24 F. E. FRITSCH. 



24. MlCROCYSTIS MARGINATA. 

 Microcystia marginata (Menegh.) Kiitz., Tab. Phyc., \. (1846), Tab. 8. 



Hah. Pond some distance behind hut, Cape Adare, January 9th, 1902 (free- 

 floating) ; attached to Prasiola calophylla, freshwater pond in gap, Winter Harbour, 

 January 12th, 1904. 



25. MlCROCYSTIS MERISMOPEDIOIDES. 



Microcystis merismopedioides F. E. Fritsch, Freshw. Alg. coll. iu the South Orkneys, etc., Journ. Linn. 

 Soc., Bot., xl. (1912), p. 332, text-fig. E. 



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

 McMurdo Strait, September 13th, 1902. 



The colonies were loosely attached to the surface of Pkormidium glacial', and 

 differed in no respect from those previously described. The general investment was of a 

 bright yellowish-red hue. 



26. MlCROCYSTIS PARASITICA. 



(PI. L, figs. 67-70.) 



Jllicrocys/is parasitiea Kiitz., Phyc. generalis, 1843, p. 170 ; Phyc. German., 1845, p. 148 ; Tab. Phyc., i. 



(1 840), Tab. IX. ; Migula, Kryptogainenfl. von Deutschland, Ucutech-Osterreich und d. Schwciz, ii., 1 



(1007), p. 36. 



Anacystis parasitiea Kiitz., Spec. Alg., 1849, p. 209. 



Microhaloajfirma Brcb. ; Kiitz., Tab. Phyc., i. (184(5), Tab. VII. ; Spec. Alg. (1849), p. 207. 

 Polycystis flrma (Breb. et Lenorm.) Rabenh., Fl. Europ. Alg., ii. (1865), p. 53. 

 Microcystisfirma (Breb. et Lenorm.) Migula, oj>. cit., p. 37. 



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

 McMurdo Strait, September 13th, 1902 ; freshwater pond in eskers upon ice, half-way 

 between Black and Brown Islands, January 3rd, 1903 ; Gap pond and other pools, 

 Winter Harbour. 



This form was very abundant on some of the P/iormidium-sheets from the 

 localities above-mentioned, and in several cases was found in large quantities on the 

 surface of aquatic micro-animals. The colonies varied very considerably in size 

 (15-40 /A) and were composed of numerous minute rounded cells, rarely exceeding 1 p 

 in diameter. The shape of the colonies was very diverse ; in many cases they were 

 more or less rounded and well defined (fig. 68), but in other cases the shape was quite 

 irregular (figs. 67, 70). These differences are not due to a difference in age, as large 

 colonies were often round and small ones quite irregular. The cells are, as a general 

 rule, very closely crowded, although in the more irregular colonies they tend to be less 

 densely placed at some points. The colour of the cell-contents varies from a pale blue- 

 green to a dark green. The colonies could in all cases be made to stand out 

 conspicuously against the background of the Phorrnidium by treatment with iodine, 

 which gave them a yellowish-brown tinge. 



