WHERE FOOD COMES FROM 121 



bodies of living things or in a flame. Thus we may see that all the en- 

 ergy which plants and animals use as a result of the oxidation of carbo- 

 hydrates is derived from the sun's energy. There is more than poetry in 

 the statement that every human act is a transformed sunbeam. 



WHERE FOOD COMES FROM 



1. Organic matter is constantly being destroyed 



Through oxidation in protoplasm 



(Through decay) 



(Through fire and industrial processes) 



2. Organic matter is constantly being made anew 



Primarily 



Through photosynthesis 



Material : water ( H._,0) ; Energy : sunlight 



carbon dioxid (CO^) Product; carbohydrates 



Instrument: chlorophyl By-product; oxygen 



Secondarily 



Through transformation of carbohydrates 

 By plant and animal protoplasm 

 Into fats ; into proteins 

 Through assimilation of nutrients (proteins, fats, and carbo- 

 hydrates) 

 By plant and animal protoplasm 



Into substances peculiar to the different species of plants 

 and animals 

 Through (other) chemical processes of protoplasm 



Into substances peculiar to the activities of different species 

 of plants and animals 



3. Structure and activities of chief food-producers (seed plants) 



The leaf 



General character 

 Origin 



From stem (From buds) 



Epicotyl 

 Cotyledon 

 Different forms (compare also parts of flower) 

 Structure 

 Epidermis - Pulp (chlorophyl-bearing cells) 



Stomates Palisade layers 



(Hairs) ; (Wax) Spongy (air-space) layers 



