31. Colonies shaped difPerently from above 32 



32. Fragments of old mother cell walls lying scattered about and 

 partly inclosing spherical daughter cells; colonial mass soft and 

 shapeless, usually floating at the surface Schizochlamys 



32. Fragments of old mother cell walls lacking or, if present, not 

 scattered among daughter cells; colonial mass of definite shape 33 



33. Colonies irregularly globose or spherical; cells arranged in groups 

 of 4, tlie clusters remote from one another within copious muci- 

 lage; cells bearing long pseudociUa (visible only under favor- 

 able optical conditions) Tetraspora (in part) 



33. Colonies of various shapes; cells not arranged in groups of 4, 



and witliout pseudocilia _ 34 



34. Cells ovoid, compactly arranged in semi-opaque mucilage, form- 

 ing dense, simple or compound masses, adhering to one another 

 by branching strands of mucilage (PI. 52, Figs. 1, 2); individual 

 cells often not apparent in older colonies because of dark muci- 

 lage and density of cell contents Botryococcus (in part) 



34. Cells not arranged in semi-opaque, irregularly shaped colonies —35 



35. Chloroplast a stellate mass with radiating processes Asterococcus (in part) 



35. Chloroplast not stellate 36 



36. Cells arranged in groups of 4 at the ends of branching strands 

 formed by the remains of old mother cell walls; colony ovoid 



or globose 37 



36. Cells not arranged at the ends of branching strands; colony of 

 various shapes 38 



37. Cells reniform to sausage-shaped and some also appearing ellip- 

 soid in each group of 4, at the ends of branching strands (gela- 

 tinous investment usually lacking) ....Dimorphococcus (in part) 



37. Cells spherical or broadly ovoid, all the same shape, in groups of 



4 at the ends of branching strands Dictyosphaerium 



38. Cells spherical 39 



38. Cells of various shapes, fusiform, ovoid, reniform 42 



39. Cells arranged in linear series ( single or double ) within branched 

 gelatinous strands; either with or without individual lamellate 

 sheaths — Palmodictyon (in part) 



39. Cells arranged otherwise — - 40 



40. Colonies spherical or irregularly shaped, sometimes triangular, 

 with cell sheaths distinct and not confluent with the colonial 

 mucilage . -^ - - - - G/oeocj/sfts ( in part ) 



40. Colonies spherical; cells without individual sheaths, or with 

 sheaths confluent with the colonial mucilage and not apparent 41 



41. Cells with cup-shaped chloroplasts containing a conspicuous 

 pyrenoid; colony usually showing daughter colonies of smaller 



cells resulting from cell division Sphaerocystis 



41. Cells with several peripheral, polygonal chloroplasts, each with a 

 pyrenoid (when cells are young with but 1 cup-shaped chloro- 

 plast; in this condition to be compared with Sphaerocystis); 

 colonies never containing daughter colonies, but frequently dis- 

 integrating so that cells become solitary Planktosphaeria (in part) 



42. Cells lunate or sickle-shaped, with narrow poles - -43 



42. Cells reniform or fusiform, with rounded apices 44 



[574] 



