FRESHWATER ALG. 31 
39. PHORMIDIUM TENUE. 
Phormidium tenue (Menegh.) Gom., tom. cit., p. 169, Pl. IV., figs. 23-25. 
Diam. fil. = 1°5-2 p. 
Hab.—¥reshwater pond in ice off Black Island, MeMurdo Strait, December 31si, 
1902 (forming a thin stratum overgrown by Nodularia koettlitzi and species of 
Oscillatoria) ; Gap pond, Winter Harbour, December 15th, 1903. 
The cell-contents were occasionally shehtly granular. 
40. PHORMIDIUM FRAGILE. 
Phormidium fragile (Menegh.) Gom., tom. cit., pp. 163-164, Pl. LV., figs. 13-15. 
Diam, trichy— 1-51-82; lone. cell. = 1°5=2 px: 
Hab.—¥reshwater pond in eskers upon ice, half-way between Black and 
Brown Islands, January 3rd, 1903; Gap pond, Winter Harbour; growing in and 
through ice in pond among the eskers which border the shore of the Western mainland, 
December 2nd, 1902. 
41. PHORMIDIUM FRIGIDUM sp. nh. 
(PL. LL, fi 
g. 52.) 
Strato, ut videtur, tenui, membranaceo, colore? (ut videtur erugineo);  filis 
plerumque plus minusve tortuosis et intricatis, interdum parallelis ; vaginis mucosis, 
in muco hyalino diftluentibus ; trichomatibus inter cellulas distincte constrictis, seepe 
fere moniliformibus, apice non attenuato, cellula apicali rotundata ; cellulis tam longis 
quam latis vel ad duplo longioribus, cytoplasmate dilute ezrugineo, homogeneo, rare 
granulato ; dissepimentis plerumque cum granulo magno distincto seepe deplanato in 
utraque parte, interdum modo in altera parte, vel sine granulis ; calyptra nulla. 
Diam. trich. = 0°8-1°2 p (interdum ad 1°5 p). 
Hab.—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, which presumably grows on the surface of the ice, was only present 
in minute pieces, so that the general colour of the stratum cannot definitely be stated. 
It belongs to Gomont’s first section Moniliformia, but differs from all other species of 
that section in the frequent presence of granules at the dissepiments ; although 
occasionally wanting, the granules were always present on the majority of the septa in 
each filament. The granules were generally more or less flattened against the 
dissepiments, which gives the trichomes a rather characteristic aspect (¢/. the uppermost 
filament in fig. 52). 
Except for the shortness of the cells and the granulated dissepiments the species 
resembles P. angustissimum W. and G. S. West. It also comes close to P. /ragile 
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