Microtropis

Savinov, Ivan A., Nuraliev, Maxim S., Kuznetsov, Andrey N., Kuznetsova, Svetlana P., Luu, Hong Truong, Tran, Huu Dang & Luong, Huu Thanh, 2019, Microtropis cerocarpa (Celastraceae), a new species from southern Vietnam, Phytotaxa 387 (2), pp. 140-148 : 146

Key to the sections and species of Microtropis in Vietnam

Partly based on: Merrill & Freeman (1940), Tardieu-Blot (1948), Hou (1966), Shui & Chen (2002b), Zhang & Funston (2008).

The Chinese species M. wui is included only provisionally, on the basis of its possible occurrence in Lao Cai province of Vietnam according to Zhang & Funston (2008); its holotype was found in ca. 8 km from the Vietnamese border ( Shui & Chen 2002b). The presence of M. tetragona Merr. & F.L.Freeman and M. triflora Merr. & F.L.Freeman in Vietnam indicated by Ban (2003) is still to be confirmed by specimen investigation. Microtropis discolor (Wall.) Arn. accepted by Zhang & Funston (2008) in sect. Microtropis is placed here into sect. Remotiflorae on the basis of its inflorescence type, i.e. compound dichasium with elongated axes. Section Cymosopaniculatae is absent from the flora of Vietnam.

1. Flowers in dense glomerate cymes with obscure branching pattern; peduncle mostly less than 1 cm long and cyme subsessile or sessile; flowers subsessile or sessile (sect. Microtropis )....................................................................................................................2

− Flowers in compound dichasia, loosely arranged (i.e. inflorescence axes mostly elongated); peduncle often more than 1 cm long; flowers clearly pedicellate (except for M. discolor and M. pallens ) (sect. Remotiflorae ).................................................................5

2. Rostrum at fruit apex 7–8 mm long............................................................................................................... M. rhynchocarpa Merr.

− Rostrum at fruit apex short (1–3 mm long)........................................................................................................................................3

3. Leaves subsessile; inflorescence probably several-flowered; fruit surface coated with wax granules ................................................ ...................................................................................................................................................... M. cerocarpa Savinov & Nuraliev

− Leaves distinctly petiolate, petiole 2.5–6 mm long; inflorescence 5– to 15–20-flowered; fruit surface smooth..............................4

4. Leaf blade ovate, broadly ovate or ovate-lanceolate, 7–13 × 2.5–8 cm; cymes generally 5-flowered ................................................ ................................................................................................................................... M. osmanthoides (Hand.-Mazz.) Hand.-Mazz.

− Leaf blade obovate or rhombic, 36–50 × 16–18 cm; cymes 15–20-flowered................................... M. wui Y.M.Shui & W.H.Chen

5. Cymes with 2–4(6) orders of branches, usually more than 7-flowered, longer than 3 cm, peduncle generally 1–3 cm or more long (0.7–1.7 cm in M. apiculata )..............................................................................................................................................................6

− Cymes with 1–2 orders of branches, less than 7-flowered, 1–3 cm long, peduncle ca. 1 cm or shorter............................................8

6. Cymes 5–7 cm long; capsule up to 2 cm long............................................................................................................... M. fallax Pit.

− Cymes 3–4 cm long; capsule ca. 1–3.5(5) cm long............................................................................................................................7

7. Leaf blade 6.5–13(15) × 2–4.5(7) cm, secondary veins (3–5)7–13 pairs; petiole 0.8–1.2 cm long; capsule 1.5–3.5 (up to ca. 5) cm long (including rostrum 0.5–1 cm long)......................................................................................... M. petelotii Merr. & F.L.Freeman

− Leaf blade 27 × 7.5 cm, secondary veins ca. 20 pairs; petiole 1.5 cm long; young capsule 1 cm long......... M. apiculata Ding Hou

8. Cymes with branches of first and second order short (0.5 cm long); flowers almost sessile; disk absent.........................................9

− Cymes with branches of first and second order longer than 0.5 cm; at least some flowers clearly pedicellate; disk present.........10

9. Leaves chartaceous, secondary veins 7–12 pairs ..................................................................................................... M. pallens Pierre

− Leaves thickly chartaceous or leathery, secondary veins 5–8 pairs ............................................................. M. discolor (Wall.) Arn.

10. Cymes usually 2.5–3 cm long; fruiting pedicels rugose.......................................................... M. chlorocarpa Merr. & F.L.Freeman

− Cymes 1.5 cm long; fruiting pedicels more or less smooth.............................................................................................................11

11. Branchlets terete; cymes 3-flowered; leaf blade narrow, 5.5–10 × 1–2.5(4) cm, with length: width ratio 4–5: 1, rectangularlanceolate or broadly oblanceolate .................................................................................................. M. triflora Merr. & F.L.Freeman

− Branchlets distinctly tetragonal; cymes 3–7-flowered (rarely more); leaf blade wide, 8–13 × 2.5–5 cm, with length: width ratio less than 3: 1, rectangular or elliptic, rarely broadly ovate ........................................................ M. tetragona Merr. & F.L.Freeman