. A Manual of botany : being an introduction to the study of the structure, physiology, and classification of plants . Botany. 20 FOEM AND AKEANGEMENT OF VESSELS. (reticulum, a net); and the name dotted is sometimes applied when the fibre is so broken up as to leave small isolated portions adhering to the membrane (fig. 62). In scalariform vessels (scala, a ladder), there are short horizontal lines or bars, composed of fibre, arranged along the sides of the tubes, at nearly equal distances, like the steps of a ladder, and presenting a striated appearance. In some cases, as in the Vine (fig. 63
. A Manual of botany : being an introduction to the study of the structure, physiology, and classification of plants . Botany. 20 FOEM AND AKEANGEMENT OF VESSELS. (reticulum, a net); and the name dotted is sometimes applied when the fibre is so broken up as to leave small isolated portions adhering to the membrane (fig. 62). In scalariform vessels (scala, a ladder), there are short horizontal lines or bars, composed of fibre, arranged along the sides of the tubes, at nearly equal distances, like the steps of a ladder, and presenting a striated appearance. In some cases, as in the Vine (fig. 63), they are composed of tubes united to each other by thin, broad, oblique extremities; at other times they taper like spiral vessels. They generally assume a prismatic form, the angles being unmarked by lines, as is seen in Ferns (fig. 64). Pitted Vbssels.^—Another kind of vessel common in plants is the pitted vessel, so called from the appearance of pits or depressions on its surface. The tissue formed by pitted vessels has received the name of Vasiform tissue, Pitted tissue, Bothrenchyma, or Taphrenchyma (j366§og or rd,(pgog, a pit). The vessels are of large size, and are easily observed in the Vine (fig. 65), Sugar Cane, Bamboo, Gourd (fig. 116 ter), and other plants, in which the sap circulates rapidly. They consist of cylinders more or,Jess elongated, in which the thickening matter is so deposited as to leave part of the membrane un- covered, thus giving rise to the porous or pitted appearance. The uncovered portions of membrane are sometimes absorbed in old vessels, and a direct communicar tion is established between them. The pits or so-called pores have sometimes a bordered aspect, which, according to Schleiden, depends on air contained in -the cavities between contiguous ves- sels. Pitted or porous vessels are usually united to each other by a broad and often oblique septum. This kind of vessel occasion- ally presents a beaded appearance, as if formed by pitted cel
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