Helicostylis
Description
Trees, dioecious or monoecious. Leaves alternate, on the lateral branches distichous; stipules not fully amplexicaul, free; blade entire or dentate, pinnately veined. Inflorescences on spurs in the leaf axils, unisexual, discoid-capitate, involucrate. Staminate inflorescences up to 15 together, pedunculate, receptacle revolute, at least before anthesis; tepals 4, at least basally connate; stamens (2-)4; pistillode absent. Pistillate inflorescences solitary, in pairs, or sometimes accompanied by one or 2 staminate ones, sessile or pedunculate, flowers several to numerous; tepals 4(-6), at least basally connate, the two inner tepals cohering on the inner surfaces by entangled thin hairs; ovary almost free; stigmas 2, vittiform, twisted. Infructescences discoid to subglobose; fruiting perianth enlarged, fleshy, yellow to orange; fruit basally adnate to the perianth; seed large, without endosperm, cotyledons thick and equal.
Wood
Vessels diffuse, but with a tendency towards a diagonal arrangement, mostly solitary (60-90%) and in short radical multiples of 2-4, round to oval, 5-12 per sq. mm, diameter 100-200 μm. Vessel-member length: 400-520 μm. Perforations simple. Intervascular pits alternate, round, oval or polygonal, 8-10 μm. Vessel-ray and vessel-parenchyma pits larger and irregularly shaped, half-bordered. Thin-walled tyloses often present.
Rays uniseriate and 2-5-seriate, 4-7 per mm, up to 310-900 μm high. Heterogeneous, composed of procumbent cells, except for the uniseriate margins of 1-2(5) rows of square and/or upright cells. Sheath cells few. Radial latex tubes always present, albeit sometimes sporadically. Rhom- bic crystals present, but few.
Parenchyma paratracheal, vasicentric-aliform with narrow to broad wings, sometimes tending towards unilateral arrangement abaxially, sometimes confluent, occasionally terminal. Strands of 4 cells. Few rhombic crystals present.
Fibres all or partly septate, lumen 7-14 μm, walls 2-5 μm. Pits simple, small, restricted to the radial walls. Gelatinous fibres few. Length: 1250-1300 μm. F/V ratio: 2.5-2.8.
Vitreous silica occasionally present in the fibres, rarely also in the axial parenchyma. Sclerotic cells occasionally noticed in the rays and/or axial parenchyma.
Rays uniseriate and 2-5-seriate, 4-7 per mm, up to 310-900 μm high. Heterogeneous, composed of procumbent cells, except for the uniseriate margins of 1-2(5) rows of square and/or upright cells. Sheath cells few. Radial latex tubes always present, albeit sometimes sporadically. Rhom- bic crystals present, but few.
Parenchyma paratracheal, vasicentric-aliform with narrow to broad wings, sometimes tending towards unilateral arrangement abaxially, sometimes confluent, occasionally terminal. Strands of 4 cells. Few rhombic crystals present.
Fibres all or partly septate, lumen 7-14 μm, walls 2-5 μm. Pits simple, small, restricted to the radial walls. Gelatinous fibres few. Length: 1250-1300 μm. F/V ratio: 2.5-2.8.
Vitreous silica occasionally present in the fibres, rarely also in the axial parenchyma. Sclerotic cells occasionally noticed in the rays and/or axial parenchyma.