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Key to Asian and Australian Podostemaceae

Australia

Two genera (two subfamilies) and two species occur separately in northeastern and northwestern Australia: Cladopus queenslandicus in northern Queensland; Terniopsis australis in northern Northern Territory and northern Western Australia.

1A. Flowers 3-merous (perianths 3-lobed, stamens 2, ovary 3-locular, stigmas 3); leaves flattened, oblong or ovate, univeined
.......... Terniopsis australis
1B. Flowers 2-merous (tepals 2, filiform, stamens 1, ovary 2-locular, stigmas 2); leaves trifid with filiform middle segment and two short lateral segments, not veined

.......... Cladopus queenslandiqus

Bhutan, Nepal, N India and Myanmar

Podostemaceae in these regions are poorly known, so the key below is tentative.

One subfamily (Podostemoideae), three genera and four species are recorded from Bhutan, Nepal, N India and Myanmar.

1A. Roots ribbon-like, shoots on flanks of root.
.......... 2
1B. Roots crustaceous, shoots borne irregularly on upper surface of root.
.......... 3

2A. Capsules equally valved
.......... Polypleurum wallichii (N India, SE Myanmar)
2B. Capsules unequally valved
.......... Zeylanidium lichenoides (S & N India, Myanmar)

3A. Bracts 4–6, ovules per locule 20–30, stigmas cristate
.......... Hydrobryum griffithii (Bhutan, Nepal, N India)
3B. Bracts 2–4, ovules per locule 10–16, stigmas linear, entire
.......... Hydrobryum japonicum (Myanmar)

Cambodia and Vietnam

Two subfamilies (Tristichoideae, Podostemoideae), 2 genera and 2 species occur in Cambodia, and one subfamily (Podostemoideae), 2 genera and 4 species occur in Vietnam.

Cambodia
1A. Leaves lanceolate, univeined, bracts carinate, flowers 3-merous with 3-lobed calyx, 3 stamens, and 3 stigmas, capsule-ribs 9
.......... Cussetia carinata
1B. leaves filiform, not veined, bracts not carinate, flowers 2-merous with 2 reduced filiform tepals, 2 stamens, and 2 stigmas, capsule-ribs 8

.......... Polypleurum wallichii

Vietnam
1A. Roots subcylindrical or ribbon-like, shoots at sinuses between root branches, bracts digitate, stamens single, capsules globose, smooth
.......... 2
1B. Roots crustaceous, shoots scattered on upper surface of roots, bracts simple, stamens 2 with forked filaments, capsules ellipsoid, flattened, ribbed
.......... 3

2A. Stamens 1
.......... Cladopus fallax
2B. Stamens 2 with forked filaments
.......... Polypleurumwallichii

3A. Stigmas linear, capsule-ribs ca. 12–14
.......... Hydrobryum japonica
3B. Stigmas capitate, capsule-ribs ca. 20
.......... Hydrobryum minutale

China

Three genera (two subfamilies) and six species occur in eastern central, southern, and southwestern China: Terniopsis sessilis, Cladopus doianus and C. fukienensis in Fujian province; C. austrochinensis in Guangdong province and Hainan Island; Hydrobryum japonicum and H. griffithii in southern Yunnan province.

1A. Flowers borne along both sides of roots, 3-merous, with short leafy shoots and 2 entire opposite bracts; flower buds not covered by spathella; tepals 3, elliptic, alternate stamens, connate except for distal lobes; stamens 3; ovary locules 3, stigmas 3; capsules globose, 9-ribbed (ribs 3 per locule); roots compressed, subcylindrical; leaves borne on branches (ramuli), tristichous (one dorsal, two lateral-ventral), ovate, entire, vein 1 (subfam. Tristichoideae)
.......... Terniopsis sessilis
1B. Flowers near sides or on dorsal surface of roots, 2-merous, with bracts digitate or entire, more than 4 in 2 rows; leafy shoots absent; flower buds enclosed by globose or ellipsoid spathella (special covering) ; tepals 2, linear, on both sides of stamens, free; stamens 1 or 2 (if 2, filaments forked); ovary locules 2, stigmas 2; capsules globose, smooth or ribbed (ribs 5 or 6 per locule); roots compressed, subcylindrical, ribbon-like or foliose; leaves borne on roots, fascicled, linear (subfam. Podostemoideae)
.......... 2

