Lasianthus

Q. T., Pham, S., Tagane, P., Souladeth, T., Yamamoto, P., Phonepaseuth, T., Vongthavone, D., Kongxaisavath, B. V., Truong & Dang, V. S., 2025, Two new records of Lasianthus (Rubiaceae) for the Flora of Laos, Rheedea 35 (1), pp. 39-45 : 42-44

Key to the species of Lasianthus in Laos

1. Flowers in pedunculate cymes ...................... 2

1. Flowers in sessile fascicles or solitary .......... 4

2. Corolla 13–14 mm long; peduncles 1–2 mm long; fruits globose, blue ............... L. japonicus

2. Corolla up to 12 mm long; peduncles more than 5 mm long; fruits obovoid, black ......... 3

3. Leaves blade elliptic or subovate, 1–2.5 × 0.5–1.5 cm; peduncles 0.5–1.5 cm long; bracts inconspicuous ................................... L. biflorus

3. Leaves blade ovate-oblong, 3.5–13 × 1.4–4.1 cm; peduncles 1.3–3 cm long; bract linear, ca. 2.2 mm long ...................................... L. laoticus

4. Bracts more than 3 mm long ........................ 5

4. Bracts less than 3 mm long ........................... 9

5. Bracts leaf-like ................................... L. hirsutus

5. Bracts lanceolate, subulate, linear, ovate, filiform ............................................................ 6

6. Leaf base cordate or rarely rounded ........................................................ L. attenuatus

6. Leaf base acute, obtuse or cuneate ............... 7

7. Secondary veins 15–17 pairs; stipules more than 15 mm long .................... L. harmandianus

7. Secondary veins 7–10 pairs; stipules up to 8 mm long .......................................................... 8

8. Stipules 3–8 mm long; bacts up to 5 mm long; corolla 5–6 mm long ................ L. chrysoneurus

8. Stipules 2–3 mm long; bracts up to 20 mm long; corolla 10 mm long .......... L. sikkimensis

9. Calyx tube shorter than lobes or as long as lobes .............................................................. 10

9. Calyx tube longer than lobes ...................... 11

10. Petioles 10–15 mm long; secondary veins 11 pairs; calyx lobes linear ................ L. chevalieri

10. Petioles 1–2 mm long; secondary veins 3–5 pairs; calyx lobes triangular ..... L. sarmentosus

11. Leaf blades with reticulate nervules; secondary veins more than 10 pairs .............................. 12

11. Leaf blades with parallel or subparallel nervules; secondary veins less than 10 pairs ................... 13

12. Stipules 4–5 mm long; calyx truncate ....................................................... L. repoeuensis

12. Stipules 1.5–3 mm long; calyx not truncate ... ........................................................... L. chinensis

13. Branches glabrous ............................. L. bolavenensis

13. Branches hairy .............................................. 14

14. Corolla 10–12 mm long; fruits ellipsoid, up to 10 mm in diam. .......................... L. verticillatus

14. Corolla 6–7 mm long; fruits globose or subglobose, up to 6 mm in diam. ............... 15

15. Branches densely appressed pubescent; leaf blades 12–24 cm long; fruits glabrous or puberulent ......................................... L. hookeri

15. Branches densely villous; leaf blades 7–10 cm long; fruits hirsute ....................... L. hispidulus