''Semecarpus australiensis'', commonly known as the tar tree, native cashew, marking nut, or cedar plum, is a species of tree in the cashew, sumac and mango family

Anacardiaceae The Anacardiaceae, commonly known as the cashew family or sumac family, are a family of flowering plants, including about 83 genera with about 860 known species. Members of the Anacardiaceae bear fruits that are drupes and in some cases produce ...

, native to parts of

Melanesia Melanesia (, ) is a subregion of Oceania in the southwestern Pacific Ocean. It extends from Indonesia's New Guinea in the west to Fiji in the east, and includes the Arafura Sea. The region includes the four independent countries of Fiji, ...

and northern Australia. Contact with the plant can cause serious allergic reactions, a common characteristic of this family.

Description

The tar tree is a large

rainforest Rainforests are characterized by a closed and continuous tree canopy, moisture-dependent vegetation, the presence of epiphytes and lianas and the absence of wildfire. Rainforest can be classified as tropical rainforest or temperate rainfo ...

tree up to in height. The trunk is generally straight and cylindrical, and marked with numerous oval-shaped lenticels arranged in more or less vertical lines. When cut or damaged the trunk and branches produce a tar-like exudate which turns black on exposure to the air. The leaves are up to long by wide with prominent pale yellow veins. They are dark green and glabrous on the upper surface and chalky blue-green ( glaucous) underneath. The flowers are pentamerous and are quite small – petals on the male flowers are about long, while those on female flowers measure up to long. Flowering occurs in spring (September to November) and fruits are produced through the summer. The fruits are a true nut attached beneath a colourful fleshy

receptacle Receptacle may refer to: Biology * Receptacle (botany), a plant anatomical part * Seminal receptacle, a sperm storage site in some insects Electrical engineering * Automobile auxiliary power outlet, formerly known as ''cigarette lighter recep ...

. To the casual observer it appears to be a "fruit" (the receptacle) with a "seed" (the nut) on the outside. The receptacle is actually the swollen flower stem or pedicel and is much larger than the nut (see images below). Neither are edible to humans in their raw state due to the presence of highly irritant resins.

Taxonomy

''Semecarpus australiensis'' was first described by the prodigious German botanist Adolf Engler. His treatment was published in volume 4 of ''Monographiae Phanerogamarum'' in 1883.

Etymology

The genus name ''Semecarpus'' 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 ...

''semi-'', meaning half, and the

Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic p ...

''κᾰρπός (karpós)'', meaning fruit. It is a reference to the appearance of the fruit. The

species epithet Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany) A botanical name ...

means "from Australia".

Distribution and habitat

The natural range of ''Semecarpus australiensis'' is from the Moluccas in the west, into

New Guinea New Guinea (; Hiri Motu: ''Niu Gini''; id, Papua, or , historically ) is the world's second-largest island with an area of . Located in Oceania in the southwestern Pacific Ocean, the island is separated from Australia by the wide Torr ...

, the Bismark Archipelago,

Vanuatu Vanuatu ( or ; ), officially the Republic of Vanuatu (french: link=no, République de Vanuatu; bi, Ripablik blong Vanuatu), is an island country located in the South Pacific Ocean. The archipelago, which is of volcanic origin, is east of no ...

and New Caledonia in the east; and south to the coastal parts of the

Northern Territory The Northern Territory (commonly abbreviated as NT; formally the Northern Territory of Australia) is an Australian territory in the central and central northern regions of Australia. The Northern Territory shares its borders with Western Au ...

and

Queensland ) , nickname = Sunshine State , image_map = Queensland in Australia.svg , map_caption = Location of Queensland in Australia , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , established_ ...

in Australia. It grows in lowland

, monsoon forest and gallery forest, close to the sea or to water courses.

Ecology

The fruits of this species are eaten by cassowaries (''Casuarius casuarius'') with no apparent adverse effects from the sap that is toxic to humans. The tree also serves as one of the host plants for the larvea of the Purple Line-blue butterfly (''Prosotas dubiosa'').

Toxicity

Like many other species in the family Anacardiaceae, this tree may cause severe allergic responses after contact with it. The agents responsible for the allergies are resinous phenolic compounds found in most parts of the plant, including the fruits and the exudate from the trunk and branches. Direct contact with the tree is not necessary to elicit the allergic response — in March 1954, an article appeared in the local newspaper in Cairns, Australia, describing how a number of children suffered rashes after swimming in a stream beneath a tar tree.

Indigenous uses

Indigenous Australians Indigenous Australians or Australian First Nations are people with familial heritage from, and membership in, the ethnic groups that lived in Australia before British colonisation. They consist of two distinct groups: the Aboriginal peoples o ...

were are aware of the toxic nature of this plant, and kept their children away from it. They also knew that the fleshy receptacle and the nut (which is similar to the cashew) were edible, and they developed methods of deactivating the toxins so that they could be eaten. These included covering the hands with clay before handling the plant, and roasting the nuts in a fire. Even the smoke from the fire can cause problems, and they were careful to prepare the food well away from their camp.

Gallery

File:Semecarpus-australiensis-SF21353-02.jpg , Mature fruit File:Semecarpus-australiensis-SF21349.jpg , Detail of trunk File:Semecarpus australiensis leaves SF21170.jpg , Foliage File:Semecarpus australiensis exudate SF21170.jpg , Branch with black exudate

References

External links

* *
View a map
of recorded sightings of this species at the Australasian Virtual Herbarium
View observations
of this species on iNaturalist
See images
of this species on Flickriver {{Taxonbar, from=Q7449189 Bushfood australiensis