134 SIXTEENTH REPORT. 



them rise to nearly 100 feet in height. Most of them are fixed, being covered 

 and held in place with trees, shrubs and herbaceous plants, but near the 

 lake, especialW at Port Franks, the dunes are still forming and being blownti 

 first one way and then another, nowhere so far as observed encroaching 

 upon good agricultural land. As the Lake Huron shore of the county runs 

 quite regularly northeast and southwest, the cjuestion naturally arises as 

 to why the dunes are so much larger at Port Franks than at other points 

 along the shore. On the west coast of Michigan it has been noticed that 

 by far the largest dunes have been formed at the mouths of rivers- and this 

 perhaps fully explains the situation at Port Franks. At this point the Aux 

 Sables River enters the lake and brings down and carries into it an immense 

 cjuantity of sand which is again washed up by waves and then blowTi up 

 into dunes. 



HABITAT DISTRIBUTION OF PLANTS. 



From the foregoing it will be seen that in a general discussion of distribu- 

 tion, the district under consideration may be divided into three fairly well 

 defined kinds of habitats, the very wet or hydrophytic, the medium wet or 

 mesophj^tic, and the very drj^ or xerophytic. 



Hydrophytic Habitats. 



These habitats are particularly interesting, altho the plants of the small 

 rivers and small driecl-up lakes do not form any considerable part of the 

 flora. On the borders of Lake St. Clair, along the several mouths of the 

 St. Clair River and on the delta islands, the bogs, coves, small bays, and 

 large areas of shallow and apparently rather stagnant water, are sufficiently 

 permanent and free from variations to encourage the growth of all plants 

 fitted to thrive under such conditions. The pondweeds {Potamogetons) 

 flourish, about 27 species or forms having been noticed and in many "places 

 on the borders of Lake St. Clair and the mouths of the St. Clair River and 

 often extending out some distance into the deeper water, the rush, Scirpus 

 ocddentalis, is so dense that it is difficult to row a small boat through it. 

 With the latter is often associated an abundance of Equisetum fluviatUe, 

 and usually nearer the shore, sometimes hoAvever in shallow water or in 

 very wet places, Scirpus validus, S. heterochaetus, Sparganium eurycarpiim 

 and Bidens beckii are abundant. In the coves and still water the pickerel- 

 weed, Najas flexilis, water shield, Xymphaea advena and Castalia tuherosa 

 are very frequent and Eleocharis quadrangulata occasional. In very wet 

 places, for at least part of the year, and often as it appears in strips, or in 

 the beds of old but now mostly discontinued streams, the common reed 

 (Phragmites communis) is abundant, and is a very striking feature of the 

 vegetation when in bloom. The renowned Indian rice Zizania palustris L., 

 and Vallisneria spiralis, known among sportsmen as wild celery, both known 

 to furnish valuable food for wild ducks, are found, the former plentiful in 

 spots, the latter common everywhere in shallow water. Another plant, 

 Sagiiaria latifolia, sometimes knowTi as swan root, the root or rootstock of 

 which is said to furnish food for ducks and swans, is verj*- common in mud 

 and shallow water. 



2"The Ecological Relations of the Vegetation on the Sand Dunes of Lake Michigan," by Henry 

 Chandler Cowles. Botanical Gazette, Vol. XXVII, Nos. 2-3-4-5, 1899. 



