FIG. 50. An English ivy (Hedera) grown in front of a south window 



WW, the line of the window casing ; all to the right of this is unlighted wall. The 

 tips of the shoots (t) avoid the light ; the young leaves (I) have assumed no defi- 

 nite position ; the mature leaves are nearly at right angles to the light coming 

 from the direction of the arrow ; r, aerial roots 

 63 



