Agrostis tsomgoensis D.Prasad & P.Agnihotri, 2025

Prasad, Dileshwar, Tiwari, Smita, Sharma, Sangam, Yadav, Rekha & Agnihotri, Priyanka, 2025, Agrostis tsomgoensis (Poaceae, Agrostidinae) -- a new pooid grass species from Sikkim Himalaya, India, Phytotaxa 706 (2), pp. 163-170 : 164-168

Agrostis tsomgoensis D.Prasad & P.Agnihotri , sp. nov. ( Figs. 1 & 2 )

Diagnosis:— The new species differs from A. clavata and A. scabra by its longer length of palea (0.6–0.75 mm vs. 0.22–0.25 mm and 0.27–0.33 mm, respectively), higher ratio of palea length to lemma length (0.47–0.58 vs. 0.18–0.20 and 0.20–0.22, respectively), and callus hairs (absent vs. rarely present with hairs 0.02–0.2 mm long and 0.2–0.3 mm long, respectively), and from A. micrantha by its leaf blade width (1.8–2.5 mm vs 2.5–6.0 mm), glumes (unequal vs subequal to equal), lower glume length (2.3–3.0 mm vs 1.0–2.0 mm), and lower ratio of lemma length to lower glume length (0.48–0.54 vs 0.90–0.96).

Type:— INDIA. Sikkim, East Sikkim, near Tsomgo lake, 27.374N, 88.752E, 3718 m, 11 Aug. 2021, D.Prasad, R.Yadav & S.Sharma 314447 (holo. LWG! iso. LWG!).

Description:— Perennial, loosely tufted grass, 20–28 cm high. Culms 15–22 cm long, terete, smooth, 2-3 nodes below the panicle. Nodes glabrous, compressed. Leaf sheaths split-overlapping, connate at 2/3 rd of their length from base, glabrous, basal sheath persistent. Leaf blades (topmost leaf blade measured) 4.5–6.0 cm long, 0.18–0.25 cm wide, linear, abaxial surface sparsely scabrous, adaxial surface scabrous with ribbed. Ligules 1.5–2.0 mm long, membranous, adaxial and abaxial surface glabrous; apex blunt, truncate; collar glabrous. Inflorescences a panicle, 5–12 cm long, lax, open or sometimes lower part closed in sheath, spreading; lower branch in whorls of 3 or 5, 4.0–6.0 cm long, sparsely scabrous, spiculate in upper 1/3–1/2. Rachis slender, smooth. Pedicels 2.5–3.5 mm long, scaberulous. Spikelets 2.3– 3.0 mm long, 1.0– 1.5 mm wide, elliptic, closed to mature become open, greenish-purplish,1-flowered, disarticulating above the glumes and below the floret; glumes unequal; floret bisexual. Lower glumes 2.3–3.0 mm long, 0.60–0.75mm wide, 1-nerved, 1-keeled, lanceolate, greenish to purplish-hyaline toward margin, surface glabrous; apex acuminate; margin entire; keel scabrid. Upper glumes 1.9–2.5 mm long, 0.65–0.75 mm wide, 1-nerved, 1-keeled, lanceolate, greenish to purplish-hyaline toward margin, surface glabrous; apex acuminate; margin entire; keel scaberulous on upper half; ratio of upper glume length to lower glume length 0.78–0.90. Callus glabrous. Lemmas 1.1–1.5 mm long, 0.8–1.1 mm wide, 5-nerved, elliptic, membranous, surface smooth, not awned; apex obtuse; ratio of lemma length to lower glume length 0.47–0.52. Paleas 0.6–0.75 mm long, nerveless, membranous-hyaline; ratio of palea length to lemma length 0.47–0.58. Stamens -3, anthers 0.33–0.66 mm long.

Flowering and fruiting:— August to September.

Habitat and distribution:— Agrostis tsomgoensis is known only from its type locality, which is Tsomgo Village, near Lake, East Sikkim ( Fig. 3). It was found growing in moist alpine meadows, on mountain slopes ; at about 3700 m a.s.l.

Etymology:— The specific epithet “ tsomgoensis ” refers to the type locality where the new species is known: Tsomgo, Sikkim.

