Notes on Pothos
BOYCE & A.D. POULSEN*
Ten species of Pothos have so far been collected
in Brunei. These all belong to sect. AlloPothos sensu Engler
(1905), series Longevaginati (seven species) and series Goniuri
(two species). The juvenile stage, probably of a further species,
has also been gathered but cannot be named yet. So far no members
of sect. Pothos ('EuPothos' sensu Engler
1905) have been collected in Brunei. From herbarium material seen
in Leiden (L), Florence (FI) and Kew (K) it appears that sect. Pothos
is restricted to the more mountainous regions of Borneo and is thus
likely to be very local if it occurs in Brunei at all. Gatherings
of Pothos material in Brunei have mostly extended
the known distributions of species common elsewhere in Malaysia,
Indonesia and the Philippines, but some of the material represents
only the third or fourth collection of species endemic to Borneo.
Two collections made by one of us (ADP) belong to Pothos
insignis, a species first gathered by Beccari and previously
known from only three localities in Sarawak. The isotype of P.
insignis at Kew is sterile, but vegetatively matches the Brunei
gatherings. Comparison between the Brunei collections, the fertile
holotype in Florence and an illustration of the species in Beccari
(1883) does not reveal any significant differences. There are two
further collections at Kew (Ludong S.31842 & Mamit S.32655) which
are referable to this species. Both differ from the type and from
the Brunei gathering in the shape of the petioles on the sterile
mature stems. The petioles also have pronounced petiolar sheaths
and the laminae have a slightly different, less pronounced, abaxial
venation pattern. In other respects, especially in their inflorescences,
they match the type well and clearly represent the same taxon.Moderately
slender, slightly branched, adpressed to 'hammock'-forming trunk
climber to 3 m, main stem monopodial, apparently of indeterminate
length, sterile, never branching terminally unless damaged; side
branches sympodial, of determinate length, fertile, branching terminally
after flowering (plant displaying Model of Stone, Hall│ et al.,
Juvenile stem lengths unknown; mature sterile stem lengths straight
to slightly flexuous, 3-5 mm diam., apparently of indeterminate
length, naked, nodes distant, slightly prominent, c. 6-8 cm apart,
stem rooting copiously from nodes, roots 0.75-1 mm diam.; mature
post-fertile (see below) stem lengths straight, 5-7 mm diam., naked,
nodes ▒ compacted, c. 1.5 cm apart, producing few, slender, tough
roots, roots 0.5-2.5 mm diam.; mature fertile stem lengths quite
strongly flexuous, 6-25 cm long, 4-6 mm diam., apparently of determinate
length, completely and densely clothed by inflated, overlapping
cataphylls, nodes compacted, c. 1.5 cm apart, producing few slender
roots, roots c. 0.5 mm diam.
Juvenile leaves unknown; leaves on mature sterile stem: prophyll
unknown, cataphyll unknown, petiole slender, strongly channelled,
geniculate apically, 11-24 cm x 3-6.6 mm, geniculum prominent, 7-9
x 2 mm, extending beneath lamina, sheath initially conspicuous,
c. 2-4 mm wide, later much reduced and present as a minutely erose
margin along the entire petiole length and forming a smooth, flattened
oblique ochrea above the geniculum; lamina (7-)0.5-34 x (2.5)5-14
cm lanceolate-elliptic, strongly oblique, base minutely cordate,
apex attenuate with a 2-2.5 mm apiculum; leaves on mature fertile
stems: prophyll unknown, all other leaves reduced to cataphylls,
cataphylls 7-10 x 1.5-2 cm, oblong elliptic, robust, margins hyaline,
apex drawn into a lamina 3-9 x c. 1 mm, margins erose.
Peduncle 5 cm x 2-3 mm, greenish purple; subtending cataphyll
c. 2 cm x 6 mm; spathe 4.5-5.5 x 1.5-3.25 cm, ovate-elliptic, base
decurrent, apex acuminate, mid-green with a broad purple mark centrally
and some purple staining apically, spathe reflexing at anthesis;
spadix 3.5-5 cm x 4-6 mm overall; stipe 4-6 x 1.5-2 mm, decurrent
into spathe limb, purple; fertile portion 4.2 cm, cream.
Tepals 2 x 1 mm, oblong-cymbiform, apex cucullate, triangular,
outer whorl slightly hirsute, inner whorl glabrous, cream with purple
staining apically, stamens: filament 1 x 0.5 mm, strap-shaped, thecae
linear, 1 x 0.33 mm, dehiscing via longitudinal slits, cream, gynoecium
2 x 1 mm, 3-loculate, ovoid-ellipsoid, stylar region pointed, purple,
stigma punctate, very slightly two-lobed, purple.
Peduncle 6-8 cm x 2-3 mm diam., greenish purple; spathe persistent
into fruiting, becoming chartaceous; tepals much increased in size,
up to 7 x 2.5 mm, and apparently functioning as protection for developing
berries; filament remains abundant, chartaceous; berries flattened
basally, turbinate apically, 5-10 x 2-3.5 mm, stylar region strongly
pointed, young berries dark purple, tinged white, mature berries
white with purplish stylar region; seed c. 2 mm diam., ovoid, usually
only one developing per berry, greyish brown. (Fig. 1).
