Euonymus

Savinov, Ivan A., Son, Hoang Thanh, Thang, Nguyen Toan & Nguyen, Vo Dai, 2024, Euonymus echinatus, a new record for the Flora of Vietnam, the species lectotypification and the key for identification of Vietnamese species of the genus Euonymus (Celastraceae), Phytotaxa 633 (2), pp. 155-162 : 159-160

Key to the sections and species of Euonymus in Vietnam

(Partly based on: Blakelock 1951, Ma 2001, Hou et al. 2010)

Two Chinese species, E. clivicolus W.W.Sm. (1917: 31) & E. frigidus Wall. in Roxb. (1824: 409) (incl. E. taliensis Loes. (1913: 3) ), are included only provisionally, on the basis of their possible occurrence in northern provinces of Vietnam. Both species are occurs in Laos ( Newman et al. 2007), but not mentioned for the country by Du et al. (2016). One more species, E. hemsleyanus Loes. (1902: 460) , actually distributed of Yunnan Prov., China ( Du et al. 2016), but not mentioned in the «Flora of China » ( Ma & Funston 2008), included also in the key, because there are field observations by Hoang Thanh Son in the Ha Giang Prov., North Vietnam (limestone mountains).

Examined specimens of E. taliensis Loes. (P!): Poilane 28450, Laos, 1938; Poilane 28617, Laos, 1938

1. Winter buds usually conic, markedly acute, large. Stamens without filaments, subsessile, anthers of one theca, dehiscing by one continuous split. Capsules winged (subgenus Kalonymus , sect. Uniloculares).................................................................................2

− Winter buds usually ovoid, acute, small. Stamens with filaments or (rarely) subsessile, anthers with two thecae, dehiscing by two distinct splits. Capsules globose or lobed, without wings (subgenus Euonymus )..............................................................................3

2. Leaves evergreen or semipersistent. Flowers and fruits always 4-merous. Wings of capsule short, less than 6 mm long.................. ................................................................................................................................................................... E. frigidus Wall. in Roxb.

− Leaves deciduous. Flowers and fruits usually 5-merous, sometimes combined with 4-merous. Wings of capsule more than 1 cm long.................................................................................................................................................................. E. clivicolus W.W.Sm.

3. Ovary densely papillose at base, capsules echinate, prickly or tuberculate (sect. Echinococcus ) .....................................................4

− Ovary not papillose, capsules smooth or rugose, not echinate, prickly or tuberculate ......................................................................7

4. Fruits densely covered with large subulate prickles...........................................................................................................................5

− Fruits covered thin, needle-shaped spines (prickles) (2)3(4) mm long, flattened ..............................................................................7

5. Prickles numerous, smaller, 1–1.5(2) mm long...................................................................................... E. echinatus Wall. in Roxb.

− Prickles fewer, 2–3.5(4) mm long .................................................................................................................... E. hemsleyanus Loes.

6. Inflorescences more than 10 cm long, with more than 10 flowers. Leaves and capsules not pubescent.......... E. balansae Sprague

− Inflorescences less than 9 cm long, with fewer than 9 flowers. Leaves and capsules pubescent ................. E. acanthoxanthus Pit.

7. Capsules unlobed, smooth, rounded or globose (sect. Ilicifolia ) .......................................................................................................8

− Capsules lobed, usually rugose and angulate (sect. Euonymus ).......................................................................................................12

8. Capsule white-spotted at maturity ......................................................................................................................................................9

− Capsule without white spots at maturity ..........................................................................................................................................10

9. Leaves sessile or with very short petiole less than 3 mm long, base round or cordate. Capsule without light colored grooves at maturity.................................................................................................................................................................... E. petelotii Merr.

− Leaves with short petiole 4–9 mm long, base cuneate. Capsule with light colored grooves at maturity.......... E. pseudovagans Pit.

