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Fig. 1 (A,B) Hygroryza aristata (Retz.) Nees ex Wight & Arn.: (A) habit; (B) inflorescence, (photos: Haruthai
Hemadhulin). (C,D) Leersia hexandra Sw.: (C) inflorescence; (D) habit, (photos: Woranart Thammarong). (E,F) Oryza
meyeriana
(Zoll. & Moritzi) Baill. var. meyeriana: (E) inflorescence; (F) habit, (photos: Phanom Sutthisaksopon).
Klaeng, 6 May 2009, P. Wessumritt & M. Norsaengsri
203
(QBG); Chanthaburi, Makam, 14 Jun. 1963,
K. Larsen 10087
(BKF, C), 10087a (K); Trat, Koh
Chang, 22 Feb. 1985, T. Smitinand s.n. (BKF);
PENINSULAR: Phatthalung, Tale Noi, 1 Apr. 2012,
Sumanon & Traiperm 2
(BKF); Songkhla, 8 Apr.
1928, Kerr 15119 (BK, BM, K), 28 Dec. 1978, Hamil-
ton & Congdon 157
(BKF).
Distribution.— This species also occurs in India,
Myanmar, China, Malaysia and Indonesia.
Habitat and Ecology.— Forming large floating
mats in small ponds, pools and canals, from sea level
to 50 m elevation. Flowering throughout the year.
Vernacular name.— Ya-phong-lom.
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ScienceAsia
41 (2015)
Fig. 2 Hygroryza aristata (Retz.) Nees ex Wight & Arn.:
(a) habit; (b) lemma; (c) palea; (d) lodicules; (e) pistil;
(f) anthers. Drawn by M. Norsaengsri.
Uses.— Widely cultivated by local people for its
grain, which is used as fodder for livestock during
cold weather
4
,
14
. In Thailand it is also cultivated as
an ornamental aquatic plant.
Conservation status.— Eleven herbarium collec-
tions of this species in Thailand were examined, and
it was observed during field work at one additional
locality. Based on these records, H. aristata was
found to have an EOO of 255 912 km
2
and an AOO
of 44 km
2
. Although the species has a scattered
distribution in Thailand, its subpopulations are not
severely fragmented; it is very widespread through-
out the region. Subpopulations can grow rapidly
via vegetative propagation and typically comprise
numerous shoots.
It is not known whether any
single site constitutes only a single clone or multiple,
genetically distinct individuals, making it difficult
to estimate the true population size in Thailand.
The origin of cultivated plants in Thailand and their
potential for introgression with native genotypes is
unknown. Some known locations for this species
are being developed as tourist attractions, but at
present there are no known specific threats to the
species in Thailand.
The degree of connectivity
with subpopulations in neighbouring countries is
expected to be high. Accordingly, it is regarded as
least concern (LC) in Thailand.
Notes.— Anders Jåhan Retzius’s original de-
scription of this taxon, published in his Observa-
tiones Botanicae in 1789, was based on Koenig’s
collections from India. Koenig’s holotype should
be held at C, but despite a thorough search, we
were unable to locate any Koenig specimens for
this taxon at that herbarium. Recognizing the same
problem, Turner
15
earlier designated a collection
at LD without locality, collector, or number as the
lectotype. However, duplicates of Koenig’s original
material were sent out to several herbaria; we found
one sheet at BM (barcode number BM000959315)
that is better preserved than Turner’s lectotype, and
which bears an original hand-written note confirm-
ing its origin as India. We have been unable to
confirm whether this was written by Koenig himself,
but we feel this specimen would have made a better
choice for lectotypification.
Leersia
Sw., Prodr. 21. 1788, nom cons.; Bor, Grasses
Burma, Ceylon, India & Pakistan 599. 1960; Fl.
China 22: 184. 2006. Type species: L. oryzoides
(L.) Sw., Prodr. 21. 1788.— Homalocenchrus Mieg
in Acta Helv. Phys. Math. 4: 307. 1760, nom.
rejec.
Type species: H. oryzoides (L.) Pollich in
Hist. Pl. Palat. 1: 52. 1776.—
Ehrhartia F.H. Wigg.,
Prim. Fl. Holsat. 63. 1780, nom illeg. superfl.—
Asprella
Schreb., Gen. Pl. ed. 8: 45. 1789, nom
illeg. superfl.— Laertia Gromov Trudy Obsc. Nauk.
Kharkow Univ. 1: 141. 1817, nom illeg. superfl.
Annual or perennial herbs. Culms slender, erect
or decumbent, rooting at nodes. Leaf sheaths tight,
not inflated, smooth, or scabrid; leaf blades linear-
acute. Inflorescence a panicle or sometimes race-
mose and enclosed within the sheath. Spikelets 1-
floret, bisexual, flattened. Glumes absent. Lemma
awned or awnless. Sterile lemmas absent. Palea
folded, nerved. Caryopsis not seen.
The genus of 18 species in tropical and warm
temperate regions
13
, two species occur in Thailand.
See
Table 2
.
1.
Leersia hexandra
Sw., Prodr. 21. 1788; Hook.
F. in Trimen, Handb. Fl. Ceylon 5: 184. 1900; Bor,
Table 2 Key to species of Leersia in Thailand.
1. Lemma awnless
1. L. hexandra
1. Lemma awned
2. L. stipitata
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