As Darwin’s Professor, Henslow was responsible for inspiring his love of natural history and it was Henslow that put him forward for the Voyage of the Beagle. Darwin later described it as “by far the most important event in my life”.

Henslow’s progressive, hands-on teaching techniques, which included meticulous observing, collecting, storing and recording were ground-breaking for the time and are why Darwin’s detailed specimens survive to this day, informing modern research.

Other Darwin-related items held in the extensive Herbarium collection include:

• Darwin’s first ever recorded specimen, collected on a field trip with Henslow in North Wales
• The diary of Darwin’s class rival, Charles Babington, who would irritate Darwin by going to the Cambridge Fens in the early mornings to collect the ‘best’ beetles first
• Original wall charts, illustrated by Henslow (such as the one pictured above) that Darwin learned from and saw displayed in the walls of the lecture room
• Henslow’s personal copies of James Edward Smith’s Compendium floræ Britannicæ (1829), in which he notes specimens found during the numerous forays to the local countryside with students – including Darwin.

The Cambridge episode of Susan Calman’s Great British Cities will air at 9pm, 22nd March on Channel 5 and the series is also available on My5.

Professor John Stevens Henslow (1796-1861) was a British botanist, clergyman, and geologist who popularised botany at the University of Cambridge by introducing new methods of teaching the subject. Notably he initiated the move of the Cambridge University Botanic Garden to its present site in 1846.

In 1822 Henslow was made Professor of Mineralogy at Cambridge and in 1825 he became Professor of Botany, where he introduced a teaching technique fostering independent discovery. His students were inspired to collect plants and asked to examine and record the characteristics of the structures they found.

This method, combined with unusual field trips, interesting lectures, and Henslow’s natural enthusiasm, made botany one of the most popular subjects at the university. His class list would extend to as many as 80 students, at a time when the total University population was only in the low hundreds. One of the students Henslow served as a source of inspiration for was Charles Darwin, whom he taught between 1829 and 1831. 

Between 1821 and 1835 Henslow expanded and reorganised the Cambridge University Herbarium, adding over 10,000 specimens from across Britain and the wider world. It became the basis for the Cambridge University Herbarium that we know today. He organised his herbarium to emphasise variation within species and determine the limits between species. To aid him, he enlisted about a hundred collaborators, one of whom was the young Charles Darwin.

Charles Darwin attended Cambridge University in 1828 to study Theology with a view to becoming a priest but was soon skipping his own classes to attend Henslow’s botany lectures and field trips instead. Darwin took Henslow’s course three years running and by the end was assisting with teaching it.

It was Professor Henslow’s inspirational teaching on the nature of plant species that established the necessary intellectual framework for Darwin’s subsequent evolutionary thinking.

When Darwin took his famous trip on the HMS Beagle in 1831, his place was arranged by Henslow. Visiting the Galapagos islands, Darwin began by arranging his observations in a framework set out by Henslow that assumed the stability of species.

In recent years, academics have put forth that the instruction Darwin received from Henslow set the framework for the new understanding Darwin came to: that varieties are incipient species. Darwin’s theory of mutability would later find its full expression in his canonical On the Origin of Species first published in 1859.

Henslow remained a mentor and friend to Darwin for the rest of his life. Other famous students and contemporaries of Henslow included Miles Joseph Berkeley, Charles Cardale Babington, Leonard Jenyns, Richard Thomas Lowe and William Hallowes Miller.