PLATE XXI. 



A. Gloiosiphonia, page 152. 



Fig. 1, G. capillaris ; the natural size. 2, ramuli, in 

 fruit. 3, transverse section of a branch, showing the 

 tubular frond. 4, portion of the wall of the frond, 

 with favellidium ; all magnified. 



B. Nemaleon, page 153. 



Fig. 1, N. multijidum ; the natural size. 2, filaments 

 from the periphery of the same. 3, favellidium sur- 

 rounded by moniliform filaments; both magnified. 



C. DuDRESNAiA, page 154. 



Fig. 1, D. divaricata ; the natural size. 2, segment of 

 a cross section of the frond. 3, favellidium ; both 

 magnijied. 



D. Crouania, page 155. 



Fig. 1, C. attenuata, growing on Cladosteplius spongi- 

 osHS ; the natural size. 2, portion of one of the 

 branches. 3, whorl of ramuli from the same. 4, te- 

 traspore attached to one of the whorled ramuli ; all 

 magnified. 



