IAS on Facebook
IAS on Instagram
Epipremnum is one of four Asian genera in Monstereae
(sensu Mayo, Bogner & Boyce, 1997), the others are Scindapsus,
Rhaphidophora and Amydrium. In Malesia these genera
are mostly root-climbing lianes (see Schimper, 1903: 193), exceptions
include, e.g. Scindapsus rupestris Ridl. (Peninsular
Malaysia, Borneo; creeping rheophyte), Amydrium humile
Schott (Peninsular Malaysia, Thailand, Sumatra; creeping to rarely
climbing forest floor herb), Rhaphidophora beccarii Engl.
(Peninsular Malaysia, Thailand, Sumatra, Borneo; creeping rheophyte)]
occurring in a wide range of habitats [lowland dipterocarp forest
(e.g. Rhaphidophora crassifolia Hook.f., Pasoh F.R., Negeri
Sembilan, Malaysia) to montane kerangas (e.g. Scindapsus scortechinii
Hook.f., Genting Highlands, Selangor, Malaysia)]. All genera except
Amydrium have abundant trichosclereids in all tissues (sparse
in Amydrium). These are observable by tearing a mature leaf
lamina and looking for hairs protruding from the damaged
edges. All genera have spadices bearing bisexual naked flowers. Often
the lower and uppermost flowers in a spadix are sterile and different
in appearance. Lower sterile flowers are usually larger and free while
those at the spadix tip are often smaller and partially fused to adjacent
sterile flowers. In neotropical Monstera Adans. the basal sterile
flowers usually produce a nectar droplet and appear to act as pollinator
attractants (Madison, 1977). They perhaps function similarly in Asian
genera. In most species observed to date the spathe gapes on opening
and is swiftly shed at male anthesis (exceptions with partially persistent
spathes include Scindapsus rupestris). In all but Amydrium
medium (Zoll. & Moritzi) Nicolson and A. humile Schott
the mature infructescence surface is comprised of tough thickened
stylar tissue. When the infructescence is ripe the styles adhere to
one-another and fall as irregular plates to expose the ovary cavity
with the seed embedded in copious, variously coloured pulp.
Confusion can occur between Epipremnum and the other Malesian
monsteroid genera. If fruits are mature, seed characters are useful
in separating Epipremnum and Rhaphidophora. Epipremnum
has fruits with few large, strongly curved, seeds with a bony, smooth
to ornamented testa. The fruits of Rhaphidophora each contain
many small ellipsoid seeds with a brittle, smooth testa. Alternatively,
immature fruits can be dissected and the number of ovules counted
(few in Epipremnum, almost always many in Rhaphidophora).
Certain Scindapsus [notably S. latifolius M. Hotta (Borneo),
S. splendidus Alderw. and S. roseus Alderw. (both Sumatra)] are very
similar in appearance to the entire-leaved Epipremnum species.
The only way to differentiate these Scindapsus and Epipremnum
species, aside from field experience, is to observe inflorescences
or, better, semi-mature infructescences. Scindapsus has fruits
with a solitary curved seed. However, certain Epipremnum species
(e.g. E. ceramense and E.
falcifolium) seem to habitually abort all but one ovule and
produce fruits with a solitary seed. Older texts (e.g. Engler &
Krause, 1908) state that Scindapsus seed is exalbuminous but
recent studies of Araceae seed by Seubert (1993) have demonstrated
that Scindapsus seeds do contain small quantities of endosperm.
Nevertheless the embryo is still relatively larger in Scindapsus.
The sparse trichosclereids of all Amydrium species facilitates
field identification of even sterile material to genus (see note above).
Where confusion between individual species can occur [e.g. between
Amydrium zippelianum (Schott) Nicolson, A. magnificum
(Engl.) Nicolson and E. pinnatum]
a note is included with the relevant species.
Species of Anadendrum Schott (tribe Anadendreae)
are often collected as Rhaphidophora, Scindapsus
or Epipremnum. Anadendrum, together
with most Pothos L. and Pedicellarum
M. Hotta (both subfamily Pothoideae), are the only simple-leaved
Asiatic aroid climbers with reticulate venation (Amydrium humile,
also with reticulate venation, can occasionally be observed as a low
climber, but then with a solitary inflorescence). Additionally, Anadendrum
lacks trichosclereids and can be distinguished from all Monstereae
using a leaf tear. Using floral characters Anadendrum (each
flower with a membranous perigon of fused tepals) is a singular genus
and should not be confused with any other asiatic climbing Araceae.
