84 SILOS, ENSILAGE AND SILAGE. 



and animal life. From the farmer's standpoint his field 

 crops may be looked upon as machines for making food 

 for animals from inorganic materials which the animals 

 could not otherwise make use of in their nutritive pro- 

 cesses. 



In order to obtain the largest possible returns from 

 these living plant machines, they must be made to work 

 to their full capacity, under conditions that are the most 

 favorable for the exercise of their special endowments. 

 They must have an abundant supply of the raw materials 

 required in making organic substances, and of energy, in 

 the form of light, and heat from the sun, to be expended 

 in the work of construction they have to perform. Any 

 deficiency in either of these essentials (inorganic raw 

 materials, and energy) must detract from their efficiency 

 as machines in the work they have to do. 



The resulting products of these plant machines, which 

 we call organic substances, as starch, sugar, fat, proteids, 

 etc., are not only food for animals in the sense that they 

 furnish materials for building animal tissues, but, what 

 is quite as important, they are also stores of potential 

 energy that is liberated and made active in doing work in 

 the constructive processes of the animal economy. 



One of the indications that these plant machines have 

 performed the full measure of useful work they are capa- 

 ble of doing, is the store of reserve materials provided for 

 future seed formation, as in the bulbs of our root crops, 

 or the actual formation of seeds, as in the cereals, to 

 provide for the future reproduction of similar machines. 

 In other words, seed formation, or provisions for seed for- 

 mation, marks the summit or limits of the profitable 

 work which plants can do in the manufacture of food for 

 animals ; and the farmer will find his interests are best 

 subserved by keeping up, or allowing these activities to 

 continue, until the limit is at least nearly reached. Im- 

 maturity in plants, therefore, implies unfinished, imper- 



