22 THE FLORA OF NEBRASKA. 



Lyngbya ©bscnra Kuetz. Phyc. Gen. 224. 1843. 



Free or forming dark aeruginous strata; filaments nearly straight, bright 

 aeruginous changing to brown, articulations distinct, one-third to one- 

 sixth as long as wide, 10-15 ft in diam.; sheaths thin, hyaline, becoming 

 yellowish brown and lamellose in age. 

 United with the preceding by Gomont, Monogr. Oscil. 

 In lakes and ponds in the eastern part of the state. PI. II., Fig. 26. 

 L-yngbya vulgaris (Kuetz.) Kirch. 



Phormidium vulgare Kuetz. Phyc. Gener. 193. 1843. 



Stratum thin, mucilaginous, dark steel-blue to brown or turning yellow, be- 

 coming thickened in age; filaments straight, rigid; joints equal to or 

 shorter than the diameter, 5-9 /z in diam., apex some what attenuated, 

 occasionally somewhat curved. 

 On damp soil in greenhouse, Lincoln. PI. II., Fig. 22. 

 Gomont cites this as a synonym of Phormidium autumnale. 

 Iijugbya ochracea (Dillw.) Thuret Ann. Sci. Nat. Bot. 6, I., 279. 1875. 

 Conferva ochracea Dillw. Brit. Conf. 55. 1809. 

 Leptothrix ochracea Kuetz. Phyc. Gener. 198. 1843. 



Filaments very slender, fragmentary, scattered; diameter 2-3 //, not articulate. 

 Floating in fragile, ochraceous masses. PI. II., Fig 20. 



5. PHORMIDHJM Kuetz. Phyc. Gener. 290. 1843. 



Filaments slender, without oscillating movement, usually united into a mu- 

 cilaginous or membranaceous stratum; sheaths hyaline, often absent or 

 at least not discernible; filaments cylindrical, never spiral, articulations 

 often indistinct. 

 Etymology: Greek <popfiiSiov, a fagot. 

 Phormidinm laminosum (Ag.) Gomont Ann. Sci. Nat. Bot. 7, XVI., 167. 1892. 

 Oscillaria laminosa Ag. Flora X., 633. 1827. 



Stratum light aeruginous or sometimes brick-red, slender, membranaceous, 

 broadly expanded; filaments flexuose, some of them usually coiled, densely 

 intricate, light aeruginous, scarcely constricted; apex straight, slightly at- 

 tenuate, not capitate, 1-1% V- broad; articulations 2-4 \t long. 

 In stagnant water in ponds and ditches; it nourishes especially in mineral 

 or thermal waters. 

 Phormidinm tenne (Menegh.) Gomont 1. c. 169. 



Anabaena tenuis Menegh. Consp. Algol. Eugan. 8. 1837. 



Stratum light aeruginous, thin, membranaceous, expanded; sometimes soli- 

 tary or scattered; filaments elongated, sub-erect; sheath slender, often 

 inconspicuous; filaments 1-2 /j. in diam., straight, slightly constricted at 

 the joints, articulations often indistinct; apex at first straight, finally be- 

 coming curved and attenuate, not capitate; articulations as long to three 

 times as long as wide. 

 With other algae. PI. II., Fig. 23. 

 Phormidinm antnmnale (Ag.) Gomont 1. c. 187. 

 Oscillaria autumnalis Ag. Disp. Alg. Suec. 36. 1812. 

 Oscillaria antliaria Ag. Syst. Alg. 63. 1821. 



Stratum gelatinous, broad, sub-membrauaceous, dark steel-blue to olivaceous; 

 filaments rather rigid, straight, sometimes oscillating; apex attenuated, 

 curved, 4^-5 /* in diam.; articulations sometimes indistinct, about as 

 long as wide; cell contents pale steel-blue, nearly homogeneous. 

 Around pumps, cisterns, etc., Lincoln. PI. I., Fig. 15. 



