THE CONSTITUENT ELEMENTS OF PLANTS. 



Nitrogen is found in plants in the form of vegetable albumen 

 and gluten ; it is also a constituent of some of the acids, and of 

 what are termed the " indifferent substances " of plants, as well 

 as of those peculiar vegetable compounds called " organic 

 bases," which possess all the properties of metallic oxides. The 

 seeds also of all plants contain nitrogenous compounds. 



Estimated by its proportional weight, nitrogen forms only a 



small part of plants ; but it is never entirely absent from any 



•par* of them.; invent when it does not absolutely enter into the 



cbrtypositien'bf a particular part or organ, it is always to be found 



in, the "fluids wljich, p&rv'ade it. 



1 «' / Eh<3 'nitrogenous 1 compounds thus invariably present in the 

 seeds and juices of plants contain a certain quantity of sulphur. 

 When the juices, seeds, or organs of particular kinds of plants 

 are subjected to distillation along with water, peculiar oily sub- 

 stances pass over. These are volatile, and are characterized by 

 their large proportion, both of sulphur and of nitrogen. The 

 volatile oils of the horse-radish and of mustard are examples of 

 this class of bodies. 



From the remarks now made, it is obvious that there are two 

 great classes into which all vegetable products may be arranged. 

 The first of these contains nitrogen ; in the last this element is 

 absent. The compounds destitute of nitrogen may be divided 

 into those in which oxygen forms a constituent (starch, lignine, 

 &c), and those into which it does not enter (oils of turpentine 

 and lemon, &c). The nitrogenous compounds may, in like 

 manner, be divided into three smaller classes. The first of these 

 is distinguished by containing both sulphur and oxygen (in all 

 seeds) ; the second contains sulphur, but is devoid of oxygen (as 

 oil of mustard) ; while the third is composed of bodies from 

 which sulphur is entirely absent (organic bases). 



It follows from the facts thus far detailed, that the development 

 of a plant requires the presence, first, of substances containing 

 carbon, nitrogen, and sulphur, and capable of yielding these 

 elements to the growing organism ; secondly, of water and its 

 elements ; and lastly, of a soil to furnish the inorganic matters 

 which are likewise essential to vegetable life. 



