(34) 



minute alternate spine-like teeth. Substance cellular, of three strata of 

 cells, surrounding a slender jointed axial tube, that nest the tube of 

 few minute closely-packed oblong cellules, second of much larger oblong 

 somewhat curved cells ; the periphery of minute roundish cellules, very 

 closely -packed, and having a tendency to arrange themselves into 

 vertical filaments. Substance cartilaginous, very hard and rigid when 

 old. Colour, when young, a fine olive green ; when old, olive brown ; 

 when dry, blackish brown. 



This beautiful species when about a foot in length (in the first or 

 second week of May) is simply pinnate, everywhere fringed with delicate 

 filaments of a pale green coloiu', and about a line and a-half in length, 

 forming little pencil-like tufts along the margin of the frond ; so delicate 

 are these, that when the plant is taken out of the water they lie flat 

 on the branches, and are not distinguishable from the main branches, 

 and the whole looks like a rather stout slightly-branched Gladophora. 

 As the plant advances in its growth, it becomes more branched, the 

 branches more elongated without altering their width, the byssoid 

 filaments gradually disappear, even at length from the summits, the 

 whole becomes fringed with alternate minute spine-like teeth, and 

 the plant has thus the appearance of harsh, rigid, somewhat flattened 

 threads. In this state it is frequently thrown on shore in autumn 

 in large bundles, often five to six feet in length. 



The young fronds are rarely if ever seen on the beach, and are only 

 got by dredging in deep watei*, or occasionally in deep sheltered pools 

 near low-water mark. 



EXPLANATION OF PLATE CXLIIL 



Fig. 1. — Desmarestia aculeata, natural size. 

 2. — Branchlet (old). 



3. — Pinna from a byssoid filament of a young plant. 

 4. — Transverse section of a branch. 

 5. — Longitudinal section of same. All maguified. 



