94 



BOTANY 



matters are taken in far in excess of the immediate needs of the 

 plant. Such minerals are stored in the stem and leaves. 



Need of Mineral Matter for Growth. — Plants will not grow well 

 without certain of these mineral substances. This can be proved 

 by the growth of seedlings in a so-called nutrient solution. Such a 

 solution contains all the mineral matter that a plant uses for food.^ 



Mineral Matter necessary for Growth of Young Plants. — Obtain three 

 jars ; put distilled water in one, nutrient solution (without ferric chloride) 

 in another, and nutrient solution plus ferric chloride in the third. Place 

 germinating corn or bean seedlings in the jars so that roots extend down 

 into the liquids. Observe the growth of the three lots of seedhngs. Decide 

 which of the three jars is most favorable to growth. 



Nitrogen in a Usable Form necessary for Growth of Plants. — We 



learned that humus is made up of decayed plant and animal 

 bodies. A chemical element needed by the plant to make proto- 

 plasm is nitrogen. This element cannot be taken from either soil 



water or air in a pure state, as is the case with 

 the other chemical elements used by the plant 

 in the manufacture of protoplasm. Nitrogen is 

 usually obtained from the organic matter in the 

 soil, where it exists with other substances in 

 the form of nitrates. Nitrogen is found in such 

 form in all decaying material ; hence the use of 

 fertilizers.^ 



Relation of Bacteria to Nitrogen. — It has 

 been known for a long time that clover, peas, 

 beans, and other legumes, cause the ground to 

 become more favorable for growth of other plants. The reason 

 for this has been discovered in late 3^ears. On the roots of the 



^ A nutrient solution may be prepared as follows : — 



Distilled water (H2O) 1000.00 c.c. 



Potassium nitrate (KNO3) 1.00 gram 



Sodium chloride (NaCl) 0.50 gram 



Calcium sulphate (CaS04) 0.50 gram 



Magnesium sulphate (MgS04) 0.50 gram 



Calcium phosphate (Ca3[P04]2) 0.50 gram 



Ferric chloride (FeCls) 0.005 gram 



(Do not put the ferric chloride into the solution in the first place, but add a drop 

 of it to each bottle wlien the seedlings are put in.) 



^ Other important plant foods found in soil, but which are frequently used up by 

 plants growing therein, are potash and phosphoric acid. Both of these substances 

 are made soluble so as to be taken in by the root by the action of the carbon dioxide 

 in the soil. 



Bacteroids forming 

 from filamentous 

 structures in the 

 cells of a root. 



