600 - Heredity and Evolution 



tion at a very early time, as is indicated in 

 Figure 29-11. 



The Rhodophytes (Red Algae). The red 



algae, of which there are some 2500 species, 

 tend to resemble the brown algae. They are 

 mainly marine and they display a variety of 

 branching forms (Fig. 31-6). However, the 

 rhodophytes generally live in deeper, 

 smoother waters, so that the form, typically, 

 is more delicate and lacy, and their struc- 

 ture is not so tough and leathery. The red 

 pigment (phycoerythrin) of the rhodophytes 



Fig. 31-5. Some brown algae (Phae- 

 ophyta). Many of these multicellular 

 marine plants are tough and leath- 

 ery and can endure the pounding of 

 waves along the shores of the sea. 

 Large brown algae are called kelps. 



absorbs heavily at blue-light wavelengths 

 (p. 162), which penetrate more deeplv into 

 the ocean. The red algae, therefore, can 

 grow at relatively greater depths, where chlo- 

 rophyll alone is not a very efficient photo- 

 synthesizing pigment. 



One group of red algae, the Corallina, 

 plays an important part in the building of 

 atoll reefs (p. 634). These forms accumulate 

 calcium carbonate, which finally makes the 

 lhalhis hard and rigid. Many generations of 

 such algae, each attaching to the bottom and 



