a. Peniocereus greggii from flood-plain near West Wash, showing fleshy main 

 root and most important laterals. 



b. Condalia spathulata from flood-plain of the Santa Cruz. 



c. Root-system of Prosopis velutina partly exposed by the caving bank of the 

 Santa Cruz. Vertical distance from surface of ground to water is approximately 5 m. 



d. Young plant of Prosopis. The squares are centimeters. 



e. f, g. Cuttings of Opuntia arbuscula (Tucson), O. arbuscula (Sacaton), and O. 

 vivipara, all grown under similar conditions and with a large water supply. 



