DICTYOTA STILOPHORA. 39 



Rocks between tide-marks, rare. Annual. Summer. East and south of 

 England. Frith of Forth, Grev. Ballycotton, coast of Cork, Miss Ball. 

 Fronds tufted, 3 12 inches long, with a broadly wedge-shaped or palmate 

 outline, triangular at base, deeply cleft into numerous segments, which are 

 again divided into lesser ones, the apices truncate. The colour is a brownish- 

 olive ; the substance thin and transparent, and the whole surface beautifully 

 marked with broad wavy lines of dark brown spores, from a quarter to half an 

 inch asunder, the intermediate spaces mottled with scattered groups of spores. 



VI. DICTYOTA. Lamour. [Plate 7, A.] 



Root coated with woolly fibres. Frond flat, ribless, mem- 

 branaceous, reticulate, dichotomous or pinnatifid ; the surface 

 cells parallel, those at the apices of the segments converging. 

 Fructification : roundish, scattered sori, bursting through 

 the cuticle on both surfaces of the frond, consisting, at matu- 

 rity, of numerous, obovate, tufted spores; or, on distinct 

 plants, solitary, scattered spores. Name, SMTVOV, a net, be- 

 cause the surface is reticulated. 



1. D. dichotoma, Huds. ; frond regularly dichotomous, 

 linear ; the segments becoming gradually narrower towards 

 the extremities ; spores scattered irregularly or clustered. 

 Grev. Alg. Brit. p. 57, /. 10; Hook. Br. FL ii. p. 280; 

 Wyatt, Alg. Danm. No. 10 ; E. Bot. t. 774 ; Harv. Phyc. 

 Brit, t. ciii. 8. intricata, Grev. ; frond very narrow, much 

 branched, twisted and entangled. 



On rocks and sea plants in the sea, between tide-marks, and in 4 15 

 fathom water. Both varieties common. Annual. Summer. Fronds 

 3 12 inches long, 1 4 lines wide, of a clear olive-green colour and mem- 

 branous substance, regularly dichotomous. Spores either scattered over 

 the surfaces, or (in distinct plants) collected into dense spots. 



VII. STILOPHORA. J. Ag. [Plate 7, C.] 



Root a small, naked disk. Frond filiform, solid or tubular, 

 branched. Fructification : convex, wart-like sort scattered 

 over the surface, composed of obovate spores nestling among 

 moniliform, vertical filaments. Name, <rnA, a point or dot, 

 and <popeu, to bear, in allusion to the dot-like fructification. 



1. S. rhizodes, Ehr. ; frond subsolid, much and irregularly 

 branched, the branches subdichotomous, acute ; ramuli scat- 

 tered, forked ; sori densely covering the branches and ramuli. 

 Grev. Alg. Brit. p. 43, t. 6 ; Hook. Br. FL ii. p. 275 ; E. 

 Bot. t. 1688 ; Wyatt, Alg. Danm. No. 5 ; Harv. Plnjc. Brit, 

 t. Ixx. 



