14 MISC. PUBLICATION 162, U. S. DEPT. OF AGRICULTURE 
timber trees, the longleaf and slash pines are highly important as the 
source of the gum from which turpentine and rosin are manufactured. 
Other species found in the pinelands are southern red, turkey, black, 
post, laurel, and willow oaks; black gum; pond, spruce, and sand pines. 
Another tree of commercial importance, found in the southern for- 
est, is the baldcypress. It grows mostly in the swamps and 
lowlands and is one of the few coniferous trees that shed their 
leaves in the fall (fig. 8, 8B). The supply of this species also is gradu- 
ally dwindling after years of heavy cutting. 
Perhaps the most important hardwood tree of the southern forest 
is sweet gum, or red gum. At one time its wood was considered of 
little importance because of its tendency to warp and twist. With 
the introduction of proper seasoning methods and the diminishing 
supply of finishing woods, the sweet gum has risen from a position 
of comparative obscurity to a rank of seventh among all lumber- 
producing trees (1938). As a veneer wood, sweet gum leads all other 
woods in the country and ranks second as a slack-cooperage wood. It 
also goes into many other products. 
Both baldcypress and sweet gum are inhabitants of the alluvial 
bottoms and swamps. Also growing in bottom-land portions of the 
southern forest region are tupelo and black gums; water, laurel, live, 
overcup, Texas red, and swamp white oaks; yellow poplar; hickories 
(including pecan) ; beech; ashes; red and silver maples; cottonwood 
and willows; elms; sycamore; hackberry; honeylocust; bays; 
magnolias; spruce pine; and southern white cedar. 
TROPICAL FoREST REGION 
The tropical forest region is so small as to be of almost negligible 
commercial importance. It consists of two fringes of forest along 
the coast in extreme southern Florida and extreme southern coastal 
Texas. Its total area is probably not more than 400,000 acres and 
the density of the forest varies greatly. Many kinds of hardwoods 
are found in this region, but most of them are small and bear ever- 
green leaves and pulpy berries or stone fruit. A few, like the mastic 
or “wild olive,’ are of some commercial or economic importance. 
The mangrove is also valuable because the impenetrable thickets it 
forms hold the muddy banks, cause new land to be built up, and act 
as a windbreak against tropical hurricanes. 
The principal trees of the tropical forest region are mangrove, 
royal and thatch palms, Florida yew, wild fig, pigeon plum, blolly, 
wild tamarind, gumbo limbo, poisonwood, inkwood, buttonwood, 
mastic or wild olive, and Jamaica-dogwood (fig. 9). The tropical 
species in this region are at the northern limits of their natural 
ranges which include mostly some or all of the West Indies, the 
Bahamas, Central America, and South America. The trees probably 
grew from seed washed ashore during storms or distributed by birds. 
Rocky MowunrtTAIN Forest REGION 
The forests of the Rocky Mountain region occupy the high eleva- 
tions of the various ranges of the Rocky Mountain system between 
the Great Plains and the Sierra Nevada, from Mexico to Canada. 
They are broken by many treeless valleys or plateaus. Because of 
