ABSORPTION OF GASES. 



37 



29. Photosynthesis. Green plants absorb carbon dioxide 

 from the air either through FIG. 32. 



the epidermis or the stomata. 

 Carbon dioxide is composed 

 of one part of carbon and two 

 parts of oxygen. The proto- 

 plasm which forms the mass 

 of the green color bodies 

 (chlorophyll bodies) in the 

 cells has the power, when it 

 receives the sunlight, of sep- 

 arating one part of the oxy- 

 gen which is thrown off as 

 a free gas, while the carbon 

 monoxide which remains is 

 combined with the water 

 present to form a compound 

 of carbon, hydrogen, and 

 oxygen from which sugar is 

 ultimately derived. The en- 

 tire process may be desig- 

 nated photosynthesis. No 

 life is imaginable without 

 photosynthesis. All organ- 



. Diffusion of gas through epidermis. 



isms, plants, and animals /, level of mercury column 20 days 



alike are ultimately depend- 



ent upon the products of centimeter-scale. 



this process for their carbon compounds. 

 EXPERIMENT 43. 



THE ACTION OF LIGHT IS NECESSARY FOR PHOTOSYNTHESIS. 



Weigh 4 seeds of Corn, germinate and grow in nutrient solution. 

 Place 2 of the seedlings in a dark chamber and the remaining 2 in 

 the sunlight. In three weeks take the plants from the solutions, dry 



