PLATE XVI. 



A. Rhodymenia, page 124. 



Fig. 1, R. laciniata ; the natural size. 2, 3, portions 

 of the margin, with coccidia of different sizes. 4, 

 portion of the margin, with sorus. 5, tetraspores ; 

 all magnified. 



B. SpHiERococcus, page 128. 



Fig. 1, S. coronopifolius ; the natural size. 2, frag- 

 ment, with fructification. 3, a tubercle. 4, longi- 

 tudinal, and 5, transverse, slices of the frond; magni- 

 Jied. 



C. Gracilaria, page 128. 



Fig. 1, G. confervoides ; the natural size. 2, vertical 

 sections of tubercle. 3, longitudinal, and 4, trans- 

 verse, slices of the frond. 



D. Hypnea, page 130. 



Fig. 1, H. purpurascens ; the natural size. 2, frag- 

 ment of a branch, with imbedded tubercles. 3, a 

 tetraspore. 4, longitudinal, and 5, transverse, slices 

 of the frond ; all magnified. 



