FRESHWATER ALC.K. 45 



i (Kiit/c.) Born, ct Fliili. (figured Ity Bornct ct Thurct, Notes algologiques, 

 tab. XXIX.), the dimensions of which arc, however, much greater. 



There is also some resemblance to A', linn-ri/unn (Thwaites) ThurH, hut the 

 filaments of the Antarctic form do not taper at the ends, and the cells arc much 

 flatter. 



6G. NODULARIA QUADRATA sp. 11. 



(PI. II., figs. 10'J-llo.) 



Filis in stratum laxum dispositis, .si-pr elongatis et modice flexuosis, interdum 



subrectis et parallelis, finibus vix attcnuatis, eellula apieali rotundata vel plus miuusve 

 ronica membrana ssepe modice incrassata; vaginis tenuibus, hyalinis, plcrumque 

 distinctis; cellulis deplanatis, lougitudiue 2-3plo latioribus, confertis, contentu Isete 

 aerugineo plus minusve granuloso ; trichomatibua modice torulosis ; heterocystis 

 singulis, raro binis, quadratis, plerumque tarn longis quani latis vel interdum paulo 

 loogioribus, rare modice deplanatis, diametro cellulis vegetativis paulo latioribus, 

 membrana incrassata, contentu hute icrugineo homogeneo ; sporis subglobosis, paulo 

 longis quam latis, membrana levi, contentu granuloso. 



Diam. cell. veg. = 3-4 p. ; diam. vag. = 5-G p. ; iliam. heterocyst. = 5-G p. ; 

 diam. spor. = 7 p. ; long. spor. = 8/1. 



Hub. Freshwater pond in eskers upon ice, halfway between Black and Brown 

 islands, January 3rd, 11)03 ; pond in ice off Black island, McMurdo Strait, 

 December 3fst, t902 ; growing in and through ice in pond among the eskers which 

 border the shore of the Western Mainland, December 2nd, l'J02. 



The most striking characteristic of this species are the square heterocysts, which 

 are unusual in the genus (figs. 109-1 1 1). As the figures show, the heterocyst is square 

 or even slightly longer than broad (figs. 109-110), even in filaments in which the 

 vegetative cells arc prominently flattened. The apices of the filaments are not 

 attenuated, but the apical cell is frequently long and more or less pointed, often 

 having an approximately conical shape (figs. 112-114). Unfortunately only one 

 case of spore-formation was seen, and I do not feel sure that this spore was mature ; 

 it was spherical with flat end-walls and had a thin membrane and granular contents 

 (fig. 115). 



The species probably stands nearest to N. harveyana (Thwaites) Thurct, but it 

 differs from it in the non-attenuation of the filaments, in the shape of the heterorvsts 

 and in the generally flatter cells. The heterocysts somewhat resemble those of 

 N. tennis G. S. West (" Rep. Freshw. Alg., iucl. Phytoplanktou, of the Third Tanganyika 

 Expedition, 1904-5," Journ. Linn. Soc., Bot,, xxxvni (1907), pp. 171-172), but this 

 species differs in its short trichomes, the attenuation of the ends of the latter, and the 

 square cells ; the dimensions are also less than in A r . guadrata. 



