INTRODUCTION
The genus Cyperus L., comprising approximately 950 species distributed worldwide, is the second-largest genus within Cyperaceae (Muasya et al., 2002; POWO, 2025). Cyperus pacificus (Ohwi) Ohwi is a taxon within this genus, found exclusively in Japan and Korea (Hoshino et al., 2011; Park et al., 2016; POWO, 2025). It was originally treated by Ohwi (1938) as C. michelianus var. pacificus Ohwi and was later elevated to species rank as C. pacificus (Ohwi, 1944). This separation from C. michelianus (L.) Delile was based on morphological characteristics, such as the nearly distichous arrangement of glumes and short, straight or nearly absent awns (Ohwi, 1938, 1944). As part of this taxonomic process, the specimens examined by Ohwi (1938, 1944) included one collected in Korea (Seoul, September 1901, U. Faurie 976, KYO). This Korean specimen had previously been identified by Léveillé (1904) and Nakai (1911) as Scirpus michelianus L. (currently treated as C. michelianus). Subsequently, it was assigned to the newly described variety, C. pacificus var. margoinflatus S. Fujii (Fujii, 2016).
Currently, major online resources, such as POWO (2025) and Flora of China (Dai et al., 2010), include Korea within the distribution range of C. michelianus. However, the Korean specimens are generally recognized as C. pacificus following the interpretation of Ohwi (1944) (Lee, 1996; Ri, 1999; Park et al., 2016; Korea National Arboretum, 2020; National Institute of Biological Resources, 2024), although some literature, such as Oh (2000), still treats the taxon as C. michelianus var. pacificus.
Morphologically, C. michelianus has glumes arranged entirely in a spiral pattern (Kükenthal, 1935–1936; Dai et al., 2010; Verloove, 2012). In contrast, C. pacificus has glumes that are primarily arranged distichously, although some exhibit a spiral arrangement (Lee, 1996; Hoshino et al., 2011; Cho et al., 2016). However, some Korean literature has described the glumes of C. pacificus as spirally arranged (Lee, 1996, 2006; Ri, 1999). Additionally, Park et al. (2016) described the glume arrangement as distichous, but the accompanying illustration shows a spiral arrangement. In Japan, both the written descriptions and the accompanying photos or illustrations consistently depict the glumes of C. pacificus as distichously arranged (Hoshino et al., 2011; Katsuyama and Kitagawa, 2014).
Cyperus pacificus var. margoinflatus has marginal wings on the achenes, but the wings are distinctly inflated, distinguishing it from the typical variety (Fujii, 2016). In Korea, this variety has been referred to by the Korean name “Nal-gae-huin-bang-dong-sa-ni”, but its occurrence has not been reported in Korean literature since its original description.
During the re-examination of Korean Cyperus taxa, we recognized the existing confusion regarding morphological descriptions and distributional information. Accordingly, we determined that a taxonomic reassessment of Korean C. pacificus is necessary. In this study, we re-examined Korean specimens (including C. pacificus var. pacificus and C. pacificus var. margoinflatus) based on the original descriptions and observations of type specimens. Additionally, these specimens were compared with those of C. pacificus var. pacificus and C. pacificus var. margoinflatus from Japan, as well as C. michelianus from Taiwan, to evaluate their taxonomic identities.
MATERIALS AND METHODS
Taxon sampling
Specimens were collected from July 2024 to October 2025 in Korea (C. pacificus var. pacificus), Japan (C. pacificus var. pacificus, C. pacificus var. margoinflatus), and Taiwan (C. michelianus). Additionally, all collected individuals were prepared as dried specimens and deposited in the Hallym University Herbarium (HHU).
Morphological re-examination and comparison
A total of 101 specimens were examined for morphological re-examination and comparison. These included 72 specimens collected during this study, as well as specimens of C. pacificus var. pacificus and C. pacificus var. margoinflatus deposited in the Kyoto University Herbarium (KYO), the National Institute of Biological Resources Herbarium (KB), and the Korea National Arboretum Herbarium (KH). In addition, type specimens of C. pacificus var. pacificus and C. pacificus var. margoinflatus deposited at the Kyoto University Herbarium (KYO) were included.
