For each species, a description of morphological and chemical characters is presented, and the variation and diagnostic characters are briefly discussed. Type material was examined for all previously published species except for V. procera , V. tuberculata , and V. tigrina . By contrast the drawings, prepared by four different authors, are of rather poor quality, ranging from mere pencil sketches to ink drawings with discontinuous outlines and excessive or inadequate shading. A glossary to the terminology mainly used in the species description and discussion completes this publication. The taxonomy of Niebla relies on both chemical and morphological characters.
Secondary metabolites are primary characters, in the sense that they define species groups.
Within these groups, species are differentiated by morphological characters. These morphospecies thus represent morphotypes within a chemical group. Although this approach is compared by the author to a phylogenetic species concept within which chemical characters serve as diagnostic features, a formal discussion of relationships among the species is not given, nor is a discussion on the metabolic relationships among these chemicals provided in support of their taxonomic or phylogenetic use. It is thus not clear whether species within a chemical group are indeed more closely related to each other than are similar morphotypes with distinct chemical profiles. Within each of these two groups, however, morphological differentiation between chemically related sub-groups is however less clear.