EXPLANATION OF THE PLATES. 
PLATE TPIE FIRST. 
ANATOMY OF THE STEM. 
Fig. 1 . Platanus orientalis, Salicince. A transverse 
section of a young branch, to exhibit the organization, 
■which is similar to that of the greater part of dicotyledon 
trees. 
Fig. 2. A magnified representation of a portion cut out 
of the above section. 
a to b. Bark. 
a to c. Outer part of the bark, dry and disorganized. 
b to c. The live part of the bark. 
c to d. A part of the bark which is continually pushed 
to the circumference. 
b to d. Inner part of the bark, called the liber or bast. 
e. The origin of the medullary radii that fill up the in- 
terstices of the wood, and which are formed of the cellular 
tissue of the bark. 
f. The extremity of the filaments that form the inter- 
stices of the wood. 
b to i. The woody mass, composed of three zones, or 
layers, b— g, g — h , and h — i. 
h to i. The oldest of the three layers. 
g to fi. The second layer. 
b to g. The third or youngest layer. 
b , g, and h. Zones which show the periods when the ve- 
getation slackened. 
i to k. Pith. 
Fig. 3. Ptychosperma gracilis. Palmce . Vertical and 
transverse section of the stem, to show the difference be- 
tween the stems of monocotyledon plants and those of di- 
cotyledon plants. 
Fig. 4. A magnified figure of the same. 
a to b. That part of the stem where the hardest woody 
fibres are the most closely collected together. 
