Bark anatomy in Croton draco var. draco (Euphorbiaceae)

Many arboreal forms of the genus Croton (ca. 800 spp.), amply distributed in the Americas, have latex-producing cells in their bark, which is widely used in traditional medicine to treat skin infections and some forms of cancer. Studies validate its ethnomedicinal use-more than 20 pharmaceutically important secondary metabolites have been reported for its latex and bark-but anatomical and ecological studies are scarce. Given this species' ample distribution, laticifer abundance could be affected by the environment. We tested this for genetically similar trees growing in two types of vegetation in Veracruz, Mexico at sites commonly visited by traditional doctors. We describe the bark anatomy of C. draco, focusing on the laticifers, histochemically characterize the bark and the latex extracted from it, and document differences in laticifer abundance in the two environments. We have also identified another cell type (what we call type B) in the secretory latex system and describe it histochemically and microscopically. The location of bark cells that contain essential oils is reported here for the first time. Given the genetic similarity of the trees at both sites, the between-site variation in the number of laticifers in stem and branch bark appears to be an effect of the environment.