Premise of research. Previous studies of secretory structures in species of the Neotropical dragon’s blood Croton (section Cyclostigma) show inconsistencies in their classification. An accurate assessment of the identity and homology of such structures is essential for taxonomic and evolutionary studies. Methodology. Field-collected leaves, stipules, and flowers at different developmental stages were sampled. The material was subjected to standard anatomical study by light microscopy and SEM, and secretions were evaluated by histochemical analyses. Pivotal results. Leaves and flowers of Croton echinocarpus and Croton urucurana present five secretory structures (idioblasts, laticifers, colleters, extrafloral nectaries, and floral nectaries) with high similarity between the two species. Idioblasts secrete compounds of a mixed nature; laticifers are branched and nonarticulated; and colleters and nectaries present hydrophilic secretion. The leaf marginal glands previously described as extrafloral nectaries are actually colleters of the standard type. We found colleters in staminate and pistillate flowers. The histochemical tests detected proteins in the secretions of all structures. Conclusions. The classes of secondary metabolites detected support the biological activities of secretion described in the literature. The correct identification of colleters in flowers establishes a new register of these structures in flowers of this genus. We show that an approach integrating anatomic structure, histochemistry, and period of secretion activity allows for a more accurate classification and homology assessment of secretory elements in this genus, which is exceptionally rich in this type of structures.

— We describe and illustrate four new species of dragon's blood trees (Croton sect. Cyclostigma) from western South America. Three of the species, Croton beckii from Bolivia and Peru, C. camposii from Peru, and C. santamartensis from Colombia, grow in montane Andean forest, whereas C. tumbesinus occurs in dry forest of the Tumbes/Piura ecoregion of western Ecuador and Peru. The characters that place them in Croton sect. Cyclostigma include the arborescent habit, the presence of reddish to yellowish latex, an indument of stellate trichomes, conspicuous and persistent stipules, acropetiolar/basilaminar nectary glands, and terminal inflorescences with bisexual cymules at the base. These new species give additional support for the Andean region being the main center of diversity of this Neotropical Croton clade, as well as being a region whose biodiversity knowledge is still incomplete.

Croton amentiformis, a new species of Euphorbiaceae from western South America, is described and illustrated. Morphological evidence and data from leaf anatomy indicate that the new species belongs to the dragon’s blood group (Croton section Cyclostigma). The dense and congested inflorescence is unusual within the genus. This singular dragon’s blood species is dedicated to the Florence Tropical Herbarium (FT) on the occasion of its 100th Anniversary celebrated in 2014.

The microphylls of Selaginella bear structures that have been given names as diverse as idioblasts, papillae, sclereids, fibers, and warts, yet they resemble silica bodies. However, for most species of the genus, no study has ever shown the composition of these structures or proven their nature comprehensively. Based on scanning electron microscopy and energy dispersive X-ray spectroscopy analyses, we confirmed the presence of silica bodies in microphylls of Selaginella, described four distribution patterns of the structures, and carried out a terminology review. The presence of silica may be related to mechanical protection of the cell wall, activation of defense mechanisms, and providing support for microphylls. Further in-depth analyses based on studies on the evolution of this character remain necessary to elucidate its relevance for the ecological relationships and systematics of Selaginella.