PRODUCTION OF NEW VARIETIES. 441 



genus and nearly related, but hybrids between 

 them have never been produced. Neither have 

 any ever been obtained between the apple and the 

 pear, or the pear and quince. But different species 

 of other plants, as of the Heaths, and some of the 

 Cacti, intermingle freely. The Rhododendron will 

 fertilize the Azaleas, and the Red Cedar has 

 been made to inoculate the American Arbor-vitse, 

 though both these examples are between plants of 

 different genera. 



