EXPLANATIONS AND REFERENCES, 

 PLATE CLXXII. 



PAGE 

 Fig. 1. CALOTHRIX LACUCOLA, ..... 2:->9 



" 2. ('ALOTHRIX CRUSTACEUM, a single plant separated from an in 



crustation, under higher magnification, 240 



" 3. " a section of a shining blackish frond, 240 



Figs. 4, 5. the gray crustiferous form, natural size, 240 



Fig. 6. " " section of a more advanced growth, 240 



"7. " matured, older plant ; ends of tri- 



chomes fibrillose, . . . 240 



