608 .PROCEEDINGS OF THE ACADEMY OP [Sept., 



flora of the mountains may be looked upon as relatively older in point 

 of time than that occupying the territory along the sea coast. 



An interesting confirmation of this position is found in a study of 

 the succession of the floras on the Pocono Mountain plateau, following 

 the destruction of the original forest by lumber operators. The 

 original vegetation of this plateau consisted, as far as I have been able 

 to determine, of four elements, viz. : a forest of pitch pine, Pinus rigida 

 Mill., which covered the looser morainic material of the great terminal 

 moraine in the eastern and southern parts of the plateau; the broad- 

 leaved deciduous forest with its oaks and associated species on the 

 eastern slopes and edge of the tableland ; the chestnut and black locust 

 forest which occupied Laurel Ridge along the western rim of the plateau, 

 and a forest of white pine with a thicket of Rhododendron maximum L. 

 beneath, mixed in many places with the black spruce, Picea nigra Link, 

 the red maple and other plants characteristic of the Catskill mountains 

 and farther north, grading over to a hemlock forest in the region of 

 Tobyhanna. The open sphagnum bogs culminated in the presence 

 of the larch, Larix americana Michx., with which were associated 

 Kalmia glauca Ait., Ledum latifolium Ait., Rhododendron rhodora Don, 

 and other northern plants. With the destruction of the white pine, 

 hemlock and pitch pine forests, the vegetation of this tableland has 

 undergone an entire change. The succession of the species has not 

 been worked out in detail, but what has been observed is instructive. 

 The botanist is impressed by the general appearance of the landscape. 

 The flora over the eastern half of the i^lateau in aspect resembles that 

 of the pine barren regions of southern New Jersey, from which the 

 original pitch pine and Jersey pine have been cut. A study of the 

 species shows that this appearance is due to the close similarity of the 

 flora in the plant species w^hich constitute the tw^o regions. We have 

 an instructive example of mass invasion of such plants as Quercus 

 ilicifolia Wang., Pinus rigida Mill., Gaylussacia resinosa Torr. and 

 Gray, Vaccinium vacillans Solander, Epigcea repens L., Gaultheria pro- 

 cumbens L., Rhododendron viscosuni Torr., Kcdmia angustifolia L., 

 Lilium philadelphicuni L., Amianthium musccBtoxicum Gray, Lyco- 

 podium inundatum L., etc., from the morainic hills westward into the 

 region occupied by the white pines. We naturally inquire from what 

 locality the pitch pine formation has proceeded, and it seems to me we 

 are forced to conclude that this association of species has been derived, 

 not from the barrens of New Jersey, but from the nearby mountains 

 northwest of the Delaware Water Gap which, as previously mentioned, 

 support such a flora. This relict flora on the Kittatinny and other 



