68 THE BOOK OF NATURE STUDY 



If a Potato plant is carefully dug up without breaking the 

 branches, the relation of the Potatoes to the parent plant can be 

 seen. The tubers are situated either at the end of shoots which 

 bear scale-leaves, or on short branches arising in the axils of the 

 scale-leaves. Both of these are shown in the illustration. 



Root-tubers are also swollen, underground structures, but 

 their origin is different from that of the stem-tuber. They grow 

 out from the base of the stem, and are therefore of the nature of 

 roots. The Peony and the Dahlia have root-tubers. 



FIG. 40. Potato plant, showing Potatoes in different stages of growth. 



All these tubers are storehouses of food for the plant. If a 

 drop of iodine is put on a slice of a Potato, a dark blue stain is 

 at once produced. This indicates the presence of starch. When 

 good potatoes are properly boiled, they have a floury appearance, 

 owing to the bursting of the grains containing starch. 



In preparing " seed " potatoes, a well-grown potato should be 

 cut into as many pieces as there are " eyes " at the apex ; each 

 piece should contain one of the " eyes/' and should not be cut 

 too close to it, as the bud when growing into the plant requires 

 to draw nourishment from the tuber. A pound of potatoes will 



