PLATE XII. 



A. POLYSIPHONIA, page 82. 



Fig. 1, P. variegata ; the natural size. 2, a cera- 

 raidium. 3, a spore. 4, ramulus with immersed te- 

 traspores. 5, a tetraspore. 6, small portion of the 

 stem. 7, cross section of the same, to show the six 

 siphons, surrounding the central tube ; all magnified. 



B. DASYA, page 93. 



Fig. 1, D. arbuscula ; the natural size. 2, ramellus 

 bearing stichidia. 3, a ceramidium. 4, cross sec- 

 tion of the stem ; all magnified. 



C. LAURENCIA, page 97. 



Fig. 1, L. pinnatifida ; the natural size. 2, apex of 

 branch with tetraspores. 3, a tetraspore. 4, apex of 

 a branch with ceramidia. 5, spores ; all magnified. 



D. BONNEMAISONIA, page 97. 



Fig. 1, B. asparagoides ; the natural size. 2, apex of 

 a branch, with ceramidia alternating with the ra- 

 muli. 3, a ceramidium. 4, a spore ; all magnified. 