10. Inflorescences longer, with peduncles 7–8 cm long, flowers numerous. Fruits much larger, 8–10 mm in diam ................................ ............................................................................................................................................................... E. tonkinensis (Loes.) Loes.

− Inflorescences short, flowers few. Fruits 5–6(10) mm in diam........................................................................................................11

11. Scandent or radicant subshrub, sometimes dwarf trees. Branchlets often with aerial roots. Leaves smaller, over 2 cm long ............ ...................................................................................................................................................... E. fortunei (Turcz.) Hand. -Mazz.

− Straight shrub or small tree. Leaves more large, 3–7 cm long in typical form ................................................. E. japonicus Thunb.

12. Flowers large, more than 1 cm in diam., 4-merous, disc large, 6–8 mm in diam., ovules usually 3–12 per locule. Capsule obtuse to rounded............................................................................................................................................................. E. grandiflorus Wall.

− Flowers small, less than 1 cm in diam., 5- or 4-merous, disc small, 2–5 mm in diam., usually 2 ovules per locule. Capsule retuse or apiculate, angled...........................................................................................................................................................................13

13. Evergreen shrubs with scandent shoots or vines 2–15 m high. Flower and fruits 4-merous, with quadrangular non-lobed disk. Ovary 4-lobed, with 2 ovules in each lobe .......................................................................................................................................14

− Evergreen erect shrubs or small trees. Flowers and fruits 5- or 4-merous .......................................................................................15

14. Branches rough, quadrialate. Leaves elongatedlanceolate, 5–7 cm × 2–4 cm. Inflorescences small, 2–3 cm, few-flowered. Anthers with stiff bristles, ovary smooth ...................................................................................................................... E.eberhardtii Tardieu

− Branches striped. Leaves elongated elliptic, 15–20 cm × 5–10 cm. Inflorescences up 10–12 cm long, many-flowered. Anthers glabrous, ovary surface scalariform .................................................................................................................... E. poilanei Tardieu

15. Flowers and fruits 5-merous, sometimes 4-merous. Petals with ciliate, dentate or fimbriate margins. Capsule pear–shaped (obovate)...........................................................................................................................................................................................16

− Flowers and fruits 4-merous. Capsules angled and lobed, of variousshape. Petals with entire margins .........................................19

16. Three-dimensional shape of petals is flat. Petals overlapping each other. Flowers from pink to red and purple. Stamens subsessile ......................................................................................................................................................... E. laxiflorus Champ. ex Benth.

− Three-dimensional shape of petals laterally bent outwards. Petals do not overlap. Flowers multi-colored (from white to yellow and green with red or purple strokes plus red spots on petals or sepals). Stamens with filaments or subsessile ...................................17

17. Flowers or fruits single or several on a short, tubercular glomerule, very rarely in obscure or very short pedunculate simple cymes.................................................................................................................................................... E. indicus B. Heyne ex Wall.

− Flowers or fruits in distinctly branched lax pedunculate cymes ......................................................................................................18

18. Petals broadly obovate, c. 4.5 by 4 mm, areolate inside, margin usually fimbriate. Stamens with filaments. Fruits broadlyobovoid or subglobose, c. 10 mm long and wide .................................................................................................... E. cochinchinensis Pierre

− Petals usually suborbiculate, sometimes broadlyobovate, 2–3 mm long and wide, smooth inside, margin minutely dentate; flowers sometimes with red spots on petals or sepals. Stamens subsessile. Fruits slightly broadlyobovoid, 8–15 by 12–17 mm ................... ................................................................................................................................................................................... E. glaber Roxb.

19. Leaves to 16 cm long or more, saliciform........................................................................................................... E. salicifolius Loes.

− Leaves less than 13 cm long.............................................................................................................................................................20

20. Leaves long and narrowly lanceolate (saliciform), pubescent ............................................ E. pittosporoides C.Y.Cheng ex J.S.Ma

− Leaves usually oblong to ovate, glabrous................................................................................................................ E. nitidus Benth.