2A. Stamen 1, simple; capsules globose, smooth, erect; bracts digitate, surface rough; roots compressed, subcylindrical or ribbon-like, with tufts of leaves along both sides of root (Cladopus)
.......... 3
2B. Stamens 2, forked; capsules ellipsoid, compressed, ribbed, appressed to roots; bracts boat-shaped, entire; roots foliose, with tufts of linear leaves scattered over dorsal surface (Hydrobryum)
.......... 5

3A. Roots 2.5 mm or more wide, ribbon-like, branching monopodially; bract bearing floral axes 3-–4 mm
.......... Cladopus doianus
3B. Roots to 1(–1.3) mm wide, compressed, subcylindrical, branching sympodially; bract bearing floral axes 3–6 mm long
.......... 4

4A. Bract bearing floral axes 3.5–6 mm long; bracts 12-20
.......... Cladopus fukienensis
4B. Bract bearing floral axes ca. 3 mm long; bracts 10 or fewer
.......... Cladopus austrosinensis

5A. Bracts 6; stigma subcristate, truncate or emarginate, not narrowed at apex; ovules borne over septa surface except in lower central area, 24–26 per locule; leaves 7–15 per tuft, 15–20 mm long
.......... Hydrobryum griffithii
5B. Bracts 4(–6); stigma linear, entire, narrowed toward apex; ovules on margin of septa, 20 per locule; leaves 8-10 per tuft, 6–10 mm long
.......... Hydrobryum japonicum

Southern India and Sri Lanka
Two subfamilies, i.e., Tristichoideae and Podostemoideae, containing 10 genera and 24 species occur in southern India and Sri Lanka. Probably there are undescribed species, and further field survey and taxonomic revision are needed.

1A. Leaves lanceolate, univeined, bracts carinate, flowers 3-merous with 3-lobed calyx, 3 stamens, and 3 stigmas (Tristichoideae)
.......... 2
1B. Leaves filiform, nonveined; bracts linear-deltoid or ovate, flowers 2-merous with 2 reduced filiform tepals, 1- or 2-stamens with forked filament, and 2 stigmas (Podostemoideae)

.......... 5

2A.Roots subcylindrical
.......... 3
2B.Root absent, shoots crustaceous or broadly ribbon-like, leaves on dorsal surface and marginal part of shoot
.......... 4

3A.Shoots cylindrical, large, many branched many times, leaves around stem
.......... Indotristicha ramosissima
3B.Shoots subcrustaceous, dorsiventral with dorsal and lateral-marginal leaves
.......... Indodalzellia gracilis

4A.Holdfast absent, shoots broadly ribbon-like, leaves directly attached to shoot surface
.......... Dalzellia zeylanica
4B.Holdfasts root-like, shoots crustaceous, leaves 4-tristichous on short shoots borne on flattened shoot
.......... Indotristicha tirunelveliana

5A.Capsules globose or ellipsoid, smooth; roots various; stamens 1 or 2
.......... 6
5B.Capsules ellipsoid, flattened, ribbed; roots crustaceous; stamens 2
.......... 11

6A.Stamens 1
.......... 7
6B.Stamens 2
.......... 8

7A.Capsules indehiscent, ovules 2 per ovary
.......... Farmeria metzgerioides
7B.Capsules dehiscent, ovules 4–14 per ovary
.......... Maferria (Farmeria) indica

8A.Shoots horizontal on noncrustaceous root, reduced (apparently absent), leaves and bracts 2-stichous
.......... 9
8B.Shoots erect on crustaceous root, 1–7 cm tall, leaves and bracts 4- or 6-stichous
.......... 10

9A. Roots ribbon-like, spathellas ellipsoid, partially covering mature flowers, capsules ellipsoid, flattened

.......... Hydrobryopsis sessilis
9B. Roots disk-like, spathellas funnel-like, flowers extruding from spathellas, capsules globose
.......... Griffithella hookeriana

10A. Shoots 4-7 cm long, leaves and bracts 4-stichous, capsule smooth
.......... Willisia selaginoides
10B. Shoots 1-2 cm long, bracts or leaves 6-stichous
.......... Willisia arekaliana

11A. Roots disk-like
.......... Polypleurum disciforme
11B. Roots elongate or crustaceous
.......... 12