The characters used for morphological re-examination and comparison were determined based on the original descriptions and relevant literature (Linnaeus, 1753; Kükenthal, 1935–1936; Ohwi, 1938, 1944; Dai et al., 2010; Hoshino et al., 2011; Fujii, 2016), including the arrangement of glumes, the length and characteristics of the awns, and the width of the marginal wing of the achene. The character states defined for each taxon in the original descriptions and relevant literature are summarized in Table 1.
RESULTS
Based on a re-examination with reference to the original descriptions and type specimens, Korean specimens previously identified as C. pacificus and C. pacificus var. margoinflatus were found not to conform to them. Moreover, in morphological comparisons, all Korean specimens (var. pacificus and var. margoinflatus) were found to be similar to C. michelianus:
In glume arrangement, C. michelianus and the Korean specimens exhibited an entirely spiral arrangement on the dorsal, lateral, and ventral sides, resulting in slightly convex spikelets (Fig. 1A1, 1B1, Table 2). In contrast, the Japanese C. pacificus var. pacificus and C. pacificus var. margoinflatus have glumes arranged distichously, with a spiral arrangement occurring only at the base or on one side, causing the spikelets to bend or curve to one side (Fig. 1C1, 1D1, Table 2).
Regarding awn morphology, C. michelianus and the Korean specimens have elongated and flexuous awns, measuring 0.29–0.45 mm and 0.18–0.41 mm, respectively (Fig. 1A2, 1B2, Table 2). In contrast, the awns of the Japanese C. pacificus var. pacificus are generally short and straight (0–0.24 mm), although a slightly curved form may occasionally occur in larger individuals (>20 cm) (Fig. 1C2, Table 2). Additionally, the Japanese C. pacificus var. margoinflatus has awns 0–0.06 mm in length, which are either absent or extremely short and straight (Fig. 1D2, Table 2).
The width of the marginal wing of the achene ranged from 0.05(0.06)–0.11 mm in C. michelianus, the Korean specimens, and Japanese C. pacificus var. pacificus (Fig. 1A3, 1B3, 1C3, Table 2). In contrast, it was measured 0.10–0.16 mm in Japanese C. pacificus var. margoinflatus, in which the wings were distinctly inflated, as described in the protologue (Fig. 1D3, Table 2).
DISCUSSION
Cause of the misinterpretation of C. michelianus in Korea
Based on detailed morphological examinations, all Korean specimens included in this study were identified as C. michelianus. Additionally, the glume arrangement and awn morphology were confirmed to be clear diagnostic characters for distinguishing C. pacificus from C. michelianus, consistent with the description of Ohwi (1944). This misinterpretation appears to have primarily resulted from the loss of three-dimensional morphological information during the specimen pressing process. Inflorescence organs or three-dimensional structures can lose or distort morphological information during specimen pressing, which may consequently lead to misinterpretation (Chater, 1996; Clarke and Moran, 2011; Sullivan and Nazaire, 2022). C. michelianus has glumes that are spirally arranged on both the abaxial and adaxial sides of the spikelet, resulting in a convex shape. During this study, we observed that spikelets in the flowering stage may have their spiral arrangement appear vaguely distichous when compressed on herbarium sheets (Fig. 2). Therefore, when distinguishing C. michelianus from C. pacificus in dried specimens, taxonomic identification should rely on characters that are less affected by pressing, particularly the length and characteristics of the awn, which are unlikely to be altered during the drying process.
Taxonomic identity of C. pacificus var. pacificus and var. margoinflatus in Korea
Some Korean floristic literature, particularly the description and illustration provided by Lee (1980), clearly depict the characteristics of C. pacificus, in which the glumes are arranged distichously with basal spiral orientation. Furthermore, this study did not examine all herbarium specimens deposited in every institution across the country. Therefore, it is premature to conclude that the taxon does not occur in the country or that C. pacificus is absent from Korea; thus additional investigation is required.
Cyperus pacificus generally exhibits greater morphological similarity to C. pygmaeus Rottb. than to C. michelianus, particularly in having a primarily distichous glume arrangement and relatively short awns. C. pygmaeus differs from C. pacificus in that it lacks marginal wings on the achene (Park et al., 2016). However, achenes are observable only during the fruiting stage, and identification therefore requires careful examination. These limitations complicate the distinction between C. pacificus and C. pygmaeus. Indeed, in this study, some specimens of C. michelianus were found mixed with C. pygmaeus on the same herbarium sheet (see specimens examined under C. michelianus), despite clear differences between these two taxa in the presence or absence of marginal wings on the achene. Therefore, some specimens deposited at the Korean Herbarium and identified as C. pygmaeus may correspond to C. pacificus.
