Tubers — Starch 



branches thickening in the open air, swelling 

 up and becoming more or less perfect potatoes. 



Many other plants produce similar under- 

 ground branches. Among these is the 

 Jerusalem artichoke, the tubers of which 

 have their shoots arranged in pairs, just like 

 the leaves and shoots on the stem. 



The potato feeds its shoots with a floury 

 substance called starch ; the same substance 

 which makes it so valuable a food for our- 

 selves. We profit by the provision made by 

 the plant for its offspring. Starch is com- 

 posed of innumerable tiny grains, contained 

 in the very small cavities with which the flesh 

 of the tuber is completely riddled. These 

 cavities are called cells. They are very small 

 receptacles formed of a fine membrane and 

 completely closed. They are filled with 

 grains of starch and pressed closely together, 

 making up the fleshy substance of the potato. 

 But these cells are so minute that we could 

 see nothing of them in the potato, however 

 closely we inspected it : a microscope would 

 be needed for their discovery. They are so 

 fine that in a fragment of potato the size of a 

 pin's head there is room for dozens and 

 dozens of them. In a potato of average size 

 there would be many millions. 



IOI 



