370 
be of inferior quality to that in the 
positive area. It did not compare 
favorably with the poorest grades of 
Mediterranean virgin growth. This 
rather strongly indicates that the 
quality of cork decreases as the rate of 
growth increases and that commercial 
grades are not obtainable from regions 
in which the rate of growth exceeds 
the Mediterranean maximum limit. 
Therefore, in the United States, the 
growth of cork for a national economy 
should be restricted to the positive 
potential areas. 
All the cork coming from the 
Mediterranean region is not of equal 
quality; it varies considerably with 
location. Only part of it can be used 
for the highest type of manufacture, 
such as champagne and wine corks 
and composition cork liners for food 
and beverage closures, while the bulk 
is employed in the production of 
thermal insulation, compositions, and 
miscellaneous articles. ‘The finest- 
textured and _ highest-quality cork 
comes from Spain and Portugal which, 
as is shown in table 6, have the slowest 
rates of growth in the Mediterranean 
region, namely 0.842 and 0.916, re- 
spectively. From this it appears rea- 
sonable to infer that cork quality is 
a reciprocal function of the rate of 
growth. 
If rapid growth, especially that in 
excess of the Mediterranean maximum, 
is detrimental to the commercial 
quality of cork, the quasi-potential 
area should be limited to the planting 
and growing of the cork oak tree 
for its architectural and ornamental 
beauty, its soil conservation properties 
and, particularly, its acorn crops. 
Therefore, what the quasi-potential 
area loses in cork production is offset 
by what it gains in landscaping and 
hog-raising potentialities. Much of 
the barren and uncultivated lands in 
this area can be planted to cork oaks 
and transformed into parklike groves 
in which hogs can feed on the acorn 
crops and ultimately produce pork 
at the estimated rate of 30 to 40 pounds 
per acre per year. 
ANNUAL REPORT SMITHSONIAN INSTITUTION, 1948 
The geographic distribution of the 
positive and quasi-potential areas is 
also shown in figure 2. A study of this 
map shows that there are 27 States in 
the United States potential cork area. 
Eighteen contain positive areas only; 
they are: Arizona, California, Colo- 
rado, Delaware, Illinois, Indiana, Ken- 
tucky, Maryland, Missouri, Nevada, 
New Jersey, New Mexico, Oklahoma, 
Oregon, Tennessee, Utah, Virginia, 
and Washington. The following seven 
States contain both positive and quasi 
areas: Alabama, Arkansas, Georgia, 
Mississippi, North Carolina, South 
Carolina, and Texas. The remaining 
two, Florida and Louisiana, are wholly 
quasi-potential. 
The positive potential area presents 
itself as the most suitable location in 
which to build the Nation’s cork-forest 
industry, because it is identical to the 
Mediterranean region in climatic ele- 
ments and growth rate. It embraces 
an area of 888,050 square miles. If 
over 90 percent of this area is already 
occupied by cities, towns, roads, farms, 
pastures, woodlands, and other uses, 
there would still be more land avail- 
able than is needed to produce this 
country’s requirement of 160,000 tons 
of cork annually. It will be shown 
that no more than 1,000,000 acres 
(1,562.5 square miles) will be needed 
to produce cork at this rate. 
In order to obtain a fair estimate of 
what might reasonably be expected of 
the tree with respect to its production 
of cork, it is necessary to study sepa- 
rately each factor that produces a 
quantitative effect on the yield. Hav- 
ing done this, it becomes apparent 
that cork production is a function of 
the combined effect of several contrib- 
uting factors. 
The amount of cork which a tree 
will produce over a given period of 
time depends upon the rate of growth 
of its immediate environment and 
upon the regularity with which strip- 
ping operations are performed. After 
the removal of the first (or virgin) 
growth, a second growth begins within 
a very few months and progresses at 
