transverse bands on false spiral vessels (scalariform ducts) and
the pits of dotted vessels are formed on the walls of membranous
fibre-tubes; in like manner he derives true spiral vessels from
long thin-walled cells, on whose inner surface the spiral band
is formed, and well compares the members of young spiral
vessels with the elaters of the Jungermannieae. Here then we
find the first more definite indications of a theory of growth in
thickness of cell-walls, which, like the theory of the origin of
vessels from rows of cells, was afterwards developed by von Mohl
and laid on better foundations. At the close of the essay the
histology of the Cryptogams, Monocotyledons and Dicotyledons
is compared, and the subject is better and more perspicuously
handled than in the corresponding chapters of his competitors.
Though Treviranus' account of vegetable tissues was on the whole weak as far as concerns the history of development, yet Mirbel[1] recognised in him the most dangerous opponent of his own theory, and addressed a public letter to him and not to his other German antagonists, Sprengel, Link and Rudolphi, in defence of the views he had formerly expressed. This letter is the first part of a larger work which appeared in 1808,
- ↑ Charles François Mirbel (Brisseau-Mirbel) was born at Paris in 1776, and died in 1854. He began life as a painter, but having been introduced by Desfontaines to the study of botany, he became Member of the Institute in 1808, and soon after Professor in the University of Paris. From 1816 to 1825 the cares of administration withdrew him from his botanical studies, but he resumed them and became in 1829 Professeur des cultures in the Museum of Natural History. Mirbel was the founder of microscopic vegetable anatomy in France. All that had been accomplished there before his time was still more unimportant than the work done in Germany. His writings involved him in many controversies, and he made enemies by refusing in his capacity of teacher to allow the importance at that time attributed to systematic botany, but directed his pupils to the study of structure and the phenomena of life in plants. We are told by Milne-Edwards that he suffered much from the fierce attacks which were made upon him; he sank at last into a weak and apathetic state, and was for some time before his death unable to continue his studies or official duties ('Botanische Zeitung' for 1855, p. 343).
