Contains very interesting drawings showing the amazing depth and extent that vegetable roots are capable of in favorable soil.
Widtsoe, John A. _Dry Farming: A System of Agriculture for Countries Under Low Rainfall. _New York: The Macmillan Company, 1920.
The best single review ever made of the possibilities of dry farming and dry gardening, sagely discussing the scientific basis behind the techniques. The quality of Widtsoe's understanding proves that newer is not necessarily better.
End of the Project Gutenberg Etext of Gardening Without Irrigation: or without much, anyway by Steve Solomon