52 BOTANY, 



While the plant here described may be taken as a type of 

 the group, it must be borne in mind that many of them differ 

 widely, not only in the structure of the plant body, but in the 

 complexity of the sexual organs and spores as well. The 

 tetraspores are often imbedded in the tissues of the plant, or 

 may be in special receptacles, nor are they always arranged 



FIG. 30. Marine red seaweeds. A, Dasya. B, Rhodymenia (with smaller 

 algse attached). C, Grinnellia. D, Delesseria. A, B, natural size ; the 

 others reduced one-half. 



in the same way as here described, and the same is true of the 

 carpospores. These latter are in some of the higher forms, 

 e.g. Potysiphonia (Fig. 29, F), contained in urn-shaped recepta- 

 cles, or they may be buried within the tissues of the plant. 



The fresh-water forms are not common, but may occasionally 

 be met with in mill streams and other running water, attached 

 to stones and woodwork, but are much inferior in size and 



