Key to the species of Prestonia from Peru 1. Corolla tube and lobes pubescent outside, the indument ferruginous, yellow to yellowish-brown; intra- or interpetiolar colleters conspicuous .............................................................................................................................................. 2 - Corolla tube and lobes glabrous or minutely and inconspicuously puberulent outside (P. vana), the indument not ferruginous or yellow; intra– or interpetiolar colleters inconspicuous ............................................................................. 6 2. Free corona lobes inserted about the midway of the corolla tube, the apices always included; sepals 2.5–4.0 mm long; corolla tube 4–6 mm long ....................................................................................... P. parviflora (Benth.) Benth. - Free corona lobes inserted near the corolla mouth, the apices exserted or at least attaining level of the mouth; sepals 7.0–19.0 mm long; corolla tube 11–19 mm long ......................................................................................................... 3 3. Leaves hirsute abaxially, trichomas erect .................................................................................. P. ipomaeifolia A.DC. - Leaves not hirsute abaxially, trichomas irregularly adpressed ................................................................................... 4 4. Inflorescence basally branched, the branches short, sometimes hide behind the bracts; follicles minutely and inconspicuously sericeous; seeds 15–22 mm long ....................................................................... P. surinamensis Müll.Arg. - Inflorescence unbranched; follicles conspicuously hirsute or hispid; seeds 8–14 mm long ...................................... 5 5. Inflorescence a dichasial cyme, simple and elongate; follicles 15–18 cm long .................... P. racemosa J.F.Morales - an umbeliform cyme, agglomerate; follicles 5–13 cm long ........................................................... P. tomentosa R.Br. 6. Corolla tube lacking corona lobes inside..................................................................................................................... 7 - Corolla tube with corona lobes inside ......................................................................................................................... 9 7. Bracts 5.0–25.0(–30.0) mm long, foliaceous to subfoliaceous; corolla lobes pinkish–yellow, reddish–yellow to purplish–yellow; sepals (8.0–)10.0–22.0 mm long ............................................................ P. riedelii (Müll.Arg.) Markgr. - Bracts 0.7–3.0 mm long, scarious; corolla lobes cream to yellow; sepals 2.9–8.0 mm long ...................................... 8 8. Corolla tube 11.0–17.0 mm long; anthers 4.5–6.0 mm long ............................................... P. coalita (Vell.) Woodson - Corolla tube 7.5–8.5 mm long; anthers 3.1–3.3 mm long … P. succo J.F.Morales 9. Free corona lobes inserted about the midway of the corolla tube, the apices always included ................................ 10 - Free corona lobes inserted near the corolla mouth, the apices exserted or at least reaching the mouth ................... 12 10. Sepals 1–3(–4) mm long, the apex usually reflexed; inflorescence unbranched … P. quinquangularis (Jacq.) Spreng. - Sepals (8–) 9–18 mm long, the apex not reflexed; inflorescence branched, the branches short, but visible .............. 11 11. Bracts 1.0–5.0 × 0.5–1.0 mm, scarious; leaf blades 4.5–22.0 cm wide, coriaceous; wet forest ................................... ............................................................................................................................................... P. annularis (L.f.) G.Don - Bracts 7.0–11.0 5 3.0–4.0 mm, foliaceous; leaf blades 1.6–4.0 cm wide, membranaceous; dry forest ........................ .............................................................................................................................. P. parvifolia K.Schum. ex Woodson 12. Leaf blades membranaceous; tertary veins not impressed; dry forest ................................................. P. mollis Kunth - Leaf blades coriaceous; tertary veins impressed and conspicuous; wet forest .......................................................... 13 13. Leaves densely ferruginous–puberulent abaxially; follicles densely and minutely ferruginous–tomentulose ............... ........................................................................................................................................ P. megagros (Vell.) Woodson - Leaves glabrous, or inconspicuously and sparsely puberulent and glabrescent abaxially ........................................ 14 14. Sepals mostly 3.0–8.0 × 1.0– 2.5 mm ....................................................................................... P. plumierifolia Markgr. - Sepals mostly 10.0–21.0 × 3.0–8.0 mm .................................................................................................................... 15 15. Corolla tube minutely and conspicuously puberulent outside; follicles winged, divaricate ............. P. vana Woodson - Corolla tube glabrous or inconspicuously papillate outside; follicles not winged or divaricate ............................... 16 16. Bracts 4.0–26.0 × 2.0–6.0 mm, foliaceous ................................................................................................................. 17 - Bracts 1.0–2.5 × 0.5–1.0 mm, scarious ...................................................................................................................... 18 17. Follicles 4–9 mm wide, seeds 14–16 mm long; bracts 8–25 mm long ............. P. rotundifolia K.Schum. ex Woodson - Follicles 11–13 mm wide, seeds 18–21 mm long; bracts 4–7 mm long ............................................. P. robusta Rusby 18. Inflorescence and young branchlets minutely and densely ferruginous-puberulent ................ P. amabilis J.F.Morales - Inflorescence and young branchlets glabrous or inconspicuously puberulent and glabrescent ................................ 19 19. Follicles membranaceous, 6–8 mm wide; inflorescences conspicuously branched, nectary totally covering ovary ..... ................................................................................................................................ P. portobellensis (Beurl.) Woodson - Follicles woody, 8–11 mm wide; inflorescences inconspicuously branched; nectary not covering ovary ................... .......................................................................................................................................... P. trifida (Poepp.) Woodson

Published as part of Morales, J. Francisco, 2011, Studies in the Neotropical Apocynaceae XLI: A new species of Prestonia (Apocynoideae, Echiteae) from Peru and a key to the Peruvian species, pp. 28-32 in Phytotaxa 29 on pages 30-31, DOI: 10.11646/phytotaxa.29.1.2, http://zenodo.org/record/4894372