218 PHARMACEUTICAL BOTANY 
3. An endodermis, wavy in character and composed of 
endodermal cells whose brownish walls are strongly suberized. 
4. A sclerenchymatous cylinder sheath composed of somewhat 
separated masses of sclerenchyma (pericyclic) fibers and unde- 
veloped fibro-vascular bundles of the closed collateral type. — 
Fic. 148.—Photomicrograph of a representative portion of Greenbrier stem 
showing epidermis (¢.p.), cortex (c), endodermis (e.n.d.), cylinder sheath (c.s.), 
sclerenchyma fibers of closed collateral bundle (6), fundamental parenchyma 
(f.p.), trachea (t). X 22. 
5. A pith or central matrix of strongly thickened, more or less 
lignified, parenchyma cells in which are scattered, irregularly, 
numerous Closed collateral bundles. Small starch grains will be 
found in the parenchyma cells. Examine a representative 
bundle, and note the two very large trachez and several smaller 
ones in the xylem portion of the bundle which faces toward the 
center of the section. In the outer or phloem portion of the 
