The Pollen Morphology of the Haloragaceae with Reference to Taxonomy

Pollen morphological investigations of the family Haloragaceae were carried out using light microscopy supplemented by electron microscopical studies. An attempt was made to correlate the pollen morphology with the taxonomy of the family. The pollen morphological data provide clear support in favour of the division of the family into two separate families, respectively, Haloragaceae and Gunneraceae. Both subfamilies, i.e., Haloragoideae Schindl. (excluding a few species in the subsection Spongiocarpus Schindl.) and Gunneroideae Schindl., are stenopalynous. Important arguments concerning pollen morphology, gross morphology, ecology, and type of pollination, favour a regroupment of the Haloragis species belonging to the subsection Spongiocarpus, which is related to the genus Laudonia Lindl. Eventual fusion of these Haloragis species in the subsection Spongiocarpus with the genus Loudonia is worth consideration. The Haloragaceae is an interesting plant group from a palaeobotanical point of view. A review of the literature concerning fossil findings of the Haloragaceae and sporomorphs of the Stemma Normapolles Pf., some of which most probably could have been related with the Haloragaceae, point out the interest of this family to palaeo-botany. The Haloragaceae, which have an antarctic origin, seem to have been more widely distributed during the Tertiary than at the present time.