The difference between the woody fibre and the wood-cells of coniferous wood may also be seen well in a piece of deal, as cut up for fire-wood. If the end of a stick of this be examined with the naked eye, parts of brown rings will be seen traversing the whiter portion of the wood. These brown rings consist of woody fibre; the white portion of wood-cells. On making a very thin transverse section, the interior of the woody fibres is seen to be almost entirely filled up (Pl. I. fig. 7 _b_), while the cavity of the wood-cells is much more open (Pl. I. fig. 7 _a_); the former also contain globules of turpentine. It must be remarked here that some botanical authors include both forms of woody tissue under the term prosenchyma. But, as we shall see hereafter, the form of the prosenchymatous cells being sometimes used as a character for distinguishing the cells of leaves, to which the term pleurenchymatous cells would be inapplicable, the above distinction will be found important. _Vessels, vascular tissue._--In the next form of tubular cells, these are broader and softer than the cells of woody tissue, thin-walled, and the ends pointed; and their walls exhibit spiral or ring-like markings, or rows of dots (Pl. I. fig. 5 _c_, _e_, _b_), indicating the existence of one or more spiral fibres or rings. When the vessels contain spiral fibres, they are called spiral vessels (Pl. I. fig. 5 _c_); when they contain ring-shaped portions of fibre, they are called annular (_an´nulus_, a ring) vessels (Pl. I. fig. 5 _e_); and when the spaces between the fibres are partly filled up, leaving only dots, the deposit forming a kind of network, we have a reticulated (_réte_, a net) vessel (Pl. I. fig. 5 _b_). This tissue can easily be obtained from a piece of cooked rhubarb, the stem of a balsam, or from any soft-stemmed plant. Vessels very frequently contain air. _Ducts._--The tubular cells forming ducts (Pl. I. figs. 5 _b_, 11 _c_) are large, more or less flattened or blunt at the ends (truncated); and the cell-membrane at first closing the ends is often removed or absorbed, so that the ducts communicate with each other, to allow of the free passage of the sap through them. Their walls are invariably covered with markings, consisting of either simple or bordered dots, resembling those met with in the preceding forms of tissue. The ducts are often easily recognizable with the naked eye, in transverse sections of stems, by the large pores which they form in the wood. These may be well seen in a section of a piece of cane. The tissue composed of dotted ducts is called bothren´chyma (βὁθρος, pit); but the term is principally applied to those ducts in which the dots are simple, _i. e._ have no inner dot.