Erich von Tschermak
Von Tschermak is one of three men – the others were Hugo de Vries and Carl Correns – who were credited with independently rediscovering Gregor Mendel's work on genetics. Von Tschermak published his findings in June 1900.
By a quirk of history, Correns had been a student of Karl Wilhelm von Nägeli. Nageli was a renowned botanist with whom Mendel corresponded about his work with peas, but who failed to understand how significant Mendel's work was. Von Tschermak was a grandson of a man who taught Mendel botany during his student days in Vienna.
Though von Tschermak was originally also credited with the rediscovery, this is no longer generally accepted, because he did not understand Mendel's laws.