402 Part IV. Chapter 2. 
Sphagnum atolls are formed by an increase in the size of a lake which had an Ka central 
lagoon of water fringed by vegetation. This ring of vegetation is detached and forms atolls oceu- 
pying the center of the enlarged pond. The plants established on one of these en according 
to Mac MirLAn®), who has studied them, are Scheuchzeria palustris, Carex tenuiflora, Carex 
tenella, Carex intumescens, Eriophorum polystachyum and gracile, Pogonia ophioglossoides, Calo- 
pogon pulchellus, Lyonia nsindasihe); Kalmia glauca, Andromeda, V. Oxycoccus, Menyanthes 
trifoliata, Sarracenia purpurea. The arrangement of species in the atoll was such that Menyanthes 
occupied the outer and inner edges, Kalmia occupied five distinet patches, while Sarracenia and 
Eriophorum sought the firmer substratum in the center. The other plants were sparingly represented. 
Floating bogs are also occasionally met with in the lakes of the Interlacustrine Area an 
' times when stationary they constitute the anchored bogs, which subjected to a new environment 
become modified in consequence. Morasses develop from attached bogs when these occur in 
sheltered bays or coves. Two types of morasses are distinguished, wet and dry, and the association 
of species gives name to the re such as Menyanthes morass, Utricularia morass, Salix 
morass etc.2). 
TRANSEAU?°) has studied in a painstaking manner the bog associations of 
the Huron River Valley, and his description in general will apply to the bog 
areas, as found at Mud Lake and other localities in Michigan, as described by 
C. A. CooRKE*) in a detailed manner, while discussing the distribution and origin 
of the peaty deposits throughout the state. — The first circumarea recognized 
by him next to the open water of the glacial lakes is the bog sedge cir- 
cumarea (or association). 
Here occur such dominant plants as Carex filiformis, C. oligosperma, Eleocharis palustris 
var. glaucescens, Eriophorum polystachyum while as secondary species occur Nephrodium thelypteris, 
noclea sensibilis, Juncus effusus, J. canadensis, Potentilla palustris, Salix myrtilloides, Dulichium 
spathaceum, Equisetum limosum, Bidens trichosperma var. tenuilo ee men Viola blanda 
and Eriophorum virginicum, Here and there a among the sedges occur the forerunners of the shrub 
association. The rootstocks of Lyonia or Cassandra calyculata ee up shoots and prepare the 
way for other plants. The bog near Oxford is without a central lagoon but it is occupied by 
the bog-sedge association where Carex oligosperma and Scheuchzeria palustris oceur. 
The bog-shrub circumarea in West Lake consists of Carex filiformis 
(most abundant), Nephrodium, Eriophorum, Menyanthes, Potentilla, with ‘Zleo- 
charis palustris, Sagütaria latifolia, Carex teretiuscula, Salix myrtilloides, . 2 
candida, Betula glandulosa, Vaccinium macrocarpon and Andromeda polifolta. 
This circumarea about First Sister Lake is more irregular. Zyonza calyculata 
with the bog mosses Sphagnum cymbifolium, S. subsecundum and 5. recurvum 
are in intimate association and occupy the area. | 
The associated an are the moss Aulacomnium palustre and such herbs as Drosera rotun- 
difolia, Arethusa bulbosa, Habenaria lacera, Sarracenia purpurea, Pogonia ophioglossoides, Calo- 
pogon pulchellus, Viola blanda, Osmunda regalis, Campanula aparinoides, Scutellaria galerieulata 
1) MACMILLAN, Conway: Sphagnum Atolls in central Minnesota. Minnesota Botanical Studies 
Bulletin 9, Part I: 13. 
Compare MAcMILLAN, Conway: Observations on the Distribution of Plants u Se 
at Las of the Woods. Binapustu Botanical Studies Bulletin 9, Parts X and XI: 949 
3) TRANSEAU, EDGAR N.: The Bogs and bog Flora of the Huron River Valley. at 
Gazette XL: 351, 418—448. 1905; XLI: 17—42. 1906. 
4) Report we Board of Geological Survey of Michigan 1906: 105—395- 
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