PLANT PRODUCTS 



137 



(mannans and galactans) which are very similar to true cellu- 

 lose. They are deposited on the inner surfaces of the walls of 

 cells and are very readily transformed into sugars. They give 

 the hard, horn-like character to coffee and date seeds and are im- 

 portant foods in the germination of these seeds. 



The alkaloids are supposed to be formed in the protoplasm, 

 but are later found in the cell sap in combination with the vari- 

 ous plant acids. They contain nitrogen, carbon, hydrogen and 

 sometimes oxygen; they will combine with acids and form salts. 

 They are usually 

 associated with 

 starch, fixed oils, 

 aleurone grains 

 and other reserve 

 food products. 

 They may be 

 abundant in im- 

 mature fruits and 

 seeds, but they 

 disappear with maturity. Many of the alkaloids are very poi- 

 sonous. Among the most important are the following: 



(a.) Theine, from tea; 1 to 3 per cent, in dry leaves. 



(6) Caffeine, from coffee ; .5 to 2 per cent, in the bean. 



(c) Theabromine, from cacao, or chocolate plant; 1.5 per 

 cent, in the seeds. 



All of the above are in general use, but are poisonous and 

 injurious to health when used in large quantities. 



(<#) Morphine and a number of other alkaloids from the 

 opium poppy are used in medicine. The smoking of opium has 

 most deleterious effects on both body and mind. Opium and its 



Fio. 94. Cell from grain of corn containing starch. 



