Yet trees are the great engines of nature. The mazzard cherry tree,
growing wild throughout the southeastern United States, often yields
twenty bushels of fruit. Fifty bushels and upwards are often obtained
from the mature apple trees. The walnut yields its bushels, the
persimmon breaks with fruit.

Europe shows us an agriculture making considerable use of crop-yielding
trees other than the ordinary fruits. Mr. C. F. Cook, of the Department
of Agriculture, is the authority for the statement that Mediterranean
agriculture began on the basis of tree crops, and there are now about
twenty-five such crops in the Mediterranean basin. The oak tree
furnishes five, cork bark, an ink producing gall which enters into the
manufacture of all our ink, the Valonia, or tannin-yielding acorn, which
is an important export from the Balkan states; the truffle worth several
million dollars to France; and lastly the acorn. In the Balaeric Isles,
I am informed, certain acorns are more prized than chestnuts and the
trees yielding them are grafted like apples, and the porker is turned
out to make his living picking up acorns where they fall, and enriching
his diet with a special kind of fig grown in the same way for his use.
We Americans are too industrious; we insist upon putting a pig in a pen
and then waiting upon him. The pistachio, the walnut, the filbert and
the chestnut are all important tree crops in parts of the Mediterranean
countries and many American travelers have probably seen the chestnut
orchards of France and Italy, which I have found by examination are able
to make the rough and unplowable mountain-side, bristling with rocks, as
valuable as the level black prairies of Illinois.

The natural objection may be raised that the utilization of so much
hilly land in fruit and nut-yielding trees will give such supplies of
new food that people will refuse to use them. The above objection is