495 
emergent vegetation, principally Scirpus, which, on account of 
its growth and structure, does not reach an advanced stage of 
decay until ice and winter floods have broken it down. With 
rising spring temperature it yields to decay and releases a great 
store of nitrogen which the phytoplankton can utilize. Both 
of these types of vegetation are rooted in the humus and allu- 
vial deposits of the lake,and both are to some degree emergent. 
They thus draw their supply of food (dissolved salts and gases) 
largely from soil waters and the air, and less from the supply 
in solution in the water of the lake. The submerged and non- 
rooting vegetation (Ceratophyllum and Elodea) is not abundant 
in Flag Lake, so that the food supply in the lake waters is not 
drawn upon to any great extent by the aquatic vegetation, and 
it thus becomes available for the phytoplankton, which, in 
turn, supports the zodplankton. The products of decay of the 
succulent and emergent vegetation, on the other hand, are in 
large part released directly into the lake waters, and at times 
(fall and spring) when the plankton reaches its greatest devel- 
opment in this region. Owing to its character and to the pro- 
tected situation of the lake the vegetation is never swept away 
by floods, nor is the lake traversed by any marked current as 
are both Thompson’s and Quiver lakes. The fertilizing effect 
of the decaying vegetation is thus more localized in this region 
than in the other bodies of water examined by us. 
The data from Flag Lake thus throw light upon the effect 
of emergent and rooted vegetation—which is typically of the 
littoral type—upon the plankton. They indicate that this kind 
of vegetation favors the development of the plankton by add- 
ing to the food materials in the water, while at the same time 
it does not to a large degree compete with the phytoplankton 
in the consumption of the food thus released by its decay. 
In 1896 a series of examinations of the local distribution 
of the plankton in Quiver, Matanzas, and Thompson’s lakes was 
made by the pumping method, and since the collections were 
made in the areas of vegetation as well as in the open water 
they might also be examined to determine, if possible, the effect 
