CULTIVATED FRUITS 



In the Hickory Nut the "shuck" probably 

 consists partly of calyx and partly of consoli- 

 dated bracts of involucre; when the fruit is ripe 

 it opens and releases the nut. In the Walnut 

 and Butternut the "hull" is probably of the 

 same origin as the "shuck" of the Hickory, but 

 it does not split open as it ripens. It remains 

 fleshy, and the nut is usually removed by drying 

 the cover. It has been discovered that the 

 charcoal made by burning the shells of nuts, as 

 well as the pits of stone-fruits, makes the best 

 absorbent of poisonous gases yet known. 



175 



