94 



OUTLINE OF PLANT GEOGRAPHY 



the small streams emptying into it. The marshes have a rich and 

 very interesting vegetation. Great beds of rushes (Scirpus) and 

 cat-tails (Typha), and many species of sedges and grasses, among 

 the latter the wild rice (Zizania aquatica) which in the late summer 

 is very conspicuous with its graceful plumes. The open spaces of 

 the marsh harbor a rich assortment of algae, stone-worts (Cha- 

 raceae), and many pond weeds (Potomogeton, Vallisneria, Elodea, 



Fig. 19.— Small glacial lake, Cheboygan County, Michigan. Photo., Dr. F. C. Gates. 



etc.), while beds of white and yellow water-lilies, and occasionally 

 the great yellow lotus (Nelumbo), cover the surface of the water 

 with their big leaves and showy flowers; and white arrow-head 

 (Sagittaria) and blue pickerel-weed (Pontederia), abound about 

 the margins of the shallow water. 



Many showy herbaceous plants and shrubs grow around the 

 edge of the marsh and advancing from year to year on the soil 

 built up by the silt and their own decaying tissues, sometimes 

 extend the land into the marsh with surprising rapidity. Elder, 

 willows, button bush (Cephalanthus), wild roses, are among the 

 common members of this community, and with these are such 

 herbaceous plants, as the pink milkweed, purple Eupatorium, 

 loosestrife (Lythrum), horse mint (Monarda), asters, golden-rods, 

 thistles and many others. 



