American botanist. Herbert Louis Mason was born at Fond du Lac, Wisconsin, and graduated from Stanford University in 1922, having served from 1917 to 1919 in the United States Medical Corps, stationed in Beaune, France. He received his master's degree and PhD in botany from the University of California (in 1923 and 1932 respectively), and taught there from 1932 until his retirement in 1963. He was appointed professor in 1941 and curated the university herbarium from 1935-1941. Mason made numerous collecting trips, extensively in the United States and notably as palaeobotanist with the Carnegie Institution expedition to the Bering Sea and the Arctic Ocean in 1932. He specialised in the Polemoniaceae and in Pleistocene flora of western North America, but also travelled to Central and South America. In 1949 and 1950, he joined A.H. Miller and R.A. Stirton in an expedition to the Magdalena Basin of Colombia, sponsored by the Associates in Tropical Biogeography; their objective was to study periodic phenomena under tropical conditions without marked seasons. Mason and his graduate students were then commissioned to make a botanical survey of California wetlands, which resulted in his best known work, A Flora of the Marshes of California (1957).