HOW PLANTS ARE INFLUENCED 



327 



lying on a dry table -top, and will finally assume the 

 appearance 1 shown in Fig. 179. On comparing it 

 with a potato 

 grown under 

 normal con- 

 ditions, we 

 see that its 

 growth has 

 been exceed- 

 ingly slow 

 (the normal 

 Potato of the 

 same age is 

 a hundred or 

 more times 

 as large) , its 

 branches are 

 thick and 

 clumsy in 

 appearance, 

 with close- 

 ly crowded 

 nodes; 2 it 



1 A somewhat similar but less pronounced effect is produced by the action 

 of strong light, even when abundant moisture is present: in general, the effects 

 of light and dryness are closely similar. Fig. 180 shows the striking contrast 

 between potato sprouts which receive little water and abundant light, as com- 

 pared with those which receive abundant water but no light. In the latter the 

 nodes are further apart and the stem more elongated and much weaker than in 

 a normal plant, while the leaves are small and the whole plant of a pale color. 



2 The nodes are the places where leaves and buds appear on the stem. 



179. Potato which has been allowed to sprout and grow on a dry 

 table-top before a north window, showing Cactus-like habit. 



