170 



VEGETABLE KINGDOM DIAGRAM 9. 



The stem raises the leaves into the air; they are generally 

 renewed every year ; the stalk which supports them is called tho 

 petiole. The surface of the leaf is supported by the nervures ; to 

 see them well, an oak-leaf may be dried in a book, and then 

 rubbed gently with a brush. AH the parenchyma between the 

 neiTures fall off, and only the latter remain. Only dicotyledonous 

 plants have nervures like those of the oak. Monocotyledons havo 

 none, and the leaf seems to be formed of parallel fibres only, as 

 may be seen in the leaves of the lily, the leek, the wheat, and tho 

 reed, which are monocotyledonous plants. 



Ordinary leaves are called simple leaves, but there are also 

 compound leaves; and the separate 

 parts of these are called leaflets. The 

 horse-chestnut has four or five leaflets, 

 springing from the 

 end of the same 

 petiole, which to-' 

 gether form a leaf, 

 In the acacia and 

 rose tree the po- 

 Kose Leaf. tiole terminates in 



one leaflet, and other leaflets are arranged two and two on opposite 

 sides ; which also together form one leaf. To see if the leaf is 

 simple or compound, we must observe the position of the bud 

 which is at the axis of every petiole. When, as in the acacia or 

 chestnut-leaf, the bud is at the axis of the common petiole, then 

 all the small leaves which it bears are only leaflets. They all fall 

 off together with the common stalk. 



Chestnut Leaf. 



