2 species recorded from New Guinea and Pacific Islands. Click on a name to go to its species page
Description (Barlow 1993)
Amylotheca Tieghem, Bull. Soc. Bot France 41 (1895) 261. - Type: A. dictyophleba (p. Mueller) Tieghem.
For descriptions and synonymy see Barlow, Austral. J. Bot. 22 (1974) 545; Flora of Australia 22 (1984) 73. Danser (1931) included Decaisnina in Amylotheca, which was therefore more broadly circumscribed than in this treatment. The descriptions referred to above are amended as follows: triads with central flowers sessile or pedicellate.
A genus of 4 species distributed from Malaya and Thailand eastwards and southwards to Sumatra, Borneo, New Guinea, Australia, New Caledonia, and the New Hebrides. Except for the localized A. subumbellata the species are apparently allopatric, so there is no significant centre of species richness for the genus (but see note under A. duthieana).
The species are found principally in rain forests, but may occur in open tropical woodlands. They may be common in lowland forests, but extend to montane forests at 2850 m in New Guinea. Attachment to the host is exclusively through secondary haustoria on extensive epicortical runners. Leaf architecture is not very variable, ranging from a common simple bifacial pattern to thick or thin isofacial forms, always decussate and with pennate venation. There is some variation in inflorescence and flower structure and, together with vegetative characters, this forms the basis for species distinction. Host specificity is generally low.
Diagnostic features
The infrafamilial classification of
Amylotheca and the generic group to which it belongs are
outlined above. For identification at the generic level the readily
observable morphological characters are derived from inflorescence
and flower structure.
The basic inflorescence unit (uniflorescence) in Amylotheca is a simple dichasium (triad) with a simple bract subtending each flower. The triads are aggregated into conflorescences, and the plesiomorphic state for the genus is an axillary raceme of uniformly spaced opposite pairs of triads. Simpler inflorescences are derived by reduction, and occur primarily as infraspecific rather than interspecific variations. The inflorescence is often subumbellate, and the ttiads may be reduced to single flowers so that the inflorescence may appear to be a simple raceme or even a 2-flowered simple umbel.
The flowers of Amylotheca are hermaphrodite, 6-merous, regular, and gamopetalous to the middle or higher, with the corolla tube often inflated at anthesis. The epipetalous stamens have basifixed immobile introrse anthers with simple filaments, the free parts of which are about as long as the anthers. The style is usually articulate above the base, leaving a distinct nipple on the fruit.
Generic relationships
Amylotheca is apparently closely related
to the larger genus Decaisnina, which is probably the least
specialized in the group. The major difference is in the corolla,
which is essentially choripetalous in Decaisnina, although
usually with the petals coherent at the base into a short tube,
and distinctly gamopetalous to the middle or higher in Amylotheca.
The anthers in Amylotheca are usually rounded or truncate
at the apex, whilst those of Decaisnina are commonly attenuate
and acute. Amylotheca is probably closest to Philippine
species such as D. viridis and D. crassilimba, in
which the inflorescence is not secund. Danser (1929; 1931; 1933a;
1935; 1936) consistently treated Amylotheca and Decaisnina
as congeneric, citing these Philippine species as a link which
obviated generic distinction. The lack of other apomorphic characters
in Amylotheca confirms the close relationship, but the
consistency of the gamopetalous corolla suggests that Amylotheca
is a monophyletic group which diverged early with a different
pollination syndrome.
Biogeographic history
For a general outline of the history
of the decaisninoid genera, see note under Decaisnina. Like
Decaisnina, Amylotheca occurs widely on both sides of Charles's
Line, although three of the four species are on the Australo/Papuasian
side. The genus was presumably represented in the intrusive Malesian
stocks which penetrated New Guinea and northern Australia, and
underwent some differentiation and speciation in the process.
Being basically a lowland genus, it has reached New Caledonia
and nearby islands, probably from New Guinea at times of lowered
sea level. The taxonomic difficulties in the genus derive entirely
from the resultant disjunctions in species areas.
1a. Leaves more or less glaucous; lamina truncate
or shortly cuneate at the base into a sharply defined dark coloured
petiole more than 10 mm long; style articulate 0-0.5 mm above
the base (Thailand, Malaya, Singapore, Sumatra, Borneo) 3.
A. duthieana
1b. Leaves not glaucous; lamina attenuate at the base into
an obscure winged petiole less than 10 mm long; style articulate
2-3 mm above the base. 2
2a. Leaves linear to narrowly lanceolate, less than 2 cm wide,
dull on both sides; corolla up to 34 mm long (Australia) . 4.
A. subumbellata
2b. Leaves lanceolate to broadly elliptic, more than 2 cm
wide, weakly to strongly bifacial and shiny above and dull below;
corolla mostly more than 34 rom long. 3
3a. Leaves mostly acuminate and acute at the apex, 12-20 cm long
(New Guinea) 1. A. acuminatifolia
3b. Leaves mostly rounded, rarely acute at the apex, 5-14
cm long (New Guinea, Australia, New Caledonia, New Hebrides).
2. A. dictyophleba
Description (Barlow 1974)
Amylotheca Tiegh. Bull. Soc. bot. Fr. 41: 261 (1894); Barlow, Aust. J. Bot. 14: 438 (1966); Loranthus sect. Amylotheca (Tiegh.) Blakely, Proc. Linn. Soc. N.S.W. 50: 11(1925). Type Species--A. dictyophleba (F. Muell.) Tiegh.
Aciella Tiegh. Bull. Soc. hot. Fr. 41: 435 (1894); Elytranthe sect. Aciella (Tiegh.) Engl . Pfl. Fam.Nachtr. 126 (1897); Amylotheca sect. Aciella (Tiegh.) Engl. & Krause, Pfl. Fam.ed. 2 16b: 139 (1935). Type Species.-A. pyramidata Tiegh.
Glabrous aerial stem-parasitic shrubs (possibly
sometimes initially terrestrial) with runners and opposite penninerved
leaves. Inflorescence axillary, primarily a subumbellate raceme
of several decussate pairs of dichasia (triads) with the central
flowers sessile and the lateral flowers pedicellate, but through
reduction sometimes a simple raceme or even a 2-flowered simple
umbel; bracts primarily single under each flower but sometimes
more in reduced infiorescences. Corolla 6-merous, inflated in
the mature bud; petals in the open flower united to the middle
or higher. Anthers linear, basifixed; pollen trilobate. Style
articulate 1.5-5 mm above the base; style base pyramidal. Basic
Chromosome Number. x = 12.
A genus of five species occurring in eastern Australia, New Guinea,
and Melanesia. Four of the species are found in the area dealt
with here. Some of them are polymorphic and their differences
difficult to define (see note in introduction and in Barlow 1966).
Key to Species
1. Corolla less than 40 mm long 3. A.
dictyophleba
1. Corolla more than 40 mm long 2
2. Leaves acuminate and acute, 12-20cm long 1. A. acuminatifolia
2. Leaves mostly rounded, rarely acute, not acuminate,
5-14 cm long 3
3. Corolla inflated at the base to
about twice the width of the calyx. Leaves lanceolate to elliptical,
7-14 cm long 4. A. pyramidata (Note: now A. dictyophleba)
3. Corolla not inflated at the base. Leaves
oblong to obovate, 5-7 cm long 2. A. banksiana
(Note: now A. dictyophleba)
Amylotheca
Genus Page
last updated 25 June 2003