Bull. Natl. Mus. Nat. Sci., Ser. B, 37(1), pp. 1–8, February 22, 2011

Taxonomic Enumeration of Podostemaceae of Cambodia and Vietnam
Masahiro Kato
Department of Botany, National Museum of Nature and Science,
Amakubo 4–1–1, Tsukuba, 305–0005 Japan
E-mail: sorang@kahaku.go.jp(Received 7 November 2010; accepted 22 December 2010)

Abstract This is a preliminary floristic report of Podostemaceae in Cambodia and Vietnam. It
enumerates two genera and three species in Cambodia and three (probably two) genera and four
species in Vietnam. They include new records of Polypleurum wallichii and P. schmidtianum from
Cambodia, and an apparently local species, Diplobryum minutale, endemic to southern Vietnam.
They represent two subfamilies, Podostemoideae and Tristichoideae. Identification of Hydrobryum
japonicum occurring in northern Vietnam is verified. Podostemaceae of Cambodia and Vietnam
are still poorly known and need further exploration.
Key words : aquatic plants (river-weeds), Cladopus, Diplobryum, Hydrobryum, Polypleurum,
Terniola.

Introduction
Postemaceae are an aquatic eurosids I angiosperm family that is the most closely related
to Hypericaceae (Soltis et al., 2000; Savolainen
et al., 2000; Gustafsson et al., 2002; Davis et al.,2005; Tokuoka and Tobe, 2006; Wurdack andDavis, 2009) and distributed in the tropical towarm-temperate seasonal-climates of the world(Kato, 2006b). Vegetative plants grow submergedon rock surfaces in rapids and waterfalls during
the rainy season, when the water level is high,and subsequently plants are exposed and dried,
while flowering and fruiting during the dry season, when the water level is lowered. In thisextreme environment, the plants adhere to thewater-worn rock surfaces by the creeping roots or
shoots, or their disk-like bases (Rutishauser,
1997; Cook and Rutishauser, 2007). All speciesof Cambodia and Vietnam have roots that aresubcylindrical, ribbon-like or crustose (foliose).
It is suggested that large-gap morphologicalchanges happened in the evolution of Podostemaceae. Partly because of such ecology andphenology, Podostemaceae have been relatively

rarely collected. Nonetheless, recent studies withincreasing specimens have discovered thespecies-rich Podostemaceae in Thailand, Laos,and India (Kato, 2004, 2006a; Kato and Koi,
2009; Koi and Kato, 2010; S. Koi and M. Kato,
unpubl. data; Asian Podostemaceae website:
http://www.kahaku.go.jp/research/db/botany/
podostemaceae/1index.html).
Podostemaceae in Cambodia and Vietnam, incontrast, are little known at present. The firstrecord was made by Lecomte (1909) who described Terniola carinata from Cambodia andLaos. Cusset (1972) described Diplobryum minutale from southern Vietnam, and Cusset (1973a)
described Cladopus fallax and recorded C. pierrei, both from southern Vietnam, and Hydrobryum griffithii (see H. japonicum below) from
northern Vietnam. Then, those taxa were dealt
with by floristic studies of Cusset and Cusset(1988) and Cusset (1992).
This paper examines all described species ofPodostemaceae in Cambodia and Vietnam using
specimens from all recorded places, in hopes thatit provides useful material for further understanding the complete flora of the family. Recent col-

