LESSON 6.] OILS, WAX, CHLOEOPHYLLE, ETC. 



19 



dies, and for greasing the wheels of locomotives and cars on railroads, 

 especially in Europe. 



110. The valuable properties of castor oil, obtained from the 

 seeds of Ricinus communis, as a medicine, are well known. 



111. THE ESSENTIAL OILS occur in the stem, leaves, flowers and 

 fruit of many odoriferous plants, and are procured by distillation 

 with water ; they are called essences, and contain the concentrated 

 odor of the plant. The most conspicuous of these are the oils of 

 cinnamon, otto or attar of roses, of peppermint, caraway, cloves, &c. 



112. Amongst the seeds of plants used for human food, or nuts 

 as they are called, the almond claims attention. If a thin section of 

 it be made, and submitted to the microscope, a number of cells (Fig. 

 24) filled with a concrete oil will be seen. The masses into which it 

 resolves itself are of a variable size ; there is some difficulty in mak- 

 ing these preparations and preserving them, as the oil frequently 

 quits the cells, and follows the knife ; moreover, the great density of 

 the preserving fluid, causes the oil to flow out of the cells, and fuse 



FIG. 25. 



FIG. 24. 



Section of Almond, showing 

 oil in situ. 



Section of Cocoa-nut. 



into large patches on the outside of the tissue ; cells thus emptied 

 are shown in the figure. 



113. The cells of the Cocoa-nut also contain ^, concrete oil (Fig. 

 25), which", obtained by pressure, possesses much value as an oil for 

 lamps, and a material in the composition of candles. 



114. WAX is another peculiar fatty substance, sometimes found 

 in the stem and fruit of plants. It is procured from several species 

 of Palms, the candle-berry Myrtle (Myrica cerifera, and Myrica 

 cordifolid] ; it is also found on the external surface of fruits, forming 

 the bloom of grapes, plums, &c., and on the leaves of many plants. 



115. It is a popular opinion that the honey-bee forms, secretes, or 



