IV 



THE STUDY OF THE SHOOT 



37 



When two leaves spring from the node and face each other, the 

 arrangement is called opposite ; if the leaves higher up are 

 placed at right angles to the first pair, the arrangement is called 

 decussate the Deadnettle is a good example of this. If more 

 than two leaves are produced at a node, they are termed 

 whorled leaves. The 

 Bed-straw and Cleavers 

 illustrate this arrange- 

 ment. 



The most common ar- 

 rangements of leaves are 

 the alternate, opposite, 

 and whorled. The so- 

 called alternate arrange- 



Start of Spiral 

 Twig ofOaJc . 



FIG. 40. -Whorled leaves of 

 Cleavers. 



FIG. 41. Diagram illustrating phyllo- 

 taxis of Oak. 



ment can be further investigated by drawing a spiral round the 

 stem from one leaf until the leaf vertically above is reached. In 

 the case of the Wallflower or Oak the spiral goes round the stem 

 twice before the leaf vertically above is reached, and five leaves, 

 not counting the leaf at which the spiral commenced, are touched 

 by the -spiral. This is known as a arrangement. The same 

 phyllotaxis is found in the Pear, Poplar, and Walnut. In the 

 Plantainthe leaves form a $ phyllotaxis. 



