OSCILLATORIACEAE. 621 



3. Oscillatoria Corallinae Gomont, Monogr. 238. ;»/. 6. f. 21. 1893. 



On HaUmcda, etc., Mariguana : — Europe; North Arm-rlcn. Type from Trance. 



4. Oscillatoria tenuis Ag, ex Gomont, Monogr. 241. 1893. 



Watling's Island: — of world-wide distrihutlon. fresh water, oconslonallv s,,!,- 

 marine. Type from Sweden. • 



2. TRICHODESMIUM Ehrenb. Ann. Phys. u. Chem. 18: 506. 1830. 



1. Trichodesmium Thiebautii Gomont, Jour, do Bot. 4: 356. 1890. 



Pelagic in Gulf Stream, between Gun Pay and Florida : — Bermuda : Guadeloupe • 

 and Canary Islands. Type from Guadeloupe. 



3. PHORMIDIUM Kiitz. ex Gomont, ^fonogr. 176. 1893. 



Trichomes distinctly torulose. 1.2-2 3 u in diametor. 1. P. franiU 



Trichomes not torulose. 



Trichomes less than 2 << in diameter; forming definite carti- 

 laginous discs or cushions. 2. I'. ![( mlrrftnuii. 

 Trichomes 2u in diameter or more. 



Trichomes 2-2.5 u in diameter, cells l.."-3 diameters long. ?,. P. vahlrrinnum. 

 Trichomes over ^u in diameter. 



Apical cell obtusely conical, trichomes ,3-4. . 5 w in di- 

 ameter. 4. P. Corium. 

 Apical cell truncate, cells T* m in diameter or more. 

 Cells usually shorter than their diameter, dissepi- 

 ments often constricted, sheaths loose and dif- 

 fluent, n. P. Rrizii. 

 Cells usually longer than their diameter, trichomes 



always cylindrical, sheath close, persistent. 6. P. puhinntum. 



1. Phormidium fragile Gomont, Monogr. 183. pi. 4. f. 13-1.'>. 1893. 



On walls of fresh-water tanks. New Providence : — Europe : Africa ; North Amer- 

 ica. Type from Italy. 



2. Phormidium Hendersonii M. A. Howe. Smiths. :Nrisc. Coll. 68": 3. 1918. 



Forming definite discs or cushions on rocks, Watling's Island : — Cuba, Porto 

 Rico. Type from Cuba. 



3. Phormidium valderianum Gomont, Monogr. 197. pi. 4. f. 20. 1893. 



Among other algae. New Providence, North Cat Cay. Watling's Island: — Europe; 

 North America ; fresh water and marine. Type from Italy. 



4. Phormidium Cdrium Gomont, Monogr. 192. pJ. '>. f. IS. 1893. 



Great Ragged Island : — generally distributed. Type fr<im Sweden. 



5. Phormidium Retzii Gomont, Monogr. 195. pi 5. f. G-9. 1893. 



Caicos Islands : — generally distributed. Type from Swt'don. 



6. Phormidium pulvinatum Collins, sp. nov. 



Mariniim. Strato pallida aerugineo, crasso, compacto, pulvinato; filam- 

 entis rectis vel leviter eurvatis, vaginis tenuibus, membranaceis, persistontibus, 

 adhaerentibus nee dlffliientibns ; trichomatibus ]>allide aeruginois, cylindriois, 

 apiee reetis, non capitatis nee attenuatis; collulis 7-9 m «Ham., 5-H diam. 

 longis; dir,sepimentis non graniilatis; cellula npieali rotundata. 



Stratum pale aeruginous, thick, compact, pulvinato; filaments straight or 

 slightly curved; sheaths thin, membranaeoous, persistent, adherent but not 

 dififluent; trichomes pale aeruginous, cylindrical, apex not attenuate nor capi- 

 tate, 7-9 M in diameter, cells 3-H diameters long, di.ssepiments not granulate; 

 apical cell rounded. 



