THE RED ALG^E 213 



leaf-like branches which resemble foliage, (2) berry-like floats, 

 and (3) small reproductive branches, or receptacles (Fig. 200, r). 

 Some species of Sargassum, when torn away from their at- 

 tachment to rocks, are able to vegetate in the open sea, where 

 they are called gulf weed, but they are not known to fruit in 

 the free floating condition. Certain ocean currents carry and 

 accumulate immense quantities of this floating gulf weed in 

 great eddies in the ocean, forming the Sargasso seas. 



239. Summary of the brown algae. The Phceopliycecc stand 

 entirely apart from the green algae as a side line of plant evolu- 

 tion. There is much evidence that it is a group of very ancient 

 origin, probably arising from an ancestry of motile organisms 

 (somewhat like the flagellates) just as did the green algse in 

 early geological ages. The brown algie have developed in their 

 own peculiar ways the largest and most complex forms of plant 

 bodies in the thallophytes, and also some very high types of 

 sexual reproduction. It is clear, however, that these have no 

 relation to higher plants, bryophytes and pteridophytes, and are 

 also entirely independent of other groups of algre. Thus heter- 

 ogamy in the brown alga? has been developed entirely independ- 

 ently of heterogamy in the green alga?, illustrating very well 

 how similar results mav be worked out through different evo- 



/ 



lutionary lines independently of one another. 



CLASS IV. THE EED ALG.E, OR RHODOPHYCE^E 



240. The red algae.* The Rhodopliycece include the most 

 beautiful of the marine algre, for many of the forms are exqui- 

 sitely colored in clear shades of red, and are extremely delicate 

 in structure. Other forms are brownish red or purplish, and cer- 

 tain types are greenish. The pigment is held in chromatophores, 



* To THE INSTRUCTOR : In a brief course where only one type can be 

 studied in the laboratory, Nemalion or Batrachospermum is preferable, fol- 

 lowed by a study of the life habits of the group and demonstrations of 

 herbarium material. 



