A taxonomic revision of Cenchrus L. (Poaceae) in Thailand, with lectotypification of Pennisetum macrostachyum Benth. Author Wessapak, Paweena Department of Botany, Faculty of Science, Kasetsart University, Chatuchak, Bangkok 10900, Thailand Author Ngernsaengsaruay, Chatchai Department of Botany, Faculty of Science, Kasetsart University, Chatuchak, Bangkok 10900, Thailand fsciccn@ku.ac.th Author Duangjai, Suthee https://orcid.org/0000-0002-1490-759X Department of Botany, Faculty of Science, Kasetsart University, Chatuchak, Bangkok 10900, Thailand text PhytoKeys 2023 2023-09-28 234 1 33 http://dx.doi.org/10.3897/phytokeys.234.106486 journal article http://dx.doi.org/10.3897/phytokeys.234.106486 1314-2003-234-1 175200BD8D535C96944C1AC7D5B29315 6. Cenchrus purpureus (Schumach.) Morrone in Chemisquy et al., Ann. Bot. (Oxford) 106: 129. 2010. Figs 10 , 11 Pennisetum purpureum Schumach., Beskr. Guin. Pl.: 44. 1827. Basionym. = Pennisetum macrostachyum Benth. in W. J. Hooker, Niger Fl.: 563. 1849, non (Brongn.) Trin. (1834). Type: Nigeria, Aboh, Vogel s.n. (lectotype, designated here: K [K000281312!]; isolectotype: K [K000281311!]). = Pennisetum flavicomum Leeke, Z. Naturwiss. 79: 46. 1907. Type: Tanzania, von Prittwitz & Gaffron 199 (holotype: B [B100167864] seen on digital image). = Pennisetum pruinosum Leeke, Z. Naturwiss. 79: 46. 1907. Type: Tanzania, Mtemere am Rufidji, W. Goetze 66 (holotype: B [B100167822] seen on digital image). = Pennisetum pallescens Leeke, Z. Naturwiss. 79: 47. 1907. Type: Togo, Nov 1902, O. Kersting 719 (holotype: B [B100167821] seen on digital image). Type . Ghana , P. Thonning 355 ( lectotype , designated by Hepper (1976 , pg. 149): C [C10004308!]; isolectotype BM n.v.) . Description. Perennial, tufted. Culms erect or ascending, 1.8-4 m high; nodes glabrous or hairy; internodes terete or subterete, 7-32 cm long, 2-10 mm in diam., glabrous. Leaf sheaths 9-20 cm long, glabrous. Ligules a fringe of hairs, 2-5 mm long. Collar glabrous. Leaf blades linear, 26-100 x 0.4-3(-3.5) cm, apex acute, base rounded glabrous or with tubercle-base hairs, margins scabrous, chartaceous, scabrous on both surfaces (sometimes hairy on upper surface). Inflorescence spiciform panicle, 45-80 x 2-4 cm (including bristles); central axis terete, 15-40 cm long, pubescent; peduncle terete, 25-55 cm long, glabrous or pubescent; short racemes along central axis; raceme with 1-4 spikelets in cluster, one sessile and the other pedicelled (if solitary, it is sessile or subsessile spikelet), pedicelled spikelets smaller than sessile spikelet; pedicels 0.5-2.2 mm long, scabrous; subtended by involucre bristles. Involucre composed of outer and inner circles, numerous and free at base, outer circle shorter than inner circle; outer involucre 2-4 mm long; inner involucre 1-1.4 cm long (sometimes up to 2.6 cm long), one conspicuous longest bristle 1.1-2.3 cm long, antrorsely scabrous; involucre falling with spikelets; stipe (raceme-based) 0.2-0.3 mm long, hairy, persistent on