SECTION I. 



RELATION or PLANT TO ANIMAL LIFE AND CHEMICAL 

 ELEMENTS NEEDED BY PLANTS. 



How Plants Feed. — Every seed is made up of a germ (em- 

 bryo plant) surrounded by stored up food. When a seed is 

 dropped into the warm soil it germinates and feeds on this stored 

 up food material until it has put forth a root, stem and leaves. 

 It is now able to gather its food from the air, water and soil. 

 On the roots of plants are minute root hairs, composed of 

 single cells, which absorb food materials from the soil water, 

 by means of osmosis or diffusion. The leaves, on the under 

 sides, have minute openings which permit the breathing of air 

 which contains carbonic acid gas. The carbon is used in build- 

 ing up the plant and the excess of oxygen is given back to the 

 atmosphere. This process requires the presence of light as does 

 chlorophyll (green coloring matter of plants). Plants will grow 

 without light as long as the food supply in the seed lasts, but 

 they will be white and will not produce seed. By the aid of 

 sunlight the materials gathered by the root hairs and leaves are 

 manufactured into compounds and retained by the plants. 



The Food of the Plant. — The plant keeps growing until it 

 produces seed. It may continue its growth for years as is the 

 case with trees. In this continual growing process we cannot 

 see the plant feeding but we know its nourishment is obtained 

 from the soil, water and air. The food of the plant, then, con- 

 sists of the mineral substances, water and gases taken from the 

 soil and air. 



The Food of the Animal. — The plant takes its food from 

 mineral substances, water and gases and changes these materials 

 into many compounds. These compounds are stored in the 

 plant and are in a form suitable for animals and constitute their 

 food. The animal feeds on the plant and changes plant sub- 

 stances into bone, flesh and blood. If the animal is deprived of 

 the plant it dies. Therefore we know that the plant is necessary 

 for the existence of the animal and constitutes its food. 



