45 



any opaque body, while the generaUty of 

 plants are turned from the opaque body 

 toward the hght. The whole of a plant 

 kept in a room will grow towards the 

 w^indow. But though this principle is not 

 so striking out of doors, it is perpetual and 

 universal. 



As the light falls equally on the leader 

 of a tree it goes up straight. In proportion 

 as it intercepts the light from above, the 

 branches grow towards the light at the 

 sides ; and if one outstrips its neighbours, 

 the light from above turns its end up. If 

 the lower tier of branches outgrows the 

 tier above it, in turning up, it will take 

 its neighbour with it. That tier will 

 turn the tier above ; and so in succes- 

 sion all the branches will grow upward. 

 This growth is often seen in beech trees. 



It is this principle which prevents the 

 boughs of a tree from growing against one 

 another. In proportion to their opacity 

 they grow one from the other. 



