Checklist of the orchids of Nokrek Biosphere Reserve, Meghalaya, India

: A study on the diversity and distribution of different orchid species in Nokrek Biosphere Reserve (NBR) was carried out from 2009 to 2015 with an objective to assess the threatened plants present in protected areas. A total of 127 species of orchids belonging to 56 genera were identified from NBR; out of which 94 are epiphytes or lithophytes, 32 are terrestrial, and one species is mycoheterotrophic. Dendrobium (21 spp.) is the most dominant genus in terms of the species composition, followed by Bulbophyllum (8 spp.), Coelogyne (8 spp.), Liparis (7 spp.), Cymbidium (5 spp.), and Pinalia (4 spp.). Other dominant genera include Aerides , Agrostophyllum , Cleisostoma , Habenaria , Micropera , Paphiopedilum , and Pholidota which were represented by three species each. A total of 10 genera were recorded that were represented by two species include Acampe , Cryptochilus , Dendrolirium , Gastrochilus , Oberonia , Peristylus , Phalaenopsis , Pleione , Spathoglottis , and Vanda . Of the recorded species from NBR, the Gastrochilus calceolaris is assessed by the IUCN Red List as ‘Critically Endangered’, Paphiopedilum insigne and P. venustum are ‘Endangered’, P. Hirsutissimum as ‘Vulnerable’, and Dendrobium aphyllum as ‘Least Concern’. It has been observed that at the higher elevations, subtropical and temperate forests provide a conducive environment for the orchids to occupy a pristine ecosystem because the temperature and maximum humidity recorded in those areas is lower in comparison to lower regions. This research finding recommends the designation of Nokrek hill as a permanent orchid sanctuary for germplasm collection and conservation, as it could better guarantee the survival of threatened plants and reduce human interventions in the forested zone.


INTRODUCTION
Nokrek Biosphere Reserve (NBR) popularly called 'the Achik land' in the Garo language, located between 25. 25-48°N and 90.22-90.50°E, was established on 13 September 1988 in the Garo district of Meghalaya State (Singh & Borthakur 2015). It occupies a geographic area of 820 km² in the state with 47.48 km² designated as Nokrek National Park. UNESCO added this biosphere reserve to its list in 2009 under Man & Biosphere (MAB) program, as it consists of three mountains, viz., Tura range, Arbella range, and Ranggira range (Singh 2015a,b). The well-recognized mountain peaks located in NBR includes Nokrek peak (1,412 m), followed by Arbella peak (999 m), Tura peak (872 m), and Ranggira peak (673 m); other important peaks are Meminram hill, Nengminjok hill, and Chitmomg hill (Singh et al. 2018). These mountainous belts are mainly composed of hilly granitic mass and compact block of hilly ranges having deep slopes and valleys with most of the ranges being more than 500 m. These mountain peaks are considered as an important source of several rivers and streams. The region is categorized as having a monsoon climate with temperature ranging 9.5-37.3°C. The climate as a whole is controlled by the south-west monsoon and seasonal winds; south-west and north-east monsoons are responsible for rainfall to the area ranging 3,900-6,800 mm/year (Singh et al. 2012a,b,c). It has been observed that the great heterogeniety in the ecologically rich ecosystem and the high range of altitudinal variations in the study area are responsible for the luxuriant, rich, and diverse vegetation of NBR (Singh 2015). Olson et al. (2001) categorized these mountain belts under the Indo-Malayan eco-region with the major vegetation types as the mixed tropical forests and subtropical forests (200-1,400 m), and small patches of temperate forests (above 1,400 m) at the higher mountains.
The Nokrek flora is the remnant of Indo-Malayan forests (Image 1), and the dense forests of these mountains provide a home to many narrowly endemic unique species of phytogeographical significance (Singh et al. 2011). The vegetation in many areas of the forests of Nokrek and adjoining areas has declined and plants are becoming threatened due to biotic pressure (Image 2). For instance, wild Citrus indica L., insectivorous plant Nepenthes khasiana Hook.f., the slipper orchids Paphiopedilum Pfitzer spp., Blue Vanda Vanda coerulea Griff. ex Lindl., which used to be common in Nokrek and Khasi mountains, are becoming rare and threatened due to illicit collection and destruction of virgin forests (Image 3). Considering the immense need for conservation of these unique species, the area needs research and protection from human interference.
Plant species diversity contributes to ecosystem health, and each species is like a thread holding together an ecosystem (Mir et al. 2022). Therefore, if a species disappears, an entire ecosystem can start to unravel. The rapid loss in orchid diversity and the changing pattern of forest compositions due to various biotic and abiotic factors in Meghalaya have necessitated the qualitative and quantitative assessment of vegetation. However, numbers of floristic studies on community dynamics and phytogeographic affinities have been conducted qualitatively as well as quantitatively in northeastern India (Singh 2015a); there are a few studies incorporating orchid diversity (Singh & Borthakur 2015). However, no studies are available that give a detailed account of orchid diversity of Nokrek as NBR is less explored from the floristic point of view. Therefore, this work (i) emphasizes the need to study and explore the diversity of orchid species in NBR, (ii) collect samples and identify the tree species where orchid plants grow, and (iii) identify the localities rich in orchid diversity for conservation and management for local use.

