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Several taxonomic treatments of Styrax (Styracaceae) exist in regional floras of Asia, but the Asian species of the genus have not been comprehensively revised since 1907. A treatment of the Asian taxa of S. series Cyrta with imbricate floral aestivation was accomplished in 2003. To complete the taxonomic revision of S. series Cyrta, we conducted a taxonomic revision of the species of the series with valvate aestivation of the corolla lobes. Our revision comprises 11 species with a combined distribution from eastern India through southern China and Malesia, Melanesia, and Micronesia, although the group is absent from the Philippines. We resurrected S. bracteolatus, S. rubifolius, and S. warburgii as species to be recognized, and we corrected the misapplication of S. finlaysonianus, previously used for a species in S. series Benzoin. Styrax finlaysonianus and S. warburgii are segregated from the broader concept of S. agrestis recognized in prior treatments. The circumscriptions of the heretofore poorly delimited species S. confusus, S. faberi, and S. fortunei are clarified and their possible introgressants discussed. We observed unique combinations of characters in some problematic specimens whose taxonomic status remains unresolved because only single specimens with either flowers or fruits were available; at least some of these may represent undescribed species. Lectotypes are designated for Cyrta agrestis, S. argyi, S. bracteolatus, S. calvescens, S. casearifolius, S. confusus var. microphyllus, S. dasyanthus, S. dasyanthus var. cinerascens, S. faberi, S. finlaysonianus, S. formosanus, S. fortunei, S. fukienensis, S. henryi, S. henryi var. microcalyx, S. iopilinus, S. philadelphoides, S. rostratus, S. rubifolius, S. serrulatus var. agrestis, and S. virgatus. A neotype is designated for S. warburgii. Keys, descriptions, distribution maps, and conservation assessments are provided for all species. Styrax agrestis, S. bracteolatus, and S. rubifolius are rare endemics of conservation concern, with highly restricted distributions.

Styrax agrestis (Lour.) G. Don, is a deciduous species of Styracaceae with beautiful shape, drooping flowers, and blooming like snow. Here, we characterized the complete chloroplast (cp) genome of S. agrestis using next generation sequencing. The circular complete cp genome of S. agrestis is 157,893 bp in length, containing a large single-copy (LSC) region of 87,512 bp, and a small single-copy (SSC) region of 18,285 bp. It comprises 136 genes, including eight rRNA genes, 37 tRNAs genes, 90 protein-coding genes, and one pseudo gene. The GC content of S. agrestis cp genome is 36.96%. The phylogenetic analysis suggests that S. agrestis is a sister species to Styrax faberi in Styracaceae.

Several taxonomic treatments of Styrax (Styracaceae) exist in regional floras of Asia, but the Asian species of the genus have not been comprehensively revised since 1907. To help rectify this, we conducted a taxonomic revision of the Asian species of Styrax series Cyrta with imbricate corolla aestivation. Our revision comprises 17 species with a combined distribution from Japan south to Sumatra and west to Nepal. The circumscriptions of the heretofore poorly defined species S. hookeri and S. serrulatus are clarified. Styrax agrestis var. curvirostratus is elevated to the species level, and lectotypes are selected for S. duclouxii, S. floribundus, S. hemsleyanus, S. hookeri, S. hookeri var. yunnanensis, S. hypoglaucus, S. japonicus, S. limprichtii, S. macranthus, S. obassia, S. perkinsiae, S. serrulatus var. latifolius, S. shiraianus, S. supaii, and S. wilsonii. Keys, descriptions, and distribution maps are provided for all species.