A new Ambrosia (Asteraceae) from the Baja California Peninsula, Mexico

ambrosia humi león de la luz et rebman, sp. nov., a member of the franseria alliance, is here described and illustrated. this taxon is apparently endemic only to mesa de humí in the sierra de la giganta of baja california sur, mexico. this new species is a subshrub with three-parted leaves that are gently scented and viscid when fresh, and it has a bur-like pistillate head, at maturity it is densely covered with strong, sharp, aculeate spines.