400 ALG2K GLOIOCLADE.E. [Scythymenia. 



In fresh-water pools, near the sea. Rivulet near Torquay, Dr. 

 Hooker. Appin, Capt. Carmichael. — " Fronds unattached, scattered at 

 random in the clefts of the rocks, globular, smooth, olive-green, diaph- 

 anous, from { to 1| inch in diameter, the larger ones generally com- 

 pressed, hollow and sometimes ruptured." Carra. MSS. 



8. N. sphcericum, Vauch. {small globose Nostoc); densely ag- 

 gregated minute globose solid smooth olivaceous. — Ag. Syst. 

 Alg. p. 20. — Ulva pisiformis, Huds. 



In fresh-water. — " On mural rocks, exposed to the trickling of 

 water," Captain. Carmichael. — "Fronds from half a line to two lines in 

 diameter, globular, firm, smooth, solid, heaped on each other like a par- 

 cel of small shot. Internal filaments rather thinly scattered through 

 the mass." Carm. MSS. 



** Polymorphous. 



9. N. verrucdsion, Vauch. (plaited Nostoc); fronds large gre- 

 garious confluent subglobose plaited, at length hollow blackish- 

 green Ag. Syst. Alg. p. 21. — Tremella verrucosa, Linn. — 



Hudson. 



On stones, in alpine rivulets, common. — " Fronds half an inch or 

 more in diameter, confluent, adhering firmly to the rock, roundish, 

 plaited, at length hollow. Filaments short, curled and fragile." 

 Carm. MSS. 



3. Bluish, small. 



10. N. cceruleum, Lyngb. (bluish Nostoc); frond minute glo- 

 bose solitary solid smooth pale-blue subpellucid, filaments sim- 

 ple curved moniliform. Grev. — Lyngb. Hydroph. Dan. t. 68. 

 Grev. Crypt. Fl. t. 131. Ag. Syst. Alg. p. 22. 



In flowing water and very moist places, attached to mosses ; near 

 Callendar, Dr. Greville. — Plants 1 — 2 lines in diameter, gelatinous, glo- 

 bose, gregarious, but distinct; subpellucid, of a delicate pale-blue colour, 

 rarely almost colourless. In drying, they shrink almost to nothing. 

 Grev* I. c. 



APPENDIX. 



97. Scythymenia. Ag. Scythymenia. 



Frond tough, coriaceous, spreading, its surface reticulated 

 with raised, irregularly anastomosing veins ; entirely composed 

 of byssoid branched fibres, intermixed with granules. — Name ; 

 tsxvroz, leather, and vfirjv, a membrane ; from the leathery texture 

 of the frond. — A highly curious plant, found only, that I am 

 aware of, in a single situation. Agardh, supposing it may be 

 related to Palmella, places it as an appendix to the Nostochinece. 

 I cannot perceive that it has any affinity with that genus or any 

 of its allies ; but rather think, that if it be an Alga at all, it 

 would range better with the Byssoidea — perhaps next to Hy- 

 grocrocis. 



