FRESHWATER ALG. 37 
eranuloso; trichomatibus gradatim attenuatis, sed non in pilum  productis, non 
pseudo-ramosis, inter cellulas vix constrictis, dissepimentis distinctis; cellulis ad 
basin trichomatis tam longis quam latis vel modice deplanatis, sursum diametro ad 
duplo longioribus, contentu zrugineo granuloso. 
Diam. fil. ad bas. = 8-9»; diam. trich. ad bas. = 5-6; diam. trich. in media 
parte = 4-5»; diam. heterocyst. = 5-6 w ; crass. parietis vaginae = °8 p. 
fab.—Gap pond, Winter Harbour. 
The filaments are curved and intertwined to such an extent as to make it almost 
impossible to follow one from end to end (fig. 158). In places these densely 
entangled filaments form a thin stratum completely hiding the underlying Phormidium, 
but at other points they are much more loosely arranged. The base of the sheath is 
often a little inflated, and in this case there is a rapid narrowing of the filament just 
above the base ; beyond that point, however, the attenuation is very gradual, and the 
termination of the filament is only shehtly narrower than it is Just above the inflated 
base (figs. 159, 160). The terminal cell of the trichome appears to be more or less 
pointed and acute (figs. 159, 160). 
This species bears considerable resemblance to the Calothriv sp., described and 
figured by Messrs. West (op. cit., p. 298, Pl. XXV., figs. 55-57), which they regard as 
probably being a new species of the genus ; but there are some important differences— 
viz. the subtorulose cells (which are quite different to those of C. intricata), and the 
obtuse terminal cell of the trichomes. Possibly Messrs. West’s specimens are a variety 
of C. intricata. The genus Culothrix is, however, evidently well represented in the 
Antarctic with a considerable number of new forms. 
There is some resemblance between C. intricata and C. epiphytica W. and 
G. S. West, but, apart from the somewhat larger dimensions, the former differs in 
the fact that the trichomes do not taper into a hair and in the highly tortuous 
character of the filaments. 
56. CALOTHRIX GRACILIS, sp. 1. 
(Pl. III. figs. 164-172.) 
Filis rectis vel seepe modice flexuosis, solitariis vel subgregariis, usque ad 400 
longis, in superficie Phormidii repentibus, rare pseudo-ramosis ; vaginis tenuissimis, 
hyalinis, arctis, basin interdum inflatis ; heterocystis basilaribus, et in filis longioribus 
etiam intercalaribus, plerumque solitariis, in vaginis inclusis, deplanatis, hemispheericis 
vel rarius obconicis, membrana modice incrassata contentu homogeneo ; trichomatibus 
non in pilum productis, plerumque gradatim attenuatis, sed ubi basis vagine inflata est 
subito attenuatis paulum supra basim, cellula apicali acuta ; trichomatibus in parte 
basali inter cellulas modice constrictis; cellulis inferne sepe paulo deplanatis 
(preesertim ubi basis fili inflata est), in media parte et superne diametro circa 13plo 
longioribus, contentu cum paucis granulis; sporis (an maturis?) binis (semper ?), 
cylindricis, diametro 14—2plo longioribus, membrana levi. 
