48 Gardening 
ae eee er epidermis 
ppt <P? 
Palisade layers 
Intercellular 
Mesophyll tissue 
a1 Food-con- 
& |ducting tissue x 
&|Bundle sheath/ Guard cell 
ig Stoma: 
| ay 
Chloroplast 
Fic. 34. Section of a leaf, very highly magnified. 
goes on in all green parts of the plant, but takes place 
especially in the leaves. 
Leaves as sugar-making organs. As the term photo- 
synthesis indicates, the energy used in building up sugar 
is furnished by the light. Without light, plants cannot 
do this work ; and when we examine a plant, we note at 
once that the broad, thin blades of ‘the leaves and the 
way they are arranged on the plant enables them to 
catch large amounts of light. This makes it possible 
for the manufacture of sugar to be carried on rapidly by 
the plant. ; 
But it is only when we examine the internal structure 
of a leaf that we understand how well fitted it is for 
