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

cashew The cashew tree (''Anacardium occidentale'') is a tropical evergreen tree native to South America in the genus ''Anacardium'' that produces the cashew seed and the cashew apple accessory fruit. The tree can grow as tall as , but the dwarf cult ...

sumac Sumac ( or ), also spelled sumach, is any of about 35 species of flowering plants in the genus ''Rhus'' and related genera in the cashew family (Anacardiaceae). Sumacs grow in subtropical and temperate regions throughout the world, including Eas ...

and

mango A mango is an edible stone fruit produced by the tropical tree ''Mangifera indica''. It is believed to have originated in the region between northwestern Myanmar, Bangladesh, and northeastern India. ''M. indica'' has been cultivated in South a ...

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, Va ...

and northern

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

. 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 rainfores ...

tree up to in height. The trunk is generally straight and cylindrical, and marked with numerous oval-shaped

lenticel A lenticel is a porous tissue consisting of cells with large intercellular spaces in the periderm of the secondarily thickened organs and the bark of woody stems and roots of dicotyledonous flowering plants. It functions as a pore, providing a ...

s arranged in more or less vertical lines. When cut or damaged the trunk and branches produce a tar-like

exudate An exudate is a fluid emitted by an organism through pores or a wound, a process known as exuding or exudation. ''Exudate'' is derived from ''exude'' 'to ooze' from Latin ''exsūdāre'' 'to (ooze out) sweat' (''ex-'' 'out' and ''sūdāre'' 'to ...

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 Glabrousness (from the Latin '' glaber'' meaning "bald", "hairless", "shaved", "smooth") is the technical term for a lack of hair, down, setae, trichomes or other such covering. A glabrous surface may be a natural characteristic of all or part of ...

on the upper surface and chalky blue-green (

glaucous ''Glaucous'' (, ) is used to describe the pale grey or bluish-green appearance of the surfaces of some plants, as well as in the names of birds, such as the glaucous gull (''Larus hyperboreus''), glaucous-winged gull (''Larus glaucescens''), g ...

) 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. 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 Pedicle or pedicel may refer to: Human anatomy *Pedicle of vertebral arch, the segment between the transverse process and the vertebral body, and is often used as a radiographic marker and entry point in vertebroplasty and kyphoplasty procedures ...

and is much larger than the nut (see

images An image is a visual representation of something. It can be two-dimensional, three-dimensional, or somehow otherwise feed into the visual system to convey information. An image can be an artifact, such as a photograph or other two-dimensiona ...

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 German(s) may refer to: * Germany (of or related to) ** Germania (historical use) * Germans, citizens of Germany, people of German ancestry, or native speakers of the German language ** For citizens of Germany, see also German nationality law **Ge ...

botanist Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the Ancient Greek wo ...

Adolf Engler Heinrich Gustav Adolf Engler (25 March 1844 – 10 October 1930) was a German botanist. He is notable for his work on plant taxonomy and phytogeography, such as ''Die natürlichen Pflanzenfamilien'' (''The Natural Plant Families''), edited with ...

. 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 of the ...

''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 peri ...

''κᾰρπός (karpós)'', meaning fruit. It is a reference to the appearance of the fruit. The species epithet means "from Australia".

Distribution and habitat

The natural range of ''Semecarpus australiensis'' is from the

Moluccas The Maluku Islands (; Indonesian: ''Kepulauan Maluku'') or the Moluccas () are an archipelago in the east of Indonesia. Tectonically they are located on the Halmahera Plate within the Molucca Sea Collision Zone. Geographically they are located eas ...

in the west, into

New Guinea New Guinea (; Hiri Motu Hiri Motu, also known as Police Motu, Pidgin Motu, or just Hiri, is a language of Papua New Guinea, which is spoken in surrounding areas of Port Moresby (Capital of Papua New Guinea). It is a simplified version of ...

, the

Bismark Archipelago The Bismarck Archipelago (, ) is a group of islands off the northeastern coast of New Guinea in the western Pacific Ocean and is part of the Islands Region of Papua New Guinea. Its area is about 50,000 square km. History The first inhabitants o ...

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 ) , anthem = "" , image_map = New Caledonia on the globe (small islands magnified) (Polynesia centered).svg , map_alt = Location of New Caledonia , map_caption = Location of New Caledonia , mapsize = 290px , subdivision_type = Sovereign st ...

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 states and territories of Australia, Australian territory in the central and central northern regions of Australia. The Northern Territory ...

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_ ...

. It grows in lowland

monsoon forest Seasonal tropical forest, also known as moist deciduous, semi-evergreen seasonal, tropical mixed or monsoon forests, typically contain a range of tree species: only some of which drop some or all of their leaves during the dry season. This tropic ...

and

gallery forest A gallery forest is one formed as a corridor along rivers or wetlands, projecting into landscapes that are otherwise only sparsely treed such as savannas, grasslands, or deserts. The gallery forest maintains a more temperate microclimate above th ...

, close to the sea or to water courses.

Ecology

The fruits of this species are eaten by

cassowaries Cassowaries ( tpi, muruk, id, kasuari) are flightless birds of the genus ''Casuarius'' in the order Casuariiformes. They are classified as ratites (flightless birds without a keel (bird anatomy), keel on their sternum bones) and are native t ...

(''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 In polymer chemistry and materials science, resin is a solid or highly viscous substance of plant or synthetic origin that is typically convertible into polymers. Resins are usually mixtures of organic compounds. This article focuses on natu ...

phenolic compounds found in most parts of the plant, including the fruits and the

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 Cairns (, ) is a city in Queensland, Australia, on the tropical north east coast of Far North Queensland. The population in June 2019 was 153,952, having grown on average 1.02% annually over the preceding five years. The city is the 5th-most-p ...

, 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 ...

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 The ''Australasian Virtual Herbarium'' (AVH) is an online resource that allows access to plant specimen data held by various Australian and New Zealand herbaria. It is part of the Atlas of Living Australia (ALA), and was formed by the amalgamat ...

View observations
of this species on

iNaturalist iNaturalist is a social network of naturalists, citizen scientists, and biologists built on the concept of mapping and sharing observations of biodiversity across the globe. iNaturalist may be accessed via its website or from its mobile applic ...

See images
of this species on Flickriver {{Taxonbar, from=Q7449189 Bushfood australiensis