154 OHIO STATE ACADEMY OF SCIENCE. 
It extends in typical places from a depth of 5 feet on the outer 
side, where it is bounded by water-lilies, to a depth of 10 feet or 
more on the inner side. At the north end where conditions are 
ideal the zone is 15 feet wide between the 5 and 1o-feet limits. 
On the west side it is 20 feet between these limits. Beyond the 
1o-feet limit the depth increases very rapidly. ‘The water of the 
lake is considerably colored, which must have an important effect 
on the submerged vegetation. All the plants in this zone have 
slender, wand-like stems with narrow and slender or much dis- 
sected leaves or branches. They are all highly specialized and 
thoroughly adapted to their habitat. They appear to occupy the 
ground because no other plants are able to follow. On the outer 
side they are pushed back by the water-lilies as far as these are 
able to invade the water. The typical plants are : 
Potamogeton zosteraefolius Schum. 
os lucens L,. 
Ceratophyllum demersum L,. 
Myriophyllum sp. 
Chara sp, 
Other species are : 
Potamogeton foliosus Raf. 
ne pectinatus L. 
Naias flexilis (Willd.) R. & S. 
Zannichellia palustris L. 
On the surface are frequently found the free-floating duck- 
weeds : 
Spirodela polyrhiza (I,.) Schl. 
Lemna minor Ll. 
Wolffia columbiana Karst. 
2. WATER-LILY ZONE. This isa Nymphaea-Castalia zone, 
the two plants that give character to the society being Nymphaea 
advena Soland. and Castalia odorata (Dryand) W. & W. It is 
said that the Castalia was introduced artificially, but it is now 
well established. At the north end the zone is 4o feet wide and 
extends from water five feet deep to two feet deep. On the west 
side it is 28 feet wide. This is a very striking zune on account 
of the large, upright leaves of Nymphaea. ‘The comparative 
absence of Nymphaea in water shallower than two feet must be 
accounted for on the grounds of a severe struggle with the plants 
