Rivularia.] alga: gloioclade^e. 39 1 



erect, mostly simple filaments, " fixed at their base to a thin 

 expansion" (Grev.). Fruit: capsules at the base among the fila- 

 ments.— Name ; ftvpos, a thousand, and vrrpa, & filament; from 

 the innumerable filaments which unite to form the frond. — A 

 genus of extremely minute parasites, which it was Capt. Car- 

 michael's wish to have called " Linkia." The " thin expan- 

 sion," described by Greville, I am inclined to suspect, may be 

 only the excoriated epidermis of the Ulva on which the para- 

 site grew. 



1. M. strdngulans, Grev. (convex Myrionema); " subconvex 

 confluent, filaments subcylindrical simple, capsules shortly 

 pedicellated " affixed to the basal lamina." Grev. Crypt. Fl. 

 t. 300. 



On various Ulva:. — 1—2 lines in diameter, brown. 



2. M. punctiforme, Harv. (plane Myrionema); very minute plane 

 scattered, filaments attenuate at the base simple, capsules ses- 

 sile affixed to the filaments. — Linkia punctiformis, Lyngb. Hy- 

 dro ph. t. 66. — Carm. MSS. cum icone. 



On Chylocladia c/avel/osa, Captain Carmichael. — Half a line in dia- 

 meter. 



3. M. clavdtum, Harv. (clavate Myrionema); very minute 

 rather convex, filaments clavate mostly bifid, capsules pedicel- 

 late affixed to the filaments — Linkia clavata, Carm. MSS. cum 

 icone. 



¥* On a thin purplish crust, which covers the pebbles at the half-tide 

 l eve l _The parasite is so much of the colour of the crust, that it re- 

 quires a microscope to detect it." Captain Carmichael. 



Tribe XX. Rivulariejb. 



Plants more <» less globose, ,o eer filiform, carnosc, composuJ oj 

 continuous filaments annulated within* 



91. RlVULARIA. Roth. Rivularia. 



Frond globose or lobed, rarely incrusting, green or olivace- 

 ous, carnose or gelatinous, composed <>i' continuous filament! 

 annulated within, and surrounded by or set in gelatine-— 

 Named in allusion to the fresh-water habitat of some of the 

 original Bpecies:— many, however, are Pound in tli<' sea.— This 

 genus contains three natural gr< upes or Bub-genera, correspond- 

 ing with the following sections. 



Sect. 1. (Rivularia, Hoih.— Linkia, Lyngb.) : frond verm 

 for,,,, rarely incrusting. Filaments close-set, sparingly annu- 

 lated within, i mostly) dichotomously branched, ra liaHngfrom a 

 common fi a d base* 

 I. R.dtra, Roth, (black Rivularia); fronds minute scattered 



