Darwin’s Botanists: Asa Gray

Holotype of Abutilon parvulum collected by Charles Wright for Asa Gray, Harvard University Herbaria.

This last post in the series (1,2,3) on Charles Darwin and the botanists who supported his work deals with an American, Asa Gray (1810-1888).  He received his medical degree at Yale University, but like Joseph Dalton Hooker (see last post), had little interest in practicing and a great desire to learn more about plants.  He taught at Utica College in central New York State for a short time, while collecting in the area and creating exsiccatae of grasses and sedges (Gray, 1834).  He was eventually drawn to work with John Torrey, a botanist who was teaching botany part time at Columbia College in New York City while also teaching chemistry at Princeton University.  Torrey was impressed with Gray’s herbarium and paid for him to collect in New York and New Jersey.  After this, Gray moved in with Torrey’s family and organized his herbarium.  This gave Gray an opportunity to see many more species than he had encountered up to this time.  He remained with the Torreys for two years until he was offered a position as professor of botany at the newly formed University of Michigan.

In preparing for this post, Gray traveled to Europe to purchase books and equipment, and also to consult much richer herbaria than those available in the US, even for American species.  Visiting Glasgow, Gray stayed with William Jackson Hooker for three weeks examining his North American plants, including many collected by Thomas Nuttall.  Gray discovered that most of the specimens were from northern areas of North America, with the south and west still relatively unexplored.  John Lindley of the Royal Horticultural Society let him take portions of the specimens said to have been collected by Thomas Walter in the Carolinas in the 1700s, something that would be unheard of today (Dupree, 1959, p. 80).  Having gathered a wealth of information, Gray returned home to find that the University of Michigan was still not ready to have him begin work.  When offered a similar position at Harvard University, with the additional responsibility for its botanical garden, he moved to Cambridge and remained there for the rest of his life. 

Gray continued to work with Torrey on the deluge of specimens coming in from US-sponsored expeditions and surveys, including the Wilkes Expedition’s 50,000 plant specimens.  This necessitated another trip to Europe to consult herbaria in Britain and France with their superior holdings of North American plants.  Torrey and Gray did much to eventually alleviate this problem by creating large collections at their home institutions of Columbia and Harvard, while the Wilkes specimens became the nucleus of the US Herbarium at the Smithsonian Institution.  Like Joseph Dalton Hooker (see last post), Torrey and Gray became “imperial” botanists, in that they attempted to retain control over collectors and discourage them from describing species themselves.  They claimed that those gathering specimens didn’t have the knowledge, reference collections, or literature to do the job. 

In 1843, US Navy Commodore Matthew C. Perry signed a treaty with Japan that began to open the country to trade.  While Perry had not wanted a natural history collector on the expedition, two Americans associated with the mission, one a friend of Gray’s, did make a small plant collection and sent it to Cambridge.  What struck Gray about these plants, as well as some other Japanese species he had encountered, was how similar they were to those of the northeast US.  When he had examined a broad enough selection, he arranged them in a table and found that of 580 Japanese species, fewer were in western North America than in Europe, and far more were in eastern North America than in either of the other areas.  Considering this odd result, he posited that the plants in these two areas had a common ancestry.  Due to fluctuating climates, which remained most similar in eastern North America and Japan, the species were better able to survive in these regions.  This was a significant piece of evidence for evolution and Charles Darwin was very pleased with it.

Gray and Darwin began their correspondence in 1855.  Darwin appreciated Gray’s acceptance of species change, though he was less pleased that Gray held that creation still had a role in life on earth.  Gray presented this view most fully in an article in the Atlantic Monthly in 1861, “Natural Selection Not Inconsistent with Natural Theology.”  While disagreeing with it, Darwin did see it as a way to lure more people into the evolutionary fold and arranged for it to be reprinted in Britain (Dupree, 1959, p. 155).  Like Hooker, Gray also provided Darwin with much botanical information for his post-Origin plant studies.  They both experimented in their gardens, and Gray could provide seeds and cuttings of American plants.  In his own work, Gray was stymied by the amount of administrative work he was required to do at Harvard without adequate assistance.  Until he retired, he was the only professor of botany, and the University had never created an infrastructure for botanical research.  Gray managed to set the stage for this at his retirement by donating his herbarium of 220,000 specimens and his library of over 2,200 books to the University and managing the hiring of a staff to at last create a department of botany.   


Dupree, A. H. (1959). Asa Gray: American Botanist, Friend of Darwin. Cambridge, MA: Harvard University Press.

Gray, A. (1834). North American Gramineae and Cyperaceae (Vols. 1–2). New York, NY: Post.

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