CHAPTER IV 



THE LEAF 



DURING the previous practical work we have had 

 occasion to observe the structures, known as leaves, 

 which are borne on the stems of plants. It is a matter 

 of common knowledge that the leaves of different plants 

 vary greatly in size, character and shape,and we commonly 

 distinguish plants, when not in flower, by the shape of 

 their leaves. Apart from these minor differences many 

 leaves agree in having a more or less thin, flattened, 

 green portion, known as the blade of the leaf, which may 

 be " simple " in shape, as a privet, elm, or nasturtium leaf, 

 or much divided, as an ash, rose, or vetch leaf. In many 

 plants for example, the sow-thistle or honeysuckle this 

 leaf-blade joins directly on to the stem, but in others it 

 has a thinner, generally rounded, lower portion, the leaf- 

 stalk, easily seen in a maple, horse chestnut or nasturtium. 

 In addition to these two parts many, but by no means 

 all, leaves show, at the point where they join the stem, a 

 pair of bodies which are known as stipules. These may 

 be small, as in the garden geranium, or comparatively 

 large, as in the pea, pansy and hawthorn. 



The blade of the leaf has been spoken of hitherto as 



