104 THE ALGAE 



{a) mechanical; in this case they would presumably provide 

 resistance to high turgor pressures, although the presence of 

 high osmotic pressures in the cells has yet to be proved; 



(h) to enlarge the protoplasmic surface; 



(c) concerned with diffusion, because movement of mineral 

 salts is more rapid through these strands than through the 

 cytoplasm; 



{d) lost or without any function. 



In addition to the trabeculae there are also internal peg-like 

 projections. Vegetative reproduction occurs through the dying 

 away of portions of the old rhizome thus leaving a number of sepa- 

 rate plants. The s warmers or gametes are formed in the aerial por- 

 tions and are Hberated through special papillae that develop on the 

 frond. The sexual reproductive fronds have a variegated appear- 

 ance caused by the massing of the biflagellate gametes at the differ- 

 ent points, the swarmers in some species being separable into 

 micro- and macrogametes. In certain species the whole plant can 

 produce swarmers, whilst in others the reproductive area is limited, 

 and in such cases the morphological identity and differentiation of 

 the frond becomes of great interest. The thallus can be regarded as 

 composed of a number of individual cells which only become 

 evident at gametogenesis. Fusion between the swarmers has been 

 observed in C. racemosa, and it is probable that in all the species 

 the motile bodies are functional gametes and that the adult plants 

 are diploid. The genus has been much employed in experiments 

 on polarity because the structure of the thallus renders it extremely 

 suitable. 



REFERENCES 



General 



Feldmaniij J. (1946). Compt, Rend. Acad. Sci. (Paris), 222 (13), 752. 

 Feldmamij J. (1954). Rept. Sect. 17, 8th Intern. Bot. Cong., p. 96. Paris. 

 Fritsch, F. E. (1935). Structure and Reproduction of the Algae^ Vol. I, 

 pp. 368-446. Camb. Univ. Press. 



Codium 



Hartmann, M. and Hammerling, J. (1950). Publ. Staz. Zool. Napol., 22 

 (2), 129. 



Halicystis 



Kommann, P. (1938). Planta^ 28, 464. 



