474 Part IV. Chapter 2. 
summits and table-lands. Some plant geographers, among them MERRIAM, 
would place the higher mountain areas with the great northern coniferous 
forest, because they consider the forests of the highest mountains to be an 
extension southward of the northern forest. In all likelihood, as previously 
described (pages 209— 212), the trees of the northern forest, north of the great 
terminal moraine, have been derived from farther south and in all probability 
the coniferous forest formation and associations came from the higher Appa- 
lachian ranges in the middle and southern states. The writer, therefore, on 
historic grounds considers it best to include these isolated mountain 
forests surrounded on every side by a sea of broad-leaf trees, and removed 
hundred of miles from the pure coniferous forests of the north with the fo- 
rest formations and associations of the Appalachian Mountain District of our 
classification. This it seems to him is the natural method of treatment, first, 
because these forests in the minds of the laity are associated with the country 
where they are found, and second, because the deciduous trees of the lower 
forests mingle with and modify the coniferous formations and associations, 
producing tension lines which in peculiar manner modifies and alter the facies 
of the vegetation. 
a) Northern Mountain Area. 
The Appalachian mountain ranges enter southeastern New York terminating 
in the Catskill Mountains and Shawangunk Mountains. The streams of this 
area heading in the Alleghany Plateau on the west run southeastward into the 
tlantic Ocean and cut through the ranges by great gorges, that are popu- 
larly called water gaps; but south of New River the Appalachian ranges are 
drained into the Gulf. New River (Great Kanawha) and the James River 
represent the southern boundary of the northern mountain phyto- 
geographic area. 
ı. Territorial Remarks on the District. 
Exposure and situation have much influence on the distribution of plants 
in these northern Appalachians. Thus on Spruce Creek a tributary of the 
Juniata in Pennsylvania where this stream has produced a talus by its erosive 
action grow Sorbus americana, Betula papyrifera, Ribes prostratum, Heuchera 
Pubescens, and Linnaea borealis. In contrast to this association, we find scarce 
two hundred yards away a narrow intervale bordering the stream where on 
the alluvial bottom grows the southern papaw, Asimina triloba. Aristolochia 
sıpho also occurs climbing up Juniperus virginiana in this bottom ’). 
The original condition of the flora of the Catskills has been much dis- 
turbed by the removal of the marketable trees by lumbermen and by the 
settlement of the country. The list of introduced plants is a large one and 
among them are many noxious weeds. Originally the woods were damp owing 
ı) BuckHovT, W. A.: Northern Plants in Pennsylvania, Garden and Forest 1891, IV: 447- 
