THE STEM 211 
rays possess brownish contents which take a red color with an 
alkaline solution. 
In radial longitudinal section, a lengthwise view of the tissues will 
be seen. The medullary-rays appear 15 to 25 cells in height and 
crossing at right angles to the other elements. The crystal 
f 
co 
ST 
ph 
xT 
td? 
td‘ 
Fic. 141.—Transverse section of representative portion of the stem of the second 
year’s growth of spruce (Picea sp.), a conifer. (X 80.) ep, epidermis; ck, cork; 
pn, phellogen; co, cortex; sr, secretion reservoir; ph, phloem; ca, cambium; xr, 
xylem ray; td', tracheids of autumn wood of first year; id?, tracheids of wood of 
second year. 
fibers here will be seen to be composed of vertical rows of super- 
imposed thin-walled cells each of which contains a monoclinic 
‘ prism of calcium oxalate. The phloem (bast) fibers appear 
elongated and taper-ended and are associated with crystal fibers. 
The sieve tubes show sieve plates on their longitudinal as well as 
their transverse walls in this bark. 
