38 Report of the Acting Director and Chemist of the 



compounds in the vegetable kingdom as there are different species of 

 plants. This, of course, can not be known absolutely until all plants 

 in existence have been carefully analyzed; but, whether the number 

 of different chemical compounds in the vegetable kingdom be a few 

 thousand or a few hundred thousand, we know that they are almost 

 entirely made up of fourteen elements, and these, therefore, form 

 the chemical alphabet of the vegetable kingdom, all the different 

 vegetable compounds, like words from letters, being formed by the 

 union of two or more of these elements. 



The fourteen elements which are regarded as being necessary to 

 tlie perfect growth and development of every plant are the follow- 

 ing : Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, Sulphur, 

 Chlorine, Silicon, Calcium, Iron, Magnesium, Manganese, Potassium, 

 and Sodium. The element fluorine is of frequent occurrence in very 

 small quantities ; and the following elements are of rare or doubtful 

 occurrence: Aluminum, barium, bromine, cobalt, copper, iodine, 

 lead, lithium, nickel, rubidium, tin, titanium, and zinc ; but their 

 occurrence is a matter of curiosity rather than of practical import- 

 ance, for, unlike the fourteen named above, they seem in no way to 

 be necessary to plant life. 



To chemical analysis we owe all that we know about what plants 

 contain or are made of. Eighty yeai's ago not a single vegetable 

 substance had been accurately anal^^zed ; and, although, in the thirty 

 years following, much was learned about the different elements con- 

 tained in plants, it was not until after the investigations of Liebig 

 that our knowledge of the chemistry of plants progressed with any 

 satisfactory degree of rapidity 



Classification into Air-Derived and Soil-Derived Elements. — 

 The elements that are necessary to the growth of plants may be 

 divided into two quite distinct classes, wdiich have important and 

 mai'ked differences. These two classes are : (a) Air-derived or 

 organic elements, (b) Soil-derived or inorganic elements. 



