NOSTOCE.E. 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." Ralfs. 



Plate XG1V. jig. 3. Portions of trichomes with heterocysts and 

 spores X 400. 



Sphaerozyga Broomei. Thwaites in Harv. Phyc. Britt. 



Stratum bluish or yellowish green. Trichomes moniliform, 

 joints subsphserical. Heterocysts smooth, subquadrate, rather 

 longer than wide. Spores numerous, elliptical, twice as long as 

 wide, not much exceeding in width the joints, commencing to be 

 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 

 I am acquainted with." Ralfs. 



Plate XC1V. fig. 4. Portions of trichomes, with heterocysts and 

 spores X 400. 



Species imperfectly 'known. 

 Sphaerozyga Berkeley ana. 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. 



SIZE. Cells about P 006-'007 mm. Spores about -012 x 

 015 mm. 



Thwaites in Harv. Phyc. Britt. t. 173, fig. B. Ralfs Ann. 

 Nat. Hist. 1850, 334, t. 8, fig. 11. 



Amongst Cladoplwra 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. 



