tg1t] BURNS—HURON RIVER VALLEY 107 
color, Cornus stolonifera, Ilex verticillata, Rubus idaeus var. acu- 
leatissimus, R. hispidus, R. villosus, Rosa carolina, Vitis vulpina, 
Alisma Plantago-aquatica, Acalypha virginica, Agrostis alba, Bidens 
cernua, Cicuta bulbifera, Carex vulpinoidea, C. scoparia, Eleocharis 
tenuis, Eupatorium perfoliatum, Geum strictum, Glyceria nervata, 
Juncus effusus, Lycopus americanus, L. virginicus, Lactuca cana- 
densis, Ludvigia palustris, Pilea pumila, Polygonum Hydropiper, 
Fic. 1.—First Sister Lake near Ann Arbor, Mich.; the photograph shows the 
zonal arrangement of plants at the southwest corner; five zones can be distinguished 
as follows: water lily, bog sedge, bog shrub, tamarack, maple-poplar; the adjacent 
uplands are covered with oak-hickory woods; photograph by STEELE. 
P. sagittatum, Penthorum sedoides, Ranunculus pennsylvanicus, 
R. scleratus, R. delphinifolius, etc. (fig. 1). 
A study of the partial lists given above shows that they are 
not all xerophytes. There are at most only three. zones which 
have bog flora as the characteristic plants. These are the floating 
sedge, the bog shrub, and the tamarack zones. In the first of 
these only those plants rooting deep in the mat can be called bog 
xerophytes; those rooting in the surface layers are hydrophytes. 
The other zones are occupied by hydrophytes or mesophytes. 