Field Survey, Orchid Collection, and Identification
Eleven field surveys were carried out from 2009 to 2015 along 57 forest trails of NBR, including buffer and core zones. Nokrek peak, Tura peak, Ranggira peak, Daribokgre, Neingmandalgre, Rongrengre, Chokpot, and other similar adjoining areas were selected as prioritized areas for frequent field surveys and exploration of plant diversity. The living samples were collected for those nonflowering samples and as herbarium vouchers for both non-flowering and flowering samples. During the period of study, the live orchids collected were introduced in the greenhouse and orchidarium in the Botanical Survey of India (BSI) in Shillong for ex situ conservation and identification once they bore flowers. Flowering materials were then preserved as herbarium vouchers. All visible morphological characters were studies in the field and at the laboratory of ASSAM herbarium in BSI and Department of Botany, University of Gauhati, Assam. The collections were processed according to the standard herbarium specimen preparation techniques with slight modification as mentioned by Jain & Rao (1977) and Bridson & Forman (1989). Specimens were identified using the diagnostic characters described and the identification keys mentioned by Hooker (1895), Duthie (1906)

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Note: Terrestrial plant of pale pink to white flower, occurring in shaded humus soil of the subtropical forests between the altitudes of 100-1,400 m. The flowering season recorded in the study area is from August to late September. The species is rare and is recorded for the first time from the Garo district of Meghalaya. Widely distribution recorded from Bangladesh, Bhutan, and India (Arunachal Pradesh, Sikkim, Assam, Meghalaya, Nagaland, Manipur, Mizoram).

Arundina Blume
The genus comprises two species (http://www. theplantlist.org) distributed in southern and southeastern Asia and both are found in India; one species from Meghalaya (Kataki 1986 Note: Terrestrial plant of uniformly pink to pale purple flowers seen grows along with grasslands in forest borders at 1,000-1,400 m elevation in the study area. It flowers between May and September. Distribution recorded from Bhutan, China, India (Arunachal Pradesh, Meghalaya), Nepal, Myanmar, and Thailand.

Bulbophyllum Thouars
The genus is comprised of 2,058 species (http://www. plantsoftheworldonline.org/) distributed throughout the World; about 300 species in tropical regions (Kataki 1986) Note: Plant terrestrial of yellow flower spotted with purple brown, and lip pale violet, white at the base, grows in a shady area of subtropical forests. It flowers in September and in some other places of Meghalaya, it is recorded till November. The species is rare and threatened in the NBR. The distribution of the species is reported from Bhutan, China, India (Arunachal Pradesh, Assam, Meghalaya, Nagaland, Manipur, Sikkim), Myanmar, and Thailand.

