126 PLANT LIFE. 



These fungi belong apparently to very different species 

 (A inanita inuscaria^ Lactarins piperatus, etc.), but there is 

 a want of definite details as to their origin ; it is, how- 

 ever, certain, that the development of the tree is very 

 seriously hindered if they are not present. Not merely 

 trees but many smaller bushes, like the Blaeberry, or 

 even very tiny herbs like Monotropa, maintain a fungus 

 assistant. These fungus threads are much finer and 

 more rapidly developed than root hairs ; they will thus 

 ensure a more thorough search of every particle of soil 

 for the valuable nitrates, sulphates, and phosphates. As 

 the group of fungi are specialised to feed on decaying 

 matter, they will probably be able to obtain food from 

 or break up substances which cannot be absorbed by 

 ordinary root hairs. (See Chap. XI.) 



In addition to the roots, Mycorhiza and colonising 

 stems already mentioned, the soil contains a very 

 varied flora and fauna. Of this flora the bacterial 

 population is probably of prime importance to agri 

 culture (see Chap. X.), especially, in the way of 

 breaking up the dead bodies of plants and animals in 

 such a manner, that the material can enter the roots of 

 other plants. 



Amongst the animal population, the worm is of the 

 greatest importance, and is probably essential in every 

 sort of agriculture. It has been estimated that there 

 are in i-|- acres of arable land some 200,000 individual 

 worms. Their burrows go down to six feet or more, 

 and thus aerate the soil ; they drag down leaves to a 

 depth of 3 or 4 inches, and assist in digging and work- 

 ing the soil generally. But their main duty is to eat 

 earth for the sake of the decaying vegetable matter which 

 it contains. After being rubbed into fine particles in 

 their muscular gizzards, and after the humus material 



