Cenchrus setosus Sw., Prodr.: 26. 1788.

Wessapak, Paweena, Ngernsaengsaruay, Chatchai & Duangjai, Suthee, 2023, A taxonomic revision of Cenchrus L. (Poaceae) in Thailand, with lectotypification of Pennisetum macrostachyum Benth., PhytoKeys 234, pp. 1-33 : 1

7. Cenchrus setosus Sw., Prodr.: 26. 1788.

Figs 13 , 14

≡ Pennisetum setosum (Sw.) Rich, Syn. Pl. 1: 72. 1805.

≡ Pennisetum polystachion (L.) Schult. subsp. setosum (Sw.) Brunken, Bot. J. Linn. Soc. 79(1): 63. 1979.

Type.

Jamaica, O. Swartz s.n. (lectotype, designated by Hitchcock (1908, pg. 143): S [S-R-969] seen on digital image; isolectotypes: BM [BM000938799!], G [G00168094], S [S-R-968, S06-637] seen on digital images) .

Description.

Annual or perennial, tufted. Culms erect or ascending, 0.5-3 m high; nodes glabrous; internodes subterete, sometimes slightly flattened, 5.5-34 cm long, 1-8 mm in diam., glabrous. Leaf sheaths 0.7-2.5 cm long, glabrous. Ligules ciliate membrane, 1.5-3 mm long. Collar ciliate or hairs 1-2 mm long. Leaf blades linear, 10-85 × 0.4-2.2 cm, apex acute, base rounded with tubercle-base hairs, margins scabrous, chartaceous, hairy on both surfaces. Inflorescence spiciform panicle, 22-55 × 1.5-4.5 cm (including bristles); central axis with shortly decurrent ribs, 12-23 cm long, scabrous or almost glabrous; peduncle terete, 10-35 cm long, scabrous or almost glabrous or glabrous; short racemes along central axis; raceme with solitary sessile spikelet subtended by an involucre bristle. Involucre composed of outer and inner circles, numerous and free at base, outer circle shorter than inner circle; outer involucre 1-5 mm long; inner involucre 1-1.4 cm long, one conspicuous longest bristle 1.2-3.3 cm long, antrorsely scabrous and hairy. Involucre falling with spikelet; stipe (raceme-based) absent. Spikelets dorsally compressed, lanceolate, 3.3-4.5 × 0.8-1.2 mm. Lower glume absent, minute ca. 0.1 mm long or triangular, 0.5-0.8 × 0.1-0.6 mm, apex acute, membranous, nerveless. Upper glume lanceolate, 3.3-4.5 × 0.8-1.2 mm, apex acuminate or mucronate, membranous, glabrous or slightly scabrous, 5-nerved. Florets 2. Lower floret male or sterile. Lower lemma lanceolate-elliptic or lanceolate, 2.8-3.5 × 0.8-1.2 mm, apex trifid, membranous, glabrous or slightly scabrous, 3- or 5-nerved. Lower palea oblong or oblong-lanceolate, 2.2-3.2 × 0.3-0.8 mm, apex acute, margins folded, membranous, glabrous, 2 or 3-nerved or nerveless, sometime palea absent. Upper floret bisexual, caducous. Upper lemma lanceolate, 1.9-2.5 × 0.4-0.8 mm, apex obtuse with ciliate, coriaceous, glabrous, nerveless or 5-obscure-nerved. Upper palea lanceolate, 1.9-2.5 × 0.3-0.8 mm, apex obtuse with ciliate, coriaceous, glabrous, nerveless or 5-obscure-nerved. Lodicules absent. Stamens 3; filament 1-1.5 mm long; anther yellow or brown 1.3-2.2 mm long. Pistil ovary oblong or elliptic, 0.3-0.6 × 0.1-0.2 mm; style 2, 1-2 mm long; stigma plumose, 2-3 mm long. Caryopsis ellipsoid, 1.2-1.7 × 0.5-0.8 mm.

Distribution.

Native to India and Tropical Africa and introduced to Indo-China, Malaysia, Australia, North America and South America.

Distribution in Thailand.

