1917] 
MOORE—ALGAE OF DEVILS LAKE, NORTH DAKOTA 297 
Oscillatoria tenuis Agardh, Alg. Decades 2: 25. 1813. 
ws represented in four collections. 
illatoria sp. А small form occurring in eleven different 
samples. Cell contents homogeneous and walls indistinct. 
Up to 2 џ in diameter. Resembling іп a general way the de- 
scriptions of O. subtilissima Kuetzing but never circinate and 
color blue-green. Also a trifle too large for the measurements 
given for this species. 
Genus PLECTONEMA Thuret 
Plectonema tenue Thuret, Ann. d. Sci. Nat., Bot. VI. 1: 380. 
1875. Numerous filaments of this species were obtained from 
surface tow in one of the smaller bays of the lake. While it 
is probable that the material had become detached from 
stones, a search along the shore in shallow water failed to 
reveal any indication of from where the specimens had come. 
Genus sPIRULINA Turpin 
Spirulina major Kuetzing, Phye. Gen. 183. 1843. Ап 
abundant and widely distributed species, being found in four- 
teen collections. 
Spirulina Nordstedtii Gomont, Monogr. Oscill. 272. 1893. 
Notable as being the only characteristic marine form found. 
Spirulina subtilissima Kuetzing, Phye. Gen. 183. 1843. 
Found in one collection only. А salt-water and sulphur- 
spring form. 
Spirulina tenerrima Kuetzing, Phye. Gen. 183. 1843. Rare. 
Family NosrocACEAE 
Genus ANABAENA Bory 
Anabaena flos-aquae (Lyngbye) Brébisson in Brébisson & 
Godey, Alg. des Environs de Falaise, 36. 1835. Not common 
during any period of summer or fall nor forming the predom- 
inant part of the plankton as is frequently the case. Found 
so as to be definitely identified in but one towing, although 
bits of filaments which might have been 4. flos-aquae occurred 
in several other collections. 
