Born in
New York as Mary Knapp Strong, she married
Joseph Clemens, a
Methodist Episcopalian minister, in 1896. He joined the
United States Army in 1902 as a
chaplain, with the rank of captain, and served in the
Philippines, America, and then
France during the
First World War, retiring in 1918. During the period spent in the Philippines in 1905–1907, she made extensive trips through
Luzon and
Mindanao. After her husband's retirement, he became her assistant and the couple worked as a team of professional, full-time botanical collectors. Usually Clemens collected the plants while her husband dried them and prepared them for shipment. Between the First and
Second World Wars the Clemenses visited
Hebei and
Shandong provinces in
China as well as
Indo-China,
British North Borneo,
Sarawak,
Java and
Singapore. Especially notable are their visits to
Mount Kinabalu in northern Borneo in 1915, and again in 1931–1934, where they amassed the largest collections of plants ever made from that mountain. In August 1935 they went to the Mandated
Territory of New Guinea where Joseph Clemens died in January 1936 of
food poisoning from contaminated
wild boar meat. Mary Clemens continued to work in
New Guinea until December 1941 when she was compulsorily evacuated to Australia because of impending war. In Australia she was allocated some space at the
Queensland Herbarium in Brisbane, in a shed behind the main building, which she used as a base from which she continued her botanical collecting. Although the provision of facilities at the Herbarium was intended to be temporary and occasional, she settled in for the next 20 years. Living in a hostel 5 km away, she would walk to the herbarium early in the morning, and sometimes cook meals and sleep in her shed overnight, despite being ordered not to. Her strong religious faith was expressed in such ways as writing quotations from the Bible daily in her field journal, frequent hymn-singing that brought complaints from co-residents and neighbours, and payment for field-trip accommodation with scripture lessons and hymn-singing. Later in life Clemens restricted her botanical work in Australia to the state of Queensland and made field trips to
Charleville (1945), the
Jericho district (1946), the
Mackay area (1947), the
Maryborough district (1948), and to
Ingham and
Tully in North Queensland (1949). A broken hip in 1950 marked the end of extended field trips but she continued to work at the Queensland Herbarium until the early 1960s. She died peacefully on 13 April 1968, at the age of 95. ==Legacy==