200 



made more practical and more interesting and also more popular. When 

 tiiey see that no line of work really needs more knowledge and skill it 

 will be a strong inducement to our young people to think of spending 

 tkeir time in developing our country along agricultural lines. 



The great need tliat may be seen in many parts of southern Indiana 

 is the formation of a proper vegetable mould. This means that there 

 must be a greater amount of proteid substauce in it. This fiu'ther means 

 that nitrogen is the element most needed and the one most difficult to 

 secure. Since about four-fifths of the air is composed of nitrogen it would 

 seem that we should not lack for this substance. This source of wealth 

 had remained hidden for centuries. Not until recently did we learn of 

 the part that the leguminous plants play in tliis problem. Now we know 

 that this class of plants is the one that can make use of the nitrogen of 

 the air for the manufacture of proteid sul)stances of plants. 



Fewer than ten years have elapsed since the noted German scientists 

 Nol)be and Hiltner suggested that pure cultures of soil bacteria might be 

 used to inoculate new soils. German expei'iments continued to be made, 

 but they were quite unsatisfactory. 



In 1901 the Department of Agricultui'ie of the United States began 

 investigations in its laboratory of plant physiology to find an 'artificial 

 medium in which Ijacteria Avould grow and still preserve its power or even 

 to intensify its qualities. Furthermore the bacteria must have the power 

 to penetrate the roots of the plants, because it is impossible to fix nitrogen 

 unless they are stimulated by the activities of the plant itself. The result 

 of this investigation was a liquid culture. This culture is put up in three 

 packages, Nos. 1, 2, and 3. No. 1 consists chiefly of sugar with a little 

 potassium phosphate and magnesium sulphate. No. 2 consists of cotton 

 laden with bacteria. No. 3 contains ammonium phosphate. No. 1 is 

 dis.solved in one gallon of water and the bacteria placed in it. This must 

 be kept in a warm place, the temperature of which is between 70 and 80 

 degrees. At the end of twenty-four hours No. 3 is added and kept twenty- 

 four hours more imder similar conditions. The water by this time will be 

 quite milky. Examination with the microscope reveals myriads of bac- 

 teria in active state. 



The seed is now thoroughly moistened with the water and spread 

 out to dry as quickly as possible. This liquid culture will retain its 

 qualities for about forty-eight hours. The inoculated .seed may be kept 



