Olive—Occurrence of Oscillatoria Prolifica, 123 
other cakes showed ten inches or so of clear top, with the red¬ 
dish substance frozen into the ice only below the ten inches. 
The great abundance of the alga is further proved by the 
large masses which were left floating on the surface of the lake, 
in March last, where the ice had melted. Mr. Hansen, who col¬ 
lected for the purposes of identification an abundance of the 
alga on March 25, 1905, says that some of the floating masses 
were about 12 inches in diameter, while others were small —■ 1 the 
greater part of them being about the size of an oak leaf” (from 
letter of April 8th to Prof. Birge;. Mr. Hansen and many 
others mentioned the peculiar smell readily noticable at the 
lake shore, which came from the decaying plant. One described 
the odor as resembling that from decayed flesh; but Hyarns and 
and Richards describe it rather as fetid, not putrefactive. 
An old resident claimed that at intervals during the past 
twenty years this red color had appeared in the ice taken from 
Pine Lake. Another said that the ice at North Lake, which is 
situated only a short distance north of Pine Lake, was colored 
two or three years ago in this same way. Some ventured the 
explanation that the fact that Pine Lake has practically no out¬ 
let except at high water, might explain the abundance of the 
alga here, as w r ell as its present confinement to this lake. For, 
a visit to ice-houses at North and Okauchee Lakes failed to dis¬ 
cover any signs of the growth, and careful inquiries at Mouse 
and Oconomowoc Lakes and Lac la Belle showed that none was 
present, at least, in the ice harvested from these bodies of water 
last winter. It is perhaps a significant fact that all of these 
lakes mentioned have strongly flowing outlets and inlets, ex¬ 
cepting Pine Lake and the neighboring Beaver Lake, so that 
it may well be that this lack may assist in explaining the abund¬ 
ance of the plant in Pine Lake during the past season. 
I have had opportunity to examine the plankton of Pine Lake 
collected on three days only—on Aug. 23, and Oct. 18, 1900, and 
again on July 26, 1905. The first collections were taken from 
waters 8—20 meters deep, but only a few blue-green forms were 
here found, and among them no Oscillatoria. 
The more recent material was taken from the surface of both 
shallow and deep waters, and from various parts of the lake; 
9 
