62 The American Naturalist. [January, 
When Lake Erie subsided after the melting of the glacier, and Mar- 
blehead emerged from the water, it was left bald, so to speak, for what- 
ever deposit the glacier may have left upon it was washed off from 
most of it by the lake. The same was true of portions of Kelley’s Island 
and Put-in-Bay, and here, where one would expect to find a moist 
climate, the scant soil formed by disintegration of the limestone becomes 
more parched under the summer sun than any spot in Ohio farther — 
east. I doubtif another place could be found in the country as far east 
where there are so many plants that belong to the western plains ason 
Marblehead. 4 
Having shown that the conditions of climate and soil near the south- 
western extremity of Lake Erie are peculiarly suited to southern and — 
western plants, it remains to indicate briefly how the seed succeeded in 
getting so many miles away from home, though the problem is no more 
difficult than accounting for the dispersal of any rare plant that is found 
only at widely separated stations. The seeds of the Composite, which 
` are the best represented of all, might many of them have come on the 
wings of the wind, and so with Asclepias and others. The seeds 
Ammania coccinea and Rotala ramosior may have stuck to the feet of a 
eS 
by cattle, which, before the time of railroads, were driven from Illinois | 
east by way of Marblehead and Cedar Point, being made to swim across 
the channel that connects Sandusky Bay with the lake. At an earlier 
day, when the bison roamed as far east as Lake Erie, seeds of various 
kinds must have clung to its hair. Others, probably came with the- 
Indians, who seem to have been attracted by the good fishing in this 
region. Few, if any, are such as have fruit whose seeds are dropped 
by birds. Fruit-eating birds in migrating would carry northward only 
those whose fruit survives the winter. 
Following is a list of plants which, on the south shore of Lake Erie, 1 
believe occur farther north than anywhere else in this part of the coun- 
try. Some of them in the west, where the summer isotherms bend to 
the north, extend to southern Minnesota. As a number of these arè 
both southern and western in distribution, I include in the same 
some that appear to reach their eastern limit near Sandusky. Onl 
a few of either the southern or western species extend east along the 
lake as far as Cleveland. Quite a number, I believe, have not hitherto 
been recorded as occurring as far north by one hundred and fifty miles, 
or so far east by a still greater distance. 
