Metabolism; Digestion and Translocation 259 



especially in the seeds of palms. This reserve food be- 

 comes available during germination. 



146. Fats and oils. - - Fats and oils are far more com- 

 mon and important constituents of plants than is popu- 

 larly supposed. In Liliacese and a few other mono- 

 cotyledonous orders oils replace starch as the first visible 

 photosynthetic product. Oily bodies occur in active cells 

 often as small droplets in the cytoplasm. In a variety of 

 seeds the amount of fatty substances is considerable, a 

 part occurring as globules or as crystals. 



Among the more important fats and oils may be men- 

 tioned those from corn, coconut, various palms, olives, 

 mustard, poppies, flax, castor-bean, Bergamot-orange, 

 carnation, Brazil-nut, cotton, etc. Thousands of tons of 

 palm and coconut oil are annually imported into Europe 

 and constitute an important item of trade. The value 

 of the cotton-seed oil produced during 1909 and 1910 is 

 estimated to have been upwards of $300,000,000. 



Oils and fats may be identified by comparatively simple 

 tests and they are obtained for commercial purposes by 

 crushing and pressing, or by extraction. 



147. Proteins. - The vegetable proteins are numerous, 

 and they vary greatly in physical and chemical character- 

 istics. They may occur in solution in the cell vacuoles, 

 partially dissolved in intimate association with the pro- 

 toplasm, and as solid forms - - crystals or granules. The 

 latter occur especially in storage organs or tissues with 

 reduced water-content, usually associated with carbohy- 

 drate storage products, oil, and other substances, as in 

 many legumes. 



The vegetable proteins have been studied more particu- 



