PLANTS INFLUENCED BY THEIR SURROUNDINGS 115 



All this is just what we see in desert plants; in fact 

 the whole appearance of this plant reminds us of a cactus. 



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FIG. 63. Potato which has been allowed to sprout and grow on a dry 

 table top before a north window. It resembles a cactus. 



On the other hand, we may, by growing a cactus 

 in the dark, with plenty of moisture, cause the spines 

 to grow out into leaflike organs. Figure 65 shows a 

 sprout which has grown from a prickly pear under these 



