Alstonia scholaris, commonly called blackboard tree or devil's tree in English, is an evergreen tropical tree in the family Apocynaceae. It is native to southern China, tropical Asia and Australasia, it is a commonly planted ornamental plant in these areas. It is a toxic plant, but traditionally it is used medicinally for myriad diseases and complaints. Alstonia scholaris is a glabrous tree and grows up to 40 m (130 ft) tall. Its mature bark is grayish and its young branches are copiously marked with lenticels.
The upper side of the leaves are glossy, while the underside is greyish. Leaves occur in whorls of three to ten; petioles are 1–3 cm (0.39–1.18 in); the leathery leaves are narrowly obovate to very narrowly spathulate, base cuneate, apex usually rounded; lateral veins occur in 25 to 50 pairs, at 80–90° to midvein. Cymes are dense and pubescent; peduncle is 4–7 cm (1.6–2.8 in) long. Pedicels are usually as long as or shorter than calyx. The corolla is white and tube-like, 6–10 mm (0.24–0.39 in); lobes are broadly ovate or broadly obovate, 2–4.5 mm (0.079–0.177 in), overlapping to the left. The ovaries are distinct and pubescent. The follicles are distinct and linear.Flowers bloom in the month October. The flowers are very fragrant similar to the flower of Cestrum nocturnum.
Seeds of A. scholaris are oblong, with ciliated margins, and ends with tufts of hairs 1.5–2 cm (0.59–0.79 in). The bark is almost odorless and very bitter, with abundant bitter and milky sap.
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 echitamine content of the bark, an alkaloid.
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 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, Gurudeb Rabindranath Tagore.
Leaves and flowers in Kolkata, West Bengal, India
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 is used for coffins. In Borneo the wood close to the root is very light and of white color, and is used for net floats, household utensils, trenchers, corks, etc. In Theravada Buddhism, the first Buddha is said to have used Alstonia scholaris as the tree for achieving enlightenment.
The 1889 book The Useful Native Plants of Australia records that "The powerfully bitter bark of this tree is used by the natives [sic] 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 (Pharm. 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]. For further information see Dymock (Materia Medica of Western India). Most writers who speak of it at all speak of it in terms of the highest praise. A very full account of the various substances which have been extracted from this bark will be found in Watt's Dict., 3rd suppt. Part i., page 688 et seq."At one time, decoctions of the leaves were used for beriberi. The bark contains the alkaloids ditamine, echitenine, echitamine and strictamine. Echitamine is the most important alkaloid found in the bark, it has been detected in all samples studied, from different collection locations, and is also detected in bark commercially sold as herbal medicine.
Its English names “scholar's tree” and “blackboard tree” refer to its use in making school black boards and wooden slates for children to write on. Its other name “devil tree” or “shaitan ka jhad” is based on the belief in Western India, that the tree is an abode of evil spirits.
Alstonia scholaris is native to the following regions: China: Guangxi, Yunnan. Indian subcontinent: Bangladesh, India, Nepal, Pakistan, Sri Lanka. Distribution: India to Indonesia, tropical Australia and Africa. Cultivated in Pakistan as an ornamental. The inner bark is of medicinal value and is used as a source of anti-malerial drug.