144 
Tolypothrix distorta, Kg. Everywhere in flowing water, 
growing czspitose on the rocks. Filaments of our specimens 
measure 12-20 # diameter. July to October. 
Tolypothrix pulchra, Kg. Common as the last; on dripping 
rocks and on wet wood-work of dams, flumes and the like, sub- 
merged twigs, etc., in springs and streams. July to October. 
Nostoc muscorum, Ag. Abundant on moss under dripping rocks. 
Nostoc calctcola, Ag. Plentiful on the rocks at the ‘‘ Great 
Fall” of the Missouri, which are kept constantly wet by the drift- 
ing spray. ; 
Nostoc commune, Vauch. Common throughout the State. 
On the high foot-hills (5,000 to 7,000 ft.), on the alkaline plains 
and in the valleys. Extremely variable ; in innudated places, 
where the water is kept warm by the sun’s rays, this nostoc grows 
with marvelous rapidity, and frequently attains a diameter of ten 
inches and half a inch in thickness. 
Nostoc sphericum, Nauch. This small Species is particularly 
partial to damp rocks in shady ravines. 
Nostoc verrucosum, Vauch. Common at the Falls ofthe Mis- 
souri and in spring water impregnated with lime. In the fall of 
the year this species is torn from its hold on submerged rocks in 
the upper Missouri River, rises to the surface and floats to the 
shore in large numbers. Sometimes watery, hollow specimens, 
the size of bantam eggs are picked up. This species seems to 
take the place of WV. pruntforme, Ag., with us. 
Nostoc flagelliforme, Berk. & Curt. Very common on the 
alkali plains about Helena and thence southward and westward. 
As one walks carelessly along, this curious Mostoc looks like small — 
weather-beaten, entangled tufts of black horse hair. Hitherto 
only reported from Texas. See Wood’s ‘ Contributions,” p. 226, 
and Wolle’s ‘“‘Fresh-Water Alge,” p. 285. This species is so 
very distinct from all other known species that it could never be 
mistaken for any of them. It is frequently in company with the 
plains form of VV. commune. 
Spherozyga polysperma. Common in open, muddy pools 
heated by the sun’s glare; rising to the surface in small frothy, 
scummy masses. Ponds and semi-stagnant mud-bottomed parts of 
streams in the mountains and on the plains, June to November. 
