Fig. 264. CALLITHAMNION TETRAGONUM. 
Colour. A full or brownish-red, becoming darker in drying ; but occasionally, when young, 
brighter ; turning orange in fresh water. 
Substance. 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 branchleteews. Branchleteews incurved ; 
tapering at base ; suddenly pointed at top ; springing from all sides. 
Jomts. 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 branchleteew. 2. Tetraspores excessively minute ; sessile 
near the tips of the same. 
Habitat. Our coasts generally. On the larger alg?e near low-water mark. Common. 
Fig. 265. CALLITHAMNION SPONGIOSUM. 
Colour. A dull reddish-brown ; quite without gloss. 
Substance. Soft and flabby ; holding water like a sponge. 
Character of 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 fur- 
nished throughout with branchlets ; the branchlets crowded (especially upwards) with 
repeatedly forked {dichotomous) branchleteews, 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 {lobed) capsules; 
sessile on the stems of the branchlets. 2. Tetraspores^ solitary ; oval ; sessile in the 
angles of branching {axils). 
Habitat. 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 alg£e. Not 
uncommon. 
Not found in the same stations as C. arhuscula. 
114 
