2. In 1877 he published a paper on the mechanical causes of cell stretching in plants
in which he developed his method of comparing osmotic pressures by plasmolysis.
He worked out the conception of isotonic
coefficients, and was able to show by 1884 that the osmotic pressure in
the plant cell was determined by the number of molecules in solution
and not by the weight of solute.
He became one of the pioneers of the then unnamed science of genetics.
3. First expression of some of the fundamental ideas of modern genetics—that the material basis of
heredity is to be found in the nucleus of the cell in the units derived from father and mother
respectively, units which de Vries named “ Pangenen.”
De Vries joined with Bateson in denying the smooth flow of change by insensible steps which Darwin
had postulated as the procedure by which new varieties and eventually new species arise.
All the later association of the Mendelian generalizations with the behaviour of the chromosomes in
meiosis and the gradual establishment of a definite rate of mutation in many organisms, a rate which
can be speeded up by agencies like X-ray treatment, makedeVries’s mutations a permanent
contribution to knowledge
4. Carl Erich Correns (September 10, 1864 – February 14, 1933) was a German
botanist and geneticist, who is notable primarily for his independent discovery of
the principles of heredity, and for his rediscovery of Gregor Mendel’s earlier paper
on that subject, which he achieved simultaneously but independent of the botanists
Erich Tschermak von Seysenegg and Hugo de Vries
Carl Correns conducted much of the foundational work for the field of genetics at
the turn of the 19th century. He rediscovered and independently verified the work of
Mendel in a separate model organism.
5. Correns published his first paper on January 25, 1900, which cited both Charles
Darwin and Mendel, though without fully recognising the relevance of genetics to
Darwin’s ideas. In Correns’ paper, “G.Mendel’s Law Concerning the Behavior of the
Progeny of Racial Hybrids”, he restated Mendel’s results and his law of segregation
and law of independent assortment
6. He also discovered cytoplasmic inheritance, an important extension of Mendel’s
theories, which demonstrated the existence of extra-chromosomal factors on
phenotype. Most of Correns’ work went unpublished however, and was destroyed in
the Berlin bombings of 1945.
After rediscovering Mendel’s laws of heredity, which apply to chromosomal
inheritance, he undertook experiments with the four o’clock (Mirabilis jalapa) to
investigate apparent counterexamples to Mendel’s laws in the heredity of
variegated (green and white mottled) leaf color.
7. The Mendelian ratios were not quite so consistent and Tschermak was much more
cautious in his embrace of Mendel.
He wrote up his results first as his Habilitationsschrift, the postdoctoral thesis
required for teaching at the university level, which he handed in in January 1900.
While he was waiting for it to be accepted, the other rediscovery papers (two by de
Vries and one by Carl Correns) appeared, and he rushed to publish his own account
and crossing results.
8. Tschermak’s publication was not a focused explication of Mendel’s laws, but his
entire ninety-page thesis. It was framed as a test of Darwin’s ideas about the
effects of inbreeding the original purpose of the Ghent experiments- and the main
research question was whether a natural self-pollinator like the pea was immune
to inbreeding depression or could be made more vigorous by outcrossing. The
Mendel-style crosses and backcrosses seem to have been an afterthought, inspired
by some of the literature on hybridization, possibly including Mendel. As
Tschermak wrote in 1900
