134 



SEAWEEDS 



interwoven like so many other 

 multinucleate Algae. 



In the thallus of Codium two 

 layers may be distinguished, 

 though their component elements 

 are all branches of the same cell. 

 In the middle there is a densely 

 interwoven mass of filaments 

 which end outwards in club- 

 shaped apices arranged perpen- 

 dicularly to the surface. These 

 club-shaped ends lie parallel to 

 each other, and form a kind of 

 pallisade tissue (Fig. 35). The 

 spongy thallus so formed is of 

 varying habit, either elongate 

 and dichotomously branched (C. 

 tomentosum), or in globular cush- 

 ions, or flat and encrusting, with- 

 out definite stalk and with very 

 slightly developed rhizoids. The 

 lumen of the cell is sometimes 

 interrupted (apart from the 

 formation of reproductive bodies) 

 by plug-like thickenings of the 

 membrane. 



In Dcrlesia, the single fila- 

 ments of the thallus show no 

 differentiation of frond. They 

 are dichotomously but sparingly 

 ,. branched, and are rarely, but 

 : with no regularity, septate in 



