in the United States to support many millions of people; and
therefore the tree is the more important because it permits an
agriculture that will keep the soil indefinitely, and in permanent
production, without plowing.

I have aecidently discovered a better way of conserving moisture than by
plowing, and I have found it going on in widely scattered places and in
widely different climates.

Primitive peoples in many parts of the world have long since obtained
the advantage of cultivation, mainly, increasing the available moisture
for the tree or plant, without cultivation of the soil and the loss
which follows the washing of cultivated soils. As an example I cite the
Indians of Arizona, who have grown corn crops for centuries in a country
with but from six to fifteen inches of rain. They do this by planting in
little patches at the mouth of a gully where at the time of rain the
flood water is led away into furrows and depressions so that it
thoroughly soaks the ground in which the corn is planted.

My attention was first called to this practice by observing a good patch
of barley in the edge of the Sahara in Southern Tunis, where the gulley
flow resulting from a winter rain had spread itself out fan-*like and
soaked the triangular alluvial area of sand, which bore a fine crop of
barley in the midst of the desert.

For centuries the olive growers of parts of Tunis have led gulley water
to the olive trees where it was retained, in areas that resembled a
tennis court, with a 12 inch bank of dirt around it and two or three
olive trees within this area thus watered by impounding.

A practice somewhat similar to this is shown in F. H. King's classic
book on Chinese agriculture, "Farmers of Forty Centuries;" but the most
extreme case that has come to my attention is furnished by the Berber
tribe of the Matmatas, of Tunis. These people live on the edge of a
hilly, limestone plateau, where the rainfall is less than 10 inches and
in some years as low as five.

An important part of the food supply of these people is furnished by
date and olive trees which they grow in the gulches of their limestone
plateau. They built a dry rock dam behind which earth-wash lodges. In
this the trees are planted and every rain sends more earth and soaks
that which has collected. The plan can certainly not be called an
experiment for the people have lived there for centuries. They have
olive trees that are several centuries old and I have neve