68 ALG^E. 



pearance ; while the striated appearance is caused by 

 the dark cells being elongate and the cell-walls thick, 

 so as to form white interspaces. 



The fructification consists of capsules (ceramidia), 

 attached to the sides of the branches, containing pear- 

 shaped spores, with tetraspores imbedded in swollen 

 branches of separate plants. 



Polysiphonia fastigidta (fig. 25, a small piece) is 

 common, attached to the fronds of Fucus. Its fila- 

 ments are rigid, bristle-like, of the same breadth 

 throughout, forked, and forming globular brown or yel- 

 lowish tufts, from 2 to 4 inches long. The joints are 

 broader than long, each with 16-18 of the dark cells. 

 In the centre of the branches of this sea- weed is a 

 row of curious objects (fig. 26 ), consisting of a dark- 

 coloured body surrounded with irregular spiny mar- 

 ginal processes, and with a colourless short process 

 above and below. These require further investiga- 

 tion. 



P. nigredcens is also common among masses of sea- 

 weeds. Its filaments are brown, pinnate, the branches 

 awl-shaped, and the joints about as long as broad. 



Ddsya coccin'ea (PL IV. figs. 1 and 2, representing 

 small portions of a filament) is a very common fila- 

 mentous red sea-weed of the same family. The fila- 

 ments are 6-8 inches long, and bipinnate, the larger 

 ones somewhat resembling those of Polysiphonia, in 

 being composed of parallel longitudinal cells, arranged 

 round the centre, but containing also smaller inter- 

 mediate cells ; while the smallest branches (fig. 2), 

 which arise in tufts, consist of a single row of cells, 

 little longer than broad. The fruit consists of ovate 

 capsules (ceramidia), placed at the base of the branches, 

 and containing a round mass of spores. There is also 

 another kind of fructification, occurring on distinct 

 plants ; this is formed of one or two rows of tetra- 

 spores, immersed in pod-like capsules, called stichid'ia 

 (cr/%09, row). 



