THE STORAGE OP FOOD-RESERVES 151 



contained in them arise as the result of certain chemical 

 changes taking place within the plant, and, most probably, 

 in connection with the respiratory functions. Respiration 

 begins with the inception of oxygen, and usually termi- 

 nates with the elimination of carbonic acid gas. If the 

 process is interfered with in any way, organic by-products 

 are formed, and if these turn out to be useful to the plant, 

 their formation tends to become habitual, and the dis- 

 position to produce them becomes hereditary. 



These substances are found in mustard (ground seeds of 

 Brassica spp.), pepper (ground fruits of Piper nigrum), 

 ginger (rhizomes of Zingiber officinale), cloves (dried 

 flower-buds of Eugenia caryophyllata), nutmeg (seed of 

 Myristica fragrans) capers (flower-buds of Capparis 

 spinosa), chiUies (fruits of Capsicum annuum), water- 

 cress (shoots of Nasturtium officinale), horse-radish (rhi- 

 zome oiCochlearia Armoracia). 



The bases of flavourings are volatile oils. They are 

 generally obtained by distilling the parts of the plants 

 where they are present with water — e.g., fruits of vanilla, 

 aniseed, caraway, and coriander ; cloves; stems and leaves 

 of peppermint ; cinnamon bark ; and the rind of the lemon. 

 In some cases the whole plant is used, either fresh or in 

 a dried state — e.g., thyme, sage, mint. 



(6) Beverages. — Infusions of tea, coffee, and cocoa are 

 universally used as beverages. Alcohol is obtained by 

 fermenting sugar with yeast, either directly from a vege- 

 table sugar or indirectly from starch. The range of 

 intoxicating drinks is almost as great as the range of man 

 himself. Sugary lic[uids, capable of fermentation, are 

 obtained from all kinds of plants — sprouting barley (beer 

 and whisky), grapes (wine, brandy, liqueurs), potatoes, 

 rye, and maize (inferior spirits), sugar-cane (rum), agave 

 (pulque), coconut (arrack, toddy), honey (mead), millet 

 (kafir beer), etc. 



(c) Drugs. — Hundreds of drugs used in medicine are 

 prepared from plants — ^poisons, antiseptics, narcotics, 

 aneesthetics, etc. — all capable of producing more or less 

 profound disturbances in the physiological activities of 

 the human body. Peruvian bark, or Cinchona, is the 

 source of quinine, the opium-poppy the source of morphia. 

 Tobacco may be regarded as a mild drug. The following 

 plants, growing in England, have been used at one time 

 or another in medicine: buckthorn, broom, cherry- 



