Pulp and paper magazine of Canada . leaf-sheath is the occurence of n Ue/> McGill University. highly elastic wall!*, seen as darker groups of cells infigure 20. Chemical Characters of the Tissues. When the cell-walls are first formed, they are com-posed of cellulo-se, with a layer (the primary mem-branej of pectose between the adjacent walls. As de-velopment proceeds, additional substances (lignin-bodies) the chief of whicii passes under the term ligninare added to the Malls. Stem.—In the mature straw, all the cell-walls becomestrongly lignified with the exception only of theph
Pulp and paper magazine of Canada . leaf-sheath is the occurence of n Ue/> McGill University. highly elastic wall!*, seen as darker groups of cells infigure 20. Chemical Characters of the Tissues. When the cell-walls are first formed, they are com-posed of cellulo-se, with a layer (the primary mem-branej of pectose between the adjacent walls. As de-velopment proceeds, additional substances (lignin-bodies) the chief of whicii passes under the term ligninare added to the Malls. Stem.—In the mature straw, all the cell-walls becomestrongly lignified with the exception only of thephloem, the thin-walled xylem (wood) lying on eitherside of the ])rinuiry wood, the collapsed i)ith cells, andthe ehlorenchyma. The lignified tissues tiierefore arethe epidermis, all the fibers, all the wood vessels.(tracheids) and the parenchyma (.save the inner pithi-eiis and ehlorenchyma) (figure 4). On account of thecompleteness of lignification the cellulose of straws(grain straws) are regarded chemically as Figure 25. — Portion of a section of the leafslieatii of wlieat. the wide (1, 1) thin walled cells justabove the bundles, u. upijer (inner) epidermis, x 130. very long, thin walled tubular cells, (1, figure 25),forming a small group of between the largebundles and the upper (inner) epidermis. They canhardly be classed as fibers—or at an,v rate they cannotbe compared with in point of strength, since thewalls are thin and tiie lumen large, measuring (iO mic-rons, more or less. The end walls are transverse, oblique, or forked. They are relatively few innumber, but can be found in jiulp or strawpaper. False Nodes.—The above described structure failsalmost entirely at the base of the leaf-sheath, wherethe motile organ or false node occurs. There is an en-tire absence of sjjecializcd ehlorenchyma, and the is thick walled. The walls, however, in com-mon with those of the bundles o
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