Unusual carpological characters in Marlothiella gummifera (Apiaceae)

Flowers and fruits of the monotypic Namibian endemic Marlothiella gummifera were examined to explore anatomical variation and to highlight problems associated with the homology of certain character states. Some unusual new features observed in the fruits and ovaries raise questions regarding the homology of fruit heteromorphy, rib oil ducts, vittae and carpophores in subfamily Apioideae. These include the irregular occurrence of heterocarpic ovaries, oil ducts on both the internal and external sides of the vascular bundles (the inner dwarf ducts), short ducts in the commissural area, and carpophores (only rarely present). The fruits of Marlothiella share several unusual features with the genus Lichtensteinia, namely concentric rings of cells around the rib oil ducts, of which the innermost are irregular in size and shape, very small vascular bundles that are usually comprised of two separate strands, and the occurrence of heteromorphy in fruits and ovaries. These two genera are morphologically very different and it is encouraging to find anatomical data to support their presumptive relationship based on molecular studies.