Carl Erich Correns was a German botanist and geneticist notable primarily for his independent discovery of the principles of heredity, which he achieved simultaneously but independently of the botanist Hugo de Vries, and for his acknowledgment of Gregor Mendel's earlier paper on that subject.
Carl Correns in the 1910s
Carl Correns
Hugo Marie de Vries was a Dutch botanist and one of the first geneticists. He is known chiefly for suggesting the concept of genes, rediscovering the laws of heredity in the 1890s while apparently unaware of Gregor Mendel's work, for introducing the term "mutation", and for developing a mutation theory of evolution.
de Vries, c. 1907
Hugo de Vries in the 1890s
Hugo de Vries at his retirement (Thérèse Schwartze, 1918)