See. MELANOSPERME^. ( 137 ) Fam. CHORDARlEiE. 



MYRIONEMA STRANGULANS.— G^re?). 



Gen. Char. — Fronds formed of two strata of articulated filaments: 1, forming a thin 

 stratum, creeping and cohering; 2, erect, simple. Fructification, consisting of 

 obovate spores, attached either to the erect or creeping filaments. Name from 

 Hvpios, "a myriad," and vriixa, "a thread," in allusion to the multitude of 

 minute filaments of which the plants are composed. 



Myrionema strangulans. — Fronds somewhat convex, spreading, often 

 confluent, dark brown ; filaments clavate, closely compacted ; spores 

 roundish obovate, pedicellate, attached to the creeping filaments. 



Myrionema strangulans. — Grev. Crypt. Fl. t. 300; /. G. Agardh, Sp. Gen. Alg. 

 vol. i. p. 48; Kiits. Sp. Alg. p. 540 ; ffarv. in Mack Fl, Hib. part 3, 

 p. 223 ; Haw. P. B. plate 280 ; Harv. Man. p. 51 ; Harv. Syn. p. 47 ; 

 Atlas, plate 16, fig. 68 ; Jlarv. N. B. A. part 1, p. 132. 



Hab. — Parasitical on the fronds of various Ulvce and Enteromorphce. Annual. Summer 

 and autumn. Very common. 



Geogr. Dist. — Not correctly known ; likely to be widely dispersed. 



Description. — Plants formed of numerous decumbent filaments 

 closely appressed to the sm-face of the plants on which they grow, 

 forming a very thin stratum of simple articulated filaments, closely 

 adhering together ; cells short, angular ; from these arise short, erect, 

 simple, somewhat club-shaped filaments, obtuse and rounded at the 

 apices ; the cells about as long as broad, or towards the apex rather 

 longer than broad. Fructification : obovate or pyriform spores, attached 

 to the creeping filaments by short one or two -jointed pedicels, about 

 one-third the height of the erect filaments. Substance subcartilaginous, 

 scarcely adhering to paper. Colour, dark brownish olive. 



This curious parasite is by no means unconnnon on all our coasts, but 

 is very uncertain in its appearance. When it does occur, it generally 

 completely covers the patch or even the pool where it fixes its habitat. 



It generally occurs on some of the green Algae, such as Ulva, 

 Enteromorpha, or Conferva, appearing in the form of minute, dark 

 brown, almost black spots, at first consisting of the creeping filaments 

 only, which spread over the surface of the plant, in the filiform species 

 often entirely investing it, and at length emitting from every joint of 

 the creeping filaments, which form a thin membranous base, the erect 

 filaments, when the surface becomes somewhat convex and lubricous. 



VOL. III. "^ 



