John Stevens Henslow (February 6, 1796 - May 16, 1861) was an English botanist and geologist.

Henslow was born at Rochester in Kent. From his father, who was a solicitor in that city, he imbibed a love of natural history which largely influenced his career. He was educated at St. John's College, Cambridge, where he graduated as sixteenth wrangler in 1818, the year in which Sedgwick became Woodwardian professor of geology.

He accompanied Sedgwick in 1819 during a tour in the Isle of Wight, and there he learned his first lessons in geology. He also studied chemistry under Professor James Cumming and mineralogy under E. D. Clarke. In the autumn of 1819 he made some valuable observations on the geology of the Isle of Man (Trans. Geol. Soc., 1821), and in 1821 he investigated the geology of parts of Anglesey, the results being printed in the first volume of the Transactions of the Cambridge Philosophical Society (1821), the foundation of which society was originated by Sedgwick and Henslow.

Meanwhile, Henslow had studied mineralogy with considerable zeal, so that on the death of Clarke he was in 1822 appointed professor of mineralogy in the university at Cambridge. Two years later he took holy orders. Botany, however, had claimed much of his attention, and to this science he became more and more attached, so that he gladly resigned the chair of mineralogy in 1825, to succeed to that of botany. As a teacher both in the classroom and in the field he was eminently successful. To him Darwin largely owed his attachment to natural history, and also his introduction to Captain Fitzroy of HMS Beagle. Henslow founded the Cambridge University Botanic Garden in 1831.

In 1832 Henslow was appointed vicar of Cholsey-cum-Moulsford in Berkshire, and in 1837 rector of Hitcham in Suffolk, and at this latter parish he lived and laboured, endeared to all who knew him, until the close of his life. His energies were devoted to the improvement of his parishioners, but his influence was felt far and wide. In 1843 he discovered nodules of coprolitic origin in the Red Crag at Felixstowe in Suffolk, and two years later he called attention to those also in the Cambridge Greensand and remarked that they might be of use in agriculture. Although Henslow derived no benefit, these discoveries led to the establishment of the phosphate industry in Suffolk and Cambridgeshire; and the works proved lucrative until the introduction of foreign phosphates.

The museum at Ipswich, which was established in 1847, owed much to Henslow, who was elected president in 1850, and then superintended the arrangement of the collections. He died at Hitcham. His publications included A Catalogue of British Plants (1829; ed. 2, 1835); Principles of Descriptive and Physiological Botany (1835); Flora of Suffolk (with E. Skepper) (1866).

Reference

Walters SM & Stow EA Darwin's Mentor Cambridge University Press 2001 ISBN 0521591465 This article incorporates text from the public domain 1911 Encyclopædia Britannica.