THE VOLATILE PAET OP PLANTS. 



83 



effect on vegetable colors that belong to ammonia. Car- 

 bonate of sodium has the taste and other propei'ties of caus- 

 tic soda in a' greatly mitigated form. On the other hand, 

 sulphates of aluminum, iron, and copper, have slightly 

 acid characters. , 



5. Fats ajs^d Oils (Wax). — We have only space here 

 to notice this important class of bodies in a very general 

 manner. In all plants and nearly all parts of plants we 

 find some representatives of this group ; but it is chiefly 

 in certain seeds that they occur most abundantly. Thus 

 the seeds of hemp, flax, colza, cotton, bayberry, peanut, 

 butternut, beech, hickory, almond, sunflower, etc., con- 

 , tain 10 to 70 per cent of oil, which may be in great part 

 removed by pressure. In some plants, as the common 

 bayberry and the tallow-tree of Nicaragua, the fat is 

 solid at ordinary temperatures, and must be extracted by 

 aid of heat ; while, in most cases, the fatty matter is 

 liquid. The cereal grains, especially oats and maize, con- 

 tain oil in appreciable quantity. The mode of occur- 

 rence of oil in plants is shown in Fig. 17, which repre- 

 sents a highly magnified section of the flax-seed. The 

 oil exists as minute, transparent globules in the cells, /. 

 From these seeds the oil may be completely extracted by 

 ether, benzine, or sulphide of car- 

 bon, which dissolve all fats with 

 readiness, but scarcely affect the 

 other vegetable principles. 



Many,plants yield small quanti- 

 ties of wax, which often gives a 

 glossy coat to their leaves, or 

 forms a bloom upon their fruit. 

 °^^^P^^^^^T^ The lower leaves of the oat-plant 

 '^^r~^^^^^^(WO ^* *'^^ ^™^ ^^ blossom contain, in 

 the dry state, 10 per cent of fat 

 and wax (Arendt). Scarcely two' 

 of these oils, fats, or kinds of wax, are exactly alike in 



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