206 



COARSER BROWN ALGAE 



as a source of potassium (see page 48), from 23 to 48 per cent, 

 of their dry weight being potassium chloride. It is estimated 

 that there is between 600 and 800 sq. miles of these plants on our 

 Pacific coast and that they should yield annually one million 

 tons of potassium chloride, valued at 40 million dollars. 



The rock weed or bladder wrack {Fucus) and the gulf weed 

 (Sargassum) are representatives of the second group, Fucaceae, 

 that contain the most specialized of the brown algae (Fig. 121). 

 The Sargassum with its stem and leaf-like organs which may 

 become modified into air sacs and reproductive organs bears the 

 closest external resemblance to the higher plants of any of the 

 algae (Fig. 121, A). It forms the major portion of that floating 



r»^ . 



Fig. 121. Two common forms of the Fucaceae: A, Sargassum, the stem- 

 like axis bearing air sacs, s, and leaf-Hke organs; g, reproductive branches. B, 

 Fucus — s, air sacs; g, reproductive branch. C, young plant. 



vegetation in the Atlantic known as the Sargasso Sea. The 

 bladder wracks may be found firmly attached to the rocks by 

 disc-like holdfasts in almost all colder, temperate and northern 

 seas (Fig. 121, B). The elongation of the flat leathery stems 

 is largely localized in a terminal cell and results in a regular 



