Jennings : A Botanical Survey of Presque Isle. 397 



Erie, classified according to Merriam's system of life -zones/'' belongs 

 typically to the Alleghanian area of the transition zone ; the northern or 

 southern elements dominating in limited areas, the ecological conditions 

 of which approach more nearly to the boreal or austral zones res])ec- 

 tively. The escarpment at the head of Presque Isle is more than eighty 

 feet in height, and, although almost perpendicular, it is quite heavily 

 wooded. Its forest is typically a hemlock-birch formation with sec- 

 ondary species of Ostrya, red maple, beech, and Tilia. The shrubs 

 are Sambucus racemosa, Riibiis odonitiis, and Hamamelis, while the 

 herbaceous layer consists mainly of various mosses, Adiantum pedatum, 

 and Di-yopieris spinulosa. The distinct tendency of the cliff vegeta- 

 tion here is Canadian as to the trees, but Alleghanian as to the under 

 vegetation. 



As to the mainland back of the escarpment the forest is about equally 

 composed of hemlock, black and red oak, and chestnut, with consid- 

 erable Magnolia acuininata, Liriodeiidron, and Primus serotina, and 

 lesser numbers of white ash and Betula lutea. This forest, as to the 

 trees, is thus composed about equally of northern and southern (boreal 

 and austral) species, and may thus be regarded as typical Alleghanian 

 (eastern transition). The undergrowth here is typically composed of 

 Alleghanian species, but there are a i^'ii species, the ranges of which 

 extend far to the south, reaching the gulf coast or even the tropical 

 region. 



The flora of Presque Isle comprises at least 430 ferns and seed- 

 plants, and, grouping these in a general manner according to Mer- 

 riam's life-zones, there are to be distinguished three main groups as 

 follows : 



A. Species the range of which is northern, Canadian, or Alleghan- 

 ian, or extending over more or less of both areas. Total, 115 species. 



Typical representatives of this group are : 



Viola rolundifolia, Viola rafinesqiiii, 



LepargyrcBa canadensis, Arctostaphylos uva-itrsi, 



Oxycoccus macrocarpiis, Trientalis americanus, 



Alenyanthes trifoliata, Gerardia paupercula, 



Viburniwi acerifoliitm, Viburnum denfatu?n, 



^^ Merriam, C. H. " A Provisional List of Canadian Plants — The Vertebrates of 

 the Adirondack Mountain Region." Trans. Liniiaan Soc. N'. K, I: 26, Dec, 

 1882 : and " Life Zones and Crop Zones of the United .States." Div. Biol. Survey, 

 U. S. Dept. of Agriculture, Bull. 10 : 1-79, 1898. 



