Ser. Melanospeemkb. Fain. Chordariea. 



Plate CCLXXX. 



MYRIONEMA STRANGULANS, Grev. 



Gen. Char. Minute parasites, consisting of a mass of short, erect, simple, 

 jointed filaments, which spring from a thin expansion formed of 

 decumbent, cohering filaments, spreading in patches on the surface 

 of other Algae. Spores oblong, affixed either to the erect, or to the 

 decumbent filaments. Myrionema (Grev.), — from pvpios, numberless, 

 and vrjfia, a thread. 



Myeionema strangulans ; patches convex, confluent, brown; the vertical 

 filaments clavate, densely set ; spores obovate, on short stalks, 

 attached to the decumbent filaments. 



Myrionema strangulans, Grev. Crypt. Fl. t. 300. Harv. in Hook. Br. FL 

 vol. ii. p. 391. Harv. in Mack. FL Hib. part 3. p. 223. Harv. Man. ed. 2. 

 p. 51. /. Ag. in Gen. and Sp. Alg. vol. i. p. -48. Kiitz. Sp. Alg. p. 5-iO. 



Hab. Parasitical on the fronds of various Uhce and Enteromorphc. 

 Annual. Summer and autumn. Common. 



Geogr. Distr. Probably widely dispersed. 



Descr. The parasite first appears in the form of a dark brown stain, spotting 

 the Viva on which it grows, and at this stage consists of little more than 

 an imperfect membrane composed of prostrate filaments. As it advances 

 in growth the erect filaments are developed : the spots become convex, and 

 gelatinous, and the plant is matured. It then, when growing on the cylin- 

 drical fronds of an Euteromorpha, completely invests the stem, forming a 

 collar round it. Under the microscope, looking vertically on the parasite, 

 the whole appears like a soft cushion, composed of innumerable brown dots 

 set in a gelatinous matrix. These dots are the tips of the erect filaments, 

 and the proper structure may be seen either by making a thin transverse 

 slice, or by bruising the frond between two flat pieces of glass. The little 

 plant will then be resolved into its component parts. Spores of large size, 

 obovate, pedicellate, rising from the prostrate filaments, generally abundant. 

 Articulations of the erect filaments about once and a hall* as long as broad, 

 contracted at the joints, containing an olive endochrome. 



In our first volume arc figured (Plate KLI.) two species of 

 Myrionema, a genus founded by Dr. Greville for the reception 

 of the curious and beautiful little parasite here represented. 

 M. strangulans abounds on all our coasts, and will always afford 

 the possessor of a microscope ail interesting subject for exami- 

 nation. The dark brown specks on the fronds of Enteromorpha 



M 2 



