''Eucalyptus expressa'', commonly known as the Wollemi stringybark, is a recently discovered Australian tree species. It has rough, fibrous

stringybark A stringybark can be any of the many ''Eucalyptus'' species which have thick, fibrous bark. Like all eucalypts, stringybarks belong to the family Myrtaceae. In exceptionally fertile locations some stringybark species (in particular messmate strin ...

on the trunk and larger branches, lance-shaped to curved adult leaves, flower buds in groups of between seven and twenty four and hemispherical to shortened spherical fruit with the valves extending well beyond the rim of the fruit.

Description

''Eucalyptus expressa'' is a tree that typically grows to a height of and has rough, fibrous stringybark on the trunk, and branches wider than . The bark is grey brown, with reddish tinges. Young plants have some leaves arranged in opposite pairs, otherwise alternate, broadly lance-shaped to egg-shaped, glossy green on one surface, paler on the other, long and wide. Adult leaves are arranged alternately, more or less the same glossy green on both sides, lance-shaped to curved, long and wide on a petiole long. The edges of older leaves are scalloped or irregularly toothed and the veins diverge at an angle of 30 to 40 degrees to the midrib. The flower buds are arranged in leaf

axil A leaf ( : leaves) is any of the principal appendages of a vascular plant stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, ...

s in groups of between seven and twenty four on a

peduncle Peduncle may refer to: *Peduncle (botany), a stalk supporting an inflorescence, which is the part of the shoot of seed plants where flowers are formed *Peduncle (anatomy), a stem, through which a mass of tissue is attached to a body **Peduncle (art ...

long, the individual buds on

pedicels In botany, a pedicel is a stem that attaches a single flower to the inflorescence. Such inflorescences are described as ''pedicellate''. Description Pedicel refers to a structure connecting a single flower to its inflorescence. In the absenc ...

long. Mature buds are spindle-shaped, long and wide with a conical operculum up to twice as long as the floral cup. The fruit is a woody, hemispherical to shortened spherical capsule, long and wide with the valves protruding above the rim. This species is similar to '' E. eugenioides'' but differs in its tall habit, scalloped leaf edges and conspicuously protruding valves in the fruit.

Taxonomy and naming

''Eucalyptus expressa'' was first formally described in 2012 by Stephen Bell and

Dean Nicolle image:Dean-Nicolle-Deanei.JPG, 270px, Dean Nicolle and ''Eucalyptus deanei'' Dean Nicolle (born 1974), is an Australian botanist, arboriculture, arborist and ecologist. He is widely recognised as the leading authority on the genus ''Eucalyptus''. ...

from a specimen alongside the

Putty Road Putty is a material with high plasticity, similar in texture to clay or dough, typically used in domestic construction and repair as a sealant or filler. Although some types of putty (typically those using linseed oil) slowly polymerise and beco ...

near Bulga and the description was published in the journal '' Telopea''. Before its formal description, it was known as ''E.'' sp. aff. ''eugenioides'' (Bees Nest Ridge). The

specific epithet In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

(''expressa'') is from the

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power ...

''expressus'', which means “prominent and clearly exhibited”, and refers to the long, narrow, prominent external valves of the fruit.Klaphake, V. (2010) Eucalyptus of the Sydney Region. Second edition

Distribution and habitat

The Wollemi stringybark is a tall forest tree from at least seven populations in sheltered gullies in the

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates ...

ranges north-west of Sydney. It occurs in and near

Wollemi National Park The Wollemi National Park () is a protected national park and wilderness area that is located in the northern Blue Mountains and Lower Hunter regions of New South Wales, in eastern Australia. The park, the second largest national park in New ...

and

Yengo National Park The Yengo National Park is a protected national park that is located in the Lower Hunter region of New South Wales, in eastern Australia. The park is situated northwest of the Sydney central business district, south of , north of , and ...

Conservation status

A ROTAP rarity rating of 2KC has been proposed for this species. It is poorly known and suspected of being at risk, occurring in a range of less than , although at least partially conserved in a national park.

Photos

File:Wollemi String2.jpg, Wavy edged leaves File:Wollemi String3.jpg, Wollemi stringybark measured at 42 metres tall File:Wollemi String4.jpg, Stringybark trunk File:Dean-Nicolle-Deanei.JPG, One of the describing scientists,

and an associate species of the Wollemi stringybark,

mountain blue gum ''Eucalyptus deanei'', commonly known as mountain blue gum, round-leaved gum, or Deane's gum, is a species of large tree endemic to New South Wales. It has smooth bark, lance-shaped leaves that are paler on the lower surface, flower buds in group ...

References