Eucalyptus hypostomatica

Pokolbin box

Eucalyptus | Symphyomyrtus | Adnataria | Terminales | Heterophloiae

Eucalyptus hypostomatica L.A.S.Johnson & K.D.Hill, Telopea 4: 72 (1990).

T: New South Wales; Central Coast: 0.3 miles [0.5 km] from Lumbys Road on Langans Road, Correbare State Forest, 11 Nov.1974, M.I.H.Brooker 4624; holo: NSW; iso: CANB.

Tree to 30 m tall. Forming a lignotuber.
Bark rough on trunk and larger branches, box-type, flaky, grey, branches < 8 cm diameter usually smooth, grey.
Juvenile growth (coppice or field seedlings to 50 cm): stem rounded or square in cross-section, warty or smooth; juvenile leaves always petiolate, opposite for 4 to 6 nodes then alternate, broadly ovate to ovate, 3.8–7 cm long, 1.2–4 cm wide, discolorous, dull, mid-green above.
Adult leaves alternate, petiole 1–2 cm long; blade lanceolate to broadly lanceolate, 8–18 cm long, 1–3 cm wide, base tapering to petiole, distinctly discolorous, glossy, green (rarely dull green), side-veins greater than 45° to midrib, very densely reticulate, intramarginal vein parallel to and remote from margin, oil glands mostly island.
Inflorescence terminal compound, peduncles 0.3–0.8 cm long, buds 7 per umbel, pedicels 0.1–0.3 cm long. Mature buds ovoid, 0.3–0.4 cm long, 0.2–0.3 cm wide, green, scar present, operculum conical, stamens inflexed, with outer staminodes, anthers adnate, positioned obliquely at filament tip, cuboid, dehiscing by terminal pores, style long, stigma pin-head shaped, locules 3 or 4, the placentae each with 4 vertical ovule rows. Flowers white.
Fruit pedicellate (pedicels 0.1–0.3 cm long), barrel-shaped or obconical, 0.3–0.6 cm long, 0.3–0.5 cm wide, disc descending, valves 3 or 4, enclosed.
Seeds brown or grey, 1–2 mm long, ovoid or flattened-ovoid, often pointed at one end, dorsal surface shallowly pitted, hilum ventral.

Cultivated seedlings (measured at ca node 10): cotyledons reniform to oblong; stems square in cross-section, warty or smooth; leaves always petiolate, opposite for 5 or 6 pairs then becoming alternate, ovate-lanceolate, 3.5–7 cm long, 2–4 cm wide, base rounded to tapering, margin entire, apex pointed, discolorous, mid-green above, slightly paler beneath.

Flowering has been recorded in October and November.

An erect, medium-sized to tall tree of subcoastal ranges and hills from the Warragamba Dam area north to Correbare, Pokolbin and Wattagan State Forests in New South Wales, but not known in the Blue Mountains. It has grey box-type bark and discolorous leaves, the latter feature distinguishing it from the closely related and more northerly distributed E. rudderi. Other box species found in the coastal hinterland north of Sydney are E. moluccana, E. rummeryi and E. largeana, which differ in having irregularly flexed stamens all of which are fertile.

Eucalyptus hypostomatica belongs in Eucalyptus subgenus Symphyomyrtus section Adnataria because the buds have two opercula, ovules are in four rows, seeds are flattened-ovoid, cotyledons are reniform, and anthers are rigid on the staminal filaments. Within section Adnataria, E. hypostomatica is part of series Heterophloiae having box bark, terminal inflorescences, buds that shed the outer operculum early, stamens inflexed and the outer stamens sterile (staminodes). Other species in this series are E. rudderi from the Taree area of the North Coast of New South Wales, E. baueriana and E. polyanthemos in southern New South Wales and eastern Victoria, E. magnificata from the northern tablelands of New South Wales, E. conica from the slopes and adjacent tableland areas of New South Wales north from the Weddin Mountains to central Queensland, and E. fasciculosa from far western Victoria and adjacent parts of South Australia. A eighth species in the series, E. lucens, is found only west and south-west of Alice Springs.

Eucalyptus hypostomatica: Greek hypo-, below and stoma, mouth, referring to the stomates being mostly on the underside of the leaf.