Aeschynanthus mannii Kurz ex C.B. Clarke, Monogr. Phan. 5: 29 1883. (syn: Trichosporum mannii Kuntze);
Assam to Myanmar: Assam, Bangladesh, Myanmar as per POWO;
MS,Sept.,2021/04 Aeschynanthus sp. for id.: 3 images.
Location : Lurh tlang, Mizoram near Myanmar border
Date : 19-03-2019
Could not find a match as per comparative images at Aeschynanthus
Pl. post keys from your book.
After checking all the listed species, I think it is Aeschynanthus mannii as per POWO specimens- one and GBIF specimens- one and two.
References: POWO (specimens- one) Catalogue of Life The Plant List Ver.1.1 IPNI GBIF specimens- one and two (High resolution specimens) India Biodiversity Portal