74 



GROWTH AND SECRETIONS. 



more principles, which can be separated, and 

 are not homogeneous, like the nutritive juice, 

 which, although it may of course, by chemical 

 analysis, be resolved into its elementary con- 

 stituents, presents no such peculiar principle 

 as do the special secretions. 



2. These latter contain (in addition to their 

 carbon) oxygen and hydrogen, not in the pro- 

 portion in which they combine to form water, 

 but with a preponderance of one or the other 

 of those gases, and some of them, and those 

 the most important to man, also contain azote, 

 i. e. nitrogen. 



3. All these secretions, if they are absorbed 

 by the roots of living plants, even by those 

 which produced them, act on them as poisons. 

 A sufficient proof of their not being intended 

 to percolate the plant in the manner of the 

 nutritive juices. 



They consist principally of four divisions : 

 1, Milky, and 2, Resinous Juices, 3, Volatile, 

 and 4, Fixed Oils,* and the local secretions, 

 properly so called. The milky and resinous 

 fluids, which form the first two classes, are some- 



* With the fixed oils should perhaps be classed the 

 vegetable tallows and butters. 



