138 3Botani2 



plant receives food from earth, water, air. The 

 earth gives the plant sulphur, iron, soda, magnesia, 

 phosphorus, and other mineral substances which 

 we have before noted. These are all offered to the 

 l^lant, held in solution in water. AVe are sure of 

 this, because the food must pass into the cells, the 

 cells have walls, and only water, with what is held 

 in solution that is changed to a liquid state in water, 

 can pass through the cell walls. We knoAV that 

 these mineral substances are carried into the plant, 

 changed and become a part of it, because when a 

 plant is burned, destroying its moisture, these min- 

 erals can be taken again from its ashes. 



From water the plant receives as food hydrogen 

 and forms of ammonia. From air the plants absorb 

 carbon (dioxide), oxygen, nitrogen, and ammonia; 

 very much of the first, little of the second, and very 

 little of the others. 



Plants seem to be as foolish as some people, in 

 that they will absorb from the air very poisonous 

 elements, which destroy them. AVhen plants grow 

 out of doors the winds, dews, and rains free the 

 leaves from accumulations of dust which obstruct 

 the pores and hinder the receiving of food. In very 

 dry and dusty seasons we notice that the plants be- 

 come sickly from the stopping of the pores. Plants 

 need clean skins as human beings do. House plants 



