Fanning : ALG OF THE ST. PAUL CITY WATER. 611 
Synedra and Astertonella. Of the Chlorophycee, Scenedes- 
mus and Raphidium were present most of the time. Among 
the Cyanophycee, Osczllatoria and Celospherium were prac- 
tically constant. 
The effect of the cold on some of the varieties is shown by 
the accompanying plates (Pl. XLIII. and XLIV.). It will be 
seen that a fall in temperature coincides with a decrease in the 
numbers of all except Oscz/latorza, which shows a gradual in- 
crease with the cold and is abundant for several weeks during 
the severest weather. 
The desmids, more plentiful in the fall than at any other 
time, although never abundant, disappeared after the cold wave 
of the third week in December. Another fall in temperature 
about the fourth week in January banished most of the Chloro- 
phycez and cleared the field of Celospherium, but some of the 
diatoms persisted until the zero weather in February, when 
most of them disappeared. FAvagz/ar¢a was abundant in Jan- 
uary and about January 30th, when Osc7/latoria and Fragilaria 
were practically the only forms seen, the water contained con- 
siderable sandy débris and entangled in it were quantities of 
resting spores of Glwotrichia. 
The observations vary from year to year so that a record 
should be kept for several years before one could find what 
forms were both constant and abundant. For example, in the 
fall of 1898, Anabena was ‘‘common,” but in the following 
year it is only marked “ present.” 
I wish to thank Mr. P. F. Lyons, of the St. Paul Weather 
Bureau and Mr. John Caulfield, Secretary of the Water Board, 
St. Paul, for their kind assistance. 
EXPLANATION OF PLATES XLIII. anp XLIV. 
Table showing relation between abundance of certain forms and 
temperature. XLIV. is a continuation of XLIII. 
PEAT EH wliVe 
1. Calastrum microporum Naeg. var. spectosum Wolle. Freshw. 
eigae U.S. 170. Al. 156. f. g. 1887. 
2. Pediastrum duplex Meyen Beob. iiber Algenformen. in Nova 
Acta Acad. Leop. Carol. 772. 1829. 
3. Scenedesmus guadricauda (Turp.) Bréb. Alg. Falais. 66. 1835. 
4. Scenedesmus bijugatus (Turp.) Kg. Syn. Diat. 607. 1833. 
5. Rhaphidium polymorphum Fresen. var. aciculare (A. Br.) 
Rabenh. Fl. Eur. Algar. 3: 45. 1868. 
