Siphocranion macranthum

Siphocranion macranthum (Hook.f.) C.Y.Wu, Acta Phytotax. Sin. 8: 56 (1959) (syn: Hancea hemsleyana H.Lév. ; Hancea prainiana H.Lév. ; Isodon macranthus (Hook.f.) Kudô ; Isodon macranthus var. prainianus (H.Lév.) Kudô ; Plectranthus macranthus Hook.f. ; Plectranthus prainianus (H.Lév.) Dunn ; Rabdosia macrantha (Hook.f.) H.Hara ; Siphocranion macranthum var. microphyllum C.Y.Wu ; Siphocranion macranthum var. prainianum (H.Lév.) C.Y.Wu & H.W.Li);
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E. Himalaya to S. China: Assam, China South-Central, China Southeast, East Himalaya, Myanmar, Tibet, Vietnam as per POWO;

Stems 30-60cm, tomentose, glabrescent below. Leaves ovate to elliptic, 5-8.5 x 2.8-5.2cm, base cuneate or rounded, apex acute to acuminate, margins serrate, both surfaces tomentose on veins, sparsely tomentose elsewhere; petiole 0.5-4cm. Inflorescence 8-18cm, whorls 2 flowered; pedicels 4-5mm. Bracts ovate acuminate,3-5mm long. Calyx c 4mm,glandular-puberulent and with scattered sessile glands; upper lip c 2mm with 3 subulate teeth; lower lip slightly shorter than upper and with 2 subulate teeth; fruiting calyx enlarging, up to 10mm long. Corolla pink purple,2-2.4cm;tube straight,1.5-1.8cm;upper lip c 5mm,4-lobed,lobes obtuse; lower lip subequal to upper, entire. Stamens inserted in throat, not exceeding corolla. Nutlets c 2 x 2mm.
Fl. August
(Attributions: A.C.J Grierson & D.G Long. Flora of Bhutan. Published by RBGE and RGoB. 1999 as per Bhutan Biodiversity Portal )
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Please id this flowering plant: 3 images.
Found and photographed this flower at Upper Samdong area, East Sikkim. Please id this flowering plant.

Lamiaceae ???

Initially I thought it would be a member of the Lamiaceae family. Did not get any idea up to genus level.

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References:
POWO  Catalogue of Life  GBIF (High resolution specimens) BSI Flora of India Checklist  Flora of China  Bhutan Biodiversity Portal  IBIS Flora (Flora of British India) Wikipedia