Just back from a brilliant tour of the Cambridge University Herbarium, in the Sainsbury Laboratory next to, but not formally connected to, the Cambridge University Botanic Garden. Many thanks to Christine Bartram, the Chief Herbarium Technician, for making us so welcome and for sharing her unrivalled knowledge of the collection of more than one million items, which arrived at its present state-of-the-art, temperature- and humidity-controlled home only in 2011.

Before that, the specimens were held on the Downing Site, in less than ideal conditions, and with issues of access and cataloguing such that fascinating items collected by world-famous botanists are still coming to light.

All the plants were deep frozen before being moved into the new facility, in a successful attempt to remove the minute insects that thrive and breed among dried plant material, including the biscuit beetle (Stegobium paniceum – it doesn’t only eat plants!) and the vodka beetle (Attagenus smirnovi – not known to indulge in the drink: the name honours one E.S. Smirnov, no relation).

The biscuit beetle (2–3 mm).

The vodka beetle (2-5 mm).

The sheets are kept in cardboard folders in sliding shelves which are very economical of space. Darwin’s specimens, sent to the great John Stevens Henslow (who occasionally complained about his protégé’s techniques of preservation), and those of Henslow himself, were, until the 1960s, stored by genus rather than by collector: it was not even clear how many of Darwin’s own specimens were held. These days, they are identified by blue bands at the top and bottom of their mounting cards (type specimens in the collection have red bands), and the Beagle specimens (marked ‘Priority’ for evacuation in case of disaster) are stored, appropriately enough, in Solander cases.

Some of Darwin’s specimens.

Henslow is of course regarded as the founding father of all things botanic in Cambridge (or re-founder, to acknowledge the work of John Ray). Legend has it that John and Thomas Martyn, father and son (1699–1768 and 1735–1825), who were Henslow’s predecessors as professor of botany, holding the post for 92 years between them, were hardly ever in the city and very rarely lectured. Christine Bartram points out that the professorial post was not funded (the father earned his living as a London physician and the son as a clergyman), and lectures dried up because they were not well attended. Both were however active in naming plants and creating herbaria, and both published on botanical topics, so perhaps history has been unkind to them?

John (right) and Thomas Martyn, with one of their sheets.

But it was undoubtedly Henslow’s drive and energy which established the Botanic Garden on its existing site. He also took on the responsibility of remounting many of the Martyns’ specimens (which had been left to moulder in a wooden cupboard), as well as creating his own ‘posters’ of botanical paintings to use as teaching aids,

One of Henslow’s teaching posters, showing Arum maculatum (cuckoo-pint).

Henslow’s botanical painting of Eschscholzia californica.

making drawings of strange fungi in Christ’s College wine cellar,

Pencil sketch of an unnamed fungus, lurking under Christ’s College.

Botanical watercolours of fungi by Henslow.

trying to improve the living conditions of his parishioners at Hitcham in Suffolk, by teaching their children and researching the pests and diseases which undermined their crops, and writing books and pamphlets on all aspects of botany and on university reform (as well as dealing with the packages which arrived from Darwin, where he was helped with the taxonomy by Joseph Dalton Hooker).

A specimen (Scalesia incisa) sent back by Darwin, with annotations and drawing by Hooker.

The earliest individual specimen in the herbarium is a sheet of four leaves sent back from India in 1703: unfortunately, they cannot now be identified. As well as the Martyns and Henslow, John Lindley (1799–1865) was a significant contributor to the collection. Best remembered as the secretary of the (Royal) Horticultural Society, whose library is named after him, Lindley sent collectors all over the world – the Lobb brothers, the unfortunate David Douglas, and Robert Fortune, who sent Lindley a sample of Forsythia, modestly suggesting that he would not be averse to having it named after himself: Forsythia suspensa var. fortunei it remains.

Forsythia fortunei, with the letter from Fortune attached.

But one fascinating aspect of the herbarium’s significance – and the reason why herbaria are unlikely ever to be replaced by digital resources, however valuable these may be as adjuncts – is the continually evolving method of DNA research, which requires less and less actual material to provide more and more answers about plant relationships.

We’re not quite at the ‘Jurassic Park’ stage of being able to recreate extinct plants like Sicyos villosa (a cucurbit rampant in the Galápagos when Darwin visited, named by Hooker, but extinct within the next few decades) from DNA samples (and what a lot of interesting ethical and practical issues that would raise!), but the comparison of modern hybrids with their ancestral DNA is not just interesting for its own sake, but also has implications for plant care and horticulture: and the same applies, even more so, to plant pathogens.

Darwin’s specimen of Sicyos villosa, then abundant, soon extinct.

From a purely romantic point of view, however, the star of the collection assembled for us to study was the sheet showing leaves and seeds of Sequoiadendron gigantea.

The ‘Wellingtonia’ sheet: note the red ‘type specimen’ bands and the pocket containing seeds.

Seedlings, dried material and seeds of this great Californian tree were brought back by William Lobb in 1853; Lindley named it Wellingtonia gigantea, in an unfortunate snub to the American botanist who was planning to call it Washingtonia, but who couldn’t get his taxonomic specimens together fast enough. The sheet in the herbarium includes some seeds: the two majestic trees in the Botanic Garden are believed to have come in 1855 from the Veitch nursery, for which Lobb was collecting, and are from the same batch as the dried material. What a wonderful historical conjunction!

Caroline