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Jennings: A Botanical Survey of Presque Isle. 401 



perus heath, a distinctly northern formation. The Myrica thicket is 

 soon superseded by the Pniniis serotina forest, which in its turn 

 gives way to the Qi/ercus vclittina forest, both formations being dis- 

 tinctly southern and related to the deciduous forest. The heath stage 

 is succeeded by the Finns strohus forest, distinctly northern, but this 

 is eventually displaced by the black oak forest, distinctly southern. 



In the Dune-Thicket-Forest Succession the initial stage may be dis- 

 tinctly northern, as in the Ammophila and Pniniis piitnila dunes, or 

 more southern, as in the Popnlus and Andropogon dunes. In either 

 case these dunes may towards the southern side of the peninsula pass 

 into the Toxicodendron thicket and the Prunus serotina forest, both 

 related to the deciduous forest center, or towards the northern side 

 of the peninsula they may pass into the Arctostaphylos-Juiiiperus 

 heath and then into the Pinus strohus forest, both with northern 

 affinities. The climax forest for the succession is, however, the 

 Querciis velutina forest, this being distinctly related to the deciduous 

 forest center. 



In the Lagoon-Marsh-Thicket-Forest Succession the more hydrophi- 

 lous formations on Presque Isle consist of species of wide distribution, 

 but in the zoned formations on the banks of the lagoon or pond there 

 may be seen tendencies towards either the one or the other forest cen- 

 ter. Thus, in the first three stages of the succession a considerable 

 number of the species are northern — Triglochin palustris, Carex 

 cederi puniila, /uncus balticus, J. articulatus, J. alpimcs insignis, J. 

 nodostis, etc. 



With the growth of the outer Populus-Salix zone and the advent of 

 an inner shrub-zone around the lagoons, together with the leaving of 

 the lagoons farther inland with the onward growth of the peninsula, 

 the direct exposure to high winds becomes less and less at the same 

 time that species with southern relationships become more prominent. 

 However, the wet meadow formation, Cladium-Calaviagrostis forma- 

 tion, and its outer shrub-zones, the Myrica-Salix and Rhus-Alnus 

 formations, are quite distinctly northern, and the wet meadow may be 

 invaded and occupied by other typically northern formations, as the 

 Fragaria- Polytrichum and the Sphagnum- Oxycoccus formations. The 

 climax stages of the succession, however, are more southern than 

 northern, the final Uttnus-Acer forest belonging clearly to the decid- 

 uous forest center. 



The burn succession also apparently begins with formations belonging 