NORTHERN: Chiang Mai (Doi Saket, Mae Ya Waterfall, Chom Thong, Mae Rim, Doi Chiang Dao, Hang Dong), Chiang Rai (Mae Chan, Mae Sai, Mueang Chiang Rai), Phrae (Song), Nan (Tham Sa Koen), Lampang (Doi Luang), Phitsanulok (Thung Salaeng Luang), Kamphaeng Phet (Pang Sila Thong); NORTH-EASTERN: Phetchabun (Nam Nao), Loei (Phu Ruea, Wang Saphung), Udon Thani (Kumphawapi), Khon Kaen (Waeng Yai, Phu Wiang, Nam Nao); EASTERN: Nakhon Ratchasima (Pak Thong Chai, Sakaerat, Pak Chong, Khao Yai), Buri Ram (Chaloem Phra Kiat), Ubon Ratchathani (Phu Chong Na Yoi); SOUTH-WESTERN: Kanchanaburi (Thong Pha Phum); CENTRAL: Saraburi (Wang Muang), Nakhon Pathom (Phutthamonthon), Nakhon Nayok (Khao Yai), Samut Prakan (Phra Pradaeng); SOUTH-EASTERN: Prachin Buri (Kabin Buri), Chon Buri (Si Racha, Ban Bueng), Rayong (Klaeng), Chanthaburi (Tha Mai, Khlong Nong Khla, Laem Sadet), Trat (Ko Chang); PENINSULAR: Surat Thani (Chaiya), Phuket (Thalaeng), Krabi (Ao Ma Ya, Khlong Thom), Nakhon Si Thammarat (Thung Song, Tha Yang), Phatthalung (Phanang Tung), Trang (Sikao), Satun (Mueang Satun), Songkhla (Hat Yai, Khao Phra, Rattaphum, Sadao, Na Mhom).

Habitat and ecology.

In open areas by the roadside, disturbed and open areas in deciduous forests at elevations between 0 and 1200 m a.m.s.l. Flowering and fruiting throughout the year.

Vernacular name.

Ya kha chon chop (หญ้าขจรจบ), Ya kha chon chop dok lek (หญ้าขจรจบดอกเล็ก), Ya kha chon chop dok lueang (หญ้าขจรจบดอกเหลือง); Mission grass (English).

Specimens examined.

