PHARMACEUTICAL BOTANY 
114 
Histology of a Typical Woody Monocotyl Stem. — The stem of the 
Greenbrier, a woody monocotyl, will here be considered. In trans- 
verse section passing from periphery toward the center the following 
structural details will be noted: 
1. Epidermis, of a single layer of epidermal cells whose outer walls 
are strongly cutinized. Cutin is a wax-like substance which forms 
a protective coat to the epidermis, preventing the evaporation of 
Fig. 52. — Cross-section of cornstalk stem; a, epidermis; b, cortex and 
c, ground tissue. ( After Stevens.) 
water, the ingress of destructive parasites, and injury from insects. 
2. A cortex, composed of about ten or twelve layers of thick- walled 
parenchyme cells, the outer two or three layers of which are termed 
hypodermis. 
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 sclerenchymatous fibers and undeveloped fibro- 
vascular bundles of the closed collateral type. 
5. A central matrix of strongly thickened parenchyme 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 tracheae and 