axis. Spikelets dorsally compressed, lanceolate, 4-6.5 x 0.8-1.3 mm. Lower glume ovate or lanceolate, 0.5-1.5 x 0.2-0.6 mm, apex acute or acuminate, sometimes obtuse, chartaceous, glabrous, nerveless or 2-obscure-nerved. Upper glume lanceolate or ovate-lanceolate, 1.8-4.2 x 0.4-1 mm, apex acute or acuminate, chartaceous, glabrous with or without scabrous along nerve, 1- or 3-nerved or nerveless. Lower floret male or sterile. Lower lemma lanceolate, 3-6 x 0.8-1.3 mm, apex acuminate, chartaceous, glabrous with or without scabrous along nerve, 3- or 5-nerved. Lower palea mostly absent or lanceolate, 4.5-5.2 x 0.8-1 mm, apex acute, margins fold with or without scabrous, membranous, glabrous, 2- or 3-nerved. Upper floret bisexual, persistent. Upper lemma lanceolate, 4-6.5 x 0.8-1.2 mm, apex acuminate, margins with ciliate, coriaceous, glabrous and scabrous near tip, 3- or 5-nerved. Upper palea lanceolate, 4.3-6.5 x 0.8-1.2 mm, apex acuminate, coriaceous, glabrous with or without scabrous near tip, 2-, 3- or 5-nerved. Lodicules absent. Stamens 3, filament 0.3-3 mm long, anther yellow, 1.5-2.8 mm long. Pistil ovary oblong-lanceolate, 0.6-1.5 x 0.1-0.5 mm; style 2, 1.5-4 mm long; stigma plumose, 2-6 mm long. Caryopsis ellipsoid, 1.5-2 x 0.8-1 mm. Figure 10. Cenchrus purpureus (Schumach.) Morrone A habit B ligule C spikelets with involucre D spikelet E lower glumes F upper glumes G lower lemmas H lower paleas I upper lemmas J upper paleas K stamens L pistil. (Drawn by Paweena Wessapak). Distribution. Native from Sahara to Tropical Africa and introduced to China, India, Myanmar, Indo-China, Malaysia, Australia, New Zealand, North America and South America. Distribution in Thailand. NORTHERN: Mae Hong Son (Pang Ma Pha, Mae Rim, Doi Suthep-Pui), Chiang Rai (Doi Tung, Mae Sai, Tham Luang-Khun Nam Nang Non), Lampang (Ngao); NORTH-EASTERN: Khon Kaen; EASTERN: Nakhon Ratchasima (Pak Chong), Si Sa Ket (Phrai Bueng); CENTRAL: Nakhon Pathom (Kampheangsaen); SOUTH-EASTERN: Chon Buri (Sattahip), Rayong (Klaeng); PENINSULAR: Surat Thani (Tha Chang), Krabi (Khlong Thom), Trang (Khao Chong), Songkhla (Sadao), Yala (Bannang Sata), Narathiwat (Sungei Kolok). Figure 11. Cenchrus purpureus (Schumach.) Morrone A habitat B culm with node rooting C inflorescence D spikelets with involucre E spikelets. (Photographs: Paweena Wessapak). Habitat and ecology. In open areas by the roadside, disturbed sites and the edge of deciduous forests. They are also cultivated for forage at elevations of 50-1350 m a.m.s.l. Flowering and fruiting from October to March. Vernacular name. Ya hang chang (หญ้าหางช้าง), Ya Napier (หญ้าเนเปียร์); Elephant grass, Napier grass (English). Specimens examined. Thailand . Chiang Mai : Doi Suthep-Pui , 23 Jan 1991 , J. F. Maxwell 91-95 (AAU); ibid., 1 Jan 2001 , J. F. Maxwell 01-1 (BKF, CMUB); Doi Suthep, 4 Nov 1958 , Th. Sorensen, K . Larsen & B. Hansen 2633 (BKF, C, K)]; ibid., 24 Dec 1965 , E. Hennipman 3478 (BKF, C); ibid., 19 Mar 1997 , K. Chayamarit & C. Pattanacharoen 