THE GROWTH AND NUTRITIOX OF PLANTS. 115 



forms a very large per cent of all growing plants, it is seen that 

 the larger part of the plant comes from the air. But is the water 

 all that comes from the air? 



Starch, sugar, fibre, gum, and oil are made up of three elements, 

 namely: Carbon, Hydrogen, and Oxygen. The carbon in all of 

 these comes from the carbonic acid gas which exists in the air. 

 The hydrogen and oxygen come from water, which is made up of 

 these two elements. Again about eighty-four per cent of the 

 albuminoids are composed of the same three elements. That 

 such is the source of the plant substance, has been thoroughly 

 proved by numerous experiments. Thus it appears that 39,479 

 pounds out of 40,000 pounds in the ensilage crop came from the 

 air, and that 11,765 pounds out of 12,000 of the grass crop as 

 cut, came from the same source (12,000 lbs. of grass, in drying 

 in the field, must lose 8,000 lbs. of water, leaving 4,000 lbs. of 

 dry hay). 



We are left in doubt as to the origin of the nitrogen of the crop. 

 Experimenters differ in their conclusions as to this element, but 

 we will place it in the list of substances that come from the soil. 

 Doing this, we find that 521 lbs. of the 40 tons of ensilage, is all 

 that comes from the soil, while in the grass crop only 235 lbs. 

 can, by any means, be regarded as originating in the soil. Hence 

 we may well abandon the too common idea that the bulk of the 

 growing plant is made up of elements which come from and 

 therefore exhaust the soil. 



(3.) Are all of the Parts that Come from the Soil of Equal 

 Importance? The answer must be that they are not. In the 

 foregoing tabular statement, are given the substances which make 

 up the ash of the crops we are considering ; now by experiments 

 of various kinds it has been found that magnesia is necessary for 

 the perfect growth of the plant, but it is also true that in most 

 soils the supply is abundant, so that for all practical purposes 

 magnesia is not to be regarded as an essential element. 



Silica has been shown to be an unimportant substance, since 

 plants may be grown and matured in solutions where there is no 

 silica present. Lime is absolutely essential to the plants. 

 Plants having every other element within their reach fail to grow, 

 but the addition of lime immediately causes the building up 

 processes of the plant to become active. 



But lime is a very common and abundant constituent of most 



