218 
FIFTEENTH REPORT. 
THE FLOWERING 
PLANTS, FERNS AND THEIR ALLIES 
MACKINAC ISLAND.* 
OF 
BY C. K. DODGE 
INTRODUCTION. 
Mackinac Island is situated near the northern end of Lake Huron, in 
the Straits of Mackinac. It is about 3 miles from the shore of the 
northern peninsula and 7 or 8 miles from the shore of the southern pen- 
insula. It is one of the historical places in Michigan, as it was visited 
by most of the early voyageurs and was the site of a federal fort from 
1780 until ceded by the federal government to the State of Michigan, 
in 1895, for a park. It is now under the control of a state commission, 
and about one-half is used for park purposes, the other half being- 
privately owned. 
Little work has been done upon the fauna and flora of the island. A 
few species of plants have been recorded by travelers, but no attempt 
has apparently been made to list the flora as a whole. In the summer 
of 1912, the writer visited the island in the course of his work upon the 
flora of the east coast of Michigan, for the Michigan Geological and 
Biological Survey, and made as careful study of the plants as time per- 
mitted. Five days were spent on the island, from June 30 to July 2 in- 
clusive, and Sept. 30 and Oct. 1, 1912. 
TOPOGRAPHY. 
The island is roughly quadrangular in shape, about 3 miles long in a 
north and south direction and 2 miles wide, and contains 2221 acres. 
Generally speaking the land rises from the beach to a high rocky area 
in the center that is much broken up by ravines. The highest point is 
317 feet above the lake. Around most of the island the cliffs rise abruptly 
from a narrow beach; but on the north side the elevation is not abrupt 
and on the south side a succession of terraces leads from the bay to 
the bluff. 
The underlying rock is limestone, which is in general covered by a 
thin layer of morainic material. One small area near the northwest 
shore is covered with a considerable deposit of morainic material, and 
the terraces at the south end are made up of recent lake deposits. 
PRESENT PLANT COVERING. 
Notwithstanding the long inhabitation of the island, Mackinac Island 
is still in a quite primitive condition as far as the flora is concerned. 
The original forests still remain substantially intact, except on the 
northern part where most of the large timber has been removed and a 
few pieces of land cleared and cultivated. In the dense forests of the 
•Published with the permission of Alexander G. Ruthven, Chief Naturalist, Michigan 
Geological and Biological Survey. 
