Professor Henslow’s Legacy

mem HenslowTo CUBG on Saturday for the Festival of Plants: it started cloudy and windy but cleared up to blue sky and bright sunshine. As usual, there was a marquee with stalls showing the work of the Sainsbury Laboratory and other plant research centres, a problem-solving booth (thankfully, my wisteria isn’t currently wilting), refreshments, and specialist nurseries displaying their tempting wares along the Main Avenue. There were also guided tours of various parts of the garden, and I signed up for a whizz round the systematic beds, in the delightful company of Rod Mulvey, a volunteer (and highly knowledgeable) Garden Guide.

Refreshments under the trees

Refreshments under the trees

Signing up for tours

Signing up for tours

I have to confess that I usually go to the systematic beds only to see specific plants when they are at their flowering best. At the moment the iris are glorious, and later in the year there will be the cosmos, echinaceas, eryngiums, nightshades, etc. etc. But at this time of year, there tends to be quite a lot of bare earth with labels, in curved beds of various shapes, intersected by daisy-studded grass paths, and surrounded by ancient, low hawthorn hedges, buzzing with insects.

The were originally called the order beds, and were part of the layout of the garden from its opening in 1846. An open-air classroom, they group together the different orders of plants, from the monocotyledons through the dicotyledons and the various subdivisions of the latter: Compositae, Labiatae, Umbelliferae, Cruciferae, Rosaceae, etc. etc. (Knowledgeable people will know what is wrong with this list, but bear with me.)

The hawthorn hedges group like plant families with like, and the classification used is the sexual system of Linnaeus, as modified by the more detailed physiological investigations of the Swiss botanist Augustin Pyramus de Candolle (1778–1841). The curving beds (rather than regimented rows and rectangles) were apparently influenced by Romantic theories of landscape, but the scientific intentions were serious.

A version of the famous image of Linnaeus in Lapp costume; other more conventional portraits show a genial man in a wig

A version of the famous image of Linnaeus in Lapp costume; other more conventional portraits show a genial man in a wig

Augustin Pyramus de Candolle

Augustin Pyramus de Candolle

Rod gave out hand lenses, and – sharp intake of breath! – PICKED SOME FLOWERS for us to look at, describing the structure, including the extraordinary modifications of petals which evolved to match the specific weights and tongue lengths of pollinating insects. (Darwin predicted that an insect with an enormous proboscis must exist to pollinate and thus fertilise a particular Madagascan flower, Angraecum sesquipedale: a possible moth (Xanthopan morganii praedicta) was discovered in 1907, but it was only in 1992 that there were confirmed sightings of the moth in action on the flowers.)

Doronicon orientale (leopard's bane), picked strictly for the purpose of education

Doronicon orientale (leopard’s bane), picked strictly for the purpose of education

The problem with this succession of beds and hedges is that more recent, and continuing, developments in taxonomy, not least at the level of the plants’ DNA, is leading to the reclassification of whole families, as well as individual plants. These days, the Compositae should be known as the Asteraceae, the Umbelliferae as Apiaceae, and the Labiatae as Lamiaceae, and the further subdivisions become ever more complex. So how should the Botanic Gardens respond? Unthinkable, surely, to uproot the hawthorn hedges and realign the beds – apart from the history of botanical theory which they exemplify, the Garden is Grade II* listed. An interested challenge for the new Director and Curator!

This fascinating walk reminded me of the early history of the Garden on its present site, and the role played by John Stevens Henslow, ‘Darwin’s Mentor’ and the father-in-law of Joseph Dalton Hooker, in its establishment. The original University Botanic Garden, the ‘Walkerian Garden’ was situated in what is now the New Museums Site, off Downing Street, on land formerly part of an Augustinian friary, and donated by Richard Walker, Vice-Master of Trinity, on the advice of the great Philip Miller, in the early 1760s. It was a physic garden, growing medicinal plants for medical students, and perhaps the Sophora tree which Elwes and Henry record as growing on the site early in the twentieth century was a survival from this garden.

John Stevens Henslow

John Stevens Henslow

Henslow (1796–1861) began his academic career as a student of St John’s College, Cambridge, in 1814. He graduated BA in early 1818 and became a fellow of the Linnean Society at the same time. He took up the study of geology under the great Adam Sedgwick, and the pair founded the Cambridge Philosophical Society in 1819. He became professor of mineralogy in 1822, and in 1825, on the death of the long-serving Thomas Martyn, he succeeded as professor of botany and gave up the mineralogy chair. He had married in 1823 and was ordained in 1824.

Henslow was determined both to revitalise the teaching of botany in Cambridge (Martyn had barely visited, let alone lectured, for the previous thirty years) and also to persuade the University to provide a bigger site for a new Garden. He was modest about his own botanical knowledge at this time (saying in his 1846 pamphlet on the need for a new garden that ‘I knew very little indeed about botany … but I probably knew as much of the subject as any other resident in Cambridge’); but he knew what needed to be done to give Cambridge the status in the botanical world to which he was convinced it should aspire: and he did it.

In his later career, Henslow maintained his study of botany (and his Cambridge chair) while serving – equally conscientiously – as vicar of Hitcham in Suffolk. His most important book, The Principles of Descriptive and Physiological Botany, published in 1835, made available in English the work of de Candolle and other European botanists: he also published  a botanical dictionary and a student guide, and edited a flora of Suffolk. He wrote widely for scientific journals, and a collection of his papers produced between 1821 and 1838, selected and introduced by Professor John Parker, until recently Director of the Garden, was published in 2014.

Henslow’s best known claim to fame is undoubtedly his refusal of the post of naturalist on the Beagle, and his suggestion that his protégé Charles Darwin should be offered it. (Incidentally, Darwin was actually the third choice, Leonard Jenyns, Henslow’s brother-in-law and first biographer being the second.) But botanists worldwide, and the people of Cambridge, owe him a great debt for the wonderful institution he had the vision and determination to establish.

Oh, and I mentioned specialist nurseries … I admit to being tempted, and falling.

The spoils ...

The spoils …

The Nicotiana mutabilis (from Fernatix) will go in my tall pots when the tulips currently in residence are finished, and the two viola species and helianthemum (from Little Heath Farm Nursery) and linaria (from D’Arcy and Everest, who – eat your hearts out, alpine enthusiasts! – aren’t at Chelsea this year) are for my trough, when I can reach it again after the Great Plant Giveaway is over next Friday. So thanks again, @CUBotanicGarden and Professor Henslow!


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