Dendrobium darjeelingensis – a Less Known Orchid, New Record for Assam

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Authors

H.A. Barbhuiya1, S.K.Singh1, C.M. Sabapathy2

 1Botanical Survey of India Eastern Regional Centre, Shillong-793003

 email: hussainbsi@yahoo.com; sksbsinc@rediffmail.com

2 Botanical Survey of India, Central National Herbarium,P.O. B.Garden-Howrah – 711 103

email: m_saba@rediffmail.com

Abstract

Dendrobium darjeelingensis Pradhan is reported here from Assam North-east India. This constitutes second collection of the species from Indian regions and third in world.  A detailed taxonomic description along with photographic illustration is provided to facilitate its future identification.

Keywords Dendrobium darjeelingensis, New record, Assam.

Introduction

Dendrobium Sw., is one of the largest epiphytic (occasionally lithophytic) genera of Orchidaceae, comprising c. 1100 species in the world (Wood, 2006). In India, the genus is represented by 116 species (Mishra, 2007). Chowdhury (2005) listed c. 43 spp. from Assam, India.

Dendrobium darjeelingensis was described by Pradhan (1979) on the basis of collection made in 1975 from Darjeeling, West Bengal, India. He kept its Holotype in his personal Herbarium and it was destroyed few years back in a fire accident (Pers. Comm.). Later, this species was recorded from Nepal (www.Efloras.org; annotated checklist of the flowering plants of Nepal).

Recently, during an exploration near Loharbond (Cachar district of Assam) in January 2012, one of us (HAB) encountered a small epiphytic population growing on tree trunk of Tectona grandis L. f. in lowland semi-evergreen forest, which subsequently identified as D. darjeelingensis. It is interesting to note that the place of occurrence of this species is well explored and genus Dendrobium is already documented (Bhattacharjee et al., 2008), but without any mention of this species. Thus it constitutes a new record for the Assam, North-east India. The occurrence of this species also constitutes second collection of from Indian regions and third in the world. It may also be noted here that the present collection is the only available material in any Indian herbarium.

Taxonomic Description

Dendrobium darjeelingensis Pradhan, Indian Orchids: Guide Identif. & Cult. 2: 336 1979.

Pseudobulbs conical to fusiform, 1-3 cm high, 5-7 mm in diameter, internodes 3-4 closely surrounded by sheathes. Leaves not seen. Inflorescence 2-3, from nodes, 9-15 mm long, 2-5 flowered. Flower pale-green in colour. Floral bracts pale brown, triangular, 3-nerved, 1.5-2 mm long, acute. Pedicel and ovary 3-3.5 x 0.2-0.8 mm. Dorsal sepal ovate-triangular, 5-nerved, 4.5 x 2.7 mm, acute at apex. Lateral sepals 2, oblique, 5-nerved, 5.8-6 x 2.5-4 mm. Petals ovate-lanceolate, 3-nerved, 4.2-4.5 x 1.5-1.6 mm. Lip oblong-ovate ca. 7 mm long, 4 mm wide at the middle and the proximal edge ca. 1 mm wide, connate with column foot forming a spur, 3-lobed, hypochile with entire edges, lateral lobes-2, with distinct triangular front, epichile with slightly crenulate to wavy margin, keels-3, placed at the middle of the lip, rounded, reaching more than half way of the blade, middle one indistinct. Column ca 2.5 x 1 mm; column-foot ca 4.5 x 1 mm. Anther cap dome shaped, minutely papillose, 0.8 x 0.7 mm, front edge pilose. Pollinia in 2 pairs, yellow, ca. 0.5 x 0.2 mm. Fruits green in colour, 7-8 mm long and 4-4.3 mm in diameter, 3-ridged.

Discussion

The plants belong to section Stachyobium of genus Dendrobium, wherein the plants are generally smaller in size and leafless in flowering condition. Our plants slightly vary in habit and pseudobulbs size than the plants of Darjeeling mentioned in protologue. The flowering plants are leafless and the pseudobulbs are 1-3 cm long (while flowering plants from Darjeeling were with leaf and pseudobulbs up to 7.5 cm as mentioned in protologue). The inflorescence of our plants are slightly shorter (2-5 flowered, 9-15 mm long.) than the Darjeeling plants (4-6 flowered, 40 mm long). These variations mere because the different geographical condition and changes in Climate. Flowering and fruiting takes place in the month of November-January.

Specimen examined: India, Assam, Cachar, Near Loharbond Beat Office, (24º 36? 10.92?? N latitude & 92º 43? 21.81?? E longitude), Epiphytic on tree trunk of Tectona grandis L. f. in lowland semi-evergreen forest at c. 37 msl. 06.01.2012, H.A. Barbhuiya 846 (ASSAM).

Acknowledgement

Authors are thankful to the Director, Botanical Survey of India, Kolkata for providing the facilities and to the Sci.-E & H.O.O., BSI, Eastern Regional Centre, Shillong for encouragement.

References

  1.  Bhattacharjee, B., Dutta, B. K. and P. Tandon, The genus Dendrobium Sw. in Southern Assam (Barak Valley), Cachar. J. Orchid Soc. India, 22: 39-44.
  2.  Chowdhury, S., Assam’s Flora, Present Status of Vascular Plants. Assam Science Technology and Environmental Council, Guwahati, 2005.
  3. Misra, S., Orchids of India, a glimpse. Bishen Singh Mahendra Pal Singh, Dehradun. 2007.
  4. Pradhan, U. C., Indian Orchids: Guide to Identification  and  Culture. Volume II. Premulaceae Books, Kalimpong, 1979.
  5. Wood, H. P.2006. The Dendrobiums. A. R. G. Gantner Verlag K. G., Germany.

EXPLANATION OF THE FIGURES

Fig.1: Dendrobium darjeelingensis. A: Habit. B: A single plant with inflorescence. C: Floral bract. D. Flower. E. Dorsal sepal. F. Lateral sepals. G. Petals. H. Front view of flower when lip was excised. I. Floral perigon. J. Column with lip. K. Lip. L. Column. M. Frontal view of anther cap. N. Distal view of anther cap. O. Pollinia. P. Fruit.

 

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