12A. Capsule-valves equal
.......... 13
12B. Capsule-valves unequal
.......... 18

13A. Roots subcylindrical, ribbon-like or crustaceous
.......... 14
13B. Roots disk-like
.......... Polypleurum disciforme

14A. Roots crustaceous(?), bracts filiform above ovate base, ca. 20 mm long
.......... Polypleurum filifolium
14B. Roots subcylindrical or ribbon-like, bracts not so
.......... 15

15A. Roots floating, adhering at base, subcylindrical
.......... 16
15B. Roots creeping or only distally floating, ribbon-like
.......... 17

16A. Roots to 60 cm long, to 3 mm wide, not zigzag, flowers on flanks in proximal 1/3 of root, shoots in distal 2/3, capsule-stalks to 10 mm long
.......... Polypleurum elongatum
16B. Roots (shoots?) to 10-30 cm long, to 2 mm wide, zigzag, flowers along nearly entire length of root, capsule-stalks to 15 mm long
.......... Polypleurum dichotomum

17A. Roots to 50 cm long, distally floating, ovules 100 or more per locule
.......... Polypleurum stylosum
17B. Roots to 10 cm long, creeping, ovules to 50 per locule
.......... Polypleurum wallichii Polypleurum prostratum

18A. Roots subcylindrical or ribbon-like, shoots 2-3 cm long, flowers plural per shoot
.......... 19
18B. Roots crustaceous or ribbon-like, shoots reduced, flowers single per shoot
.......... 20

19A. Stamens 2, capsule-ribs 8, not undulate
.......... Zeylanidium subulatum
19B. Stamens 1, capsule-ribs 6 + indistinct 2, undulate
.......... Zeylanidium barberi

20A. Roots crustaceous, shoots scattered on upper surface of root
.......... 21
20B. Roots ribbon-like, sympodial, shoots at sinuses of distinctly unequal root branches
.......... 22

21A. Sterile shoots (hypocotyls and shoots) with many filiform leaves at tip present, stigmas 2-lobed
.......... Zeylanidium olivaceum
21B. Such sterile shoots absent, stigmas multilobed
.......... Zeylanidium maheshwarii

22A. Roots adhering, to 1.5 mm wide, leaves to 1 cm long
.......... Zeylanidium lichenoides
22B. Roots distally floating, to 0.4 mm wide, leaves to 6 cm long
.......... “Polypleurum” munnarense

Laos
Two subfamilies, 7 genera and 16 species occur in northern and southern Laos (two species also occur in central Laos); 4 Dalzellia species in northern Laos (Vientiane prov.); 2 Cussetia species in southern Laos (Champasak prov.); 1 Pododiscus species in northern Laos (Vientiane prov.); 3 Polypleurum species in northern Laos (Vientiane prov.); 1 Cladopus species in central and southern Laos (Khammouan prov., Champasak prov.); ca. 6 Hydrobryum species in northern Laos (Vientiane prov.). Many of the species are nomen nudum and should not be officially used.

1A. Leaves oblong, ovate-oblong or deltoid, midveined, flower bud enclosed by leafy cupule or naked, flower 3-merous with 3-lobed perianth (subfamily Tristichoideae)
.......... 2
1B. Leaves filiform, non-veined, flower bud enclosed by spathella, flower 2-merous with 2 minute, filamentous tepals (subfamily Podostemoideae)
.......... 5

2A. Root absent; shoots adhering to rock surface, crustose or broadly ribbon-like, dorsiventral with dorsal and lateral leaves; flower bud enclosed by cupule with many filiform leaves
.......... 3
2B. Roots creeping on rock surface and bearing shoots along flank; shoots horizontal or erect, terete, leafy; flower bud naked, leaves on flowering shoot carinate abaxially

.......... 4

3A. Shoots 1 – 2 mm wide; leaves on cupule monomorphic, filiform; ovules 22 – 33 per locule
.......... Dalzellia minima (in prep.)
3B. Shoots ca. 2 mm wide; leaves on cupule subdimorphic, dorsal leaves filiform, lateral-ventral leaves narrowly deltoid; ovules 42 – 54 per locule
.......... Dalzellia borealis (in prep.)

