and validated and architectural notes on Pothos subgenus
Peter C. Boyce *
& Nguyen Van Dzu**
Summary. Pothos grandis, a name proposed but not validly
published by Buchet (1942), is validated and an emended species
description given. Discussion of the growth architecture of western
Indomalesian Pothos subgenus Pothos
Pothos L. is genus of approximately 70 species of
subtropical and tropical forest climbers centred in Malesia (Hay
et al. in press) belonging to Araceae subfamily Pothoideae
(sensu Bogner & Nicolson 1991). Shared leaf, flower and fruit
characters suggest that Pothos is most closely related
to Pedicellarum M. Hotta (1976) and Pothoidium Schott
(1857a, b). Indeed, Pothos and Pedicellarum
may be congeneric. Until a full revision of Pothos
is completed we are, in this and other papers, adopting a modified,
informal version of Englers infrageneric classification of
Pothos (Engler 1905). While we follow Englers
sections (as subgenera) we reject his serial concepts, instead recognizing
informal species groups. Pothos grandis belongs to
the P. seemanii Schott group of subgenus Pothos.
HISTORY OF Pothos grandis
Buchet (1942) writing in Gagnepains Floré Général
de lIndo-Chine proposed the name Pothos grandis
for specimens collected at three sites in Tonkin (modern North Vietnam)
and a single specimen from Annam (central Vietnam). Unfortunately,
Buchet omitted the Latin diagnoses for his new species and thus
according to the Art. 36.1 of the International Code of Botanical
NCNST, Nghia Do, Tu Liem, Hanoi, Vietnam.
NOMENCLATURE (Greuter et al. 1994) the name Pothos grandis
is not validly published. Since Buchets time the species has
been seldom re-collected. All collections seen are rather poor and
none display the full range of shoot form to be expected for a species
of Pothos subgenus Pothos. Recent field
work in North Vietnam undertaken jointly by staff of the Herbarium,
Royal Botanic Gardens, Kew, (K), the Department of Botany of the
Institute of Ecology and Biological Resources, Hanoi (HN) and the
Department of Botany, University of Hanoi, (HNU) resulted in the
re-collection of P. grandis at
one of the type localities. A plant was found in flower and sufficient
material collected to enable a complete description to be prepared.
Pothos grandis S. Buchet ex P.C. Boyce & D.V.
Nguyen sp. nov., P. grandis in
aspectu P. seemanni valde proxima, et ab ea foliis majoribus,
pedunculo petiolum aequanti sed numquam eum superanti (pedunculus
in P. seemanni petiolo duplo longior), spatha aliquantum
grandi atque spadice dissimiliter formato grandiore in stipite longiore
suffulto distinguibilis. Typus: Colani s.n. (holotypus P!; isotypi
K (photo!) SGN!).
grandis S. Buchet apud Gagnepain in Lecomte, Fl. Gén.
lIndo-Chine 6: 1088 (1942), nom. invalid. sine descr. Latin.
Moderately robust somewhat woody root-climber and hammock-forming
hemi-epiphyte to 3 m.
system differentiated into several phases (seedling phase not
known). Seedling/mature sterile transition shoots monopodial, apparently
of indeterminate length, climbing, appressed to substrate and rooting
moderately from most nodes, probably not branching unless damaged
apically (reiteration not observed), stem to 4 mm diam., sharply
four-angled, minutely winged along the angles, leaves rather scattered.
Mature sterile shoots monopodial, orthotropic, of indeterminate
length, climbing, appressed to substrate and rooting prolifically
from each node, not branching unless damaged apically, reiteration
occurring from a node some distance back from the damaged apex,
stems occasionally transforming terminally into a foraging flagellum
(see below), stem to 8 mm diam., weakly four-angled or slightly
compressed-terete, at first somewhat sparsely clothed with leaves,
later naked, naked portions with prominent, slightly stepped nodes
to 5 cm distant, stem deep green, becoming black-brown with age,
drying dark green to almost black. Mature fertile shoot sympodial,
with growth modules of varying determinate lengths, free, arising
from the mature sterile stem as side branches, often branching to
three orders, plagiotropic, not rooting from nodes, stem to 4 mm
diam., mostly moderately clothed with leaves, occasionally older
portions naked at the base to approximately half their length, naked
portions with prominent, stepped nodes to 3 cm distant. Flowering
shoots much abbreviated, arising from the leaf axils of mature fertile
shoots, subtended by a minute prophyll and up to seven 4 - 30 mm,
sequentially longer, cataphylls, terminated by 1 - 3 sequentially-produced
inflorescences. Foraging shoot a flagellum to 2 mm diam. with a
few leaf-like cataphylls and reduced foliage-leaves at first but
soon becoming naked with slightly prominent nodes up to 10 cm distant,
arising mostly by terminal extension of the mature sterile shoot,
(more rarely from a similar extension of a fertile shoot), monopodial,
of indeterminate length, foraging for several metres until a suitable
climbing surface is encountered, not branching unless damaged apically
and then branching from the nearest healthy node, occasionally rooting
sparsely from the nodes while foraging, always rooting prolifically
on resumption of climbing habit.
