VI.] EUCALYPTUS. IVY. 121 



and consequently exposes as little surface as possible 

 to the overpowering sun. In some species the long 

 and narrow phyllodes carry this still further by hang- 

 ing downwards, and in such cases they often assume 

 a scimitar-like form. This I would venture to 

 suggest may be in consequence of one side being 

 turned outwards, and therefore under more favourable 

 conditions. 



In one very interesting species (Acacia melan- 

 oxylon. Fig. 74), the plant throughout life produces 

 both forms, and on the same bough may be seen 

 phyllodes interspersed among ordinary pinnate 

 leaves, the respective advantages being, it would 

 appear, so equally balanced that sometimes the 

 one, sometimes the other, secures the predominance. 



In the case of the Eucalyptus, every one who has 

 been in the South of Europe must have noticed 

 that the young trees have a totally different aspect 

 from that which they acquire when older. The leaves 

 of the young trees (Fig. 76) are tongue-shaped, and 

 horizontal. In older ones, on the contrary (Fig. "jf), 

 they hang more or less vertically, with one edge towards 

 the tree, and are scimitar-shaped, with the convex 

 edge outwards, perhaps for the same reason as that 

 suggested in the case of Acacia. There are several 

 other cases in which the same plant bears two kinds 

 of leaves. Thus, in some species of Juniper the leaves 

 are long and pointed, in others rounded and scale-like. 

 funiperus chinensis and some others have both. 



In the common Ivy the leaves on the creeping 

 or climbing stems are more or less triangular, while 

 those of the flowering stems are ovate lanceolate ; a 