In the case of C. pacificus var. margoinflatus, based on the results of this study, the only verified record in Korea is the specimen cited by Fujii (2016) (Korea, Seoul, Sept. 1901, U. Faurie 976, KYO). Thus, further field surveys are required to reassess the current distribution of this taxon in Korea.
TAXONOMIC TREATMENT
Cyperus michelianus (L.) Delile, Descr. Egypte, Hist. Nat. 2(Mém.): 50, 1813; Scirpus michelianus L., Sp. Pl.: 52, 1753.—TYPE: Tilli, Cat. Pl.: t. 20, f. 5, 1723 (lectotype: illustration!, designated by Simpson in Cafferty and Jarvis, 2004); Italy, Lombardia, Prov. di Mantova, juxta Padum (Po) ad Ponte di Borgoforte, 17 m, 19 Sep 1904, A. Fiori s.n., Flora Italica Exsicc., cur. Fiori, Béguinot and Pampanini no. 745 (epitype: BM, not seen, designated by Simpson in Cafferty and Jarvis, 2004). (Fig. 3)
Korean name: Na-seon-huin-bang-dong-sa-ni (나선흰방동사니).
Herbs, annual, caespitose. Roots fibrous. Stems 3.4–42 cm tall, roundly to slightly compressed-trigonous, smooth. Leaves 1–3 per culm; sheaths 1.1–10.7 cm long, pale pinkish-red to reddish-purple; blades 2.4–19.2 cm long. Bracts 3–8, leaf-like, 3.4–19.1 cm long, the lower 3–5 exceeding the inflorescence. Inflorescence capitate, ovoid to subglobose, rarely with 1–2 short branches, 0.5–1.5 × 0.5–2 cm. Spikelets narrowly elliptic to lance-ovate, slightly convex, 1.94–4.37 × 0.51–1.28 mm, 20–35-flowered. Glumes spirally arranged, vaguely distichous in pressed herbarium specimens, narrowly elliptic to narrowly oblong, 1.01–2.06 × 0.31–0.62 mm; awns flexuous, 0.18–0.45 mm long. Stamens 2; filaments 0.8–1.7 mm long; anthers oblong, 0.2–0.34 mm long. Stigmas 2–3-fid within the spikelet. Achenes narrowly oblong to lance-ovate, 0.75–1.03 × 0.21–0.36 mm, margins winged on both sides, wings 0.06–0.11 mm wide.
Flowering and fruiting: July to October.
Distribution: Widely distributed from Europe and the Mediterranean region through Central and South Asia to East and Southeast Asia, extending to Australia and New Guinea (Dai et al., 2010; POWO, 2025).
Distribution in the Republic of Korea: Widely distributed, except in Gangwon Province.
Diagnosis: Cyperus michelianus is morphologically similar to C. pacificus and C. pygmaeus, but is clearly distinguished by its glume arrangement and the length and characteristics of the awns. Cyperus michelianus has glumes spirally arranged over the entire spikelet, including both dorsal and ventral surfaces, and these are convex, while the awns are elongated and flexuous. In contrast, the glumes of C. pacificus and C. pygmaeus are distichous, and the awns are short and straight. However, in pressed and dried specimens, the spiral arrangement may become indistinct, so careful observation of awn characteristics is required.