Thailand. Buri Ram: Chaloem Phra Kiat, Isan Khet, 21 Oct 2017, P. Wessapak 410 (BK); Chanthaburi: Tha Mai, 2 Jan 1971, S. Sutheesorn 1947 (BK); ibid., 8 Nov 1971, S. Sutheesorn 2017 (BK); Tha Mai, Khlong Nong Khla, 16 Feb 2009, M. Norsaengsri 4894 (QBG); Tha Mai, Laem Sadet, 24 Feb 2008, M. Norsaengsri & K. Wangwasit 3487 (BKF, QBG); Chiang Mai: Chom Thong, 3 Dec 1991, J. F. Maxwell 91-1092 (AAU); Doi Chiang Dao, 21 Nov 1999, P. Suksathan 2221 (QBG); Hang Dong, 21 Mar 2009, S. Watthana 3007 (QBG); Doi Saket, Ban Pang Faen, 10 Dec 1998, F. Konta & S. Khao-Iam 4421 (BKF); Mae Rim, 3 Oct 1994, W. Nanakorn et al. s.n. (QBG); Mae Ya Waterfall, 15 Dec 1998, F. Konta, C. Phengklai & S. Khao-Iam 4529 (BKF); Chiang Rai: Mae Chan, 20 Jan 1981, Y. Paisooksantivatana y492-81 (BK, CMUB, KKU); ibid., 1 Dec 2008, M. Norsaengsri 4470 (QBG); Mae Sai, Pong Pha, Ban Nam Cham, 2 Dec 2008, M. Norsaengsri 4477 (QBG); Mueang Chiang Rai, Ban Pa Rai, 24 Jan 1981, Y. Paisooksantivatana 561-81 (BK); Chon Buri: Ban Bueng, 3 Jun 1989, Y. Paisooksantivathana 2327-89 (BK); Si Racha, Thung Sukhla, 8 Dec 2003, J. F. Maxwell 03-482 (CMUB); Kamphaeng Phet: Pang Sila Thong, 13 Nov 2007, M. Norsaengsri 2986 (QBG)]; Kanchanaburi: Thong Pha Phum, 15 Nov 1971, C. F. van Beusekom, C. Phengklai, R. Geesink & B. Wongwan 3788 (BKF, C, K, P); Thong Pha Phum, Huai Khayeng, Bueng Nam Thip, 3 Dec 2003, S. Sirimongkol 67 (BKF); Thong Pha Phum, Pilok, 23 Oct 2004, S. Sirimongkol 164 (BKF); Khon Kaen: Nam Nao, 10 Mar 1979, P. J. O’Corner & C. Niyomdham 15724 (AAU, BKF); Phu Wiang, 21 Feb 1993, P. Chantaranothai, D. Middleton, J. Parnell & D. Simpson 826 (K, KKU); Phu Wiang, Khok Phu Ta Ka, 30 Nov 2003, C. Jaroenchai 37 (KKU); Waeng Yai, 26 Dec 2007, M. Norsaengsri 3255 (AAU, CMUB, QBG); Waeng Yai, Ban Khao Nai, 7 Nov 2008, M. Norsaengsri 4384 (QBG); Krabi: Ao Ma Ya, 24 Nov 1998, C. Niyomdham 5646 (BKF); Khlong Thom, Khlong Phon, 29 Nov 1986, J. Supapol 288 (PSU); Khlong Thom, Khlong Thom Tai, 29 Oct 2011, P. Wessapak 196, 197 (BK, BKF)]; Lampang: Doi Luang, 12 Dec 1998, O. Petrmitr 400 (BKF, CMUB); Loei: Phu Ruea, 6 Dec 2004, C. Jaroenchai 133 (KKU); ibid., 27 Nov 2005, C. Jaroenchai 163 (KKU), ibid., 12 Nov 2005, C. Jaroenchai 210 (KKU), ibid., 13 Nov 2005, C. Jaroenchai 228 (KKU); ibid., 27 Nov 2005, C. Jaroenchai 245 (KKU); Wang Saphung, 26 May 2009, M. Norsaengsri & W. La-ongsri 5560 (QBG)]; Nakhon Nayok: Khao Yai, Hin Tung, 23 Jan 2002, J. F. Maxwell 02-35 (BKF, CMUB)]; Nakhon Pathom: Phutthamonthon, Salaya, 22 Nov 2002, J. F. Maxwell 02-418 (BKF, CMUB); Nakhon Ratchasima: Khao Yai, 23 Oct 1970, T. Smitinand 11040 (BKF); Pak Chong, 14 Jan 1965, Umpai 173 (BK); Pak Thong Chai, Nov 1970, Ch. Charoenpol, K. Larsen & E. Warncke 4535 (C); Sakaerat, 4 Dec 1983, N. Fukuoka & M. Ito T-35013 (BKF); Nakhon Si Thammarat: Tha Yang, Thung Yai, 2 Nov 2011, P. Wessapak 201 (BK); Thung Song, 18 Dec 1965, J. Sadakorn 2 (BK); Nan: Tham Sa Koen, 30 Nov 2011, W. La-ongsri, M. Norsaengsri, P. Panyachan, P. Tatiya & S. Satatha 2002 (QBG, PSU); Phatthalung: Phanang Tung, Khuan Khanun, 2 Dec 2012, P. Na Sawat 2 (PSU); Phitsanulok: Thung Salaeng Luang, 25 Jul 1973, G. Murata, N. Fukuoka & C. Phengklai T-17144 (BKF); ibid., 21 Oct 1984, G. Murata, C. Phengklai, S. Mitsuta, T. Yahara, H. Nagamasu & N. Nantasan T-38399 (BKF)]; Phetchabun: Nam Nao, 25 Oct 2001, S. Laegaard & M. Norsaengsri 21787 (AAU, BKF, QBG); Phrae: Song, Mae Yom, 10 Nov 1991, J. F. Maxwell 91-1003 (AAU); Phuket: Thalaeng, Thep Kasattri, Ban Mai Kao, J. Supapol 100 (PSU); Prachin Buri: Kabin Buri, 13 Feb 2009, M. Norsaengsri 4854 (QBG); Rayong: Klaeng, 15 Feb 2009, M. Norsaengsri 4877, 4891 (QBG); Klaeng, Chak Don, 18 Nov 2008, P. Wessumritt & M. Norsaengsri 147, 148 (QBG); Samut Prakan: Phra Pradaeng, Song Khanong, 25 Mar 2012, P. Wessapak & C. Ngernsaengsaruay 204 (BK); Saraburi: Wang Muang, Kham Phran, 1 Dec 2011, P. Wessapak 203 (BK); Satun: Mueang Satun, Phi Man, 24 Oct 2010, P. Wessapak & C. Ngernsaengsaruay 154 (BK, BKF); Songkhla: Hat Yai, 2 Feb 1979, G. Congdon 247 (AAU, PSU); Hat Yai, Ban Nong Bua, 3 Jul 2012, S. Aya 26 (PSU); Hat Yai, Khao Kho Hong, 24 Oct 2010, P. Wessapak & C. Ngernsaengsaruay 151 (BK, BKF); Khao Phra, 28 May 2001, A. Boonprom 1 (PSU); Na Mhom, Klong Rhang, 23 Nov 2016, P. Wessapak, C. Ngernsaengsaruay, N. Meeprom & W. Boonthasak 344, 345 (BK);Rattaphum, Ban Khao Rak Kiat, 15 Oct 2012, K. Jamnongjit 27 (PSU); Sadao, Samnak Taeo, 9 Jan 2014, H. Soh 36 (PSU); Surat Thani: Chaiya, Pak Mak, 2 Nov 2011, P. Wessapak 198 (BK); Chaiya, Pa We, 2 Nov 2011, P. Wessapak 199 (BK, BKF); Trang: Sikao, Mai Fat, Ban Khuan Hen Le, 27 Oct 2011, P. Wessapak 195 (BK, BKF); Trat: Ko Chang, Ban Khlong Son, 22 Mar 2001, K. Chayamarit, T. Wongprasert, R. Pooma, V. Chaemchumroon, K. Pattarahirankanok & M. Newman 2735 (BKF)]; Ubon Ratchathani: Phu Chong Na Yoi, Phalan Kong Kwian, 6 Nov 2010, P. Wessapak, Y. Buangam & W. Sareemongkonnimit 159 (BK)]; Udon Thani: Kumphawapi, Huai Koeng, 4 Dec 2008, M. Norsaengsri 4582 (QBG).

