Chroococcacece 



351 



brown integuments (fig. 165 B), and Gl. Ralfsiana (Hass.) Kiitz. with bright 

 red or purple integuments, are two of the best-defined species. Most of the 

 species occur on wet or dripping rocks, generally in association with other 

 Myxophycese. 



J 



Genus Aphanocapsa Nag., 1849. 

 aggregated to form small 

 colonies within a com- 

 mon homogeneous in- 

 tegument. The genus 

 only differs from Apha- 

 nothece in its globose 

 cells. The integument 

 may be colourless or 

 tinted brown or blue- 

 green, and the cells are 

 of a blue-green or olive- 

 green colour. 



There are four British 

 species occurring both in 

 stagnant water and on wet 

 rocks. A. Grevillei (Hass.) 

 Rabenh. is the most fre- 

 quent ; diam. of cells 3'4 

 4-5 p; fig. 165 A. 



The cells are globose and 



C 



D 



Fig. 165. A, Aphanocapsa Grevillei (Hass.) 

 Eabenh., from Helln Pot, W. Yorks. B, Glceo- 

 capsa Magma (Breb.) Kiitz., from Boston Spa, 

 W. Yorks. C E, Gl. polydermatica Kiitz., from 

 Boston Spa, W. Yorks. (All x 450.) 



Genus Porphyri- 

 dium Nag, 1849. The 

 cells, which are closely arranged to form a thin gelatinous stratum, 

 are globose or angular by compression. The stratum consists of 

 many layers of cells, and the cell-contents are of a reddish-purple 

 colour. Cell-division takes place in all directions. 



P. cruentum (Ag.) Nag. is a common Alga, forming a thin slimy stratum 

 of a dark red colour on damp ground and near the base of damp walls. The 

 cells are 7 9 /A in diameter. 



This Alga was at one time placed in the Chlorophycese and has since been 

 relegated to the Rhodophyceae. I agree with Hansgirg, however, in thinking 

 it much better placed in the Myxophycese. There are many of the Myxo- 

 phyceae which possess as much red or purple pigment as Porphyridium, and 

 moreover, the latter genus is generally found in association with blue-green 

 Algae. It is more nearly allied to Aphanocapsa than any other genus of 



