120 PHARMACEUTICAL BOTANY 
gritty particles in the “flesh” of certain fruits as the Pear, the 
endocarp or stone region of drupaceous fruits as the Olive, 
Peach, Cubeb, Pepper, etc., the hard portions of seed coats as 
in Physostigma, Walnuts, etc. Each stone cell presents for 
examination a cell wall of cellulose with one or several layers 
of lignin on its inner surface which surround a central lumen. 
Fic. 61,—Sclerenchyma fibers from different sources. 1, From powdered 
cinnamon bark; 2, end of bast fiber of flax stem showing transverse markings 
(4); 3, middle portion of flax fiber showing characteristic cross markings at }; 4, 
bast fiber from cinchona bark; 5, branched bast fiber from choke cherry bark; 6, 
above, end, and below, medium portion of bast fiber of jute. All highly magnified. 
The latter is in communication with radial pore canals leading 
outward to the middle lamella. Longitudinal pore canals 
are also evident. 
Fisers.—When sclerenchyma is composed of cells which are 
greatly elongated and more or less obtusely or taper ended, its 
component elements are termed SCLERENCHYMA FIBERS or 
Firsers. These fibers are frequently spindle-shaped. When 
young they contain protoplasts but when mature their lumina 
usually contain air. They exhibit pits of the nature of oblique 
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