WISCONSIN PHYTOPLANKTON 37 



var. SuBPUNCTULATUM (Nordstedt) B^rgesen. PL 57, Fig. 29. 



Medd. om Gronland 18: 12. 1894; W. & G. S. West, Monogr. Brit. Desm. 3: 

 209, pi. 84, figs. 15-20; pi. 85, figs. 1-3. 1908. 



Semicells with granules of central area conspicuously larger than 

 those near the margin, arrangement of granules at center generally 

 not following a definite pattern. (Tychoplanktont.) 



Cells 33 /A long ; 30 fi broad ; 10 /a broad at isthmus. 



George (rrr). 



W. & G. S. West recognize the forms Alpha and Beta of the variety, 

 the distinction being based upon smooth or granulate semicell apices. 

 The Wisconsin specimens belong to the variety Beta with granulate 

 apices. 



16. CosMARiUM OVALE Ralfs. PI. 58, Fig. 1. 



Ann. & Mag. of Nat. Hist. 14: 394 (p. p.), pi. 11, figs. 7D-7E. 1844; Brit. 

 Desm. 98, pi. 15, figs. 9A-9B. 1848; Carter, Ann. of Bot. 34: 282, pi. 13, figs. 

 82-88. 1920. 



Cells very large, length one and a half times to nearly twice the 

 breadth, outline oval, deeply constricted, sinus linear, with apical 

 portion somewhat inflated and outer margin widely open, isthmus 

 narrow; semicells truncate-pyramidate, with basal angles broadly 

 rounded and sides gradually converging to a truncate apex, apex 

 flattened to convex, cell outline with large conical granules with 

 rounded apices, cells frequently without granules at the poles. Ver- 

 tical view elliptic, with outline smooth except at poles. Lateral view of 

 semicells ovate, with granulation of cell outline confined to apical re- 

 gion. Cell wall with large granules similar to those of the cell outline 

 within the lateral margins but with apical area smooth, entire surface 

 of wall minutely punctate ; vertical view with a broad band of coarse 

 granules extending from pole to pole and lateral view of semicells 

 with the band extending from isthmus to apex. Semicells with four 

 parietal chloroplasts, two generally opposite each front face, each 

 chloroplast with numerous vertical laminate projections extending 

 to the cell wall ; main body of chloroplast with 6-12 pyrenoids. 



Zygospores unknown. 



Cells 180 fjL long ; maximum breadth 90 fi, breadth at apex 11 /x ; 

 breadth at isthmus 39 fi. 



Devils (rrr). 



COSMOCLADIUM De Brebisson 1856. 



Cells united by bands of gelatinous material to form spherical to 

 ellipsoidal, sessile or free-floating colonies. Colonies enclosed by 

 hyaline, homogeneous gelatinous envelopes. Cells small, quite similar 

 in shape to those of Cosmarium; length somewhat greater than the 

 breadth, median constriction usually deep and sinus linear ; semicells 

 usually compressed and front view elliptic. Vertical view elliptic and 

 lateral view of semicells subcircular. Cell wall smooth, without orna- 

 mentation aside from pores. Chloroplasts axial, with one pyrenoid. 



Zygospores spherical, with irregular, broad, angular projections. 



