116 



AGRICULTURE ON THE PACIFIC SLOPE 



conditions. It will be noticed that the whole appear- 

 ance is more like an ordinary plant than is the potato 

 plant shown in figure 63. This sprout was obtained 

 by taking a joint of prickly pear which was preparing 

 to sprout, placing it in a pot of sand, and setting this 

 inside a closed box to exclude the light. It was watered 



frequently, and 

 in the course of 

 about two 

 months produced 

 the sprout shown 

 in the figure. 



Plants under 

 dry conditions 

 expose less sur- 

 face to the air 

 because the dan- 

 ger of drying up 

 is so great. They 

 make their leaves 

 very small or get 

 rid of them altogether. A cactus shows this very well. 

 It has lost its leaves and has little exposed surface. 



Plants get rid of their leaves in winter because they 

 cannot get water enough during the cold weather. As 

 soon as the roots become chilled they cannot absorb 

 water. Cold irrigation water may chill the roots too 

 much, and it should be run on slowly in shallow basins 



FIG. 64. Branch of a potato grown under ordi- 

 nary conditions. 