Ceratostylis Blume
The genus comprises 153 species (http://www. plantsoftheworldonline.org/) distributed in Southern and J TT southeastern Asia to Indonesia and New Guinea (Pearce & Cribb 2002), three species from India, two species from Meghalaya (Kataki 1986), and one species in NBR.
Note: Epiphytes plant of pinkish-yellow flowers grows in the primary forests between the elevation ranges of 1,000-1,480 m in the study area. Flowering was recorded in May. Distribution of the species widely recorded from Bhutan, China, India (Meghalaya, Arunachal Pradesh, Assam, Nagaland, Manipur, Mizoram, Sikkim), Nepal, Thailand, and Myanmar.
Note: Terrestrial plant of white flowers found growing in the subtropical forests at 900-1,400 m elevation in the study area. Its flowering was recorded between May and August. Distribution reported from Bhutan, India (Meghalaya, Arunachal Pradesh, Assam, Nagaland), Nepal, Myanmar, and Thailand.

Cleisostoma Blume
The genus comprises 96 species (http://www. plantsoftheworldonline.org/) distributed across the world in tropical and subtropical climate (Bose et al. 1999), 35 species in tropical Asia (Kataki 1986), 19 species in India (Gogoi et al. 2009 Note: Epiphytic plant of purple flower with a yellow stripe at the centre, found to be growing on tree trunks in shady places in the tropical and subtropical forests. The plant flowers in April and continues till June. It is rare in the Nokrek, and recorded for the first time from the Garo districts, and is one of the most threatened plants of the state. After a repeated search in the study area, we could only locate two populations: one at the Sabokgre (subtropical area), and one at the Rongrenggre (tropical forests). Bhutan, China, India (Arunachal Pradesh, Assam, Manipur, Meghalaya, Mizoram, Nagaland, Tripura, Sikkim), Nepal, Myanmar, and Thailand. Note: Epiphytic plants of yellow to brown flowers, growing on tree trunks in the tropical and subtropical forests between the altitude ranges of 450-1,050 m. Flowering was recorded from May to June. During the scrutiny of ASSAM herbarium, the authors come across two unidentified sheets of MKV Rao, and after identification, it is a new record for Garo district. India (Arunachal Pradesh, Assam, Meghalaya, Nagaland, Mizoram, Sikkim), Myanmar, and Thailand.

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plantsoftheworldonline.org/), 34 species in India (Das & Jain 1980), 22 species in Meghalaya (Kataki 1986), and eight species in NBR. Key to species 1a. Inflorescence with imbricate sterile bracts .... Note: Epiphytic plant of yellow flowers found to be growing in dense primary subtropical forests at 1,000-1,400 m. Flowering was recorded in November and January. It is extremely rare in Nokrek, as authors could locate only two localities after repeated searches in the BR. It is reported from Bhutan, India (Arunachal Pradesh, Meghalaya, Mizoram, Sikkim), Nepal, and Myanmar. Note: Plant epiphytic plant of flower brownish-yellow or greenish to dark brown, and lip dark brown, on lofty trees, sometimes lithophytic on moss-covered rocks in the shady area of the tropical and subtropical forests between the elevations of 500-1,000 m. Its flowering period was recorded in January and continued till the end of March. The plant is rare and threatened in Nokrek. Distribution of the species recorded from Bhutan, India (Arunachal Pradesh, Assam, Meghalaya, Manipur, Nagaland, Sikkim), Myanmar, and Thailand.

Corybas Salisb.
The genus of terrestrial orchids that comprised about 147 species (http://www.plantsoftheworldonline.org/) found from southern China and India to Australia, New Zealand, and western Pacific Islands (Chung & Hsu 2008), one species from Meghalaya, and one species in NBR. Note: A terrestrial plant having white flowers grows along with grasses in subtropical vegetation at 1,000-1,480 m elevations in the study area. Flowering was recorded between June and July. The species is recorded from China and India (Sikkim, Meghalaya).

