Figure 46. A sick potato that has a disease, the potato wart, 

 which not only renders the potato unfit for food but which will 

 also destroy it. Bureau Plant Industry. 



Figure 47. Photograph of a sprurt 1 1 1 1-, the ri)u;s ot which 

 have been partly undermined by the water. As a result the tree 

 blew over but was not entirely freed from the soil. As it con- 

 tinued to live in this unusual position, the tip of the trunk turned 

 upwards and two of the limbs became tree-like in their sym- 

 metrv. Some idea of the extent of the adaptation i> gained by 

 comparing the unchanged limbs with the two that look like young 

 trees. This experiment took place in nature uninriuenced by man. 



