The Food of Plants 



and oxygen. 1 

 nitrogen, and 



Potassium, 

 phosphorus 



H'. T. Shilling 



FIG. 12. A pupils' collection of 

 samples of the necessary plant-food 

 elements. 



are the elements most likely 

 to be deficient in any soil, 

 and therefore they are the 

 ones most needed as ferti- 

 lizers (Fig. 12). 



The plant takes all of its 

 carbon and some of its oxy- 

 gen from the air. All the 

 rest of its essential food 

 materials, including water, 

 it takes through its roots 

 from the ground. (Exp. 3.) 

 In Figure 13 each of the 

 side roots is shown absorb- 

 ing one of the food materials, and the taproot, collecting 

 water. Of course, every root absorbs all of these, but 

 the picture is made in this way to aid the memory. 

 The other essential food material, carbon, is shown 

 coming to the leaf from the air. 2 



However necessary the food elements from the soil 

 may be to a plant, water is still more necessary, for 

 mineral matter cannot be absorbed, except in solution. 

 It must be dissolved in water before it can be drawn 

 through the thin membranes of the root hairs. Not 

 only does water carry food materials from the ground 



1 The first four substances named are metals ; the second four are 

 non-metals ; and the last two are the elements of which water is composed. 



2 The water, carbon dioxid, and minerals that a plant uses are not 

 foods. They are the raw materials from which the plant manufactures 

 the foods that it needs. 



How both 

 earth and 

 air furnish 

 food 

 materials 



Water a 



food mate- 

 rial and a 

 carrier of 

 food 



: 



