Correns, the only child of the painter Erich Correns, was born in Munich, Germany. He studied at Tübingen University, where he began his research on the effect of foreign pollen in changing the visible characters of the endosperm (nutritive tissue surrounding the plant embryo). In some of his crossing experiments Correns used varieties of pea plants, following the ratios of certain characters in the progeny of these. After four generations he had gathered sufficient evidence to formulate the basic laws of inheritance. Not until he searched for relevant literature did he find that Gregor Mendel had reached the same conclusion a generation earlier. Correns' own work, published in 1900, thus only provided further proof for Mendel's theories. His later research concentrated on establishing how widely Mendel's laws could be applied. Using variegated plants he obtained, in 1909, the first conclusive evidence for cytoplasmic, or non-Mendelian, inheritance, in which certain features of the offspring are determined by the cytoplasm of the egg cell. Other contributions to plant genetics include his proposal that genes must be physically linked to explain why some characters are always inherited together. Correns was also the first to relate Mendelian segregation (the separation of paired genes, or alleles) to meiosis and the first to obtain evidence for differential fertilization between gametes. From 1914 until his death he was director of the Kaiser Wilhelm Institute for Biology in Berlin.