NOSTOCE. 241 
“The best distinctive mark of this species is the subacute extremities, 
combined with the short filament and littoral habitat. There are rarely 
more than one or two groups of enlarged cells, when only one is present 
it is situated near the centre of the filament. I believe that the attenuated 
extremities are constant, at least in the young plant, unless the filament 
has been broken.”—Rail/s. 
Plate XCIV. fig. 3. Portions of trichomes with heterocysts and 
spores X 400. 
Spherozyga Broomei. Thwaites in Harv. Phyc. Britt. 
Stratum bluish or yellowish green. Trichomes moniliform, 
joints subspherical. Heterocysts smooth, subquadrate, rather 
longer than wide. Spores numerous, elliptical, twice as long as 
wide, not much exceeding in width the joints, commencing tobe 
formed on either side next to the heterocysts. 
Size. Cells 004 mm. Heterocysts (005 x ‘006 mm. 
Spores 008 x ‘016 mm, 
“Thwaites in Harv. Phyc. Britt. t. 173, fig. A. Ralfs Ann. 
Nat. Hist. (1850) t. 8, fig. 10. 
On dead leaves of Myriophyllum in brackish ditch. 
“The gelatinous matrix is firmer than in many species of this genus. 
The numerous spores in each series distinguish it from every other species 
Iam acquainted with.”—Railfs, 
Plate XCIV. fig. 4. Portions of trichomes, with heterocysts and 
spores X 400. 
Species imperfectly known. 
Spherozyga Berkeleyana. Thwaites in Harv. Phyc. Britt. 
Young trichomes included, one or several together in a de- 
fined mucous sheath. Joints spherical, compressed. Hetero- 
cysts spheroidal, slightly compressed. Spores usually two on 
each side of the heterocysts, large, twice the width of the joints, 
oblong, half as long again as wide, becoming brown when 
mature. 
Sizz. Cells about :006--007 mm. Spores about -012 x 
015 mm. 
Thwaites in Harv. Phye. Britt. t. 173, fig. B. Ralfs Ann. 
Nat. Hist. 1850, 334, t. 8, fig. 11. 
Amongst Cladophora fracta, in brackish ditch. 
Mr. Ralfs says: “ The turgid spores and large compressed heterocysts 
characterise this species,” of which we have no knowledge. 
Plate XCVI. fig. 9. Portions of trichomes, with heterocysts and 
spores X about 400. After Harvey. 
