1 86 



STRUCTURE OF FUCUS 



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 

 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 



h-cr 



Fig. 122. Structural features of Fucus: A, cross-section of a portion of 

 the central stem-like part of the plant, showing an epidermal, c\ cortical, 

 cr, and central region, c. B, section of one of the cavities that appears to 

 the eye as a dot. See Fig. 121, B, g. This cavity contains only male 

 gametangia. C, section of a cavity from another plant contains only female 

 gametangia. — After Oltmann. 



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 

 called dichotomy in contradistinction to the axial branching 

 characteristic of the majority of our flowering plants. Fucus, 

 like many of the gross brown algae, contains air cavities or 



