94 College of Forestry 
A few illustrations will suffice to define the status of this 
algal growth as related to lake filling. 
(a) At a depth of twenty-two feet in Tully Lake I have 
found heavy masses of the alga popularly called water silk 
(a species of Spirogyra, probably S. crassa). This rested 
lightly upon the ooze of the lake bottom. 
(b) At other points in this same lake, the bottom am to 
at least as great a depth as in (a) is covered by a slimy 
felt of blue-green alga (Spirulina) patches of which become 
detached by the buoyancy of gas and appear at the surface 
as the familiar (locally at least) floating “ voleanoes ” seen 
in late summer. 
(c) In shallow bays protected from strong wave action, 
filamentous green algae, notably a species of Mougeotia, 
develop so earn as to form a dense tangle among the 
anchored vascular plants. The shallow water becomes liter- 
ally blocked by this growth. During windy weather masses 
become detached and carried into deeper water as peculiar 
cloud-like objects of curiosity or are piled up along the 
shore. 
(d) Gelatinous bead-like colonies of blue-green alge 
(Rivularia) develop in great masses on the bottom of 
Oneida Lake, and in late summer are washed upon the 
beach in quantities sufficient to resemble deposits of smooth 
pebbles. Algae of this sort and other of the blue-greens de- 
velop habitually a thick beady or slimy coating on all sub- 
merged objects —notably old or dead stems of lake rush 
and Hqutsetum — which adds materially to the volume of 
debris finally laid down upon the lake bottom. 
(e) Especially noteworthy are the blue-green algze which 
in some New York lakes— notably the so-called green lakes 
of the Jamesville and Kirkville districts —are associated 
with the deposition of lime upon submerged branches of 
trees, ete. and apparently also upon lake margins. These 
masses of lime become remarkably thick — like a fall of 
soft wet snow upon twigs — and if the shore ledges are thus 
built up as seems likely, then the role of these organisms in 
