regular cell-tissue, the shapes of the cells being like geometrical bodies, in opposition to the irregular tissue of Fuci,
Lichens and Fungi. It is a decided improvement on former
practice, and one that marks his later works also, that in connection with the structure of the solid cell-fabric he discusses the
contents of cells in a special chapter, in which first the matter
in solution, then the granular bodies with organized structure
are considered, though with the latter he classes not only starch-grains, chlorophyll-corpuscles and the like, but also the spermatozoa in pollen-grains and layers of thickening matter projecting
on the inside of cell-walls, such as the spiral bands in the elaters
of Jungermannieae and several similar formations. He describes
the crystals in vegetable cells at some length, and finally
discusses the movement of the cell-contents ('sap'), not
omitting that of rotation in the Characeae as observed by
Corti, and in other water-plants. The chapter on intercellular
spaces also shows considerable advance on the views which
obtained in 1812; Meyen calls it an account of the spaces
produced in cell-tissue by the union of the cells; the true
intercellular passages filled with air are here distinguished from
receptacles of secretions, resin- passages, gum-passages, oil-
passages, and secretion-receptacles of the nature of cavities.
The large air-passages and gaps, such as occur in water-plants,
are a third form of intercellular space; his air-canals in the
wood of oak filled with cell-tissue are obviously vessels filled with the substance known as thylosis. The form of the cells in the tissue he thinks is not due to mutual pressure, and he rejects Kieser's view that the ideal fundamental form of cells
must be a rhombododecahedron; but he thinks there is a
significant resemblance between the shape of cells and that
of basaltic columns.
In dealing with the spiral tube-system he first discusses the spiral fibre, which appears, he says, either detached between the cells or inside them as well,—an account of the matter decidedly inferior to those of Bernhardi and Treviranus. The spiral
