The Manufacture of Food 47 



220 men for i day.^ This shows the great loss of energy that 

 results when plant foods are converted into meat before they 

 reach the human consumer. It is evident that as the human 

 family becomes larger and food becomes scarcer, we shall have to 

 take more and more of our foods directly from plants. 



There are, however, certain animals that feed, either directly 

 or indirectly, on plants that cannot be used for human food. 

 All of our sea-food animals, such as fish, clams, and oysters, are 

 able to convert otherwise unusable food into food that can be 

 used, thus adding much to our diet. Sheep and cattle grazing on 

 the open range and forest reserves in the Western states and on 

 the pampas of Argentina may be looked upon as gatherers and 

 converters into available forms of food not directly usable by 

 man. 



PROBLEMS 



1. How do the white parts of a variegated leaf get food? 



2. Occasionally in a field of young corn a stalk that lacks chlorophyll will be found. 



How long will it live ? 



3. Geraniums with variegated leaves occasionally produce branches that are en- 



tirely white. A noted horticultural firm offered $1000 to any one of its 

 gardeners who would root one of these branches and thus produce a white- 

 leafed geranium. What was the chance for success ? Why? 



4. Why do trees in the open retain their lower as well as their upper branches, 



while the same trees grown in a dense forest retain only their uppermost 

 branches? 



5. Why are there comparatively few weeds in a cornfield in the autumn as com- 



pared with an adjoining field in which wheat has been grown? 



6. Bushbeans cannot be grown profitably between rows of corn in a cornfield, 



but polebeans, if properly spaced in the field, will yield abundantly and not 

 interfere with the corn. Explain. 



7. Why is it best to wait until celery is well grown before tying it up with paper, 



or covering it with boards to blanch it? 



8. In how many ways could you cause a plant to starve to death? Are any of the 



methods used in controlhng weeds ? 



1 United States Department of Agricillture, Farmers' Bulletin No. 877. The 

 table does not take into account the necessity for using a variety of food substances 

 in our diet. Milk cattle return a larger proportion of food for human consumption 

 than the above statistics indicate. 



