SPOROCHNACE^E DESMARESTIA. 23 



SYNOPSIS OF THE BRITISH GENERA. 



Fam. 1. ARTHROCLADIE.E (J. Ag.). Spores attached to pen- 

 cilled filaments, issuing from the branches. 



I. DESMARESTIA. Frond solid, filiform or flat, distichously 



branched. [Plate 5, D.] 



II. ARTHROCLADIA. Frond traversed by a jointed tube, 



filiform, nodose. [Plate 5, C.] 



Fam. 2. SPOROCHNE^E. Spores produced in knob-like recep- 

 tacles, composed of whorled filaments, compacted to- 

 gether. 



III. SPOROCHNUS. Receptacles lateral, on short peduncles. 

 [Plate 5, A.] 



IV. CARPOMITRA. Receptacles terminal, at the tips of the 

 branches. [Plate 5, B.] 



FAMILY 1. ARTHROCLADIEJE. 

 I. DESMARESTIA. Lamour. [Plate 5, D.] 



Frond linear, either filiform, compressed or flat, disti- 

 chously branched, cellular, traversed by an internal, single- 

 tubed, jointed filament ; branches producing, when young, 

 marginal tufts of byssoid, branching fibres. Fructification 

 unknown. Name, in honour of A. G. Desmarest, a cele- 

 brated French naturalist. 



1. D. ligulata, Lightf. ; frond flat, with an obscure mid- 

 rib, repeatedly pinnate ; pinnae and pinnulse linear-lanceolate, 

 tapering at base, opposite. Grev. Alg. Brit. p. 36, t. 5 ; 

 Hook. Br. Fl. ii. p. 273 ; E. Bot. t. 1636 ; Wyatt, Alg. Danm. 

 No. 55. Harv. Phyc. Brit. t. cxv. 



On rocks and stones between tide-marks and at a greater depth. An- 

 nual. Summer. Frequent on the southern shores of England, and the 

 south and west of Ireland. Frith of Forth, Lightfoot. Orkneys, Rev. C. 

 Clouston. Yarmouth, Mr. Wigg. Frond 2 6 feet long, of a clear olive 

 brown while growing, but soon fading in the air to a verdigris-green ; yel- 

 lowish when dry. Branches variable in breadth, but all linear-lanceolate 

 in outline, and exactly opposite in insertion. 



2. D. aculeata, L. ; stem short, cylindrical, throwing forth 