732 (BKF); Mae Rim, 28 Nov 1995 , Anonymous 5378 (QBG); Mae Rim, Queen Sirikit Botanic Garden, 10 Feb 2006 , C. Glamwaewwong 463 (QBG) ; Chiang Rai : Doi Tung , Mae Fa Luang , 23 Dec 2006 , J. F. Maxwell 06-989 (QBG, CMUB); Mae Sai, Pong Pha, Ban Nam Cham, 2 Dec 2008 , M. Norsaengsri 4475 (QBG); Tham Luang-Khun Nam Nang Non, 13 Feb 2012 , M. Norsaengsri & N. Thatana 8876 (QBG) ; Chon Buri : Sattahip , 11 Oct 1969 , J. F. Maxwell s.n. (BK) ]; Khon Kaen : Khon Kaen University , 25 Dec 1997 , U. Pattaramanon 18 (KKU) ; Krabi : Khlong Thom , Khlong Thom Tai , 12 Nov 2011 , P. Wessapak 202 (BK) ; Lampang : Ngao , Ban Huat , 9 Dec 2014 , J. F. Maxwell 14-19 (CMUB, PSU) ; Mae Hong Son : Pang Ma Pha , Ban Tha Khrai , 16 Feb 2005 , K. Pruesapan KP2005-9 (BK) ; Nakhon Pathom : Kampheangsaen , 28 Dec 2016 , P. Wessapak 348 , 350 (BK) ; Nakhon Ratchasima : Pak Chong , Oct 1931 , A. F. G. Kerr s.n. (BM, BK) ; Narathiwat : Sungei Kolok , Nikhom Waeng , 6 Mar 1974 , K. Larsen & S. S. Larsen 33030 (AAU, BKF, K) ; Rayong : Klaeng , Chak Pong , Ban Phlong Sawai , 13 Jan 2009 , P. Wessumritt & M. Norsaengsri 160 (QBG) ; Si Sa Ket : Phrai Bueng , Suk Sawat , 26 Dec 2004 , A. Virapongse 194 (BKF) ; Songkhla : Sadao , Samnak Taeo , 24 Oct 2010 , P. Wessapak & C. Ngernsaengsaruay 153 (BK, BKF); 11 Nov 1959 , T. Smitinand 6124 (BKF) ; Surat Thani Tha Chang , Tha Koei , Ban Thong Sai , 2 Nov 2011 , P. Wessapak 200 (BK) ; Trang : Khao Chong , 18 Nov 1990 , K. Larsen , S. S. Larsen , M. S. Barfod , W. Nanakorn , W. Ueachirakan & P. Sirirugsa 41606 (AAU, BKF, PSU) ; Yala : Bannang Sata , 12 Dec 1961 , Ploenchit 1775 (BKF) . Notes. Napier grass is a multipurpose forage crop. It is mainly used to feed livestock and is also used for ornamentation and soil erosion control. Its fibres are used to make pulp and in papermaking. Furthermore, its biofuel producing potential is being researched because all the parts of this species produce lignocellulose biomass which can be used to produce cheap biofuel ( Obi Reddy et al. 2014 ; Chavre and Sonawane 2021 ). This species was introduced to Thailand from Malaysia for forage. At present, it has become naturalised to almost all Thai floristic regions. The synonym, Pennisetum macrostachyum , was described by George Bentham in 1849 and is based on the Vogel's specimens from Aboh (Nigeria) and Fernando Po (Equatorial Guinea). He did not choose any specimens to be the holotype. We located the Vogel's specimen in three sheets at K which was collected from Aboh (Nigeria) [K000281311 and K000281312] and Fernando Po (Equatorial Guinea) [K000281310] and, according to Art 9.6 of the ICN ( Turland et al. 2018 ), they constitute syntypes. The sheet K000281312 is a well-preserved specimen with more leaves and spikelets and, therefore, it is herein designated as the lectotype for the synonym P. macrostachyum . (Fig. 12 ) Figure 12. Lectotype of Pennisetum macrostachyum Benth. Digital image The Board of Trustees of the Herbarium of the Royal Kew Botanic Garden (K).