Background
Correns was born on September 19, 1864, in Munich, Germany, the only child of Erich Correns, a painter and member of the Bavarian Academy of Art. His mother was of Swiss extraction. Orphaned at 17, he was raised by an aunt in Switzerland.
Carl Correns in the 1910's.
Geschwister-Scholl-Platz 1, 80539 München, Germany
Correns graduated from the University of Munich in 1889.
Geschwister-Scholl-Platz, 72074 Tübingen, Germany
Correns took his Habilitation from Tübingen University in 1892.
Geschwister-Scholl-Platz 1, 80539 München, Germany
Correns graduated from the University of Munich in 1889.
Geschwister-Scholl-Platz, 72074 Tübingen, Germany
Correns took his Habilitation from Tübingen University in 1892.
Correns was born on September 19, 1864, in Munich, Germany, the only child of Erich Correns, a painter and member of the Bavarian Academy of Art. His mother was of Swiss extraction. Orphaned at 17, he was raised by an aunt in Switzerland.
Correns left Munich for St. Gall, Switzerland, where tuberculosis interrupted his schooling and prevented him from obtaining his Abitur until 1885. Four years later he graduated from the University of Munich; and after two semesters in Berlin under Schwendener he moved to Tübingen, where he took his Habilitation in 1892.
After ten years as Privatdozent, Correns was appointed assistant professor at Münster in 1909. When the Kaiser-Wilhelm Institut für Biologie was built in Berlin (Dahlem) in 1913, Correns became its first director. There he remained for the rest of his life, and his unpublished manuscripts were preserved there until their destruction during the bombing of Berlin in 1945.
Correns won fame as a rediscoverer of Mendel’s laws. Whereas de Vries and Tschermak, who rediscovered Mendel’s work simultaneously, were more concerned with mutation and practical plant breeding, respectively, Correns concentrated on the xenia question: Does foreign pollen have a direct influence on the characteristics of the fruit and seed? This subject was but one of many botanical problems occupying his attention in the 1890’s.
The many-sided character of Correns’ early research indicates the indecision of one trained in the shadow of giants, Naegeli, and Darwin in particular. His work represents a re-investigation, extension, or criticism of previous work. He studied heterostylism in the primrose because of disbelief in Darwin’s and G. G. F. Delpino’s views on adaptation to outbreeding. Following his mentor Naegeli, he denied that the large and small pollen grains are an adaptation to long-and short-styled flowers because the culture of the grains in a sugar solution failed to yield the required difference in length. In his study of Drosera rotundifolia Correns also questioned Darwin’s conclusions on the effect of increasing temperature on the sensitivity of leaves.
In 1894 Correns took up the xenia question, studying it by crossing varieties of Zea, Pisum, Phaseolus, Lilium, and Matthiola. Three years later he concluded that the xenia effect in maize is due either to an enzymatic effect of the embryo on the endosperm tissue or to a genuine hybridization between the secondary embryo sac nucleus and a generative nucleus of the pollen tube. Correns did not learn of this until late in 1899. Meanwhile, his pea crosses had reached the fourth generation. His scoring of maize progeny had given him complicated numerical results, but his pea progeny gave him simple ratios; and in October 1899 Correns arrived at the correct explanation. A few weeks later he read Mendel’s paper, of which he had learned from a rereading of W. O. Focke’s Die Pflanzenmischlinge. On 21 April Correns was stimulated to write up his own account by the receipt of de Vries’s paper “Sur la loi de disjonction des hybrides,” The German Botanical Society received it on 24 April.
Of the three rediscoverers of Mendel’s laws, Correns showed the deepest understanding and the most subtle approach. The remainder of his career was devoted to an investigation of the precise extent of the validity of these laws. He was the first to correlate Mendelian segregation with reduction division and to show that Mendelian segregation does not require the dominant-recessive relationship, and that characters, even those due to different physiological agents, can be “coupled” or “conjugated” in heredity and are therefore unable to show independent assortment (Mendel’s second law). In 1902 he found in maize a case of coupling between self-sterility and blue coloration of the aleurone layer; here too he found the first evidence of differential fertilization between different gametes. This finding was later supported by his discovery of competition between male and female pollen grains, the former having a selective advantage over the latter. In the same year as Walter Sutton (1902), Correns produced a chromosome theory of heredity that allowed for exchange of genes between homologous chromosomes but not for the block transfer type later advanced by Morgan. On Correns’ scheme, therefore, mapping of the genes from crossover values would be impossible.
In 1903 Correns predicted that sex is inherited in a Mendelian fashion, and in 1907 he proved it by his classic experiments with Bryonia. Two years later he obtained the first proof of cytoplasmic inheritance in plants simultaneously and independently of Erwin Baur. From that year until his death Correns studied plant variegation in all its forms, and by crossbreeding experiments he distinguished between nuclear, Mendelian and extranuclear, non-Mendelian inheritance of variegation. Whereas Baur proposed that the plastids themselves are the genetic determinants (Plastom theory) in cases of extranuclear heredity, Correns favored the nonparticulate cytoplasm of the cell considered as a whole (non-Plastom theory). For Baur the change from green to white cells was due to plastid mutation; for Correns in 1909 it was a case of disease, but in 1922 he postulated a labile state of the cytoplasm that could cause the plastids to develop either into normal (green) bodies or into diseased (white) bodies. Although the Plastom theory is now widely accepted both for biparental and for monoparental cytoplasmic inheritance, in Correns’ time the failure to detect cell with white and green plastids mixed and to see a clear boundary between mutant and normal tissues seemed to furnish valid objections to Baur’s theory.
Correns is notable primarily for his independent discovery of the principles of heredity. His research was the first to correlate Mendelian segregation with the reduction division of chromosomes, and he illustrated several important examples of deviations in Mendelian inheritance, such as natural variations in the dominant-recessive heredity pattern.
Correns was unimpressive as a lecturer. He always published in German and rarely traveled. Unlike de Vries, who forced the facts of heredity into an oversimplified Mendelian scheme, Correns stressed the complexities and the exceptions to that scheme. He was a hard worker, dedicated to science rather than to success, and willingly gave Mendel full credit, later publishing Mendel’s famous letters to Naegeli. He deserves the first place in the history of the rediscovery period of Mendelian genetics.
Correns married Elizabeth Widmer in 1892. She was Karl von Nageli's niece.
