THE FLORA OF MICHIGAN LAKES. 



CHARLES A. DAVIS, ALMA. 

 (Read before the Academy, December 27, 1S94.) 



With the three largest great lakes practically within her territory, with 

 a fourth lying on her border and more than 5,000 smaller lakes and ponds 

 scattered over her surface, Michigan offers exceptional opportunities for 

 the study of fresh water plants, and it is the purpose of the present paper 

 to put the facts already known relating to the flora of our lakes into such 

 shape that they will be available for future use. The lakes of the State 

 exclusive of the Great Lakes cover an area of 1,225 square miles, or more 

 than 784,000 acres, or about 1-50 of the total area of the State, and 

 they are so distributed that there is hardly a botanist in Michigan who 

 cannot readily reach one or more of them. 



The small lakes, particularly those of the Lower Peninsula, are com- 

 monly depressions in the drift, shallow and not of large extent, frequently 

 partially filled in around the margin with the remains of former genera- 

 tions of. plants, so that many of the typical features of lakes of hilly or 

 mountainous regions are partly supressed or entirely wanting. These 

 lakes belong to a recent geological time which undoubtedly accounts for 

 some of their peculiarities. By far the larger number of them exhibit 

 the following features: A small sheet of water of roughly elliptical 

 shape bordered by a marshy area of varying width, which is limited on 

 two or more sides by low. abruptly sloping, sandy or gravelly hills. The 

 marshy tract is frequently wider on the south side than on the north, and 

 its character varies from a quaking bog at the inner margin through a 

 sphagnous zone into a swamp in which the prevailing trees may be tama- 

 rack, cedar, or spruce, or all of them. The plants of the sphagnum zone 

 are characteristically those of the boreal life zone and in such lake 

 margins we find northern plants reaching their southern limits. The 

 quaking bog is usually a lake ward extension of the shore plants and is a 

 closely woven turf of the roots and rootstocks of various species of Carex, 

 Cyperus, grasses and at its outer margins, sometimes of Typha latifolium 

 and Sparganium eurycarpum, partly resting, partly floating on a bed of 

 loosely coherent vegetable debris into which the unwary investigator 

 may find himself sinking, if he is not constantly on the lookout for his 

 footing. In the larger lakes the marshy border may not extend entirely 

 around the margin, but it is usually noticeable along the southern shore 

 where it may be of considerable extent, while the rest of the shore is 

 entirely without it. Such are the lakes. 



The work which has been done in connection with the flora of these 

 bodies of water has been of a decidedly desultory and irregular sort, and 

 the published accounts of such work, meager and largely confined to 

 simple lists of the species of the Metaspermae found growing in the lakes 

 which have been visited by our collectors. Sometimes these lists are 

 accompanied by notes relating to the variations of some of the species, but 

 usually the accounts are very short. A notable exception is the work done 

 on Lake St. Clair in 1893, by the Michigan Fish Commission party under 