Corymborkis Thouars
The genus is comprised of eight species (http:// www.plantsoftheworldonline.org/) distributed across the world in tropic and subtropics, one species from Meghalaya, and one species in NBR.
Note: Clump-forming terrestrial plant tubular fragrant white flowers, growing in the subtropical forests. It flowers usually in July. The plant is rare in Nokrek as well as in the state. The distribution of the species is recorded from China, India (Sikkim, Arunachal Pradesh, Assam, Meghalaya), Japan, Malaysia, Myanmar, and Thailand.

Crepidium Blume
The genus is represented by 291 species (http:// www.plantsoftheworldonline.org/) throughout the world mostly in tropical and subtropical regions of Asia to the Pacific, six species from Meghalaya, and one species in NBR.

Cylindrolobus Blume
The genus is represented by 75 species (http:// www.plantsoftheworldonline.org/) in its native range of southern China to tropical Asia and one species in NBR.
Key to species 1a.
Pseudobulbs ovoid, bilaterally flattened; leaves 4-6, oblong, obtuse, unequal bilobed at apex, thick, rigid, erect …. Note: Epiphytic plant of flowers green with purple dots on tree trunks, occasionally lithophytic on mosscovered big rocks in dense under canopy layer in the subtropical forests above 1,000 m. Its flowering period was recorded from May to July. This plant species is again extremely rare in Nokrek as well as in the statebecause after long surveys, only two localities,Tura Hills and Cherrepunjee, are recorded so far from Meghalaya. It's a new record for the Garo districts. The species is reported from Bhutan, China, India (Arunachal Pradesh, Sikkim, Meghalaya, Manipur, Mizoram, Nagaland), Myanmar, Nepal, and Thailand.
Specimen studied: Tura Hills, DBD22629 (ASSAM). Note: Epiphytic plant of purplish-brown flower with slightly yellowish lip, growing on tree trunks in the primary tropical and subtropical forests between the elevations range of 400-1,400 m. Flowering was recorded from October to November. Although this species is common in the state, it was rarely recorded in Nokrek, also a new record for the Garo district. Distribution of the species reported from Bhutan, China, India (Arunachal Pradesh, Meghalaya, Manipur, Nagaland, Sikkim), Myanmar, and Nepal.

Dendrobium Sw.
This genus is the second-largest number of species in the Orchidaceae family and comprises 1,536 species (http://www.plantsoftheworldonline.org/) distributed in tropical and subtropical Asia to Oceania (Liu & Chen 2011), about 102 species in India (Gogoi 2011), 47 species in Meghalaya, and 20 species in NBR.
Key to species 1a.
Plant with fusiform to clavate stems or pseudobulbs, often angled, sometimes compressed; leaves 1-5, thick, nearly sheath-less, more or less, clustered at apex; leaf-sheaths insignificant .. Sepals and petals bright yellow to copper or  Note: Epiphytic plant of big white flowers of 6.5-11.5 cm diameter with a centre lip changes from yellow to orange after opening for about a week, delicately fragrant, grows on tree trunks in the open as well as in the dense forests of tropical and subtropical regions. Its flowering starts in October-December, fruiting in April-May. The plant is rare in Nokrek hills, recorded for the first time from Garo district. The distribution of the species is native to Indian regions, although recorded from Bhutan, India (Arunachal Pradesh, Assam, Manipur, Meghalaya, Mizoram, Nagaland, Sikkim, Tripura), Malaysia, Myanmar, Nepal, Thailand, and Vietnam.
Specimen studied: Nokrek hills, on the way to Tura peak, DBD 29139 (ASSAM). Note: Epiphytic plant of bright yellow flowers of faint, honey-like fragrance on pendent racemes, grows on tree trunks in the tropical and deciduous forests. Its flowering period is between April-June. The species is rare in the Nokrek hills, reported being a native species of southern and southeastern Asia. Distribution widely from China, India (Assam, Meghalaya, Sikkim), Myanmar, and Thailand. Note: the flower colour of the species is very similar to Dendrobium jenkinsii Wall. ex Lindl. but differs in mostly having an inflorescence with many flowers. Note: Epiphytic as well as lithophytic plant, fragrant, waxy flowers, colour variable; the base of the petals is pale pink or white, grading into a stronger amethyst-purple towards the tip; the lip is velvety with a rich maroon-purple basal part, surrounded by a pale yellowish-white portion. The species were recorded from tropical deciduous and subtropical forests at 750-1,500 m at the foothills of Nokrek and surrounding areas. The flowering of this plant species could be seen continuing throughout the year. This plant species is rare in Nokrek (Singh & Singh 2002), and after repeated search in wild; the species could not be the location in the study area. Distribution of the species recorded from Bhutan, China, India (Arunachal Pradesh, Assam, Manipur, Meghalaya, Nagaland, Sikkim), Nepal, Myanmar, Nepal, Laos, Thailand, and Vietnam.

