A scanning electron microscopic study of the seed coat structure of Curtia Chamisso & Schlechtendahl and Hockinia Gardner (Gentianaceae)

The six species of Curtia, including a hitherto undescribed species published here, as well as the monotypic genus Hockinia can be distinguished from each other by the seed coat structure. The anticlinal walls and the cuticle provide the most useful information. Curtia tenuifolia appears to be a complex species, but subsp. tenella can be readily separated from this complex by the seed coat structure. Heterostyly has been found in C. tenuifolia subsp. tenuifolia, C. obtusifolia, and Hockinia montana, but differences in seed coat structure can not be correlated with long-, short-, and equal-styled flowers. The differences in seed coat structure, the length of the seeds, and the number of cells per seed plead for maintaining Hockinia (closely related to Curtia) as a distinct genus. One new species of Curtia is described and a new combination is made.