View photos of the edible and medicinal plant, Juglans nigra (Black walnut), profiled in the Wild Edible Series: Arkansas, Kansas, Louisiana, Missouri, Texas: Vol 1, and others.

A passage from Wild Edible Plants of Texas (Volume 1):

Black walnut is the largest of the native Texas growers. The nuts of the other two species are smaller, however just as edible. They should first be collected whole, air–dried, and then shelled.