FEESHWATER ALG^. 23 



In its habitat D. antarctica resembles D. mucicola F. Hustedt (Hedwigia, XLVIIL, 

 pp. 140-141), which also grows in the mucilage of a Nostoc, but Hustedt's species is a 

 much larger form with curved cells, having marked attenuated apices. The Antarctic 

 form is much nearer to D. montana W. and G. S. West ; the cells of this species are 

 however appreciably larger, are more pronouncedly spindle-shaped, and the species is 

 not endophytic. The cells in D. montana also appear to be more regularly arranged 

 than in D. antarctica {cf. G. S. West, Brit. Freshw. Algae (1904), p. 348, fig. 162a). 



A form like D. antarctica approaches very near to an Aplianothece. 



Genus Glceooapsa Kiitz. 

 21. Glceooapsa rupicola. 

 Glmocapsa rupicola Kiitz., Spec. Alg. (1849), p. 221 ; Eabenhorst, Fl. Europ. Alg., ii. (1865), p. 43. 



Diam. cell. = 4-5 /a ; diam. colon, usque ad 30 /x. 



Hah. — Gap pond, Winter Harbour, December 15th, 1903 (on surface of 

 Phormidium) ; freshwater pond, Granite Harbour, January 20th, 1902 (in sediment). 



The small colonies were spherical or elliptical. The inner sheaths were deep 

 red-brown, often almost completely obscuring the cells. A closely allied species 

 {G. shuttleworthiana Kiitz.) is recorded by Messrs. West {op. cit., p. 296). 



Genus Aphanothece Nageli. 

 22. Aphanothece prasina. 



Aphanothece prasina A. Braun in Rabenh. Alg. No. 1572 ; Eabenhorst, Fl. Europ. Alg., ji. (1865), 

 pp. 65-66. 



Hah. — Ice-wall, five feet above present level of river-like pond, " Penknife ice," 

 McMurdo Strait, September 13th, 1902. 



Small, but otherwise typical colonies, attached to Phormidium ylaciale. This 

 species is generally free-floating. 



Genus Microcystis Kiitzing. 

 23. Microcystis chroococcoidea. 

 (PI. II., figs. 102, 103.) 

 Microcystis chroococcoidea W. and G. S. "West, o}}. cit., p. 296, PL XXVI., figs. 107-114. 



Diam. cell. = 4/x.. 



Hah. — Gap pond. Winter Harbour, December 15th, 1903. 



Occasional colonies of this interesting form were found on the Phormidiu)n-&heets 

 from the above-mentioned locality. They agreed well with the description published 

 by Messrs. West, except that the cell-contents appeared homogeneous. 



VOL. VI. K 



