I've found two plants that I've not been able to identify using Southern USA and Western plant sites. They both seem to thrive in heat and drought in uncultivated areas of central Texas. Plant A is a vine that prefers shade and Plant B grows low in direct sunlight.
Carolina snailseed http://www.wildflower.org/plants/result.php?id_plant=COCA Croton monanthogynus possibly. http://www.wildflower.org/gallery/result.php?id_image=3344