American mycologist and entomologist who specialised in the parasitic fungi Laboulbeniales and Entomophthoraceae. Roland Thaxter was born in Newtonville, Massachussets, into a literary family, his father a lawyer and an authority on Robert Browning, his mother a prominent poet. Natural history was an early interest; on fishing trips with his father, he learned to identify birds and plants. From private schools in Cambridge, he went to Harvard in 1878. After graduating, he entered Harvard Medical School, but in his first year fell under the influence of the cryptogamist William Gilson Farlow, a recent appointee to the university. A Harris Fellowship enabled him to switch to botany the following year. Farlow recommended that he study entomogenous fungi because they combined his interests in entomology – he had a large collection of New England butterflies – and botany. In 1887 he published, in the Proceedings and Memoirs of the American Academy of Arts and Sciences, his first important paper, in which he described the species of Gymnosporangium and connected them with their Roestelia stages. His doctoral dissertation, which came out the following year, was entitled Entomophthoreae of the United States.

His first job after his PhD was as a mycologist at the Connecticut Agricultural Experiment Station. During his short time there, he made valuable contributions to plant patholology, by describing and determining the cause of potato common scab, the previously unknown bacterial pathogen Oospora scabies Thaxt. (= Streptomyces scabies (Thaxt.) Waksman &. Henrici), the mildew of lima beans, Phytophthora phaseoli Thaxt., of onion smut, and by producing pioneering spray work with the fungi of potatoes, grapes, and quinces.

In 1891 he returned to Harvard as assistant professor of cryptogamic botany under Farlow. Within five years he had assumed full responsibilities for the teaching of undergraduates, and in 1901 was made full professor. At Harvard, his work on parasitic fungi continued, becoming focused on the Laboulbeniales, a little-known group of entomogenous fungi. This research was published between 1896 and 1931 in five volumes of the Memoirs of the American Academy of Arts and Sciences, as "Contributions Towards a Monograph on the Laboulbeniaceae". These and more than 80 shorter papers on other groups of fungi, notably the Phycomycetes and Myxobacteriaceae, were illustrated with his accomplished pen-and-ink drawings. He was associate editor of the Botanical Gazette (1896-1904), and it was here he published most of his early and later articles on fungi other than the Laboulbeniales. In 1907 he succeeded Farlow as American editor for the British journal Annals of Botany, and continued in this capacity until his death. When Farlow died in 1919, Thaxter retired at his own request and became professor emeritus and honorary curator of the Farlow Herbarium and Library of Cryptogamic Botany. His original personal collections were deposited at the Farlow Herbarium (FH). In later life, he developed cataracts, which completely obscured his vision in one eye by 1925, and had blinded him by the time of his last illness.

Most of Thaxter's plant collecting was carried out close to home, around Cambridge or in Kittery Point, Maine, where he owned a summer home, but despite poor health and administrative duties he made several extended journeys to the West Indies and southernmost South America: to Jamaica in the winter of 1890-1891, where he collected numerous coprophilus fungi; to Florida and the major European herbaria to study and collect Laboulbeniales in his sabbatical year in 1897-1898; and to Trinidad in 1913. But by far his most interesting expedition took place during his sabbatical in 1905-1906, when he sailed to South America to accomplish a boyhood dream, inspired by Darwin's Voyage of the Beagle, to see Tierra del Fuego and Patagonia. Although he had planned a comprehensive work on Chilean fungi, he published only a short account, "Notes on Chilean Fungi", in the Botanical Gazette in December 1910. Early in his voyage, he had to change his itinerary because of a deadly outbreak of smallpox in Chile, which prevented him from landing in Valparaiso as planned. Instead he disembarked in Buenos Aires and spent six weeks in Argentina, collecting and meeting associates and colleagues, before leaving for Chile. Although he reached his destinations, his journey along the coast was plagued by poor weather and ill health, and came to an abrupt end when news reached him of his son's death in May 1906.

As well as holding memberships to the major American scientific institutions, he was President of the New England Botanical Club, the Society of Plant Morphology and Physiology, the American Mycological Society, and the American Botanical Society. He was elected to the American Academy of Arts and Sciences, the American Philosophical Society, and the National Academy of Sciences, and honoured as a foreign member of the Russian Mycological Society, the Linnean Society of London and of Lyons, the Royal Botanical Society of Belgium, the Royal Academies of Sweden and Denmark, the Botanical Society of Edinburgh, the Academy of Science of the Institute of France, the British Mycological Society, and the Deutsche Botanisch Gesellschaft. The French Academy conferred on him the Prix Desmaziers for his work on Laboulbeniales. The genus Thaxteria Giard was named after him, though it is now reduced to synonmy under Laboulbenia Mont. and C.P. Robin. Several species of fungi and lichen are named in his honour.

Sources:
G.P. Clinton, 1935, "Biographical Memoir of Roland Thaxter, 1858-1932", National Academy of Sciences, 17: 55-68
1964, Dictionary of American Biography, 9(1): 398-399.