SPERMOSEIKA. 233 



most distant from the ciliated connecting one." Thw. Harv. 

 Phyc. Brit. f. cxiii. B. 



On the muddy sides of ditches of brackish water, also floaling;. Dolgelly, 

 Mr. Ralfs. Shirehampton, Mr. Tkwaitcs. Povthury, Somerset, Mr. 

 Broome. — " Very gelatinous, deep green, sometimes almost black. Fila- 

 ■nwnts pale green, curved, entangled ; connecting-cells large, ciliated, sub- 

 spherical, slightly oblong, of a lighter colour than the ordinary cells, which 

 are somewhat compressed. Spores of a deep brown when mature." Thw. 



3. S. Broomei, Thw. ; " spores numerous, elliptical, twice 

 as long as wide, not much exceeding in width the ordinary 

 cells, commencing to be formed from the cells nearest the 

 connecting- cells ; connecting-cells smooth, rather longer 

 than wide." Thw. Harv. Phyc. Brit. t. clxxiii. A. 



Ditches at Shirehampton, Mr. C. E. Broome and Mr. Thivaitcs.—'''- A 

 very distinct species, first detected by C. E. Broome, Esq., an excellent 

 cryptogamic botanist, after whom it is named.'' Thto. 



4. S. Berkeleyana, Thw. ; spores large, twice the width of 

 the ordinary cells, oblong, half as long again as wide, becom- 

 ing brown when mature, generally two on each side the con- 

 necting-cell, which is spherical, slightly compressed ; young 

 filaments included, one or several together, in a defined, mu- 

 cous sheath." Tlnv. Harv. Phyc. Brit. t. clxxiii. B. 



Ditches at Shirehampton, Mr. Tlmmites . — " This fine species, which is 

 named in honour of the Rev. M. J. Berkeley, is interesting from the cir- 

 cumstance of its filaments, when young, being enclosed, often several 

 together, in definite, gelatinous sheaths, out of which they appear to es- 

 cape before the spores are mature. There are other species, occurring in 

 fresh-water, which exhibit the same peculiarity of structure, but it does not 

 seem to have hitherto been noticed." 



5. S. Ralf'sii, Thw. MS. ; filaments straight or nearly so ; 

 ordinary ceils sub-quadrate; spores cylindrical with tnm- 

 cated ends, of very unequal length, and scattered irregularly 

 throughout the filament ; connecting-cells oblong. 



Tn brackish and in fresh-water ditches near Bristol, G. H. K. Thwaites. 

 For the reception of this and some other closely allied species it is proposed 

 to constitute a new genus [Dolichospermum), characterized by their spores 

 being of unequal length and scattered irregularly throughout the fila- 

 ment. 



III. Spekmoseira. Ag. [Plate 27, E.] 



"■Filaments slightly mucous, free, simple, cylindrical, en- 

 closed in a very delicate, membranous tube. Celh lenticu- 

 lar ; connecting-cells larger, compressed." Tltw. Spores 



K 



