194 Bureau ok Farmers' Institutes. 



growth. The following list contains t lie names of elements that 

 occur in plants: Carl. on, oxygen, nitrogen, hydrogen, potas- 

 sium, phosphorus, calcium, magnesium, sulphur, iron, chlorin 

 (sodium, silicon, manganese). 



These few elements we may regard as a kind of chemical alpha- 

 bet of the vegetable world. We do not find these elements simply 

 tumbled together in miscellaneous heaps in the formation of 

 plants. Somewhat as the letters of our alphabet unite to form 

 words, so the chemical elements are united to form various chemi- 

 cal compounds, and these compounds are mixed together in a 

 variety of ways to form plants. 



Classes of Chemical Compounds in Plants. — It will be of in- 

 terest in passing to notice briefly some of the more common kinds 

 of chemical compounds found in plants: 



1. There is a most important and extensive group of compounds, 

 each containing carbon, hydrogen and oxygen. The class, as a 

 whole, is known by the name of carbohydrates. The most common 

 members of this class are sugar, starch, woody fiber, vegetable 

 gums, etc. 



2. We have another class distinguished for the valuable food 

 constituents contained in it, known in general as proteids. As a 

 representative of this class, we may mention the gluten or sticky 

 portion of wheat flour. This contains beside the three elements 

 of carbohydrates, three other elements — nitrogen, phosphorus 

 and sulphur. 



3. We have the vegetable oils, from which come our linseed, 

 castor, olive, cotton seed, and other vegetable oils of commercial 

 importance. 



4. We may mention as another class the vegetable acids — for 

 example, the tartaric acid of grapes, present as a compound of 

 tartaric acid and potassium, containing the elements carbon, hy- 

 drogen, oxygen and potassium; citric acid, found in lemons, cur- 

 rants, cherries, strawberries and similar fruits; malic acid, in 

 apples, etc. 



5. We have that extremely important class of compounds which 

 give characteristic flavors to many plant products, particularly the 

 flowers and fruits. 



6. There may be mentioned in passing the very widely dis- 

 tributed substances of vegetable origin, used for medicinal pur- 

 poses, such as quinine, morphine, strychnine, etc. 



The exact number of different compounds in the vegetable king- 

 dom formed from our dozen elements is not known but must be 



