FIELD AND FOREST. 107 



especially can penetrate deep into the sub soil, only where there are 

 earthworms. 



A microscopical comparison of the earth deposited by the worm 

 shows that it is like two-year leaf mould prepared by gardeners for fill- 

 ing of flower pots. Most of the plant cells are destroyed ; still there 

 are present some cells and shreds of tissue, browned and friable, mixed 

 with many sand grains and brown organic fragments. The chemical 

 composition of the worm earth shows much similarity to that of fertile 

 humus ground. Its fertility, therefore, cannot be "doubted, though 

 direct experiments with it are wanting. 



With regard to the numerical value of this action of the earthworm, 

 the following observations by M. Hensen affjrd some information. 



Two worms were put into a glass pot i}4, foot in diameter, which 

 was filled wiih sand to the height of i^ foot, and the surface covered 

 with a layer of fallen leaves. The worms were quickly at work, and 

 after i^ month many leaves were down 3 inches deep into the tubes; 

 the surface was completely covered with humus 1 cm. in height, and 

 in the sand were numerous worm tubes partly fresh, partly with a 

 humus wall 3 mm. thick, partly quite filled with humus. 



Counting when an opportunity offered, the open worm tubes in his 

 garden, M. Hensen found at least nine in the square foot. In 0.15 

 square metres two of three worms were found in the deeper parts each 

 weighing three grammes: thus in the hectare there would be 133,000 

 worms with 400 kilos, weight. The weight of the secretions of a 

 worm in twenty-four hours was 0.5 grammes. While these numbers 

 are valid only for the locality referred to, they yet give an idea of the 

 action of this worm in all places where it occurs. 



The assertion that the earthworms gnaw roots is not proved by any 

 fact ; roots gnawed by worms were never met with, and the contents 

 of the intestine of the worms never included fresh pieces of plants. 

 The experience of gardeners that the earthworm injures pot plants may 

 be based on the uncovering or mechanical tearing of the roots. 



"Let us take a retrospective glance," concludes the author, "over 

 the action of the worm in relation to the fertility of the ground. It 

 is clear that no new manure material can be produced by it, but it 

 utilses that which is present in various ways. 1. It tends to effect a 

 a regular distribution of the natural manure material of fields, inas- 



