Lake Distriet: Interlacustrine Area. 393 
racterized by the predominance of certain northern types and the absence or 
rarity of trees more freqwent farther south. An uninterrupted forest extended 
from Michigan through Wisconsin into Minnesota. 
The forest formations inNorthern Michigan, according to C. A. Davis?) are (l) the Deei- 
duous Forest ZPRRNON which covered the better class of well-drained uplands, eg the 
rock hills e dominant 2. were Acer saccharum, Ulmus, Tilia, Fagus, in the s ‚ Betula 
utea, B. PR in the north, with m or less mixture of conifers, especially Tsuga, ra Picea 
alba and Pinus strobus. eE The onfeinie Forest Formation (Swamp Tree-Facies) which covered 
all of the undrained, or poorly drained flat lands, including the peat bogs and comprised Larix 
americana, Picea nigra and Thuja occidentalis with the occasional admixture of Pinus strobus, 
se Picea alba, Fraxinus sambucifolia, ar and Acer rubrum. (3) The ee Sag 
m-Facies was found on well drained flat lands and upon gentle slopes o e sides of th 
ll It had as ee constant constituents Betula populifolia, B. Iutea, A le 
(4) The White Pine-Facies was the type of forest in which Pinus strobus was dominant and confined 
to relatively small and disconnected areas of gravelly deposits and to partially covered rock 
outerops. In open stands oecur Pinus resinosa and P. Banksiana associated with Quercus coceinea 
and Acer rubrum 
Along the southern and southwestern border this forest merged into oak 
and jack pine “openings”, and in places gave way to regular prairies: Mixed 
Forest Formation?). It is a mixed forest of Pinus strobus and hardwoods 
on all loram and clay lands, while the pineries on sand and loamy sand con- 
sisted of a mixture of Pinus strobus and P. resinosa. To the east and north 
of a line extending approximately from Lake Superior east to Green Bay the 
hemlock stands associated with the pines and hardwoods on all gravelly clay 
and loam soils. Ozercus rubra is scattered through the forest and the absence 
of Ouercus alba is noteworthy. South of this line however Ouercus alba becomes 
abundant. Two kinds of forests may, therefore, be distinguished: the coniferous 
forest and the deciduous forest represented by the Acer-Fagus-Tsuga-facies. 
The undergrowth in the dense shade in the latter forest is scanty consisting of 
Taxus canadensis, Mitchella repens. 
The basin of the Red River of the North represents the western or north- 
western limit of many species of trees which constitute a large part of the 
eastern forests. It may be considered to be the western boundary of the 
Interlacustrine Area. 
Among the trees which here reach their limit are Tilia americana, Acer saccharum, Acer 
rubrum, Juglans einerea, Quercus alba, Q. macrocarpa, Q. tinctoria, Ostrya virginiana, Carpinus 
caroliniana, Betula lutea, Populus grandidentata, Pinus strobus, P. resinosa, Thuja occidentalis, 
Juniperus virginiana, Fraxinus americana, F. pubes en ie „sambueioi, Ulmus fulva, U. racemosa. 
s of far northern range “id in this d t their southern or southwestern limit: 
w specie 
Pinus Banksiana, Picea alba, Abies balsamea, Tsuga Ga Popälns balsamifera. 
Some of the eastern shrubs which make the undergrowth of the forests here attain their 
western limits: Vaccinium pennsylvanicum, V. corymbosum, Dirca palustris, Comptonia asplenifolia, 
ı) Report State Board of Geological Survey of Michigan. 1906: 191 
2) Ayres, H.B.: Timber Conditions of the Pine Regions of Minnesota. 2ıst Report U. S. 
Geographical Survey Part V: 
