Marine Algae, of Berwick-on-Tweed. 373 



Fronds red, slender, compressed or cylindrical, branches much 

 contracted at the base, often constricted at intervals into pseudo- 

 articulations, tetraspores tripartite in depressed cavities. Chylocladia. 

 Fronds purple or nearly black, small, constricted at intervals into 

 pseudo-articulations, tetraspores zouate immersed in the substance 

 of the frond. ... ... ... ••■ ■■• Catenella. 



59. Fronds formed of a single row of cells, (mouosiphonous) without 

 proper cortex. ... ... .. ... ... 60 



Fronds with distinct axial and cortical layers. ... ... 66 



60. Fronds mouosiphonous throughout. .. ... ... 61 



Fronds composed below of a single row of cells, becoming densely 

 cellular above, spores formed by the division of any of the cells, 

 filaments simple, gelatinous, dark purple. ... Bangia. 



Fronds composed of a single row of cells above, but below with a false 

 cortex formed by the growth of descending filaments, which proceed 

 either from the base of the branches or from the cells of the main 

 filaments. ... ... ... .. ... ... 65 



Frond formed of large cells placed end on end, with bands of smaller 

 cells at the nodes, in some cases the nodal cells exteuding in a thin 

 layer over the intern odal cells. ... ... .. Ceramium. 



61. Spores (as far as known) formed directly from the contents of any 

 of the cells. .. ... ... ... ... ... 62 



Spores on short pedicels, distinct, undivided. ... Chantransia. 



Spores cruciate on short, congested branches near the apices of the 

 erect filaments. Fronds composed of prostrate, creeping filaments 

 from which arise erect, dichotomous, or irregularly branched filaments. 



Rhodochnrton. 

 Tetraspores and cystocarps present. . . ... ... 63 



62. Filaments simple, forming a fine web over other alg;e. Erythrotriehia. 



Filaments dichotomously branching, minutely tufted. Goniotrichum. 



63. Fronds formed of prostrate filaments, from which arise erect pinnate 



filaments, cystocarps terminal, involucrate, spores irregularly grouped, 

 not surrounded by a common gelatinous envelope when mature. 



Spermothamnion. 

 Cystocarps terminal or lateral, spores irregularly grouped at maturity, 

 covered by a general gelatinous envelope. ... ... 64 



64. Fronds dichotomous, formed of delicate vesicular cells, tetraspores in 



whorls at the joints, involucrate. ... ... Griffithsia. 



Fronds dichotomous, or pinnate, branches alternate, tetraspores 

 tripartite,scattered on the branches, solitary or aggregated, cystocarps 

 lateral, usually binato. ... ... ... Callithamnion (in part). 



Branches opposite or whorled, tetraspores cruciate. Antithamnion. 



65. Fronds capillary or bushy, densely branching, cortications confined to 

 the larger branches, and evidently formed of vein-like descending 

 filaments. ... ... ... Callithamnion (in part). 



Fronds compressed, ancipital, branches pectinate-pinnate, covered 

 everywhere, except at the tips, by polygonal areolated cells. Ptilota. 



