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. 



