Pollen morphology and the bi-reticulate exine of the Phyllanthus species (euphorbiaceae) from mauritius and réunion

Abstract

The pollen grains of the Phyllanthus species of Mauritius and Réunion have been divided into seven pollen types. The different species and varieties of teh “phillyreifolius” group have close affinities and can be arranged in a continuous morphological series. All grains in this series are characterized by a two-layered or bi-reticulate ornamentation. They have a peripheral reticulum which consists of arch-like muri (in cross-section) and variform lumina and this covers an infra (micro-) reticulum, the structural units of which are connated with the muri of the suprareticulum. Contrary to earlier observations the Phyllanthus amarus type also shows a bi-reticulate ornamentation; this suggests a relationship between this type and the “phillyreifolius” group. The Phyllanthus maderaspatensis, P. casticum and P. tenellus types, however, have eu-reticulate ornamentation. The P. urinaria type resembles the P. amarus type, but its ornamentation is not clearly bi-reticulate and is better termed tectate-perforate. In the P. casticum type the pollen grains show very characteristic ectoapertures and they are of special interest as many Phyllanthus spp. occurring in Africa and Asia belong to the same type.