4 ! 4 BULLETIN OF THE BUREAU OF FISHERIES. 



Thirteen species in fresh or salt water or on the ground, sometimes growing among 

 other algae, throughout the world. 

 Microcoleus chthonoplastes (Mertens) Thuret, ex Gomont. 



Conferva chthonoplastes, Mertens, in Flora Danica, 1818, Fasc. 27, p. 8, pi. 1485- 



Microcoleus chthonoplastes, Thuret, 1875. P- 3?8. 



Microcoleus chthonoplastes, Farlow, 1882, p. 33, pi- 2. i- 3- 



Microcoleus gracilis, Wolle, 1887, p. 306, pi. 203, f. 10-11. 



Microcoleus anguiformis, Wolle, 1887, p. 306. 



Microcoleus chthonoplastes, Gomont, 1892, tome 15, p. 353, pi- 14, f. S~8- 



Microcoleus chthonoplastes, Forti, in De Toni, 1907, p. 371- 



Microcoleus chthonoplastes, Tilden, 1910, p. 155, pi. 6, f. 28. 



P. B.-A. Nos. 153, 906, i8s4- 



Filaments forming a. dull or dark green, ragged, spreading, compact, stratified mass, made up of 

 layers of different colors, or growing sparsely among other algae; tortuous, not often branched; sheaths 

 cylindrical, unequally roughened on the surface, with apex usually open, sometimes entirely dissolving; 

 trichomes blue-green, short, nearly straight, many within the sheath, usually densely aggregated into 

 bundles, rarely twisted into cords, constricted at the joints, 2.5 to 6 mic. in diameter, cells 3.6 to 10 

 mic. long, apex of trichome attenuated, apical cell not capitate, acutely conical, transverse walls not 

 granulated. 



Canada to North Carolina; Texas; Ohio; Illinois; Dakota; Washington; West Indies; warm and 

 temperate waters generally. 



Very abundant with Chroococcus turgidus and Plectonema battersii on ocean beach at Ocracoke, 

 N. C., covering many square meters just beyond high-tide line, August, 1907. 



Family 2. NOSTOCACE^C (Agardh) Kirchner. 



Nostochaceae, Forti, in De Toni, 1907, p. 383. 



Trichomes simple, consisting of similar vegetative cells, not differentiated into basal 

 and apical regions, not tapering to hairs at the apices, usually provided with heterocysts, 

 naked or inclosed in a mucous, gelatinous, or membranaceous sheath ; multiplication by 

 gonidia and hormogonia. 



Usually aeruginous green. Trichomes straight or twisted or curved, of equal 

 diameter throughout or tapering very slightly toward the apices, heterocysts terminal 

 or intercalary. Sheaths usually gelatinous, often dissolving into an inclosing jelly, 

 often adhering to each other, more rarely membranaceous and cylindrical, colorless or 

 yellowish or olivaceous, containing one or more trichomes. 



The Nostocaceae live on moist earth, among mosses, etc., often in quiet fresh water, 

 sometimes in rapid streams, sometimes in salt or brackish water, a few being endophytic. 



About 220 species throughout the world. 



Genus Microchaete Thuret, ex Bornet and Flahault. 



Microchaete, Thuret, 1875, P- 3?8 (7). 

 Microchaete, Bornet and Flahault, 1887, p. 83. 



Filaments possessing evident sheaths, unbranched, erect, attached at the base, 

 solitary or forming small cushionlike tufts; trichomes single within the sheath, hetoro- 

 cysts basal or intercalary, gonidia formed near the base. 



Eleven species, all minute, in fresh or salt water, widely distributed. 

 Microchaete nana Howe and Hoyt. PI. CXVII, figs. 12-17. 



Microchtete nana, Howe and Hoyt, 1916, p. 105, pi. 12, figs. 12-17. 



Plants inconspicuous, almost microscopic, forming loose, scattered clusters over the surface of 

 the host; filaments mostly o.i to 0.2 mm. long, curved near base or near middle, usually more or less 

 horizontal toward the base and erect toward the apex, sometimes almost prostrate throughout or almost 



