146 ANATOMY OF STEM, ROOT AND LEAF 



water-vapour in the transpiration process, and are concerned 

 also with the interchange of gases which goes on between the 

 atmosphere and the air within the plant' in the process of 

 respiration and 'assimiMion.' 



Fig. 75. — i. Transverse section through a plum leaf (somewhat diagrammatic). 

 2. Enlarged view of portion A from 1 . e Epidermis ; x stomata ; p palisade parenchyma ; 

 J spongy parenchyma ; i vascular bundles. (Enlarged 160 diameters.) 



The ground-tissue of the leaf is a continuation of the cortex 

 of the stem and is termed the mesophyll. In ordinary flat leaves 