Specimens examined: KOREA. Seoul: Mapo-gu, 10 Oct 2003, S. H. Park ParkSH32774 (KH). Incheon: Yeongjong-do, 28 Jul 2009, S. H. Park et al. ParkSH93402 (KH); Gyodong-do, 28 Aug 2024, T. H. Kim THKim10626, 10628, 10633, 10637 (HHU); Gyodong-do, 8 Oct 2024, T. H. Kim THKim10650 (HHU). Gyeonggi-do: Icheon-si, 4 Jul 2008, J. D. Jung 808040 (KB); Icheon-si, 12 Sep 2021, J. H. Kim 21-7005 (KB). Chungcheongnam-do: Hongseong-gun, 22 Sep 2016, J. H. Kim, J. H. An & H. J. Park LI16258 (KB); Asan-si, 23 Aug 2020, U. H. Eom CN201449 (KB); Asan-si, 10 Aug 2021, M. K. Lee N2021-280 (KB); Asan-si, 19 Aug 2024, T. H. Kim THKim10610, 10613, 10614, 10615, 10619 (HHU); Yesan-gun, 13 Sep 2022, M. K. Lee S2022-205 (KB). Gyeongsangbuk-do: Uiseong-gun, 25 Aug 2016, W. J. Lee US160825-1657 (KB); Uiseong-gun, 23 Jun 2018, G. S. Kim & M. K. Lee US181024 (KB); Gumi-si, 25 Oct 2015, J. U. Hwang 2015KNU-187 (KB); Yeongcheon-si, 11 Jul 2019, W. J. Lee et al. & Y. J. Jeong YC190491 (KB); Gyeongju-si, 4 Jul 2019, W. J. Lee et al. & Y. J. Jeong GJ19172 (KB). Daegu-si: Dalseong-gun, 15 Sep 2024, T. H. Kim THKim10638, 10639, 10640, 10645, 10647 (HHU). Jeollabuk-do: Gunsan-si, 23 Nov 2016, Y. S. Lim 2016-328 (KB); Gochang-gun, 25 Sep 2020, S. H. Hwang 2020-30219 (KB); Gochang-gun, 30 Sep 2022, Y. H. Cho & S. S. Kim WR20220730-010 (KB); Jeongeup-si, 21 Aug 2022, H. Cho & S. S. Kim WR20220821-017 (KB). Jeollanam-do: Gangjin-gun, 22 Aug 2008, Jongduk Jong 808045 (KB, mixed with C. pygmaeus on a sheet). Gyeongsangnam-do: Changwon-si, 18 Aug 2019, J. H. Kim 19-5522 (KB); Changnyeong-gun, 19 Aug 2006, S. H. Park & G. H. Nam ParkSH61462 (KH); Jinju-si, 7 Aug 2024, T. H. Kim THKim10601, 10602, 10604 (HHU); Jinju-si, 12 Oct 2024, T. H. Kim THKim10656, 10657 (HHU).
TAIWAN. Yunlin County: Mailiao, 7 May 2025, T. H. Kim & C. T. Chao THKim13004, 13005, 13006, 13007, 13008, 13009, 13010, 13011, 13012, 13013, 13014, 13015, 13016, 13017, 13018, 13019, 13020, 13021, 13022, 13023 (HHU).
Cyperus pacificus (Ohwi) Ohwi, Mem. Coll. Sci. Kyoto Imp. Univ., Ser. B, Biol. 18: 150. 1944; Cyperus michelianus var. pacificus Ohwi, Acta Phytotax. Geobot. 7: 137, 1938.—TYPE: JAPAN. Funakoshi in Ugo, 25 Sep 1931, S. Muramatsu s.n. (holotype: KYO!) (Fig. 4).
Herbs, annual, caespitose. Roots fibrous. Stems 1.1–32.5 cm tall, roundly to slightly compressed-trigonous. Leaves 1–3 per culm; sheaths 0.3–5.7 cm long, pale pinkish-red to reddish-purple; blades 1.4–14.8 cm long. Bracts 3–6, leaf-like, 1.4–12.2 cm long, the lower 2–5 exceeding the inflorescence. Inflorescence capitate, ovoid to subglobose, 0.4–1.3 × 0.5–1.5 cm. Spikelets narrowly elliptic to lance-ovate, flattened, sometimes bending forward or curving laterally, 1.63–6.61 × 0.41–1.31 mm, 15–37-flowered. Glumes primarily distichous, basally or on one side spirally, elliptic to narrowly oblong, 1.24–1.89 × 0.47–0.87 mm; awns 0–0.24 mm long, absent or short and straight, occasionally slightly curved in larger individuals (>20 cm). Stamens 2; filaments 0.6–1.4 mm long; anthers oblong, 0.19–0.32 mm long. Stigmas 2–3-fid within the spikelet. Achenes narrowly oblong to lance-ovate, 0.89–1.21 × 0.26–0.37 mm, margins winged on both sides, wings 0.05–0.16 mm wide.
