126 Wisconsin Academy of Sciences, Arts, and Letters. 
quantities of the plant would come to the surface, buoyed up by 
the gas bubbles, a phenomenon to which they refer as the 
“blooming time” of the Oscillatoria. They say further in this 
connection that this phenomenon never happened except when 
an air temperature of 80° F. and over was accompanied by a 
bright sun and quiet water. (04, p. 270). Only on two days in 
thirteen years did this “blooming” result in a large amount of 
scum; while on about five other days of this time; a slight scum 
was formed. 
The maximum growth, which took place generally during the 
long days of June, was followed in July and August by a de¬ 
creased development, when the plant would be colored usually 
a more or less brilliant blue-green. In September, the “spore¬ 
like” (04, p. 270) bodies were formed, always few-in number 
in comparison with the amount of the plant in the water, which,, 
in their opinion, apparently serve to carry the plant through ex¬ 
ceptionally severe conditions. Even in late October, however, 
these authors have observed that a succession of warm days will 
frequently permit of a rejuvenescence and a fairly vigorous 
growth results along the edges where the water is warm. Dur¬ 
ing the winter, according to these investigators, the plant lies 
dormant, either in the form of broken threads of various lengths 
and of various stages of arrested development, or in the form of 
spores. These fragments or spores rest either on the bottom in 
shallow water or they appear to be held suspended in the denser 
water near the bottom of the deeper portion. As the spring ad¬ 
vances and the surface of the water becomes warmed to a tem¬ 
perature of about 60° F., the authors assert that the plant be¬ 
gins to grow; and growth continues until the water reaches a 
temperature of 72° F., when rapid breaking up of the filaments 
occurs. 
The alga in Jamaica Pond was at last, in September, 1903, 
killed by means of an application of copper sulphate, and the 
authors were able to find during the following spring only the 
merest trace of its recurrence. 
The scum which forms on the surface of many ponds and 
lakes, following a hot summer season, has been much studied 
and has been found to consist in most cases of various blue-green 
