WHENCE DO PLANTS DERIVE THEIR CARBON. 79 



mers to consider this question with much interest, if at all; 

 giving more attention to the other elements of plant growth 

 and leaving^the carbon to take care of itself. But it is a 

 question which should be carefully considered, because of its 

 importance and because other questions which draw atten- 

 tion from it, may become more prominent than they deserve. 

 We know that there was a time when no vegetable mat- 

 ter existed in the soil and when vegetation first covered the 

 earth's surface. Then the first plants must have grown and 

 matured without the aid of any vegetable or animal matter 

 in the soil and could have derived their carbon from no 

 other source than the atmosphere, directly; or indirectly, 

 by its presence in the water in the soil. It is also known 

 that soils which have been perfectly arid and have produced 

 no vegetation, or very little previously, yield abundant 

 crops when brought under culture by irrigation, and that 

 plants are often grown in water and in some cases grow lux- 

 uriantly without having any connection with the soil. 

 Further it is a common practice for farmers, when their 

 lands are unable to produce maximum crops, to seed them 

 to grass or clover and to leave them for years to recuperate 

 and become enriched by the gradual accumulation of veg- 

 etable matter in the soil; and when these lands are again 

 plowed a rich black soil filled with carbon is found, where 

 but little organic matter existed previously. This also ap- 

 plies to lands under forest growth, and to the rich prairies 

 of the west, where the dark vegetable mold- lies many feet 

 in thickness and contains an inexhaustible supply of carbon; 

 as well as to the peat swamps in which enormous quantities 

 of carbon have been accumulated. We may also take into 

 consideration the vast beds of coal which have been made 

 up of accumulations of vegetable matter, the luxuriance of 

 which, proved by its remains, still to be recognized in the 

 coal, almost surpass imagination; and may then ask, 

 whence did all this vegetable growth procure its carbon, 

 which has gradually accumulated in the soil to this vast 

 extent; and which we can perceive still accumulates under 

 our own personal observation ? 



