Srr. GONGYLOSPERMEiE. {17) Fam. RIIODYMENIACEJ;. 



Plate LXXII. 

 EUTHOKA CRISTATA.— J^. G. Arj. 



Gen. Chak. — Frond membranaceous, flat, dicbotomo-pinnate, composed of two strata of 

 cells ; tbose of tbe inner stratum oblong, large ; of tbe outer coloured, minute, in 

 few rows. Conceptacles marginal, sub-spherical, with a closed cellular pericarp 

 (composed of concentrical layers of cellules at one point radiating) ; sporiferous 

 filaments very numerous, radiating from a central placenta, which is suspended in 

 the cavity of the pericarp by sub-simple filaments ; the fertile spore-threads 

 forming roundish masses of spores from their upper cells. Tetraspores cruciate, 

 lodged in the thickened apices of the frond. 



EuTHORA cristata. — Fronds membranaceous, much divided ; divisions 

 ii-regularly dichotomous, alternate or palmate, mostly linear or narrowed 

 upwards ; apices acute, laciniated or fimbriated ; tubercles spherical, 

 sessile ; tetraspores collected in the upper segments. 



EuTnoRA cristata. — /. G. Agardh, Sp. Gen. Alg. vol. ii. p. 385 ; Harv. N. B. A. 

 part 2, p. 150. 



Ehodtmenia cristata.— Grev. Ahj. Brit. p. 89; Hooh. Br. Fl. vol. ii. p. 290; 

 Endl. 3rd Suppl. p. 210 ; Harv. P. B. plate 307 ; Harv. Man. p. 126; 

 Harv. Syn. p. 105 ; Atlas, plate 40, fig. 184. 



Callophyllis cristata. — Kutz. Sp. Alg. p. 747. 



Sph^rococcus cristatus. — Ag. Sy7i. p. 29 ; Lijngl. Hyd. Ban. p. 13, t. 4 ; Ag. 

 Sp. Alg. vol. i. p. 300 ; Ag. Syst. p. 231 ; Hooh. Fl. Scot, part 2, p. 104 ; 

 Grev. Crypt. Scot. t. 85l; Fl. Edin. p. 296 ; Kiitz. Phyc. Gen. p. 410. 



Fucus cristatus. — Herb. Linn. ; Turn. Hist. t. 23. 



Fucus gigartinus.—Fl. Dan. t. 394 ; Mohr, Hist. Isl. p. 247 ; Gunn. Fl. Norv. 

 p. 847. 



Hab. — Growing on the roots and stems of Laminar ice in deep water. Very rare. 

 Annual. Summer. Wick ; Caithness ; Orkney and Shetland ; Frith of Forth {Dr. 

 Greville) ; Berwick {Dr. Johnstone). 



Geogr. Dist. — Arctic Sea ; shores of the North of Eui-ope ; Iceland ; eastern shores 

 of North America. 



Descuiption. — Root, a minute flattened disc. Fronds solitary or 

 slightly tufted, from a very short subcompressed stem, suddenly expand- 

 ing into a roundish subflabelliform flat frond, from half an inch to an 

 inch and a-half in length, much divided in a subpalmate or subalternate 

 manner; the branches generally short and bushy, frequently very 

 irregular, mostly linear or narrowing upwards, or occasionally slightly 



VOL. II. J, 



