MARINE ALG;E OF BEAUFORT, N. C. 411 



Plant mass very dark olive green; trichomes moderately long, rather straight, fragile, constricted at 

 joints, arcuate toward the extremities, tapering and obtuse at the apices, 7 to n mic. in diameter, cells 

 3 to 5 mic. long; apical cell somewhat capitate with convex and slightly thickened outer wall; trans- 

 verse walls granulated, cell contents pale green or olive. 



Maine to West Indies; Washington; Europe; Australia. 



Several large masses floating in harbor, August, 1909, in sparse tufts on marine grasses, shoals west 

 of laboratory, and near "Green Rock," Beaufort, N. C. 



A few other specimens belonging to this genus have been found at Beaufort in small 

 quantities on shells or marine plants, or growing directly on sandy shoals between tide 

 lines, but none has been obtained in sufficient quantity for a specific determination. 



Genus 2. Spirulina Turpin, ex Gomont. 



Spirulina, Turpin, 1827. tome 50, p. 309. 

 Spirulina, Gomont, 1892, tome 16, p. 249. 



Trichomes unicellular, thin, cylindrical, without a sheath, forming a regular, rather 

 loose or close spiral, having a characteristic spiral movement; apex not tapering, cell 

 contents homogeneous or slightly granular. 



Twenty-one species in fresh or salt water, gathered into a continuous layer or 

 scattered among other algae, in America, Europe, Africa, and Australia. 



A few filaments of an undetermined species of Spirulina were found on shells in 

 Pamlico Sound at Ocracoke, N. C. 



Genus 3. Phormidium Kuetzing, ex Gomont. 



Phormidium, Kuetzing, 1843, p. 190. 

 Phormidium, Gomont, 1892, tome 16, p. 156. 



Filaments showing evident sheaths, unbranched, agglutinate, usually forming a felt- 

 like mat with free ends torn and ragged, attached at the base or rarely floating; sheaths 

 thin, transparent, mucous, adhering to each other, partly or entirely diffluent; trichomes 

 constricted at the joints in some species, sometimes even becoming moniliform, straight 

 or curved but never regularly spiral, often tapering toward the apices, outer wall of 

 apical cell thickened, in some species, to form a calyptra. 



About 70 species, usually terrestrial or in fresh water, some species marine. 



Many filaments of an alga apparently belonging to this genus, but insufficient for 

 specific determination, were found on the hydroids inhabited by Acrochcetium infestans 

 growing on Dictyota dichotoma dredged from the coral reef offshore, August, 1914. 

 These filaments had trichomes 0.75 to 1.5 mic. in diameter with cells 0.75 to 3.0 (mostly 

 i to 2) diameters long, and were closely adherent to the stalks and rhizomes of the 

 hydroids. 



Genus 4. Lyngbya Agardh, ex Gomont. 



Lyngbya, Agardh. 1824. p. XXV. 

 Lyngbya, Gomont, 1892, tome 16, p. 116. 



Filaments possessing evident sheaths, free, unbranched, free floating, or forming 

 a densely intricate floccose or expanded mass; sheaths firm, of variable thickness, some- 

 times lamellose, colorless or rarely yellow brown; trichomes sometimes constricted at 

 the joints, obtuse or slightly tapering at the apices, outer wall of apical cell sometimes 

 thickened, forming a calyptra. 



Seventy-five species in fresh or salt water throughout the world. 



