Hugo De Vries
Hugo Marie de Vries (Feb 16 1848, Haarlem - May 21 1935, Lunteren) 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.

# Early life
De Vries was born in 1848, the oldest son of Gerrit de Vries (1818-1900), a lawyer in Haarlem, and Maria Everardina Reuvens (1823-1914), daughter of a professor in archaeology at Leiden University. His father became a member of the Dutch Council of State in 1862 and moved his family over to The Hague. From an early age Hugo showed much interest in botany, winning several prizes for his herbariums while attending gymnasium in Haarlem and The Hague.
In 1866 he enrolled at the Leiden University to major in botany. He enthusiastically 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 was also deeply impressed by Charles Darwin's evolution theory, despite Suringar's skepticism. 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.

# Early career
After a short period of teaching, De Vries left in September 1870 to take classes in chemistry and physics at the Heidelberg University and work in the laboratory of Wilhelm Hofmeister. In the second semester of that school year he joined the lab. of the esteemed Julius Sachs in Wurzburg to study plant growth. From September 1871 until 1875 he taught botany, zoology, and geology at schools in Amsterdam. During each vacation he returned to the lab in Heidelberg to continue his research.
In 1875 the Prussian Ministry of Agriculture offered De Vries a position as professor at the still to be constructed Landwirtschaftliche Hochschule ("Royal Agricultural College") in Berlin. In anticipation, he moved back to Wurzburg, where he studied agricultural crops and collaborated with Sachs. By 1877, Berlin's College was still only a plan, and he briefly took up a position teaching at the University of Halle-Wittenberg. The same he year he was offered a position as lecturer in plant physiology at the newly founded University of Amsterdam. He was made adjunct professor in 1878 and full professor on his birthday in 1881, partly to keep him from moving to the Berlin College, which finally opened that year.
De Vries was also professor and director of Amsterdam's Botanical Institute and Garden from 1885 to 1918.

# Definition of the gene
In 1889, De Vries published his book Intracellular Pangenesis , in which, based on a modified version of Charles Darwin's theory of Pangenesis of 1868, he postulated that different characters have different hereditary carriers. He specifically postulated that inheritance of specific traits in organisms comes in particles. He called these units pangenes, a term 20 years later to be shortened to genes by Wilhelm Johannsen.

# Rediscovery of genetics
To support his theory of pangenes, which was not widely noticed at the time, De Vries conducted a series of experiments hybridising varieties of plants in the 1890s and he discovered new forms among a display of the evening primrose (Oenothera lamarckiana) growing wild in a waste meadow. His experiments led to the same conclusions as Mendel and confirmed his hypothesis: that inheritance of specific traits in organisms comes in particles.
He also speculated that genes could cross the species barrier, with the same gene being responsible for hairiness in two different species of flower. Although generally true in a sense (orthologous genes, inherited from a common ancestor of both species, tend to stay responsible for similar phenotypes), De Vries meant a physical cross between species. This actually also happens, though very rarely in higher organisms (see horizontal gene transfer).
In the late 1890s, de Vries became aware of Mendel's obscure paper of forty years earlier, and he altered some of his terminology to match. When he published the results of his experiments in the French journal Comtes Rendus de l'Academie des Sciences in 1900, he neglected to mention Mendel's work, but after criticism by Carl Correns , he conceded Mendel's priority.
Correns and Erich von Tschermak now share credits for the rediscovery of Mendels laws. It may be noteworthy that Correns was a student of Nageli, a renowned botanist with whom Mendel corresponded about his work with peas but who failed to understand how significant Mendel's work was. Quirkily, Tschermak was a grandson of a man who taught Mendel botany during his student days in Vienna.

# Mutation theory
De Vries developed his own theory of evolution known as the mutation theory (a form of saltationism), which posited that instead of Darwinian gradualism, new species could arise in single jumps. However it was later discovered that much of what De Vries was describing in terms of his evidence had nothing to do with what is now known as genetic mutation. In his time, though, De Vries's theory was one of the chief contenders for the explanation of how evolution worked, until the modern evolutionary synthesis became the dominant model in the 1930s.

# Honors and retirement
In May 1905, De Vries was elected Foreign Member of the Royal Society. He was awarded the Darwin Medal in 1906 and the Linnean Medal in 1929.
He retired in 1918 from the University of Amsterdam and withdrew to his estate "De Boeckhorst" in Lunteren where he had large experimental gardens. He continued his studies with new forms until his death in 1935.

# Books
His best known works are:
- Intracellular Pangenesis (1889)
- The Mutation Theory German edition (1900-03) English edition (1910-11)
- Species and Varieties: Their Origin by Mutation (1905)
- Plant Breeding (1907) German translation (1908)