2

Masahiro Kato

lections include new records from Cambodia. As
a result of this study, I suggest that future exploration will discover the flora of the areas richer.
Key to the species of Cambodia and Vietnam
1a. Leaves lanceolate, univeined, bracts carinate,flowers 3-merous with 3-lobed calyx, 3 stamens, 3 stigmas, obtetragonal 3-locular capsules; Cambodia (subfamily Tristichoideae)                   1. Cussetia carinata
1b. Leaves filiform, not veined, bracts not carinate, flowers 2-merous with 2 reduced filiform tepals, 1 or 2 stamens, 2 stigmas, ellipsoidal or globose 2-locular capsules (subfamily Podostemoideae)                   2
2a. Roots ribbon-like                      3
2b. Roots crustose                        6
3a. Tufts of leaves and flowering shoots borne on
flank of root, bracts simple, capsules ellipsoid, flattened, ribbed                   4
3b. Tufts of leaves and flowering shoots borne at
sinuses between root branches, bracts digitate, capsules globose, smooth           5
4a. Roots to 6 mm wide, stamens 2, capsules to 2
mm long, stalks to 15 mm long; SW Cambodia              2. Polypleurum wallichii
4b. Roots 2–3 mm wide, stamens 1, capsules
1.2–1.7 mm long, stalks 4–9 mm long; SW
Cambodia   3. Polypleurum schmidtianum
5a. Stamens 1; S Vietnam   4. Cladopus fallax
5b. Stamens 2 with forked filaments; S Vietnam                    5. Cladopus pierrei
6a. Bracts 4–5, capsule-ribs 12; N Vietnam              6. Hydrobryum japonicum
6b. Bracts 6–8, capsule-ribs ca. 20; S Vietnam                7. Diplobryum minutale
1. Cussetia carinata (Lecomte) M. Kato, Acta
Phytotax. Geobot. 57: 54. 2006—Terniola carinata Lecomte, Bull. Soc. Bot. Fr. 56: 96. 1909;
Fl. Gén. Indochin. 5: 45, f. 5A, B, 1–4. 1926—
Lawia carinata (Lecomte) Koidz., in Doi, Fl.
Satsum. 1(4): 53. 1929—Dalzellia carinata(Lecomte) C. Cusset, Fl. Cambodge, Laos, ViêtNam 14: 78, pl. 12, f. 4–7. 1973; Cusset & Cus-set, Bull. Mus. Natl. Hist. Nat. Paris, 4e sér., sect.
B, Adansonia 10(2): 173. 1988. Type. Cambodia,
M. Julien s.n., 6 June1874 (P!) (lectotyped byCusset [1973b]).
Root creeping, adhering to rock surface, ribbon-like, 1–2 mm wide, branched, with many
shoots rather closely arranged (0.5–1 mm apart)on both flanks. Shoot aggregations comprisingfloriferous shoot usually associated with much
shorter vegetative shoot; vegetative shoot flattened (in dry specimens), 1.5–4 mm long,
0.5–0.7 mm thick including scales, scales shorter
than wide, to 0.5 mm long; flowering shoots 5–9
mm long excluding flowers, 1.5–2.5 mm wide including leaves, leaves (bracts) in 6 ranks, 5–9 per
rank, deltoid-ovate, apex obtuse, keeled in middle on abaxial surface, oblique, subfalcate,
1.5–2.5 mm0.5–1 mm, thick, upper leaves larger, coriaceous; flower 1, at shoot apex; pedicelled; tepal ca. 2.5 mm long, lobed 2/5–1/2 tobase, lobes 3, membraneous, univeined, pale; stamens 3, alternate to tepal-lobes, longer thanovary, 1.5–3.3 mm long, filaments membraneousin basal half, anthers deltoid; ovary 3-locular, obdeltoid-ellipsoidal, apex subtruncate, 1.2–2.5 mm
long, 0.8–1.7 mm wide, placentation axile; stigmas 3, separate from each other, ca. 0.5 mm long,multilobed; capsule stalked (stalks 5–10 mmlong), obovoid, trigonous, ribs 9; seeds ellipsoid,
warty.
Specimen examined. Cambodia, Julien s.n.
(P!).
Distribution. Cambodia, Laos (southern).
Notes. Cussetia carinata is most similar andclosely related to C. diversifolia, the otherspecies of the bispecific genus, in the absence ofobvious bracts, carinate leaves in 6 ranks on theprominent flowering shoot, and tepal-like, palefilaments. Therefore, the two species are classified as congeneric (Kato, 2006a). Cussetia diversifolia is distinct from C. carinata in the shootcomprising a middle vegetative and two lateral
flowering branches (vs. a vegetative and a flowering branch in C. carinata), carinate leaves on thevegetative shoot (vs. scale-like), 2 or 3 leaves per
rank on flowering shoots (vs. 5–9), and stigma

Podostemaceae of Cambodia and Vietnam

3Fig. 1. Polypleurum in Cambodia. Photo taken by L. Cecilio in Thma Baing District, Koh Kong Province, Cambodia in December 2008. A, B. Polypleurum wallichii. Pink flowers are borne on flanks of ribbon-like roots.
C, D. Polypleurum schmidtianum. Stalked capsules with 8 ribs are erect on roots and flowers have single stamens with pale, ruptured anthers.

filamentous, entire (vs. branched, lobulate). Cussetia carinata is distributed in Cambodia andsouthern Laos, while C. diversifolia occurs ineastern Thailand (Lecomte, 1926; Cusset, 1973b;
Cusset and Cusset, 1988; Kato, 2006a). It is the
only species of subfamily Tristichoideae from
Cambodia, and no species is recorded from Vietnam (Kato, 2006b; for differences from Podostemoideae see Key 1).
Cussetia is similar to Terniopsis, one of six
genera of Tristichoideae, in the ramuli on theflank of the creeping root as well as the reproductive characters, but their phylogenetic relationship is uncertain.

