CHAPTER I. — THE CELL. 



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of anise (C 10 H 12 O), bergamot, rose, sandalwood, etc. ; nitro- 

 genatcd essences, as the oils of cherry-laurel leaves and bitter 

 almonds (C 7 H 6 0, HCN) ; and sulphureted essences, as the oils 

 of assafcetida, mustard (C 3 H 5 , CNS), and horse-radish. Many 

 of the natural essences are mixtures of two or more different 

 compounds. 



Closely related to these are the camphors, like common cam- 

 phor (C 10 H 16 O), Borneo camphor (C 10 H 18 O), etc. They are often 

 found associated with the volatile oils, and appear to be derived 

 from them by oxidation. 



Resins, Oleo-resins, Gum-resins, and Balsams. Resins 

 are very common constituents of plants. They appear to be in 

 the nature of excretory products, formed by the decomposition 

 of tannin, or other glucosidal bodies. They are either pro- 

 duced in special cells or groups of cells called glands, occurring 

 on the surface of plants, or forming the terminal cells of glandu- 

 lar hairs, or else in internal cells which pour their secretions 

 into intercellular spaces called secretion reservoirs. They are, 

 for the most part, amorphous, more or less transparent, readily 

 fusible substances, which cannot be volatilized without change, 

 and which are soluble in alcohol and in the volatile oils, but not 

 in water. Guaiac, mastich and common rosin may be taken as 

 examples. When mixed with volatile oils, as in Venice and 

 common turpentines, they are called oleo-resins ; if they contain 

 benzoic or cinnamic acids, either with or without volatile oils, 

 they are called balsams ; and if mixed with gums, they are 

 termed gum-resins. The last are often constituents of the milk- 

 juice of plants. Benzoin, Styrax and Peru Balsam are examples 

 of the balsams, and Gamboge, Myrrh, Galbanum and Ammoniac 

 of gum-resins. Caoutchouc and Gutta-percha are peculiar resin- 

 ous constituents of the milk-juice of some plants. 



Glucosides. The glucosides are compounds found in solu- 

 tion in the cell-sap, or deposited in the cell-walls of plants. 

 Their peculiarity consists in the fact that under the influence of 

 unorganized ferments like ptyalin, emulsin, myrosin, etc., or by 

 other means, they are decomposable into glucose or some simi- 

 lar sugar, and another substance capable of still further decom- 

 position. Their molecules are complex, and most of them are 

 composed of carbon, oxygen and hydrogen, but some few of 



