Abstract: By observing leaf epidermis of ten species in Paphiopedilum under the light microscope, we compared their cell shapes, anticlinal walls, stomatal types, and subsidiary cell shape and measured eleven quantity indexes, including size of epidermis cell, size of stomata, stomatal density and its index, to study species' difference. The epidermis cell was polygon or rectangular, anticlinal wall was circular, nearly circular, straightarched and straight, and that stomata was mainly surrounded by tetracytic. By principal component analysis on 15 indexes, the quantity indexes related to ecological adaptation (size of epidermis cell and stomatal density) were greatly contributed to species variation, which reflected that there was significant adaptation differentiation to water and light in Paphiopedilum species from different habitation. Moreover, the types of anticlinal wall and stomata, the shapes of epidermis cell could be applied to divide its subgenus. The clustering result based on leaf epidermis characters supported treatments on interspecific relationship and division of subgenus by rDNA ITS evidence.

Key words: Paphiopedilum, leaf epidermis, principal component analysis, clustering, interspecific relationship