Alstonia scholaris

''Alstonia scholaris'', commonly called blackboard tree, scholar tree, milkwood or devil's tree in English, is an evergreen tree in the oleander and frangipani family Apocynaceae. Its natural range is from Pakistan to China, and south to northern Australia. It is a toxic plant, but is used traditionally for myriad diseases and complaints. It is called 'Saptaparna' in India and is the sacred tree of the 2nd Jain tirthankar Ajitnatha. It was first described by Linnaeus in 1767, who gave it the name ''Echites scholaris''.

Description

''Alstonia scholaris'' is a large tree growing up to tall (rarely to 60 m), with narrow buttressess that extend well up the trunk, giving it a fluted appearance. The bark is gray to pale gray with numerous lenticels, and all parts of the plant exude copious amounts of white sap when broken or cut.

The leaves are glossy dark green above and pale below, and they are arranged in whorls of four to eight, with petioles (leaf stalks) around long. The leaves are usually obovate (i.e. broadest near the apex) to elliptic, tapering towards the base and with a rounded tip, and there are 25 to 40 pairs of lateral veins at 80–90° to the midvein.

The inflorescences are much branched (), with peduncles up to long, and are produced at the ends of the branches. The small tubular flowers are cream or white and strongly scented. They are about long and wide, with five lobes. The calyx is about long, and the flower stalks are usually as long as or shorter. The corolla is white and tube-like, long. The lobes are broadly ovate or broadly obovate, , overlapping to the left.

The fruit is a pair of long papery follicles measuring up to about long and diameter. They contain numerous flat, brown seeds about long and wide, which have long tufts of hairs at each end.

Taxonomy

This plant was originally named ''Echites scholaris'' by Carl Linnaeus in 1767. The Scottish botanist Robert Brown transferred it to the genus ''Alstonia'' in 1810, as part of his work on the taxonomy of Apocynaceae.

Etymology

The genus was named in honour of botanist Charles Alston, and the species epithet ''scholaris'' is a reference to the traditional use of the timber of this tree for blackboards in Myanmar.

Distribution and habitat

''Alstonia scholaris'' grows in a broad range of habitats in tropical and subtropical areas, in a range of forest types from rainforest to savannah, on a variety of soils including alluviall, volcanic and metamorphic, and at altitudes from sea level to more than .

The tree is native to tropical and subtropical areas in the following countries/regions:
* China: Guangxi, Yunnan
* Indian subcontinent: Assam, Bangladesh, Bhutan, East Himalaya, India, Laccadive Is., Nepal, Pakistan, Sri Lanka, West Himalaya
* Indo-China: Andaman Is., Cambodia, Laos, Myanmar, Nicobar Is., South China Sea, Thailand, Vietnam
* Malesia: Borneo, Indonesia, Java, Lesser Sunda Is., Malaysia, Maluku, Philippines, Sulawesi, Sumatera,
* Papuasia: Bismarck Archipelago, New Guinea, Solomon Islands
* Australia: Northern Territory, Queensland, Western Australia

Toxicity

This is a toxic plant. At high doses, an extract of the plant exhibited marked damage to all the major organs of the body in both rats and mice. The toxicity appears to depend on the plant organ studied, as well as the season it is harvested, with the bark collected in the monsoon season being the least toxic, and bark in the summer the most. Intraperitoneal administration is much more toxic than oral. Rats were more susceptible to the poison than mice, and pure-bred mice strains were more susceptible than crossbred. The toxic effects may be due to the alkaloid echitamine in the bark.

Chemistry

The bark contains the alkaloids ditamine, echitenine, echitamine and strictamine. Echitamine is the most important alkaloid found in the bark, as it has been detected in all samples studied and collected from several locations. It is commercially sold as a herbal medicine.

Culture

''Alstonia scholaris'' is the state tree of West Bengal, India, where it is called Chhatim tree.

During convocation the leaves of ''Alstonia scholaris'' (''saptaparni'') are awarded to graduates and postgraduates of Visva-Bharati University by the chancellor, given to him in turn by the Prime Minister of India. In recent years, supposedly to prevent excessive damage to the environment, the vice-chancellor of the University accepts one ''saptaparni'' leaf from the chancellor on behalf of all the students. This tradition was initiated by the founder of the University, Rabindranath Tagore.

Uses

The wood of ''Alstonia scholaris'' has been recommended for the manufacture of pencils, as it is suitable in nature and the tree grows rapidly and is easy to cultivate. In Sri Lanka its light wood was used for coffins. The wood close to the root is very light and of white colour, and in Borneo was used for net floats, household utensils, trenchers, corks, etc. In Theravada Buddhism, the first Buddha is said to have used ''A. scholaris'' as the tree for achieving enlightenment.

The 1889 book ''The Useful Native Plants of Australia'' states that "the powerfully bitter bark of this tree is used by the natives of India in bowel complaints (''Treasury of Botany''). It has proved a valuable remedy in chronic diarrhoea and the advanced stages of dysentery. It has also been found effectual in restoring the tone of the stomach and of the system generally in debility after fevers and other exhausting diseases (''Pharmacopoeia of India''). It is described in the ''Pharmacopoeia of India'' as an astringent tonic, anthelmintic, and antiperiodic. It is held in the highest repute in the Phillippine Islands 'sic''" Despite its widespread traditional use as an 'antiperiodic' (a medicine which was supposed to cure the effects of malaria), it was found to have little to very weak activity against the cause of the disease, '' Plasmodium falciparum''. It had no effect against '' Giardia intestinalis'', and weak effect against '' Entamoeba histolytica'', which both cause diarrhoea.

Gallery

References

{{Taxonbar, from=Q135307

scholaris
Flora of Guangxi
Flora of Yunnan
Flora of tropical Asia
Trees of Australia
Gentianales of Australia
Flora of Queensland
Least concern flora of Australia
Least concern biota of Queensland
Symbols of West Bengal