The Healthy Soil 



9 



either in sacs, known as pycnidia (fig. 2, d) or on 

 free stalks, known as conidiophores, meaning stalk 

 bearing spores (fig. 2, e.). Fungi, like bacteria, de- 

 pend on animals or plants for their food. Like bac- 

 teria, they are differentiated into saprophytes and 

 parasites. 



Relationship of Micro-organisms to the 

 Fertility of a Soil 



Bacteriologists are continually engaged in discov- 

 ering the possible function of numerous groups of the 

 soil organisms. A recent exhaustive study * of Acti- 

 nomyces, or thread bacteria, in the soil, for instance, 

 seems to show that they serve to decompose grass 

 roots, being more numerous in sod than in cultivated 

 land. Other groups of bacteria undoubtedly per- 

 form other important functions. 



The mere presence of friendly micro-organisms in 

 the soil, however, would be insufficient to assure the 

 welfare of our cultivated lands. These minute or- 

 ganisms must find the conditions necessary to induce 

 a maximum activity in th^ performance of their 

 work, which is to act as chief cook in the dietary of 

 the plant. Most of the plant's food, as it is found 

 in the soil, is in a crude and unavailable form. The 

 bits of mineral matter, the manure, or fertilizer 

 added to the greenhouse soil, all contain plant 

 foods, but in a form which plants cannot readily 



♦Conn, Joel H., New York (Geneva), Agr. Expt. Sta. BuL 52: 

 3-11, 1916. 



