106 



ESSENTIALS OF BOTANY 



leafy twig, by a twisting about of the petioles. The adjust- 

 ment in many opposite-leavgd trees and shrubs consists 

 in having each pair of leaves cover the spaces between 

 the pair below it, and sometimes in 

 the lengthening of the lower peti- 

 oles so as to bring the blades of 

 the lower leaves outside those of 

 the upper leaves. Examination 

 of Figs. 72 and 73 will make the 

 matter clear. 



The student should not fail to 

 study the leafage of several trees 

 of different kinds on the growing 

 tree itself, and in climbers on walls, 



"*' ' i !f irangemen ^^^ ^^ notice how circumstances 

 of the Oak. 



modify the position of the leaves. 



Maple leaves, for example, on the ends of the branches are 

 arranged much like those of the horse-chestnut, but they 

 are found to be arranged more nearly flatwise along the 

 inner portions of the branches, 

 that is, the portions nearer the 

 tree. Figs. 74 and 75 show the 

 remarkable difference in arrange- 

 ment in different branches of the 

 Deutzia, and equally interesting 

 modifications may be found in 

 alternate -leaved trees, such as 

 the elm and the cherry. 



125. Leaf-Mosaics. — In very 

 many cases the leaves at the end of a shoot are so arranged 

 as to form a rather symmetrical pattern, as in the horse- 

 chestnut (Fig. 72). When this is sufficiently regular, 



Fig. 71. Leaf Arrangement 

 of European Beech. 



