Abstract: In the present paper the pollen grains of Convallaria majalis L., Speirantha gardenii (Hook.) Baill., Reineckea carnea (Andr.) Kunth and Theropogon pallidus (Wall. ex Kunth) Maxim., all the unique member of their own genus in the tribe Convallarieae were examined under light microscope (LM) and scanning electron microscope (SEM). They can be divided into two groups. The Pollen grains of the first three species are larger (39.95-49.35×21.15-30.55 μ ), with thick granular-finely-reticulate or finely reticulate (LM) and finely reticulate (SEM) exine, and with distinct differentiation of sexine and nexine. The pollen grains of the other species are much smaller (25.85×18.8μ), with thin psilate (LM) and minutely granular (SEM) exine, and with indistinct differentiation of sexine and nexine. According to Nair and Sharma (1965), the exine surface ornamentation is a significant morphological character helping a great deal in the categorization of various genera and species within Liliaceae. The wide range of exine patterns provides ample evidence for tracing pollen evolution within the family from a retipilate to psilate condition by the processes of fusion, zonation and reduction. If their viewpoint is correct, the pollen of Theropogon may be regarded as a type more advanced than that of the remaining 3 genera of the tribe Convallarieae. Besides the differences in pollen morphology, Theropogon also differs from the other 3 genera in the characters listed in the table. The data taken from the other authors are indicated. Though there are some significant differences between Theropogon and the other 3 genera, the present authors, in a discreet attitude, merely point out the problematic systematic position of Theropogon in the tribe and would like neither hastily to give it a subtribal or tribal rank nor to transfer it to another tribe before an overall study.

Key words: Liliaceae, Convallarieae, Pollen grain, Microstructure, Ultrastructure, Theropogon, Systematic position.