Stellaria sect. Plettkea

Montesinos-Tubée, Daniel B. & Borsch, Thomas, 2023, Molecular phylogenetics and morphology reveal the Plettkea lineage including several members of Arenaria and Pycnophyllopsis to be a clade of 21 South American species nested within Stellaria (Caryophyllaceae, Alsineae), Willdenowia 53 (3), pp. 115-148 : 128-129

Key to the species of Stellaria sect. Plettkea

1. Plants annual; leaves thin; roots fibrous......... 2

– Plants perennial; leaves thick; roots mostly woody (except S. utcubambensis has fibrous roots...... 5

2. Petals 2–3 mm long; seeds 10–12 per capsule; internodes of vegetative stems very long, 1–1.5 cm long in upper part........................ S. galianoi

– Petals 0.8–1.8 mm long; seeds 2–6 per capsule; internodes of vegetative stems less than 1 cm long.... 3

3. Forming large mats 5–8 cm high and up to 30 cm in diam.............................. S. andina

– Forming small cushions 1–2 cm high and 2–10 cm in diam..................................... 4

4. Stamens 5, 0.2–0.4 mm long; seeds orbicular................................. S. pedunculosa

– Stamens 10, 0.3–0.4 mm long; seeds ovate.................................. S. apurimacensis

5. Flowers hermaphroditic (with pistils and stamens) 6

– Flowers pistillate or staminate (plants dioecious).. 17

6. Root fibrous; leaf blade linear, 0.5–1 mm long; calyx lobes mucronate with extending midrib.................................... S. utcubambensis

– Root woody and thick; leaf blade lanceolate or with broader outline,> 0.8 mm long; calyx lobes acute.. 7

7. Flowers in leaf nodes (not terminal); sepals 5–7 mm long......................... S. xanthophylla

– Flowers terminal; sepals 1.6–4.9 mm long........ 8

8. Margins of blades hirsute or ciliate, sometimes only densely ciliate near truncate base (in S. spinulosa ). 9

– Margins of blades glabrous................. 13

9. Leaf blade triangular; petals 5, deeply bifid..... 10

– Leaf blade lanceolate, ovate or oblong; petals 3–5, obtuse or bifid (if bifid then only 3 in number).. 11

10. Leaf sheath 1.4–1.7 mm long; petals 4; stamens 4; capsule 2–2.2 mm long............ S. cryptantha

– Leaf sheath 0.8–1 mm long; petals 5 (rarely 4); stamens 5; capsule 1.5 mm long..... S. macrophylla

11. Flowers distinctly pedunculate (peduncle 2–2.9 mm long); plants forming mats with decumbent stems up to 50 cm long.................... S. spinulosa

– Flowers very shortly pedunculate (peduncle 0.1–0.5 mm long); plants forming dense small cushions not more than 12 cm in diam.................... 12

12. Stamens 3 (rarely 4 or 5 in flowers on same plant), antisepalous................... S. keraiopetala

– Stamens 5, episepalous............ S. engleriana

13. Shrub with branches woody in lower part; petals deeply bifid......................... S. laevis

– Plants herbaceous; petals obtuse at apex....... 14

14. Forming small tussock-like cushions up to 2 cm in diam.; root with a thick tuber........ S. macbridei

– Forming flat cushions 8–15(–20) cm in diam.; root not tuberous............................. 15

15. Margin of leaf blades thickened, densely ciliate at base with 1–3 mm long trichomes.. S. alpamarcae

– Margin of leaf blades not deviant in thickness, completely glabrous or with only very short (c. 0.1 mm long) trichomes........................... 16

16. Internodes of stems almost invisible; leaves rigid with midrib prominent on underside; seeds 0.2–0.3 mm long............................. S. congesta

– Internodes 0.1–0.3 mm long; leaves thick and glossy, midrib not prominent on underside; seeds c. 0.5 mm long............................ S. standleyi

17. Plants with densely lanuginose indumentum; leaf blades chartaceous, densely lanuginose at margin leaf sheath weak; style single.......... S. villasenorii

– Plants glabrous; leaf blades scarious, ciliate to denticulate at margin, leaf sheath strongly developed; styles 2- or 3-fid.......................... 18

18. Leaf blade 3–5 mm long; petals 0.3–1.5 mm long; capsules 1.5–2.9 mm long.................. 19

– Leaf blade 1.5–2.5 mm long; petals 0.3–0.5 mm long; capsules 1–1.5 mm long.................... 20

19. Inflorescence terminal, exserted; petals 1–1.5 mm long; capsules 2.5–2.9 mm long..... S. patagonica

– Inflorescence terminal, included; petals 0.4–0.5 mm long; capsules 1.5–1.8 mm long..... S. tetrasticha

20. Leaf margin sparsely ciliate, trichomes c. 0.05 mm long, leaf apex mucronate; sepals 1.2–1.5 mm long................................. S. smithii

– Leaf margin distinctly ciliate, trichomes 0.1–0.2 mm long, leaf apex acute to obtuse; sepals 1.6–2 mm long.......................... S. weberbaueri