4A. Shoot comprising one middle vegetative and two lateral flowering branches, leaves on flowering branch 2 – 3 per file (6 files in total), pedicel to 7 mm long
.......... Cussetia diversifolia
4B. Shoot comprising one vegetative and one flowering shoot, leaves on flowering branch ca. 8 per file, pedicel 10 – 12 mm long
.......... Cussetia carinata

5A. Root absent; shoots long (to 1 m), branched, floating, base disk-like
.......... Pododiscus koyamae (in prep.)
5B. Roots adhering to rock surface, shoots reduced (to 2 cm)
.......... 6

6A. Roots subcylindrical to ribbon-like
.......... 7
6B. Roots crustose
.......... 13

7A. Roots subcylindrical, floating, attached to rock surface by disk-like base
.......... Hydrobryum ramosum (in prep.)
7B. Roots subcylindrical or ribbon-like, adhering to rock by ventral surface
.......... 8

8A. Bracts digitate, capsules smooth
.......... Cladopus pierrei
8B. Bracts entire, capsules ribbed
.......... 9

9A. Shoots (tufts of leaves) and flowers borne along flank of root between successive root branches and at sinuses of root branches, capsules 8-ribbed
.......... Polypleurum wallichii
9B. Shoots (tufts of leaves) and flowers borne only at sinuses of root branches, capsules 12–20-ribbed
.......... 10

10A. Spathella covering flower bud papillate
.......... 11
10B. Spathella smooth
.......... 12

11A. Roots 1.5–2 mm wide; bracts 2; spathellas to 2 mm long; capsule-stalks 1–1.5 mm long
.......... Polypleurum sessile (in prep.)
11B. Roots 2–3 mm wide; bracts 3–5; spathellas 3–4 mm long; capsule-stalks 5–6.5 mm long
.......... Polypleurum breve (in prep.)

12A. Roots ca. 2 mm wide; stamens 2
.......... Hydrobryum taeniatum (in prep.)
12B. Roots to 1 mm wide; stamen 1

……... Hydrobryum subcylindricum (in prep.)

13A. Flowering shoots erect, 7–14 mm long; bracts terete, spinulate; stamens 1, 8–10 mm long; ovaries unilocular

.......... Hydrobryum takakioides (in prep.)
13B. Flowering shoots appressed or oblique, up to 1.5 mm long; bracts flat, ovate; stamens 2, 2–7 mm long; ovaries 1- or 2-locular
.......... 14

14A. Root lobing sometimes associated with shoots at sinuses of root lobes; ovaries 1-locular, subsessile, stalks 0.1 – 0.5 mm long
.......... Hydrobryum subcrustosum (in prep.)
14B. Root lobing independent of shoots; ovaries 2-locular, stalks 1–3 mm long
.......... 15

15A. Holdfast absent; stamens forked 1/2 – 1/5 from top; ovules 9–27 per locule
.......... Hydrobryum vientianense (in prep.)
15B. Holdfasts scattered on ventral surface of root, wart-like; stamens forked 1/4 – 1/5 from top; ovules 22–49 per locule
.......... Hydrobryum erectum (in prep.)

Malesia

Two subfamilies, two genera and four species occur in Malesia: Terniopsis malayana in penisular Malaysia; Cladopus nymanii in Indonesia (Java, Flores, southern Sulawesi, northeastern East Kalimantan); C. javanicus in Java; C. queenslandicus in eastern Papua New Guinea.

1A. Flowers 3-merous (tepals forming 3-lobed tube covering flower bud, stamens 3, ovary 3-loculate, stigmas 3), capsule obovoid, 9-ribbed, spathella absent; bracts 2, entire, membranous; leaves oblong-lanceolate, univeined, 3-ranked on short shoots (ramuli) (subfam. Tristichoideae)
.......... Terniopsis malayana
1B. Flowers 2-merous (tepals 2 on both sides of stamen, free, linear, inconspicuous, stamen 1, ovary 2-loculate, stigmas 2), capsules globose, smooth-surfaced (not ribbed), flower bud enclosed by envelope called spathella; bracts many, digitate or lobed, thick; leaves simple (linear), lobed or digitate, not veined, 2-ranked or irregularly arranged (subfam. Podostemoideae)
.......... 2

2A. Shoots long (to 9 cm); bracts and leaves trifid with elongate middle lobe and small lateral lobes
.......... Cladopus queenslandicus
2B. Shoots short or long; bracts digitate; leaves simple or digitate
.......... 3

