145 
Cylindrospermum macrospermum, Kg. Common throughout ; 
same general habit and duration as the last. 
Leptothrix calcicola, Kg. Stratum dull zruginous, or dull 
ferruginous. Common everywhere on damp or dripping rocks. 
All the year. 
Leptothrix eruginea (Kg.), Kirch. Doubtless common; but 
collected but once covering the sides of a large glass jar filled 
with spring water and left standing in the window for several 
weeks. The filaments formed a dense film. The side applied 
to the glass was somewhat variable, being bluish, faintly purplish 
or glaucous green; the other side was a very rich green. August, 
1886. 
In the waters of Montana diatoms are very numerous; not so 
much perhaps in number of species as in the vast and very palpa- 
ble aggregate of individuals. They often cover such plants as- 
Cladophora so completely as to obscure the character of their 
hosts, while even in mountain torrents, the boulders and lesser 
stones are covered with them so as to render the fording of a 
stream a slippery and, at times, even a dangerous task. Prof. 
C. Henry Kain has kindly examined our scanty collection in this 
branch. The following species are common and interesting : 
Synedra ulna (Nitzsch.), Ehr. On or with Spirogyra and 
Zygnema, sp.; very common. 
Cymbella gastroides, Kutz. Very common in cold, rapid 
streams, forming hemispherical, slippery, gristle-colored masses, 
with myriads of minute diamonds flashing on all sides when the 
sun shines clearly. 
Fragilaria capucina, Desmaz., is also very commonly mixed 
with foregoing species. The entire list reported by Prof. Kain is 
as follows : 
Synedra ulna (Nitzsch.), Ehr. 
Synedra (ulna, var.) Danica, Kutz. 
Meridion constrictum, Ralfs.; some specimens are quite near 
to M. circulare. 
Diatoma hiemale (Lyng.), Heiberg, var. mesodon, Grun. 
| Melosira varians, Agardh. 
Cymbella gastroides, Kutzing. 
Cymbella cymbiformis, Ehr. 
