With the new taxa of Cryptocoryne described here and previously, a new key is provided. The characters and measurements are from wild-growing accessions. Deviant specimens are not included in the key. For brevity, the term “limb” refers here to the limb of the spathe.

1. Limb with long cilia at margin C. ciliata
— Limb without cilia at margin 2
2. Leaf blade ± covered with hairs on abaxial surface and/or along margin 3
— Leaf blade glabrous 5
3. Leaf blade lanceolate, ± bullate; spathe 5–7 cm long, very narrow, kettle white inside C. uenoi
— Leaf blade ovate to shortly lanceolate, not significantly bullate; spathe 7-10(-12) cm long, broad, kettle ± purplish inside, often inflated 4
4. Limb abruptly narrowed into a tail, collar pronounced C. ferruginea var. ferruginea
— Limb gradually tapering into a tail, collar zone present C. fusca
5. Tube of spathe > 2Χ as long as limb 6
— Tube of spathe ≤ 2Χ as long as limb 15
6. Limb with reddish or purplish protuberances 7
— Limb ± smooth, yellow, brown or purple 9
7. Limb c. 1 cm wide, with black-purple, coarse protuberances on a white base, collar purple C. zaidiana
— Limb c. 0.5 cm wide, with fine protuberances, collar not purple 8
8. Limb ± recurved, with red protuberances, especially on margin, collar yellow with red spots; leaf blade ovate, occasionally slightly bullate C. pallidinervia
— Limb ± spirally recurved, with yellow to purple protuberances over whole surface, collar zone present; leaf blade lanceolate, bullate C. keei
9. Limb 0.5–1 cm wide, with a rather long, ± twisted apex 10
— Limb usually more than 1 cm wide, without a long tail or apex 11
10. Leaf blade 3–12 cm long, usually flat C. striolata
— Leaf blade 10–30 cm long, noticeably bullate C. hudoroi
11. Limb yellow to brownish, collar zone yellow 12
— Limb brownish to purple, collar zone purple or purple spotted 13
12. Limb 1–2 cm wide, tube 5-10(-15) cm long; leaf-margin plain C. cordata var. grabowskii
— Limb c. 0.5 cm wide, tube 4–6 cm long; leaf with a distinct, membranous, ciliate margin C. aura
13. Limb brownish purple, collar zone yellow-purple spotted C. Χ purpurea nothovar. borneoensis ----- (incl. C. edithiae)
— Limb purple, collar zone plain purple 14
14. Limb almost smooth, shiny purple, collar zone almost as wide as limb C. Χ batangkayanensis
— Limb rough or with protuberances, dull purple, collar zone c. ½ as wide as limb C. Χ purpurea nothovar. borneoensis
15. Limb white to silvery, occasionally pinkish, collar white or purple 16
— Limb purple or brownish to yellowish 19
16. Limb (collar zone) white, with a long, thin, purple tail C. erwinii
— Limb wholly white, silvery or pinkish, short or long, collar white or purple 17
17. Limb > 3 cm long, upright, white, surface with protuberances, collar purple 18
— Limb ≤ 3 cm long, if longer not upright, collar whitish C. regina
18. Leaves 5–8 together, blade 3-7 Χ 6-10 cm; spathe 15-20 cm long C. yujii var. yujii
— Leaves > 10, often > 25 together, blade 2-4 Χ 6-7 cm; spathe 7–10 cm long C. yujii var. hendrikii
19. Limb taper-pointed or with a long tail 20
— Limb neither taper-pointed nor with a tail 26
20. Leaves light green, blade vertically oriented, spongy, veins inconspicuous; distal part of limb red-purple, collar zone yellow, spotted red C. lingua
— Leaves various shades of purplish, blade ± horizontally oriented 21
21. Limb at base usually open circular in view, with a distinct collar, tail 10–15 cm long C. longicauda
— Limb at base not open circular in view, with or without a distinct collar, tail ≤ 10 cm long 22
22. Limb purple or yellowish, with ± rough protuberances 23
— Limb purple to dark purple, ± smooth 25
23. Limb with a long, filiform tail, kettle inflated C. ferruginea var. sekadauensis
— Limb with a long, but not filiform tail, kettle not inflated 24
24. Limb yellow(ish), throat purphsh spotted C. keei
— Limb purple, throat purple C. uenoi
25. Limb ± upright backward coiled, throat open C. striolata
— Limb forward obliquely twisted, throat hidden C. ideii
26. Leaf blade conspicuously bullate C. bullosa
— Leaf blade not conspicuously bullate 27
27. Limb upright or recurved, collar narrow, conspicuous 28
— Limb ± forward obliquely twisted, if ± upright then collar zone broad 29
28. Limb strongly recurved, with many distinctly regular, round protuberances, collar thick in view, ± horizontal in circular opening C. griffithii
— Limb upright, not recurved to any extent, protuberances rather small and ± distinct, collar thin, vertical, funnel-shaped C. sahalii
29. Limb brown, spotted C. noritoi
— Limb light to dark purple 30
30. Throat whitish silvery to pinkish C. regina
— Throat dark purple 31
31. Limb 1–1.5 cm long; leaves 5–15 cm long, blade not spongy, ± horizontally oriented C. bastmeijeri
— Limb to 3 or 3–5 cm long; leaves 5–20 or 20–25 (-30) cm long, ± spongy, vertically or horizontally oriented 32
32. Limb to 3 cm long; leaves 20-25 (-30) cm long, ± vertically oriented, green C. isae
— Limb 3–5 cm long; leaves 5–-20 cm long, ± horizontally oriented, green or with silvery purplish markings C. auriculata