EXPLANATIONS AND REFERENCES, 

 PLATE CLXX. 



PAGE. 

 Figs. 1, 2. CALOTHRIX RADIOSA, two plants drawn on a small scale, . 538 



3, 4. CALOTHRIX HOSFORDII, a variety which appears to hold a posi- 

 tion hetween C. radiosa and Oalothrix 

 Meneghinmna, . . . 238 



Fig. 5-7. CALOTHRIX MENEGHINIANA, three variously developed forms, 238 

 Figs 8, 9. Young conditions of growth of the plants of this plate, . 238 



