Plants of the World Online (Kew) accepts 13 species.
They hybridise easily which can make identification difficult.
Some are widely cultivated as ornamentals or for their fruit.
They may have no above ground stem and creep along the ground.
There are 1 to 2 m high shrubby plants and 20 m trees.
Trunks vary from thin to very thick.
The trunks have very close scars from the spirally arranged leaf bases.
Dead leaf bases often don’t fall and may cover part to all of the trunk.
Older trunks may be smoother.
Leaves are on a short to long petiole with a rounded lower surface.
The upper surface can be flat, grooved or ridged.
The petiole has thin spines developed from the basal leaves.
The open leaf sheaths do not form a crown shaft.
Leaves are pinnate usually with a single terminal leaflet.
The midrib, rounded below and flat or angled above may have scales.
Each side of the midrib has up to 100 narrow lance-shaped leaflets.
They may be at regular intervals along the midrib or in small groups.
Leaflets taper to a sharp point and the edges are folded up (induplicate).
Those at the base become sharp spines.
Near the tip of the leaf leaflets lie in one or more planes.
They may have a waxy bloom and young leaves often have brown hairs.
Flowers are unisexual with male and female on different plants (dioecious).
The once branched axillary inflorescences are much shorter than the leaves.
Male and female panicles look similar.
On the short or long peduncle is a prophyll (first bract).
It may be large, boat-shaped with 2 keels and it covers the new inflorescences.
The other peduncular bracts are small to almost absent.
Branches off the midrib may be in spirals or groups.
They all have solitary spirally arranged flowers.
Each flower has a small triangular bract at the base.
Male flowers have 6 tepals in 2 whorls (or 3 sepals and 3 petals).
The cup-like sepal base has 3 triangular lobes.
The longer petals are fused at the base with 3 pointed or rounded lobes.
There are almost always 6 stamens on short filaments.
Filaments are inserted onto the base of the petals.
Linear anthers, longer than the filaments open to the sides.
There may be no, or a rudimentary pistillode.
Female flowers have a similar calyx to the males.
The 3 overlapping petals are longer than the calyx.
Their tips are usually rounded.
The 6 small staminodes are separate lobes or joined into a ring.
The ovary has 3 carpels that taper into short curved stigmas.
Each has one ovule but two of the three usually abort.
The oblong to ovoid fruit have old stigma fragments attached.
The smooth thin skin matures to black or brown.
Below this is a thin fleshy or fibrous layer.
The solitary seed has a thin papery membrane around it.
The seed usually has deep longitudinal grooves.
J.F.
