124 TILLEES OF THE GEOUND CHAP. 



it may be said that we eat so many different kinds 

 of things that wheat only plays a subordinate part 

 in our diet. But if we think for a moment we 

 shall see that bread forms part of all our meals, 

 and though bread and water is not a diet that we 

 should care to live on for long, yet we know that 

 it is possible to live on it for a time. 



The geologist, Hugh Miller, who from being a 

 poor quarryman rose to be a great man of science, 

 tells us, in the story of his life, that when he was 

 a journeyman he and his companions lived entirely 

 on oatmeal, in the form of porridge and oatcake. 

 So long as they could get milk to take with their 

 porridge they were quite content; it was only when 

 the milk -supply failed, and they had absolutely 

 nothing but the oatmeal, that they felt themselves 

 a little hardly used. The fact that they did live 

 upon it, however, shows that the seeds of the oat- 

 plant, without anything in addition, can supply 

 man with the three necessary food substances, though 

 they are poor in fat. 



But though seeds furnish probably the most 

 important part of man's vegetable food, yet some 

 kinds of roots and underground stems are also very 

 important. We saw before that yams, which are 

 the underground stems of plants distantly related 

 to our leeks, form the chief food-supply of some 

 kinds of African negroes. Similarly, potatoes are 