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Specimen studied: Rongrengre, DBD 29127 (ASSAM). Note: Epiphytic plant species having white flowers tinged purplish-rose towards the tip, two to three in number, fragrant, recorded on tree trunks in tropical and subtropical forests at 600-1,300 m. It flowers in April-June, and the fruiting period is July-August. The species is rare in Nokrek as well as in Meghalaya and recorded for the first time from Garo district. Distribution widely recorded from Bhutan, Bangladesh, India (Arunachal Pradesh, Assam, Manipur, Mizoram, Meghalaya, Nagaland, Sikkim), Myanmar, and Nepal.

Dendrolirium Blume
The genus is represented by 12 species (http://www. Note: Epiphytic, occasionally, lithophytic species of plant found to be having white to yellow cottony hairy flowering twigs. The plant recorded growing on tree trunks along the riverside and moss-laden rocks in subtropical forests. The flowering period is between April and May, however fruiting recorded in August. This species is rare in the study area, common in the state of Meghalaya. Note: Usually terrestrial plants of purplish-red to greenish-yellow flowers growing in moist places along streamsides, sometimes epiphytic on tree trunks. Its flowering period is between June-August and fruiting in September-December. The species is recorded rarely in Nokrek hills, although common in the state of Meghalaya, but recorded for the first time from the Garo district. The wide distribution of this plant species is recorded from Australia, Bhutan, Cambodia, China, India (Meghalaya, Mizoram), Indonesia, Japan, Laos, Malaysia, Myanmar, Nepal, New Guinea, Philippines, Sri Lanka, Thailand, and Vietnam.
Note: The species can be easily identified based on unique flowers, which are always facing downwards, tepals curving inwards and lip with a typically large and deep lamina cavity.

Diplomeris D.Don
The genus comprises of three species (http://www. plantsoftheworldonline.org/) distributed in southeastern Asian countries; one species from Meghalaya, and one species in NBR.

Diplomeris pulchella D.Don in Prodr. Fl. Nepal. 26. 1825.
Note: Terrestrial plant species were recorded growing in the primary forest in shaded humus-covered soil between the elevations of 200-800 m in the study area. Flowering was recorded between August and November. Distribution widely recorded from India (Arunachal Pradesh, Meghalaya), Nepal, Myanmar.

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plantsoftheworldonline.org/)distributed in tropical to the alpine climate in the world and one species in NBR.

Eriodes Rolfe
The genus is represented by one species (http://www. theplantlist.org/) distributed and endemic to Southern and southeastern Asia, one species from Meghalaya, and one species in NBR.
Key to species 1a.
The Note: A pendent epiphytic plant having white flowers spotted with reddish-purple, pale yellow on the outer side, and lip white with a purple edge, and column purple, grows in both the tropical and subtropical region of the study area. It flowers October-December. The plant is rare in the study area and recorded only from the Sabogre region having a small population. Distribution recorded from northeastern India.

