192 PLANT ANATOMY. 
The ordinary cork, of Quercus Suber, corresponds in its form 
to the above type.' Deviations from this fundamental form 
Fie. 105.—Cortex Guaiaci. a, thickened cork-cells; a’, phellogen layer; b, primary 
bark; c, sclerenchymatous layer. 
depend upon a more undulating—though on a transverse sec- 
tion, generally radial—course of the transverse walls, or upon a 
o/ 
rae 
Fie. 106.—Radix Pyrethri romani. a, thickened cork-cells; b, oil-spaces; *, xylem 
rays (wood-bundles), 
thickening of one or all sides (as seen in Figs. 102, 103, 108) 
of the ordinarily thin walls (Figs. 97, 104, 105). 
* Yet in cork (bottle-cork), numerous stone-cells occur (Fig. 101). 