Petiole obovate-oblong, broadly winged, base decurrent, apex truncate
to rounded or slightly auriculate, 2 - 5 x 1 - 2 cm, petiole with
2 - 3 secondary veins and numerous veinlets per side, all veins
prominent, especially in dried material; lamina ovate, base rounded,
apex acuminate-mucronate, 14 - 23 x 5.5 - 10 cm, lamina with 2 secondary
veins per side, these arising from the base and either reaching
the leaf tip or merging into a prominent submarginal collecting
vein, all additional veins arising obliquely from the mid-vein,
remaining parallel with numerous branches arising from them, leaves
deep green adaxially, paler and slightly yellowish abaxially when
fresh, drying dull olive green.
pedunculate, peduncle robust, 4 - 7 cm x 2 - 3 mm, tapering, slightly
thinner towards the apex, deep purple; spathe ovate to ovate-lanceolate,
base slightly cordate to decurrent, apex acute with a somewhat stout
mucro, 2.5 - 5.2 x 2 - 3 cm, margins prominently inrolled, deep
purple, sometimes slightly greenish abaxially when fresh, drying
almost black; spadix stipitate, deep purple, stipe terete, 1.2 -
1.5 cm x c. 2 mm; fertile portion of spadix ovoid to clavate, 1.2
- 3 cm x 9 - 13 mm, yellow-green to off-white.
tepals 6, 4 x 1.3 mm, oblong-cymbiform, yellow-green to dirty white,
apex cucullate, triangular, truncate, stamens 6, 1 - 4 x c. 0.5
mm, filaments strap-shaped, thecae elongate-globose, 1 x 0.25 mm,
dehiscing via longitudinal slits, cream, gynoecium 5 x 1.75 mm,
3-locular, compressed angular-ellipsoid, yellow-green to dirty white,
stylar region truncate, stigma prominent, punctate, purple.
a head of 4 - 10 berries, these obclavate, 1 - 1.75 x 1 - 1.4 cm,
green ripening through yellow to deep orange-red. Seeds 1 - 3, ellipsoid
to compressed-globose, c. 5 - 8 mm diam. (Fig. 1).
VIETNAM. Hanoi: near Kien Khe, Bon 2152 (P!). Ha Tay: My Duc, Chua
Huong, 28 May 1977, Nguyen Thi Nhan HN 111 (HN!); My Duc, Chua Huong,
1 July 1993, Ha Thi Dung HN 217 (HN!); Hoa Binh: Cho Bo, Balansa
2051 (P!); Kim Boi, 30 Aug. 1994, Boyce & Nguyen Van Dzu 857
(HN!, K!); Kim Boi, June 1926, Colani 3002 (holotype P!; isotypes
K (photo), P!, SGN!); Kon Tum, Dak Glay, 29 Mar. 1977, Tran Ding
Ly HN 389 (HN!); Lang Son: Pac Mo, 23 Mar. 1961, Soviet-Vietnam
Expedition 1137 (LE!); Nghe An: from Phu Qui to Kebon, Poilane 16565
(P!, SGN!); Quy Chau, Trinh Xuan Mai HN 737 (HN!). Ninh Binh: Cuc
Phuong Nat. Park, 6 Jan. 1963, Nguyen Quo Chung HN 2130 (HN!); Cuc
Phuong Nat. Park, 17 Feb. 1971, Hach 26 CP (HN!); Cuc Phuong Nat.
Park, 9 July 1971, Tran Hop HN 643 (HN!).
or hemiepiphyte on trees and cliffs of Karst limestone formations
in fragments of very degraded lowland to lower hill evergreen forest.
75 - 250 m.
Co´m lênh la´buo´i (Viet.).
NOTE: The collection from Pac Mo, Lang Son prov., (Soviet-Vietnam
Expedition 1137) was made close to the border with China. Pothos
grandis is to be expected in that country.
Pothos grandis is most similar in appearance to P.
seemanni Schott (SW China, Laos, Thailand, N Vietnam) from
which it may be separated by the larger leaves, the peduncle equalling
the petiole (peduncle twice as long as the petiole in P. seemanni),
larger, differently shaped spathe (ovate to ovate-lanceolate in
P. grandis, ovoid in P.
seemanni), the differently shaped, larger fertile portion
of spadix (ovoid to clavate in P. grandis,
ovoid in P. seemanni) and longer stipe.
Pothos grandis displays the typical growth
architecture and inflorescence presentation of most species of subgenus
Pothos and can be used as a point of reference for
a discussion of the majority of species of this subgenus in western
Indomalesia. Species of the Pothos scandens
L. group (subgenus Pothos), while conforming to the
pattern of growth architecture described above, behave somewhat
differently in the manner of inflorescence presentation. Discussion
of this will be the subject of a future paper. Data concerning stem
architecture in P. insignis
Engl. (Borneo; subgenus AlloPothos) were discussed
by Boyce and Poulsen (1994, as sect. AlloPothos).
