204 THE LIVING ORGANISMS OF THE SOIL [chap. 



Fungi of Importance in the Soil. 



Allusion has already been made to the fact that a 

 large number of fungi inhabit the soil — Penicillium y 

 Mucor, Trichoderma, Spicaria, etc., Cladosporium, Clado- 

 thrix, and various wild yeasts, Monilia, etc. — all of 

 which aid in breaking down the organic matter. Many 

 of these fungi possess the power of attacking ammonium 

 salts applied as manure, withdrawing the ammonia and 

 setting free the acid. To this action is due the acidity 

 produced by the long-continued use of ammonium salts 

 as manure, as seen on the experimental plots at Rotham- 

 sted and Woburn. At Woburn the soil is light and 

 sandy, containing but little lime, and the application of 

 ammonium salts containing 50 lbs. ammonia per acre 

 every season for twenty-four years, has rendered the 

 land practically incapable of carrying the crops. A 

 moderate dressing of lime, however, restores the fertility. 

 The following crops were obtained in 1900 on the barley 

 plots : — 



The soil had become acid to litmus paper where the 

 lime had not been used : it is interesting to note that 

 though barley would not grow, oats flourished freely on 

 this sour soil. There are, however, two special organisms 

 which merit further consideration — the fungus which 

 clothes the finer rootlets of many classes of plants, 

 forming mycorhiza and the slime fungus, or Plasmodio- 

 phora which causes the disease known as "finger-and- 

 toe " or " club " in turnips and other cruciferous plants. 



