126 PLANT LIFE 
of the huge leaves. The midrib of each leaf 
is a@ massive structure, and it possesses a 
considerable degree of rigidity. The blade, 
which it traverses, forms a long oval expansion, 
and thus exposes to the air a very considerable 
surface. Any one acquainted only with the 
banana as it grows in a plant house, where 
the air is always quiescent, might easily 
imagine that these large unbroken leaves 
must be remarkably well provided with 
mechanical tissue in order to maintain their 
outline intact. As a matter of fact, however, 
precisely the reverse is the case. The veins 
run out almost at right angles from the 
midrib to the margin, and anastomose very 
little with each other. There is thus no 
mechanical reason why the leaf should not 
be easily torn, and as a matter of fact this 
is what actually happens to a plant grown 
out of doors. The whole blade is reduced to 
a number of separate flaps or strips, each 
firmly attached, of course, to the midrib. 
Hence they can easily give to the breeze, and 
the banana escapes the overthrow to which 
it would be liable were it to hoist such large 
leaves, if unbreakable, in the teeth of the 
wind. The efficiency of the leaf surface is 
practically unimpaired by the tearing, because 
the vascular bundles, running parallel to each 
other, are not broken across, and_ their 
functions as conducting channels to and from 
the midrib to the green leaf surface are not 
interfered with in any way. 
