90 PLANT LIFE 
structure and indeed the whole conformation 
of the plant is dominated by the leaf or other 
equivalent green surface 
CHAPTER IX 
MECHANICAL PROBLEMS AND THEIR SOLUTIONS 
WE will, in the first place, direct our atten- 
tion to the mechanical problems which affect 
plants. These are, broadly speaking, the 
same as those which confront the engineer 
in his ordinary work of building and con- 
struction. There are a variety of stresses 
and strains that have to be guarded against, 
unless the fabric is to collapse either by its 
own weight or by the action of other external 
forces. These mechanical requirements are 
satisfied in practice by choosing materials 
which, in the first place, possess the requisite 
physical characters of strength, toughness 
and the like; and in the second, by utilising 
them to the best mechanical advantage 
economy is combined with efficiency. 
Now it may safely be said that in the 
