THE TISSUES OF PLANTS. 17 
40. Stony Tissue (Sclerenchyma).—In many plants the 
hard parts are composed of cells whose walls are thickened, 
often to a very considerable extent (Fig. 9). The cells are 
usually short, but in some cases they are greatly elongated; 
they are sometimes regular in outline, but more frequently 
they are extremely irregular. They do not contain chloro- 
Fic. 9.—Stony tissue. A, from shell of Hickory-nut; Band C, from under- 
ground stem of the common Brake (Pteris). Magnified 400 to 500 times. 
phyll, but in some cases (e.g., in the pith of apple-twigs) 
they contain starch. 
41, Fibrous Tissue. —This is composed of elongated, 
thick-walled, and generally fusiform fibres (Fig. 10), whose 
walls are usually marked with simple or sometimes bordered 
pits. These fibres in cross-section are rarely square or 
round, but most generally three- to many-sided. They are 
found in, or in connection with, the woody bundles of ferns 
