Marie Charlotte Carmichael Stopes (15 October 1880 - 2 October 1958) was a British author, palaeobotanist and campaigner for eugenics and women's rights. She made significant contributions to plant palaeontology and coal classification, and was the first female academic on the faculty of the University of Manchester. With her second husband, Humphrey Verdon Roe, Stopes founded the first birth control clinic in Britain. Stopes edited the newsletter Birth Control News, which gave explicit practical advice.

During Stopes's time at Manchester, she studied coal and coal balls and researched the collection of Glossopteris (Permian seed ferns). This was an attempt to prove the theory of Eduard Suess concerning the existence of Gondwana or Pangaea. A chance meeting with Antarctic explorer Robert Falcon Scott during one of his fund-raising lectures in 1904 brought a possibility of proving Suess's theory. Stopes's passion to prove Suess's theory led her to discuss the possibility of joining Scott's next expedition to Antarctica. She did not join the expedition, but Scott promised to bring back samples of fossils to provide evidence for the theory. Scott died during the 1912 Terra Nova Expedition, but fossils of plants from the Queen Maud Mountains found near Scott's and his companions' bodies provided this evidence. In 1907, Stopes went to Japan on a scientific mission. She spent eighteen months at the Imperial University, Tokyo and explored coal mines on Hokkaido for fossilised plants. She published her Japanese experiences as a diary, called "Journal from Japan: a daily record of life as seen by a scientist", in 1910. In 1910, the Geological Survey of Canada commissioned Stopes to determine the age of the Fern Ledges, a geological structure at Saint John, New Brunswick. It is part of the Early Pennsylvanian epoch Lancaster Formation. Canadian scholars were divided between dating it to the Devonian period or to the Pennsylvanian/Upper Carboniferous period. Stopes arrived in North America before Christmas to start her research. On 29 December, she met the Canadian researcher Reginald Ruggles Gates in St. Louis, Missouri; they became engaged two days later. Starting her work on the Fern Ledges in earnest in February 1911, she did geological field work and researched at geological collections in museums, and shipped specimens to England for further investigation. The couple married in March and returned to England on 1 April that year. Stopes continued her research. In mid-1912 she delivered her results, finding for the Pennsylvanian period of the Carboniferous. The Government of Canada published her results in 1914. Later the same year, her marriage to Gates was annulled.[1] During the First World War, Stopes was engaged in studies of coal for the British government, which culminated in the writing of "Monograph on the constitution of coal" with R.V. Wheeler in 1918. The success of Stopes' work on marriage issues and birth control led her to reduce her scholarly work; her last scientific publications were in 1935. According to W. G. Chaloner (2005), "between 1903 and 1935 she published a series of palaeobotanical papers that placed her among the leading half-dozen British palaeobotanists of her time". Stopes made major contributions to knowledge of the earliest angiosperms, the formation of coal balls and the nature of coal macerals. The classification scheme and terminology she devised for coal are still being used. Stopes also wrote a popular book on palaeobotany, "Ancient Plants" (1910; Blackie, London), in what was called a successful pioneering effort to introduce the subject to non-scientists.

Using a quote from the above article, answer the following question: What research did Stopes do in Japan?
She spent eighteen months at the Imperial University, Tokyo and explored coal mines on Hokkaido for fossilised plants.