Seed Morphology in the Oncidiinae and Related Subtribes (Orchidaceae)

Abstract

A survey of seed morphology, using scanning electron microscopy, of the Oncidiinae and related Neotropical subtribes found that the majority of these taxa exhibit a uniform seed condition, designated the Maxillaria type. The two major variants within the Oncidiinae are anticlinal wall ornamentation and two different forms of extensions of the testa cells: the former in the vegetatively modified (rat-tailed and mule-eared oncidiums) groups and the latter in taxa restricted to the outer portions of the canopy (twig epiphytes). Other minor variants are also discussed. The exhibited variation is systematically significant only above the generic level. This study identified the Maxillariinae as a close relative of the Oncidiinae but failed to find any dif- ferences between the types of seeds observed in the Lockhartiinae, Oncidiinae, Ornithocephalinae, Pachyphyllinae, and Telipogoninae.