PLANTS OF WESTERN LAKE ERIE. 
67 
a moderate growth of Vallisneria and Idotamog etov , mostly 1*. perfoltaMus and I*, 
jjectinatus. The water is very muddy, and this may account for the scarcity of 
vegetation; for near the shore, where the water is clear, plants are more abundant, 
such bottom forms as Ohara , Nitella , and Naias, as well as Potamogetons , being 
present. 1 In the clear water also were floating great masses of a species of Mesocarpus 
swarming with Crustacea and other minute forms of animal life, while in some quiet 
places Ilydrodictyon was found. Lower Sandusky Bay averages 10 to 12 feet deep, 
and no plants were found except scattered clumps of Potamogeton pectinahus and 
P. perfoliatus. The parts of the bay above and east of the city were but hastily 
examined. For the most part there is a scanty growth of Potamogeton lonchites, 
P. perfoliatm , P. peetinatm , P. prwlongns , and P. zizii. In some places the water 
is clear, and one sees on the bottom, at a depth of 5 to 8 feet, Potamogeton ampli- 
folius and P. lucens and the straight, slender shoots of P. roUbinsii, as well as most 
of the other species native to these waters. Here Eleocharis palustris vigens grows 
just beyond Scirpus pungens, its stem below the water line covered with colonies of 
Pividaria. 
ESTABLISHING ZONES. 
It is clear that such a grouping of plants into zones as was established by 
Magnin 2 for the lakes of the Jura and by myself for Lake St. Clair is impossible 
for any region examined in 1898. Only two groups are possible — one including all 
submersed forms and those with floating leaves, the other all the remaining species 
with emersed leaves and growing with roots and parts of the stem in water. All 
the species of the three submersed and floating zones arc either mixed together in a 
narrow border along the channels or cover the entire bottom of shallow harbors. 
Among the swamp plants it is sometimes possible to draw a more or less definite line 
between the landward forms and those growing in deeper water, but even this is so 
often vague and unsatisfactory that I do not consider it of any real value. The 
species intermingle so much on common ground that an attempt to separate them 
would only result in confusion. 
INFLUENCE OF VARIATION OF DEPTH OF WATER ON PLANTS. 
The influence of changes in the depth of water on the distribution of aquatics is 
important, but unfortunately we have little data on this subject. Through the kind- 
ness of Col. James Smith, of the engineer’s office in Cleveland, Ohio, I secured a 
table showing the depths of water at Cleveland from 1859 to June, 1898. From the 
table it appears that since the records began the greatest difference in water level has 
been 2.86 feet between high water in 1859 and low water in 1895. In L859 the water 
was nearly 1.5 feet higher than it was during the summer of 1898. This must have 
made a great increase in the extent of the swamp, especially of those portions in 
which the submersed forms could flourish. In 1895, however, the water suddenly 
fell from 0.4 foot below mean in 1894 to 1.39 feet below in 1895, causing a decrease 
in the submerged area and the destruction of a great deal of submersed vegetation. 
In the following year the water rose 0.64 foot and has continued to rise slowly 
!This may also be connected with the character of the bottom. In the first locality the bottom contains a much 
larger percentage of clay than in the second. 
-Magnin, M. Ant. Recherches sur la Vegetation des Lacs du Jura. Revue Gen. de Bot., t. V (1893), p. 303. 
