Pollen morphology of Periploca (Periplocaceae)

The pollen morphology of all 13 species of Periploca L. was studied. All the species are characterized by pollen grains arranged in tetrads. The arrangement of the grains may be rhomboidal, decussate or linear. Linear tetrads were only observed in P. acuminata Rahman & Wilcock, P. sepium Bunge and P. aphylla Decaisne. The exine is smooth. Exine structure consists of an outer, homogenous stratum (tectum) subtended by a granular stratum. Except for small differences which may occur between species in pollen size, the pollen is uniform in morphology