Fig. 264. CALLITHAMNION TETRAGONUM. 



Colour. A full or brownish-red, becoming darker in drying; but occasionally, when 

 young, brighter; turning orange in fresh water. 



Suhstance. Rigid; elastic. 



Character of Frond. ^ Thread-like {filamentous)-, jointed; single or tufted; much 

 branched; thicker than hogs' bristles below; becoming finer upwards. Set 

 with branches which spring in succession from all sides of the stem 

 {quadrifarious) ] the lowermost longest; several times re-branched in a similar 

 manner; the last set but one densely clothed with short, alternate, wide-spread 

 tufts of brauchletmzs. Branchlete^;^5 incurved; tapering at base; suddenly 

 pointed at top; springing from all sides. 



Joints. Obscure in the stems. Visible in all the branches. 



Measurement. From 3 to 6 inches long. 



Fructification. Of two kinds. 1. Minute spores in large, oval, single or double 

 capsules; borne on a (then) shortened branch^et^^7^. 2. Te^mspores excessively 

 minute; sessile near the tips of the same. 



Habitat. Our coasts generally. On the larger algse near low- water mark. Common. 



Fig. 265. CALLITHAMNION SPONGIOSUM. 



Colour. A dull reddish-brown; quite without gloss. 

 Suhstance. Soft and flabby; holding water like a sponge. 



Character ofi Frond. Thread-like {filamentous)-, jointed; single or tufted; much 

 branched. Stems shrubby; branches long; wavily curved; spreading in every 

 direction; thickly clothed (especially upwards), with one or more secondary, 

 similar sets. These furnished throughout with branchlets; the branchlets 

 crowded (especially upwards) with repeatedly forked {dichotomous) branchlet^ms, 

 which, springing from all sides, give each division a rounded, bushy character. 

 Angles of branching {axils) wide. 



Joints. Obscure in the main stems, which are more or less opaque and veiny. 

 Visible in all the branches. 



Measurement. From 2 to 4 inches long. 



Fructification. Of two kinds. 1. Minute spores in roundish or divided {loled) 



capsules; sessile on the stems of the branchlets, 2. Tetraspores, solitary; oval; 



sessile in the angles of branching {axils). 

 JIahitat. Our coasts generally, in the warmer stations. Isle of Man. Scilly Isles. 



West of Ireland, &c. On perpendicular rocks near low- water mark; and on 



other algje. Not uncommon. 



Not found in the same stations as G. arhuscula. 



40 



