. Class-book of botany : being outlines of the structure, physiology, and classification of plants ; with a flora of the United States and Canada . Botany; Botany; Botany. 136 THE TISSITES. contiguous walls. This tissue varies according to the character of the constituent cells, which are (a) spiral, or (6) annular, or (c) sclariform, or {d) reticulated. 669. Such cells, with their tapering ends, form vessels with oblique joints. When porous'cells (653) with their truncated ends unite they form right-jointed vessels re- aembhng strings of beads, called dotted or vascula/r ducts. These are usua
. Class-book of botany : being outlines of the structure, physiology, and classification of plants ; with a flora of the United States and Canada . Botany; Botany; Botany. 136 THE TISSITES. contiguous walls. This tissue varies according to the character of the constituent cells, which are (a) spiral, or (6) annular, or (c) sclariform, or {d) reticulated. 669. Such cells, with their tapering ends, form vessels with oblique joints. When porous'cells (653) with their truncated ends unite they form right-jointed vessels re- aembhng strings of beads, called dotted or vascula/r ducts. These are usually quite large, and characteristic of the woody layers of all exogenous plants. (470.) 670. The dipfeeent taeieties of tkaohenohtma are assigned to different re- gions and olBces, (a) to the earUest formed part of the wood, the petioles and veins of leaves, petals of flowers, etc.; (6) to similar parts, but later formed, most abundant in ferns and Equisetaoese; (c) in the woody bundles of the Endogens and in the succu- lent parts of plants in general; (d) most abundant m ferns, dub-mosses. 671. CiENCHTMA is a system of milk-vessels—vessels secreting the latex or peculiar juice of the plant, white, yellow, red, turbid, containing opium, gamboge, caoutchouc, resin, etc. It occurs in the petioles and veins ; in the parenchyma of roots, in the liber es- pecially ; sometimes simple, generally branched and netted in a complicated manner, as well seen in the poppy, ce- landine, blood-root, gum-elastic tree, etc. These vessels are probably mere open spaces between the cells at first, subsequently acquiring a lining membrane which never exhibits pores or spiral markings. But there ar^lso true 673. Intercellular passages filled with air and admitting its free circulation in all directions through the parenchyma. These are neces- sarily very irregular, and they communicate with the external air through the stomata. (§ 678.) 674. Import of the cell. Thus the cell appears to be the type
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