CHAPTER IV 



PLANT FOOD 



"I dropped a seed into the earth. It grew, and the plant was mine. 

 It was a wonderful thing, this plant of mine. I did not know its name, 

 and the plant did not bloom. All I know is that I planted something 

 apparently as lifeless as a grain of sand and that there came forth a 

 green and living thing, unlike the seed, unlike the soil in which it 

 stood, unlike the air into which it grew. No one could tell me why it 

 grew, nor how. It had secrets all its own, secrets that baffle the wisest 

 men; yet this plant was my friend. It faded when I withheld the light, 

 it withered when I neglected to give it water, it flourished when I sup- 

 plied its simple needs. One week I went away on a vacation, and 

 when I returned the plant was dead; and I missed it." 1 



56. Elements Required for Plant and Animal Growth. 2 

 Of the seventy different chemical elements, only thirteen 

 are usually found in plants and animals. These elements 

 are: 



Oxygen Calcium 



Hydrogen Magnesium 



Nitrogen Iron 



Carbon Chlorin 



Sulfur Sodium 



Phosphorus Silicon 



Potassium 



Only the first ten of these are considered necessary 

 for plant growth, but the last three are always found in 

 plants, and may serve some useful purpose. Manganese 

 and one or two other elements occur, but are not essential. 



'L. H. Bailey. Junior Naturalist Monthly. February, 1903. 

 3 If the class lias not studied chemistry, a few elementary lessons on 

 this subject should precede this chapter, see manual. 



(60) 



