The Living Machine 297 



machine finds a parallel in the storage of electrical energy 

 in a storage battery. 



Turning from the world of animals to that of plants, we 

 find in the latter a parallel to all of the metabolic processes 

 of the former. The average person is accustomed to think of 

 a plant in terms of the green thing which he finds in garden, 

 field or forest. But when we go a-hunting mushrooms, or 

 poke aside the rotting remains of a fallen tree, we discover 

 other plants which live a different sort of life from that of 

 tree or shrub or herb. And should we delve yet further into 

 Nature's recesses, and penetrate that hidden world to which 

 the microscope gives entrance, we should discover creatures 

 concerning whom no one can say whether they are plant or 

 animal. Some of these uncertain forms are claimed by both 

 botanist and zoologist as belonging in their own especial field 

 of study, for in some respects they are distinctly animal, in 

 others plant in nature, as we have already seen in an earlier 

 chapter. But while one stands at the portals of life in a 

 realm which is neither plant nor animal ; advancing into either 

 kingdom he must follow ever more widely diverging paths; 

 until when he reaches the farthest bounds of this wonderful 

 world he finds its two kingdoms, while governed by the same 

 fundamental laws, nevertheless differing profoundly in their 

 expression. 



Perhaps the most fundamental difference between the higher 

 plants and animals is in their metabolism. "While the latter 

 are spenders, the former are hoarders of energy, taking raw 

 materials, carbon dioxide from the air and water from both 

 air and soil, and from these constructing by the energy of the 

 sun, acting through the green chlorophyl of leaf and stem, 

 their own food-stuffs; thereby converting the radiant energy 

 of sunlight into the chemical energy of sugar and of starch. 

 From the soil and air the plant obtains its nitrogen, and from 

 the soil the other inorganic substances which it needs to build 

 its protoplasm, and combining these in some as yet but little 

 understood way, with the sugar, by the action of constructive 

 ferments, it builds up its protoplasm. This is what is hap- 

 pening in the blade of grass, the spreading leaf and the stag- 

 nant pool, covered with a thick green scum, a little chemical 

 laboratory, where Nature is busily at work making sugar and 

 releasing oxygen. Some day perchance the chemist, imitat- 

 ing Nature, will learn to make our starch and sugar for us, 

 and bid defiance to the "man with a hoe." This indeed is 

 the possibility, perhaps not immediate, but none the less ulti- 

 mate, of the studies on photosynthesis now under way at the 

 Desert Botanical Laboratory of the Carnegie Institution at 