Taxonomic notes:— A group of species in the genus Agrostis is distinguished by callus glabrous, or sometimes shortly hairy, lemma glabrous and unawned and palea very minute to half as long as lemma, or sometimes absent. In South-East Asia, this group is represented by A. clavata , A. micrantha Steud. (1854: 170) , A. nervosa Nees ex Trinius (1841: 329) , A. scabra Willdenow (1797: 370) , and A. sikkimensis Bor (1954: 502) . Of which, A. scabra has not been reported in the Himalayan regions (Poszko & Liu 2016). Agrostis tsomgoensis appear to be closely related to A. clavata and A. scabra than A. micrantha based on morphology, particularly habit and panicle. The morphological similarities and differences between A. clavata , A. micrantha , A. scabra and A. tsomgoensis are presented in the diagnosis and Table 1. Agrostis micrantha , widely distributed across the pan-Himalayas ( Hooker 1896, Bor 1960, Rajbhandari 1985, Lu & Phillips 2006), was also known under the names A. himalayana Bor (1953: 269) and A. myriantha Hook.f. (1896: 257) , the latter both noted as leafy and robust form of A. micrantha . However, A. micrantha always has 2.5–6.0 mm wide leaf-blade and shorter spikelets, never exceeding over 2 mm long, that clearly differentiate it from A. tsomgoensis . Agrostis nervosa is also somewhat related to A. tsomgoensis , as the former is characterized by having caespitose habit, relatively longer ligules, and minute or lacking palea, lower glume 2.37–3.2 mm long, upper glumes 2.0– 2.9 mm long, lemma 1.2–2.3 mm long and anthers 0.5–0.75 mm long, but the palea will always settle the identity. The dwarf grass, A. sikkimensis , endemic to Sikkim, differs from A. tsomgoensis by having divaricated branchlet in panicle, spikelets about 1.75 mm long and palea shorter than half of the length of lemma ( Bor 1960, Rajbhandari 1985).

Additional specimens examined:— Agrostis clavata : INDIA. Sikkim, East Sikkim, Nathula Pass , 27.3859N, 88.8294E, 4200 m, 11 Aug. 2021, D Prasad, R Yadav, P Rajput & S Sharma 314869 ( LWG!) ; near Tsomgo Lake , 27.3772N, 88.7670E, 3850 m, 11 Aug. 2021, D Prasad, R Yadav, P Rajput & S Sharma 314850 ( LWG!) ; A. micrantha : INDIA. Jammu & Kahsmir, Ramban , 6,500 ft [1981.2 m], 12 May 1939, NL Bor 25 ( DD!) ; Himachal Pradesh, Lahul and Spiti, Lahul , Keylong , 10,000 ft [3048 m], 13 Jul. 1938, NL Bor 9242 ( DD!) ; Lahul and Spiti, Lahul , Keylong , 10,300 ft [3139.44 m], 02 Aug. 1941, NL Bor s.n. ( DD!) ; Uttarakhand, Tehri Garhwal, Chitora , 11,000 ft [3352.8 m], 29 Sept. 1948, Walter N Koelz 22048 ( DD!) ; Chamoli, Govindghat , 30.618486N, 79.5581541E, 2200 m, 22 Aug. 2019, P Agnihotri, D Prasad, S Jaiswal & R Yadav 326699 ( LWG!) ; Sikkim, East Sikkim, Kupup , 13,000 ft [3962.4 m], 03 Sept. 1945, NL Bor 644 ( DD!) ; Gangtok, Dikchu , 2,000 m, SK Mukerjee 4990 ( CAL!) ; without precise locality, 1878, King s.n. ( CAL!); West Bengal, Darjeeling, Tonglu , 21 Sept. 1957, PC Nanda s.n. ( CAL!) ; Brich Hills , 6,500ft [1981.2 m], 16 Jun. 1960, s.cl. s.n. ( CAL!) ; Tonglu , 10,000ft [3048 m], 21 Sept. 1958, BD Patil 1248, 1242 ( CAL!) ; Lopchu , 22 Sept. 1957, PC Nanda 7267 ( CAL!) ; Rongbang , 20 Sept. 1957, BD Patil 1231 ( CAL!) ; Meghalaya, Shillong, Khasia , 6,000ft [1828.8 m], JD Hooker & JJ Thomson s.n. ( CAL!) ; Shillong , 01 Jun. 1937, GK Daka 13994 ( CAL!) ; on the way to Mairang , 25.487116N, 91.754397E, 1760 m, 12 Oct. 2022, D Prasad 337271 ( LWG!) ; Arunachal Pradesh, Dibang Valley, Chitapani camp, 1990 m, 28 Jun. 2002, M Bhaumik & MK Pathak 4069 ( CAL!) ; Dibang Valley, Pasupani Camp , 2100 m, sandy rocky soil, 30 Jun. 2002, M Bhaumik & NK Pathak 4096 ( CAL!) ; Nagaland, Naga Hills , 5,000 ft [1524 m], 06 Aug. 1942, NL Bor 1629 ( DD!) ; Naga Hills , 1935, NL Bor s.n. ( DD!) ; without precise locality, 8,000ft [2438.4 m], 19 Aug. 1910, WW Smith 4420 ( CAL!) .

Figures

FIGURE 1. Agrostis tsomgoensis, sp. nov.: A. Basal sheath, B. Node, C&D. Ligules, E. Collar, F. Upper part of lower panicle branch, G. Spikelet, H. Spikelet with removed floret, I. Floret, J. Lemma, dorsal view, K. Lemma, ventral view, L. Anthers.

FIGURE 2. Agrostis tsongoensis, sp. nov.: A. Habit, B. Ligule, C. Part of lower panicle branchlet, D. Spikelet, E. Floret, F. Lemma, G. Palea, H. Anthers.