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 ptdchellum Wood. X S7o. (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 Kiitzing. 



vfnfi?(y>) West's genus InefigiaLa is probably a Botryococcus where the gelati- 



irs/-iC\n/^^YU 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. 



'j^yj^ Fig. 161. Botryococcus hraunii 'K.utzi'az. 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. 



f'^ST"''"*^' "-.-., Cells in groups of two and four, the groups sur- 



t-®©^;^^ ® ^r-*^ ©':^^', '-vr-v,^ rounded by gelatinous vesicles which are united to 



f® "'r® '%®i^'^''''^''^.'0"?®''W^^ form the cylindrical colony, and give a more or less 



\^'-^-'-'-"''.-^%^4^,.^-yQ\%.'^.i-!^\~^'<:<:^-} netted appearance to the gelatinous portion. Repro- 



""^"^ ^sij^C^®/--'-^^. : X* duction by means of resting spores with brown walls; 



.'^'^ <:^---^'^-^fi'^''ePu these spores germinate and produce a new colony. 



^tf''o'r'^::4'd.^'t^:^«-.w West states that the outer coat often becomes very 



^j5?',«:@;--^.r'^^''^^"^ tough and of a brown color. Palmodictyon is a 



-•■''*''&* S^-'^' ^^'y '^''^ ^'sa in America, but Collins reports it 



^••iisf^'iiSs. Js**'" from Massachusetts. 



ft^l-i'l'®.; ?:<>-''" Fig. 162. Palmodictyon viridis Kiitzing. 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 often isolated no 



no (127, 128) Colonies irregular in 



111 (120) Cells not in clusters 112 



112 (ns) Gelatinous envelop containing concentric lamellae about the 



cells 113 



