PLANT PRODUCTS 141 



The mucilages and gums are formed within the cell or by 

 modification of the cell wall. Many of them are of considerable 

 commercial value. Among the most important of the vegetable 

 gums of commerce are gum camphor, gum-arabic and 

 gum-tragacanth. 



The oils and resins are formed by the protoplasm and are 

 associated with the mucilages and tannins. There are two classes 

 of oils: (1) The reserve or fixed oils, which are also known as 

 fatty oils and are associated with fruits and seeds. Among the 

 most important are olive oil, corn oil, cotton-seed oil, cocoanut 

 oil, flax or linseed oil and castor oil. (2) The volatile oils, 

 which are found in specialized secretory cells or canals. They 

 are important factors in the odors of plants and many of them 

 are extracted for commercial purposes. Among the most im- 

 portant are : oil of peppermint, oil of sassafras, oil of cinnamon, 

 oil of cloves, oil of cedar, and oil of bergamot from the orange 

 rind. The pine resins, india rubber, gutta-percha and camphor 

 are related to the volatile oils and are well-known com- 

 mercial products. 



Fats and fatty oils are not soluble in water or cell sap>. The 

 vegetable fats are found in the form of minute crystals in the 

 cytoplasm and the fatty oils as very fine emulsions. They are 

 both found in the plants as mixtures of glycerine esters or 

 glycerides of palmitic, stearic and oleic acids and are called 

 palmitin, stearin and olein. The first two are solid at ordinary 

 temperatures and the latter is fluid. They are most abundant in 

 the seeds of plants and serve as important reserve foods in ger- 

 mination. Some of the most important sources of commercial 

 oils are castor beans, flax seed, rape seed, cotton seeds, peanuts, 

 olives and cocoanuts. The edible nuts are very rich in oils. 



