FIRST PRINCIPLES OF AGRICULTURE. 



CHAPTER I. 



/S^37 

 The Constituents of Plants; Plant Growth. 



Parts of Plants. Most agricultural plants possess 



three distinct parts, the root, the stem, and the leaf. 



The main uses of the root are to secure food from the soil, 



and to serve as a support to the plant during its period 



of life. The stem acts as a support for the leaves, as 



a medium for the circulation of food through the plant, 



from the leaf to the root and from the root to the leaf, 



and as a storehouse of nutriment for future growth. The 



T^ leaves secure food from the atmosphere, and permit the 



( escape into the air of the water taken up by the roots. 



^ These different parts all co-operate, or work together, 



1 to secure and distribute the constituents necessary to the 



^ 



complete growth and development of the whole plant. 

 What is plant food, or of what constituents is a plant 

 composed, is a question of the first importance in a study 

 of the growth of plants. 



The Water contained in Plants. A plant in the 

 first place is composed of two distinct classes of sub- 

 stances, water and dry matter. Water is contained in 

 all growing plants ; forest and fruit trees seldom contain 



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