^f^^ 





■'V.. 



THE SEASONAL LIFE-CYCLE OF SOME RED ALGAE AT 



WOODS HOLE 



I. F. LEWIS 

 University of Wisconsin, Madison, Wis. 



The complete life-cycle of the red algae has been a subject of 

 speculation rather than exact knowledge. For various reasons 

 the Florideae have not been much studied dui'ing the winter, 

 and the difficulty of cultivating them in the laboratory has pre- 

 ^^ented satisfactory experimental work. In the course of some 

 field work done at Woods Hole in 1911-1913 it has been possible 

 to follow the history of certain typical species throughout the 

 year. 



Some of these results have already been published. ^ In the 

 present paper will be given the conclusions drawn from some cul- 

 tures of Dasya elegans, Grifithsia Bornetiana Farlow ( =(?. globifera 

 Ag.), and Folysiphonia violacea, which lasted from July, 1912, until 

 August, 1913. 



Both tetraspores and carpospores of the species mentioned 

 were sown on oyster shells in the laboratory in July, 1912. In 

 about twenty-four hours, when the resulting sporelings were 

 firmly attached, the shells were clamped to boards by means of 

 galvanized iron screws, and the boards were then nailed to the 

 piles at the outer end of the Fay Wharf. 



In August of the same year the shells were examined in a 

 cursory way, and cumulative evidence was obtained corroborat- 

 ing the previous conclusions that tetraspores produce sexual 

 plants without exception. The shells on which tetraspores had 

 been sown were covered with a dense growth of young plants 

 which random samplings showed to be sexual. The carpospores 

 produced an equally vigorous growth, but no fertile individuals 

 were found. 



1 I. F. Lewis, Alternation of generations in certain Florideae. Bot. Gaz. 53: 

 236-242. 1912. 



31 



THE PLANT WORLD, VOL. 17, NO. 2, 1914 



