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- 



