Mackay, James Townsend (1775–1862), botanist, was born 29 January 1775 in Kirkcaldy, Fife, Scotland. His parents may have been Hugh McKay and Margaret (née Mitchel). He was educated at the local parish school and subsequently trained as a gardener, holding several posts before leaving for Ireland in 1802. Upon his arrival in Dublin he was appointed assistant to the professor of botany at TCD (1804–6), teaching botany to medical students. During 1804–5 he travelled throughout the west of Ireland exploring native flora, and publishing a catalogue of the rare plants of Ireland in the Transactions of the Dublin Society, v (1806), 121–89. Over the next twenty years he pursued his interest in native Irish plants, continuing his observations and collections during expeditions to all parts of Ireland. This culminated in the publication of an expanded catalogue published in the Transactions of the Royal Irish Academy, xiv (1824), 103–98, as a ‘Catalogue of the indigenous plants of Ireland’, a study that formed the basis of his Flora Hibernica (1836). This landmark publication, though not the first of its kind, consisted of some 600 pages, and was the first comprehensive publication about the Irish flora. Although he was credited on the title page as the sole author, the work was, in fact, a collaborative effort, with significant contributions from Dr Thomas Taylor (qv) and William Henry Harvey (qv). A total of 750 copies were printed, though only 300 were initially sold and a second edition was never published.
In 1806 the university leased eight acres of land in Ballsbridge, Dublin, then outside the city boundary. Three acres of this were taken for a botanical garden and enclosed within a high wall. Mackay was appointed curator having sole charge of the botanic garden, and was not under the direction of the professor of botany. The situation led to some friction between Mackay and the professor of botany, George J. Allman (qv), owing to his practice of holding botany classes in the garden for the general public. He remained curator until his death. An industrious and talented gardener, Mackay was responsible for laying out and stocking the garden. He established a notable plant collection, which by the 1820s was seen as surpassing that of the larger Glasnevin gardens; it became well known both in Ireland and abroad. Two of his assistants, David Moore (qv) and Charles Moore (qv), were deeply influenced by his teachings and went on to become directors of Glasnevin botanic gardens, Dublin, and Sydney botanic gardens, Australia, respectively.
He was rewarded for his unique contribution to Irish botany with a honorary doctorate from the University of Dublin (1850). The genus of seaweeds Mackaya and a seaweed species Fucus Mackayi, as well as a species of heather Erica mackaiana, were named after him. He was attacked by paralysis in 1860 and died 25 February 1862 of bronchitis in Beggar's Bush, Dublin. He was buried in Mount Jerome cemetery, Dublin.