Ruellia umbrosa (Ruellieae, Acanthaceae) a new and critically endagered species from Lowlands of the Goias state, Brazil

Ruellia umbrosa, a new species from the riparian forest in the lowlands of the Goi??s state, is described and illustrated. It is similar to the South American species R. erythropus and R. epallocaulos by the decumbent stems rooting at nodes, solitary flowers in the axils of the upper leaves, and capsules with eight or more seeds, but differs in having white or slightly mauve corollas, absence of bractlets, corolla with tube and throat similar in size, calyx with 5 lobes equal or slightly subequal with dense trichomes, and larger number and size of the seeds by capsules, among other characters. It grows in an environment under strong anthropogenic pressure in a small area and, therefore, was classified as Critically Endangered.