Anatomical characteristics as taxonomic tools for the species of Curtia and Hockinia (Saccifolieae–Gentianaceae Juss.)

The delimitation of species and even support of the genera Curtia and Hockinia, monotypic genus, are still controversial. To define anatomical characteristics that help resolve taxonomic problems, the stem and leaf anatomy of seven species of Curtia and Hockinia montana are described. Some characteristics are found in both genera: leaves with uniseriate epidermis, dorsiventral mesophyll, cells of the palisade parenchyma with invaginations, basal acrodromous venation with an incomplete marginal ultimate venation, presence of colleters and nectaries, stem with small wings and internal phloem. The types of stomata, the midrib vascular bundle, and the type and distribution of nectaries were used to separate the genera. The presence/absence of crystals, the sinuosity of the anticlinal walls of the epidermal cells, the type and distribution of stomata, and the distribution of nectaries distinguish species of Curtia. Our results suggest that these anatomical characteristics are potentially useful for clarifying the taxonomy of Gentianaceae, and that they represent an additional tool for distinguishing genera and identifying species of Curtia, particularly pointing out the need to revise the synonymy between C. patula and C. tenuifolia. We also highlight the first report of leaf nectaries and colleters in the Saccifolieae and the first record of stem nectaries in the Gentianaceae.