Geodorum Jackson
The genus comprises 12 species (http://www. theplantlist.org) distributed in tropical and subtropical environment (Gogoi et al. 2012), one species from Meghalaya, and one species in NBR. April to May, however, fruiting can be seen from June to July. The species is widely distributed in Bhutan, China, India (Arunachal Pradesh, Meghalaya, Sikkim), Java, India, Myanmar, Nepal, and Thailand.

Goodyera R.Br.
The genuscomprises 99 species (http://www. theplantlist.org) widely distributed in the tropical and subtropical environment across the world, six species from Meghalaya, and one species in NBR.

1890.
Note: Terrestrial plants with yellow flowers growing along the forest borders in shaded moist soil especially near streams and rivers at 1,000-1,400 m elevations. Flowering was recorded from July till August. It is rare in Nokrek, and distribution is widely reported from India (Meghalaya, Manipur, Mizoram) and Thailand.

Habenaria marginata Colebr. in W.J.Hooker, Exot. Fl. t. 136. 1824.
Note: Terrestrial plants with yellow flowers growing along the forest borders in shaded moist soil especially near streams and rivers at 800-1,100 m elevations. It flowers between October and December. Distribution of the species recorded from India (throughout northeastern states), Bhutan, China, Myanmar, Nepal, and Thailand.

Herminium R.Br.
The genus is comprised of 22 species (http://www. theplantlist.org) distributed in Europe and Asia, five species in Indian Himalaya, one species in Meghalaya, and one species in NBR. Note: Terrestrial erect plant with pale green flowers grows along with the grasses in slopes at 900-1,450 m elevation in the study area. The plant starts flowering in June till August, and fruits start in August till November. The distribution has been reported from China, India (Arunachal Pradesh, Meghalaya, Sikkim, Assam, Nagaland, Mizoram, Tripura), Myanmar, Nepal, and Thailand.

1840.
Note: Terrestrial plant of white flowers tinged with orangish-red to pink grows along with the grasses in slopes at 900-1,450 m elevation. Flowering can be seen in April, however, fruiting can be recorded from September to November. It is rare in the biosphere reserve. Widely distributed in China, India (Meghalaya, Sikkim), Myanmar, and Thailand.

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subtropical and temperate environment across the World; 260 species in tropical Asia (Singh 2015); 45 species in India (Gogoi et al. 2012); 17 species in Meghalaya (Kataki 1986), and seven species in NBR.
Key to species 1a. Leaves

1851.
Note:An epiphytic species grows on tree trunks in tropical and subtropical forests at 450-1,400 m elevation in shady areas. Flowering and fruiting can be seen between July and November. This plant species is rare in the study area. The distribution of the species is widely reported from Bhutan, China, India (throughout the regions), Nepal, Myanmar, Thailand, and India.
Specimen studied: Way to Baghmara, MKV Rao 53394 (ASSAM). Note: Small epiphytic plant one-leaved with yellow flowers, grows on tree trunks in tropical and subtropical forests at 300-1,000 m elevation in the study area. Flowering has been recorded in August. Its occurrence in Nokrek is rare, however, the distribution of the species is reported from Bhutan, China, India (throughout the regions), Nepal, and India.

Liparis cespitosa
Specimen studied: Way to Sasatgiri, MKV Rao 53322A (ASSAM). Note: Terrestrial as well as epiphytic plant with purple flowers usually growing on tree trunks as well as in moist places on tree trunks in tropical and subtropical forests at 300-1,000 m. Its flowering was recorded in June-July.

