HOW THE PLANT GROWS 9 



ash in solution is left behind. The ash content of the bark of trees and 

 stems of plants is also usually high. 



13. The end of plant effort. If we study the life history of a plant, we 

 observe that its first effort is toward self -establishment and enlargement. 

 At this time all the elaborated material, as fast as formed, is transferred 

 to the growing parts that they may be built up and established. As the 

 plant approaches maturity, its energies are changed from growth to re- 

 production, or the perpetuation of its kind. The nutrients in the juices, 

 which were formerly directed to the growing portions, are now turned 

 toward the reproductive parts. First come the blossoms, then the young 

 enlarging fruits. Into these the sugars, amids, and mineral substances, 

 all elaborated and worked over by the plant in its leaves, are poured in a 

 steady current. The wheat plant resulting from a single kernel bears a 

 hundred fruits in the shape of seed grains, while the Indian corn plant 

 may produce a thousand-fold. In each of these grains is a miniature 

 plant, the germ, composed largely of protein, about which is stored a 

 generous supply of rich nutriment proteins, starch, sugar, oil, and 

 mineral matter all in compact, concentrated form, awaiting the time 

 when the germ shall begin life on its own account. 



14. Plants support animal life. It is Nature's plan that plants shall 

 use energy supplied by the sun in building inorganic matter taken 

 from earth and air into organic compounds. In this process the sun 

 energy employed becomes latent, or hidden. Animals can not directly 

 secure from the sun the energy necessary for their life but must 

 live on the organic compounds built by plants. After more or less 

 change during digestion, these compounds are built into their body 

 tissues or are broken down within their bodies to produce heat and 

 energy. In the coal burning in the grate, there reappears the energy 

 of the sun which was stored in the plants of ages ago. In a similar 

 manner the energy received from the sun by plants during their 

 growth is transformed into animal heat and energy. Plants are thus 

 sun-piower machines for furnishing food to support animal life. 



II. How THE CHEMIST GROUPS PLANT SUBSTANCES 



As we have seen, many different compounds are formed in plants, 

 some of these being so complex that their exact structure has not yet 

 been determined. In studying feeding stuffs it is desirable to group 

 all plant compounds into a few classes, the amounts of which can be 

 readily found by chemists. Accordingly, in analyzing plant materials 

 and feeding stuffs, the following classes or groups of substances are 

 commonly determined : water, ash or mineral matter, crude protein, 

 fiber, nitrogen-free extract, and fat. The average percentages of these 

 in typical feeds are shown in the following table, which is taken 

 from Appendix Table I. The last column gives the number of 

 analyses from which the average composition has been computed by 

 the authors. 



