Fig. 448. Magnified bit of a pine shaving, taken parallel with the silver grain. 449. Separate whole wood-cell, more magnified. 450. Same, still more magnified; both sections represented: a, disks in section, b, in face.
412. The wood-cells of Pines, and more or less of all other Coniferous trees, have on two of their sides very peculiar disk-shaped markings (Fig. [448-450]) by which that kind of wood is recognizable.
Fig. 451, 452. A large and a smaller dotted duct from Grape-Vine.
[413.] Ducts, also called Vessels, are mostly larger than wood-cells: indeed, some of them, as in Red Oak, have calibre large enough to be discerned on a cross section by the naked eye. They make the visible porosity of such kinds of wood. This is particularly the case with
Dotted ducts (Fig. [451, 452]), the surface of which appears as if riddled with round or oval pores. Such ducts are commonly made up of a row of large cells more or less confluent into a tube.
Scalariform ducts (Fig. [458, 459]), common in Ferns, and generally angled by mutual pressure in the bundles, have transversely elongated thin places, parallel with each other, giving a ladder-like appearance, whence the name.