Confusion can occur between Anadendrum and genera of Pothoideae
(i.e. Pothos, Pothoidium
Schott and Pedicellarum) that also lack trichosclereids. However,
Pothos (except subgen. Pothos) and Pedicellarum
are instantly recognizable by the intramarginal veins crossing the
primary venation (for illustration see Hay, 1995). Anadendrum
flowers on clinging climbing shoots whereas almost all Pothos
flower on free lateral shoots. In fruit both have red, somewhat juicy
berries. However, those of Anadendrum are apically truncate
with a prominent linear stigma wheras Pothos has ellipsoid to globose
berries with a tiny, punctiform to slightly elongated stigma. The
critical characters for differentiating between the genera of Anadendreae
and Monstereae in west and central Malesia are presented below
as a dichotomous key.
Confusion is also possible at species level. Epipremnum pinnatum
is vegetatively most similar to Rhaphidophora korthalsii Schott
but easily-observed distinguishing characters are present. Mature
leaves of R. korthalsii are invariably pinnatisect (variously
pinnatifid, pinnatipartite or pinnatisect in E.
pinnatum) with individual pinnae, even the narrowest, having
more than one primary lateral vein (one per pinna in E. pinnatum).
The internodes of R. korthalsii lack the prominent irregular
longitudinal whitish crests and older stems lack the distinctive matt
to sub-lustrous pale brown papery epidermis typical of E. pinnatum.
The feeder roots of R. korthalsii are scaly whereas
they are lenticellate-corky in E. pinnatum. The pre-adult stage
of R. korthalsii is a shingle climber with
oblong-elliptic to ovate, slightly falcate, upwards pointing leaves
overlapping in the manner of roof tiles. Juvenile plants of E.
pinnatum are sprawling to climbing with long-petioled conventional
leaves. Fertile material of R. korthalsii and E.
pinnatum is readily separated by the shape of the style apex [round
to oval (R. korthalsii) versus angled (E. pinnatum)]
and the shape of the stigma and its orientation to the spadix [punctiform
and circumferential (R. korthalsii) versus linear and longitudinal
Epipremnum pinnatum and Rhaphidophora tetrasperma Hook.f.,
another pinnatifid and perforate-laminaed species can be confused.
Juvenile R. tetrasperma is a shingle-plant similar in appearance to
R. korthalsii. Flowering-size plants have smooth stems and
unequal ovate-elliptic coriaceous laminae (longitudinally crested
stems and more-or-less equal, ovate to oblong-elliptic and sub-membranaceous
laminae in E. pinnatum) and a more scandent habit, with leaves scattered
along sinuous stems. Rhaphidophora tetrasperma is a rather
rare species restricted to a few sites in Peninsular Malaysia (Kelantan,
Perak) and southern Peninsular Thailand (Narathiwat).
Some terms employed in the descriptions to follow may need clarification.
Monopodial stems Sterile stems, often of great length, that are monopodial.
Such stems are usually only clinging and orthotropic (or nearly so).
Physiognomically monopodial stems Fertile stems, of variable length,
with the appearance of being monopodial but that are actually sympodial
with growth terminating by a, sometimes aborted, inflorescence. Such
stems may be clinging and orthotropous (or nearly so) or free and
plagiotropic to pendent.
Clasping roots Short specialized roots that anchor a climber, hemiepiphyte
or epiphyte to its substrate, generally a tree or rock. Feeding roots
Specialized roots arising from aerial stems which, extending down
to the soil, transport nutrients to the plant. Shingle climber A type
of juvenile morphology, found in climbers, in which the petiole is
very short and the leaf blade relatively broad and more-or-less overlapping
with its neighbours to resemble the tiles (or shingles) of a roof;
such plants are found climbing up larger tree trunks; e.g. Rhaphidophora
Compound primary lateral veins Vein type found in dried specimens
in which a primary lateral vein is comprised of few to several vascular
bundles (vs one vascular bundle in simple lateral veins). In fresh
material such features are often obscured by the turgidity of the
Interprimary veins A vein approximately parallel to and situated between
the primary lateral veins.
Perigon The floral envelope of a flower in which there is no differentiation
of calyx from corolla, it may be a single structure (connate tepals)
or composed of individual, similar tepals.
Perigoniate Of a flower which possesses a perigone.
Circumferential orientation (of stigmas) Linear stigmas set parallel
to the circumference of the
Longitudinal orientation (of stigmas) Linear stigmas set parallel
to the long axis of the spadix.
Trichosclereids Literally a hair-like sclereid; fibre cells (cells
with thick, lignified walls) which are very slender and elongated
so as to be visible to the naked eye as hair-like structures. On tearing
the leaf blade they can be seen protruding from the torn edge.