Plate LXXVII. 
Fig. 361. CALOTHRIX LUTEOLA. 
Colour. Light green ; or (when the colour-cells have dropped out) pale horn-colour. 
Substance. Very soft. 
Character of Frond. Exceedingly slender threads (^filaments) scattered along the stems of the 
lesser alg^5 forming a downy fringe. Filaments unbranched ; tubular ; some containing 
very narrow, close-set, cylindrical colour-cells, which show through ; their division-lines 
faintly marked ; some partially or entirely empty from these having dropped out. 
Measw-'ement. One-tenth, or at most ^ of an inch high ! 
Fructification. Minute seeds {zoospores) formed of the colour-cells in the filaments ; which 
cells then separate from each other and drop out. 
Habitat. Appin ; but should be looked for elsewhere. On thread-shaped {filiform) algce in 
tide-pools. 
The word Calothrix is misspelt on this Plate. 
Fig. 362. CALOTHRIX FASCICULATA. 
Colour. Very dark, shining green. 
Substance. Velvety ; very slippery to walk upon. 
Character of Frond. Minute tufts of very straight, upright, finely-pointed threads {filaments) ; 
forming a spreading velvety layer upon rocks. Filaments not branched ; but some- 
times surrounded at top with a set of lesser ones lying close against them, branch- 
like ; tubular ; containing very narrow, close-set, cylindrical colour-cells, which show 
through ; their division-lines strongly marked. 
Measurement. Filaments J or J of an inch high ; the velvety layer indefinite. 
Fructification. As in the preceding. 
Habitat. Miltown Malbay, and probably elsewhere. Spreading over the surface of rocks about 
half-tide level. 
Possibly only C. scopulorum, grown in deeper water. It is taller, straighter, darker, and 
occasionally appears branched above, as described. 
Fig. 363. CALOTHRIX SCOPULORUM. 
Colour. A dull, dirty green. 
Substance. Velvety ; very slippery to walk upon. 
Character of Frond. Exceedingly minute, upright, wavy threads {filaments) ; often finely 
tapering ; rising from a slimy base ; forming a spreading, velvety layer upon rocks. 
Filaments unbranched; tubular; containing very narrow, close -set, cylindrical 
colour-cells, which show through ; their division-lines indistinctly marked. 
Measurement. One-fifth of an inch high. 
Fructification. As before. 
Habitat. Our coasts generally. On rocks near high-water mark. Common. 
153 
X 
