COSMARIUM. 165 



zygospores. It can be recognized from all these species by 

 the form of its cells alone. Its open sinus, rounded at the 

 apex, is characteristic, and the chloroplast is furnished with 

 a number of distinct lobes. 



24. Cosmarium bioculatum Breb. 

 (PI. LXI, figs. 3-7.) 



Heterocarpella bioculata Breb. Alg. Falaise, 1835, p. 56, t. 7 [in part only]. 

 Cosmarium bioculatum Breb. in Ralfs' Brit. Desm. 1848, p. 95, t. 15, f. 5 



In part ?] ; Arch, in Pritch. Inftis. 1861, p. 731 ; Eabenh. Flor. Europ. 



Alg. Ill, 1868, p. 163 ; Delp. Desm. subalp. 1877, p. 1, t. 7, f . 1-4 ; 



Kirchn. Alg. Schles. 1878, p. 147 ; Cooke, Brit. Desm. 1886, p. 89, t. 37, 



f . 6 ; Haiisg. Prodr. Algenfl. Bohui. 1888, p. 193 ; De Toni, Syll. Algar. 



1889, p. 933 ; West, Alg. N. Wales, 1890, p. 288 ; Alg. W. Ireland, 1892, 



p. 146 ; Alg. Eng. Lake Distr. 1892, p. 725 ; Roy & Biss. Scott. Desm. 



1894, p. 42 ; Xordst. Index Desm. 1896, p. 61 ; West & G-. S. West, Alg. 



S. England, 1897, Ip. 486 ; G. S. West, Alga-fl. Canibs. 1899, p. 115 ; 



West & G. S. West, Alga-fl. Yorks. 1900, p. 73 ; Alg. N. Ireland, 1902, 



p. 34; Scott. Freshw. Plankton, I, 1903, p. 526; Further Contrib. 



Freshw. Plankton Scott. Lochs, 1905, p. 484. 

 Didymidium (Cosmarium) bioculatum Reinsch. Algenfl. Frank. 1867, p. 107 



[in part]. 

 Cosmarium Phaseolus Breb. b. bioculatum Klebs, Desni. Ostpreuss. 1879, 



p. 35. 



Euastriim (Cosmarium) bioculatum Gay, Monogr. loc. Conj. 1884, p. 57. 

 Ursinella bioculata Kuntze, Revis. gen. plant. 1891, p. 924. 



Cells minute, about as long as broad, deeply con- 

 stricted, sinus narrow towards the apex and widening 

 outwards ; semicells transversely oblong-elliptic, both 

 base and apex flattened, sides rounded. Side view of 

 semicell subcircular. Vertical view oblong-elliptic, 

 ratio of axes about 1:2. Cell-wall smooth and colour- 

 less. Chloroplasts axile with one pyrenoid. 



Zygospore globose, furnished with conical, blunt 

 spines, from 9 to 11 of which show in the periphery. 



Length 15-21 M ; breadth 15-21 /LI ; breadth of 

 isthmus 4'8-6*7/i; thickness 6-9'5/u; diam. zygosp. 

 without spines 15-19 /u; with spines 22 ' 5-28 /i. 



ENGLAND. Westmoreland! (Ralfs). W., N., and 

 E. Yorks! Lancashire! (Ralfs). Leicestershire (Roy). 

 Cambridgeshire! Warwick (Wills). Gloucestershire 

 (Rolfs). Middlesex! Surrey (zygospores from Putten- 

 ham Common) ! Sussex (Ralfs). Kent (Ralfs). 

 Cornwall ! 



