40 F. H.. FRITSCH. 
59, Nosroc LONGSTAFFI,* sp. n. 
(Pl. IIL, figs. 132-137.) 
Ss) 
Thallo lete srugineo, impellucido, primo adnato, demum libere natante, forma 
disci tenuis ovalis vel circularis cum margine modice irregulari, non confluentis, 
diametro usque ad 12 mm.; trichomatibus dense intricatis, valde tortuosis, seepe cum 
vaginis distinctis amplis hyalinis margine incrassata et inter cellulas constrictis ; 
cellulis parvis, plerumque globosis vel interdum ellipsoideis (deplanatis doliformibus 
post divisionem), plerumque remotis, contentu homogeneo lete zrugineo ; heterocystis 
plus minusve globosis, solitariis, diametro trichomatis circiter duplo latioribus, mem- 
brana incrassata et contentu homogeneo; sporis globosis, membrana levi, confertis, 
in catenis longis dispositis ; thallus peridermate tenui, paulo lamellato, et firmo (multo 
firmiore quam in NV. disc/form/) circumdatus est ; thall juvenales elongati sunt. 
Diam. cell. veg. = 3-4; diam. heterocyst. = 5-6; diam. spor. = 5p; diam. 
vagines = 10-12 p. 
Hab.—Gap pond, Winter Harbour; freshwater pond in ice off Black Island, 
McMurdo Strait, December 31st, 1902 ; dry ponds, Winter Quarters, February, 1902. 
This species has a great superficial resemblance to NV. diseiforme (cf. fig. 132), but 
there are important differences. The filaments are much more densely intertwined 
than in that species (fig. 187), and as a result the whole thallus acquires a coarser, 
opaque appearance, very different from that of the delicate transparent thalli of 
N. disciforme (ef. figs. 137 and 131, which show the thalli of the two species, magnified 
to the same extent). The envelope of the whole colony is also much coarser and firmer 
than the gelatinous investment of V. disciforme. These differences are sufficient to 
enable one to distinguish between the thalli of the two species with the naked eye. 
The trichomes are very similar in the two species, but in VV. longstafi a wide 
mucilage-sheath is commonly found enveloping the individual trichomes (fig. 136). 
This sheath is far more distinct than that occasionally found in N. diseiforme ; it 
has a thickened outer edge and is often obviously constricted between the cells. The 
spores are absolutely spherical (fig. 135) and often form long chains, which were 
abundant on the surface of the Phormidiwm-sheets in several of the samples, being 
quite free from the colonies. 
The young colonies appear to be quite different from those of V. diseiforme. 
Those which I have seen were elongated (figs. 133, 134) with a heterocyst at one or 
both ends and the contained trichome was already closely wound. I have not been 
able to follow their further development. 
The two species of .Vostoe above described obviously belong to Bornet and Flahault's 
section Cuticularia (see Ann. Sci, nat., Bot., 7 sér., VIL. (1888), p. 183). WV. disciforme 
comes nearest to N. maculiforme Bornet et Flahault, but it differs from it in the 
* Named after Mr. Longstaff, whose generous contribution rendered the expedition possible. 
