POLLEN MORPHOLOGY, TRICHOME TYPES, AND RELATIONSHIPS OF THE GRONOVIOIDEAE (LOASACEAE)

The pollen of all four genera of Gronovioideae-Cevallia, Fuertesia, Gr onovia, and Petalonyx-was examined in light microscopy, and scanning a nd transmission electron microscopy. The pollen of Cevallia, of Fuerte sia, and of Gronovia can be easily distinguished from each other and f rom all remaining Loasaceae. Only Petalonyx, with a striate tectum, sh ows a clear relationship to the Mentzelioideae and Loasoideae, the vas t majority of which have striate-reticulate or striate tecta. The tric home data are mostly congruent with the pollen data: Cevallia, Fuertes ia, and Gronovia each have a distinctive trichome not known to occur e lsewhere in the family, while Petalonyx has only the common types. A c ladistic analysis of Gronovioideae utilizing Mentzelia as the outgroup proposes that Cevallia, Gronovia, and Fuertesia are a sister group to Petalonyx within the subfamily. The relationships of the four genera to each other and of Gronovioideae to the Loasaceae are discussed.