OSCILLATORIACEAE. 621 



3. Oscillatoria Corallinae Gomont, ilonogr. 238. pi. 6. f. SI. 1893. 



On Halimeda, etc., Marigaana :— Europe ; North America. Type from France. 



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



marlne'^T/pl IroSflwTden.'^'"'^"^"'" aistrlbntion, fresh water, occasionally sub- 



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



1. Trichodesmimn Thiebafltii Gomont, Jour, de Bot. 4: 356. 1890. 



Pelagic in Gulf Stream, between Gun Cny and Florida :— Bermuda : Guadeloupe- 

 and Canary Islands. Type from Guadeloupe. nuciuupe , 



3. PHORMIDnnM Kiitz. ex Gomont, Monogr. 176. 1893. 



Trlchomes distinctly torulose, 1.2-2.3 n in diameter. l p fraqilt 



Trlchomes not torulose. 



Trlchomes less than 2n in diameter; forming definite carti- 

 laginous discs or cushions. 2. P.Hendcraonii 

 Trlchomes 2u in diameter or more. 



Trlchomes 2-2.5 u in diameter, cells 1.5-3 diameters long. 3. P.raUlerlanum. 

 Trlchomes over 3u in diameter. 



Apical cell obtusely conical, trlchomes 3-4.5 « in di- 

 ameter. 4. p, CoHum. 

 Apical cell truncate, cells 5u in diameter or more. 

 Cells usually shorter than their diameter, dissepi- 

 ments often constricted, sheaths loose and dif- 

 fluent. 5. P. Retzii. 

 Cells usually longer than their diameter, trichomes 



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



1. Phormidium fragile Gomont, Monogr. 183. pi. 4. f. 13-15. 1893. 



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

 ica. Type from Italy. 



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



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

 Eieo. Type from Cuba. 



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



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

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



4. Phormidium Corium Gomont, Monogr. 192. pi. 5. /. IS. 1893. 



Great Ragged Island ; — ^generally distributed. Type from Sweden. 



5. Phormidium Betzii Gomont, Monogr. 195. pi. 5. f. 6-9. 1893. 



Caicos Islands : — generally distributed. Type from Sweden. 



6. Phormidium pulvinatum Collins, sp. nov. 



Marinum. Strato pallide aerugineo, erasso, compaeto, pulvinato; filam- 

 entis rectia vel leviter curvatis, vaginis tenuibus, membranaeeis, persistentibus, 

 adhaerentibus nee diffluentibus ; trichomatibus pallide aerugineis, eylindricis, 

 apice rectis, non eapitatis nee attenuates ; cellulis 7-9 ii diam., i— 14 diam. 

 longis; dLssepimentis non granulatis; eellula apicali rotundata. 



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

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

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

 tate, 7-9 /t in diameter, cells f-li diameters long, dissepiments not granulate; 

 apical cpl! rounded. 



