Olive—Occurrence of 0scillatoria Prolifica. iZo 
this reddish pigment is associated with a vigorous growth. The 
intensification of the color, as decomposition proceeds, argues 
also strongly for this conclusion. 
The daily determinations, from March to October, of the 
amount of carbon-dioxide dissolved in the water of Jamaica 
Pond, as made by Hyains and Richards, may be regarded as fur¬ 
nishing a very important clew to the revealing of one cause, at 
least, of the formation of a surface scum and the appearance of 
the reddish color. These authors found that whenever the 
Oscillatoria grew vigorously, the normal content of “carbon di¬ 
oxide disappeared and the water became not only neutral but 
alkaline . With the decay of the plant, the alkalinity disap¬ 
peared and carbon-dioxide again became normal and in one or 
two instances appeared in excess.” (02, p. 310). 
It seems to me readily conceivable, at any rate, that we may 
have in the lack of this important food-substance, carbon-diox¬ 
ide, a condition perhaps brought about by its being used up by 
the plant during the vigorous growth, the prime cause of the 
beginnings of decomposition and the consequent rising of the 
alga to the surface of the water and the appearance of the red 
pigment. 
Madison, Wisconsin, Aug. 3,1905. \ 
BIBLIOGRAPHY. 
Birge, E. A. 98.—Plankton Studies on Lake Mendota. II. 
Trans. Wis. Acad. Sciences. 11:274-448. 1898. 
Chodat, R. 96.—Sur la structure et la biologie de deux algues 
pelagiques. II. Oscillatoria rubescens DC. Journal de 
Botanique. 10: 341—349. 405—409. 1896. 
Farlow, W. G. 77. Remarks on some algae found in the water 
supplies of the city of Boston. Bull, of the Bussey Inst. 2: 
75—80. 1877. 
-83, I. Notes on fresh-water algae. Bot. Gaz. 8: 224. 
, 1883. 
-83, II. Relations of certain forms of algae to disagree¬ 
able tastes and odors. Proc. Amer. Assoc. Adv, Sci. 32: 
306. 1883. Abstract. 
Gomont, M. 93. Monographic des Oscillariees. Paris. 1893. 
