In many Mexican towns nowadays you see what's shown below:
In English sometimes that 10-ft-high, somewhat sprawling bush is called Candlebush and sometimes Ringworm Bush. It's CASSIA ALATA of the Bean Family. I think the last member of the genus Cassia we ran into was the Golden-Shower Tree, Cassia fistula, in Sabacché last September. You might enjoy comparing the two Cassia species just to better get a feeling for how different species within a genus share many features. The Golden-Shower Tree page is at http://www.backyardnature.net/yucatan/g-showr.htm.
The name Cassia alata is a good old Linnaeus one, "alata" meaning "winged," and what's winged are the legumes. Each 6-inch long, slender fruit bears four finlike wings with wrinkled or "crenulate" tops, shown below.
This species occurs throughout the world's tropics and I don't believe anyone knows where it's from originally. Many medicinal uses are listed for it but the most frequent use seems to be the making of lotions from flowers for skin infections, particularly ringworm.