Most species of subgenus Pothos in western Indomalesia
appear to have the five-phase growth architecture described above
for P. grandis (Fig. 2). A possible
sixth phase, a modified version of the sterile mature growth, has
been observed in three species of Pothos and is discussed
below. The seedling stage is not known for all species in the subgenus
but for those known, P.
scandens L., P.
repens (Lour.) Druce (syn. P. loureirii Hooker
& Arn.), P. longipes Schott (see Hay, in press), P.
cathcartii Schott and P. yunnanensis Engl.,
this phase consists of a skototropic (see Strong & Ray 1975)
flagellar growth which, on reaching a suitable climbing surface,
alters into a shingle climber with closely arranged or overlapping
leaves of much the same shape as those found in the adult growth
stages. The shingle stage appears to be monopodial but also produces
simple branching systems by reiteration (sensu Hallé, Oldemann
and Tomlinson 1978). The seedling phase continues until one or more
as yet unknown factors (e.g. light and moisture levels, available
nutrients) trigger the production of the sterile mature growth stage.
This stage is a densely leafy, later naked, appressed monopodial
climber rooting copiously from the nodes. The sterile mature growth
phase does not branch terminally unless damaged when it then reiterates
from a node usually some distance back from the damaged apex. However,
this phase does occasionally transform terminally into a foraging
flagellum as discussed above for P. grandis.
At some point the sterile mature stage begins to produce fertile
mature shoots from lateral buds. These fertile shoots are sympodial,
of varying determinate lengths and often branch to several orders
from lateral buds. They are generally moderately leafy, later becoming
naked below. Fertile mature shoots eventually produce much-abbreviated
lateral shoots consisting of a minute prophyll and one to several
cataphylls and terminating in one to several sequentially-produced
inflorescences. Occasionally fertile mature shoots transform terminally
into a foraging flagellum.
scandens (observed in cultivation at Kew), P.
macrocephalus Scort. ex Hook.f. (observed in cultivation
at Leiden), P. repens
and P. cathcartii (both observed in habitat), the
sterile mature growth phase occasionally produces exceptionally
robust lateral branches in which the leaves, while of conventional
shape and size, are tightly imbricated and not spreading. The factors
triggering this modified growth phase are not known. It might represent
another form of foraging shoot or, possibly, a means for the plant
to reiterate from lower buds when the top growth carried begins
to exceed the capability of the functional root mass. It is noteworthy
that this type of sterile mature shoot reiteration has only been
observed on plants of great size, most notably an immense specimen
of P. repens covering
almost an entire Karst limestone formation at Man Duc, Hoa Binn
We would like to thank Dr David Simpson and Dr Alistair Hay for
their comments and suggestions and Mr Alan R. Radcliffe-Smith for
the Latin translation of the diagnoses.
Bogner, J. & Nicolson, D.H. (1991). A revised classification
of Araceae with dichotomous
keys. Willdenowia 21: 35 - 50.
Boyce, P.C. & Poulsen, A.D. (1994). Notes on Pothos
insignis (Araceae: Pothoideae). Kew
Bulletin. 49(3): 523 - 528.
Buchet, S. (1942). Pothos grandis apud Gagnepain in
Lecomte, Flore Général de l'Indo-Chine
6, 1088. Paris.
Engler, A. (1905). Pothos. In Engler, A. (ed.), Das
Pflanzenreich 21(IV.23B): 21 - 44 (1905).
Greuter, W. et al. (eds) (1994). International Code of Botanical
Nomenclature (Tokyo Code).
Hallé, F., & Oldemann, R.A.A. & Tomlinson, P.B. (1978).
Tropical Trees and Forests; An
Architectural Analysis. Springer-Verlag. Berlin.
Hay, A. (in press). The genus Pothos L. (Araceae:
Pothoeae) in New Guinea, Solomon Islands
and Australia. Submitted to Blumea.
Boyce, P.C., Hetterscheid, W.L.A., Jacobsen, N., Murata, J. &
Bogner, J. (in press). A
checklist of the Araceae of Malesia, Australia and the tropical
western Pacific region. Blumea Soppl. 8.
Hotta, M. (1976). Notes on Bornean Plants III. Pedicellarum and
Heteroaridarum, two new
genera of the aroids. Acta Phytotax. Geobot. 27: 61- 65.
Schott, H.W. (1857a). Aroideae Fasc. 6. Gerold et Fil. Vienna.
(1857b). Aroideae Skizzirt. Oesterr. Bot. Wochenbl. 7: 69 - 70.
Strong, D.R. & Ray, T.S. (1975). Host tree location behavior
of a tropical vine (Monstera
gigantea) by skototropism. Science 190: 804-806.
Herbarium, Royal Botanic Gardens Kew, Richmond, Surrey, TW9 3AB,
** Herbarium, Department of Botany, Institute of
Ecology & Biological Resources,