58 Plant Life and Evolution 



must visit the warm seas of the Tropics, where, 

 especially about the coral reefs, these interesting 

 plants abound. Some of them are fan-shaped, flat- 

 tened bodies; others jointed, much branched, coral- 

 like plants, sometimes having the ends of the 

 branches tipped with bright green tufts of hairs 

 looking like the tentacles of some polyp. Still others 

 have creeping stems from which arise fern-like 

 leaves and send down into the coral sand fine, 

 branching roots. These plants might almost be 

 called plant-corals, since, like the true corals, they 

 possess a calcareous skeleton and play a more or 

 less important part in building up the coral reefs 

 where they grow. Like the animal corals, also, they 

 have been found abundantly in a fossil condition, 

 and there is some evidence that they already existed 

 in the ancient Silurian seas. For a long time these 

 remains were supposed to be those of animals, and 

 it is only of late that the real nature of these fossil 

 Siphoneae has been recognized. 



Green Algae Mostly Fresh-water Types. With 

 the exception of the Siphoneae, most of which 

 are marine plants, the majority of the green algae 

 are fresh-water types. There are, however, two 

 great divisions or classes of algae which constitute 

 the bulk of the marine vegetation, at least along the 

 shore. These are the Brown Algae, or Phaeophyceae, 

 and the Red Algae, or Rhodophyceae, both of which 

 reach greater dimensions than any of the green 

 algae, and are much more specialized. These are 



