THE DECIDUOUS FOBEST CLIMAX. 191 



Pellia epiphylla, Sdrpus caespitosus, Carex saxaiilis, and C. scabra. The bog- 

 like or scrub stage consists of Cassandra, Kalmia, Ledum, Myrica, Sphagnum, 

 Drosera, Sarracenia, and Pellia. It may follow the preceding, or in some 

 cases replace it. Some ponds are gradually overgrown by Sphagnum, which 

 forms a substratum on which Scheuchzeria appears, soon followed by Drosera. 

 With drier conditions Sarracenia, Vaccinium oxycoceus, and Smilacina trifolia 

 enter, followed later by Eriophorum gracile, Carex trisperma, and C. pauci- 

 flora. In the succeeding heath stage, Cassandra, Kalmia, and Ledum are 

 abundant, and are associated with Pyrus, Viburnum, Empetrum, and Vacci- 

 nium. The trees next begin to encroach, Picea nigra first, followed by Thuja 

 and Larix, and the climax forest slowly establishes itself. 



Transeau (1903 : 401) has outlined in concise form the serai relations and the 

 distribution of the dominants of the boreal hydrosere of North America: 



"Throughout the region of northern Indiana, northern Ohio, and southern 

 Michigan the problem of succession is complicated by a seeming absence of 

 all connection between the bog societies and the bordering forests. The zonal 

 succession of plant groups, from the submerged aquatics of the pond to the 

 arborescent forms of the higher bog margin, are clearly defined and well known. 

 But then comes a sudden break, and without a suggestion of gradation the 

 surrounding forest of mature oaks or oaks and hickories appears. 



" Farther north in Michigan there is no such difficulty in finding a definite 

 order of succession between the bogs and forests surroimding them. For 

 example, a tamarack swamp on north Manitou Island, which is sm-rounded by 

 a thick forest of maple and beech, shows the following societies arranged ahnost 

 zonally, beginning with the open pond in the center: 



"1. Aquatic society. — Potamogeton natans, P- lucens, Nymphaea advena, 

 Castalia odorata. 



"2. Cat-tail-Dulichium society. — Typha latifolia, Phragmites phragmites, 

 Menyanthes trifoliata, Dulichium arundinaceum, Cicuta bulbifera, Scheuchzeria 



"3. Cassandra society. — Chamaedaphne calyculaia, Dryopteris thelypteris, 

 Sphagnum sp. ?, Kalmia glauca, Sarracenia purpurea, Ledum groenlandicum, 

 Lycopus amerlcanus, Triadenum virginicwm. Polygonum hydropiper, Rubv^ 

 hispidus, Comarum palustre, Andromeda polifolia, Chiogenes hispidula, Oxycoc- 

 eus oxycoceus, and Eriophorum virginicum. 



"4. Shnib and young tree society. — Aronia arbuiifolia, Ilidoides mucronaia, 

 Rosa caroliniana. Ilex verticillata; young specimens of Larix laridna, Betula 

 pumila, Picea mariana, and Acer rubrum. Beneath these occur a scattering 

 of members of the preceding society, together with Limnorchis hyperborea, 

 Blephariglottis lacera, Gymnadeniopsis clmeUata, Osmunda regalis, 0. cinna- 

 momea, Dryopteris spinulosa intermedia, Vaccinium canadense, Epilobium 

 lineare, E. adenocaulon, and Viola blanda. 



"5. Conifer society. — This zone is composed of mature tamaracks, black 

 spruces, low birch, and swamp maples, young and mature Betula lutea and 

 Tsuga canadensis, and seedling Acer saccharum. The undergrowth of herbs 

 and shrubs is diminished to a few stragglers. This brings us to the higher 

 ground surrovmding the bog, which is occupied by the next society. 



"6. Climax forest society. — Consists of sugar maples and beech trees with 

 occasional hemlocks. The undergrowth is sparse, consisting principally of 

 their own seedlings. 



"Going farther north into Ontario, the series of societies is not so long, but 

 apparently just as definite. But we have there passed the northern limits of 

 our broad-leaved mesophytic trees and the climax stage is reached in a mixed 



