Quote
"In , s are scattered like gems in an arborescent matrix. They grow mainly upon the rocky slopes of hills and mountains and are generally lacking in the valleys and on the plains. Hence, the distributional pattern is islandlike. Compared with the massive populations of agaves in and in the , they are very sparse in Sonora. However, they are distinctly characteristic of the succulent component in the vegetation of our America deserts and arid regions ... … Desert species exist with about 5 inches or less annual precipitation and can endure rainless years; montane species receive 30 or more inches annual precipitation."
H
Howard Scott Gentry




