Pine and Basswood, they are thinner.

411. Wood-cells in the bark are generally longer, finer, and tougher
than those of the proper wood, and appear more like fibres. For example,
Fig. 446 represents a cell of the wood of Basswood of average length,
and Fig. 444 one (and part of another) of the fibrous bark, both drawn
to the same scale. As these long cells form the principal part of
fibrous bark, or _bast_, they are named _Bast-cells_ or _Bast-fibres_.
These give the great toughness and flexibility to the inner bark of
Basswood (i. e. Bast-wood) and of Leatherwood; and they furnish the
invaluable fibres of flax and hemp; the proper wood of their stems being
tender, brittle, and destroyed by the processes which separate for use
the tough and slender bast-cells. In Leatherwood (Dirca) the bast-cells
are remarkably slender. A view of one, if magnified on the scale of Fig.
444, would be a foot and a half long.

[Illustration: 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.

[Illustration: 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.

_Annular_ ducts (Fig. 457) are marked with cross lines or rings, which
are thickened portions of the cell-wall.

[Illustration: Fig. 453, 454. Spiral ducts which uncoil into a single
thread. 455. Spiral duct which tears up as a band. 456. An annular duct,
with variations above. 457. Loose spiral duct passi