. The American botanist and florist: including lessons in the structure, life, and growth of plants; together with a simple analytical flora, descriptive of the native and cultivated plants growing in the Atlantic division of the American union. Botany; Botany. THE TISSUES. 129 («) to the earliest formed part of the 1^1 390. The pitted cells (§ 376) constitute a singulai- variety of wood-fibre, common in Pines, Firs, etc. That mysterious double ring -which encircles each pit, is projected, the inner by the pit itself, which is an aperture in the secondary layer, the outer by a lens-shaped inte
. The American botanist and florist: including lessons in the structure, life, and growth of plants; together with a simple analytical flora, descriptive of the native and cultivated plants growing in the Atlantic division of the American union. Botany; Botany. THE TISSUES. 129 («) to the earliest formed part of the 1^1 390. The pitted cells (§ 376) constitute a singulai- variety of wood-fibre, common in Pines, Firs, etc. That mysterious double ring -which encircles each pit, is projected, the inner by the pit itself, which is an aperture in the secondary layer, the outer by a lens-shaped intercellular cavity opposite, outside (474). 391. Trachenchyma is a tissue of vessels or tubes rather than cells. The vessels are extended lengthwise, and composed each of a row of cells joined end to end, and fused into one by the absorption of the contiguous walls. This tissue varies ac- cording to the character of the constituent cells, which are (a) spiral, or {b) annular, or (c) scalariform, or {d) reticulated. 392. Such cell?, with their tapering ends, form vessels with oblique joints. When porous cells with their truncated ends unite, they form right-jointed vessels resembling strings of beads, called dotted or vascular ducts. These are usually quite large, and char- acteristic of the woody layers of all Exogenous plants. The different varieties of trachen- chyma are assigned to difterent regions and office; wood, the petioles and veins of leaves, petals of flowers, etc.; (b) to similar parts, but later formed, most abundant in Ferns and Equiseta- cere ; (c) in the woody bundles of the Endogens, and in the succulent parts of plants in general; (rf) most abundant in Ferns, Club-mosses. 393. Cienchyma is a system of milk-vessels—vessels secreting the latex or peculiar juice of tiie plant, white, yellow, red, turbid, containing opium, gamboge, caout- chouc, resin, etc. It occurs in the petioles and veins ; in the paren- chyma of roots, in the Liber espe- cially ; sometimes
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