Sek. GONGYLOSPERME.E. ( 173 ) Fam. CERAMIACEtE. 



CALLITHAMNION BYSSOIDEUM.— ^m. 



Gen. Char. — Fronds filiform and articulated, sometimes at length in the older parts 

 cellular and partially opaque, single-tubed ; divisions mostly pinnate, dissepiments 

 hyaline. Fructification of two kinds, on distinct plants : 1. Favellse, mostly 

 lateral on the branches, and filled with minute spores ; 2. Tetraspores, external, 

 tripartite or cruciate. Name from /caA.bs, "beautiful," and fia/xros, "a shrub." 



Callithamnion hyssoideiim. — Fronds very slender, soft, and byssoid, 

 much branched from the base ; branches long, slender, and flexuous, 

 once or twice alternately pinnate, pinnae and pinnules very slender, more 

 or less flexuous and tapering ; articulations cylindrical, six to eight times 

 longer than broad, shorter upwards ; " tetraspores one or two, sessile on 

 the pinnules ;" favellse " binate, subterminal." 



Callithamnion hjssoideum. — Arnoit MSS.; Earv. in Hooh. Br. Fl. vol. ii. p. 342; 

 Wyatt, Alg. Damn. No. 185; Barv. P. B. plate 262; Earv. Man. 

 p. 178 ; Earv. Syn. p. 149 ; Alias, plate 58, fig. 269 ; /. G. Agardh, 

 Sp. Gen. Alg. vol. ii. p. 40. 



Hab. — On several Algae (especially Codium tomentosum), in tide-pools near low-water 

 mark. Not uncommon on the English and Irish coasts. Rare in Scotland. 



Geogr. Dist. ? 



Description. — Root 1 Fronds densely tufted, excessively slender 



and delicate, from one to three inches long, much branched ; branches 

 distichous, repeatedly pinnate, alternate, distant, more or less flexuous 

 and gradually tapering to a point, erecto-patent, longest in the middle 

 or near the base, giving the frond or branch an ovate or broadly lanceo- 

 late outline ; generally every joint produces its ramulus, but in the 

 larger branches the lowest joint or sometimes two are naked ; the pinnse 

 and pinnides are more or less incui'ved, the pinnules simple upward, but 

 sometimes the lower ones have a few in-egular ramuli. Articulations 

 of the stem and branches cylindrical, five, eight, or even more times 

 longer than broad, shorter upwards, and quite transparent, those at the 

 base of the stem only, partially filled with veins. Substance extremely 

 flaccid and delicate, closely adhering to paper in drying. Colour, " a fine 

 rosy lake, with a slightly purple or sometimes brown hue." Favellae 

 " binate, generally terminating tinincated branches." Tetraspores " ellip- 

 tical, sessile, rather large, borne on the sides of the pinnides, towai-ds 

 the base, one or two, rarely more, on each pinnule." — Fhyc. Brit. 



With this very delicate species we are but only imperfectly acquainted, 