3A. Vegetative shoots short, comprising clusters of simple leaves; floriferous shoots to 1 cm long, capsules 1–2 mm long
.......... Cladopus nymanii
3B. Vegetative shoots to 5 cm long, as long as reproductive shoots, both bearing numerous digitate leaves, capsules 2–3 mm long
.......... Cladopus javanicus

Thailand

Podostemaceae are distributed throughout Thailand. Two subfamilies (Tristichoideae, Podostemoideae), 10 genera and 41 species occur: genera Hanseniella, Paracladopus and Thawatchaia are endemic to Thailand, and 35 species are endemic.

1A. Flowers 3-merous (perianths 3-lobed, stamens 3, ovary 3-locular, stigmas 3); leaves flattened, oblong or ovate, univeined
.......... Subfamily Tristichoideae (2)
1B. Flowers 2-merous (tepals 2, filiform, stamens 1–2, ovary 2-locular, stigmas 2); leaves filiform or vertically flattened, not veined
.......... Subfamily Podostemoideae (12)

2A. Root absent; shoot crustose or rarely broadly ribbon-like, leafy on dorsal surface and at margin (not on ventral surface); flower bud covered by leafy cupule
.......... 3
2B. Root subcylindrical or ribbon-like; shoot subcylindrical, simple or ramified; cupule absent, flower bud instead embraced by bracts
.......... 6

3A. Shoot 3–10 mm wide or wider; dorsal leaves arranged in branched longitudinal rows; pedicel 5–8 mm long, 2.5–4 times as long as ovar
.......... 4
3B. Shoot to 2.5 mm wide; dorsal leaves in 1–2 inconspicuous rows; pedicel 1.5–4 mm long, 1–2 times as long as ovary
.......... 5

4A. Dorsal leaves dense, fimbriate; lateral leaves narrowly deltoid, to 1.5 mm long; ovules ca. 30 per locule
.......... Dalzellia ubonensis
4B. Dorsal leaves sparse, separate; lateral leaves deltoid-lanceolate, to 2 mm long; ovules 50–60 per locule
.......... Dalzellia ranongensis

5A. Shoots 1.5–2.5 mm wide; pedicel 1.5–2 mm long, as long as ovary; ovules 50–60 per locule
.......... Dalzellia kailarsenii
5B. Shoots 1–1.5 mm wide; pedicel 2–7 mm long, longer than ovary (1.3–1.5 mm); ovules 30–50 per locule
..........Dalzellia angustissima

6A. Reproductive shoot-complex comprising 3 branches, middle vegetative, 2 laterals floriferous; flowering shoot 4–5 mm long with leaves below flower many, in 6 ranks, carinate
..........Cussetia diversifolia
6B. Reproductive shoot-complex comprising 1 floriferous and 1 to few vegetative branches (if plural, floriferous shoot medial); flowering shoot short with 2 or several bracts
.......... 7

7A. Vegetative shoots to 5 cm long, many times branched, sparsely leafy, distal part comprising ramuli; bracts several
.......... Terniopsis ramosa
7B. Vegetative shoots to 2 cm long, composed of ramuli with tristichous imbricate leaves, proximal part of shoot a few times branched; bracts 2
.......... 8

8A. Root 2–10 mm wide; ramuli 3–90 mm long; stamens 5–6 mm long; ovules 8–12 per locule
.......... Terniopsis ubonensis
8B. Root 0.2–1.5 mm wide; less than 20(–30) mm long, stamens to 1.5 mm long; ovules more
.......... 9

9A. Single ramulus associated with flower
.......... 10
9B. Several ramuli associated with flower (see also 10)
.......... 11

10A. Roots 0.2–1 mm wide; ramuli 2.2–3.5 mm long; stigmas as long as wide, sometimes one slightly longer than wide
.......... Terniopsis brevis
10B. Roots 0.7–1.5 mm wide; ramuli 4–7 mm long; stigmas linear-oblong
.......... Terniopsis minor (in prep.)

11A. Pedicels 2–4 mm long; stamens 2–4 mm long
.......... Terniopsis malayana
11B. Pedicels 5–10 mm long; stamens ca. 1.5 mm long
.......... Terniopsis chanthaburiensis (in prep.)

