632 Bray: THe Tissues oF SOME OF THE 
spiral clusters following certain wavy depressions in the stem. 
When the stem is perfectly turgid these depressions are faint, but 
with the approach of wilting they become more prominent. It 
appears that in this emergency the stomata would be depressed 
farther below the surface. Very interesting is it to examine a 
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Fic. 10. View of portion of pith-area seen in cross-section of Z. antisyphilitica ; 
arm, the irregular pith-cells with numerous projecting arms giving lateral connection 
across larger or smaller intercellular passages, 7,7, etc. 
young wilted stem in which the stomata all lie at the bottom of 
the wrinkles caused by wilting. It would appear evident that the 
tissue beneath the stomata is less firm than elsewhere and as 4 
matter of fact a superficial tangential section reveals that the sub- 
stomatal assimilation-cells are irregular, making 2, 3 or 4 way CO? 
nections with other cells and so giving rise in effect to a limited 
spongy mesophyl. 
The waxy covering appears to be a secretion of the epidermal 
wall. It is added layer by layer, the striations remaining distinct 
