12 PRINCIPLES OF AGRICULTURAL, CHEMISTRY 



tract some substance. Only the fourteen elements invariably 

 found in plants need be considered, and as two of these (hydrogen 

 and oxygen) are in the water, and one (carbon) is supplied from 

 the air, there remains eleven to be tested. Twelve solutions are 

 prepared. One contains all eleven elements, and is used as a 

 check. If the plant does not thrive in it, something is wrong 

 with the experiment. Each of the other solutions contain salts 

 of ten elements, one being left out of each solution. For ex- 



Fig. i. Buckwheat grown in complete nutrient solution (O) 

 and with Cl, K, etc., absent. 



ample, sodium is left out of one, potassium left out of another, 

 and so on. Seeds are germinated on moist filter paper, and the 

 strongest seedlings are supported by a cleft cork in the neck of the 

 bottle containing the nutrient solution, so that the roots are im- 

 mersed, but the cotyledons are above the surface. The plants 

 would probably die if the cotyledons were immersed. The vessel 