2. Polypleurum wallichii (R.Br. ex Griff.)
Warm., Danske Vidensk. Selsk. Skrift., ser. 6,
Nat. Math. 11(1): 57. 1901; Cusset, Bull. Mus.
Natl. Hist. Nat. Paris, 4e sér., sect. B, Adansonia
14(1): 42, f. 8. 1992; Raveendran & Mathew,
Rheedea 2: 106, f. 1. 1994; Kato, Acta Phytotax.
Geobot. 57: 36. 2006—Podostemum wallichii R.
Br. ex Griff., Asiat. Res. 19: 103, tab. 17. 1836—
Dicraeia wallichii (R.Br. ex Griff.) Tul., Ann.
Sci. Nat. ser. 3, 11: 101. 1849; Willis, Ann. Roy.
Bot. Gard. Peradeniya 1: 223. 1902. Type. India:
Cherrapunji, Griffith s.n. (K!).
Dicraeia minor Wedd., in DC., Prodr. 17: 71.
1873; Willis, Ann. Roy. Bot. Gard. Peradeniya 1:4Masahiro Kato

223. 1902—Podostemum minor (Wedd.) Benth.,
in Benth. & Hook. f., Gen. Pl. 3: 112. 1880;
Hook. f., Fl. Brit. Ind. 5: 67. 1886—Polypleurum
minor (Wedd.) Nagendran, Arekal & Subramanyan, Plant Syst. Evol. 128: 217. 1977. Type.
India: Mts. Khasi, Griffith 2437 (holotype K!,
isotype P).
Dicraea wallichii (R.Br. ex Griff.) Tul. var.
khasiana Willis, Ann. Roy. Bot. Gard. Peradeniya 1: 224. 1902. Syntypes. India: Maomloo
River, Cherrapungi, Wallich; Sylhet rivers,
Gomez; Sylhet Mts., Griffith, Hooker, Clarke,
Willis (C!).
Dicraea wallichii (R.Br. ex Griff.) Tul. var.
striata Willis, Ann. Roy. Bot. Gard. Peradeniya
1: 225. 1902. Syntypes. Myanmar: Moulmen,
Lehmann 3; Wallich 33; Parish s.n. (K!).
Root attached to rock by base, distally free,
floating, ribbon-like, to 6 mm wide, irregularly
and often branched. Flowering shoots on bothflanks of roots; bracts 4, lanceolate to ovatelanceolate, acute or acuminate, apex often caducous; flower 1, bud covered by spathella,spathella 2–4 mm long, ruptured near apex at
anthesis; pedicel 10–15 mm long; tepals 2, 1 oneach side of stamen, to 1.5 mm long; stamens 2,
branched below apex, as long as ovary or slightly
longer, 2.5–3 mm long, anthers caducous; ovary
ellipsoidal, slightly flattened, to 2.5 mm long;stigmas 2, equal, forked at base, filiform, to 1
mm long; ovules covering entire septum surface,
40–50 per locule; capsule ribs 8–9.
Specimens examined. SW Cambodia. Mondon
Satma district: Kabal Satian waterfall, Strung
Ruesay Chrum Kandal River, Phanom Sumkot
Wildlife Sanctuary, interior to Kaoh Kong City,
M. Wongnak s.n. (TNS). Koh Kong district:Thma Baing, Ruessei Chrum, 11°3939.2N,
103°2358.7E, 342 m alt., M. Newman et al.
2158 (TNS).
Distribution. Thailand (northern, central, eastern), India (northeastern, southern), Myanmar(southeastern), Laos (northern central, southern),
Cambodia (southwestern).
Note. This is a new record from Cambodia andisolated from the eastern and central Thailand

