The anther is the source of several of the principal characters traditionally used for classification in Orchidaceae, particularly in Epidendroideae, where the greatest amount of variation is present. We examined the diversity of pollinium arrangement and anther orientation in Epidendroideae as well as in representatives of the other subfamilies using serial sections of successive ontogenetic stages of columns. An important question is whether the incumbent anther in Vanilloideae is distinguishable from that in Epidendroideae, as the shared possession of an incumbent anther is the key feature that unites the two groups, in disagreement with molecular patterns that suggest that they are not closely related. Anatomical study reveals that the principal difference in anther bending between the two subfamilies is the enormous expansion in the connective in the Vanilloideae, which is not seen in Epidendroideae. This connective expansion contributes substantially to positioning of the thecae near the rostellum. The anther in the vandoid subset of Epidendroideae is shown to be truly incumbent, with the bending achieved by a redirection of growth in very early ontogenetic stages, as opposed to the inflexing of a nearly fully-formed anther, as in the remainder of Epidendroideae. This heterochronic change is largely correlated with cellular pollinium stalks, and may facilitate the development of the complex pollinarium. It can also result in unusual pollinium shapes among the vandoids. Superposed pollinia result from a reorientation of developing thecae, and may be fully or only partially superposed. These results allow us to further refine character states that are crucial to our understanding of orchid relationships.

Key words: anatomy, anther, development, Orchidaceae