160 AGRICULTURE. 



ALBUMINOIDS. Compounds like albumen or white of egg, 

 the casein of milk, the gluten of wheat, and the fibrin of meat, 

 are known as albuminoids or protein. They are all compounds 

 containing nitrogen, and are the flesh-forming substances of 

 food. They are very low in roots, a little larger in grass, still 

 larger in hay ; so that we see that they increase as plants ma- 

 ture. They are very low in straw, but quite large in grain. 

 Why is this ? As the wheat, oats, and other plants are grow- 

 ing they take up food from the air and soil and, until blossom- 

 ing time, all their food is contained in the leaves, stalks, and 

 roots. After blossoming the seeds form, and material that has 

 been stored in the stalk and leaves is used to build up the 

 seed. In most plants very little valuable food is taken into 

 the plant through the roots after the time of blossoming. The 

 leaves continue taking in carbon and the roots water, and 

 therefore starch and sugar continue to increase, but the other 

 substances are about all in the plant by the time of full bloom. 

 Out of the leaf and stalk the most valuable materials are then 

 carried into the seed ; thus we find the nitrogenous com- 

 pound, the fats or oils, and the most valuable ash compounds, 

 especially the phosphates, stored up in the seed or grain, and 

 not in the straw. 



FAT. For the reasons just given we must look for fat or oil 

 principally in the grains. Some seeds, such as flaxseed, con- 

 tain a very large amount of oil. 



STARCH AND SUGAR. These materials are very much alike 

 in composition ; they are composed of three elements 

 carbon, hydrogen, and oxygen. Hydrogen and oxygen, we 

 have learned before, are the two elements composing water. 

 These two are found in starch and sugar in the same proportion 

 as in water, but not as water, and therefore such compounds 

 are sometimes called " carbo-hydrates." They are found in 

 large quantities in all plants and parts of plants, forming as 



