Northern Appalachian District. 481 
Pinus rigida Facies. One other formation probably exists, a displayed on 
the ledges at Kaaterskill overlooking the Hudson Valley, namely, that in which 
the pitch pine, Pinus rigida is the principal tree. As a tree this species Oc- 
cupies the higher mountains in Pennsylvania where it exists in barren soil and 
under xerophytic conditions. A number of ericaceous plants forms a part of 
this association, as well, as the barren places, viz. Vaccinium canadense, 
V. pennsylvanicum, V. vacıllans, V. nigrum, V. stamineum, with such herbs 
as Solidago odora, S. puberula, Kalmia angustifolia, Habenaria blephariglottis, 
Lygodium palmatum, representative pine barren elements. 
Other pines form an important element in the forest cover of very exposed, 
bare, rocky, southern slopes in western Maryland. Pinus virginiana (= P. inops) 
form a dense cover in the poorest shaly soils on the lower southern slopes of 
high ridges, or more’ frequently on the south side of low hills (Pinus vir- 
giniana Facies). At higher elevations comprising the middle benches and 
summits of mountains Pinus rigida and Pinus pungens occupy sterile rocky 
situations on southern, southeastern and southwestern exposures. Scattered 
individuals also occur minglad with hardwoods on the low shaly hill tops ad- 
jacent to the mountains. Pinus mitis is present in exceptional instances. 
The Rocky Ledge Formation is found on the rocky ene and bluffs which occeur 
throughout the Catskill Mountains. The plants which characterize such 1 edges are mainly ferns!) 
and a few herbs which together may be enumerated here, as: amptosorus rhizophyllus, Pelnes 
er, Woodsia ilvensis, Saxifraga virginiana, Arabis lyrata, Polypodium vulgare, Asplenium 
chomanes, Aquilegia canadensis, Heuchera americana, Polygonum cilinode, Campanula rotundifolia 
various species of lichens as of the genus Umbilicarie and blue green algae, Nostoc sp. 
3. Pond- and Lake plant Formations. 
The lake plant and the marsh plant formations are sparingly represented 
in the Catskills. One natural lake, or mountain tarn, was noted as the 
source of Stony Clove Creek already partially encroached upon by vegetation 
to produce a marsh. In the absence of a detailed study, these formations are 
merely mentioned to complete our classification of the principal formations in 
the Catskill Mountains. 
In West Virginia above the great terminal moraine exist a considerable 
number of ponds and lakes which represent water filled kettle holes or streams 
damned by glacial material. In these ponds Nymphaea odorata, Nuphar ad- 
venum, N. Kalmianum, species of Potamogeton represent the floating aquatic 
vegetation. Calla palustris, Dulichium spathaceum, Sarracenia purpurea, Dro- 
sera rotundıfolia and D. intermedia sometimes form floating masses detached 
from the edge of the pond. The open water is surrounded by a fringe of 
sedges (Carer etc.) and Sarracenia, and these plants in turn by Zyonia 
(Chamaedaphne) calyculata, into which Larix americana encroaches with occa- 
sional EPDCINERS of pine Pinus rigida. 
ı) PovsEr, W. A.: The Fern Flora of Pennsylvania. The Fern Bulletin XVII: 65. July 1909. 
Harshberger, Survey N.-America. 31 
