236 LUTHER BURBANK 



produce by splitting themselves into two or more 

 individuals. In this subkingdom live the death- 

 dealing bacteria, which bring about such human 

 diseases as tuberculosis and malaria, or such 

 plant diseases as black rot; and our helpful bac- 

 teria, too, which are everywhere helping us to 

 digest our food, and without whose help the 

 higher subkingdoms of plant life could not exist ; 

 and other plants of the same grade. 



The next subkingdom, higher by a step, in- 

 cludes the yeast which we use to raise our bread, 

 or those microscopic vegetables which turn hop 

 juice into beer, apple juice into cider; and others. 

 Those who prefer to chart seven subkingdoms 

 instead of six, divide this branch into two, making 

 the slime molds a separate phylum. 



The next subkingdom, ascending the scale, in- 

 cludes, among others, the mosses and liverworts. 



From these it is but a step to the next sub- 

 kingdom, which includes the ferns — the highest 

 type of flowerless plants, and the first, in the 

 ascending scale, to exhibit a complete develop- 

 ment of root, stem, and leaf. 



The final subkingdom, and the one into which 

 our work principally takes us, embraces those 

 plants which produce seeds. 



Taking, then, this latter, the highest sub- 

 kingdom, we find that it separates into two broad 



