Ser. Melanospekhe.*. Pam. Bictyoteie. 



Plate CCLXX. 



LITOSIPHON PUSILLUS, Har. 



Gen. Char. Frond unbranched, cylindrical, cartilaginous, subsolid, at 

 length tubular, composed of several rows of cells ; the surface areo- 

 lated. Fructification', solitary or aggregated naked spores, scattered 

 irregularly over the surface of the frond. Litosiphon [Harv.), 

 from Xiros-, slender or mean, and atycov, a tube. 



Litosiphon pusillus; fronds tufted, thread- shaped, very long, equal in 

 diameter throughout, reticulated, clothed with pellucid hairs ; spores 

 scattered. 



Litosiphon pusillus, Harv. Man. Ed. vol. ii. p. 43. 



Chlorosiphon pusillus, Harv. inP/tyc. Brit.xoi. i. p. 10. Kiitz. Sp. Alg. p. 484. 



Asperococcus pusillus, Carm. in Hook. Br. Fl. vol. ii. p. 277. JVyatt, Alg. 

 Damn. no. 58. Harv. in Mack. Fl. Hib. part 3. p. 175. Harv. Man. Ed. 

 vol. i. p. 35. J. Ag. Gen. et Sp. Alg. vol. i. p. 78. 



Hab. Parasitical on Chorda filum. Annual. Summer. Common all 

 round the coast. 



Geogr. Distr. Shores of Europe. 



Descr. Fronds very densely tufted, clothing the plant on which they grow in 

 continuous series for the space of several feet, completely concealing the 

 surface and spreading on all sides equally ; from two to four inches long, 

 as thick as hog's bristle, straight, or more commonly variously waved or 

 twisted. When young the whole frond is beset with slender, byssoid, arti- 

 culated fibres, like those found in Myriotrichia. These gradually wear 

 away, and then the fronds become more twisted and less lubricous. In 

 young plants the frond is nearly solid, composed of several strata of cells, 

 the inner ones of which are large and empty, the outer gradually smaller, 

 and those of the two or three external rows (constituting the periphery) 

 filled with granulated endochrome. The central cells first perish, and the 

 plant becomes tubular, but the tube does not seem to have regularly de- 

 fined limits. The surface under the microscope appears reticulated with 

 quadrate cells, which are disposed in longitudinal lines. Among these cells 

 one is here and there larger and more prominent than the rest, containing 

 a darker-coloured endochrome : these are supposed to be the spores, and no 

 other fructification has yet been observed. Substance somewhat cartila- 

 ginous, but soft and lubricous, closely adhering to paper. Colour at first 

 a greenish, afterwards a brownish olive. 



The old fronds of Chorda filum arc frequently infested, towards 

 the close of summer, with the parasite here figured, which 

 changes them into shaggy ropes, soft and slippery to the touch. 



