Vegetation south of the Land Ice, 203 
Lupinus perennis, Quercus ılicifolia (= O. nana), Corema Conradii. At Culver’s 
Gap, Britton found Polygala polygama, Lechea racemulosa, all abundant in 
sandy soil along the coast. In all probability, therefore, the flora of the Kitta- 
tinny, or Shawangunk Mountains described above is peculiarly an endemic one 
showing relict endemism and that the flora of the pine barrens of the coast 
is a derived one. The same peculiar distribution is noticed in the southern 
states where on the high mountains above five thousand feet such plants oc- 
eurring also on the sandy flats of the coastal plain are found, viz., Zygadenus 
limanthoides, Xerophyllum asphodeloides, Amianthium (Chrosperma) muscae- 
Zoxicum, Leiophyllum (Dendrium) buxifolium, and Hudsonia montana of Table 
Mountain related to Audsonia tomentosa of the coast. 
With reference to the coniferous vegetation previously mentioned, in this 
connection it is a noteworthy fact that the distribution of the long-leäf pine 
Pinus palustris in general coincides with the area of the Atlantic and Gulf 
coastal plains except on such mountains as Pine and Horseleg where it is 
found above 1000 feet. This is largely influenced by the fact that in its 
demands upon the soil this pine is to be counted among the most frugal, as 
far, as mineral constituents are concerned, if only the mechanical conditions 
which influence favorable soil moisture are not wanting. It thrives best on a 
light silicious soil, loamy sand, pebbles or light sandy loam with a slightly 
clayey subsoil sufficiently porous to insure at least a partial under drainage and 
to permit unimpeded development of the long tap root. The Cuban pine, 
Pinus cubensis (= P. heterophylla = P.caribaeca) is confined to the coast plain 
of northern and central Florida and southeastern Georgia. The loblolly pine, 
Pinus taeda is a coastal plain species, while the pitch pine Pinus rigida, which 
occurs on the New Jersey coast and coastal plain is also a prominent tree on 
the mountain summits of northeastern Pennsylvania and elsewhere. 
Chapter II. Postglacial and Recent History of the North 
American Flora. 
1. Immediate Effects of Glacial Retreat. 
Boreal Associations and Forests. All of North America, north of the great 
terminal moraine, which marks the southern boundary of the continental ice 
sheet with the probable exception of the nunataks, unglaciated areas and parts 
of the Pacific coast has been tenanted by plants, which have migrated from 
several directions into the territory abandoned by the glacial ice. (See the arrows 
illustrating in the accompanying Figure 4 the directions of Plant Migration.) 
Geologists') believe from evidence afforded by the time that it has taken for 
the river to cut its gorge at Niagara, that 15,000, to 25,000 years have elapsed 
1) GILBERT, G. K.: Niagara Falls and their History. National Geographic Monographs, No. 1, 
Sept. 7. 1895. TArr, RALPH S.: The physical BR of New York State 1902: 266—299. 
