94 THE ENDOGENOUS OR MONOCOTYLEDONOUS STEM. 
2. Outer Bark, composed of parenchyma, and hence belong- 
ing to the parenchymatous system, and consisting of — 
a. Cellular Envelope or Phelloderm, composed of more or 
less angular cells, with interspaces, and giving the 
green colour to bark. 
b. Corky Layer or Suwberous Layer, composed of tabular 
cells, forming a compact tissue, and giving the pecu- 
liar hues to the young bark. 
7. The Epidermis, investing the bark of young stems, and re- 
placed after a certain age by the corky layer. 
Fie. 192. 
Fig. 192. Diagram of a Monocotyledonous stem. A. Transverse section. 
B. Vertical section. a, a. Parenchymatous tissue. 6, 0. Pitted vessels. 
ec. Wood and liber cells. d, d. Spiral vessels. (The letters mark similar 
parts in both sections.) After Carpenter. 
B. Enpocenovs or Monocoryteponovus Stem.—In this 
country we have no indigenous trees or large shrubs which ex- 
hibit this mode of growth, although we have numerous herba- 
ceous plants, such as Grasses, Rushes, and Sedges, which are 
illustrations of endogenous structure. In our gardens, again, 
we have various kinds of Lilies, Hyacinths, Tulips, and other 
bulbous plants, which are also endogenous in their growth. But 
it is in the warmer regions of the globe, and especially in the 
tropics, where we find the most striking and characteristic illus- 
trations of such stems, and of all such the Palms are by far the 
most remarkable. 
