BESSEY: STOMATA OF HOoLACANTHA 527 
Explanation of plate 24 
Part of a cross-section of a twig: ef, epidermis ; /, palisade tissue; 4, hypo- 
dermal layer with thick, cellulose walls: c7, a crystal; sf, stomal papilla, in section ; 
cy, chimney-like cavity extending from apex of papilla to the stoma at its bottom; g, 
guard-cells of stoma, in cross-section ; sc, stomal cavity, the so-called air-cavity in the 
palisade tissue. 40. 
. Another section similar to A, showing slight variations in the stomal appa- 
ratus : the lettering as 165. 
. Section of : ills (sp), chimney-like i A and guard-cells (g), show- 
ing ‘he pares rows of boundary cells (dc). 
Section of the epidermis parallel and near to the surface, showing the outer 
layer of oeaiohe cells (ef), the cavities separated by thick walls; 4c, the boundary 
cells of the stomal chimneys in cross-section. >< 165. 
E. Vertical section of the epidermis parallel tp the surface but through or near to 
its inner layer, showing cross-sections of stomal chimneys (ev), and palisade tissue (p). 
At s¢ is a stoma, with some of its boundary cells attached. 165. 
F. Transverse section of the epidermis, showing the inner epidermal layer (tep) 
and an isolated stoma (58 Fas E165. 
