. The cell and protoplasm ... Cells; Protoplasm; Cytology; Cytoplasm. 32 THE CELL AND PROTOPLASM. Fig. 3. Piiritied and expanded cellulosie matrix from section similar to Fig. 2. Total enlargement, X3600. Fig. 4. Lignin residue of section similar to Fig. 2. Total enlargement, x 3000. shows conspicuous conceutricites or laniella- tions, and, in addition, a finer radial pat- tern that approaches the limits of micro- scopic visibility. Fi<i'. 2, on the contrary, exhibits a doiiiinantly radial and ramifying- pattern. When such sections of the sec- ondary Avail are carefully and ur;idually expan
. The cell and protoplasm ... Cells; Protoplasm; Cytology; Cytoplasm. 32 THE CELL AND PROTOPLASM. Fig. 3. Piiritied and expanded cellulosie matrix from section similar to Fig. 2. Total enlargement, X3600. Fig. 4. Lignin residue of section similar to Fig. 2. Total enlargement, x 3000. shows conspicuous conceutricites or laniella- tions, and, in addition, a finer radial pat- tern that approaches the limits of micro- scopic visibility. Fi<i'. 2, on the contrary, exhibits a doiiiinantly radial and ramifying- pattern. When such sections of the sec- ondary Avail are carefully and ur;idually expanded by the use of suitable s^velling• reagents, finer and finer details of the char- acteristic structural patterns become suc- cessively visible under the microscope (Figs. 3 to 6). In all cases the secondary wall resolves itself ultimately into a system of fine threads, or microfibrils, which are variously aggregated and more or less ex- tensively coalesced. Where the microfibrils are oriented approximately parallel to the long axis of a cell, they appear in expanded transverse sections of such a cell as more or less circular specks or granulations (Fig. 5). The concentric, radial, ramifying, and other structural patterns of the secondary wall are due, therefore, to varying densities or porosities in different parts of the wall. In the denser (darker) parts, the micro- fibrils are more numerous per ^^nit area and are more extensively coalesced, whereas in the more porous (lighter) parts they are less closely aggregated and the area of in- terfibrillar capillary spaces is larger. In the case of a heavily lignified secon- dary wall, it is possible to remove the cellu- lose and leave a firmly coherent residue of lignin; and, conversely, it is possible to re- move the lignin and leave the coherent matrix of cellulose. The cellulosie matrix (Fig. 3) and the lignin residue (Fig. 4) exhibit positive and negative images of the same original, nnswollen structural pat- tern (Fig. 2).
Size: 1054px × 2371px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthoramericanassociation, bookcentury1900, booksubjectcells
