Comparative floral surface micromorphology helps to discriminate between species of Paphiopedilum (Orchidaceae: Cypripedioideae) from Peninsular Malaysia

Abstract. The floral micromorphology of critically endangered Paphiopedilum Pfitzer [P. barbatum (Lindl.) Pfitzer, P. callosum var. sublaeve (Rchb.f.) P.J.Cribb and niveum Stein] were analyzed concerning either infrageneric taxonomy or physioecological demands. first two species are phylogenetically close superficially identical but occur with distinct phytogeographical distributions in the region. third is a distant congener that inhabits limestone areas northern part Peninsular Malaysia. Using scanning electron microscopy (SEM), we investigated surface dorsal sepal, synsepal, lateral petals, pouch labellum, staminode. Amongst features epicuticular waxes, ornamentation, trichome distribution type, pustular glands, papillae. Our study supports distinction from sublaeve, which belong to subgenus Paphiopedilum, niveum, belonging Brachypetalum, separated monophyletic clade. Comparatively, has Type III non-glandular trichomes on margin its absent sublaeve. distinguishable by confined ornamentation staminode discriminate between differentiates them niveum. Compared stomata superficial prominently raised guard cells. From view, absence glandular trichomes, low occurrence papillae parts explain unscented flowers A combination examined taxonomically valuable for delimitation at level, although diagnostic characters far inadequate generic taxonomic revision. more extensive sampling three subgenera including Parvisepalum, anticipated elucidate level variation microcharacters.
 Key Words: importance, Malaysia, microscopy,