THE FRESH-WATER ALGAE 149 



104 (103, 105, 106) Cells single, spherical, or oval. Dictyosphaerium Nageli. 



Chromatophore single, parietal. Reproduction by internal division. 

 FIG. 160. Dictyosphaerium pulchellum Wood. X 5?o. (Original.) 



105 (103, 104, 106) Colonies much as in Dictyosphaerium except that the cells 



are in clusters of four which are held together by the rem- 

 nants of the mother-membrane Tetracoccus West. 



Some regard this as a young stage in Dictyosphaerium. 



106 (103, 104, 105) Cells clustered, grape-like, imbedded in the rather firm, 



often yellow gelatinous strands. . . Botryococcus Kutzing. 



West's genus Ineffigiata is probably a Botryococcus where the gelati- 

 nous envelop is somewhat contracted. 



In old cultures of Botryococcus, and often in nature, an orange 

 or reddish oil is produced which gives the cells that color. 



The alga is found very frequently in pools, ponds, and lakes; it 

 has been known to form the water bloom on lakes of small 

 dimensions. 



FIG. 161. Botryococcus braunii Kutzing. X about 300. (Original.) 



107 (96, 102) Cells not at the surface of a gelatinous mass but distributed 



through it 108 



108 (109) Colonies cylindrical, branching; gelatinous envelop somewhat 



rigid and often lamellate Palmodictyon Nageli. 



Cells in groups of two and four, the groups sur- 

 rounded by gelatinous vesicles which are united to 

 form the cylindrical colony, and give a more or less 

 netted appearance to the gelatinous portion. Repro- 

 duction by means of resting spores with brown walls; 

 these spores germinate and produce a new colony. 

 West states that the outer coat often becomes very 

 tough and of a brown color. Palmodictyon is a 

 very rare alga in America, but Collins reports it 

 from Massachusetts. 



FIG. 162. Palmodictyon viridis Kutzing. X 210. 

 (After West.) 



109 (108) Colonies of no definite shape, of the shape of the individual cells, or 



more or less angled and showing a dark gelatinous layer be- 

 tween the cells. Cells of ten isolated no 



no (127, 128) Colonies irregular in 



in (120) Cells not in clusters 112 



112 (115) Gelatinous envelop containing concentric lamellae about the 

 cells 113 



