The occurrence of apical septum in the ovary of Rhyncholacis, Apinagia, Marathrum and Mourera (Podostemoideae - Podostemaceae): taxonomic implications
published: Apr 2, 2003
The apical septum has been documented for eight species of four genera of subfamily Podostemoideae (Podostemaceae) of the New World: Rhyncholacis, Apinagia, Marathrum and Mourera. This rare structure, occasionally found in bi-carpellate ovaries among dicotyledons, depends on anacrostyly of the respective carpels and develops a paracarpous region above of a basally syncarpous ovary. The apical septum resembles the septum at the base of a syncarpous gynoecium, but contrasts by the dorsal medial bundle to the septum at the ovary base which is supplied by the ventral medial vascular strand of the two carpels. Though otherwise of less taxonomic value, the apical septum is found in like manner within a closely related taxonomic group (tribe Lacideae sensu ENGLER) of Podostemoideae and is, therefore, considered to be an important characteristic. All the more, as the apical septum, too, occurs in the bi-carpellate Weddellina squamulosa (subfamily Weddellinoideae) which, except for the lack of the spathella and dithecous leaves, resembles the herein investigated species of the subfamily Podostemoideae, but also matches in several features with the tri-carpellate species of subfamily Tristichoideae. Weddellina squamulosa is seen linked to Mourera, Apinagia, Rhyncholacis and Marathrum as well as to members of Tristichoideae. From the available data, the subfamily Weddellinoideae has an intermediate position between the two other subfamilies.