ECOLOGY OF NORTHERN MICHIGAN. 49 



have been introduced, and which is kept open, so that only in a few places 

 can the succession of forms be observed that would occur if the clearing 

 was left undisturbed. There is evidence, however, in several places, that 

 the pioneer forms are the Quaking and Large-toothed Aspens, and the Paper 

 and Yellow Birch. The animals taken here weie probably all forms from 

 adjacent habitats (see annotated lists). 



Station II. Washington River. This river is a sluggish meandering 

 stream flowing through a broad flat valley between the Greenstone and 

 Minong Trap Ranges, and emptying into the head of Washington Harbor. 

 The aquatic vegetation is very poor. In the quiet water near the mouth 

 of the river, Myriophyllum sp. forms the principal vegetation with Sphar- 

 ganium eurycarpum, and Phragmites communis in the shallow water near 

 shore. These forms are replaced on the mud flats by a zone of sedges and 

 herbaceous forms, among the conspicuous forms of which are Car ex tri- 

 buloidea, retrorsa, intumescens and trisperma, Juncus effusus, Joe Pye Weed, 

 Esclepias incarnata, and Spiraea salicifolia. This society is not extensive 

 but soon grades into the dense thickets of Hoary Alder (Alnus incana) that 

 are characteristic of the flood plains in this region. The undergrowth in 

 these thickets is limited to a few forms such as Caltha palustris, Skunk 

 Cabbage, Vagnera trifolia, and several species of ferns and violets. Where 

 the flood-plain is broad, as toward the mouth of the river, the alder thickets 

 are followed by a society of White and Black Spruce, Tamarack, White 

 and Yellow Birch, and Black Ash, with an undergrowth of Taxus canadensis, 

 Mountain Maple, Andromeda polyfolia, Mitella nuda, Dwarf Dogwood, 

 Coptis trifolia, Chiogenes hispidida, Ledum groenlandicum, Vaccinium cana- 

 densis, and Viburnum opulus, on a thick carpet of moss. As the valley 

 narrows toward the head of the river, this zone gradually disappears. 



As in the case of the flora, the aquatic fauna is limited both in individuals 

 and species. The birds are represented by the Pied Billed Grebe, American 

 Coot and American Merganser; the molluscs by Planorbis exacuous and 

 Physa sp. among the leaves of aquatic plants, and Pisidium variabile and 

 Pisidium spp. on the mud bottom. Among the alders are found the sparrows, 

 warblers and thrushes; the toad, Bufo americanus; the garter snakes, Tham- 

 nophis sirtalis sirtalis, and T. sirtalis parietalis, and the molluscs, Carychium 

 exile, Pisidium ahditum, Apecta kypnorum, Pyramidula striatella, Zonitoides 

 arbor ea and exigua, Vitrea binneyana and Agriolimax campestris. In the 

 tamarack and spruce forest, the birds are not so numerous, and the sparrows, 

 thrushes and warblers tend to be replaced by the Arctic Three-toed, Downy 

 and Hairy Woodpeckers, the Crossbills and the Sharp-shinned and Sparrow 

 Hawks. Among the molluscs, Pisidium dbditum, Apecta hypnorum and 

 Carychium exile also seem to drop out in this zone, but Pyramidula stria- 

 tella, Vitrea binneyana, Zonitoides arbor ea and exigua were found associated 

 with Euconulus ftdvus and E. chersinus polygyratus, Sphyradium edentidum, 

 Acanthinula harpa and Pyramidula striatella alba. Here also the grasshopper, 

 Tettix acadicus, and the spider, Amaurobius bennetti, are occasionally found 

 in the moss. 



Station VI. North Slope of Greenstone Range. On account of the 

 intermediate relation which it bears to the flood-plain of Washington river, 

 Station II, and the top of the Greenstone Ridge, Station III, this station 

 will be considered here. The Tamarack and Black Spruce are replaced 

 on the sides of the valley by a forest composed principally of the Balsam 

 Fir, White Spruce, Paper and Yellow Birch, and large isolated White Pines. 

 The undergrowth consists principally of the Ground Hemlock associated 

 7 



