HUGO VON

See also:

• HUGO VON MOHL (1805–1872)
• MOHL, JULIUS VON (1800–1876)

MOHL (1805–1872)  , German botanist, was born at Stuttgart on the 8th of April 18o5 . He was a son of the Wurttemberg statesman Benjamin Ferdinand von Mohl (1766–1845), the family being connected on both sides with the higher class of state officials of Wurttemberg . While a pupil at the gymnasium he pursued botany and mineralogy in his leisure time, till in 1823 he entered the university of Tubingen . After graduating with distinction in medicine he went to Munich, where he met a distinguished circle of botanists, and found ample material for research . This seems to have determined his career as a botanist, and he started in 1828 those anatomical investigations which continued till his death . In 1832 he was appointed professor of botany in Tubingen, a post which he never left . Unmarried, his pleasures were in his laboratory and library, and in perfecting optical apparatus and microscopic preparations, for which he showed extraordinary manual skill . He was largely a self-taught botanist from boyhood, and, little influenced in his opinions even by his teachers, preserved always his independence of view on scientific questions . He received many honours during his lifetime, and was elected foreign fellow of the Royal Society in 1868 . Von Mohl's writings cover a period of forty-four years; the most notable of them were republished in 1845 in a volume entitled Vermischte Schriften- (For lists of his works see Botanische Zeitung, 1872, p . 576, and Royal Soc . Catalogue, 187o, vol. iv.) They dealt with a variety of subjects, but chiefly with the structure of the higher forms, including both rough anatomy and minute histology .

The word

protoplasm " was his suggestion; the nucleus had already been recognized by R . Brown and others; but von Mohl showed in 1844 that the protoplasm is the source of those movements which at that time excited so much attention . He recognized under the name of " primordial utricle " the protoplasmic lining of the vacuolated cell, and first described the behaviour of the protoplasm in cell-division . These and other observations led to the overthrow of J . M . Schleiden's theory of origin of cells by free-cell-formation . His contributions to knowledge of the cell-wall were no less remarkable; he held the view now generally adopted of growth of cell-wall by apposition . He first explained the true nature of pits, and showed the cellular origin of vessels and of fibrous cells; he was, in fact, the true founder of the cell theory . Clearly the author of such researches was the man to collect into one volume the theory of cell-formation, and this he did in his treatise Die vegetabilische Zelle (1851), a short work translated into English (Ray Society, 1852) . Von Mohl's early investigations on the structure of palms, of cycads, and of tree-ferns permanently laid the foundation of all later knowledge of this subject: so also his work on Isoetes (184o) . His later anatomical work was chiefly on the stems of dicotyledons and gymnosperms; in his observations on cork and bark he first explained the formation and origin of different types of bark, and corrected errors relating to lenticels . Following on his early demonstration of the origin of stomata (1838), he wrote a classical paper on their opening and closing (1850) .

In 1843 he started in

conjunction with F . Schlechtendal the weekly Botanische Zeitung, which he jointly edited till his death . He was never a great writer of comprehensive works; no text-book exists in his name, and it would indeed appear from his withdrawal from co-operation in W . F . B . Hofmeister's Handbuch that he had a distaste for such efforts . In his latter years his productive activity fell off, doubtless through failing health, and he died suddenly at Tubingen on the 1st of April 1872 . See Sachs, History of Botany, p . 292, &c.; De Bary, Botanische Zeitung (1872), p . 561; Proc . Roy . Soc., xxiii .

1; Allgemeine Deutsche Biographie, xxii . 55 . (F . 0 .