14 MAN ON THE LANDSCAPE 



gasoline and lubricants can be got from it by hydrogenation. But 

 the high grade, low priced portion of our coal deposits is noticeably 

 shrinking. 



When the hydrocarbons do become scarce and expensive, we may 

 be forced to turn to carbohydrates, forced to use sun energy which 

 green plants can imprison from year to year, crop by crop. (This 

 would present a staggering problem because the world's soils today 

 are not even feeding, clothing or sheltering its population decently.) 

 The use of direct sunlight, concentrated by some scientific marvel and 

 changed into a transportable form, offers future possibilities. It also 

 offers almost insuperable practical difficulties. Science will probably 

 be able to use the enormous energies of atoms as a source of controlled 

 power. This could perhaps give us a higher standard of living. Water 

 power cannot supply more than a fraction of our energy needs. 



Carbohydrates in the form of starch, sugar, and cellulose, for the 

 powering of the earth 's animal population must continue to come from 

 plants. Science to date has not made more than a dent in the problem 

 of duplicating the process which plants use in making carbohydrates. 

 There is at present no glimmer of hope that we shall ever be able to 

 live without plants. 



Fats are also energy sources, and are basically carbonaceous. Sugar 

 is their foundation. The energy residing in plant and animal oils is 

 derived from sunlight sunlight acting through plants on raw ma- 

 terials from atmosphere and water. The oil of the castor bean was 

 used to lubricate airplanes in the First World War. No petroleum 

 product was then good enough. Today better mineral lubricating oils 

 are available. Our machine civilization could operate on plant oils, 

 and may be forced to do so some day. This will mean that vastly more 

 plants will be needed. Instead of gasoline we may find it necessary to 

 use an alcohol, derived from carbohydrates, e.g., from potatoes, grain, 

 wood. And again plants in the mass will be called for. These possi- 

 bilities, if we may speak parenthetically, offer a very sound argument 

 for conserving and keeping productive every acre of soil in the world. 

 And in order that such a burden be kept from our soils as long as 

 possible, the life of mineral fuel and power supplies should be pro- 

 longed by every known means. 



Green Food Factories. Of all the physiologic processes which 

 occur, that of photosynthesis is, in a sense, most important. Without 

 it there could be no plants, no animals, no human race. The only logi- 

 cal challenger to the importance of this primary process could be the 

 reverse action, respiration (a form of combustion) which takes place 

 in cells. By respiration, the sun energy concentrated by the green 

 plant into carbohydrate is reconverted again into energy, to appear 

 finally, for one thing, as all the works of man. Toward maintaining 

 these processes all other physiologic activities of plants are pointed. 



It is not out of place to review here one of the greatest mysteries 

 confronting man: how green plants make food. If and when science 

 discovers just how chlorophyll does this job, we may know the secret 

 of life. What we know is this : In certain plant cells are bits of matter 



