Paul Runar Collander (1 May 1894 Vyborg – 25 May 1973 Helsinki) was a Finnish botanist. He was an adjunct professor of plant physiology at the University of Helsinki from 1935 to 1939, and professor of botany from 1939 to 1961.^[1] He gained international acclaim for his research on the effect of molecular size and solubility ratios on the ability of substances to penetrate the cell membrane.^[2] He presented the "lipoid filter theory" of permeability and further developed it. Collander also wrote several works on the history of botany.^[1]

• Collander, Runar (1965). The History of Botany in Finland, 1828–1918. The History of Learning and Science in Finland, 1828–1918. Helsinki: Societas Scientiarum Fennica [Finnish Society of Sciences and Letters]. pp. 1–159.