Hugo Marie de Vries (1848-1935) was a Dutch botanist and one of the first geneticists. He is known chiefly for suggesting the concept of genes, rediscovering Gregor Mendel's laws of heredity in the 1890s, and for developing a mutation theory of evolution. In 1866 he enrolled at the Leiden University to major in botany. He took part in W. F.R. Suringar's classes and excursions, but was mostly drawn to the experimental botany outlined in Julius Sachs' 'Lehrbuch der Botanik' from 1868. He wrote a dissertation on the effect of heat on plant roots, including several statements by Darwin to provoke his professor, and graduated in 1870. After a short period of teaching, de Vries left in 1870 to take classes in chemistry and physics at the Heidelberg University and work in the laboratory of Wilhelm Hofmeister. In 1875 the Prussian Ministry of Agriculture offered de Vries a position as professor at the still to be constructed Landwirtschaftliche Hochschule in Berlin. By 1877, Berlin's College was still only a plan, and he briefly took up a position teaching at the University of Halle-Wittenberg.