ABSORPTION OF GASES. 



37 



29. Photosynthesis. Green plants absorb carbon dioxide 







from the air either through FlG 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 

 1-1 i, , 1 j j after beginning of experiment ; O, 



alike are ultimately depend- skin O f grape ;7\ sealing-wax ; A 



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 



