RELATION OP PLANT PHYSIOLOGY TO OTHER SCIENCES. 437 



called forth many relationships between it and the social sciences. 

 What it has done in explaining the exhaustion, what it has contributed 

 to the understanding- of the significance of the forest covering for cli- 

 mate and for the cultivation of field and garden vegetation has benefited 

 the social sciences. But there are besides many other relations exist- 

 ing between these two seemingly widely separated sciences. In order 

 further to illustrate this I will give another example, intentionally an 

 extreme but instructive case. For almost a century men busied them- 

 selves with the question as to how long the earth's stores of coal would 

 last in view of the enormous increase in the use of fuel. The estimates 

 awakened grave apprehensions, though one might reassure himself by 

 this fact that the premises upon which such dire conclusions were based 

 lacked very much of being accurate. Next, comes from across the ocean 

 a more disturbing and vexatious intelligence. Through the American 

 and English papers goes the news — reflected also in the German press — 

 that the danger of extinction of mankind would come sooner than had 

 hitherto been feared. Under an appeal to the authority of a great 

 physicist it was claimed that, with the increasing consumption of min- 

 eral fuel by the various industries, all supplies of mineral coal would 

 be exhausted within five hundred years. But the last remnants of 

 coal — so it was further claimed — it would no longer be possible to bring 

 out of the earth, because in the meantime the oxygen of the atmos- 

 phere, as a result of the enormous increase in combustion, would have 

 decreased to such a limit that the air would no longer be adapted for 

 human respiration. 



The computations in question seemed to be entirely accurate, but 

 again the assumptions were uncertain, upon which these terrible results 

 were predicted, as indeed the whole question whose solution proceeded 

 upon complications of a similar kind, were dealt with only from the 

 chemical standpoint, quite disregarding the character of living organ- 

 isms. 



Every condition of the earth which corresponds with the Kant- 

 Laplace theory forms the starting point for computations like those 

 above cited. All of the earth's carbon is burned up ; all of the oxygen 

 allotted to our planet is exhausted. After cooling of the earth, the 

 green vegetation appears and generates free oxygen under the influ- 

 ence of sunlight. This hypothesis derives the whole of the atmos- 

 pheric oxygen from the green vegetation. Since, at that time, there 

 was no other natural source of oxygen upon the earth besides the green 

 plants, it followed that with increasing combustion the oxygen supply 

 would diminish. In order to check this decrease it was advised that 

 extensive areas of fruit trees should be planted. So it was hoped that 

 in this way a sufficient quantity of oxygen and human sustenauce 

 would be assured to help out the inhabitants of the earth. What small 

 agencies opposed to the harmonious working of the powers of nature! 



Upon how weak a foundation the foregoing hypothesis stands may 



