74 Postelsta 
thest out in the lake working shoreward one 
meets first with a zonally arranged society of 
Myriophyllum spicatum:-This zone varies in 
width and is not continuous. Its usual depth is 
from 1-3 meters. Frequently in certain places 
of this society are found scattered plants of 
Nymphea polvse pata. 
The next zone shoreward is formed by a Po- 
tamogeton society. This is principally composed 
of Potamogeton natans and Potamogeton pusillus. 
In some of the small bays or inlets along the 
shore this zone attains a comparatively large 
width. Along projecting points on the other hand 
it frequently narrows down very much and often 
becomes discontinuous. Potamogeton natans is 
by far the largest element in this zone. 
Of a still more interrupted charactem asea 
society that shoreward succeeds the one just 
mentioned and which is built up principally of 
Nymphea polysepala. It develops typically in 
the bays or behind projecting spits of land. Asa 
a rule the plant occurs in dense patches where 
often the large heart shaped floating leaves crowd 
so close together as nearly to obscure the surface 
