The Origin of Life and Photosynthesis 109 



per acre per day of nine hours' sunshine. This would be sufficient to 

 produce about one ton of carbohydrate material from carbon 

 dioxide, on the basis of the best efficiency which is reached in labora- 

 tory experiments. Actual agricultural operations do not approach 

 this degree of efficiency. The average yield of agricultural produc- 

 tion is not more than two tons per acre per year,^ which is clearly 

 very much less than the optimum obtainable from a plant under ideal 

 conditions. There are of course many reasons why oiily a small frac- 

 tion of the photosynthetic energy of sunshine is actually utilized in 

 practice, but it is clear that in sunshine, particularly in the tropics, we 

 have a source of energy and of synthesis far exceeding all other 

 sources, such as coal, oil and atomic energy, and the photosynthetic 

 apparatus of green cells is remarkably well adapted to its utilization 

 to make a host of compounds. 



^ The data given here are taken from an article by F. Daniels in Holloender's 

 Radiation Biology, Vol. III. 



