Atlantic Pine barren Flora. 221 
of the mountains is an endemic one showing relict endemism, representing a 
survival of a pine barren flora which was extensively represented in Atlantic 
North America as a plain flora occupying the situations controlled by the same 
edaphic conditions. During the elevations of the coastal plain, it spread its 
boundaries over the newly raised land and on to the more level mountain 
summits, but during a subsequent depression (Pensauken submergence) it was 
again destroyed on the coastal plain or circumscribed in its distribution to similar 
edaphic situations in the mountains where it persisted during the glacial period. 
With the post-Pensauken uplift the New Jersey coastal plain was again tenanted 
by pine barren plants, which after the retreat of the great continental ice sheet 
migrated to Staten and Long islands. 
This peculiar pine-barren assemblage of species‘) of the mountain 
floras of northeastern Pennsylvania and northern New Jersey forms an element 
in the flora of the Pocono plateau 2000 feet above sea level in Monroe County, 
Pennsylvania. The original vegetation of this plateau consisted of five elements, 
viz., the pine barren association of plants, consisting of a forest of pitch pine 
(Pinus rigida) with associated species which entered the region at the close 
of the glacial period and occupied the looser sand and boulder material of 
the slopes and sides of the great terminal moraine having been derived from 
the pine barren elements of the mountains previously described; following 2, the 
deciduous forest of oaks, ashes, tulip poplar and associates, which moved up 
the river valleys and clothed the slopes of the mountains and edges of the 
tableland; 3, the chestnut and black locust forest, which moved up the valleys 
from the Susquehanna River to Laurel Ridge; 4, a forest consisting of white 
pine, black spruce and hemlock, which migrated into the region along the 
crest and in the upper mountain stream valleys from the main Appalachian 
system, comprising that association of species found in the mountains of Vir- 
ginia and southward at an elevation of three thousand feet and over. 5, the 
sphagnum-bog flora, as a relict flora, when more glacial conditions prevailed. 
In these bogs are preserved many glacial plants such as Ledum latifolium 
(= L. groenlandicum), Scheuchzeria palustris, Rhododendron Rhodora, Kalınıa 
glauca, etc. With the destruction of the original forest consisting of species 
disposed in general, as above, the pine barren element consisting of Quercus 
ilicifolia (= Q. nana), Pinus rigida, Gaylussacia resinosa, Vaccinium vacıllans, 
Epigaea repens, Gaultheria procumbens, Rhododendron viscosum, Kalmia angu- 
stifolia, Amianthium (Chrosperma) muscaetoxicum, Lycopodium inundatum, seems 
to be spreading by mass invasion to the white pine lands made sterile by the 
action of the forest fires, so that if no precaution is taken the whole of the 
Pocono tableland will be covered with a worthless scrub of Comptonia asplent- 
folia, Pieris (Pteridium) aguilina, Ouercus ilicifolia (= O. nana) representing 
the pine barren associations of species”). 
i) That is an “Association of Species” or “species-guild” in a phytogeographie sense. 
2) HARSHBERGER, J. W.: The comparative Age of the different floristice Elements of eastern 
North America. Proceedings Academy Natural Sciences of Philadelphia 1904: 601—615. 
