CHEMICAL ELEMKXTS NEEDED RV PLANTS 5 



plants). The color of soils (red and yellow) are chiefly due to 

 the presence of iron compounds. 



Chlorine is most commonly found as chloride (common salt). 

 It also occurs in combination with hydrogen, as hydrochloric acid. 



Magnesium. — This element is found in most rocks and soils 

 in sufficient amounts for the needs of the plant. It is used in 

 different parts of the plant but mainly in the formation of seeds. 



Sodium. — Chloride is the commonest compound of this ele- 

 ment and is present in common salt, sea water, salt lakes, and 

 in many springs and waters. It occurs in sodium carbonate and 

 sodium nitrate ; the latter compound is a valuable fertilizer be- 

 cause of its nitrogen content. Sodium is believed to be helpful 

 in plant growth. 



Aluminum. — This element is the most widely distributed next 

 to oxygen and silicon of the earth's crust. /Vbout one-twelfth of 

 the earth's crust is aluminum. In combination it is found in clay, 

 slate, kaolin, etc. Although it is very abundant it is not used 

 much by plants. 



Manganese occurs in combination as manganese blend, man- 

 ganese spar, manganite, etc. Plants use this element in small 

 amounts although it is not believed to be necessary for plant 

 growth.* 



How Plants Feed.^ — Every seed is made up of a germ (embryo 

 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 con- 

 tains carbonic acid gas. The carbon is used in building 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 



1 Much of the remaining portion of this chapter has been taken from Halligan's 

 Elementary Treatise On Stock Feeds and Feeding. 



