FRESHWATER ALG^. 25 



It does not seem possible to distinguish adequately between Kiitzing's Microcystis 

 parasitica sindiYn.^ Microhaloa firma {= Microcystis firma). The colonies observed in 

 the present material really combine the characters of the two species. 



Var. GLACiALis var. nov. 



Cellulis minutissimis, dense aggregatis in familiis plerumque et saepe valde 

 irregularibus, in muco rubiginoso involutis ; contentum cellularum dilute serugineum 

 esse verisimile est. 



Diam. cell. = • 5 /x ; diam. colon, usque ad 40 ju. 



Hah. — Dull brick-coloured ice, situated in long level line as though in situation 

 of former water-level, four feet above frozen water-course through " Penknife " ice, 

 McMurdo Bay, September 13th, 1902. 



This form is partly, if not entirely, responsible for the colouration of the ice in this 

 habitat. The minute cells are densely aggregated in a brownish-red mucus, which 

 seems to be the only essential point of diiference from the type. As far as could be 

 made out the cells themselves have pale blue-green contents. 



Genus Merismopedia Meyen. 



27. Merismopedia tenuissima. 



(PI. L, figs. 49-51.) 



Merismopedia tenuissima Lemmermann, Beitr. z. Kenntn. d. Planktonalgen, Bot. Centralbl., Ixxvi. (1898), 

 p. 154. 



Diam. cell. ca. 1*5 /a. 



Hal). — Damp spot, summit of Cape Adare, January 9th, 1902. 



The colonies were composed of small, generally closely placed cells, and consisted 

 of sixteen or frequently thirty-two or even sixty-four cells, forming very regular 

 compact plates of small dimensions. The cell-contents were pale blue-green and 

 homogeneous. Wille (Antarkt. Algen, Nyt Mag. f. Naturvidenskab, xl. (1902), p. 219) 

 has recorded another form of this genus {M. glaucum (Bhrb.) Nag. var. j^unctatum 

 (Meyen) Hansg.) from Cape Adare, but the cells in the colonies of my material were 

 too minute to belong to this species ; they differed also in their frequently dense 

 aggregation. 



Genus Eucapsis Clements and Shantz. 



28. Eucapsis minuta sp. n. 



(PI. I., figs. 47, 48.) 



Familiis ssepe irregularibus, sed e fasciculis cubicis 8-32-128 vel plurium 

 cellularum compositis, libere natantibus, cum tegumento hyalino mucoso arcto ; cellulis 

 hemisphsericis vel subglobosis, geminatim dispositis ut in genere Chroococco, 

 cytoplasmate plerumque dilute serugineo (prsesertim in familiis novellis), sed interdum 



b: 2 



