters of the littoral area. Those 

 with brown pigment came next and they were well suited 

 to absorb rays from a somewhat Ughter but still very misty 

 atmosphere. The green Algae came last in the series, when 

 our present-day conditions were estabUshed. They proved 

 very successful and spread from the sea to the estuaries and 

 thence into the freshwaters. 



Physical Conditions. — The character of the shore - 

 faima depends in part on the chemical composition of the 

 water, which shows considerable diversity. This depends 

 on the nature of the rocks and sea-bottom, on what the 

 rivers bring down, and on what the currents sweep along. 

 The nature of the rocks, whether volcanic or calcareous, 

 granitic or sandstone, and so on, is also of much importance, 

 determining, for instance, the nature of the rock-pools 

 and the opportunities for attachment. On the nature of 

 the rocks and sea-floor the vegetation of seaweeds in part 

 depends, and the ' flora ' reacts on the fauna. 



It is part of the definition of the shore-area that it is 

 illumined (hence its rich vegetation), but it is subject of 