localities (Kato, 2006a). The Cambodian plants
are referable to var. wallichii.
3. Polypleurum schmidtianum Warm. in
Schmidt, Bot. Tidsskr. 24(3): 258. 1901; Danske
Vidensk. Selsk. Skrift. ser. 6. Nat. Math. 11(1):3, f. 1–6. 1901; Cusset, Bull. Mus. Natl. Hist.
Nat. Paris, 4e sér., sect. B, Adansonia 14(1): 38.
1992; Kato, Acta Phytotax. Geobot. 57: 40.
2006—Polypleurella schmidtiana (Warm.) Engl.,
Bot. Jahrb. Syst. 61: 9. 1927; Royen, Dansk Bot.
Ark. 23: 185. 1965. Type. Thailand: Klong Sarlakpet, Koh Chang, 600 ft, southeastern, Schmidts.n. (C 3160) (C, not seen).
Root ribbon-like, 2–3 mm wide, irregularly
and often branched (vegetative plants not available). Flowering shoots on both flanks of root;
bracts 2–3 or possibly more, in 2 ranks, ca. 2 mm
long, sheathed, distally linear; flower 1, bud covered by ellipsoidal spathella, spathella ruptured
near apex at anthesis, ruptured spathella ca. 1.5mm long; pedicel 4–8 mm long; tepals 2, 1 oneach side of stamen, 0.5–0.7 mm long; stamen 1,
as long as ovary or longer, ca. 1.5 mm long;ovary 2-locular, ellipsoidal, slightly flattened,
1.2–1.7 mm long, 0.7–1 mm wide; stigmas 2,
subequal, forked at base, filiform, tapering toapex, 0.3–0.6 mm long; ovules covering entire
septum surface, ca. 35 per locule; capsule stalked(4–9 mm long), ribs 8.
Specimen examined. SW Cambodia. KohKong district: Thma Baing, Ruessei Chrum,
11°3939.2N, 103°2358.7E, 340 m alt., M.
Newman et al. 2159 (TNS).
Distribution. Thailand (southeastern, central[Cusset, 1992]), Cambodia (southwestern),northern central Laos (Bolikhamsai).
Note. This species has been regarded as endemic to Thailand, but it also occurs in northern
central Laos (S. Koi and M. Kato, unpubl. data).
This paper reports the third locality in southwestern Cambodia nearby Trat province and an offshore island, Ko Chang, southeastern Thailand(Kato, 2006a). In Cambodia, this occurs alongwith Polypleurum wallichii (M. Newman, person.
commun.).

Podostemaceae of Cambodia and Vietnam

4. Cladopus fallax C. Cusset, Fl. Cambodge,
Laos, Viêt-Nam 14: 72, pl. 10, f. 10, 11. 1973;
Kato, Acta Phytotax. Geobot. 57: 32. 2006. Type.
Vietnam: Massif du Lang Biang between Klou
and Da Nhim, Tuyên Doc, southern, 900–1200 m
alt., Chevalier 30946a (P!).
Cladopus nymanii auct. (non H. Möller); C.
Cusset, Bull. Mus. Natl. Hist. Nat. Paris, 4e sér.,sect. B, Adansonia 14(1): 22, f. 2, 4–7. 1992, p.p.
Root creeping, adhering to rock surface, ribbon-like, 1–2 mm wide, branched, with tufts ofleaves near edge on both flanks of root at all
sinuses of root branches (vegetative plants notavailable). Flowering shoot very short; bracts
6–12, in two ranks, digitate, lobes 5–8, oblong,
0.5–1 mm long, 0.2–0.3 mm wide, papillate withsilica; flower 1, pedicelled, bud covered byspathella, spathella globose, ca. 1 mm long, irregularly ruptured near apex at anthesis; tepals 2, 1
on each side of stamen, linear, ca. 0.8 mm long;stamen 1, to 1.3 mm long, longer than ovary;
ovary globose-ellipsoidal, 1–1.2 mm long, 0.8–1
mm thick, 2-locular, with 2 nearly verticalgrooves; septum hemispherical in central part,
margins membranous; stigmas 2, forked nearbase, ca. 0.4 mm long, linear to subulate, entire,procumbent; ovules covering entire septum surface, ca. 25 per locule. Capsule stalked (stalk to
1–1.5 mm long), globose, 1.5 mm long, smooth.
Specimen examined. S Vietnam: Massif duLang Biang, between Klou and Da Nhim, Tuyên
Doc, Chevalier 30946a (P).
Distribution. Thailand (southeastern), Vietnam(southern).
Notes. Cusset (1992) reduced Cladopus fallax
to C. nymanii in the very broad sense including
local species of China and Japan. This treatment
resulted in a polymorphic and widely distributed
C. nymanii; however, molecular evidence refutes
this Cusset’s (1992) lumping (Kita and Kato,
2001, 2004). Cladopus fallax is the most closely
related to C. taiensis (Koi et al., 2008). Morphologically, C. fallax differs considerably from C.
nymanii in that the root is up to 2.5 mm wide (vs.
to 5 mm in C. nymanii sensu stricto, the stamen
is up to 1.5 mm long (vs. 2.5 mm), and the ovules5

