_Woody tissue._--Of this there are two forms, called respectively wood-cells and woody fibres. The _wood-cells_ are moderately long, more or less tapering and overlapping at the ends; and the cell-walls are thickened, so as to possess considerable firmness. These cells are found in the wood of stems, as in the white woody portion of an ash stick, that of a lime-tree, the stem of a Chrysanthemum, &c. (Pl. I. fig. 6). They are closely packed, and the tissue formed by their union is called _prosen´chyma_ (πρὸς, close, ἔλχυμα, tissue). In the other kind of woody tissue the cells are very long and slender, strong, yet flexible, gradually tapering at the ends, where they overlap each other; and they have thick walls, so that, when divided transversely, the cavity appears almost filled up (Pl. I. figs. 5 _d_, 9, & 7 _b_). This tissue is called _woody fibre_ or _pleuren´chyma_ (πλευρἀ, rib, ἔγχυμα), from its strength. The walls of the cells of woody tissue are often covered with dots, either simple or with an inner dot (Pl. I. fig. 6 _b_, fig. 11 _b_), or with streaks (Pl. I. fig. 6 _a_) or with a spiral fibre (fig. 11 _b_, _c_), either alone or with dots also. This tissue is of great importance in plants, from its strength and flexibility; it forms a considerable part of the veins of leaves, the inner bark (_liber_), and of the wood of the stems of trees. It is also very useful to man: for it constitutes hemp, of which rope and string are made; flax, of which linen is made; cocoanut fibre; bast, used by gardeners for tying up plants, which is the inner bark of the lime; and jute, which is the inner bark of an Indian lime-tree. In the white woody part of the stems of trees belonging to the fir-order (Conif´eræ), as a piece of deal or pine, which is mainly composed of wood-(prosenchymatous) cells, the cells exhibit rows of minute circular markings (Pl. I. fig. 10). These were formerly supposed to be solid bodies or glands; hence the tissue is still sometimes called glandular. Within the outer ring of each marking is an inner central dot, or sometimes an oblique streak. The side view of the cells (Pl. I. fig. 8 _a_), which is seen in a tangential section, shows that the markings are minute pits, each being opposite to one of an adjacent cell, and sunk inwards towards the centre of the cell, the inner dot or streak being a thinner portion of the cell-wall. This glandular tissue of the Coniferæ is interesting as forming a test-object for the defining power of the microscope, which should show the two rings sharply and free from colour; the section of the wood should be examined as a dry transparent object.