24 ¥. EK. FRITSCH. 
24. MIcROCYSTIS MARGINATA. 
Microcystis marginata (Menegh.) Wiitz., Tab. Phyc., i. (1846), Tab. 8. 
/ab.—Pond some distance behind hut, Cape Adare, January 9th, 1902 (free- 
floating) ; attached to Prasiola ealophylla, freshwater pond in gap, Winter Harbour, 
January 12th, 1904. 
25. MICROCYSTIS MERISMOPEDIOIDES. 
Microcystis merismopedioides V'. BK. Fritsch, Freshw. Ale. coll. in the South Orkneys, etc., Journ. Linn. 
Soc., Bot., xl. (1912), p. 332, text-fig. 2. 
Hab.—Ice-wall, five feet above present level of river-like pond, “ Penknife ice,” 
MeMurdo Strait, September 13th, 1902. 
The colonies were loosely attached to the surface of Phormidium glaciale, and 
differed in no respect from those previously described. The general investment was of a 
bright yellowish-red hue. 
26. MICROCYSTIS PARASITICA. 
(Pl. L, figs. 67-70.) 
Microcystis parasitica Wiitz., Phye. generalis, 1843, p. 170; Phye. German., 1845, p. 148; Tab. Phyc., i. 
(1846), Tab. IX. ; Migula, Kryptogamenfl. von Deutschland, Deutsch-Osterreich und d. Schweiz, ii., 1 
(1907), p. 36. 
Anacystis parasitica Kiitz., Spec. Alg., 1849, p. 209. 
Microhaloa firma Breb. ; Kiitz., Tab. Phye., i. (1846), Tab. VIL. ; Spec. Alg. (1849), p. 207. 
Polycystis firma (Bréb. et Lenorm.) Rabenh., Fl. Europ. Alg., ii. (1865), p. 53. 
Microcystis firma (Bréb. et Lenorm.) Migula, oy. cit., p. 37. 
Ilab.-—\ce-wall, five feet above present level of river-like pond, ‘‘ Penknife ice,” 
MeMurdo 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 Phormidium-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 yw) and were composed of numerous minute rounded cells, rarely exceeding 1 pu 
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 
irrecular (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 Phormidium by treatment with iodine, 
which gave them a yellowish-brown tinge. 