are ca. 25 per locule (vs. up to 50) (Kato andHambali, 2001; Kato, 2006a). Cladopus fallax is
also distinct from C. taiensis in the digitatebracts with lobes thick and somewhat rough on
the surface, while the bracts are lobed, thin andsmooth in C. taiensis (Kato, 2006a).
5. Cladopus pierrei (Lecomte) C. Cusset, Fl.
Cambodge, Laos, Viêt-nam 14: 73. 1973; Bull.
Mus. Natl. Hist. Nat., B, Adansonia 14(1): 25.
1992—Mniopsis pierrei Lecomte, Not. Syst. 1:
8. 1909. Type. Laos: Bassac, Champassak,
F.(A.)F.J. Harmand s.n. (as Pierre 5194) (P!).
Roots ribbon-like, ca. 1.5 mm wide; leaves atsinuses between root branches. Flowering shoots
at sinuses of root branching, solitary, erect, to 3
mm tall; bracts 8–10 in two files, digitate with
6–10 lobes, base membranous, lobes cylindrical,
hard, papillate with silica, 1–1.2 mm long;spathella enclosing young flower flattened, ellipsoidal, 2–2.5 mm long, membranous, rupturing
into several lobes at apex at anthesis, funnel-like;pedicellate; tepals on top of pedicel 2, 1 on eachside of stamen, linear, ca. 1 mm long; stamens 2
with common andropod; ovaries single, sessile,
2-locular, globose; stigmas 2, subulate, ca. 0.3
mm long, forked at base; ovules on whole septum
surface; capsules-stalks 2.5–4 mm long, capsuleschestnut-brown, globose, ca. 1.5 mm long, ca. 1
mm wide, smooth but with two stripes, dehiscingby 2 equal or subequal valves.
Specimen examined. S Vietnam: Massif duLang Biang, between Klou and Da Nhim, Tuyên
Doc, Chevalier 30945 p.p. (P).
Distribution. Laos (southern, central), Vietnam(southern).
Notes. Cusset (1973a, 1992) divided the genus
Cladopus by the number of stamens into two sections, Cladopus with one stamen and Griffithella
with two stamens on the common andropod, thelatter of which comprises C. pierrei and south Indian C. hookerianus (Tul.) C. Cusset, type of thesection. Phylogenetically, C. pierrei is so close to
C. doianus (Koidz.) Koriba (C. japonicus Imamura; Kato, 2008) as to be inseparable even at
the section level (S. Koi, unpubl. data). The

6

Masahiro Kato

genus Lecomtea Koidz. was proposed for Cladopus pierrei (Koidzumi, 1929), but it is not warranted. An unpublished result of S. Koi’s molecular phylogenetic analysis also suggests that C.
hookerianus belongs to the Polypleurum-Zeylanidium clade, sister to a clade comprising the
Cladopus clade and the Hydrobryum clade.
6. Hydrobryum japonicum Imamura, Bot.
Mag. Tokyo 42: 376. 1928; l.c. 43: 332. 1929;
Ohwi, Fl. Jap. 394. 1965; Shin, Wild Fl. Jap.
Herb. Pl. 2: 214. 1982; Cusset, Bull. Mus. Natl.
Hist. Nat., B, Adansonia 14(1): 46. 1992, p.p.
excl. H. floribundum (Koidz.) Koidz. et H.
puncticulatum Koidz.; Kato, Acta Phytotax.
Geobot. 55: 157. 2004—Hydroanzia japonica(Imamura) Koidz., Acta Phytotax. Geobot. 4: 28.
1935. Type. Japan: Ohnejime, Kagoshima,
Kyushu, Senokuchi s.n. (TI, not seen).
Hydrobryum griffithii auct. (non [Wall. ex
Griff.] Tul.); Cusset, Fl. Cambodge, Laos, ViêtNam 14: 68. 1973.
Root crustaceous, irregularly lobed (vegetativeplants not available). Flowering shoots appressed,with flowers solitary at tip; bracts ca. 4, in 2
ranks, uniform, ovate, abaxially convex; spathella
irregularly ruptured near apex at anthesis; ovarystalk short; tepals 2 on both sides of stamen, inserted near base of stalk, linear-lanceolate, 1.5–2mm long; stamens 2, branched above middle, ca.
2.5 mm long (when young), much longer thanovary; ovary 2-locular, ellipsoidal, 2–2.5 mm
long, septum fissured above sterile thick central
area; stigmas 2, equal, ca. 0.5 mm long, linear,
pointed or obtuse at tip, branched above base,often reflexed; ovules ca. 14 per locule, on marginal surface of septum; capsule short-stalked(up to 0.5 mm long), ellipsoidal, flattened, ribs
12.
Specimen examined. N Vietnam. Lao Kay,near Chapa, 1300 m alt., Pételot 3370 (P).
Distribution. Thailand (northern, northeastern;
central [Cusset, 1992]), Vietnam (northern),
China (Yunnan prov. [Kato and Kita, 2003]),
Japan (southern Kyushu).
Note. This species from northern Vietnam was

