32 



THE AMERICAN NATURALIST 



[Vol. XL 



slender. At a distance of 15 cm. from the ])lant one of the largest 

 of them was 7.6 mm. in diameter, and one meter from the plant 

 it was 4.6 mm. in diameter. The roots ran abont 6 cm. below 

 the surface, in places which were free of stones, but when a stone 

 was encountered the root dipped beneath it and availed itself of 

































































































































































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the better water supply to be found there. The most deeply 

 placed root, however, was not more than 10 cm. below the surface 

 of the ground. There are therefore two noticeable characteristics 

 of the root system of Echinocactm wisUzeni, namely, the roots 



