194 



COARSER BROWN ALGAE 



of our Atlantic coast have stalked blades ten to twenty feet long. 

 The great bladder kelps of the Pacific, Nereocystis and Macro- 

 cyslis, attain great dimensions, the latter genus reaching a length 

 of 500 to 900 feet and Lessonia with trunk-like stems and leaf- 

 like segments forms veritable submerged forests in the Ant- 

 arctic Ocean (Fig. 120, B, C). These highly organized plants 

 have apparently lost or failed to develop a sexual method of 

 reproduction and depend entirely upon the formation of zoo- 

 spores for their propagation. 





Fig. 120. Three of the larger brown algae: A, Laminaria. B. Lessonia. 



C, Macrocystis. 



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

 {Sargassum) are representatives of a group, Fucaceae, that con- 

 tain the most specialized of the brown algae (Fig. 121). The 

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

 come 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 

 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 

 forking of the stem into two equal parts, a method of branching 



