Bulbophyllum section Didactyle comprises seven species, but distinction between these is often problematic. These species are pollinated by milichiid flies and air currents move the hinged labellum and press the pollinator against the gynostemium. The labellum structure is considered to be homogeneous and conservative for the genus. Therefore, the floral anatomy and micromorphology of B. section Didactyle were studied in order to identify characters useful for distinguishing the species. All species have sunken glandular trichomes on the abaxial surface of the sepals (possible osmophores) and a trilobed labellum, clothed with trichomes, with a secretory cavity in the callus that is bound by scale-like papillae. Of the c. 100 characters assessed, 25 varied between species, and each pair of species differed by at least four character states, mainly occurring on the labellum. The data presented allow for a distinction to be made between species and corroborates their grouping in B. section Didactyle, as proposed previously. The presence of osmophores and a nectary on the labellum is confirmed, although their structure is more diverse than anticipated. Moreover, structural differences between B. weddellii and the core of the section might be the result of the odour-mediated attraction of pollinators rather than flower morphology and thus phylogeny.

Bulbophyllum section Napelli, as recently circumscribed based on molecular analyses, comprises 12 species. These occur as epiphytes in the Brazilian Atlantic Rain Forest and in gallery forests in the cerrado vegetation, and thus differ from other Neotropical sections of Bulbophyllum, which are more variable in habit and habitat. To identify diagnostic characteristics that are representative of this section and to confirm whether there are characteristics that are related to their habit and habitat, their floral micromorphology and anatomy were studied using conventional techniques. Bulbophyllum section Napelli is characterized by sepals with sunken glandular trichomes and stomata on the abaxial surface, reduced petals with one vascular bundle (sometimes lacking), an entire labellum with a secretory sulcus on the adaxial surface and a keel with stomata or glandular trichomes on the abaxial surface, two pollinia, and crystalliferous idioblasts in all floral parts. Our data enable us to distinguish between species and show congruence with the present circumscription of B. section Napelli. The labellar epidermal surface of three closely-related species was unusual in its possession of unicellular trichomes and these appear to function as osmophores. A relationship between striate surfaces, iridescence and pollinator attraction related to the epiphytic habit and forest habitat is proposed.

Our paper presents reliable anatomical characters of the pinnae that allowed the identification of the recognized species of Butia through a purely anatomical key, in which specific identification is performed by a set of up to five characters. Leaf anatomy, already used to support new taxa in related genera, can also be useful to validate questionable Butia species and differentiate between similar species, but surprisingly does not reflect the proposed phylogenetic relationship between species of this genus.

The data support the view that there is a correlation between the inaperturate pollen production and the release of constraint on tetrad shape. However, in P. pusillus the tetrad shape may be constrained by a callose ring. It is also suggested that the lack of apertures in the pollen of Potamogeton may be due to the lack of specific sites on which callose deposition is completed. Moreover, inaperturate pollen of Potamogeton would be better classified as omniaperturate.

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