12A. Roots crustose
.......... 13
12B. Roots subcylindrical or ribbon-like
.......... 27

13A. Flowering shoots erect; bracts in 4 ranks, dimorphic, ventrals (facing root) bilobed, dorsals simple
.......... 14
13B. Flowering shoots appressed or oblique or only flowers erect; bracts in 2 ranks, uniform, simple or trilobed
.......... 15

14A. Capsules 2–2.5 mm long, ribs 12–16
.......... Hanseniella heterophylla
14B. Capsules 1.5–2 mm long, ribs 8
.......... Hanseniella smitinandii

15A. Bracts trilobed with middle lobe much longer than lateral lobes
.......... Thawatchaia trilobata
15B. Bracts simple with tips obtuse or sometimes acute or acuminate
.......... 16

16A. Stamens 2 with filament forked
.......... 17
16B. Stamen 1 with simple filament
.......... 25

17A. Bracts linear-lanceolate, acuminate; stigmas unequal
.......... 18
17B. Bracts deltoid, elliptic or ovate, obtuse or acute; stigmas equal or subequal
.......... 19

18A. Roots (crusts) ca. 0.5 mm thick, not markedly raised around tufts of leaves; bracts 2–3; stigmas unequal, forked below middle
.......... Hydrobryum bifoliatum
18B. Roots (crusts) up to ca. 1 mm thick, prominently raised around tufts of leaves; bracts 4–6; stigmas markedly unequal, forked above middle
.......... Hydrobryum kaengsophense

19A. Leaves oblique or appressed, tough; bracts deltoid, acute at apex; spathellas split longitudinally, stigmas subequal
.......... Hydrobryum tardhuangense
19B. Leaves patent, soft (but tough in H. khaoyaiense); bracts ovate or elliptic, obtuse at apex; spathellas ruptured irregularly (if split longitudinally, ovary 1-locular in H. somranii), stigmas equal
.......... 20

20A. Stigmas cristate, ovules 20–30 per locule
.......... Hydrobryum griffithii
20B. Stigmas entire or subentire, ovules 4–20 per locule
.......... 21

21A. Ribs on capsule 16–20; ovules 4–8 per locule
.......... 22
21B. Ribs on capsule 12–14; ovules 6–20 per locule (per placenta in 1-locular ovary)
.......... 23

22A. Root tissue around tufts of leaves not raised or slightly so; base of capsule lower than or as high as top of uppermost bract
.......... Hydrobryum loeicum
22B. Tufts of leaves rimmed by annular bulges of root; base of capsule higher than top of uppermost bract
.......... Hydrobryum phetchabunense (in prep.)

23A. Bracts 2–4, spathellas ruptured longitudinally; flowers and fruits erect; ovary 1-locular; ovules 6–12 per placenta
.......... Hydrobryum somranii
23B. Bracts 4(–6), spathellas ruptured irregularly near apex; flowers and fruits, like flowering shoots, appressed or oblique; ovary 2-locular; ovules 12–20 per locule
.......... 24

24A. Stigmas subentire, oblong or narrowly deltoid-lanceolate, emarginated, truncate, or obtuse at tip; ovules 12–20 on septum surface except in small lower central area; leaves 10–20 mm long
.......... Hydrobryum chiangmaiense
24B. Stigmas entire, linear, pointed at tip; ovules 11–15 on marginal surface of septum; leaves to 3 mm long
.......... Hydrobryum japonicum

25A. Ovary 2-locular; placentation axile; leaves somewhat tough
.......... Hydrobryum khaoyaiense
25B. Ovary 1-locular; placentation pseudo-central; leaves soft
.......... 26

26A. Roots (crusts) 0.1–0.2 mm thick; bracts 2–4; ovary ca. 1.5 mm long; ovules 9–13 per placenta
.......... Hydrobryum micrantherumvar.micrantherum
26B. Roots (crusts) 0.2–0.3 mm thick; bracts 3–5; ovary 1.5–2 mm long; ovules 13–23 per placenta
.......... var.crassum

27A. Bracts 3–4-lobed or digitate; capsules globose, smooth (or weakly striped) or ellipsoid, ribbed
.......... 28
27B. Bracts simple; capsules ellipsoid, slightly flattened, 8–15-ribbed
.......... 31

