PLANTS INFLUENCED BY THEIR SURROUNDINGS 117 



so as to be warmed before it reaches the roots. 

 Otherwise the fruit and even the leaves may drop off. 



Nothing is more important than to give the plant 

 all the water it needs. But of course the soil should 

 not be kept too wet, 

 for this drowns the 

 roots, which need air 

 as much as any other 

 part of the plant. 



Other things being 

 equal, the amount-.of 

 a crop depends directly 

 on the amount of water 

 it gets. This we have 

 learned by long ex- 

 perience and very care- 

 ful experiments, and it 

 agrees with what has 

 already been said (on 

 page 89) about growth. 



Light. The effects 

 of light are much like 

 those of dryness and 

 go with them; for in dry places the light is usually 

 intense. Some leaves avoid intense light by growing 

 in a vertical position (eucalyptus, figure 40, acacia). 

 Young leaves are very sensitive to the light, and are 

 protected in a variety of ways, usually by their vertical 



FIG. 65. Sprout of prickly pear grown 

 in the dark, showing leaflike organs. 



