OSCILLATORIACEAE. 623 



5. PLECTONEMA Thurct ex Goniont, Monogr. IIG. 1S93. 

 Trichomes torulose ; filaments inhabiting colonies of Roiatinous 

 Trichomes not torulose; filaments matted into a rose-colored - '">« "'"riim. 



membrane. 



L'. /', rtiHioUttn. 



1. Plectonema nostocorum Born, ex Gomont, Monogr. 122. ;>/. 7. /. 11. 1893. 



New rrovidence, in colonies of (Jlocothccc, etc. -.—common evervwh.-r.' in Klmllar 

 habitats. Type from France. 



2. Plectonema roseolum Gomont, Moiiogr. 122. pi. 1. f. 9-10. 1893. 



On sand and mud, New Providence: — Europe; North America. Tvi..- fr..m 

 Germany. 



6. SYMPLOCA Kiitz. ex Gomont, Monogr. 124. 1893. 



1. Symploca hydnoides forma fruticulosa Gomont, Monogr. 127. 1S03. 



North Cat Cay and Great Bahama : — the typical form Is widely distributed, the 

 type from Great Britain ; no type locality for the forma fruticulosa which occurs 

 generally with the typical form. 



7. HYDROCOLEUM Kiitz. ex Gomont, Monogr. 71. IMt.''.. 



Sheath cylindrical, distinct. 1. II. comoidt h. 



f;;heath irregular, often becoming shapeless and diflluent. 



Trichomes usually 9-11 w. in diameter. 2. II. l}inuh]/arcum. 



Trichomes seldom under 17/i in diameter. 



Filaments forming tufts attached to algae or to sand 

 and rocks ; sheaths broad, with irregular and erose 



margins, but fairly persistent. 3. II. canthdiiilosmum. 



Filaments not attached, forming an indefinite gela- 

 tinous stratum ; sheaths very irregular or shape- 

 less, soon diffluent. 4. H. glutinosum. 



1. Hydrocoleum comoides Gomont, Monogr. 73, pi. 12. f. 3-5. 1893. 



Great Bahama and Exuma Chain: — Bermuda; Guadeloupe; Australia. Type 

 from Australia. 



2. Hydrocoleum lyngbyaceum Kiitz. ex Gomont, 75. pJ. 12. f. 8-10. 1893. 



Caicos Islands and Great Ragged Islands : — of general distribution. Type from 

 France. 



3. Hydrocoleum cantharidosmum Gomont, Monogr. 74. pJ. 12. f. 6-7. 1893. 



Mariguana : — widely distributed in warmer waters. Type frt>m the Canary 

 Islands. 



4. Hydrocoleum glutinosum Gomont, Monogr. 77. 1893. 



Caicos Islands : — Europe and America. Type from Sweden. 



The genus Hydrocoleum is fairly distinct from neighboring genera, but the spe- 

 cies have much similarity. Absolute certainty o( determiniiiion cnu be obtained 

 only by observing the development of the living plant. 



8. SCHIZOTHRIX Kiitz. ex Gomont, Monogr. 30. 1S93. 



Sheaths hyaline, trichomes 2-3 ^ in diameter. 1. S. va</inata. 



Sheaths w'ith inner layer violet or slate color; outer layer hyaline, 



trichomes 7-9^1 in diameter. 2. S.chalybca. 



1. Schizothrix vaginata Gomont, Monogr. 40. pi. 7. f. 1-4. 1893. 



New Providence and Caicos Islands: — generally distributed. Typo from Switzer- 

 land. 



