34 MICHIGAN SURVEY, 1905. 



St. Johns Wort, Joe Pye Weed, Swamp Milk Weed, Running Swamp Black- 

 berry, Marsh Cinquefoil, Ladies Tresses, Marsh Bell Flower, Creeping Snow- 

 berry, Solidago uliginosa, and a number of grasses and sedges among which 

 are Eriophorum cyperinum, Calamagrostis canadensis, Deschampsia flexusa, 

 Panicularia canadensis, Scirpus cyperinus, Carex viridula, riparia, and 

 filiformis. Owing to the low height of these forms, the habitat is open r 

 and the fauna is similar in many ways to the fauna of the mountain top, 

 but, owing to its proximity to the river, several new forms are added. The 

 more characteristic forms are the butterflies, Argynnis cybele var. (near leto\ 

 Argynnis atlantis and Basilarchia arthemis; the dragon flies, Gomphus spicatus, 

 Lestes unguiculatus, Calopteryx aequabilis and Sympetrum obtrusum, and the 

 grasshoppers, Atlanticus pachymerus, Stenobothrus curtipennis, Podisma 

 glacialis, Melanoplus islandicus and Scudderia pistillata. It might be ex- 

 pected that this habitat would be favorable for reptiles and amphibians, 

 but while it is the habitat of the Garter Snake, Thamnophis sirtalis sirtalis, 

 the dense entangled nature of the vegetation apparently excludes the frogs. 



The cassandra zone extends only to the river bank, where it generally 

 mingles with a narrow zone of alders on the low natural levees, but a number 

 of grasses and sedges, Juncus effusus, Calamagrostis canadensis, Scirpus 

 cyperinus, Dulichium arundinaceum, Carex filiformis, viridula and riparia, 

 push out on the mud flats to the edge of the water, Fig. 19, and form a transi- 

 tion society between the cassandra zone and the aquatic forms of the river. 



The fauna of these flats is also transitional between the aquatic and terres- 

 trial habitats. This is illustrated by the presence of the turtle, Chrysemys 

 marginata, and the frogs, Rana clamitans and septentrionalis , which are 

 amphibious and thus intermediate in habits between the two habitats. 

 The birds are the waders and shore birds that find their food here ; among 

 these may be mentioned the sandpipers, snipes, herons, and bitterns. Al- 

 though by no means limited to this habitat, and to be more properly listed 

 with the fauna of the mesophytic forest, the Canadian Porcupine is a 

 conspicuous form on these flats where it may often be seen, singly or in 

 groups of two or three, feeding on the pads of the water lilies. 



Owing to the steepness of the sides of the valley, the entire succession of 

 societies is only found in the broader parts, for where the river swings toward 

 the side of the valley the flood-plain is destroyed, and the cassandra, alder 

 and coniferous societies are all limited to a single narrow zone between the 

 river and the deciduous forest. 



If the different flood-plain societies be compared with the succession of 

 forms in a tamarack swamp as given by Transeau ('03, pp. 403-404) , a remark- 

 able similarity will be revealed. The societies that occur in the bogs of 

 more southern localities are here spread out over the entire flood-plain of 

 the river, and the tamarack swamps of Indiana, Illinois and southern Michigan 

 are minature reproductions of the flood-plain conditions in this region. 



Station IV. Substation 4- There are, however, areas where more typical 

 bog conditions prevail, so that in the wider parts of the valley the bog types 

 may attain a much better development. In these areas, the bog societies 

 are not arranged in concentric zones, as in the southern bogs, but are, as 

 the flood-plain societies, more or less parallel to the river. The succession 

 is much the same as on the flood-plain and in the southern bogs. The sedge 

 zone grades into a zone composed largely of Dwarf Cassandra associated 

 with the Rose, Juneberry, High Bush Blackberry, Wax Myrtle, American 

 Meadow Sweet, Swamp Honeysuckle, and Cranberry, that is in turn followed 

 by a society composed largely of Balsam Fir, Tamarack and White Spruce, 



