144 TALKS AFIELD. 



ing in the structure of stem or root, so far 

 as we know, which would cause either of 

 them to take a special direction. To be 

 sure, the roots seek the earth to secure food 

 for the plant, but that fact does not explain 

 how they are enabled to practice such dis- 

 crimination. It may be that gravitation has 

 something to do with this downward ten- 

 dency of the root, as many botanists have 

 supposed, although it is difficult to see why 

 the stem should not be similarly influenced ; 

 and, moreover, it sometimes happens that 

 roots grow upwards in search of food. Af- 

 ter all that has been said and done about 

 the reasons for the downward direction of 

 roots, we are forced to say that we do not 

 know what makes them enter the earth, any 

 more than we know what makes some seeds 

 germinate slowly and others rapidly; we 

 can do no more than to adopt a name which 

 has been given to the phenomenon by bota- 

 nists. This name is Geotropism^ from the 

 Greek for earth and to turn. 



Another distinction between stem and 

 root is the absence from roots of all forms of 

 leaves and buds. This distinction will ena- 

 ble us to distinguish between true roots and 

 certain underground stems which are root- 