Notes.

This species was introduced to Thailand from India and Philippines as a fodder grass. At present, it has become a major weed and naturalised throughout the country.

Previously, this species was identified as Pennisetum polystachion (L.) Schult. The name was established by J. A. Schultes in 1824, based on the basionym Panicum polystachion L. After the genera were combined, based on the molecular phylogenetic studies ( Donadío et al. 2009; Chemisquy et al. 2010), Pennisetum was merged into Cenchrus . The name of this species in Cenchrus is Cenchrus polystachios (L.) Morrone coined by Morrone in Chemisquy et al. (2010). Turner et al. (2019) reported that the lectotypification of the basionym Panicum polystachion L. by Merrill in 1917 was based on the plate cited by Linnaeus, which is identified as Setaria flava (Nees) Kunth. (now treated as a synonym of Setaria parviflora (Poir.) Kerguélen). Therefore, the name of Cenchrus , based on Panicum polystachion L., is not correct. The correct name of this species is considered as Cenchrus setosus Sw., which has the next priority.

Figures

Figure 13. Cenchrus setosus Sw. A habit B ligule C spikelet 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 M caryopsis. (Drawn by Paweena Wessapak).

Figure 14. Cenchrus setosus Sw. A habitat B inflorescences C spikelet with involucre. (Photographs: Paweena Wessapak).