PROTOCOCCUS. 181 



As a matter of historical interest we record a few of the more 

 prominent forms with the names, partly as varieties, which 

 obtained hitherto. 



I. Aerial Forms. 



PROTOCOCCUS VIRIDIS, Ag. 



Cells small, segregate, accumulated in broadly expanded 

 strata of yellowish or darker green color, usually pulver- 

 ulent, but during moist weather and after rain somewhat 

 gelatinous. 



Diameter of cells, 3-13 yw. 



Common everywhere, on trunks of trees, moist rocks, 

 walls, timbers of shaded buildings, old fences, etc. 



Syn. Pleurococcus vulgaris, Menegh. ; Protococcus communis, Kg. ; 

 Clilorococcum vulgare, Grev., etc. 



Plate CLXI, fig. 1, a simple cluster of cells evenly dis- 

 tributed. 



Plate CLXII, fig. 2, the same, but often clustered by 

 twos, fours, and more, the result of division in one or two 

 directions ; the Pleurococcus form. 



Plate CLXIII, figs. 1-5, show modes of development into 

 filaments of Ulothrix. 



b. Var. ANGULOSA. Pleurococcus angulosus, Menegh. 



The same as the last, but in different condition; in the 

 process of decay rather than of multiplication ; effected by 

 alternate moisture and dryness; the cells sometimes form 

 around themselves gelatinous envelopes; they divide dis- 

 tinctly ; becoming angular by crowding. 

 Plate CLXII, fig. 3, cells very gelatinous. 



c. Var. DISSECTUS. Pleurococcus dissectus, Naeg. 



Another condition of the same, being a dark green vege- 

 tative, developing form, with cells decussately dividing; 

 membranes thin. 



Diameter of cells, 5-11 ^. 



Usually on old and moist wood. 



Plate CLXII, fig, 4. Plate C, fig. 5, cells commencing to 

 develop. 



d. Var. MINIATUS. Pleurococcus miniatus, (Kg.) Naeg. 



Cells often of an orange yellow, or reddish brown color, 



