Danish-born botanist who served as superintendent of the East India Company's botanic garden in Calcutta from 1815-1846. As well as making large collections of plants in India, Nepal and other parts of Asia, Wallich is credited with bringing the substantial East India Company herbarium to Europe for distribution in 1828.

Wallich was born Nathanael Wolff Wallich in Copenhagen on 28 January 1786, the son of a Jewish merchant. There he studied botany under Martin Vahl and qualified as a doctor of medicine in 1806. Wallich arrived in India in 1807 to take up the appointment of surgeon at the Danish factory in Serampore, near Calcutta. When the factory was taken over by the East India Company the following year, Wallich entered the service of the British, being transferred in 1809 to assist at the Royal Botanic Gardens in Calcutta. After the gardens' superintendent, William Roxburgh, fell ill and retired in 1814, Wallich succeeded him, taking on the role in 1817. Wallich distinguished himself at the gardens by making extensive collections of plant specimens, which he distributed to other gardens and herbaria in Europe and North America. He also described a great deal of species new to science, and added material to Roxburgh's posthumously published Flora Indica.

Wallich's travels in Asia were very fruitful. In 1820 he was commissioned to explore Nepal, sending consignments of plants collected there to the likes of Sir Joseph Banks and A.B. Lambert in Britain. He later published Tentamen florae Nepalensis illustratae (1824-1826), which was printed at the new Asiatic Lithographic Press in Serampore. He visited the Malaysian Peninsula in 1822, collecting much in Singapore, where he laid out a botanic garden. In 1825 he went to the forests of Hindustan and following on from this explored Ava and Lower Burma before he was taken ill and thus returned to England in 1828. Over the course of the 1820s, he and his assistants had gathered nearly 10,000 different species for the Calcutta herbarium.

Wallich's most important publication was the three-volume Plantae Asiaticae Rariores, in which he gave descriptions of many new East Indian plants. He completed the work while invalided in England from 1828-1832, having taken with him 8,000 plant specimens for distribution. Returning to India, he set about making further collecting expeditions, for example searching for the wild tea shrub in Assam. However, his health never stabilised and he resigned from his post in Calcutta in 1846.

Living in London, Wallich continued his botanical work and served as vice-president of the Linnean Society. He received the degree of MD from Marischal College, Aberdeen, in 1819; was a Fellow of the Royal Society of Edinburgh and of the Danish Royal Society of Copenhagen; and was elected a Fellow of the Royal Society in 1829. He was also a fellow of the Royal Asiatic Society and of the Geological Society of London. He died in London on 28 April 1854. An obelisk to Wallich's memory was erected at the Calcutta Botanic Gardens and the palm genus Wallichia Roxb. commemorates him.

Sources:
G.S. Boulger, rev. A.Grout, 2005, "Wallich, Nathaniel (1785-1854)", Oxford Dictionary of National Biography, online edn:

http://www.oxforddnb.com/view/article/28564, accessed 11 February 2011
R. de Candolle and A. Radcliffe-Smith, 1981, "Nathaniel Wallich (1786-1854) and the herbarium of the Honourable East India Company, and their relation to the de Candolles of Geneva and the Great Prodromus", Botanical Journal of the Linnean Society, 83: 325-348
R. Desmond, 1992, The European discovery of the Indian flora
K. Thothathri, 1989, "Nathaniel Wallich (1786-1854) and his contributions to the botany of India and neighbouring countries", Bulletin of the Botanical Survey of India.