126 SEVENTH REPORT. 



PLANT DISTRIBUTION IN A SMALL BOG/ 



EDITH E. PETTEE. 



The bog studied is about four miles southeast of Ann Arbor, Mich., in 

 one of the many morainal depressions of that region. It is about thirty- 

 nine rods long and seventeen rods wide, and is surrounded by steep banks 

 which are forty feet high at the west end, sloping down on both sides 

 to within three feet of the swamp level at the east end. On the north 

 side there is a depression in the hillside, and a consequent widening of 

 the swamp at that point of at least fifty feet. The area drained is very 

 narrow on all sides and there is no definite channel draining into the 

 swamp. 



The bog is undrained except for excess of water, which is taken off in 

 times of flood by a shallow ditch at the east end. The surface of the 

 swamp is nearly level and there is no evidence of its ever having stood at 

 a higher level than at present. 



The underlying soil is heavy blue clay. Borings show a slope of the 

 bottom on all sides toward the center, as indicated in the diagram. The 

 dotted lines show estimated depths which have yet to be determined. 



The hills around the bog seem to have been covered by an oak-hickory 

 forest which has all been destroyed except on the high west hill and its 

 east facing slope. On the top of the hill are found : — 



Quercus rubra, Quercus velutina, Quercus alba, Hicoria ovata, Hicoria alba, Acer saccharinum.^ 



There is no underbrush and few herbs except grass. 



On the east facing slope we find 



Quercus rubra, Quercus velutina, Quercus alba, Hicoria ovata, Hicoria minima, Hicoria alba, Jug- 

 lans nigra, Prunus sp . (cherry), Juniperus communis, Prunus Americana, Rubus occidentalis. 



Rubus nigrobaccus, Hamamelis Virginiana, Crategus 2sp., Corylus Americana, Cornus stolonifera, 

 Rosa Carolina, Galium sp., Vagnera racemosa, Celastrous scandens, Vicia sp., Dioscorea villosa, Parthen- 

 ocissus quinquefolia, Thalictrum dioicum, Asclepias Syriaca, Linaria Linaria, Falcata comosa. Podo- 

 phyllum peltatum, Pyrola elliptica, Impatieus biflora Geranium maculatum, Cnicus Lanceolatus, 



The south bank is occupied by a second growth of young trees and shrubs. We find 



here: 



Quercus rubra, Quercus velutina, Quercus alba, Quercus coccinea. Hicoria alba, Hicoria ovata, 

 Rubus occidentalis, Rubus nigrobaccus, Populus grandidentata, Populus tremuloides, Carpinus Carol- 

 iniana, Hamamelis Virginiana, Corylus Americana, Aronia arbutifolia, Acer saccharinum, Crategus 

 (several species), Vaccinium vacilla'ns, Rhus glabra, Vitis sp., Smilax sp., Hepatica Hepatica, Anten- 

 naria plantaginifolia, Mitchella repens, Penstemon sp., Rudbeckia hirta. Achillea Millefolium, Viola 

 pubescens, Mitella diphylla, Vicia sp., Carex sp., Thalictrum dioicum, Polytrichum commune. Prunella 

 vulgaris. Aster corditolius, Prunus sp. 



On the north side there is a cultivateded field with patches of this young-tree-and- 

 shrub zone fringing the swamp as shown by the presence of 

 Hamamelis Virginiana, Corylus Americana, Prunus, etc. 



The bog proper is divided into three very distinct regions: — 



1. A Marginal zone. 2. An intermediate zone. 3. A central area. 



The marginal zone averages about twenty-five feet wide and has a distinctly different 

 vegetation from the rest of the swamp. Ten of the thirteen plants given by Transeau^ as 

 typical of drained swamps are found here. The ones not foimd are 



Scirpus lacustris, Polygonum emersum and Fraxinus Americana. 



1 This work was done in the summer of 1904 under the direction and with the assistance of Dr. G. P . 

 Burns. 



2The names used are those of Britton's Manual of the Northern States and Canada, 1901. 



^Transeau, E. N. On the Geographic Distribution and Ecological Relations of the Bog Plant So- 

 cieties of Northern North America. — Botanical Gazette, December, 1903. 



