24 DESMARESTIA — ARTHROCLADIA. 



numerous slender, flattish branches, which are repeatedly 

 irregularly pinnate ; pinnaj and pinnulce alternate, tapering 

 at base, filiform, either fringed with minute tufts of delicate 

 fibres, or set with erect, awl-shapcd, alternate, distichous 

 spines. Grev. Alg. Brit. p. 38, t. 5, /. 2, 3 ; Hook. Br. FL 

 n.p. 273; E. Bot. t. 2445; Wyatt, Alg. Damn. No. 158, 

 a. and |S. ; Harv. Pliyc. Brit. t. xlix. 



Ou rocks, stones and Alfjte between tide-mailvS, and in 4 — 5 fathom 

 water. Perennial. Common on most shores. — Fronds \ — 3 feet long. 

 In the young plant the branches are soft and flaccid, and furnished along 

 their wlaole length with tufts of bright green couferva-like filaments, which 

 drop off" as soon as the branch has completed its growth. Old plants are 

 rigid, destitute of these fibres, and the branches set with short awl-shaped 

 spines or ramuli ; but whenever they shoot out new branches, these are 

 constantly clothed with the green fibres, which seem to be an indispensable 

 accompaniment to the process of growth, and perhaps perform the func- 

 tions of leaves. No fructification has yet been observed either in this spe- 

 cies or in D. ligulata. 



3. D. viridis, Miill. ; frond cylindrical, filiform, repeatedly 

 pinnate; pinnae and pinnulae capillary, opposite. Dicldoria 

 viridis, Grev. Alg. Brit. p. 39, t. 6 ; Hook. Br. FL ii. p. 274; 

 F. Bot. t. 1669; IVgait, Alg. Damn. No. 56. 



In the sea, growing on stones and the larger Algae between tide-marks. 

 Annual. Summer. Not uncommon on the British shores. — Root disk-like. 

 Frond 2 — 3 feet long, excessively branched in a pinnated manner, all the 

 branches and ramuli exactly opposite; the main stem about half a line in 

 diameter at base, gradually attenuated upwards ; the branches becoming iu 

 each series more and more slender and capillary ; the whole plant having 

 a strikingly feathery and delicate appearance. Colour., whilst growing, 

 dark olive or "foxy" (Dr. Drummond) \ quickly becoming a verdigris- 

 green when removed from the water. Substance at first harsh and rigid, 

 but soon becoming flaccid on exposure, in which stale it closely adheres to 

 paper. 



II. Arthrocladia. Duby. [Plate 5, C] 



Frond filiform, cellular, with an articulated, tubular axis, 

 nodose ; the nodes producing whorls of delicate, jointed fila- 

 ments. Fructification : pedicellate, moniliform pods, borne 

 on the filaments, and containing, at maturity, a string of 

 elliptic spores. Name, a^d^ov, a joint, and «Aa5b$, a branch. 



1. A. villosa, Huds. ; Harv. Phyc. Brit. t. Ixiv. Sporoch- 



nus villosus, Grev. Alg. Brit. p. 42 ; Hook. Br. FL ii. p. 274; 



F. Bot. t. 546; JVyatt, Alg. Damn. No. 105. 



On submarine substances, in 4—5 fathom water, rather rare. Annual. 

 Summer and autumn. Coast of England in several places, chiefly in the 



