88 LUTHER BURBANK 



ways been; and that it is necessary to cultivate 

 different varieties of plants in order to gain the 

 diverse products that man needs or desires as 

 food or as aids in the industries. 



The particular product that a hop vine grows, 

 and in the production of which it has an absolute 

 monopoly, is used, as everyone is aware, mostly 

 in the process of the manufacture of beer. 



No product has been found that makes a satis- 

 factory substitute for the bitter principle sup- 

 plied by the lupulin of the hop. 



The particular place in which the hop vine 

 stores this bitter alkaloid, once it has manufac- 

 tured it, is the curious conelike leafy seed case 

 or envelope of the pistillate flower. Without 

 doubt the plant develops this bitter principle and 

 stores it there to give the seeds protection from 

 the depredations of animals. But whatever its 

 purpose, the bitter alkaloid provided by the hop 

 was discovered at an early date to have value 

 for the purposes of the brewer, and the hop vine 

 continues to be grown in large quantities solely 

 for the production of this alkaloid. 



The hop vine belongs to that somewhat 

 numerous tribe of plants that grow the pistillate 

 and staminate flowers on different vines. It 

 is only the pistillate flower that is of value to the 

 hop grower. But a few staminate flowers are 



