ALG^E 



121 



of their bodies are huge. Ectocarpus may be used to 

 illustrate the essential features of the group. Its body is 

 filamentous (Fig. 113), suggesting the body of some of the 

 Conferva forms among the green Algae. Certain 

 cells of the filament (Fig. 113, A), or the end cells 

 of special short branches, become enlarged and 

 produce numerous swimming spores. The swim- 

 ming spores of brown Algae are peculiar in usu- 

 ally bearing the two cilia on one side of the body 

 rather than at one end, and hence 

 they are described as laterally bicili- 

 ate (Fig. 115, G). 



The cell that produces swimming 

 spores was sometimes spoken of 

 among the green Algae as a mother- 

 cell, but a mother-cell may not al- 

 ways produce spores. 

 Hence it is well to use ~ 



a term that implies the 

 product of the mother- 

 cell, and in this case 

 the term is sporangium 

 (spore-case). A sporan- 

 gium, therefore, is an or- 

 gan that produces spores; 

 and among the Algae de- 

 scribed thus far it con- 

 sists of one cell. 



In addition to the one- 

 celled sporangia, other 

 organs in similar posi- 

 tions may occur; but 

 they differ from the spo- 

 rangia in being many-celled (Fig. 113, B). In -each cell 

 usually one body is formed, which when discharged is seen 



B 



FIG. 113. Ectocarpus: a filamentous, branch- 

 ing form: A. filament bearing one-celled 

 sporangia (); B, filament bearing many- 

 celled gametangia (#). 



