CORK OAK-——-RYAN AND COOKE 
369 
TABLE 6.—Composite total rate of growth of natural cork oak 
Composite rate of growth 
Country 
EEN DANN Pave fa np sve, sAsynyoieafaalels is, su Refers staudin, Vs 
RIPALe tices e tin clacioh eiisraths aeromtieit ss oi 
Brance and Corsica’: <+.. 045.64. sists le oes 
Italy, Sicily and Sardinia................ 
Jliica 6S ee are eg Semecacte doce ie aren 
BremCHeNIOLGCCO...< <2 5.h/< <hsicys ovsia/rens inl, 
SPATS GVLOLOCEO s.Parerss Scie Sage epaje so als Se 
AifUTMIst ally «PPh ce NAO sia che kites s elle craic so 
Tempera- | Rainfall Soil Total 
ture 
0.9330 | 0.9759 1. 006 0. 916 
8509 9451 1. 047 . 842 
8740 | 1. 0080 1. 260 1.110 
9152 9192 1. 260 1. 060 
1. 0470 9952 1. 000 1. 042 
1. 0430 . 9166 1. 000 . 956 
1.0000 | 1.0000 1. 000 1. 000 
1. 2130 1. 0000 1. 000 1. 213 
. 9696 9678 1. 039 975 
The final results of the climatic anal- 
ysis show that in the Mediterranean 
region the cork oak grows: (1) at 
mean annual surface temperatures be- 
tween the limits of 50° and 70° F.; 
(2) under mean annual rainfalls be- 
tween the limits of 10 and 60 inches; 
(3) in a variety of soils ranging from 
the semiarid brown steppe soils to the 
moist tropical and subtropical red and 
yellow soils; and (4) at rates between 
the limits of 0.58 and 1.45. 
The Cork Potential 
The region within the United States 
potential cork area, which embraces 
all four of the above ‘‘Mediterranean 
elements of growth” is graphically pre- 
sented in figure 2 as the positive 
potential area. This map also includes 
an additional region, designated as the 
quasi-potential area, which is non- 
Mediterranean in its climatic elements. 
It is to be noted that old cork oaks are 
growing in both regions, despite the 
fact that the quasi-potential area has 
an average growth rate which is about 
30 percent more rapid than the 
Mediterranean maximum. This is 
rather definite proof that the cork oak 
will grow and thrive, within certain 
limits, beyond the Mediterranean 
climatic borders, and is sufficient evi- 
dence to establish the botanic position 
of the cork oak tree in this country as 
being actual rather than potential. 
Its potentiality lies solely in its economic 
position with, respect to cork pro- 
duction. 
The positive potential area is ‘so 
designated because it is felt that, if the 
Mediterranean region has been turn- 
ing out satisfactory cork for over 
2,300 years, this positive area, whose 
climatic elements and growth rates 
are identically Mediterranean, can be 
relied upon to produce cork of good 
commercial quality. This confident 
feeling is not only further strengthened 
but is also actually confirmed by the 
quality of cork obtained in stripping 
over 500 American trees in the 
positive potential area. These strip- 
pings yielded about 15 tons of mixed 
virgin and second-growth cork which 
were sent to the McManus Cork Proj- 
ect in Baltimore for evaluation. The 
results of physical and chemical tests 
showed the material to be suitable 
for making composition cork products, 
insulation blocks, and commonplace 
articles. It was found to be compar- 
able in all respects with Mediter- 
ranean cork of similar character and 
grade. 
No stripping has been done in the 
quasi-potential area, but specimens 
have been sporadically cut from a 
limited number of trees and, in all 
instances, the cork has been found to 
