SCHLEIDEN, Matthias (1801-1881), was born at Hamburg in 1804. He studied law at Heidelberg and practised as advocate in Hamburg till 1831, but not succeeding he studied botany and medicine at Göttingen and Berlin, and graduated in Jena in 1839, where he afterwards became professor of botany (1846-50). In 1863 he was called to Dorpat, but resigned the following year and returned to Germany, where he lived as a private teacher. He died at Frankfurt in 1881. His title to remembrance is twofold. Uniting the labours of two centuries of workers in vegetable histology, from Malpighi and Grew to Mirbel and Robert Brown, he proved that a nucleated cell is the only original constituent of the plant embryo, and that the development of all vegetable tissues must be referred to such cells, thus preparing the way for the epoch-making cell theory of Schwann; and his Principles of Scientific Botany, which went through several editions (1842—50), did much to shake the tyranny of the purely systematic Linnean school, whose accumulations he was accustomed irreverently to describe as “hay.” Despite a certain inability to criticize and verify his own hypotheses, he gave, both by his speculative activity and by the introduction of improved technical methods, so vivid an impulse to the younger botanists of his time as to have earned from De Bary the title of reformer of scientific botany. His botanical labours practically ceased after 1850, when he entered on various philosophical and historical studies. See Schwann.