FRESHWATER ALG^l. 21 



cellularum contracto, cum pyrenoide magno globoso in utraque parte cellulse ; 

 chromatoplioram non vidi. 



Long. cell. = 35 p. ; lat. cell. = 16 /A. 



llal>. Isolated among sediment from freshwater ponds, Granite Harbour, 

 January 20th, 1902. 



The discovery of this Desmid is of great interest, as it indicates that the group 

 is not quite unrepresented, even in these extreme southern latitudes. It may well be 

 that the form just described is new, but the material was too scanty and the 

 cell-contents too badly preserved to warrant the establishment of a new species. The 

 cells appear elliptical in shape and have somewhat flat rounded ends. There is a 

 slight constriction in the middle of the cell, as in many species of the genus. The 

 specimens show considerable resemblance to P. cruciferum (De Bary) Wittr. (cf. 

 W. and G. S. West, A monograph of the British Desmidiaceae, Ray Society, 1904, 

 Vol. I., p. 100, PI. X., figs. 18, 19), but the shape of the cell is rather different. The 

 contents were contracted in all the individuals seen, and no details of the chloroplast 

 could be made out ; each half of the cell however has a large circular pyrenoid. In 

 many cases the contents showed a faint constriction similar to that of the cell- wall. 



CYANOPHYCE^E (MYXOPHYCE^E). 



CHROOCOCCACEjE. 



Genus CHROOCOCCUS Nageli. 



15. CHROOCOCCUS TURGIDUS. 



Chroococeus turgidus (Kutz.) Niig., Gatt. einzell. Alg. (1849), p. 46. 



Diam. cell. = 13-14/i. 



Hab.G&p pond, Winter Harbour, February 20th, 1904 (on Phormidium). 

 The sheath was plainly stratified, thus distinguishing this form from C. minutus, 

 which was much more abundant. 



16. CHROOCOCCUS MINUTUS. 



Chroococeus minutus (Kutz.) Niig., op. cit., p. 46 ; Rabenhorst, Fl. Europ. Alg., ii. (1865), p. 30. 



Diam. cell. = 8-1 1 p or sometimes even 13 p.. 



Hob. Abundant on the surface of Phormidium in some of the material from the 

 Gap pond, Winter Harbour. 



These specimens, like those recorded by Messrs. West (o/>. cit., p. 297) are larger 

 than the normal ; the cells were often grouped to form colonies of appreciable size. 