Micropera Lindl.
The genus comprises of 21 species (http://www. theplantlist.org) widely distributed in tropical and subtropical environment across the world (Lucksom 2007), five species in India (Kataki 1986), three species in Meghalaya, and three species in NBR.
Key to species 1a.
Inflorescence Note:A plant epiphytic with pale purple or pink flowers grows on tree trunks in tropical and subtropical forests at 500-1,400 m elevation in the study area. This species flowers between May and June. The species is distributed occasionally in the Nokrek hills, however, wide distribution of the plant population is reported from China, India (Arunachal Pradesh, Meghalaya, Sikkim), and Thailand.

Mycaranthes Blume
The genus is represented by 36 species (http:// www.plantsoftheworldonline.org/) distributed from southcentral China to tropical Asia and one species in NBR.

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Note:Epiphytic as well as lithophytic plant recorded to have pale yellowish-green flowers with brownishpurple blotches on column and lip callus white. The plant recorded growing on tree trunks in shady places of tropical and subtropical forests at 750 -1,250 m elevation in the study area. It flowers between June and July. It is rare in the NBR and reported as new for the Garo Mountains of Meghalaya. Distribution widely recorded from Bhutan, India (Arunachal Pradesh, Assam, Manipur, Meghalaya, Nagaland, Sikkim), Cambodia, Laos, Myanmar, Nepal, and Thailand. Note: Epiphytic plant of two leaves and yellow keeled white flowers usually grows on tree trunks in tropical and subtropical forests between the elevations of 500-1,400 m in the study area. It flowers between June and September. The population status is rare and endangered in the Nokrek hills. Wide distribution of the species reported from China, India (Arunachal Pradesh, Assam, Meghalaya, Sikkim), and Thailand.

Oberonia Lindl.
This genus is represented by 298 species (http:// www.plantsoftheworldonline.org) widely distributed in tropical Asia and Australia (Bose et al. 1999), 50 species in India (Gogoi et al. 2012 Note: Plant epiphyte of yellowish flowers rusty brown at the centre, grows on moss-laden tree trunks in tropical and subtropical forests at 600-1,200 m elevation in the study area. The flowering of the plant can be seen in July to August. It is rare in the Nokrek hills. Distribution of the species recorded from Cambodia, China, India (Arunachal Pradesh, Assam, Meghalaya, Sikkim), and Vietnam.

1838.
Note:Epiphytic plant of reddish-brown flowers found on huge tall trees in shady places in tropical and subtropical forests at 700-1,200 m elevation in the study area. The plant flowers in September and October. It is rare in the Nokrek hills. Distribution of this species reported from Cambodia, China, India (Sikkim, Meghalaya), Nepal, Thailand, and Vietnam.

Odontochilus Blume
The genus is represented by 56 species (http:// www.plantsoftheworldonline.org) widely distributed in southern and southeastern Asia, seven species in India (Misra 2007), one species in Meghalaya, and one species in NBR. Note: Terrestrial plant of flowers pale green tinged with brown and lip yellow, recorded growing in the primary forests in shaded humus soil, often on rotting wood between 1000 and 1400m elevations in the study area. Distribution recorded from India (Arunachal Pradesh, Assam, Sikkim, Meghalaya, Nagaland, Manipur, Mizoram, Sikkim) and Thailand.

Otochilus Lindl.
This genus is represented by five species (http:// www.theplantlist.org) widely distributed throughout the world, four species in Meghalaya (Kataki 1986), and one species in NBR.

Papilionanthe Schltr.
The genus is represented by 10 species (http:// www.plantsoftheworldonline.org/) widely distributed in the tropical, subtropical and temperate environments throughout the world, four species in India (Gogoi et al. 2009); three species in Meghalaya (Kataki 1986), and one species in NBR. Note:Climbing epiphytic plant with white flowers tinged with pink and yellowish to brown spur, inflorescence 2-5 flowers, grows primarily on tree trunks at 500-1,000 m elevations in tropical and subtropical forests. The flowering of this plant species is usually seen between May and June. This species found to be rare and threatened in Nokrek forests due to human ornamental needs. Wide distribution of the species recorded from India (throughout northeastern states), Bangladesh, Bhutan, Laos, Myanmar, Nepal, Thailand, and Vietnam. Note: Epiphytic plants with many-flowered habitat on tree trunks of Quercus and Castanopsis trees; flowers yellowish with dark spots, growing in subtropical environment at 950-1,500 m elevations. The flowering of this species is usually seen in April and May. The species have been recorded wild from India (Assam, Meghalaya, West Bengal), China, Bhutan, Myanmar, Nepal, and Vietnam. This species is critically endangering at a faster rate in Nokrek BR.
Key to species 1a.

