Amitostigma pathakianum Av. Bhattacharjee, 2015

Bhattacharjee, Avishek, 2015, A new species of Amitostigma (Orchidinae, Orchidaceae) from India, Phytotaxa 230 (3), pp. 267-273 : 268-272

Amitostigma pathakianum Av. Bhattacharjee , sp. nov. ( FIGURE 1 , 2 )

Type:— INDIA. Arunachal Pradesh: Upper Siang, Kamatukut to Kanebango , 2800–3400 m, 05 August 2012, M.K. Pathak 54472 (holotype CAL! , isotype CAL! ).

Diagnosis:— Similar to Amitostigma trifurcatum Tang et al. (1982: 80) but differing in its smaller habit (up to 20 cm tall vs 24–36 cm tall in A. trifurcatum ), narrower leaves (1–3 mm vs 5–7 mm in A. trifurcatum ), ebracteate peduncle or with 1 foliaceous sterile bract on peduncle (vs. occasionally with 2 foliaceous sterile bracts in A. trifurcatum ), 2–5 flowered rachis (vs. 6–9 flowered rachis in A. trifurcatum ), longer petals (4.4–5 mm vs 3–3.8 mm in A. trifurcatum ) and linear lateral lobes of lip which are 3.4–4 mm long and almost equalling the 3.5–4 mm long middle lobe (vs. lanceolate to narrowly triangular lateral lobes of lip which are 1–1.5 mm long and much shorter than 3.5–4 mm long middle lobe in A. trifurcatum ).

Description:— Slender, terrestrial herbs up to 20 cm tall. Tubers globose, 4–7 mm across. Stem up to 16 cm long, c. 1 mm in width, glabrous, with 2 tubular sheaths at base, 1-leaved. Leaf cauline, linear to narrowly linear-lanceolate, mostly falcate, 3.2–7.5 × 0.1–0.3 cm, uniformly green, acute at apex. Peduncle ebarcteate or with 1 foliaceous sterile bracts, uniformly green; sterile bracts linear-lanceolate to oblong-lanceolate, 0.7–1.5 × c. 0.1 cm, green; rachis 1–2.5 cm long, subdensely 2–5 flowered; floral bracts ovate-lanceolate, 3–5 × 1–1.2 mm, shorter than pedicel plus ovary, green, occasionally with pale purplish tinge, acute at apex, 1-veined. Flowers subsecund, pinkish-purple with pinkish-white tinge at base of lip; pedicel plus ovary narrowly elliptic-fusiform, 5–7.5 × 0.8–1.2 mm, green, glabrous, with minute granular depositions mainly along ridges. Dorsal sepal erect, narrowly elliptic-lanceolate, 4–4.5 × 1–1.2 mm, slightly plicate, recurved, pinkish-purple, subacute at apex, 1-veined; lateral sepals spreading to recurved, narrowly elliptic-lanceolate, slightly oblique, 4–5 × 1–1.2 mm, pinkish-purple, subacute at apex, 1-veined. Petals narrowly ovate-lanceolate, 4.4–5 × 1.5–2 mm, slightly plicate, oblique, pinkish-purple, subacute to acute at apex, 1-veined; lip 5.5–7 mm long, 3-lobed slightly above its base, pinkish-white with purple-pink spots near base, pinkish-purple above, apices of lobes sometimes undulate or irregular, with 5 stout raised veins of which 2 enter into lateral lobes and 3 enter into middle lobe; lateral lobes (free portion) linear, 3.4–4 × 0.3–0.5 mm, obtuse at apex; mid-lobe (free portion) oblong-ligulate, 3.5–4 × 0.8–1.5 mm, obtuse at apex; spur suborbicular or subsquarish or subconical, 0.8–1 × 0.5–0.8 mm, slightly curved, obtuse at apex. Column 2–2.5 mm long, rostellum with 1 obscure central lobe and 2 short lateral lobes, lobes obtuse to subtruncate at apices; stigma with 2 prominent oblong to subclavate lateral lobes and a small central lobe, slightly raised. Pollinia 2, sectile; viscidia narrowly ovate, large.

Flowering:— August.

Distribution:— India (Arunachal Pradesh).

Habitat:— The plants are found growing on the wet hill-slopes associated with mosses and liverworts in between 2800–3400 m elevation.

Etymology:— The species is named after Dr. Mithilesh Kumar Pathak (Born: 26 January 1968 — Deceased: 07 February 2013), Botanist, Central National Herbarium, Botanical Survey of India, Howrah who collected the types during his last field tour in Upper Siang District, Arunachal Pradesh in August, 2012.

Additional specimens: — INDIA. Arunachal Pradesh: Upper Siang, Kamatukut to Kanebango , 2800–3400 m, 05 August 2012, M.K. Pathak 54498 ( CAL!) .

Notes:— The plants were located in two populations (in same locality) with 70–80 mature individuals in total within an area about 250 square meters. No anthropogenic activity was observed in the type locality ( FIGURE 3 ) and the only possible threat to these plants was grazing by wild herbivores (if any). As the species is being described here for the first time, its threats as per the IUCN-guidelines (IUCN SPS 2014) can be assessed only after few years.

Dr. Pathak collected 17 plants under two field collection numbers on which the diagnosis and description are based. The new species can be easily identified by its single, cauline, linear to narrowly linear-lanceolate leaf, peduncle with or without 1 foliaceous sterile bract, laxly few flowered inflorescence and most importantly by characters of its labellum. The relative length and breadth of linear lateral lobes and oblong-ligulate mid-lobe (which are more or less same in length) of lip in A. pathakianum are crucial for its identification.

Figures

FIGURE 1. Amitostigma pathakianum. A. Habit. B. Portion of stem and inflorescence. C. A flower with bract. D. Portion of flower after removing sepals and petals. E. Dorsa sepal (side view). F. Petal (spread). G. Lateral sepal (side view). H. Lip (spread). I. Column, spur, pedicel plus ovary (side view; anther removed). [drawn from M.K. Pathak 54472, M.K. Pathak 54498 by D.K. Sah (BSI, Howrah)].

FIGURE 2. Amitostigma pathakianum. A. Habit. B. Holotype. C. A flower (side view). D. Portion of flower after removing sepals and petals. E. Dorsal sepal (side view). F. Lateral sepal (side view). G. Petal (spread). H–J. Lip (spread). [A. photo by (Late) Dr. M.K. Pathak; C–J. dissected by A. Bhattacharjee from pressed and dried flowers from M.K. Pathak 54472, M.K. Pathak 54498 soaked in diluted Ammonium hydroxide solution).

FIGURE 3. Distribution map Amitostigma pathakianum (10 × 10 km grids).