Abstract: The observation of morphological features of seed surfaces in the genus Clinionia, including those of all 4 North American species and 11 populations of EasternAsian species (i. e. C. udensis),has been carried out by SEM. The results show that C.umbellulata differs in having more or less a smooth seedsurface with concave cratersfrom others in having striated ornamentation of seed surfaces.C. uniNra and C. andrewsiana,both from western North America,are related to each other by having similarseed ornamentations,while C. borealis, which is from eastern North America,has similarseed surface ornamentation to that of Changbalshan population of C. udensis. About 4 ornamentation types of seed surfaces in 11 populations of C. udensis can be identified byour results, with reference to the correlation between ornamentation variation and infraspecific differentiation,especially to that of diploid and tetraplold populations. It is apparent that the morphological features of seed surfaces may have some taxonomical significance at species level, while in C. udensis, population variation (including variationbetween seed surfaces)may reveal that the species is now in a stage of strong differentiation.