first regarded as H. griffithii (Cusset, 1973a), butlater identified to be H. japonicum (Cusset,
1992). This is verified here by the linear stigma(vs. cristate in H. griffithii) and molecular (matK)
phylogenetic data (M. Kato, unpubl. data).
7. Diplobryum minutale C. Cusset, Adansonia,
ser. 2, 12: 279, f, 1. 1972; Fl. Cambodge, Laos,Viêt-nam 14: 70, f. 11. 1973; Bull. Mus. Natl.
Hist. Nat., B, Adansonia 14: 49. 1992. Type.
Vietnam: Lang Bian, between Klou and Dauhin,
900–1200 m, southern, Chevalier 30946bis (P!).
Roots crustose, irregularly lobed, with rhizoids
in pads on ventral surface, coriaceous. Flowering
shoots dense on dorsal surface of root, appressed;
bracts 6–8 in 2 files, uniform but basal ones
smaller, ovate, hood-shaped, obtuse at apex,
papillate, 1–1.8 mm long; spathella enclosing
young flower, ellipsoidal, obtuse at apex, papillate except in center, 2–2.5 mm long, longitudinally or apically split at anthesis, persistent;
tepals not seen (in Cusset’s [1992] description: 2,
1 on each side of stamen, 0.5 mm long); stamens
fallen with single andropods (in Cusset’s [1992]
description: 2, branched); ovaries single, staked,
2-locular, ellipsoidal, flattened, protruding fromspathella; stigmas fallen (Cusset’s [1992] description: 2, capitate); ovules roughly 25 per
locule, borne on whole septum surface; capsules
stalked (stalks 2–3 mm long), ellipsoidal, flattened, 2–3 mm long, 1–1.2 mm wide, ca. 20ribbed, dehiscing by 2 equal valves; seeds ellipsoidal, longitudinally weakly ridged.
Specimen examined. S Vietnam: Lang Bian,
Chevalier 30946bis (P).
Distribution. Endemic to southern Vietnam.
Notes. Genus Diplobryum sensu Cusset(1972), which was treated in a broader sense by
Cusset (1992), is distinguished from Hydrobryum
only by the number of capsule ribs (see Key).
Since Lao D. vientianense, which appears close
to this species, is placed within Hydrobryum in amolecular phylogenetic tree (S. Koi and M. Kato,
unpubl. data), the two crustose-rooted species
may also be assignable to Hydrobryum. Diplobryum minutale is distinct from H. japonicum inPodostemaceae of Cambodia and Vietnam

the numbers of bracts and capsule-ribs (see Key)and ovule arrangement, and also perhaps the stigma, but similar to D. vientianense and its closely
related northeastern Thai H. loeicum in the crustose root, longitudinally split spathella, prominent ovary-stalk, and 18–20-ribbed capsule.
The specimen examined has only old bracts
and fruits on root fragments, so that new material
is needed to describe the species in more detail.
Cusset’s (1972, 1973) flower diagram should be
re-examined.
Acknowledgments
I thank M. Newman and P. Suksathan for providing specimens for this study and curators of
Herbaria C, K and P for allowing me to examine
specimens. I am indebted to L. Cecilio and M.
Newman for photo images of Cambodian Podostemaceae used in this paper. This study was
supported by a Grant-in-Aid for Scientific Study
from the Japan Society for the Promotion of Science.
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