CHAPTER VI. 



THE BROWN ALG-SJ (Phoeophycece}. 



THESE plants are all characterized by the presence of a 

 brown pigment, in addition to the chlorophyll, which almost 

 entirely conceals the latter, giving the plants a brownish color, 

 ranging from a light yellowish brown to nearly black. One 

 order of plants that possibly belongs here (Diatomacece) are 

 single celled, but the others are for the most part large sea- 

 weeds. The diatoms, which are placed in this class simply on 

 account of the color, are probably not closely related to the 



FIG. 24. Forms of diatoms. A, Pinnularia. i, seen from above ; n, from the 

 side. B, Fragillaria (?). C, Navicula. D, F, Eunotia. E, Gomphonema. 

 G, Cocconeis. H, Diatoma. All x 300. 



other brown algae, but just where they should be placed is 

 difficult to say. In some respects they approach quite closely 

 the desmids, and are not infrequently regarded as related to 

 them. They are among the commonest of organisms occur- 

 ring everywhere in stagnant and running water, both fresh 



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