(Image 25)
Note: Epiphytic plants with creeping rhizomes and densely flowered inflorescence. Flowers usually white or slightly red-tinged, seen blooming in August and fruits start appearing in November. The luxuriant population of this species is found between the elevation range of 1,000-2,500 m in tropical and subtropical forests. Wide distribution of this species is reported from India (Arunachal Pradesh, Assam, Meghalaya, Nagaland, Manipur, Mizoram, Tripura), Australia, Bhutan,

Satyrium Sw.
The genus is represented by 90 species (http:// www.plantsoftheworldonline.org) widely distributed in tropical to alpine climate across the world, four species in India, one species from Meghalaya (Kataki 1986), and one species in NBR. 51.1. Satyrium nepalense D.Don in Prodr. Fl. Nepal. 26.

1825.
Note: Terrestrial herbs with tubers and purplishrose flowers were found to be growing along forest margins between the elevation ranges of 1,000-3,000 m. The flowering of the plants can be seen in September and October. This species is endemic to Asia and wide distribution of this species reported from India (Arunachal Pradesh, Meghalaya, Sikkim), Bhutan, China, Myanmar, Nepal, and Sri Lanka.

1838.
Note: Pendulous epiphytic plants with conduplicate leaves and purplish-red flowers with white apices prefer to grow on moss deposited trees in tropical and subtropical environments at 100-1,500 m. Flowering can be seen between April and June. This species is rare in Nokrek hills, however, wide distributionof this plant species is reported from India (Assam, Arunachal Pradesh, Meghalaya, Sikkim, West Bengal), Bhutan, China, Cambodia, Laos, Myanmar, Nepal, Thailand, and Vietnam.

Spathoglottis Blume
The genus is comprised of 41 species (http://www. plantsoftheworldonline.org) distributed in the diverse habitat of India, Philippines, southeastern Asia, New Guinea, New Caledonia, Solomon Islands, Borneo, and Australia (Singh 2015), two species from Meghalaya, and two species in NBR.
Key to species 1a. Flowers purplish, drooping, 2.5-3.5 cm across ... Note: Terrestrial herbs with ovoid pseudobulbs and purplish flowers were found to be growing in grasslands and along forest margins between the elevation ranges of 800-1,800 m. The flowering of the plants can be seen in August in Nokrek hills and is very rare in occurrence. Wide distribution of this species is reported from India (Arunachal Pradesh, Meghalaya), Australia, China, Indonesia, Japan, Malaysia, Pacific Islands, New Guinea, Philippines, Sri Lanka, Thailand, and Vietnam. Note:Terrestrial herbs with dorsoventrally compressed pseudobulbs and yellow flowers with violet spotted lips. Flowers of this species can be seen in August and September. This species grows on hill slopes in the subtropical forest at 1,000-1,400 m in the study area of Nokrek forests. Wide distribution reported from India (Assam, Arunachal Pradesh, Meghalaya, Sikkim), Cambodia, China, Laos, Myanmar, Thailand, and Vietnam.
This genus is represented by 24 species (http://www. theplantlist.org) widely distributed in the tropical and subtropical regions.

1890.
Note: Small epiphytic plants having conical-shaped pseudobulb and white coloured many flowered inflorescences. Flowering in plants appears in early summer and can also be seen till November. It prefers