102 



r PRODUCTS 



be freed by the combustion of dry plant materials equals 

 the amount of solar energy necessary for their production, 

 and the animal energy obtained by consuming plant 

 products will also be the same amount less some forms of 

 waste (discussed in Part IV.) . Although the actual mechanism 

 by means of which carbon dioxide is converted into complex 

 organic bodies is only very little known, the substances 

 themselves have been the subject of much elaborate inquiry. 

 The following table gives, in brief form, the chief classes 

 of substances which are produced in plants by these means. 



Water 



Organic 

 matter 



TABLE 19. 



Volatile, such as acetic acid. 

 Non-volatile. Lactic, citric, tar- 

 taric, oxalic acids. 



Pentosans (guins) as araban 



and xylan. 

 Pentoses (sugars) as arabi- 



nose and xylose. 

 Furfuroids, lignin, etc. 

 Hexosans (amylans) as cel- 

 lulose and starch. 

 Hexoses (glucoses) as 



dextrose, levulose. 

 Poly - saccharoses as 



cane sugar, etc. 

 True fats and oils. 



Resins and essential oils. 

 Proteins. 



bodies | Amides and Amines. 



\ Mineral matter 



Phosphates of lime, potash, and 



other bases. 

 Sulphates of lime, potash, and 



other bases. 

 Silicates of lime, potash, and 



other bases. 

 ^ Chlorides of sodium, etc. 



Feeding value. 



(Practically 

 none. 



Doubtful. 



Do. 



None. 



Heat-pro- 

 ducers. 



Heat pro- 

 ducers. 



No value. 

 Do. 



Flesh- 

 formers. 



Small heat- 

 ing values. 



Bone - form- 

 ing. 



None. 



None. 

 Digestive. 



In some cases they are very well-known organic substances, 

 in others they are substances only described in the advanced 

 text-books. 



THE VEGETABLE ACIDS. 



Formic Acid, H.COOH, occurs in small quantities in 

 stings of nettles, in butter exposed to sunlight, in the contents 

 of the stomach, and in many fermented materials. Formic 



