THE BROWX ALG.E 205 



CLASS III. THE BROWX ALG.E, OR PH.EOPHYCE^E 



233. The brown algae. The PJcrvj/J/i/cece comprise a very 

 irge assemblage of marine algae, or seaweeds, called the brown 

 Lgae because their chrornatophores are colored brown instead of 

 reen. The brown pigment, however, performs the same sort 

 f work (photosynthesis) as the chlorophyll of the green algre. 

 'he brown algae can generally be recognized at a glance by 

 leir color, but the group is really separated from all other 

 Lasses of algte by certain peculiarities of structure, or mor- 

 hology. The plant bodies in most of the forms are very much 

 irger and more complex than those of any green algse and fre- 

 uently have a degree of differentiation quite above that of the 

 rpical thallus. Indeed, some of the higher brown algae have 

 -ell-defined stems fastened to the rocks by remarkable hold- 

 ists, resembling clusters of roots, and bearing expanded leaf- 

 ke structures of complex and striking forms. Certain types 

 evelop swollen bladders, which contain considerable oxygen, 

 iven off from the tissues, and serve to float parts of the plant 

 i the water. Besides the complexity of the plant body the 

 rown algae are also distinguished by peculiarities of the repro- 

 uctive organs that can only be understood through a study 

 E types. Iodine is obtained from the ash of certain kelps and 

 :>ckweeds. These larger brown algae are also gathered from 

 le rocks and beaches by the peasantry of certain European 

 mntries and by farmers on the New England coast and spread 

 ver farm lands to fertilize the soil. 



234. Life habits. The brown algce are most luxuriant in the 

 Dlder waters of the oceans, where they form extensive growths 

 Long the coasts. Some of the larger forms, as Fucus and 

 (scopliylliun, are known as rockweeds because they cover the 

 3cks between low and high tide marks with heavy fringes of 

 rown vegetation (Plate IV). Other forms, known as the kelps, 

 r devil's aprons, grow below or just at low watermark and some- 

 .mes form large beds attached to the rocks. These larger types 



