AGRICULTURE. 



CHAPTER V. 



THE PLANT AND THE AIR. 



THE COMBUSTIBLE PART OF A PLANT. When we dry 

 any plant thoroughly, we drive off the water that it contains ; 

 when we burn up this dried portion, we have left the ash. 

 But what about the portion that has been burned up ? What 

 was it and where did it come from ? All plants contain fibre 

 woody fibre as we may now call it ; this has been burned 

 up. Some plants, such as sugar beets, sugar cane, and corn, 

 contain some sugar. Other plants, such as potatoes, contain a 

 large quantity of starch. In burning, all the fibre, starch, and 

 sugar are burned up. Then such seeds as flaxseed and cotton 

 seed contain oil. There are other substances, also, that we 

 should know. For instance, if we chew a few grains of wheat, 

 we find after a short time a small quantity of a gummy sub- 

 stance remaining in the mouth it is called gluten. Then you 

 all know that from many different fruits a beautiful clear sub- 

 stance is got by boiling, known as jelly. Perhaps we have 

 mentioned enough fibre, starch, sugar, oil, gluten, jelly 

 substances all these and many others similar to them are 

 found in plants. They do not pass off when the water evapor- 

 ates, nor are they left behind in the ash. They are all con- 

 sumed or burnt up when the plant is burned. 



What do they consist of? In burning any plant slowly, the 

 first thing that you notice is that the plant becomes black 

 charred ; and by very slowly burning it we can turn it into a 

 black mass that we call charcoal, somewhat like coal in 

 appearance. This black color is given to it because of the 

 carbon which it contains. If we could put some of this 



