THE FOOD OF THE PLANT 



43 



The relation that exists between a plant and the 

 surrounding air can now be dealt with. Answers to 

 the following questions will be sought. 



Does a plant get any food from the air ? If it does, 

 what is the nature of the food taken, and under what 

 conditions is it obtained ? 



II. THE ABSORPTION OF POOD FBOM THE AIR 



Experiments dealing with the absorption of food 

 from the air are more difficult than those connected 

 with absorption from the soil, because invisible gases 

 are here bemg dealt with. 



A few preliminary experiments will be made. 



Experiment 24 



Aim. — To find out whether 0,ir can pass from the 

 atmosphere into and through a leaf. 



Method. — A piece of straight glass-tubing drawn out 

 to a point at the lower end and a piece 

 of glass-tubing bent at right angles are 

 put through a two-holed cork. The 

 cork is then fitted into a conical flask 

 or a bottle partly filled with water. 



In the upper end of the straight tube 

 a stout leaf is fixed ; a laurel leaf is a 

 suitable one for the purpose. 



A piece of rubber-tubing with a clip 

 is attached to the end of the right- 

 angled tube. 



The junction between the leaf and 

 the tube and all the joints in connec- 

 tion with the cork are then made air- 

 tight (Fig. 20). 



If a big succulent leaf such as a 

 funkia can be obtained the apparatus may be set up 

 more simply. In this case the straight glass-tube can 



Fig. 20 



