no MAPLE. [CHAP. 



brought up nearly to the same level, and immediately 

 to the outside of the first pair. In well-grown shoots 

 there is often a fourth pair on the outside of the 

 second. If we look at such a cluster of leaves directly 

 from in front, we shall see that they generally appear 

 somewhat to overlap ; but it must be remembered 

 that in temperate regions the sun is never vertical. 

 Moreover, while alternate leaves are more convenient 

 in such an arrangement as that of the Beech, where 



FlG. 69. Acer. 



there would be no room for a second leaf, it is more 

 suitable in such cases as the Sycamores and Maples 

 that the leaves should be opposite, because if, other 

 things remaining the same, the leaves of the Sycamore 

 were alternate, the sixth leaf would require an incon- 

 venient length of petiole. 



Perhaps it will be said that the Plane-tree, which has 

 leaves so like a Maple that one species of the latter 

 genus is named after it (Acer platanoides, Fig. 69), has, 

 nevertheless, alternate leaves. In reality, however, I 

 think this rather supports my argument, because the 



