THE TISSUES OF PLANTS. 



17 



40. Stony Tissue {8clerenchyma). — 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- 



FiG. 9.— stony tissue. A, from shell o( Hickory-nut; B and 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 (Pig. 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 



