The character states of the Caribbean monotypic endemic Strumpfia (Rubiaceae)

Abstract

Strumpfia, restricted to littoral habitats, is characterized by ternately arranged ericoid leaves with extreme xeromorphic adaptations. The flowers, with quincuncial (imbricate s.1.) corolla lobe aestivation, have the anthers fused into a “true” anther tube. The bicarpellate gynoecium has two erect, anatropous ovules per locule. In addition to the “true” septum, the ovary also has a secondary or “false” septum, arranged at right angles to the former and only developed in the upper part of an ovary. The drupaceous fruits contain a plurilocular stone which, typically, is four‐seeded. Erroneous descriptions of Strumpfia's ovary as bilocular with one ovule per locule may have been due to the frequent presence of only two seeds in a stone (one seed per locule aborted and crushed). As opposed to the widespread protandry in the Rubiaceae, the genus shows proterogyny. In functionally female stage, the style is straight and raises the exposed stigmatic surfaces above the level of the anther tube and its apical appendages. In functionally male stage, the style contracts so that the stigmas “plug” the entrance to the anther tube; at this stage the pollen is released from the anther tube by means of apical pores. Strumpjia has a chromosome number of x=n=II (first count for the genus). The genus' systematic position has hitherto been considered to be uncertain. A comparison of its character states with other Rubiaceae, nevertheless, led to inconclusive results. Because of a) many unusual and, in part, unique features and b) the lack of detailed comparative data for neotropical Rubiaceae, the genus' subfamilial and tribal position remains obscure.