CONDITIONS AFFECTING GROWTH IT 



ing the excess moisture to escape and the warm air 

 to penetrate to a greater depth. It must be remem- 

 bered that oxygen is as necessary to the healthy 

 growth of these plants as it is to the animal. The 

 cells of the newly formed roots are filled with that 

 life-giving principle called protoplasm, and they 

 must have access to the oxygen of the air or they 

 will soon die. 



The late Prof. E. S. GofT 1 illustrates this in this 

 way: Take a quantity of water and boil it for a 

 time, so as to expel the free oxygen and then cool 

 it quickly. A portion of it is then placed in a glass 

 and oil is poured over it, so as to prevent the re- 

 absorption of air. Leave the remainder exposed to 

 the air for some time until it has reached the nor- 

 mal condition. Now take cuttings from some free- 

 rooting plant, like the geranium or tomato, and 

 insert one into each of the glasses. In the glass con- 

 taining the oil over the top the cutting will soon die, 

 because there is no free oxygen in the water, while 

 the one in the other glass, which has been left ex- 

 posed to the air, will soon send out its rootlets and 

 continue to grow. 



Or, take the same kinds of cuttings and place 

 them in a soil where the free water is within six 

 inches of the surface. Make the cuttings long 

 enough so that the lower ends will extend down 

 into the free water. It will be found later on that 

 the cuttings will have thrown out roots above the 

 water level, but not from the ends which were in the 

 soil which was saturated with moisture and conse- 

 quently devoid of free oxygen. 



1 "Principles of Plant Culture." 



