132 Wisconsin Academy of Sciences, Arts, and Letters. 
true, then the floating scum would have been frozen directly into 
the top ice. I have no means at present of determinating cer¬ 
tainly which of these two ideas is correct, but the weight of the 
long-continued observations of the above quoted authors on the 
seasonal habits of the plant inclines me to believe that the alga 
did not form a scum, but was probably present, late in the sea¬ 
son, in vast quantities in the deeper waters of the lake and that 
somehow the extreme cold of the month of January caused it 
to rise after the surface had become frozen. 
Concerning the reddish color which appears in these plants, 
particularly on their rising to the surface, or on their under¬ 
going decomposition, I wish to record here a suggestion at con¬ 
siderable variance from the theory held by Hyams and Rich¬ 
ards, who come to the conclusion that the reddish substance is 
an important factor in the vigorous growth of plants. 
These authors have themselves stated the fact that ' ‘ whenever 
the plant is found below the surface it is blue-green in color ■ ’ 
(01, p. 310), and that the reddish pigment appeared “when 
luxuriant, or whenever the growth is rapid’ 7 (04, p. 271). 
They have further said that it is the mass of filaments near the 
surface of the water, and the floating scum, and the decayed 
alga on the rocks of the shore which display the reddish or vio¬ 
let tints. 
While it may be correct, as do the two authors above cited, 
to assume the probability of the great importance of these red¬ 
dish pigments and perhaps even their chemical combination 
with the chlorophyll of these plants, it is hardly allowable, in 
my opinion, to bring in, to assist in establishing their point of 
the great importance of these substances, comparisons with the 
other reddish coloring matters sometimes present in the cell-sap 
of the young shoots and leaves of higher plants. For, I think 
that it is not at all established that these reddish pigments of 
the higher and lower plants are similar to each other, either 
chemically or physiologically. 
The appearance, in the case of Osciliatoria prolifica as well 
as in other common species of Osciliatoria, of the reddish coloring 
matters in the filaments after they have risen to the surface and 
particularly on their undergoing evident decomposition, suggests 
that such colors arise as decomposition products, rather than that 
