Reexamining the classification proposed by Hurusawa, the phylogeny of Far Eastern Euphorbia subgenus Esula was analyzed using thirteen morphological and seventeen phenolic compound data. These data were analyzed independently and in combination using PAUP under the assumptions of Fitch parsimony. Ten species, comprised of three sections and five subsections within Far Eastern Euphorbia subg, Esula and one outgroup from sub& Chamaesyce, were used as terminal taxa. The phylngenetic results did not support the sectional classifications within subg. Esula proposed by Hurusawa. Section Decussatae was nested in the paraphyletic sect. Esula in all of the analyses, and the relationship of sect. Helio$copiae was equivocal among data sets. The disagreement of data sets over the placement of Euphorbia ebracteolata is probably due to a hybrid origin of the species and missing phenolic data for E. pallasii. A slster-group relationship of the Korean endemic E. fauriei with the widespread E. pekinensis was strongly supported by the morphological and phenolic data.

Light and scanning microscopies were used to evaluate the sectional boundary of 17 species included by various authors in Euphorbia sect. l~thymalopsis. Based on seed shape, surface ornamentation, and mucilage formation, five seed morphological types were recognized in North American section Tith~nalop$i$ and related species. These results did not provide added support for recent treatment of the sect. 7~th~cnalopsi$ s.s. However, a close relationship was suggested among species of the ~thymalopsi$ subsection Corollatae. In addition, including species from subsections Innocuae, Ipecacuanhae, and Sphaerorhizae within sect. T'sthymalop$i$ could not be justified, based on seed morphological data.