Key for Paullinia Linnaeus.

1Cross section of stems with a central vascular cylinder, surrounded by three (sometimes only one) peripheral cylinders disposed in a triangular arrangement
1'Cross section of stems with a single vascular cylinder
2Inflorescence cauliflorous, fascicled, produced on mature, leaf-less stems
2'Inflorescence axillary or distal, produced on leafy branches, solitary or fascicled
3Petiole and leaf rachis winged; capsules unwinged;
3'Petiole and leaf rachis unwinged; capsules winged
4Inflorescence fascicled; capsules winged
4'Inflorescence solitary; capsules unwinged
5Plant pubescent; stipules 7-15 mm long; capsule globose or globose-trigonous
5'Plant glabrous or puberulent; stipules < 7 mm long, capsule pyriform
6Petiole and leaf rachis unwinged or margined
6'Petiole and leaf rachis winged
7Leaves 7-11-foliolate pinnate
7'Leaves 5-foliolate pinnate, trifoliolate or biternate
8Stipules < 5 mm long
8'Stipules > 1 cm long
9Fruit winged; inflorescence fasciculate
9'Fruit unwinged; inflorescence solitary
10Leaves biternate
10'Leaves 5-foliolate pinnate or trifoliolate
11Leaflets acuminate at apex; capsules winged; plant tomentose or tomentulose
11'Leaflets ligulate at apex; margins bidentate at apex; capsules unwinged; plant tomentulose or puberulent
12Leaves trifoliolate
12'Leaves 5-foliolate pinnate
13Leaflets abaxially flavo-sericeous-tomentose; capsules unwinged
13'Leaflets abaxially glabrous or barbate at vein angles; capsules winged (or unknown in P. anomophylla)
14Leaflets glabrous; petioles terete
14'Leaflets abaxially barbate or barbulate; petioles margined
15Fruit 9-winged (very short wings) or verrucose
15'Fruit 3-winged
16Calyx and capsules cinereus-sericeous, with 9 distal, short, divaricate wings
16'Calyx and capsules ferruginous, hirto-tomentose, with 9 longitudinal, wrinkled ridges
17Leaf rachis unwinged
17'Leaf rachis winged or margined
18Leaflets lustrous on both surfaces, with entire, or remotely subdentate margins; tertiary venation clathrate
18'Leaflets not lustrous, or if so only on adaxial surface, margins variously serrate or dentate; tertiary venation clathrate, subclathrate, or reticulate
19Capsules winged or triquetrous (narrowly winged)
19'Capsules unwinged (globose, ellipsoid or pyriform)
20Plant puberulent or glabrous
20'Plant pubescent, hispidulose, tomentose or setose (at least the young parts)
21Capsules ferruginous-tomentulose, with wing surrounding the coccus and slightly projecting beyond its apex and tapering on the stipe; seeds puberulent
21'Capsule glabrous, with dorsal, distal wings slightly projecting beyond the apex; seed glabrous
22Plant setose; stipules deeply dissected, to 1.5 cm long
22'Plant pubescent hispidulose, or tomentose; stipules minute, not dissected
23Leaflets obtusely acuminate at apex, capsules 2.5-3 cm long, the wings projecting beyond the apex, running through the lenght of the locule and tappering at base into an elongated stipe
23'Leaflets acuminate at apex; capsules otherwise
24Leaflets abaxially puberulous or glabrous, with subentire margins
24'Leaflets abaxially ferruginous or flavo tomentose, with repando-dentate margins
25Capsule with narrow, lengthwise dorsal wings
25'Capsule wings on distal portion of locule, elongated, divaricate
26Leaflets (chartaceous to coriaceous ac.desc.) coriaceous, abaxially ferruginous-sericeous, with serrate margins; inflorescence axillary racemiform
26'Leaflets chartaceous, abaxially pubescent, with remotely dentate margins; inflorescence cauliflorous, fascicled
27Body of fruit (locule) globose or ellipsoid, 8-10 mm long
27'Body of fruit (locule) clavate, ca. 20 mm long
28Stems 4-5-costate; stipules dissected
28'Stems terete, nearly terete or triangular; stipules entire or inconspicuous
29Stems hirsute-tomentose; stipules 1.5-2 cm long; bracteoles ca. 4 mm long, overlapping; cincinni congested along inflorescence rachis
29'Stems tomentulose, puberulent or glabrescent; stipules 2-4 mm long; bracteoles ca. 1 mm long, not overlapping; cincinni spaced out along inflorescence rachis
30Plant glabrous
30'Plant puberulent, tomentose, hirsute-tomentose, or hirsute
31Capsules with 9 longitudinal wrinkled ridges
31'Capsules without ridges or with 6 longitudinal, smooth ridges
32Leaflets with clathrate tertiary veins
32'Leaflets with reticulate tertiary veins
33Leaflet margins entire for most part, sometimes with a few teeth near the base or near the apex
33'Leaflet margins serrate or remotely glandular serrate
34Capsule depressed-globose or globose-trigonous, minutely pubescent or glabrous, woody-crustose, wrinkled when dried
34'Capsules ellipsoid, unwinged, 6-costate, sericeous-pubescent
35Capsule obovoid, globose, ovoid, or ellipsoid, slightly chartaceous, 6-ridged, ferruginous-tomentose, long-stipitate
35'Capsules, globose, smooth, crustose, (drying wrinkled) glabrous, shortly stipitate
36Plant glabrous; capsule nearly globose, glabrous, coriaceous, with 6 longitudinal sulci, 1.2-1.5 × 1.2-1.5 cm; mesocarp ca. 1 mm thick; endocarp glabrous; seed one per fruit.
36'Plant tomentose, becoming glabrous; capsule obovoid to depressed-globose, sericeous-tomentose, slightly rugose, 3-3.5 × 3-3.7 cm; mesocarp ca. 3 mm thick, endocarp puberulent; seed (1) 2 per fruit
37Fruit winged
37'Fruit not winged
38Stem trigonous to subterete; leaflets abaxially glabrous or puberulent, with minute dark papillae, the margins not ciliate; capsule wing surrounding most part of coccus
38'Stem terete; leaflets abaxially pilose along midvein, the margins ciliate; fruit wings on upper half of coccus ascending or slightly divaricate
39Capsule ferruginous-tomentose
39'Capsules glabrous
40Capsules crustose, drying wrinkled
40'Capsules woody or coriaceous
41Capsules nearly globose, long stipitate; leaflets with minute hairy domatia at the secondary veins axils on abaxial surface
41'Capsules pyriform; leaflets without domacia
42Bracts oblong, 7-10(15) mm long; stipules 2-4.5(7) cm long
42'Bracts subulate, 1-3 mm long; stipules 0.5-1(2.5) cm long
43Stipules 0.5-1 (2.5) cm long; petiolules of lower pair of leaflets ca. 0.5 cm long; pericarp ca. 1 mm thick
43'Stipules ca. 0.5 mm long; petiolules of lower pairs of leaflets 2-2.5 long; pericarp ca. 4 mm thick