CHAPTER XV 

 ALLIED AND MISCELLANEOUS PRODUCTS 



Variety's the very spice of life, 

 That gives it all its flavor. 

 — Wm. Cowper. 



In the plant factory, aside from the foods mentioned in the three 

 preceding chapters, are made other products, which are more or 

 less closely related and which have certain physiological roles in 

 the plant. These will be described in the following order: 



1. Glucosides. 



2. Organic acids. 



3. Nitrogen bases. 



4. Aromatic aldehydes, alcohols, phenols, and acids. 



5. Essential oils and resins. 



6. Tannins. 



7. Pigments. 



Glucosides. — The glucosides are compounds of sugars with 

 various other substances usually belonging to the class of aro- 

 matic compounds. Strictly speaking they should always contain 

 glucose, but the term is rather a loose one which includes many 

 different substances, and in some cases the sugar present is galac- 

 tose, mannose, or levulose. Even combinations with pentoses 

 are not unknown. To include the different substances found here 

 under one class is to a certain extent artificial and, if the compound 

 associated with the sugar is more important than the sugar, the 

 substance may more fittingly be placed in another group, as in 

 the case of the glucoside pigments. 



The glucosides are generally soluble in water, forming a levo- 

 rotary solution. When purified^ they form colorless crystalline 

 solids with a bitter taste. They are hydrolyzed by specific enzymes. 

 Several hundred glucosides have been isolated from plant tissues, 

 and among the products resulting from their hydrolysis, aside 

 from sugars, are alcohols, aldehydes, hydrocyanic acid, phenols, 

 mustard oil, saponins, flavones, anthocyans, etc. The glucosides 

 are classified upon the basis of these products. 



Among the alcohol glucosides is salicin from willow bark and 

 leaves. It is used in medicine for the treatment of fevers and 



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