Darwin’s Gift: herbarium specimens for Henslow
Charles Darwin was the Cambridge student who supplied the highest number of plants for Professor Henslow’s herbarium. His first addition was from Wales in August 1831, but he began serious collecting during his world trip on HMS Beagle
Darwin gathered plants every year between 1832 (182 collections) and 1835 (223) and altogether sent Henslow about 2,700 from the whole voyage - from the mainland of South America, the Cape Verde Islands in the Atlantic Ocean, the Galapagos Archipelago in the Pacific, and Keeling Island in the East Indies.
Darwin’s plants were a gift for his Professor and so he collected in the same way as Henslow. Darwin usually collected two or more plants at each location, up to an astonishing maximum of 31 from a single population in Chile. In addition, Darwin made a particular point of collecting all the plants he found in flower on the Galapagos Archipelago, since the flowers of these oceanic islands had not been studied previously and Henslow was particularly interested in geographical distribution.
Darwin made precise notes of the location of each collection he made during the voyage, and occasionally added other information. He followed the instructions given to him by Henslow in a letter, and so recorded dates only to the month of collection.
When he received the plants in Cambridge, Henslow “collated” and mounted the samples on to about 950 herbarium sheets, itself a very large task. He had sheets printed with “Mus Henslow” (Museum of Henslow) in the top corner and also brief printed locations - South America, Patagonia or Galapagos Islands – and the name “C. Darwin”. Henslow then hand-wrote the date of the collection and any brief notes that Darwin had supplied.
Using this precious material, Henslow published a short paper describing two new species of Opuntia
from the Galapagos in 1837 and followed this with an account of the native plants of Keeling Island in 1838. The task of identifying the species in this magnificent gift, however, greatly exceeded Henslow’s taxonomic knowledge of the world’s flora. So Darwin’s Galapagos plants were later dissected, drawn and described by his friend Joseph Hooker of the Royal Botanic Gardens, Kew, and were finally published in 1847.Handling plants, carrying out instructions
Darwin sent back the first box of Beagle
specimens from Brazil to Henslow late in 1832. After having examined the contents, Henslow offered his advice in a letter of January 1833 on how Darwin could collect geological and botanical specimens more effectively.
About plants, Henslow wrote,
“Avoid collecting scraps. Make the specimens as perfect as you can, root, flowers & leaves and you can’t do wrong. In large ferns and leaves fold them back upon themselves on one side of the specimen & they will get into a proper sized paper.”
Henslow accompanies this with a sketch of a leaf indicating, “this side is folded back at the edges.”
Two fern fronds in this first box had been inexpertly dried by Darwin to give a tangled mass. It is tempting to think that they occasioned the instructions about collecting in Henslow’s correspondence. Certainly, ferns along with the other plants were much better prepared from then on. For example Darwin’s samples of Pleopeltis aurea
(now Phlebodium areolatum
) from James Island in the Galapagos in October 1835 have the pinnae folded over, as instructed by his Professor. Further reading:
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Porter, D. 1986. Charles Darwin's vascular plant specimens from the voyage of HMS Beagle. Botanical Journal of the Linnean Society
93, 1: 1-172