28A. Holdfasts present on ventral surface of root under tufts of leaves; tufts of leaves and flowering shoots borne on flank of root between successive root branches and at sinuses of root branches
.......... 29
28B. Holdfast absent; tufts of leaves and flowering shoots only at sinuses of root branches; bracts 3–4-lobed or digitate
.......... 30

29A. Bracts linear-oblong, with 2 small lateral basal lobes; capsules globose, smooth
.......... Paracladopus chiangmaiensis
29B. Bracts digitate; capsules ellipsoid, 12–14-ribbed
.......... Paracladopus chathaburiensis

30A. Bracts 3–4-lobed, lobes semicircular, thin, smooth
.......... Cladopus taiensis
30B. Bracts digitate, segments finger-like, thick, papillate with silica
.......... Cladopus fallax

31A. Stamens 2; capsule-ribs 8
.......... 32
31B. Stamen 1; capsule-ribs 8–15
.......... 33

32A. Tufts of leaves and flowering shoots at sinuses between root branches; bracts linear distal to ovate or ovate-lanceolate base; capsule-valves unequal
.......... Zeylanidiumcf.lichenoides
32B. Tufts of leaves and flowering shoots on flanks of root between successive root branches; bracts lanceolate or ovate-lanceolate, apex obtuse or sometimes acute; capsule-valves equal
.......... Polypleurum wallichii

32Ba. Roots ca. 5 mm wide; leaves to 5(–10) mm long; pedicels 5–8 mm long; ovary to 2.5 mm long
.......... var.wallichii
32Bb. Roots ca. 3 mm wide; leaves to 2.5 mm long; pedicels to 2–4 mm long; ovary 1.2–1.5 mm long
.......... var.parvum

33A. Tufts of leaves borne between successive root branches; capsule-ribs 8–12
.......... 34
33B. Tufts of leaves or shoots borne exclusively at sinuses of root branches; capsule-ribs 10–15
.......... 35

34A. Roots 2–4 mm wide; pedicels 6–7 mm long; ovary protruding from spathella at anthesis, 2-locular; stigmas much shorter than ovary; capsule-ribs 8
.......... Polypleurum schmidtianum
34B. Roots 1–1.5 mm wide; pedicels to 1 mm long; ovary mostly enclosed in spathella at anthesis, 1-locular; style plus stigmas as long as ovary or longer; capsule-ribs 10–12, inconspicuous
.......... Polypleurum longistylosum

35A. Shoots prominent with leaves exposed on elongate stems; flowers always or occasionally multiple per shoot
.......... 36
35B. Shoots comprising tufts of leaves, lacking stems; leaf-bases embedded within root; flower always 1 per shoot
.......... 37

36A. Roots 1–1.5 mm wide; shoots to 5 cm long, simple, erect; leaves 15–30 mm long; ovules 15–30 per locule
.......... Polypleurum erectum
36B. Roots 2.5–4 mm wide; shoots to 18 cm long, branched, bent at base and floating; leaves 30–70 mm long; ovules 50–70 per locule
.......... Polypleurum longicaule

37A. Bracts 4–6; pedicels 10–15 mm long; spathellas 4–6 mm long
.......... Polypleurum phuwuaens
37B. Bracts 2–4(–6); pedicels 2–8 mm long; spathellas 2–3 mm long
.......... 38

38A. Complex of flower bud and bracts not globose, bracts usually obvious, attenuate at apex or attenuate tip caducous
.......... Polypleurum wongprasertii
38B. Complex of flower bud and bracts globose, bracts inconspicuous (ovate or elliptic), not attenuate to apex, basal bracts rarely attenuate
.......... 39

39A. Roots 1–2 mm wide, stalk of capsule 2.5–4 mm long
.......... Polypleurum insulare (in prep.)
39B. Roots 2–3 mm wide, stalk of capsule 4–10 mm long
.......... 40

40A. Leaves 20–40 mm long, stigmas subdeltoid or deltoid-ovate, ovules 18–22 per locule
.......... Polypleurum longifolium (in prep.)
40B. Leaves 10–25 mm long, stigmas narrowly conical, pointed, ovules 15–20 per locule
.......... Polypleurum prachinburiense (in prep.)
40C. Leaves 5–20 mm long, stigmas semicircular, ovules 40–70 per locule
.......... Polypleurum sisaketense (in prep.)