Brunei, Sarawak. BRUNEI. Temburong: Sungai Belalong at Kuala Belalong,
Batu Apoi Forest Reserve, ridge west of Kuala Belaong Field Studies
Centre slope, 115┴09'E, 4┴33'N, 22 June 1991, Poulsen 180 (AAU!
BRUN! K!); Sungai Belalong at Kuala Belalong, Batu Apoi Forest Reserve,
Kuala Belalong Field Studies Centre, Webber Booth's Plot, 115┴09'E,
4┴33'N, 23 June 1991, Poulsen 183 (AAU! BRUN! K!). SARAWAK. 1st
Division: Matang, Beccari 953 (holotype FI! isotype K!); Tiang Bukop,
32 mile Padawan road, 13 Jan. 1973, Mamit S32655 (L! K! SAR). 4th
Division, Bukit Kala, Long Melinau, Paku, Tutoh, Ludong, S31842
(SAR K! L! SYD).
Hemiepiphytic trunk or treelet climber at base of ridges or near
rivers in primary mixed dipterocarp forest on Setap shales or limestone.
70-100 m. Pothos insignis is apparently
allied to P. rumphii (Presl) Schott (1832) and P. borneensis Furt.
(1935) in having long petioles with a petiolar sheath extending
to the base of the geniculum, a relatively large, leathery spathe
and robust tepals. Pothos insignis is
distinguished from P. rumphii and P. borneensis by
the manner in which the inflorescences are presented. In P.
insignis new fertile stems arise from leafless, post fertile
stems (see below). The new fertile stems are clothed along their
entire length by inflated cataphylls each consisting of a greatly
enlarged petiolar sheath terminated by a much reduced leaf lamina.
From the apex of each fertile stem emerge the inflorescences, one
at a time, each new inflorescence emerging as the previous one begins
to fruit. It is unclear how many inflorescences a fertile stem produces
before it dies, but a study of the scarring of post fertile stems
suggests that it may be as many as twelve.
Our observations of Pothos in the field and
in herbaria show that there are four types of stem architecture
displayed by the plants in sect. AlloPothos. All members
of the section investigated in Brunei pass through a juvenile phase.
The seedling is a shade-orientated (skototrophic, see Strong & Ray
1975, Madison 1977), climber which grows along the forest floor
until a suitable climbing surface is encountered. The juvenile phases
of all the species investigated have ovate to lanceolate, almost
sessile, distichously arranged leaves. Once a climbing surface is
reached the plants often form a distinctive 'shingle' climber with
the leaves overlapping in the manner of roof tiles. Such 'shingle'
climbers are abundant on the lower parts of tree trunks. The 'shingle'
stage continues for approximately 2 metres when, abruptly, adult
leaves are produced with long petioles and lanceolate to elliptic
laminae. This transition marks the beginning of the second type
of stem architecture known as 'sterile mature'. It appears that
many Pothos species remain at this growth stage
for a considerable time, the sterile mature stems continuing growth
and often branching repeatedly from the lower parts, especially
in series Goniuri. It should be noted that while the 'shingle' stage
is always closely attached to the substrate by roots from the nodes,
the sterile mature stems are often scandent, forming 'hammocks'
in the canopy and only rooting at distant nodes. Eventually sterile
mature stems branch from the older, often leafless, lower parts,
giving rise to fertile mature stems. These fertile stems, although
initially produced from the mature sterile stem, later give rise,
themselves, to new fertile stems which are produced from post fertile
portions, usually the older mid-portions, the whole structure eventually
forming a much-branched system. Each plant may bear many such systems
(see Fig. 2). The most important observation about this differentiation
of stem function is that while the juvenile sterile and mature sterile
stems are apparently monopodial, the fertile mature stems are sympodial.
Although this growth habit does occur in other species of sect.
AlloPothos, it is difficult to observe because these species
have densely aggregated flowering stems. Pothos
insignis has fertile mature stems of sufficient size to make
the stem architecture readily observable.
Beccari, O. (ed.), Malesia 1:261-304, t.16-28. Genova.
Engler, A. (1879). Araceae specialmente Bornensi e Papuane raccolte
O. Beccari. Bull. Soc. Tosc. Ortic. 4:265-271, 295-302 (1879).
Beitr╣ge zur Kenntniss der Araceae. I. 1. Neue Araceen vom indischen
Archipel. Bot. Jahrb. Syst. 1:179-190. -------- (1883) ('1882').
Araceae. In Beccari, O. (ed.), Malesia 1:261-304, t.16-28. Genoa.
Pothos. In Engler, A. (ed.), Das Pflanzenreich 21(IV.23B):21-44
(1905). Leipzig. Furtado, C.X. (1935).
Araceae Malesicae. Gard. Bull. Straits Settlem. 8:145-158. Hall│,
F., & Oldemann, R.A.A. & Tomlinson, P.B. (1978).
Tropical Trees and Forests; An Architectural Analysis. Springer-Verlag.
Berlin. Madison, M. (1977).
A revision of Monstera (Araceae). Contrib. Gray. Herb. 207: 3-100.
Schott, H.W. (1832).
Pothos. In Schott, H.W. & Endlicher, S.F.L., Meletemata
Botanica 17. Vienna. Strong, D.R. & Ray, T.S. (1975).
* Address. Botanisk Intitut,
University of Aarhus, 68 Nordlandsvej, DK-8240, Risskov, Denmark.