ESSENTIALS OF PLANT U?E II 



the quantity of ash in the seed planted. Hence the plants did not 

 create any ash, and the ash gained in the previous experiment 

 must have come from the sand. This work is an example of the 

 importance of continuing experiments until only one possible 

 conclusion is indicated, and also shows the danger of formulating 

 conclusions upon insufficient data. 



The plants in the platinum dish after reaching the height of 

 only two or three inches, began to turn yellow, and died. This 

 showed that the ash in the seed was sufficient for only a limited 

 development of the plant, and, taken in connection with the pre- 

 ceding experiment, showed the mineral matter was necessary 

 to the growth of plants. 



Finding the Essential Elements. An essential element is an 

 element whose presence is absolutely necessary to the full growth 

 and maturity of the plant. A useful element, though not essential, 

 may be serviceable to the plant. 



The following fourteen elements are invariably present in 

 plants : 



The eight non-metals: carbon, hydrogen, oxygen, nitrogen, 

 phosphorus, sulphur, silicion and chlorine. 



The six metals: potassium, calcium, magnesium, iron, sodium 

 and manganese. 



Other elements are sometimes found in plants. 1 Iodine occurs 

 constantly in sea-weeds and sponges, being present as an organic 

 compound in the latter. It is prepared from the ash of sea-weeds. 

 Fluorine, arsenic, boron, rubidium, bromine, lithium, barium, 

 aluminum, thallium, lead, zinc, titanium and copper have also 



Water Culture Experiments. Experiments to ascertain which 

 been found in plants, in minute quantities. 



elements are essential or useful to plants are made by growing 

 plants in pure water, to which the salts to be tested are added. 

 This is known as the water culture method, and is used because it 

 is comparatively easy to secure pure water and salts, but almost 

 impossible to secure a sand or soil from which plants do not ex- 



1 Jahresber. Agr. Chem., 1864, pp. 94, 99, 159; 1866, p. 121. Exp. Sta. 

 Record 3, p. 717; 7, p. 643. 



