ii8 BOTANY FOR BEGINNERS CHAP. 



The elements which are found in the ash of a plant are said to 

 form the incombustible elements of the plant. 



The Essential Chemical Elements of Plant Food. 

 The elements which are essential for the life of a green plant 

 are ten in number. They are as follows : 



Carbon Phosphorus 



Hydrogen Potassium 



Oxygen Calcium 



Nitrogen Magnesium 



Sulphur Iron 



Water Culture. The relative importance of the elements 

 given above to the life of plants can be ascertained by the 

 method of water culture. The plant is grown in distilled 

 water in which certain salts have been dissolved. If the solution 

 contains everything necessary for the growth of the plant, it is 

 said to be a normal solution. By varying the salts in the 

 solution in a number of experiments, and observing the effect 

 produced upon the plants, we can draw certain conclusions as 

 to the needs of plants. 



The following can be taken as an example of a solution for water 

 culture : 



Distilled water I litre. 



Potassium nitrate I gramme. 



Sodium chloride \ ,, 



Calcium sulphate ,, 



Magnesium sulphate \ ,, 



Calcium phosphate i ,, 



A few drops of a dilute solution of iron chloride should be added. 



Seeds of any quick growing plant, such as Maize, Bean, Pea, or 

 Buck-wheat, are germinated on damp saw-dust, and when the 

 radicles are well-developed, the seedlings are washed in distilled 

 water. A series of bottles with wide mouths are prepared, and 

 the corks which fit the bottles are suitably split. The seedling 

 is then placed in the split made in the corks with its roots 

 hanging in the solution. A different solution is placed in each 

 bottle. In one a normal solution is used as a test of the growing 

 power of the others. If, for instance, the plant is grown in a 

 solution which contains all the essential elements except iron 

 the plant is of a pale yellow colour, because iron is necessary 

 for the development of chlorophyll. If a mere trace of iron is 