Key to the varieties of Cyperus pacificus
1. Awns of glumes short and straight, rarely absent, and slightly curved in larger individuals (0–0.24 mm); marginal wings of the achene 0.05–0.11 mm wide ·· var. pacificus
1. Awns of glumes absent or extremely short (0–0.06 mm); marginal wings of the achene 0.10–0.16 mm wide and distinctly inflated ························· var. margoinflatus
Cyperus pacificus var. pacificus (Fig. 5).
Glumes primarily distichous, basally or on one side spirally, elliptic to narrowly oblong, 1.32–1.87 × 0.47–0.87 mm; awns short and straight, occasionally elongate and slightly curved in larger individuals (>20 cm), 0–0.24 mm long. Achenes narrowly oblong to lance-ovate, 0.89–1.21 × 0.26–0.37 mm, margins winged on both sides, wings 0.05–0.11 mm wide.
Flowering and fruiting: July to October.
Distribution: Korea (Yongsan) and Japan (Hokkaido; Honshu: Ibaraki, Gunma, Chiba, Niigata, Yamanashi prefectures, eastward from the Kinki region) (Nakai, 1911; Hoshino et al., 2011).
Diagnosis: C. pacificus var. pacificus is distinguished from taxa with distichously arranged glumes, such as C. pygmaeus and C. nipponicus Franch. & Sav., by the presence of marginal wings on the achene. In addition, because C. michelianus has spirally arranged glumes, it can be readily distinguished from this taxon in the field. However, in dried specimens, careful examination of features such as awn morphology is necessary for accurate identification.
Specimens examined: JAPAN. Hyogo Prefecture: Ono, 23 Sep 2025, T. H. Kim et al. THKim13201, 13203, 13204, 13205, 13206, 13207, 13208, 13210, 13211, 13213, 13214, 13215, 13217 (HHU); Akita Prefecture: Funakoshi in Ugo, 25 Sep 1931, S. Muramatsu s.n. (KYO, holotype of C. pacificus).
Cyperus pacificus var. margoinflatus S. Fujii, Acta Phytotax. Geobot. 67: 123. 2016.—TYPE: JAPAN. Osaka Pref., Izumi, Shinoda-yama, 15 Nov 1996, S. Fujii 5587 (holotype: OSA, not seen; isotypes: KYO!, MAK, not seen, TNS, not seen) (Figs. 6–7).
Korean name: Nal-gae-huin-bang-dong-sa-ni (날개흰방동사니; Korea National Arboretum, 2020).
Glumes primarily distichous, basally or on one side spirally, elliptic to narrowly oblong, 1.24–1.89 × 0.52–0.86 mm; awns absent or extremely short and straight, 0–0.06 mm long. Achenes narrowly oblong to lance-ovate, 0.89–1.21 × 0.26–0.37 mm, margins winged on both sides, distinctly inflated, wings 0.1–0.16 mm wide.
Flowering and fruiting: July to October.
Distribution: Korea (Seoul), Japan (Honshu: Tohoku, Kanto, Tokai, Kinki, Chugoku regions; Shikoku) (Fujii, 2016).
Diagnosis: Unlike the typical variety, C. pacificus var. margoinflatus is characterized by its smaller overall plant size and by distinctly inflated marginal wings on the achene, which measure 0.10–0.16 mm in width.
Specimens examined: JAPAN. Kagawa Prefecture: Mitoyo, 26 Oct 2019, S. Fujii 18458, 18459, 18760 (KYO); Takamatsu, 26 Oct 2019, S. Fujii 18758 (KYO); Takamatsu, 28 Nov 2020, S. Fujii 18896 (KYO); Hiroshima Prefecture: Higashi-Hiroshima, 8 Nov 2019, S. Fujii 18480 (KYO); Higashi-Hiroshima, 23 Sep 2025, T. H. Kim et al. THKim13101, 13102, 13103, 13104, 13105, 13106, 13107, 13108, 13109, 13110, 13111, 13112, 13113, 13114, 13115, 13116, 13117, 13118, 13119 (HHU); Kyoto Prefecture: Kameoka, 15 Nov 2019, S. Fujii 18433 (KYO); Osaka Prefecture: Izumi, Shinoda-yama, 15 Nov 1996, S. Fujii 5587 (KYO, isotype of C. pacificus var. margoinflatus).
PDF Links
PubReader
ePub Link
Full text via DOI
Download Citation 
Print 
