34 CHLOROPHYLL 



not incessantly performed by green plants — a power which 

 chlorophyll and chlorophyll alone confers on them — all carbon 

 must pass from the reach of the organic world and living 

 matter come to an abrupt end." Thus it comes about that 

 animals are ultimately and absolutely dependent for their 

 complex food on the green colouring matter of plants. Carni- 

 vorous animals are in the end dependent on herbivorous 

 (plant-eating) animals, and thus both are dependent on the 

 food which the plant has built up, not only for the increase in 

 their bulk but for the energy which enables them to live and 

 move and have their being. It is chlorophyll which "makes 

 the world go round." If anything went wrong with this 

 green substance — and it might — the whole of living creation 

 would soon cease to be and the world become as dead as the 

 moon is. 



The fact that a plant is bathed in its food, as a baby would 

 be if it were immersed in a bath of milk or beef tea, renders 

 it important that it should expose as much of its surface as 

 possible to the circumambient nutriment. Hence, leaves are 

 numerous and flattened. It is not easy to find data as to the 

 number of leaves on a plant ; but many years ago there stood 

 in Garden Street, near the Common at Cambridge, Massa- 

 chusetts, a great tree known as the Washington elm, for it 

 was under this tree that Washington in 1775 took command 

 of the American Army. The ravages of tinie and of the 

 "leopard-moth" have reduced this tree to a stump, but at its 

 prime it was calculated to bear some 7,000,000 leaves whose 

 surfaces added together amounted to about five acres. In 

 sunlight this vast area was building up foodstuffs out of 

 carbon dioxide and water. 



Mineral Oil and Natural Gas 



But there is a further consideration which shows the im- 

 mense importance of this green colouring-stuff. It is well 

 known that coal is the mineralized product of innumerable 

 plants living in ancient geological times, and the same seems 

 to be true of the other great stores of energy wliich are at the 

 disposal of mankind. 



