THE SEASONAL CYCLE OF RED ALGAE 35 



Interesting data have recently been furnished by Davis^ of the 

 seasonal distribution of marine algae at Woods Hole. Excluding 

 the Nemalionales, 65 species of Florideae are covered in Davis' 

 list with particulars of their seasonal occurrence. Of these, 53 

 are found in summer, 8 of which also occur in spring. The con- 

 clusions set forth in the present paper apply more particularly 

 to these summer forms. Tweh'e species are mentioned by Davis 

 as occurring at all seasons, and of these only one (Agardhiella 

 tenera) shows the two generations clearly separated in point of 

 time. In this species the second generation (sexual individuals) 

 occurs like the first on stones, and not, as is so often the case, 

 on eel grass and on other algae. 



It may be mentioned here, however, that though Davis speaks 

 of this species as occurring in ''summer, undoubtedly at other 

 seasons," no specific records are given of its collection in winter. 

 The present author's observations on Agardhiella were all made 

 near the entrance to Eel Pond, and here it may be stated with 

 certainty that the approach of winter witnesses the death of all 

 the larger individuals. In spite of Davis' statement, therefore, 

 Agardhiella should be classed, as far as the present discussion 

 goes, with the summer forms. This leaves all the perennial 

 species as exceptions to the general rule given above. 



SUMMARY 



The tetraspores of Dasya, Griffithsia, and Polysiphonia violacea, 

 abundant in July, produce a second generation of sexual plants in 

 August. Carpospores from these produce sporelings which sur- 

 vive the winter by means of resistant holdfasts. All older plants 

 perish. The surviving sporelings are prevailingly tetrasporic, 

 which accounts for the predominance of tetrasporic plants in 

 early summer. 



Probably the majority of summer species on the New England 

 coast behave as the species mentioned. There are, however, 

 a number of exceptions to the general rule, and the conclusions 

 reached do not apply to the perennial species. 



^ Davis, B. M., A catalogue of the marine flora of Woods Hole and vicinity. 

 Bull. U. S. Bureau of Fisheries 31: part 2, pp. 795-833. 1911. 



