MICHIGAN ACADEMY OF SCIENCE. 
G7 
in Plate 14.), Mitella nuclei, Coptis trifolia , Mitchella repens, Viola 
blanda, and Phegopteris dryopteris. Others which are not so typical 
occur in openings where sufficient light is admitted to the ground: 
Rubus triflorus, Linnaea borealis americana , Arabia nudicaulis and 
Cypripedium hirsutum. 
In normal genetic succession this association follows the Larix asso- 
ciation quite closely. It may however, follow Chamaedaphne without 
an intervening Larix stage as is the case in the bog southeast of south 
Fishtail Bay. It is the climatic association for the boggy ground and 
as long as the ground remains in this condition no other association 
can replace it. It is separated from the aspen or the hardwood asso- 
ciations, when in juxtaposition with them, by clear-cut tension lines, in 
the making of which the water-table height seems to be the most potent 
single factor, as obvious variations of that factor at times in the near 
past have found their expression in inroads of one association into the 
other and their persistence there as relics. From the Picea-Abies asso- 
ciation there is no such well-markt tension line, but as there is only a 
single example of the Picea-Abics association it is difficult to give ade- 
quate separation from the data at hand. One obvious difference, how- 
ever, is that the Picea-Abies has developt in land which is drained by 
the little streams which run thru it fairly rapidly, while the cedar bog 
land is drained very slowly if at all except by seepage. In this region 
the Picea-Abies is the logical association to succeed the cedar bog but 
headway in that direction is virtually nil. 
Incursions of fire and lumbering are rather readily replaced by cedar 
bog species without intervening stages. In case of severe burns, how- 
ever, there is a flreweed stage and not infrequently a tamarack stage, 
both of which are past thru rather rapidly and the cedar again becomes 
dominant. Only rarely is there more than an indication of an aspen 
stage, for in wet ground the aspens cannot do so well as the bog trees 
and the aspens that may have started soon succumb to the cedar, which 
verv easilv invades such areas. 
List of the Species of the Thuja occidentals Association: 
DOMINANT SPECIES. 
Thuja occidentals. 
Acer rubrum. 
Fraxinus nigra. 
( Pinus strobus .) 
( Picea can adensis . ) 
Picea nicer iana. 
Larix laricinci. 
Abies balsamea, 
SECONDARY SPECIES. 
Clintonia borealis. 
L e d.i cm gro e n landi ci cm. 
Taxus canadensis. 
Chiogenes hispidula. 
Strcptopus amplexifoli ns. 
Moneses uniflora. 
Acer s pica turn. 
Pyrola secunda. 
Pyrola asarifolia. 
Mitella, nuda. 
Coptis trifolia . 
N m i lacina trifo lia. 
' Trientalis am crican a. 
Drosera rotundifolia. 
Prunella vulgaris. 
Viola reniformis. 
Phegi.ptcris dryopteris. 
A splenium filix-foemina. 
