The Intake of Carbon 205 



3. The use of this kinetic energy in the decomposition 

 of carbon dioxid and water (H 2 O + C0 2 , or H 2 CO 3 ), the 

 synthesis of an elementary organic product, and the con- 

 sequent storage of potential or latent energy. 



4. The probable condensation of the synthate into a 

 carbohydrate of high food value, generally fruit sugar, 

 which is then often in part transformed into starch. 



5. The elimination, by gas exchange, of (X, a by-product 

 of the process (some of which, however, may be used in 

 respiration, subsequently treated). 



It is seen, therefore, that there is a physical mechanism 

 for gas exchange, a series of transformations of energy and 

 of compounds, and ultimately the deposition of food-ma- 

 terials, frequently starch. It is now necessary to consider 

 a method of demonstrating this process, and later there 

 will be required a further consideration of the course of 

 events, the factors involved, the energy transformations, 

 and some of the products resulting. 



111. The demonstration of photosynthesis. - - It is 

 possible to demonstrate photosynthesis in any plant more 

 or less completely by one or more of several methods, and 

 no single simple experiment will reveal all the facts desired. 

 With all other factors well controlled, 1 increase in weight, 

 or the accumulation of some organic product (especially 

 starch) are practicable demonstrations. Another type of 

 experiment involves, when accurate, an analysis of the 

 gas used, or that eliminated, or both ; but such eudio- 



1 The student who may pursue this matter farther should examine 

 carefully the difficulties and beauties of well-controlled experiments, 

 consulting Ganong's "Plant Physiology" (2d Ed.), pp. 79-114; also the 

 earlier account in Sachs. 



