FRESHWATER ALG. 45 
litorea (Kiitz.) Born. et Flah. (figured by Bornet et Thuret, Notes algologiques, 
tab. xx1x.), the dimensions of which are, however, much greater. 
There is also some resemblance to N. harveyana (Thwaites) Thuret, but the 
filaments of the Antarctic form do not taper at the ends, and the cells are much 
flatter. 
66. NODULARIA QUADRATA sp. 0. 
(Pl. IL, figs. 109-115.) 
Filis in stratum laxum dispositis, seepe elongatis et modice flexuosis, interdum 
subrectis et parallelis, finibus vix attenuatis, cellula apicali rotundata vel plus minusve 
conica membrana sepe modice incrassata; vaginis tenuibus, hyalinis, plerumque 
distinctis ; cellulis deplanatis, longitudine 2—3plo latioribus, confertis, contentu late 
erugineo plus minusve granuloso ; trichomatibus modice torulosis; heterocystis 
singulis, raro binis, quadratis, plerumque tam longis quam latis vel interdum paulo 
longioribus, rare modice deplanatis, diametro cellulis vegetativis paulo  latioribus, 
membrana incrassata, contentu lete wrugineo homogeneo; sporis subglobosis, paulo 
longis quam latis, membrana levi, contentu granuloso, 
Diam. cell. veg. = 3-4; diam. vag. = 5-6; diam. heterocyst. = 5-6 p; 
diam. spor. = 7m; long. spor. = 8 p. 
Hab.—Freshwater pond in eskers upon ice, halfway between Black and Brown 
islands, January 3rd, 1903; pond in ice off Black island, McMurdo Strait, 
December 31st, 1902; growing in and through ice in pond among the eskers which 
border the shore of the Western Mainland, December 2nd, 1902. 
The most striking characteristic of this species are the square heterocysts, which 
are unusual in the genus (figs. 109-111). 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 are 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) Thuret, but it 
differs from it in the non-attenuation of the filaments, in the shape of the heterocysts 
and in the generally fatter cells. The heterocysts somewhat resemble those of 
N. tenuis G. 8. West (“ Rep. Freshw. Alg., incl. Phytoplankton, of the Third Tanganyika 
Expedition, 1904-5,” Journ. Linn. Soc., Bot., xxxvuir (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 NV. quadrata. 
