28 WISCONSIN PHYTOPLANKTON 



Sheaths enclosing cells distinctly lamellated. 



Diameter of cell and sheath not exceeding 40 n C. TURGIDUS 



Diameter of cell and sheath over 60 n C. GIGANTEUS 



CHROOCOCCUS MINUTUS (Kiitzing) Nageli. PL 1, Fig. 1. 



Gatt. einz. Algen 46. 1849. 



Protococcus minutus Kiitzing, Tabulae Phycol. 1: pi. 5. 



Cells spherical or hemispherical, solitary or in colonies of 2-4 en- 

 closed by a wide, spherical, homogeneous, gelatinous sheath. Cell con- 

 tents pale blue-green to grey, homogeneous or granulose. ( Tychoplank- 

 tont). 



Diam. cells (without sheath) 5-7 p, (with sheath) 6-12 p.; length 

 (without sheath) 5-10 /A, (with sheath) 5-13 /i. 



Wolf (rrr).* 



CHROOCOCCUS DISPERSUS (v. Keissler) Lemmermann. PI. 1, Fig. 2. 



Arkiv. f. Botanik 2, No. 2: 102. 1904. 



Chroococcus minor var. dispersus v. Keissler, Verh. d. zool.-bot. Ges. Wien 

 52: 311, fig. 6. 1902. 



Cells spherical, 4-16 or more united to form spherical, ovoid, or ir- 

 regular colonies. Individual cells some distance from one another, 

 or in compact groups that lie some distance from one another within 

 the colony. Individual cell sheaths frequently confluent with the col- 

 onial sheath. Cell contents homogeneous, pale to bright blue-green. 

 (Euplanktont). 



Diam. cells (without sheath) 3-4 /JL- (with sheath) 6 p. Distance be- 

 tween cells or groups of cells 15-20 p.. 



Browns (rr), Pokegama (1) (rr). 



A species that is closely related to C. limneticus but one where the 

 number of cells in the colony is usually greater, and where the indi- 

 vidual cells or groups of cells are some distance from one another. 



var. minor var. nov. PI. 1, Fig. 3. 



Cells smaller than the typical form and with pale grey contents. 

 (Euplanktont). 

 Diarn. cells 1. 75-2. 5 /*. 



Long (3) (rrr), Middle McKenzie (rr), Palmer (rr). 



: The relative abundance of the individual species is shown by the following 

 symbols; (aaa) very abundant, (aa) abundant, (a) fairly abundant, (ccc) very 

 common, (cc) common, (c) fairly common, (s) fairly scarce, (ss) scarce, 

 (sss) very scarce, (r) fairly rare, (rr) rare, (rrr) very rare. 



