WISCONSIN PHYTOPLANKTON 33 



These cells are somewhat smaller than other investigators find them 

 but the characteristic ornamentation shows that it is C. amoenum var. 

 mediolaeve. 



8. CosMARiuM BoTRYTis (Bory) Meneghini. PI. 57, Fig. 22. 



Linnaea 14: 220. 1840; Ealfs, Brit. Desm. 99, pi, 16, figs. lA-lD. 1848; 

 Carter, Ann. of Bot. 34: 277. 1920. 



Cells of medium size, length about a quarter greater than the 

 breadth, deeply constricted, sinus linear, with apex slightly inflated 

 and outer margin open, isthmus narrow; semicells truncate- 

 pyramidate, with basal angles broadly rounded and apical angles 

 more acute ; semicell apices distinctly flattened. Vertical view elliptic 

 and with sides inflated in median portion. Lateral view of semicells 

 broadly elliptic. Cell wall coarsely granulate, with granules dis- 

 tributed over the entire wall but not forming a definite pattern. 

 Semicells containing two chloroplasts, each with a central pyrenoid, 

 the axis of each chloroplast giving rise to 4-6 plates that radiate 

 towards the periphery and have their peripheral edges flattened 

 against the cell wall. (Tychoplanktont.) 



Zygospores spherical, with numerous short radiating processes that 

 have conical bases and trispinate apices (Ralfs.) 



Cells 60-108 fi long ; 52-74 /x broad ; breadth of isthmus 14-26 [i. 



Zygospores 51 /a in diameter, with spines 9.7 jn long (Ralfs). 



Beaverdam (rrr). Crab (rrr), Grindstone (rrr). Horseshoe (rr), Muskallonge 

 (rrr). Number One (rrr), Sand (rrr), Whitney (rrr). 



9. CosMARiUM RENiFORME (Ralfs) Archcr. PI. 57, Fig. 23. 



Jour, of Bot. 12: 92. 1874; W. & G. S. West, Monogr. Brit. Desm. 3: 157, 

 pi. 79, figs. 1-2; pi. 82, fig. 15. 1908. 



Cosmarium margaritiferum var. reniformis Kalfs, Brit. Desm. 100, pi. 16, 

 fig. 2A. 1848. 



Cells of medium size, length and breadth about equal, deeply con- 

 stricted, sinus narrow, with apex greatly inflated and pyriform, outer 

 portion dilated, isthmus narrow and somewhat elongate; semicells 

 reniform, with outline coarsely granulate. Vertical view elliptic. 

 Lateral view of semicells circular. Cell wall with coarse granules 

 covering the entire surface and arranged in a criss-cross series. 

 Chloroplasts axial and with two pyrenoids. (Tychoplanktont.) 



Zygospores spherical and with smooth walls (W. & G. S. West). 



Cells 54 n long; 50 fi broad; 16.5 ix broad at isthmus. 



Diameter of zygospores 54-60 fi (W. & G. S. West). 



Eagle (rrr). 



10. Cosmarium Portianum Archer. PL 57, Fig. 24. 



Quart. Jour. Micr. Sci. 8: 235, pi. 11, figs. 8-9. 1860. 



Cosmarium orhiculatum De Bary non Ralfs, Unters. u. d. Fam. d. Conj. 41, 

 pi. 6, figa. 49-50. 1858. 



