REPORT ON FORESTS. 237 
present agricultural, was formerly the great white-pine region 
of North America. ‘The white pine of the Transition zone and 
the short-leaf pine of the Carolinian zone meet on the edge of 
the Coastal Plain of New Jersey. 
The Carolinian zone is characterized by the short-leaf pine 
(Pinus echinata), sassafras, persimmon, liquidamber, magnolia, 
white cedar (Chamecyparis thyotdes), cardinal bird, opossum,* 
grape, English walnut,t sweet potato, etc. On its southern 
borders the long-leaf pine (P. palustris), the old-field pine 
(P. teda),t the bald cypress (Taxodium distichum) and the 
southern magnolias appear. In this zone§ the white cedar 
(C. thyordes) and short-leaf pine (P. echinata) reach their 
optimum. || 
Throughout the entire mainland of the Coastal Plain of New 
Jersey very light sandy soils predominate, although there are 
many beds of heavy clay, and ridges of road-gravel, also sand 
and clay loams and vast stretches of mucky swamp-lands. ‘‘he 
higher portions of the upland are usually gravelly, the interme- 
diate sandy, and the lower, loamy and clayey. ‘The farther 
south the richer the soil and of course the thriftier the forest 
growth. .The gravel is yellow and consists of small water-worn 
quartz pebbles mixed with sand and clay. When of the proper 
*The oppossum (Didelphys virginiana), about which so much has been written because of its mar- 
supial pouch and peculiar habit of feigning death, is arboreal in habit, with hand-like feet and prehensile 
tail, and is fond of the fruits of the persimmon tree, the seeds of which it is instrumental in distributing. 
It is highly esteemed as food, especially by the negroes of the South. 
+ East of the Rocky mountains the Persian walnut has been most successful in a limited area aloug 
the Atlantic coast from New York southward through New Jersey, southeastern Pennsylvania, central 
Virginia, North Carolina and Georgia, Farther south it does not succeed, owing mainly to the depre- 
dations of microscopic worms, which cause a disease commonly known as “ root-knot.’” 
tOne ‘specimen of Pinus teda was discovered by Mr. Pinchot, and another by Mr, Ar. hur Hollick, 
in Southern New Jersey. The region of the Pokomoke river, on the peninsula between the Delaware 
and Chesapeake, is, as far as I have been able to observe, the most northern limit of the natural growth 
of the bald cypress. ; ; 
2 According to the investigations of the U.S. Biological Survey (see ‘* Laws of Temperature Control 
of the Geographic Distribution of ‘Terrestrial Animals and Plants,’’? National Geographic Magazine, Vol. 
VI, December, 1894), the northward distribution of terrestrial animals and plants is governed by the sum 
of the positive temperatures for the entire season of growth and reproduction, and that the southward 
distribution is governed by the mean temperature of a brief period during the hottest part of the year. 
According to Prof. Merriam the species of the Carolinian belt require a total quantity of heat of at least 
6,400° C. or 11,500° F., but apparently cannot endure a summer temperature the mean of which for the 
six hottest consecutive weeks exceeds 26° C. or 78.80 F, The northern boundary of this zone, therefore, 
is marked by the isotherm showing a sum of normal positive temperatures of 6,4:0° C. or 11,500° F., 
while its southern boundary agrees very closely with the isotherm of 26° C. or 78.8° F. for the six hottest 
weeks. The minimum temperature was assumed to be 6° C. or 43° F., that is, the point where meta- 
bolic pr are just possibl 
|| By optimum is meant the combination of conditions that produces the best average result. 
