Bulbophyllum sect. Rhytionanthos (Garay, Hamer & Siegerist) J. J. Vermeulen, Schuiteman & de Vogel, 2014

Dang, Minh Quan, Averyanov, Leonid V., Dang, Van Son, Maisak, Tatiana, Bui, Van Huong, Tu, Bao Ngan & Truong, Ba Vuong, 2022, Bulbophyllum section Rhytionanthos (Orchidaceae) in Vietnam with description of new taxa and new national record, Phytotaxa 530 (3), pp. 257-270 : 259

The key for identification of species Bulbophyllum sect. Rhytionanthos in the flora of Vietnam

1. Lateral sepals caudate.........................................................................................................................................................................2

- Lateral sepals not caudate...................................................................................................................................................................3

2. Inflorescence with 1–5 flowers; upper margin of lateral sepals free in basal half; petal margin slightly erose; upper margin of stelidia erose ............................................................................................................................................................ 1 B. emarginatum

- Inflorescence with 1–2 flowers; upper margin of lateral sepals free only at base; petal margin irregularly dentate; upper margin of stelidia entire ................................................................................................................................................... 2 B. paraemarginatum

3. Lateral sepals verrucose, sparsely papillose or with clavate hairs, margin hairy...............................................................................4

- Lateral sepals smooth, glabrous, margin entire ..................................................................................................................................6

4. Pedicel and ovary, and base of sepals (from abaxial side) with clavate hairs; lip glabrous.......................................... 3 B. nodosum

- Pedicel and ovary, and sepals glabrous; lip hairy or papillose ...........................................................................................................5

5. Lateral sepals and lip margin sparely papillose............................................................................................................... 4 B. forrestii

- Lateral sepals verrucose; lip margin in basal half densely papillose............................................................................ 5 B. strigosum

6. Median sepal with entire margin ................................................................................................................................ 6 B. salmoneum

- Median sepal with denticulate or erose margin ..................................................................................................................................7

7. Pseudobulbs less than 1 cm apart; upper margin of stelidia dentate ..................................................................... 7 B. taeniophyllum

- Pseudobulbs spaced more than 1 cm apart; upper margin of stelidia entire.......................................................................................8

8. Median sepal broadly ovate, its margin slightly erose, at apex dentate, mucronate; petals narrowly ovate, apex with short seta, margin ciliate ............................................................................................................................................................. 8 B. truongtamii

- Median sepal ovate, dentate or erose, apex acute; petals ovate-triangular, apex acute, margin fimbriate.......................9 B. helenae